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Sample records for strain rate effects

  1. Strain rate effects in stress corrosion cracking

    SciTech Connect

    Parkins, R.N. . Dept. of Metallurgy and Engineering Materials)

    1990-03-01

    Slow strain rate testing (SSRT) was initially developed as a rapid, ad hoc laboratory method for assessing the propensity for metals an environments to promote stress corrosion cracking. It is now clear, however, that there are good theoretical reasons why strain rate, as opposed to stress per se, will often be the controlling parameter in determining whether or not cracks are nucleated and, if so, are propagated. The synergistic effects of the time dependence of corrosion-related reactions and microplastic strain provide the basis for mechanistic understanding of stress corrosion cracking in high-pressure pipelines and other structures. However, while this may be readily comprehended in the context of laboratory slow strain tests, its extension to service situations may be less apparent. Laboratory work involving realistic stressing conditions, including low-frequency cyclic loading, shows that strain or creep rates give good correlation with thresholds for cracking and with crack growth kinetics.

  2. Strain rate effects for spallation of concrete

    NASA Astrophysics Data System (ADS)

    Häussler-Combe, Ulrich; Panteki, Evmorfia; Kühn, Tino

    2015-09-01

    Appropriate triaxial constitutive laws are the key for a realistic simulation of high speed dynamics of concrete. The strain rate effect is still an open issue within this context. In particular the question whether it is a material property - which can be covered by rate dependent stress strain relations - or mainly an effect of inertia is still under discussion. Experimental and theoretical investigations of spallation of concrete specimen in a Hopkinson Bar setup may bring some evidence into this question. For this purpose the paper describes the VERD model, a newly developed constitutive law for concrete based on a damage approach with included strain rate effects [1]. In contrast to other approaches the dynamic strength increase is not directly coupled to strain rate values but related to physical mechanisms like the retarded movement of water in capillary systems and delayed microcracking. The constitutive law is fully triaxial and implemented into explicit finite element codes for the investigation of a wide range of concrete structures exposed to impact and explosions. The current setup models spallation experiments with concrete specimen [2]. The results of such experiments are mainly related to the dynamic tensile strength and the crack energy of concrete which may be derived from, e.g., the velocity of spalled concrete fragments. The experimental results are compared to the VERD model and two further constitutive laws implemented in LS-Dyna. The results indicate that both viscosity and retarded damage are required for a realistic description of the material behaviour of concrete exposed to high strain effects [3].

  3. Effect of Strain Rate on Ductile Fracture

    DTIC Science & Technology

    2006-01-01

    follows: The effect of strain rate on ductile fracture is one of the least understood phenomena in modern fracture mechanics. At the same time...into three interrelated tasks: Hopkinson bar tensile fracture tests on small, flat specimens using a unique apparatus developed at IPPT; Drop tower...between IPPT and MIT where the funding for the work at MIT will come from GE Global Research Center and the funding for the IPPT will come from this

  4. High Strain Rate Tensile and Compressive Effects in Glassy Polymers

    DTIC Science & Technology

    2013-02-08

    polymers under high strain rates has been determined in compression. Some research programs have studied the combined effects of temperature and strain rate...glassy polymers to high strain rate loading in compression. More recently, research programs that study the combined effects of temperature and strain...Force Materiel Command  United States Air Force  Eglin Air Force Base AFRL-RW-EG-TP-2013-006 High Strain Rate

  5. Strain Rate Effects on Ultimate Strain of Copper

    DTIC Science & Technology

    1979-05-01

    34Dogbone" Specimen Used for Quasi-Static 5 and Intermediate Rate Tests 2 Schematic of Split Hopkinso’v Bar Apparatus 7 3a PETN Filled Tube Specimen...48 Experiment 25 Calculated Stress Components in Copper Cylinder 52 Expanded by PETN 26 Fracture of Explosively Expanded Cylindrical 54 Tube A-la...Record of Shot No. 10 73 A7b Framing Camera Record of Shot No. 10 74 A-8 Strain Versus Time for Copper Tube Expanded 75 by PETN vi

  6. Effects of Applied Strain on Rates of Ageing: Project Overview

    NASA Technical Reports Server (NTRS)

    Campion, R. P.

    1997-01-01

    One of the stated intents of this project has been to make some assessment of effects of strain on rates of ageing of project thermoplastics exposed to project fluids. To this end, certain straining jigs which apply in various modes - tensile, four-point bending and crack growth using compact tension samples - were designed and made for holding samples during fluid exposures. During testing, features of the thermoplastics have been observed which have tended to confuse apparent strain effects on the polymers' aged performance, but recent assessments of the topic and its data have led to considerable progress being made in identifying test procedures necessary for strain and related effects on chemical deterioration to manifest themselves. It is the intent of this report to provide a summary of what has been determined on strain and related effects thus far, and provide recommendations for clarifying them in Phase 2 by means of further test procedures which will increase and focus the severity of the conditions applying. The choice of flexible pipe rather than umbilicals service for assessing service strain conditions reflects the major interest of project members. However, Tefzel data are still provided.

  7. Effect of strain and strain rate on residual microstructures in copper

    SciTech Connect

    Stevens, M.F.; Follansbee, P.S.

    1986-01-01

    Several specimens of OFE Cu were deformed in compression to study the resulting microstructures at equivalent levels of threshold stress and strain. Equiaxed, diffuse dislocation cells are more persistent in Cu when tested at strain rates exceeding 10/sup 3/ sec/sup -1/. At quasi-static strain rates, dislocation collapse into more distinct, narrow microbands occurs at lower strain levels.

  8. Shock Compression and Strain Rate Effect in Composites and Polymers

    SciTech Connect

    Brown, Eric

    2012-06-20

    Polymers are increasingly being utilized as monolithic materials and composite matrices for structural applications historically reserved for metals. High strain and high strain-rate applications in aerospace, defense, and automotive industries have lead to interest in utilizing the ability of many polymers to withstand extensions to failure of several hundred percent, often without localization or necking and their strong rate dependence. A broad range of characterization techniques will be presented for semi-crystalline polymers and composites including elastic-plastic fracture, split Hopkinson pressure bar (SHPB), plate impact including soft-recovery and lateral gage measurements and Taylor Impact. Gas-launched, plate impact experiments have been performed on pedigreed PTFE 7C, mounted in momentum-trapped, shock assemblies, with impact pressures above and below the phase II to phase III crystalline transition to probe subtle changes in the crystallinity, microstructure, and mechanical response of PTFE. Observed strong anisotropy on the hugoniot and spall behavior of fiber-reinforced composites will be discussed. Polymers are known to exhibit a strong dependence of the yield stress on temperature and strain-rate that are often observed to be linear for temperature and logarithmic for strain-rate. Temperature and strain-rate dependence will be reviewed in terms of classic time-temperature superposition and an empirical mapping function for superposition between temperature and strain-rate. The recent extension of the new Dynamic-Tensile-Extrusion (Dyn-Ten-Ext) technique to probe the dynamic tensile responses of polymers will be discussed, where more irregular deformation and stochastic-based damage and failure mechanisms than the stable plastic elongation and shear instabilities observed that in metals. The opportunity to use of Dyn-Ten-Ext to probe incipient damage at very high strain-rate by linking in situ and post mortem experimental observations with high

  9. Effect of Strain Rate on Mechanical Properties of Wrought Sintered Tungsten at Temperatures above 2500 F

    NASA Technical Reports Server (NTRS)

    Sikora, Paul F.; Hall, Robert W.

    1961-01-01

    Specimens of wrought sintered commercially pure tungsten were made from 1/8-inch swaged rods. All the specimens were recrystallized at 4050 F for 1 hour prior to testing at temperatures from 2500 to 4000 F at various strain rates from 0.002 to 20 inches per inch per minute. Results showed that, at a constant temperature, increasing the strain rate increased the ultimate tensile strength significantly. The effects of both strain rate and temperature on the ultimate tensile strength of tungsten may be correlated by the linear parameter method of Manson and Haferd and may be used to predict the ultimate tensile strength at higher temperatures, 4500 and 5000 F. As previously reported, ductility, as measured by reduction of area in a tensile test, decreases with increasing temperature above about 3000 F. Increasing the strain rate at temperatures above 3000 F increases the ductility. Fractures are generally transgranular at the higher strain rates and intergranular at the lower strain rates.

  10. Analysis of the tensile stress-strain behavior of elastomers at constant strain rates. I - Criteria for separability of the time and strain effects

    NASA Technical Reports Server (NTRS)

    Hong, S. D.; Fedors, R. F.; Schwarzl, F.; Moacanin, J.; Landel, R. F.

    1981-01-01

    A theoretical analysis of the tensile stress-strain relation of elastomers at constant strain rate is presented which shows that the time and the stress effect are separable if the experimental time scale coincides with a segment of the relaxation modulus that can be described by a single power law. It is also shown that time-strain separability is valid if the strain function is linearly proportional to the Cauchy strain, and that when time-strain separability holds, two strain-dependent quantities can be obtained experimentally. In the case where time and strain effect are not separable, superposition can be achieved only by using temperature and strain-dependent shift factors.

  11. Biaxial load effects on the crack border elastic strain energy and strain energy rate

    NASA Technical Reports Server (NTRS)

    Eftis, J.; Subramonian, N.; Liebowitz, H.

    1977-01-01

    The validity of the singular solution (first term of a series representation) is investigated for the crack tip stress and displacement field in an infinite sheet with a flat line crack with biaxial loads applied to the outer boundaries. It is shown that if one retains the second contribution to the series approximations for stress and displacement in the calculation of the local elastic strain energy density and elastic strain energy rate in the crack border region, both these quantities have significant biaxial load dependency. The value of the J-integral does not depend on the presence of the second term of the series expansion for stress and displacement. Thus J(I) is insensitive to the presence of loads applied parallel to the plane of the crack.

  12. Temperature and Strain-Rate Effects on Low-Cycle Fatigue Behavior of Alloy 800H

    NASA Technical Reports Server (NTRS)

    Rao, K. Bhanu Sankara; Schiffers, H.; Schuster, H.; Halford, G. R.

    1996-01-01

    The effects of strain rate (4 x 10(exp -6) to 4 x 10(exp -3)/s) and temperature on the Low-Cycle Fatigue (LCF) behavior of alloy 800H have been evaluated in the range 750 C to 950 C. Total axial strain controlled LCF tests were conducted in air at a strain amplitude of +/- 0.30 pct. LCF life decreased with decreasing strain rate and increasing temperature. The cyclic stress response behavior showed a marked variation with temperature and strain rate. The time- and temperature- dependent processes which influence the cyclic stress response and life have been identified and their relative importance assessed. Dynamic strain aging, time-dependent deformation, precipitation of parallel platelets of M(23)C6 on grain boundaries and incoherent ledges of twins, and oxidation were found to operate depending on the test conditions. The largest effect on life was shown by oxidation processes.

  13. The effect of strain rate on fracture toughness of human cortical bone: a finite element study.

    PubMed

    Ural, Ani; Zioupos, Peter; Buchanan, Drew; Vashishth, Deepak

    2011-10-01

    Evaluating the mechanical response of bone under high loading rates is crucial to understanding fractures in traumatic accidents or falls. In the current study, a computational approach based on cohesive finite element modeling was employed to evaluate the effect of strain rate on fracture toughness of human cortical bone. Two-dimensional compact tension specimen models were simulated to evaluate the change in initiation and propagation fracture toughness with increasing strain rate (range: 0.08-18 s(-1)). In addition, the effect of porosity in combination with strain rate was assessed using three-dimensional models of micro-computed tomography-based compact tension specimens. The simulation results showed that bone's resistance against the propagation of a crack decreased sharply with increase in strain rates up to 1 s(-1) and attained an almost constant value for strain rates larger than 1 s(-1). On the other hand, initiation fracture toughness exhibited a more gradual decrease throughout the strain rates. There was a significant positive correlation between the experimentally measured number of microcracks and the fracture toughness found in the simulations. Furthermore, the simulation results showed that the amount of porosity did not affect the way initiation fracture toughness decreased with increasing strain rates, whereas it exacerbated the same strain rate effect when propagation fracture toughness was considered. These results suggest that strain rates associated with falls lead to a dramatic reduction in bone's resistance against crack propagation. The compromised fracture resistance of bone at loads exceeding normal activities indicates a sharp reduction and/or absence of toughening mechanisms in bone during high strain conditions associated with traumatic fracture.

  14. THE EFFECT OF STRAIN RATE ON FRACTURE TOUGHNESS OF HUMAN CORTICAL BONE: A FINITE ELEMENT STUDY

    PubMed Central

    Ural, Ani; Zioupos, Peter; Buchanan, Drew; Vashishth, Deepak

    2011-01-01

    Evaluating the mechanical response of bone under high loading rates is crucial to understanding fractures in traumatic accidents or falls. In the current study, a computational approach based on cohesive finite element modeling was employed to evaluate the effect of strain rate on fracture toughness of human cortical bone. Two-dimensional compact tension specimen models were simulated to evaluate the change in initiation and propagation fracture toughness with increasing strain rate (range: 0.08 to 18 s−1). In addition, the effect of porosity in combination with strain rate was assessed using three-dimensional models of microcomputed tomography-based compact tension specimens. The simulation results showed that bone’s resistance against the propagation of fracture decreased sharply with increase in strain rates up to 1 s−1 and attained an almost constant value for strain rates larger than 1 s−1. On the other hand, initiation fracture toughness exhibited a more gradual decrease throughout the strain rates. There was a significant positive correlation between the experimentally measured number of microcracks and the fracture toughness found in the simulations. Furthermore, the simulation results showed that the amount of porosity did not affect the way initiation fracture toughness decreased with increasing strain rates, whereas it exacerbated the same strain rate effect when propagation fracture toughness was considered. These results suggest that strain rates associated with falls lead to a dramatic reduction in bone’s resistance against crack propagation. The compromised fracture resistance of bone at loads exceeding normal activities indicates a sharp reduction and/or absence of toughening mechanisms in bone during high strain conditions associated with traumatic fracture. PMID:21783112

  15. TRIP effect in austenitic-martensitic VNS9-Sh steel at various strain rates

    NASA Astrophysics Data System (ADS)

    Terent'ev, V. F.; Slizov, A. K.; Prosvirnin, D. V.

    2016-10-01

    The mechanical properties of austenitic-martensitic VNS9-Sh (23Kh15N5AM3-Sh) steel are studied at a static strain rate from 4.1 × 10-5 to 17 × 10-3 s-1 (0.05-20 mm/min). It is found that, as the strain rate increases, the ultimate tensile strength decreases and the physical yield strength remains unchanged (≈1400 MPa). As the strain rate increases, the yield plateau remains almost unchanged and the relative elongation decreases continuously. Because of high microplastic deformation, the conventional yield strength is lower than the physical yield strength over the entire strain rate range under study. The influence of the TRIP effect on the changes in the mechanical properties of VNS9-Sh steel at various strain rates is discussed.

  16. The effect of an acute bout of resistance exercise on carotid artery strain and strain rate.

    PubMed

    Black, Jane M; Stöhr, Eric J; Stone, Keeron; Pugh, Christopher J A; Stembridge, Mike; Shave, Rob; Esformes, Joseph I

    2016-09-01

    Arterial wall mechanics likely play an integral role in arterial responses to acute physiological stress. Therefore, this study aimed to determine the impact of low and moderate intensity double-leg press exercise on common carotid artery (CCA) wall mechanics using 2D vascular strain imaging. Short-axis CCA ultrasound images were collected in 15 healthy men (age: 21 ± 3 years; stature: 176.5 ± 6.2 cm; body mass; 80.6 ± 15.3 kg) before, during, and immediately after short-duration isometric double-leg press exercise at 30% and 60% of participants' one-repetition maximum (1RM: 317 ± 72 kg). Images were analyzed for peak circumferential strain (PCS), peak systolic and diastolic strain rate (S-SR and D-SR), and arterial diameter. Heart rate (HR), systolic and diastolic blood pressure (SBP and DBP) were simultaneously assessed and arterial stiffness indices were calculated post hoc. A two-way repeated measures ANOVA revealed that during isometric contraction, PCS and S-SR decreased significantly (P < 0.01) before increasing significantly above resting levels post exercise (P < 0.05 and P < 0.01, respectively). Conversely, D-SR was unaltered throughout the protocol (P = 0.25). No significant differences were observed between the 30% and 60% 1RM trials. Multiple regression analysis highlighted that HR, BP, and arterial diameter did not fully explain the total variance in PCS, S-SR, and D-SR Acute double-leg press exercise is therefore associated with similar transient changes in CCA wall mechanics at low and moderate intensities. CCA wall mechanics likely provide additional insight into localized intrinsic vascular wall properties beyond current measures of arterial stiffness.

  17. Effects of Strain Rates on Mechanical Properties and Fracture Mechanism of DP780 Dual Phase Steel

    NASA Astrophysics Data System (ADS)

    Li, Shengci; Kang, Yonglin; Zhu, Guoming; Kuang, Shuang

    2015-06-01

    The mechanical properties of DP780 dual phase steel were measured by quasi-static and high-speed tensile tests at strain rates between 0.001 and 1000 s-1 at room temperature. The deformation and fracture mechanisms were analyzed by observation of the tensile fracture and microstructure near the fracture. Dynamic factor and feret ratio quantitative methods were applied to study the effect of strain rate on the microstructure and properties of DP780 steel. The constitutive relation was described by a modified Johnson-Cook and Zerilli-Armstrong model. The results showed that the strain rate sensitivity of yield strength is bigger than that of ultimate tensile strength; as strain rate increased, the formation of microcracks and voids at the ferrite/martensite interface can be alleviated; the strain rate effect is unevenly distributed in the plastic deformation region. Moreover, both models can effectively describe the experimental results, while the modified Zerilli-Armstrong model is more accurate because the strain-hardening rate of this model is independent of strain rate.

  18. Effects of temperature and strain rate on the mechanical properties of hexagonal boron nitride nanosheets

    NASA Astrophysics Data System (ADS)

    Han, Tongwei; Luo, Ying; Wang, Chengyuan

    2014-01-01

    The effect of temperature and strain rate on mechanical properties remains an open topic in research of hexagonal boron nitride (h-BN) nanosheets. To examine these fundamental issues we have performed molecular dynamics simulations to record the stress-strain curves in tensile tests and measure Young's modulus, fracture strength and fracture strain in armchair and zigzag directions. Comparing the results obtained at different temperatures and strain rates we have quantified the effects of the two factors on the tensile properties of the h-BN nanosheets. The influence of crystal orientation is also examined in the present study. It is found that the h-BN nanosheets are basically an anisotropic material whose tensile properties vary substantially with temperature and strain rate. In particular, a yielding platform is observed for the h-BN nanomaterial at relatively low temperature.

  19. The effect analysis of strain rate on power transmission tower-line system under seismic excitation.

    PubMed

    Tian, Li; Wang, Wenming; Qian, Hui

    2014-01-01

    The effect analysis of strain rate on power transmission tower-line system under seismic excitation is studied in this paper. A three-dimensional finite element model of a transmission tower-line system is created based on a real project. Using theoretical analysis and numerical simulation, incremental dynamic analysis of the power transmission tower-line system is conducted to investigate the effect of strain rate on the nonlinear responses of the transmission tower and line. The results show that the effect of strain rate on the transmission tower generally decreases the maximum top displacements, but it would increase the maximum base shear forces, and thus it is necessary to consider the effect of strain rate on the seismic analysis of the transmission tower. The effect of strain rate could be ignored for the seismic analysis of the conductors and ground lines, but the responses of the ground lines considering strain rate effect are larger than those of the conductors. The results could provide a reference for the seismic design of the transmission tower-line system.

  20. The Effect Analysis of Strain Rate on Power Transmission Tower-Line System under Seismic Excitation

    PubMed Central

    Wang, Wenming

    2014-01-01

    The effect analysis of strain rate on power transmission tower-line system under seismic excitation is studied in this paper. A three-dimensional finite element model of a transmission tower-line system is created based on a real project. Using theoretical analysis and numerical simulation, incremental dynamic analysis of the power transmission tower-line system is conducted to investigate the effect of strain rate on the nonlinear responses of the transmission tower and line. The results show that the effect of strain rate on the transmission tower generally decreases the maximum top displacements, but it would increase the maximum base shear forces, and thus it is necessary to consider the effect of strain rate on the seismic analysis of the transmission tower. The effect of strain rate could be ignored for the seismic analysis of the conductors and ground lines, but the responses of the ground lines considering strain rate effect are larger than those of the conductors. The results could provide a reference for the seismic design of the transmission tower-line system. PMID:25105157

  1. Molecular dynamics simulation of a solid platinum nanowire under uniaxial tensile strain: Temperature and strain-rate effects

    NASA Astrophysics Data System (ADS)

    Koh, S. J. A.; Lee, H. P.; Lu, C.; Cheng, Q. H.

    2005-08-01

    Nanoscale research has been an area of active research over the past fifteen years. This is due to the overall enhanced properties of nanomaterials due to size effects, surface effects, and interface effects, which typically showed up in materials with characteristic size smaller than 100nm . This study focuses on the molecular dynamics (MD) simulation of an infinitely long, cylindrical platinum nanowire, with an approximate diameter of 1.4nm . The nanowire was subjected to uniaxial tensile strain along the [001] axis. The changes in crystal structure during deformation were analyzed and its mechanical properties were deduced from the simulation. Classical MD simulation was employed in this study, with the empirical Sutton-Chen pair functional used to describe the interatomic potential between the platinum atoms. The Berendsen loose-coupling thermostat was selected for finite-temperature control of the simulated system, with a time constant of 25% of the total relaxation time during each strain increment. The nanowire was subjected to strain rates of 0.04%, 0.4%, and 4.0%ps-1 , at simulation temperatures of 50 and 300K , in order to study the effects of different strain rates and thermal conditions on the deformation characteristics and mechanical properties of the nanowire. It was found that the stress-strain response of the nanowire showed clear periodic, stepwise dislocation-relaxation-recrystallization behavior at low temperature and strain rate, where crystal order and stability were highly preserved. The onset of amorphous crystal deformation occurred at 0.4%ps-1 , and fully amorphous deformation took place at 4.0%ps-1 , with amorphous melting detected at 300K . Due to higher entropy of the nanowire at higher temperature and strain rate, periodic stress-strain behavior became less clearly defined, and superplasticity behavior was observed. This characteristic was significantly enhanced due to the development of a single-walled helical substructure at 300K

  2. Effect of temperature and strain rate on cavitation in a superplastic duplex stainless steel

    SciTech Connect

    Pulino-Sagradi, D.; Nazar, A.M.M.; Ammann, J.J.; Medrano, R.E.

    1997-11-01

    The effect of temperature and strain rate on cavitation during superplastic deformation of a duplex stainless steel has been studied at 1,223 K and 1,253 K for initial strain rates ranging from 2 {times} 10{sup {minus}4} s{sup {minus}1} to 2 {times} 10{sup {minus}3} s{sup {minus}1}. The cavitation was analyzed quantitatively for a specifically developed image processing technique that allows an accurate determination of the volume fraction and size distribution of the voids. The results show that increasing temperature and/or decreasing strain rate cause a more homogeneous deformation of the specimen characterized by a uniform size and distribution of the cavities. The increase of the strain rate results in an increase in cavity volume fraction related to more cavity nucleation and interlinkage. This reflects the lack of accommodation process during the mechanism of grain boundary sliding.

  3. Effects of strain rate on the mechanical properties of tricalcium phosphate/poly(L: -lactide) composites.

    PubMed

    Yamadi, Shusaku; Kobayashi, Satoshi

    2009-01-01

    Bioactive ceramic/bioresorbable plastic composites have been expected as materials for the bone fracture fixations which have more biocompatibility than monolithic bioresorbable plastics. Many studies have been conducted on these materials. Most studies, however, focused on the mechanical properties under static loading. In the actual usage, these materials are loaded dynamically. In this study, effects of strain rate on the mechanical properties of tricalcium phosphate/poly(L: -lactide) (TCP/PLLA) composites were investigated experimentally and analytically. The TCP/PLLA composites containing three different TCP contents (5, 10 and 15 wt.%) were prepared by injection molding. In order to characterize the mechanical properties, tensile and compressive tests were conducted. The results of tensile tests indicated that the Young's moduli of composites increased with increasing TCP contents. For each TCP contents, tensile Young's modulus kept constant up to strain rate of 10(-1)/s. On the other hand, tensile strength increased with increasing strain rate. The effect of strain rate became larger with decreasing TCP contents, which means the strain rate dependency of the PLLA is more effective than that of TCP. From the results of compressive tests, similar results with tensile tests were obtained. That is, compressive Young's modulus kept constant up to strain rate of 10(-1)/s and the 0.2% proof stress increased with increasing strain rate. In order to predict the mechanical behavior of TCP/PLLA composites, the micro-damage mechanics was proposed. In this analysis, 3-phases particle reinforced composites, which include the intact particles, damaged particles and matrix, are assumed. The elastic constants are calculated with micromechanics based on the analyses by Eshelby and Mori and Tanaka. Only the debonding between particle and matrix are assumed as the damage. The nonlinearity in the stress-strain behavior of matrix PLLA is also considered. The debonding particles

  4. Numerical study of strain-rate effect in cold rolls forming of steel

    NASA Astrophysics Data System (ADS)

    Falsafi, J.; Demirci, E.; Silberschmidt, V. V.

    2013-07-01

    Cold roll forming (CRF) is a well-known continuous manufacturing process, in which a flat strip is deformed by successive rotating pairs of tools, without changing the material thickness. In the past decades, to lessen the process-development efforts, finite-element simulations have been increasingly employed to improve the process design and predict the manufacturing-induced defects. One of the important aspects in design of the CRF process is consideration of resulting strains in the final product as the material passes through several complex forming stands. Sufficient knowledge of longitudinal strain in the workpiece is required to set various process parameters. Increasing a process speed in a roll forming operation can bring cost advantages, but the influence of the forming speed on the strain distribution should be explored. This study is focussed on a strain-rate effect in the CRF process of steel sheets. The strain-rate dependency of a plastic behaviour observed in most metals can affect the finished product's quality as well as process parameters. This paper investigates the influence of the strain rate on longitudinal strains induced in the roll forming operation by incorporating a phenomenological Johnson-Cook constitutive model, which allows studying the impact of the process speed on the output product. Taking advantage of 3D finite element analysis, a roll forming process was simulated using MCS.Marc, comprising a complete set of forming stations. Through the changing of the process speed, the strain rate impact on longitudinal peak strains and forming length was investigated. The results highlight the effect of the strain rate on edge thinning and subsequent undesirable distortions in the product.

  5. Compressive behavior of bulk metallic glass under different conditions --- Coupled effect of temperature and strain rate

    NASA Astrophysics Data System (ADS)

    Yin, Weihua

    Metallic glass was first reported in 1960 by rapid quenching of Au-Si alloys. But, due to the size limitation, this material did not attract remarkable interest until the development of bulk metallic glasses (BMGs) with specimen sizes in excess of 1 mm. BMGs are considered to be promising engineering materials because of their ultrahigh strength, high elastic limit and wear resistance. However, they usually suer from a strong tendency for localized plastic deformation with catastrophic failure. Many basic questions, such as the origin of shear softening and the strain rate eect remain unclear. In this thesis, the mechanical behavior of the Zr55Al 10Ni5Cu30 bulk metallic glass and a metallic glass composite is investigated. The stress-strain relationship for Zr55Al10Ni 5Cu30 over a wide range of strain rate (5x10 --5 to 2x103 s--1) was investigated in uniaxial compression loading using both MTS servo-hydraulic system (quasi-static) and compression Kolsky bar system (dynamic). The effect of the strain rate on the fracture stress at room temperature was discussed. Based on the experimental results, the strain rate sensitivity of the bulk metallic glass changes from a positive value to a negative value at high strain rate, which is a consequence of the significant adiabatic temperature rise during the dynamic testing. In order to characterize the temperature eect on the mechanical behavior of the metallic glass, a synchronically assembled heating unit was designed to be attached onto the Kolsky bar system to perform high temperature and high strain rate mechanical testing. A transition from inhomogeneous deformation to homogeneous deformation has been observed during the quasi-static compressive experiments at testing temperatures close to the glass transition temperature. However, no transition has been observed at high strain rates at all the testing temperatures. A free volume based model is applied to analyze the stress-strain behavior of the homogeneous

  6. Effects of strain rate and surface cracks on the mechanical behaviour of Balmoral Red granite.

    PubMed

    Mardoukhi, Ahmad; Mardoukhi, Yousof; Hokka, Mikko; Kuokkala, Veli-Tapani

    2017-01-28

    This work presents a systematic study on the effects of strain rate and surface cracks on the mechanical properties and behaviour of Balmoral Red granite. The tensile behaviour of the rock was studied at low and high strain rates using Brazilian disc samples. Heat shocks were used to produce samples with different amounts of surface cracks. The surface crack patterns were analysed using optical microscopy, and the complexity of the patterns was quantified by calculating the fractal dimensions of the patterns. The strength of the rock clearly drops as a function of increasing fractal dimensions in the studied strain rate range. However, the dynamic strength of the rock drops significantly faster than the quasi-static strength, and, because of this, also the strain rate sensitivity of the rock decreases with increasing fractal dimensions. This can be explained by the fracture behaviour and fragmentation during the dynamic loading, which is more strongly affected by the heat shock than the fragmentation at low strain rates.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'.

  7. Effects of strain rate and surface cracks on the mechanical behaviour of Balmoral Red granite

    NASA Astrophysics Data System (ADS)

    Mardoukhi, Ahmad; Mardoukhi, Yousof; Hokka, Mikko; Kuokkala, Veli-Tapani

    2017-01-01

    This work presents a systematic study on the effects of strain rate and surface cracks on the mechanical properties and behaviour of Balmoral Red granite. The tensile behaviour of the rock was studied at low and high strain rates using Brazilian disc samples. Heat shocks were used to produce samples with different amounts of surface cracks. The surface crack patterns were analysed using optical microscopy, and the complexity of the patterns was quantified by calculating the fractal dimensions of the patterns. The strength of the rock clearly drops as a function of increasing fractal dimensions in the studied strain rate range. However, the dynamic strength of the rock drops significantly faster than the quasi-static strength, and, because of this, also the strain rate sensitivity of the rock decreases with increasing fractal dimensions. This can be explained by the fracture behaviour and fragmentation during the dynamic loading, which is more strongly affected by the heat shock than the fragmentation at low strain rates. This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'.

  8. Effects of strain rates and temperatures on the mechanical properties of multi-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Chen, X.; Wang, X.; Sheng, G. G.

    2007-04-01

    This paper reports the results of an investigation of the dynamic mechanical properties of multi-walled armchair and zigzag nanotubes under different strain rates and environmental temperatures. Based on a molecular structural mechanics model, the covalent bonds are treated as a two dimensional beam element and van der Waals forces between two adjacent tubes are firstly simulated by a nonlinear spring. The corresponding force constants of bond stretching, bond angle bending and torsional resistance in different environmental temperatures can be, respectively, obtained by computing the variation of chemical bond lengths. The result obtained reveals that the dynamic Young's modulus of the effective nanotube material increases as the strain rate increases, and decreases as the environmental temperature increases; the effect of layer numbers of multi-walled carbon nanotubes (MWCNTs) on the dynamic Young's modulus of the effective nanotube material is dependent on strain rates and environmental temperatures.

  9. Effects of temperature and strain rate on the tensile properties of potassium-doped tungsten

    NASA Astrophysics Data System (ADS)

    Sasaki, Kenta; Yabuuchi, Kiyohiro; Nogami, Shuhei; Hasegawa, Akira

    2015-06-01

    Tensile tests were performed on pure and K-doped tungsten at temperatures from 25 to 700 °C and strain rates between 10-5 and 10-1 s-1 in vacuum. The yield strength of both materials increased with increasing strain rate and decreasing temperature. The amount of change in the yield strength decreased with increasing temperature. The determination of activation volumes for plastic deformation highlighted that the rate-controlling process of the deformation behavior at lower temperatures was the same for both materials, namely, kink-pair formation on screw dislocations, and the process was not affected by potassium addition. The fracture strain of both materials increased with increasing strain rate and decreasing temperature, in the temperature range where the materials showed measurable ductility. K-doped W showed higher yield strength and a lower ductile-to-brittle transition temperature than pure W. No negative effect of K addition on strain rate- and temperature-induced changes in tensile properties was found. The analysis also highlighted the effectiveness of K addition, and of the grain refinement induced by it, for improving the mechanical properties of tungsten.

  10. Effects of temperature and strain rate on the mechanical properties of silicene

    NASA Astrophysics Data System (ADS)

    Pei, Qing-Xiang; Sha, Zhen-Dong; Zhang, Ying-Yan; Zhang, Yong-Wei

    2014-01-01

    Silicene, a graphene-like two-dimensional silicon, has attracted great attention due to its fascinating electronic properties similar to graphene and its compatibility with existing semiconducting technology. So far, the effects of temperature and strain rate on its mechanical properties remain unexplored. We investigate the mechanical properties of silicene under uniaxial tensile deformation by using molecular dynamics simulations. We find that the fracture strength and fracture strain of silicene are much higher than those of bulk silicon, though the Young's modulus of silicene is lower than that of bulk silicon. An increase in temperature decreases the fracture strength and fracture strain of silicene significantly, while an increase in strain rate enhances them slightly. The fracture process of silicene is also studied and brittle fracture behavior is observed in the simulations.

  11. Effects of temperature and strain rate on the mechanical properties of silicene

    SciTech Connect

    Pei, Qing-Xiang Zhang, Yong-Wei; Sha, Zhen-Dong; Zhang, Ying-Yan

    2014-01-14

    Silicene, a graphene-like two-dimensional silicon, has attracted great attention due to its fascinating electronic properties similar to graphene and its compatibility with existing semiconducting technology. So far, the effects of temperature and strain rate on its mechanical properties remain unexplored. We investigate the mechanical properties of silicene under uniaxial tensile deformation by using molecular dynamics simulations. We find that the fracture strength and fracture strain of silicene are much higher than those of bulk silicon, though the Young's modulus of silicene is lower than that of bulk silicon. An increase in temperature decreases the fracture strength and fracture strain of silicene significantly, while an increase in strain rate enhances them slightly. The fracture process of silicene is also studied and brittle fracture behavior is observed in the simulations.

  12. Temperature and strain rate effects in high strength high conductivity copper alloys tested in air

    SciTech Connect

    Edwards, D.J.

    1998-03-01

    The tensile properties of the three candidate alloys GlidCop{trademark} Al25, CuCrZr, and CuNiBe are known to be sensitive to the testing conditions such as strain rate and test temperature. This study was conducted on GlidCop Al25 (2 conditions) and Hycon 3HP (3 conditions) to ascertain the effect of test temperature and strain rate when tested in open air. The results show that the yield strength and elongation of the GlidCop Al25 alloys exhibit a strain rate dependence that increases with temperature. Both the GlidCop and the Hycon 3 HP exhibited an increase in strength as the strain rate increased, but the GlidCop alloys proved to be the most strain rate sensitive. The GlidCop failed in a ductile manner irrespective of the test conditions, however, their strength and uniform elongation decreased with increasing test temperature and the uniform elongation also decreased dramatically at the lower strain rates. The Hycon 3 HP alloys proved to be extremely sensitive to test temperature, rapidly losing their strength and ductility when the temperature increased above 250 C. As the test temperature increased and the strain rate decreased the fracture mode shifted from a ductile transgranular failure to a ductile intergranular failure with very localized ductility. This latter observation is based on the presence of dimples on the grain facets, indicating that some ductile deformation occurred near the grain boundaries. The material failed without any reduction in area at 450 C and 3.9 {times} 10{sup {minus}4} s{sup {minus}1}, and in several cases failed prematurely.

  13. High Strain-Rate and Temperature Effects on the Response of Composites

    NASA Technical Reports Server (NTRS)

    Gilat, Amos

    2004-01-01

    The objective of the research is to expand the experimental study of the effect of strain rate on mechanical response (deformation and failure) of epoxy resins and carbon fibers/epoxy matrix composites, to include elevated temperature tests. The experimental data provide the information needed for NASA scientists for the development of a nonlinear, strain rate and temperature dependent deformation and strength models for composites that can subsequently be used in design. This year effort was directed into the development and testing of the epoxy resin at elevated temperatures. Two types of epoxy resins were tested in shear at high strain rates of about 700 per second and elevated temperatures of 50 and 80 C. The results show that the temperature significantly affects the response of epoxy.

  14. Negative strain rate sensitivity in bulk metallic glass and its similarities with the dynamic strain aging effect during deformation

    SciTech Connect

    Dalla Torre, Florian H.; Dubach, Alban; Siegrist, Marco E.; Loeffler, Joerg F.

    2006-08-28

    Detailed investigations were carried out on the deformation behavior of Zr-based monolithic bulk metallic glass and bulk metallic glass matrix composites. The latter, due to splitting and multiplication of shear bands, exhibits larger compressive strains than the former, without significant loss of strength. Serrated flow in conjunction with a negative strain rate sensitivity was observed in both materials. This observation, together with an increase in stress drops with increasing strain and their decrease with increasing strain rate, indicates phenomenologically close similarities with the dynamic strain aging deformation mechanism known for crystalline solids. The micromechanical mechanism of a shear event is discussed in light of these results.

  15. Effect of temperature and strain rate on the compressive behaviour of supramolecular polyurethane

    NASA Astrophysics Data System (ADS)

    Tang, Xuegang; Siviour, Clive R.; Buckley, C. Paul; Feula, Antonio; Hayes, Wayne

    2015-09-01

    Supramolecular polyurethanes (SPUs) possess thermoresponsive and thermoreversible properties, and those characteristics are highly desirable in both bulk commodity and value-added applications such as adhesives, shape-memory materials, healable coatings and lightweight, impact-resistant structures (e.g. protection for mobile electronics). A better understanding of the mechanical properties, especially the rate and temperature sensitivity, of these materials are required to assess their suitability for different applications. In this paper, a newly developed SPU with tuneable thermal properties was studied, and the response of this SPU to compressive loading over strain rates from 10-3 to 104 s-1 was presented. Furthermore, the effect of temperature on the mechanical response was also demonstrated. The sample was tested using an Instron mechanical testing machine for quasi-static loading, a home-made hydraulic system for moderate rates and a traditional split Hopkinson pressure bars (SHPBs) for high strain rates. Results showed that the compression stress-strain behaviour was affected significantly by the thermoresponsive nature of SPU, but that, as expected for polymeric materials, the general trends of the temperature and the rate dependence mirror each other. However, this behaviour is more complicated than observed for many other polymeric materials, as a result of the richer range of transitions that influence the behaviour over the range of temperatures and strain rates tested.

  16. Strain Rate Effects for Concrete and Fiber Reinforced Concrete Subjected to Impact Loading

    DTIC Science & Technology

    1987-10-01

    S. Mindess and S. P. Shah) MRS Symposia Proceedings, V67. 64, pp. 21-37, 1986. 9. Shah, S. P., "Concrete and Fiber Reinforced Concrete Subjected to...Impact Loading," in Cement Based Composites: Strain Rate Effects on Fracture (eds. S. Mindess and S. P. Shah) MRS Symposia Proceedings, Vol. 64, pp... Mindess (11), Sierakowski (12), aAd Reinhardt (13). Many investigators (see for example Ref. 6) have studied the rate sensitivity of fracture strength

  17. Temperature and strain rate effects on the piezoelectric charge production of PZT 95/5

    NASA Astrophysics Data System (ADS)

    Khan, Amnah S.; Proud, William G.

    2017-01-01

    To develop a better understanding of the piezoelectric ceramic lead zirconate titanate (PZT) 95/5, parameters including varying temperatures, porosities and strain rates have been studied. The effects on the charge output and fracture of poled PZT samples of different porosities have been investigated with compressive strain rates (10-4 - 10+3 s-1) using quasi-static loading equipment, drop-weight towers and Split Hopkinson Pressure Bars (SHPBs). The cylindrical specimens were of 4.4 mm diameter, thickness 0.8 - 4.4 mm, and density 7.3 - 8.3 g cm-3. The temperature range of -20 °C to +80 °C was achieved using purpose-built environmental chambers. The resulting stress-strain relationships are compared; all the samples ultimately displayed a brittle response at failure [1].

  18. Strain rate effects on symmetric diblock copolymer liquid bridges: order-induced stability of polymer fibres.

    PubMed

    Peters, Robert D; Dalnoki-Veress, Kari

    2014-10-01

    Optical microscopy is used to study the effect of lamellar order on the evolution of polymer-melt bridges. Measurements are performed on symmetric diblock copolymers and linear homopolymers in the melt state. Diblock copolymer bridges measured in the disordered phase are shown to exhibit the same strain rate response as their homopolymer counterparts: shear thinning at low strain rates and shear thickening at high strain rates. However, when measured in the ordered phase, copolymer-melt bridges demonstrate an increased effective viscosity due to the lamellar order and a shear thinning response over the entire range of strain rates probed. The increased viscosity demonstrates an enhanced stability in lamellae forming diblock liquid bridges, presumed to be caused by the isotropic orientational order of lamellar domains that provide energy barriers to flow within the bridge. The shear thinning can be understood as an alignment of lamellae along the axis of the bridge due to flow, facilitating unimpeded diffusion of polymer out of the liquid bridge along lamellar boundaries.

  19. Effects of strain rate and confining pressure on the deformation and failure of shale

    SciTech Connect

    Cook, J.M. ); Sheppard, M.C. ); Houwen, O.H. )

    1991-06-01

    Previous work on shale mechanical properties has focused on the slow deformation rates appropriate to wellbore deformation. Deformation of shale under a drill bit occurs at a very high rate, and the failure properties of the rock under these conditions are crucial in determining bit performance and in extracting lithology and pore-pressure information from drilling parameters. Triaxial tests were performed on two nonswelling shales under a wide range of strain rates and confining and pore pressures. At low strain rates, when fluid is relatively free to move within the shale, shale deformation and failure are governed by effective stress or pressure (i.e., total confining pressure minus pore pressure), as is the case for ordinary rock. If the pore pressure in the shale is high, increasing the strain rate beyond about 0.1%/sec causes large increases in the strength and ductility of the shale. Total pressure begins to influence the strength. At high stain rates, the influence of effective pressure decreases, except when it is very low (i.e., when pore pressure is very high); ductility then rises rapidly. This behavior is opposite that expected in ordinary rocks. This paper briefly discusses the reasons for these phenomena and their impact on wellbore and drilling problems.

  20. Molecular dynamics study of size, temperature and strain rate effects on mechanical properties of gold nanofilms

    NASA Astrophysics Data System (ADS)

    Gan, Yong; Chen, J. K.

    2009-05-01

    Temperature and extremely-high strain rate effects on mechanical properties of different-size gold nanofilms are investigated using molecular dynamics simulation. The numerical results clearly show a temperature softening effect on the material strength and Young’s modulus and demonstrate a critical film thickness that characterizes a transition from “smaller is softer” to “smaller is stronger”. It is also found that a higher strain rate yields a higher strength, whereas the modulus is much less sensitive to the loading rate. In addition, the Young’s modulus and strength of nanofilms studied are approximately 50%-60% smaller and 50-90 times higher than those of bulk gold, respectively. This suggests that the use of the mechanical properties of a bulk material in a continuum-based approach might be inadequate for the accurate prediction of the thermomechanical response for gold nanofilms caused by ultrashort-pulsed laser heating.

  1. The effect of strain rate sensitivity on dynamic friction of metals

    SciTech Connect

    Brechet, Y. . Lab. de Thermodynamique et Physico-Chimie Metallurgique); Estrin, Y. . Dept. of Mechanical and Materials Engineering)

    1994-06-01

    A simple model relating the plastic constitutive equation to the static and the dynamic coefficient of friction has been developed. It can describe the time dependent effects in static solid friction, as well as predict some special features of the dynamic friction coefficient which may be of relevance for stick-slip phenomena in solid friction. In particular, the model highlights the effect of the intrinsic material characteristic, viz. the strain rate sensitivity of the flow stress, on the friction properties.

  2. The effect of solute distribution on the strain rate sensitivity of solid solutions

    NASA Astrophysics Data System (ADS)

    Xu, Zhijie

    Several aspects of the physics of the interaction of mobile solute atoms and dislocations in dilute solid solution alloys are studied in this thesis. Solute is added to pure metals in order to improve their strength. Alloying also leads to a number of other effects, some of which are undesirable. For example, it leads to reduced ductility and may cause plastic instabilities. Both of these limit material formability. Here, understanding is added regarding the physical basis of these phenomena. Reduced formability is associated with the occurrence of plastic instabilities which are caused either by low strain hardening or by low (negative) strain rate sensitivity (SRS). The current study is focused on the second effect. The strain rate sensitivity has an instantaneous component (always positive), which is associated with the thermally activated motion of dislocations, and a transient component (which may be either positive or negative), which is associated with the correlated motion of dislocations and solute. Negative SRS results when the transient component is sufficiently negative and is presumably due to clustering of solute at dislocations. The study has a multiscale nature. On the nanoscale, the formation of solute clusters at stationary dislocation cores is studied using Monte Carlo simulations and EAM potentials in an Al-Mg alloy. The size of the thermodynamically stable cluster and the binding energy of the dislocation to its cluster are evaluated as a function of the average solute concentration and temperature. Such data enter all existing constitutive models of DSA. On the mesoscale, we investigate how solute structures (concentration fluctuations) defined on longer length scales affect dislocation motion and hence the strain rate sensitivity of the material. This investigation is performed using 2D dislocation dynamics simulations. On the macroscopic scale, parametric constitutive modeling is used to investigate the effect of mesoscopic solute structures

  3. Temperature effects on high strain rate properties of graphite/epoxy composites

    NASA Technical Reports Server (NTRS)

    Yaniv, G.; Daniel, I. M.; Cokeing, S.; Martinez, G. M.

    1991-01-01

    A unidirectional graphite epoxy material (AS4/3501-6) was characterized at strain rates ranging from 5 x 10(exp 6) s(exp -1) to 5(exp -1), at room temperature and at 128 C. Results are presented in the form of stress-strain curves to failure. The longitudinal properties remain nearly unchanged with strain rate and temperature. The transverse modulus increases with strain rate but decreases with temperature. The transverse strength and transverse ultimate tensile strain have a positive rate sensitivity at low rates, which changes to negative at intermediate rates and returns to positive rate sensitivity at the highest rates tested. A temperature-time equivalence principle was applied and master curves were obtained for the transverse mechanical properties. The in-plane shear modulus and in-plane shear strength have a positive rate sensitivity. The ultimate intralaminar shear strain has a positive rate sensitivity at low rates, which changes to negative at high rates. At the elevated temperature of 128 C, the ultimate shear strain is 25 to 30 percent higher than the room temperature value, but its strain rate dependence is moderate.

  4. Investigation on grain size effect in high strain rate ductility of 1100 pure aluminum

    NASA Astrophysics Data System (ADS)

    Bonora, N.; Bourne, N.; Ruggiero, A.; Iannitti, G.; Testa, G.

    2017-01-01

    The effect of the initial grain size on the material ductility at high strain rates in 1100 pure aluminum was investigated. Dynamic tensile extrusion (DTE) tests, at different impact velocities, were performed. Samples have been annealed at 350°C for different exposure times to induce grain growth. Extruded fragments were soft-recovered and the overall length of the extruded jets was used as a measure of material ductility at high strain rates. Numerical simulation of DTE test at different velocity was performed using the modified Rusinek-Klepaczko constitutive model. Results indicates that, as reported for pure copper, the overall ductility of the aluminum increases when grain size decreases. Numerical simulation results were in quite good agreement with experimental data.

  5. Effect of strain rate on bake hardening response of BH220 steel

    NASA Astrophysics Data System (ADS)

    Das, Anindya; Tarafder, Soumitro; Sivaprasad, S.; Chakrabarti, Debalay

    2015-09-01

    This study aims at understanding the bake hardening ability of ultra low carbon BH220 steel at different strain rates. The as-received material has been pre-strained to four different levels and then deformed in tension under (a) as pre-strained state and (b) after baking at 170 ∘C for 20 minutes, at three different strain rates of 0.001, 0.1 and 100/s. In both the conditions, yield stress increased with pre-strain and strain rate, but bake hardening ability was found to decrease when strain rate was increased. The strain rate sensitivity of the material was also found to decrease with bake hardening. Generation of dislocation forests and their subsequent immobility during baking treatment enables them to act as long range obstacles during further deformation. At higher strain rates, less amount of dislocations are produced which can interact with themselves and produce hardening, because of which bake hardening ability and the strain rate drops. A dislocation based strengthening model, as proposed by Larour et al. 2011 [7], was used to predict the yield stress values obtained at different conditions. The equation produced excellent co-relation with the experimental data.

  6. Environmental and high strain rate effects on composites for engine applications

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Smith, G. T.

    1982-01-01

    The complex environmental and loading conditions experienced by many turbine engine components impose severe durability and damage tolerance requirements for component materials. Programs are being conducted to establish the structural performance of composite materials under anticipated engine operating environments. A description is presented of the results obtained in connection with several of these programs. A comparison of predicted and measured hygrothermal effects is considered along with hygrothermal effects on defect growth, high strain rate effects on composite mechanical properties, dynamic stress intensity factors for composites, and the indentation laws for composite impact analysis.

  7. Moisture, anisotropy, stress state, and strain rate effects on bighorn sheep horn keratin mechanical properties

    DOE PAGES

    Johnson, K. L.; Trim, M. W.; Francis, D. K.; ...

    2016-10-01

    Our paper investigates the effects of moisture, anisotropy, stress state, and strain rate on the mechanical properties of the bighorn sheep (Ovis Canadensis) horn keratin. The horns consist of fibrous keratin tubules extending along the length of the horn and are contained within an amorphous keratin matrix. We tested samples in the rehydrated (35 wt.% water) and ambient dry (10 wt.% water) conditions along the longitudinal and radial directions under tension and compression. Increased moisture content was found to increase ductility and decrease strength, as well as alter the stress state dependent nature of the material. Furthermore, the horn keratinmore » demonstrates a significant strain rate dependence in both tension and compression, and also showed increased energy absorption in the hydrated condition at high strain rates when compared to quasi-static data, with increases of 114% in tension and 192% in compression. Compressive failure occurred by lamellar buckling in the longitudinal orientation followed by shear delamination. Tensile failure in the longitudinal orientation occurred by lamellar delamination combined with tubule pullout and fracture. Finally, the structure-property relationships quantified here for bighorn sheep horn keratin can be used to help validate finite element simulations of ram’s impacting each other as well as being useful for other analysis regarding horn keratin on other animals.« less

  8. Moisture, anisotropy, stress state, and strain rate effects on bighorn sheep horn keratin mechanical properties

    SciTech Connect

    Johnson, K. L.; Trim, M. W.; Francis, D. K.; Whittington, W. R.; Miller, J. A.; Bennett, C. E.; Horstemeyer, M. F.

    2016-10-01

    Our paper investigates the effects of moisture, anisotropy, stress state, and strain rate on the mechanical properties of the bighorn sheep (Ovis Canadensis) horn keratin. The horns consist of fibrous keratin tubules extending along the length of the horn and are contained within an amorphous keratin matrix. We tested samples in the rehydrated (35 wt.% water) and ambient dry (10 wt.% water) conditions along the longitudinal and radial directions under tension and compression. Increased moisture content was found to increase ductility and decrease strength, as well as alter the stress state dependent nature of the material. Furthermore, the horn keratin demonstrates a significant strain rate dependence in both tension and compression, and also showed increased energy absorption in the hydrated condition at high strain rates when compared to quasi-static data, with increases of 114% in tension and 192% in compression. Compressive failure occurred by lamellar buckling in the longitudinal orientation followed by shear delamination. Tensile failure in the longitudinal orientation occurred by lamellar delamination combined with tubule pullout and fracture. Finally, the structure-property relationships quantified here for bighorn sheep horn keratin can be used to help validate finite element simulations of ram’s impacting each other as well as being useful for other analysis regarding horn keratin on other animals.

  9. The Effects of Stress Triaxiality, Temperature and Strain Rate on the Fracture Characteristics of a Nickel-Base Superalloy

    NASA Astrophysics Data System (ADS)

    Wang, Jianjun; Guo, Weiguo; Guo, Jin; Wang, Ziang; Lu, Shengli

    2016-05-01

    In this work, to study the effects of stress triaxiality, temperature, and strain rate on the fracture behaviors of a single-crystal Nickel-base superalloy, a series of experiments over a temperature range of 293 to 1373 K, strain rate range of 0.001 to 4000/s, and stress triaxiality range of -0.6 to 1.1 are conducted. Anomalous peak of stress is noticed in the yield stress versus temperature curves, and strain rate effect on the anomalous peak of yield stress is analyzed. The anomalous peak shifts to higher temperature as the strain rate increases. Then the effects of stress triaxiality, temperature, and strain rate on its fracture behaviors, including strain to fracture, path of crack propagation, and fracture surface, are observed and analyzed. A valley of the fracture strain is formed in the fracture strain versus temperature curve over the selected temperature range. The micrograph of fracture surface is largely dependent on the temperature, stress triaxiality, and strain rate. Finally, the original Johnson-Cook (J-C) fracture criterion cannot describe the effect of stress triaxiality and temperature on the fracture behaviors of single-crystal Nickel-base superalloy. A modified J-C fracture criterion is developed, which takes the anomalous stress triaxiality and temperature effects on the fracture behaviors of single-crystal Nickel-base superalloy into account.

  10. The Effect of Electric Current and Strain Rate on Serrated Flow of Sheet Aluminum Alloy 5754

    NASA Astrophysics Data System (ADS)

    Zhao, Kunmin; Fan, Rong; Wang, Limin

    2016-03-01

    Electrically assisted tensile tests are carried out on sheet aluminum alloy AA5754 at electric current densities ranging from 0 to 30.4 A/mm2 and strain rates ranging from 10-3 to 10-1 s-1. The strain rate sensitivity and the serrated flow behavior are investigated in accordance with dynamic strain aging mechanism. The strain rate sensitivity changes from negative to positive and keeps increasing with current density. The tendency toward serrated flow is characterized by the onset of Portevin-Le Chatelier (PLC) instabilities, which are influenced by strain rate, temperature, and electric current. The evolutions of three types of serrated flow are observed and analyzed with respect to strain rate and current density. The magnitude of serration varies with strain rate and current density. The serrated flow can be suppressed by a high strain rate, a high temperature, or a strong electric current. The threshold values of these parameters are determined and discussed. Conventional oven-heated tensile tests are conducted to distinguish the electroplasticity. The flow stress reduces more in electrically assisted tension compared to oven-heated tension at the same temperature level. The electric current helps suppress the serrated flow at the similar temperature level of oven-heating.

  11. Moisture Effects on the High Strain-Rate Behavior of Sand (Preprint)

    DTIC Science & Technology

    2008-04-01

    o r s o s dtl c εε 2 (6) The striker, incident and transmission bars in Fig. 1 were fabricated of VM C350 maraging steel (HRC = 53) with a yield...strain-rate of 400 s-1. The sand specimen confined in a hardened steel tube, had a dry density of 1.50 g/cm3 with moisture contents varied from 3% to 20... steel tube with steel wafers placed on both sides of the specimen. The primary focus was to evaluate the effects of saturation levels on the material

  12. Effect of strain rate and temperature on the tensile properties of MANET II steel

    SciTech Connect

    Ghoneim, M.M.

    1997-08-01

    MANET II, a modified 12% Cr steel with the German designation DIN 1.4914, is a candidate structural material for the first wall and blanket in fusion reactors. In the present study, the tensile properties of this steel were investigated in the temperature range of 25 to 350 C at strain rates of 5 {times} 10{sup {minus}5}, 1.2 {times} 10{sup {minus}4}, and 1.2 {times} 10{sup {minus}3}s{sup {minus}1}. Both microstructure and fracture surfaces were examined using optical and scanning electron microscopic (SEM) techniques. The results showed that the steel suffers dynamic strain aging, although no serrated flow was observed. Yield strength, ultimate strength, and elongation showed negative strain rate sensitivity. Dynamic strain aging also affected the strain hardening rate. Results are discussed with regard to the chemical composition and fracture surface morphology.

  13. Effects of Recovery Behavior and Strain-Rate Dependence of Stress-Strain Curve on Prediction Accuracy of Thermal Stress Analysis During Casting

    NASA Astrophysics Data System (ADS)

    Motoyama, Yuichi; Shiga, Hidetoshi; Sato, Takeshi; Kambe, Hiroshi; Yoshida, Makoto

    2017-03-01

    Recovery behavior (recovery) and strain-rate dependence of the stress-strain curve (strain-rate dependence) are incorporated into constitutive equations of alloys to predict residual stress and thermal stress during casting. Nevertheless, few studies have systematically investigated the effects of these metallurgical phenomena on the prediction accuracy of thermal stress in a casting. This study compares the thermal stress analysis results with in situ thermal stress measurement results of an Al-Si-Cu specimen during casting. The results underscore the importance for the alloy constitutive equation of incorporating strain-rate dependence to predict thermal stress that develops at high temperatures where the alloy shows strong strain-rate dependence of the stress-strain curve. However, the prediction accuracy of the thermal stress developed at low temperatures did not improve by considering the strain-rate dependence. Incorporating recovery into the constitutive equation improved the accuracy of the simulated thermal stress at low temperatures. Results of comparison implied that the constitutive equation should include strain-rate dependence to simulate defects that develop from thermal stress at high temperatures, such as hot tearing and hot cracking. Recovery should be incorporated into the alloy constitutive equation to predict the casting residual stress and deformation caused by the thermal stress developed mainly in the low temperature range.

  14. Strain Rate and Stress Relaxation Effects on Pressuremeter Testing in Clays

    DTIC Science & Technology

    1992-03-01

    CHARACTERISTICS OF KAOLINITE AND GROUND SILICA 245 APPENDIX E COMPUTER PROGRAMS ....................... 248 0 0 0 0 0 0 0 iv LIST OF TABLES Table Page 3.1 A...Comparison of Three Types of Boundary Conditions in a Multiaxial Cubical Test Apparatus ................... 37 3.2 Properties of the Kaolinite and Kaolin...to 0.01 %/min Versus Strain Rate for Kaolinite Clay ................... 102 4.3 Shear Strength Normalized with Respect to 0.01 %/min Versus Strain Rate

  15. Physically-based strength model of tantalum incorporating effects of temperature, strain rate and pressure

    DOE PAGES

    Lim, Hojun; Battaile, Corbett C.; Brown, Justin L.; ...

    2016-06-14

    In this work, we develop a tantalum strength model that incorporates e ects of temperature, strain rate and pressure. Dislocation kink-pair theory is used to incorporate temperature and strain rate e ects while the pressure dependent yield is obtained through the pressure dependent shear modulus. Material constants used in the model are parameterized from tantalum single crystal tests and polycrystalline ramp compression experiments. It is shown that the proposed strength model agrees well with the temperature and strain rate dependent yield obtained from polycrystalline tantalum experiments. Furthermore, the model accurately reproduces the pressure dependent yield stresses up to 250 GPa.more » The proposed strength model is then used to conduct simulations of a Taylor cylinder impact test and validated with experiments. This approach provides a physically-based multi-scale strength model that is able to predict the plastic deformation of polycrystalline tantalum through a wide range of temperature, strain and pressure regimes.« less

  16. Physically-based strength model of tantalum incorporating effects of temperature, strain rate and pressure

    SciTech Connect

    Lim, Hojun; Battaile, Corbett C.; Brown, Justin L.; Weinberger, Christopher R.

    2016-06-14

    In this work, we develop a tantalum strength model that incorporates e ects of temperature, strain rate and pressure. Dislocation kink-pair theory is used to incorporate temperature and strain rate e ects while the pressure dependent yield is obtained through the pressure dependent shear modulus. Material constants used in the model are parameterized from tantalum single crystal tests and polycrystalline ramp compression experiments. It is shown that the proposed strength model agrees well with the temperature and strain rate dependent yield obtained from polycrystalline tantalum experiments. Furthermore, the model accurately reproduces the pressure dependent yield stresses up to 250 GPa. The proposed strength model is then used to conduct simulations of a Taylor cylinder impact test and validated with experiments. This approach provides a physically-based multi-scale strength model that is able to predict the plastic deformation of polycrystalline tantalum through a wide range of temperature, strain and pressure regimes.

  17. Effects of strain rate, mixing ratio, and stress-strain definition on the mechanical behavior of the polydimethylsiloxane (PDMS) material as related to its biological applications.

    PubMed

    Khanafer, Khalil; Duprey, Ambroise; Schlicht, Marty; Berguer, Ramon

    2009-04-01

    Tensile tests on Polydimethylsiloxane (PDMS) materials were conducted to illustrate the effects of mixing ratio, definition of the stress-strain curve, and the strain rate on the elastic modulus and stress-strain curve. PDMS specimens were prepared according to the ASTM standards for elastic materials. Our results indicate that the physiological elastic modulus depends strongly on the definition of the stress-strain curve, mixing ratio, and the strain rate. For various mixing ratios and strain rates, true stress-strain definition results in higher stress and elastic modulus compared with engineering stress-strain and true stress-engineering strain definitions. The elastic modulus increases as the mixing ratio increases up-to 9:1 ratio after which the elastic modulus begins to decrease even as the mixing ratio continues to increase. The results presented in this study will be helpful to assist the design of in vitro experiments to mimic blood flow in arteries and to understand the complex interaction between blood flow and the walls of arteries using PDMS elastomer.

  18. Effect of strain rate on the tensile material properties of human placenta.

    PubMed

    Manoogian, Sarah J; Bisplinghoff, Jill A; McNally, Craig; Kemper, Andrew R; Santago, Anthony C; Duma, Stefan M

    2009-09-01

    Automobile crashes are the largest cause of injury death for pregnant females and the leading cause of traumatic fetal injury mortality in the United States. Computational models, useful tools to evaluate the risk of fetal loss in motor vehicle crashes, are based on a limited number of quasistatic material tests of the placenta. This study presents a total of 64 uniaxial tensile tests on coupon specimens from six human placentas at three strain rates. Material properties of the placental tissue were evaluated at strain rates of 0.07/s, 0.70/s, and 7.00/s. The test data have average failure strains of 0.34, 0.36, and 0.37, respectively. Failure stresses of 10.8 kPa, 11.4 kPa, and 18.6 kPa correspond to an increase in strain rate from 0.07/s to 7.0/s. The results indicate rate dependence only when comparing the highest strain rate of 7.0/s to either of the lower rates. There is no significant rate dependence between 0.07/s and 0.70/s. When compared with previous testing of placental tissue, the current study addresses the material response to more strain rates as well as provides a much larger set of available data. In summary, tensile material properties for the placenta have been determined for use in computational modeling of pregnant occupant kinematics in events ranging from low impact activities to severe impacts such as in motor vehicle crashes.

  19. Effects of strain rate, test temperature and test environment on tensile properties of vandium alloys

    SciTech Connect

    Gubbi, A.N.; Rowcliffe, A.F.; Eatherly, W.S.; Gibson, L.T.

    1996-10-01

    Tensile testing was carried out on SS-3 tensile specimens punched from 0.762-mm-thick sheets of the large heat of V-4Cr-4Ti and small heats of V-3Cr-3Ti and V-6Cr-6Ti. The tensile specimens were annealed at 1000{degrees} for 2 h to obtain a fully recrystallized, fine grain microstructure with a grain size in the range of 10-19 {mu}m. Room temperature tests at strain rates ranging from 10{sup {minus}3} to 5 x 10{sup {minus}1}/s were carried out in air; elevated temperature testing up to 700{degrees}C was conducted in a vacuum better than 1 x 10{sup {minus}5} torr (<10{sup {minus}3} Pa). To study the effect of atomic hydrogen on ductility, tensile tests were conducted at room temperature in an ultra high vacuum chamber (UHV) with a hydrogen leak system.

  20. A Study of Strain Rate Effects for Turbulent Premixed Flames with Application to LES of a Gas Turbine Combustor Model

    SciTech Connect

    Kemenov, Konstantin A.; Calhoon, William H.

    2015-03-24

    Large-scale strain rate field, a resolved quantity which is easily computable in large-eddy simulations (LES), could have profound effects on the premixed flame properties by altering the turbulent flame speed and inducing local extinction. The role of the resolved strain rate has been investigated in a posterior LES study of GE lean premixed dry low NOx emissions LM6000 gas turbine combustor model. A novel approach which is based on the coupling of the lineareddy model with a one-dimensional counter-flow solver has been applied to obtain the parameterizations of the resolved premixed flame properties in terms of the reactive progress variable, the local strain rate measure, and local Reynolds and Karlovitz numbers. The strain rate effects have been analyzed by comparing LES statistics for several models of the turbulent flame speed, i.e, with and without accounting for the local strain rate effects, with available experimental data. The sensitivity of the simulation results to the inflow velocity conditions as well as the grid resolution have been also studied. Overall, the results suggest the necessity to represent the strain rate effects accurately in order to improve LES modeling of the turbulent flame speed.

  1. A Study of Strain Rate Effects for Turbulent Premixed Flames with Application to LES of a Gas Turbine Combustor Model

    DOE PAGES

    Kemenov, Konstantin A.; Calhoon, William H.

    2015-03-24

    Large-scale strain rate field, a resolved quantity which is easily computable in large-eddy simulations (LES), could have profound effects on the premixed flame properties by altering the turbulent flame speed and inducing local extinction. The role of the resolved strain rate has been investigated in a posterior LES study of GE lean premixed dry low NOx emissions LM6000 gas turbine combustor model. A novel approach which is based on the coupling of the lineareddy model with a one-dimensional counter-flow solver has been applied to obtain the parameterizations of the resolved premixed flame properties in terms of the reactive progress variable,more » the local strain rate measure, and local Reynolds and Karlovitz numbers. The strain rate effects have been analyzed by comparing LES statistics for several models of the turbulent flame speed, i.e, with and without accounting for the local strain rate effects, with available experimental data. The sensitivity of the simulation results to the inflow velocity conditions as well as the grid resolution have been also studied. Overall, the results suggest the necessity to represent the strain rate effects accurately in order to improve LES modeling of the turbulent flame speed.« less

  2. Effect of Strain Rate on Tensile Properties of Carbon Fiber Epoxy-Impregnated Bundle Composite

    NASA Astrophysics Data System (ADS)

    Naito, Kimiyoshi

    2014-03-01

    The tensile tests for high tensile strength polyacrylonitrile (PAN)-based (T1000GB) carbon fiber epoxy-impregnated bundle composite at various strain rates ranging from 3.33 × 10-5 to 6.0 × 102 s-1 (various crosshead speeds ranging from 8.33 × 10-7 to 1.5 × 101 m/s) were investigated. The statistical distributions of the tensile strength were also evaluated. The results clearly demonstrated that the tensile strength of bundle composite slightly increased with an increase in the strain rate (crosshead speed) and the Weibull modulus of tensile strength for the bundle composite decreased with an increase in the strain rate (crosshead speed), there is a linear relation between the Weibull modulus and the average tensile strength on log-log scale.

  3. Strain rate effects on mechanical properties in tension of aluminium alloys used in armour applications

    NASA Astrophysics Data System (ADS)

    Cadoni, E.; Dotta, M.; Forni, D.; Bianchi, S.; Kaufmann, H.

    2012-08-01

    The mechanical properties in tension of two aluminium alloys (AA5059-H131 and AA7039-T651) used in armour applications were determined from tests carried out over a wide range of strain-rates on round specimens. The experimental research was developed in the DynaMat laboratory of the University of Applied Sciences of Southern Switzerland. The target strain rates were set at the following four levels: 10-3, 30, 300 and 1000s-1. The quasi-static tests were performed with a universal electromechanical machine, whereas a hydro-pneumatic machine and a Split Hopkinson Tensile Bar apparatus were used for medium and high strain-rates respectively. The required parameters by the Johnson-Cook constitutive law were also determined.

  4. High strain rates effects in quasi-isentropic compression of solids

    SciTech Connect

    Ravelo, Ramon; Holian, Brad L; Germann, Timothy C

    2009-01-01

    We have performed large-scale molecular-dynamics (MD) simulations of shock loading and quasi-isentropic compression in defective copper crystals, modeling the interatomic interactions with an embedded-atom method potential. For samples with a relatively low density of pre-existing defects, the strain rate dependence of the flow stress follows a power law in the 10{sup 9}-10{sup 12} s{sup -1} regime with an exponent of 0.40. For initially damaged, isotropic crystals the flow stress exhibits a narrow linear region in strain rate, which then bends over at high strain rates in a manner reminiscent of shear thinning in fluids. The MD results can be described by a modification of Eyring's theory of Couette shear flow in fluids.

  5. Molecular dynamics simulation of temperature and strain rate effects on the elastic properties of bimetallic Pd-Pt nanowires

    NASA Astrophysics Data System (ADS)

    Sankaranarayanan, Subramanian K. R. S.; Bhethanabotla, Venkat R.; Joseph, Babu

    2007-10-01

    Molecular dynamics simulation is used to investigate the mechanical properties of infinitely long, cylindrical bimetallic Pd-Pt nanowires, with an approximate diameter of 1.4nm and two different compositions (25% and 50% Pt). The nanowires are subjected to uniaxial tensile strain along the [001] axis with varying strain rates of 0.05%ps-1 , and 5.0%ps-1 , at simulation temperatures of 50 and 300K , to study the effects of strain rates and thermal conditions on the deformation characteristics and mechanical properties of the nanowire. The deformation and rupture mechanism of these nanowires is explored in detail. Comparisons to the behavior exhibited by pure Pd and Pt nanowires of similar diameter are also made. The effect of lattice mismatch on the observed deformation modes in bimetallic nanowires is also discussed. Our simulations indicate that Pd-Pt alloy nanowires of various compositions, with little lattice mismatch between Pd and Pt atoms, undergo similar deformation and rupture upon uniaxial stretching. It is found that yielding and fracture mechanisms depend on the applied strain rate as well as atomic arrangement and temperature. At low temperature and strain rate, where crystal order and stability are highly preserved, the calculated stress-strain response of pure Pt and Pd as well as Pd-Pt alloy nanowires showed clear periodic, stepwise dislocation-relaxation behavior. Crystalline to amorphous transformation takes place at high strain rates (5%ps-1) , with amorphous melting detected at 300K . Deformation of nanowires at higher strain rates and low temperature, where the superplasticity characteristic is significantly enhanced, results in the development of a multishell helical structure. Mechanical properties of the alloy nanowires are significantly different from those of bulk phase and are dictated by the applied strain rate, temperature, alloy composition, as well as the structural rearrangement associated with nanowire elongation. We find that Young

  6. Effect of growth rate on plasmid DNA production and metabolic performance of engineered Escherichia coli strains.

    PubMed

    Wunderlich, Martin; Taymaz-Nikerel, Hilal; Gosset, Guillermo; Ramírez, Octavio T; Lara, Alvaro R

    2014-03-01

    Two engineered Escherichia coli strains, designated VH33 and VH34, were compared to their parent strain W3110 in chemostat mode during plasmid DNA (pDNA) production. In strain VH33 the glucose uptake system was modified with the aim of reducing overflow metabolism. The strain VH34 has an additional deletion of the pyruvate kinase A gene (pykA) to increase pDNA formation. pDNA formation rates as well as kinetic and stoichiometric parameters were investigated in dependence of the growth rate within a range from 0.02 to 0.25 h(-1). Differences between strains were found in terms of the biomass yields on nitrogen and oxygen, as well as on the cell maintenance coefficients. The deletion of pykA led to a significantly increased pDNA yield and productivity. At an optimal growth rate of 0.20 h(-1) it was nearly 60% higher than that of W3110 and VH33. Metabolic fluxes calculated by metabolite balance analysis showed differences mainly in reactions catalyzed by pyruvate kinase and glucose 6-phosphate dehydrogenase. The obtained data are useful for the design of cultivation schemes for pDNA production by E. coli.

  7. Strain rate effects on the mechanical behavior of two Dual Phase steels in tension

    NASA Astrophysics Data System (ADS)

    Cadoni, E.; Singh, N. K.; Forni, D.; Singha, M. K.; Gupta, N. K.

    2016-05-01

    This paper presents an experimental investigation on the strain rate sensitivity of Dual Phase steel 1200 (DP1200) and Dual Phase steel 1400 (DP1400) under uni-axial tensile loads in the strain rate range from 0.001 s-1 to 600 s-1. These materials are advanced high strength steels (AHSS) having high strength, high capacity to dissipate crash energy and high formability. Flat sheet specimens of the materials having gauge length 10 mm, width 4 mm and thickness 2 mm (DP1200) and 1.25 mm (DP1400), are tested at room temperature (20∘C) on electromechanical universal testing machine to obtain their stress-strain relation under quasi-static condition (0.001 s-1), and on Hydro-Pneumatic machine and modified Hopkinson bar to study their mechanical behavior at medium (3 s-1, and 18 s-1) and high strain rates (200 s-1, 400 s-1, and 600 s-1) respectively. Tests under quasi-static condition are performed at high temperature (200∘C) also, and found that tensile flow stress is a increasing function of temperature. The stress-strain data has been analysed to determine the material parameters of the Cowper-Symonds and the Johnson-Cook models. A simple modification of the Johnson-Cook model has been proposed in order to obtain a better fit of tests at high temperatures. Finally, the fractographs of the broken specimens are taken by scanning electron microscope (SEM) to understand the fracture mechanism of these advanced high strength steels at different strain rates.

  8. Hydrostatic Stress Effects Incorporated Into the Analysis of the High-Strain-Rate Deformation of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Roberts, Gary D.

    2003-01-01

    Procedures for modeling the effect of high strain rate on composite materials are needed for designing reliable composite engine cases that are lighter than the metal cases in current use. The types of polymer matrix composites that are likely to be used in such an application have a deformation response that is nonlinear and that varies with strain rate. The nonlinearity and strain rate dependence of the composite response is primarily due to the matrix constituent. Therefore, in developing material models to be used in the design of impact-resistant composite engine cases, the deformation of the polymer matrix must be correctly analyzed. However, unlike in metals, the nonlinear response of polymers depends on the hydrostatic stresses, which must be accounted for within an analytical model. An experimental program has been carried out through a university grant with the Ohio State University to obtain tensile and shear deformation data for a representative polymer for strain rates ranging from quasi-static to high rates of several hundred per second. This information has been used at the NASA Glenn Research Center to develop, characterize, and correlate a material model in which the strain rate dependence and nonlinearity (including hydrostatic stress effects) of the polymer are correctly analyzed. To obtain the material data, Glenn s researchers designed and fabricated test specimens of a representative toughened epoxy resin. Quasi-static tests at low strain rates and split Hopkinson bar tests at high strain rates were then conducted at the Ohio State University. The experimental data confirmed the strong effects of strain rate on both the tensile and shear deformation of the polymer. For the analytical model, Glenn researchers modified state variable constitutive equations previously used for the viscoplastic analysis of metals to allow for the analysis of the nonlinear, strain-rate-dependent polymer deformation. Specifically, we accounted for the effects of

  9. Incorporation of Mean Stress Effects into the Micromechanical Analysis of the High Strain Rate Response of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Roberts, Gary D.; Gilat, Amos

    2002-01-01

    The results presented here are part of an ongoing research program, to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to high strain rate impact loads. A micromechanics approach is employed in this work, in which state variable constitutive equations originally developed for metals have been modified to model the deformation of the polymer matrix, and a strength of materials based micromechanics method is used to predict the effective response of the composite. In the analysis of the inelastic deformation of the polymer matrix, the definitions of the effective stress and effective inelastic strain have been modified in order to account for the effect of hydrostatic stresses, which are significant in polymers. Two representative polymers, a toughened epoxy and a brittle epoxy, are characterized through the use of data from tensile and shear tests across a variety of strain rates. Results computed by using the developed constitutive equations correlate well with data generated via experiments. The procedure used to incorporate the constitutive equations within a micromechanics method is presented, and sample calculations of the deformation response of a composite for various fiber orientations and strain rates are discussed.

  10. Environmental and High-Strain Rate effects on composites for engine applications

    NASA Technical Reports Server (NTRS)

    Chamis, C. C.; Smith, G. T.

    1982-01-01

    The Lewis Research Center is conducting a series of programs intended to investigate and develop the application of composite materials to structural components for turbojet engines. A significant part of that effort is directed to establishing resistance, defect growth, and strain rate characteristics of composite materials over the wide range of environmental and load conditions found in commercial turbojet engine operations. Both analytical and experimental efforts are involved.

  11. Deformation temperature, strain rate, and irradiation microstructure effects on localized plasticity in 304L SS

    SciTech Connect

    Cole, J.I.; Brimhall, J.L.; Vetrano, J.S.; Bruemmer, S.M.

    1995-12-31

    The present study examines the deformation behavior of ion-irradiated, low-carbon 304L stainless steel to investigate the influence of irradiation microstructure, deformation temperature and strain rate on localized plasticity. Dislocation loop character, size and density are linked to changes in deformation character. Lower doses produce small faulted loops and stacking fault tetrahedra that impede dislocation mobility. Dislocations are pinned at defects and require higher stress to break free from the defects. Larger defects take the form of faulted Frank loops that can interact with glide dislocations to form microtwins at lower temperatures and faster strain rates. Deformation at higher temperatures and slower strain rates promotes interactions between glide dislocations and loops leading to loop annihilation. Dislocation free zones or ``channels`` form where further plastic deformation is highly localized. Results are compared to limited observations for neutron-irradiated materials. These irradiation-induced changes can be an important concern for light-water reactor (LWR) stainless steel (SS) structural components due to a reduced damage tolerance, and potential susceptibility to environmental cracking such as irradiation-assisted stress corrosion cracking (IASCC).

  12. Grain size effects on the high strain rate deformation of copper

    NASA Astrophysics Data System (ADS)

    Stevenson, Michael Earle

    The high strain rate (>104/s) mechanical properties of OFHC copper were studied by the Taylor impact test for a series of copper grain sizes from 31 to 152 mum. The results are analyzed by both analytical and finite element. There is a significant increase in the dynamic strength of OFHC copper for strain rates greater than approximately 104/s. This strength increase is also dependent upon the grain size of the OFHC copper prior to testing and follows a classical Hall-Petch relationship. In addition to the analytical and finite element models, a universal dynamic stress-strain curve was developed and constructed for each grain size of the OFHC copper. The characterization parameters determined from the universal dynamic stress-strain curve are also grain size dependent. Many of these parameters also follow the classical Hall-Petch trend. Post-impact microstructures of the copper can be generalized into five distinct regions. Beginning at the specimen impact face, those regions are: (i) a nanocrystalline, or sub-micron grain size layer; (ii) a dynamically recrystallized region; (iii) a region of high density (111)[112¯] twinning; (iv) a section dominated by dislocation plastic flow, or slip and (v) the specimen portion where the deformation is completely elastic. The five regions can be related to the mechanical properties derived from the individual models and the universal dynamic stress-strain curve with consideration of the initial microstructure of the copper. The results of this dissertation suggest that there is a direct linkage between the dynamic mechanical state of stress during the impact tests and both the initial and final metallurgical microstructures of the copper.

  13. Effect of strain rate on twinning and room temperature ductility of TiAl with fine equiaxed microstructure

    SciTech Connect

    Imayev, V.M.; Imayev, R.M.; Salishchev, G.A.; Shagiev, M.R.; Kuznetsov, A.V.; Povarova, K.B.

    1997-04-15

    It is known that as the strain rate rises, the room temperature ductility of intermetallics increases. This is usually associated with the influence of environment. But in {gamma}-titanium aluminides (TiAl) the non-monotonous strain-rate dependence of ductility with a maximum at the certain rate is observed and therefore it cannot be explained only by the influence of environment. Meanwhile, it is known that the ductility improvement observed in some metals with the increase of strain rate is caused by the involving new slip and twinning systems in course of deformation. As for TiAl, it should be taken into account that as the strain rate increases, resistance to dislocation moving increases and the twinning may become the most preferable deformation mode, since the value of the Burgerous vector for twinning dislocation is less than that for superdislocation. In this case, the development of twinning may determine to a great extent a plastic flow of the intermetallic. Reasoning from this, the aim of the present work is to study the effect of strain rate on the twinning development and the ductility of stoichiometric {gamma}-titanium aluminide with fine equiaxed microstructure which provides a transition from planar slip to homogeneous one and makes the greatest ductility available.

  14. Effect of forging strain rate and deformation temperature on the mechanical properties of warm-worked 304L stainless steel

    SciTech Connect

    Switzner, N. T.; Van Tyne, C. J.; Mataya, M. C.

    2010-01-25

    Stainless steel 304L forgings were produced with four different types of production forging equipment – hydraulic press, mechanical press, screw press, and high-energy rate forging (HERF). Each machine imparted a different nominal strain rate during the deformation. The final forgings were done at the warm working (low hot working) temperatures of 816 °C, 843°C, and 871°C. The objectives of the study were to characterize and understand the effect of industrial strain rates (i.e. processing equipment), and deformation temperature on the mechanical properties for the final component. Some of the components were produced with an anneal prior to the final forging while others were deformed without the anneal. The results indicate that lower strain rates produced lower strength and higher ductility components, but the lower strain rate processes were more sensitive to deformation temperature variation and resulted in more within-part property variation. The highest strain rate process, HERF, resulted in slightly lower yield strength due to internal heating. Lower processing temperatures increased strength, decreased ductility but decreased within-part property variation. The anneal prior to the final forging produced a decrease in strength, a small increase in ductility, and a small decrease of within-part property variation.

  15. Effect of strain rates on deformation behaviors of an in situ Ti-based metallic glass matrix composite

    NASA Astrophysics Data System (ADS)

    Jiao, Z. M.; Wang, Z. H.; Chu, M. Y.; Wang, Y. S.; Yang, H. J.; Qiao, J. W.

    2016-06-01

    Quasi-static and dynamic deformation behaviors of an in situ dendrite-reinforced metallic glass matrix composite: Ti56Zr18V10Cu4Be12 were investigated. Upon quasi-static compression, the composite exhibits distinguished work hardening, accompanied by the ultimate strength of 1290 MPa and the plasticity of 20 %. The improved plasticity is attributed to the multiplication of shear bands within the glass matrix and pileups of dislocations within the dendrites. Upon dynamic compression, the stable plastic flow prevails and the yielding stress increases with the strain rate. The macroscopic plasticity decreases considerably, since the shear bands cannot be effectively hindered by dendrites with deteriorated toughness. The dendrite-dominated mechanism results in the positive strain-rate sensitivity, and the Cowper-Symonds model is employed to depict the strain-rate dependency of yielding strength.

  16. An experimental investigation of strain rate, temperature and humidity effects on the mechanical behavior of a perfluorosulfonic acid membrane

    NASA Astrophysics Data System (ADS)

    Lu, Zongwen; Lugo, Melissa; Santare, Michael H.; Karlsson, Anette M.; Busby, F. Colin; Walsh, Peter

    2012-09-01

    The time-dependent hygro-thermal mechanical behavior of a perfluorosulfonic acid (PFSA) membrane (Nafion® 211 membrane) commonly used in Proton Exchange Membrane Fuel Cells (PEMFCs) is investigated at selected strain rates for a broad range of temperatures and humidities. Tensile tests and relaxation tests are conducted to determine Young's modulus and proportional limit stress as functions of strain rate, temperature and humidity. The results show that Young's modulus and proportional limit stress increase as the strain rate increases, and decrease as the temperature or humidity increases. The results also show that the mechanical response of Nafion® 211 membrane is more sensitive to typical changes in strain rate or temperature than to typical changes in humidity. In addition, two temperature/humidity cycles are conducted to determine the steady state swelling behavior of Nafion® 211 membrane as a function of temperature and humidity. The results show that the membrane swells with increasing temperature and humidity, and that there is little or no hygro-thermal history effect for the swelling strains.

  17. Effect of strain rate and temperature on mechanical properties of selected building Polish steels

    NASA Astrophysics Data System (ADS)

    Moćko, Wojciech; Kruszka, Leopold

    2015-09-01

    Currently, the computer programs of CAD type are basic tool for designing of various structures under impact loading. Application of the numerical calculations allows to substantially reduce amount of time required for the design stage of such projects. However, the proper use of computer aided designing technique requires input data for numerical software including elastic-plastic models of structural materials. This work deals with the constitutive model developed by Rusinek and Klepaczko (RK) applied for the modelling of mechanical behaviour of selected grades structural St0S, St3SX, 18GS and 34GS steels and presents here results of experimental and empirical analyses to describe dynamic elastic-plastic behaviours of tested materials at wide range of temperature. In order to calibrate the RK constitutive model, series of compression tests at wide range of strain rates, including static, quasi-static and dynamic investigations at lowered, room and elevated temperatures, were carried out using two testing stands: servo-hydraulic machine and split Hopkinson bar. The results were analysed to determine influence of temperature and strain rate on visco-plastic response of tested steels, and show good correlation with experimental data.

  18. High strain rate behavior of polyurea compositions

    NASA Astrophysics Data System (ADS)

    Joshi, Vasant S.; Milby, Christopher

    2012-03-01

    High-strain-rate response of three polyurea compositions with varying molecular weights has been investigated using a Split Hopkinson Pressure Bar arrangement equipped with aluminum bars. Three polyurea compositions were synthesized from polyamines (Versalink, Air Products) with a multi-functional isocyanate (Isonate 143L, Dow Chemical). Amines with molecular weights of 1000, 650, and a blend of 250/1000 have been used in the current investigation. These materials have been tested to strain rates of over 6000/s. High strain rate results from these tests have shown varying trends as a function of increasing strain. While higher molecular weight composition show lower yield, they do not show dominant hardening behavior at lower strain. On the other hand, the blend of 250/1000 show higher load bearing capability but lower strain hardening effects than the 600 and 1000 molecular weight amine based materials. Results indicate that the initial increase in the modulus of the blend of 250/1000 may lead to the loss of strain hardening characteristics as the material is compressed to 50% strain, compared to 1000 molecular weight amine based material.

  19. Strain Rate Effects and Temperature History Effects for Three Different Tempers of 4340 VAR Steel

    DTIC Science & Technology

    1984-07-01

    45, pp 60-66 March, 1978. 17. C.F. Hickey, Jr. and A. A. Anctil, "Split Heat Mechanical Property Comparison of ESR and VAR 4340 Steel ", A•MMRC...Embrittlement in High Hardness ESR 4340 Steel Forgings", ANMRC Technical Report 82-1, Army Materials and Mechanics Research Center, Watertown, Mass, January, 1982...Effects and Temperature History Effects for Three Different Tempers of 4340 VAR Steel . 0 by S. Tanimura and J. Duffy DTICr:fti Army Research Office . . 1

  20. Acute Radiation Effects on Cardiac Function Detected by Strain Rate Imaging in Breast Cancer Patients

    SciTech Connect

    Erven, Katrien; Jurcut, Ruxandra; Weltens, Caroline; Giusca, Sorin; Ector, Joris; Wildiers, Hans; Van den Bogaert, Walter; Voigt, Jens-Uwe

    2011-04-01

    Purpose: To investigate the occurrence of early radiation-induced changes in regional cardiac function using strain rate imaging (SRI) by tissue Doppler echocardiography. Methods and Materials: We included 20 left-sided and 10 right-sided breast cancer patients receiving radiotherapy (RT) to the breast or chest wall. Standard echocardiography and SRI were performed before RT (baseline), immediately after RT (post-RT), and at 2 months follow-up (FUP) after RT. Regional strain (S) and strain rate (SR) values were obtained from all 18 left ventricular (LV) segments. Data were compared to the regional radiation dose. Results: A reduction in S was observed post-RT and at FUP in left-sided patients (S{sub post-RT}: -17.6 {+-} 1.5%, and S{sub FUP}: -17.4 {+-} 2.3%, vs. S{sub baseline}: -19.5 {+-} 2.1%, p < 0.001) but not in right-sided patients. Within the left-sided patient group, S and SR were significantly reduced after RT in apical LV segments (S{sub post-RT}: -15.3 {+-} 2.5%, and S{sub FUP}: -14.3 {+-} 3.7%, vs. S{sub baseline}: -19.3 {+-} 3.0%, p < 0.01; and SR{sub post-RT}: -1.06 {+-} 0.15 s {sup -1}, and SR{sub FUP}: -1.16 {+-} 0.28 s {sup -1}, vs. SR{sub baseline}: -1.29 {+-} 0.27s {sup -1}, p = 0.01), but not in mid- or basal segments. Furthermore, we observed that segments exposed to more than 3 Gy showed a significant decrease in S after RT (S{sub post-RT}: -16.1 {+-} 1.6%, and S{sub FUP}: -15.8 {+-} 3.4%, vs. S{sub baseline}: -18.9 {+-} 2.6%, p < 0.001). This could not be observed in segments receiving less than 3 Gy. Conclusions: SRI shows a dose-related regional decrease in myocardial function after RT. It might be a useful tool in the evaluation of modern RT techniques, with respect to cardiac toxicity.

  1. Microstructural evolution during ultra-rapid annealing of severely deformed low-carbon steel: strain, temperature, and heating rate effects

    NASA Astrophysics Data System (ADS)

    Mostafaei, M. A.; Kazeminezhad, M.

    2016-07-01

    An interaction between ferrite recrystallization and austenite transformation in low-carbon steel occurs when recrystallization is delayed until the intercritical temperature range by employing high heating rate. The kinetics of recrystallization and transformation is affected by high heating rate and such an interaction. In this study, different levels of strain are applied to low-carbon steel using a severe plastic deformation method. Then, ultra-rapid annealing is performed at different heating rates of 200-1100°C/s and peak temperatures of near critical temperature. Five regimes are proposed to investigate the effects of heating rate, strain, and temperature on the interaction between recrystallization and transformation. The microstructural evolution of severely deformed low-carbon steel after ultra-rapid annealing is investigated based on the proposed regimes. Regarding the intensity and start temperature of the interaction, different microstructures consisting of ferrite and pearlite/martensite are formed. It is found that when the interaction is strong, the microstructure is refined because of the high kinetics of transformation and recrystallization. Moreover, strain shifts an interaction zone to a relatively higher heating rate. Therefore, severely deformed steel should be heated at relatively higher heating rates for it to undergo a strong interaction.

  2. The Effects of Strain and Strain Rate on the Spatial Separation/Segregation of Olivine and Orthopyroxene in a Synthetic Harzburgite

    NASA Astrophysics Data System (ADS)

    Sundberg, M.; Cooper, R. F.

    2004-12-01

    The plastic rheology of polyphase aggregates incorporates the grain-matrix deformation of the component phases plus grain- and solid-state phase-boundary sliding. The grain- and phase-boundary sliding acts in kinetic series with the grain-matrix mechanisms; in rheologies involving dislocation deformation, the boundary sliding component is almost never rate-limiting [e.g., Crossman and Ashby, 1975]; on the other hand, for diffusional rheologies, the boundary sliding can be both mechanically dominant and rate-limiting. For a given set of thermodynamic (e.g., temperature, pressure, deviatoric stress) and microstructural (e.g., grain size, lattice-preferred orientation) conditions, the energy-dissipation process for the deforming polyphase aggregate must involve the strain-effected separation of the phases, based upon the relative sliding (effective) viscosities of the grain boundaries and phase boundaries. The periodicity of the phase separation should be a function of the strain rate (or, conversely, for a given set of potentials, the aggregate strain rate will be one manifestation of the phase periodicity). We are engaged in an experimental study of the phase-separation scaling physics involved in the solid-state deformation of harzburgite. Specifically, we have prepared synthetic aggregates consisting of a 50:50 (by weight) mixture of ferromagnesian olivine and orthopyroxene, employing pulverized natural material; the hot-pressed aggregates have a grain size of approximately 5 micrometers. For the conditions employed in our experiments (Griggs molten salt confining-medium apparatus in simple shear ; 17 kb; 1200 oC; 10-5-10-4 s-1; strains of 3-4), the aggregates deform by boundary diffusional creep, conditions that specifically interrogate the relative viscosity of ol-ol and opx-opx grain boundaries and ol-opx phase boundaries. Backscattered electron imaging is employed to characterize the morphology of phases before and after deformation.

  3. The effects of molecular weight on the single lap shear creep and constant strain rate behavior of thermoplastic polyimidesulfone adhesive

    NASA Technical Reports Server (NTRS)

    Dembosky, Stanley K.; Sancaktar, Erol

    1985-01-01

    The bonded shear creep and constant strain rate behaviors of zero, one, and three percent endcapped thermoplastic polyimidesulfone adhesive were examined at room and elevated temperatures. Endcapping was accomplished by the addition of phthalic anhydrides. The primary objective was to determine the effects of molecular weight on the mechanical properties of the adhesive. Viscoelastic and nonlinear elastic constitutive equations were utilized to model the adhesive. Ludwik's and Crochet's relations were used to describe the experimental failure data. The effects of molecular weight changes on the above mentioned mechanical behavior were assessed. The viscoelastic Chase-Goldsmith and elastic nonlinear relations gave a good fit to the experimental stress strain behavior. Crochet's relations based on Maxwell and Chase-Goldsmith models were fit to delayed failure data. Ludwik's equations revealed negligible rate dependence. Ultimate stress levels and the safe levels for creep stresses were found to decrease as molecular weight was reduced.

  4. Approximate Analysis on Strain Rate Effects and Behavior of Stress and Strain Fields at the Crack Tip in Mode II in Metallic Materials. Appendix Number 1

    DTIC Science & Technology

    1992-10-01

    increasing the loading rate, specimens smaller in dimensions can be employed in KIC tests at high loading rates. An example of correlation between B and...difficulties arise in numerical simulation of crack behavior at high loading rates. An analytic solution for the stress field at a stationary crack tip in...with prime attention paid to use adequate stress-strain, strain-rate, temperature constitutive relations governing material behavior at the crack tip

  5. Effects that different types of sports have on the hearts of children and adolescents and the value of two-dimensional strain-strain-rate echocardiography.

    PubMed

    Binnetoğlu, Fatih Köksal; Babaoğlu, Kadir; Altun, Gürkan; Kayabey, Özlem

    2014-01-01

    Whether the hypertrophy found in the hearts of athletes is physiologic or a risk factor for the progression of pathologic hypertrophy remains controversial. The diastolic and systolic functions of athletes with left ventricular (LV) hypertrophy usually are normal when measured by conventional methods. More precise assessment of global and regional myocardial function may be possible using a newly developed two-dimensional (2D) strain echocardiographic method. This study evaluated the effects that different types of sports have on the hearts of children and adolescents and compared the results of 2D strain and strain-rate echocardiographic techniques with conventional methods. Athletes from clubs for five different sports (basketball, swimming, football, wrestling, and tennis) who had practiced regularly at least 3 h per week during at least the previous 2 years were included in the study. The control group consisted of sedentary children and adolescents with no known cardiac or systemic diseases (n = 25). The athletes were grouped according to the type of exercise: dynamic (football, tennis), static (wrestling), or static and dynamic (basketball, swimming). Shortening fraction and ejection fraction values were within normal limits for the athletes in all the sports disciplines. Across all 140 athletes, LV geometry was normal in 58 athletes (41.4 %), whereas 22 athletes (15.7 %) had concentric remodeling, 20 (14.3 %) had concentric hypertrophy, and 40 (28.6 %) had eccentric hypertrophy. Global LV longitudinal strain values obtained from the average of apical four-, two-, and three-chamber global strain values were significantly lower for the basketball players than for all the other groups (p < 0.001).

  6. High strain rate behaviour of polypropylene microfoams

    NASA Astrophysics Data System (ADS)

    Gómez-del Río, T.; Garrido, M. A.; Rodríguez, J.; Arencón, D.; Martínez, A. B.

    2012-08-01

    Microcellular materials such as polypropylene foams are often used in protective applications and passive safety for packaging (electronic components, aeronautical structures, food, etc.) or personal safety (helmets, knee-pads, etc.). In such applications the foams which are used are often designed to absorb the maximum energy and are generally subjected to severe loadings involving high strain rates. The manufacture process to obtain polymeric microcellular foams is based on the polymer saturation with a supercritical gas, at high temperature and pressure. This method presents several advantages over the conventional injection moulding techniques which make it industrially feasible. However, the effect of processing conditions such as blowing agent, concentration and microfoaming time and/or temperature on the microstructure of the resulting microcellular polymer (density, cell size and geometry) is not yet set up. The compressive mechanical behaviour of several microcellular polypropylene foams has been investigated over a wide range of strain rates (0.001 to 3000 s-1) in order to show the effects of the processing parameters and strain rate on the mechanical properties. High strain rate tests were performed using a Split Hopkinson Pressure Bar apparatus (SHPB). Polypropylene and polyethylene-ethylene block copolymer foams of various densities were considered.

  7. The strain rate effect on the buckling of single-layer MoS2.

    PubMed

    Jiang, Jin-Wu

    2015-01-15

    The Euler buckling theory states that the buckling critical strain is an inverse quadratic function of the length for a thin plate in the static compression process. However, the suitability of this theory in the dynamical process is unclear, so we perform molecular dynamics simulations to examine the applicability of the Euler buckling theory for the fast compression of the single-layer MoS2. We find that the Euler buckling theory is not applicable in such dynamical process, as the buckling critical strain becomes a length-independent constant in the buckled system with many ripples. However, the Euler buckling theory can be resumed in the dynamical process after restricting the theory to an individual ripple in the buckled structure.

  8. The Strain Rate Effect on the Buckling of Single-Layer MoS2

    PubMed Central

    Jiang, Jin-Wu

    2015-01-01

    The Euler buckling theory states that the buckling critical strain is an inverse quadratic function of the length for a thin plate in the static compression process. However, the suitability of this theory in the dynamical process is unclear, so we perform molecular dynamics simulations to examine the applicability of the Euler buckling theory for the fast compression of the single-layer MoS2. We find that the Euler buckling theory is not applicable in such dynamical process, as the buckling critical strain becomes a length-independent constant in the buckled system with many ripples. However, the Euler buckling theory can be resumed in the dynamical process after restricting the theory to an individual ripple in the buckled structure. PMID:25588352

  9. Multiplicative earthquake likelihood models incorporating strain rates

    NASA Astrophysics Data System (ADS)

    Rhoades, D. A.; Christophersen, A.; Gerstenberger, M. C.

    2017-01-01

    SUMMARYWe examine the potential for <span class="hlt">strain-rate</span> variables to improve long-term earthquake likelihood models. We derive a set of multiplicative hybrid earthquake likelihood models in which cell <span class="hlt">rates</span> in a spatially uniform baseline model are scaled using combinations of covariates derived from earthquake catalogue data, fault data, and <span class="hlt">strain-rates</span> for the New Zealand region. Three components of the <span class="hlt">strain</span> <span class="hlt">rate</span> estimated from GPS data over the period 1991-2011 are considered: the shear, rotational and dilatational <span class="hlt">strain</span> <span class="hlt">rates</span>. The hybrid model parameters are optimised for earthquakes of M 5 and greater over the period 1987-2006 and tested on earthquakes from the period 2012-2015, which is independent of the <span class="hlt">strain</span> <span class="hlt">rate</span> estimates. The shear <span class="hlt">strain</span> <span class="hlt">rate</span> is overall the most informative individual covariate, as indicated by Molchan error diagrams as well as multiplicative modelling. Most models including <span class="hlt">strain</span> <span class="hlt">rates</span> are significantly more informative than the best models excluding <span class="hlt">strain</span> <span class="hlt">rates</span> in both the fitting and testing period. A hybrid that combines the shear and dilatational <span class="hlt">strain</span> <span class="hlt">rates</span> with a smoothed seismicity covariate is the most informative model in the fitting period, and a simpler model without the dilatational <span class="hlt">strain</span> <span class="hlt">rate</span> is the most informative in the testing period. These results have implications for probabilistic seismic hazard analysis and can be used to improve the background model component of medium-term and short-term earthquake forecasting models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MTDM...20...45S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MTDM...20...45S"><span id="translatedtitle">The <span class="hlt">effect</span> of heat developed during high <span class="hlt">strain</span> <span class="hlt">rate</span> deformation on the constitutive modeling of amorphous polymers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Safari, Keivan H.; Zamani, Jamal; Guedes, Rui M.; Ferreira, Fernando J.</p> <p>2016-02-01</p> <p>An adiabatic constitutive model is proposed for large <span class="hlt">strain</span> deformation of polycarbonate (PC) at high <span class="hlt">strain</span> <span class="hlt">rates</span>. When the <span class="hlt">strain</span> <span class="hlt">rate</span> is sufficiently high such that the heat generated does not have time to transfer to the surroundings, temperature of material rises. The high <span class="hlt">strain</span> <span class="hlt">rate</span> deformation behavior of polymers is significantly affected by temperature-dependent constants and thermal softening. Based on the isothermal model which first was introduced by Mulliken and Boyce et al. (Int. J. Solids Struct. 43:1331-1356, 2006), an adiabatic model is proposed to predict the yield and post-yield behavior of glassy polymers at high <span class="hlt">strain</span> <span class="hlt">rates</span>. When calculating the heat generated and the temperature changes during the step by step simulation of the deformation, temperature-dependent elastic constants are incorporated to the constitutive equations. Moreover, better prediction of softening phenomena is achieved by the new definition for softening parameters of the proposed model. The constitutive model has been implemented numerically into a commercial finite element code through a user material subroutine (VUMAT). The experimental results, obtained using a split Hopkinson pressure bar, are supported by dynamic mechanical thermal analysis (DMTA) and Decompose/Shift/Reconstruct (DSR) method. Comparison of adiabatic model predictions with experimental data demonstrates the ability of the model to capture the characteristic features of stress-<span class="hlt">strain</span> curve of the material at very high <span class="hlt">strain</span> <span class="hlt">rates</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030065962','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030065962"><span id="translatedtitle">Implementation of an Associative Flow Rule Including Hydrostatic Stress <span class="hlt">Effects</span> Into the High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Deformation Analysis of Polymer Matrix Composites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldberg, Robert K.; Roberts, Gary D.; Gilat, Amos</p> <p>2003-01-01</p> <p>A previously developed analytical formulation has been modified in order to more accurately account for the <span class="hlt">effects</span> of hydrostatic stresses on the nonlinear, <span class="hlt">strain</span> <span class="hlt">rate</span> dependent deformation of polymer matrix composites. State variable constitutive equations originally developed for metals have been modified in order to model the nonlinear, <span class="hlt">strain</span> <span class="hlt">rate</span> dependent deformation of polymeric materials. To account for the <span class="hlt">effects</span> of hydrostatic stresses, which are significant in polymers, the classical J2 plasticity theory definitions of <span class="hlt">effective</span> stress and <span class="hlt">effective</span> inelastic <span class="hlt">strain</span>, along with the equations used to compute the components of the inelastic <span class="hlt">strain</span> <span class="hlt">rate</span> tensor, are appropriately modified. To verify the revised formulation, the shear and tensile deformation of two representative polymers are computed across a wide range of <span class="hlt">strain</span> <span class="hlt">rates</span>. Results computed using the developed constitutive equations correlate well with experimental data. The polymer constitutive equations are implemented within a strength of materials based micromechanics method to predict the nonlinear, <span class="hlt">strain</span> <span class="hlt">rate</span> dependent deformation of polymer matrix composites. The composite mechanics are verified by analyzing the deformation of a representative polymer matrix composite for several fiber orientation angles across a variety of <span class="hlt">strain</span> <span class="hlt">rates</span>. The computed values compare well to experimentally obtained results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003APS..DFD.KK006C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003APS..DFD.KK006C"><span id="translatedtitle">The <span class="hlt">effect</span> of turbulent <span class="hlt">strain</span> <span class="hlt">rate</span> on the viability of E.coli in simulated wastewater discharge</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cotel, Aline; Battani, Brian; Semrau, Jeremy</p> <p>2003-11-01</p> <p>During storm events, release of combined sewage overflows can and does occur throughout the United States, most notably in the Great Lakes. Such overflows can deteriorate overall water quality and also lead to the closure of recreational beaches for many reasons, including due to the presence of harmful microorganisms. Here we report on how different mixing regimes created by varying the Reynolds number of simulated wastewater discharges affect the concentration and viability of microorganisms. A laboratory model was created to simulate a typical discharge containing free-floating Escherichia coli. From the experimental results, it was apparent that in the near field (five diameters from the point of discharge) the viability of E. coli was reduced as the Reynolds number of discharge increased, and such viability was more than could be explained by dilution alone. The discrepancy between observed cell viability and dilution can be attributed to the Kolmogorov <span class="hlt">strain</span> <span class="hlt">rate</span>. Such an <span class="hlt">effect</span> on cell viability was only observed in the near field and did not occur in the far field, suggesting that one possible strategy to mitigate the impact of wastewater discharges, particularly that of combined sewer overflows would be to increase the Kolmogorov <span class="hlt">strain</span> <span class="hlt">rate</span> in the near field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011APS..SHK.Y5002J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011APS..SHK.Y5002J"><span id="translatedtitle">High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Behavior of Polyurea Compositions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Joshi, Vasant; Milby, Christopher</p> <p>2011-06-01</p> <p>Polyurea has been gaining importance in recent years due to its impact resistance properties. The actual compositions of this viscoelastic material must be tailored for specific use. It is therefore imperative to study the <span class="hlt">effect</span> of variations in composition on the properties of the material. High-<span class="hlt">strain-rate</span> response of three polyurea compositions with varying molecular weights has been investigated using a Split Hopkinson Pressure Bar arrangement equipped with titanium bars. The polyurea compositions were synthesized from polyamines (Versalink, Air Products) with a multi-functional isocyanate (Isonate 143L, Dow Chemical). Amines with molecular weights of 1000, 650, and a blend of 250/1000 have been used in the current investigation. The materials have been tested up to <span class="hlt">strain</span> <span class="hlt">rates</span> of 6000/s. Results from these tests have shown interesting trends on the high <span class="hlt">rate</span> behavior. While higher molecular weight composition show lower yield, they do not show dominant hardening behavior. On the other hand, the blend of 250/1000 show higher load bearing capability but lower <span class="hlt">strain</span> hardening <span class="hlt">effects</span> than the 600 and 1000 molecular weight amine based materials. Refinement in experimental methods and comparison of results using aluminum Split Hopkinson Bar is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040082455','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040082455"><span id="translatedtitle">Modeling the Nonlinear, <span class="hlt">Strain</span> <span class="hlt">Rate</span> Dependent Deformation of Woven Ceramic Matrix Composites With Hydrostatic Stress <span class="hlt">Effects</span> Included</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldberg, Robert K.; Carney, Kelly S.</p> <p>2004-01-01</p> <p>An analysis method based on a deformation (as opposed to damage) approach has been developed to model the <span class="hlt">strain</span> <span class="hlt">rate</span> dependent, nonlinear deformation of woven ceramic matrix composites with a plain weave fiber architecture. In the developed model, the differences in the tension and compression response have also been considered. State variable based viscoplastic equations originally developed for metals have been modified to analyze the ceramic matrix composites. To account for the tension/compression asymmetry in the material, the <span class="hlt">effective</span> stress and <span class="hlt">effective</span> inelastic <span class="hlt">strain</span> definitions have been modified. The equations have also been modified to account for the fact that in an orthotropic composite the in-plane shear stiffness is independent of the stiffness in the normal directions. The developed equations have been implemented into a commercially available transient dynamic finite element code, LS-DYNA, through the use of user defined subroutines (UMATs). The tensile, compressive, and shear deformation of a representative plain weave woven ceramic matrix composite are computed and compared to experimental results. The computed values correlate well to the experimental data, demonstrating the ability of the model to accurately compute the deformation response of woven ceramic matrix composites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040111390','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040111390"><span id="translatedtitle">Modeling the Nonlinear, <span class="hlt">Strain</span> <span class="hlt">Rate</span> Dependent Deformation of Shuttle Leading Edge Materials with Hydrostatic Stress <span class="hlt">Effects</span> Included</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldberg, Robert K.; Carney, Kelly S.</p> <p>2004-01-01</p> <p>An analysis method based on a deformation (as opposed to damage) approach has been developed to model the <span class="hlt">strain</span> <span class="hlt">rate</span> dependent, nonlinear deformation of woven ceramic matrix composites, such as the Reinforced Carbon Carbon (RCC) material used on the leading edges of the Space Shuttle. In the developed model, the differences in the tension and compression deformation behaviors have also been accounted for. State variable viscoplastic equations originally developed for metals have been modified to analyze the ceramic matrix composites. To account for the tension/compression asymmetry in the material, the <span class="hlt">effective</span> stress and <span class="hlt">effective</span> inelastic <span class="hlt">strain</span> definitions have been modified. The equations have also been modified to account for the fact that in an orthotropic composite the in-plane shear response is independent of the stiffness in the normal directions. The developed equations have been implemented into LS-DYNA through the use of user defined subroutines (UMATs). Several sample qualitative calculations have been conducted, which demonstrate the ability of the model to qualitatively capture the features of the deformation response present in woven ceramic matrix composites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20060021978','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20060021978"><span id="translatedtitle">Impact Damage and <span class="hlt">Strain</span> <span class="hlt">Rate</span> <span class="hlt">Effects</span> for Toughened Epoxy Composite Structures</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chamis, Christos C.; Minnetyan, Levon</p> <p>2006-01-01</p> <p>Structural integrity of composite systems under dynamic impact loading is investigated herein. The GENOA virtual testing software environment is used to implement the <span class="hlt">effects</span> of dynamic loading on fracture progression and damage tolerance. Combinations of graphite and glass fibers with a toughened epoxy matrix are investigated. The <span class="hlt">effect</span> of a ceramic coating for the absorption of impact energy is also included. Impact and post impact simulations include verification and prediction of (1) Load and Impact Energy, (2) Impact Damage Size, (3) Maximum Impact Peak Load, (4) Residual Strength, (5) Maximum Displacement, (6) Contribution of Failure Modes to Failure Mechanisms, (7) Prediction of Impact Load Versus Time, and (8) Damage, and Fracture Pattern. A computer model is utilized for the assessment of structural response, progressive fracture, and defect/damage tolerance characteristics. Results show the damage progression sequence and the changes in the structural response characteristics due to dynamic impact. The fundamental premise of computational simulation is that the complete evaluation of composite fracture requires an assessment of ply and subply level damage/fracture processes as the structure is subjected to loads. Simulation results for the graphite/epoxy composite were compared with the impact and tension failure test data, correlation and verification was obtained that included: (1) impact energy, (2) damage size, (3) maximum impact peak load, (4) residual strength, (5) maximum displacement, and (6) failure mechanisms of the composite structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950047316&hterms=seismic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dseismic','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950047316&hterms=seismic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dseismic"><span id="translatedtitle">A comparison of eastern North American seismic <span class="hlt">strain-rates</span> to glacial rebound <span class="hlt">strain-rates</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>James, Thomas S.; Bent, Allison L.</p> <p>1994-01-01</p> <p>Glacial rebound <span class="hlt">strain-rates</span> computed using a simple Laurentide glacial loading model are of the order of 10(exp -9) per year within the region of glaciation and extending several hundred kilometers beyond. The horizontal <span class="hlt">strain-rates</span> receive approximately equal contributions from horizontal and vertical velocities, a consequence of the spherical geometry adopted for the Earth model. In the eastern United States and southeastern Canada the computed <span class="hlt">strain-rates</span> are 1-3 orders of magnitude greater than an estimate of the average seismic <span class="hlt">strain-rate</span> (Anderson, 1986) and approximately 1 order of magnitude greater than predicted erosional <span class="hlt">strain-rates</span>. The predicted glacial rebound <span class="hlt">strain-rates</span> are not, in general, oriented in such a way as to augment the observed state of deviatoric stress, possibly explaining why the seismic <span class="hlt">strain-rates</span> are much smaller than the glacial rebound <span class="hlt">strain-rates</span>. An exception to this may be seismically active regions in the St. Lawrence valley.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013MSMSE..21f5016S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013MSMSE..21f5016S"><span id="translatedtitle"><span class="hlt">Effects</span> of temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> on the deformation of amorphous polyethylene: a comparison between molecular dynamics simulations and experimental results</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sahputra, I. H.; Echtermeyer, A. T.</p> <p>2013-09-01</p> <p>Molecular dynamics simulations are used to investigate the <span class="hlt">effects</span> of temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> on the deformation of amorphous polyethylene. The simulations predict the <span class="hlt">effects</span> of temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> on the stress-<span class="hlt">strain</span> responses, Young's modulus and Poisson's ratio similar to those observed in laboratory experiments performed by other researchers. The time-temperature superposition principle is applied to the Young's modulus and Poisson's ratio to form a master curve to address the discrepancies in <span class="hlt">strain</span> <span class="hlt">rates</span> between the simulations and the experiments. Differences in the numbers of monomers and chains, the degree of crystallinity and molecular orientation lead to discrepancies in the Young's modulus and Poisson's ratio between simulations and experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920011242','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920011242"><span id="translatedtitle">Environmental and <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effects</span> on graphite/epoxy composites. Final Report; M.S. Thesis, 1987</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Peimandis, Konstantinos</p> <p>1991-01-01</p> <p>The hygrothermal characterization of unidirectional graphite/epoxy composites over a range of <span class="hlt">strain</span> <span class="hlt">rates</span> was investigated. Special techniques developed for such hygrothermal characterization are also described. The mechanical properties of the composite material were obtained and analyzed by means of a time-temperature-moisture superposition principle. The results show the following: (1) the embedded gage technique was thoroughly examined and found to be appropriate for both hygrothermal expansion and mechanical <span class="hlt">strain</span> measurements; (2) all transverse properties were found to decrease with increasing temperature and moisture content; and (3) ultimate transverse properties were found to increase with <span class="hlt">strain</span> <span class="hlt">rate</span> at low temperatures but follow an opposite trend at high temperatures compared to dry specimens.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MS%26E..181a2022P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MS%26E..181a2022P"><span id="translatedtitle">A numerical and experimental study of temperature <span class="hlt">effects</span> on deformation behavior of carbon steels at high <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pouya, M.; Winter, S.; Fritsch, S.; F-X Wagner, M.</p> <p>2017-03-01</p> <p>Both in research and in the light of industrial applications, there is a growing interest in methods to characterize the mechanical behavior of materials at high <span class="hlt">strain</span> <span class="hlt">rates</span>. This is particularly true for steels (the most important structural materials), where often the <span class="hlt">strain</span> <span class="hlt">rate</span>-dependent material behavior also needs to be characterized in a wide temperature range. In this study, we use the Finite Element Method (FEM), first, to model the compressive deformation behavior of carbon steels under quasi-static loading conditions. The results are then compared to experimental data (for a simple C75 steel) at room temperature, and up to testing temperatures of 1000 °C. Second, an explicit FEM model that captures wave propagation phenomena during dynamic loading is developed to closely reflect the complex loading conditions in a Split-Hopkinson Pressure Bar (SHPB) – an experimental setup that allows loading of compression samples with <span class="hlt">strain</span> <span class="hlt">rates</span> up to 104 s-1 The dynamic simulations provide a useful basis for an accurate analysis of dynamically measured experimental data, which considers reflected elastic waves. By combining numerical and experimental investigations, we derive material parameters that capture the <span class="hlt">strain</span> <span class="hlt">rate</span>- and temperature-dependent behavior of the C75 steel from room temperature to 1000 °C, and from quasi-static to dynamic loading.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active"><span>5</span></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_5 --> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/543291','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/543291"><span id="translatedtitle"><span class="hlt">Effect</span> of test temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> on the tensile properties of high-strength, high-conductivity copper alloys</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zinkle, S.J.; Eatherly, W.S.</p> <p>1997-04-01</p> <p>The unirradiated tensile properties of wrought GlidCop AL25 (ITER grade zero, IGO) solutionized and aged CuCrZr, and cold-worked and aged and solutionized and aged Hycon 3HP{trademark} CuNiBe have been measured over the temperature range of 20-500{degrees}C at <span class="hlt">strain</span> <span class="hlt">rates</span> between 4 x 10{sup {minus}4} s{sup {minus}1} and 0.06 s{sup {minus}1}. The measured room temperature electrical conductivity ranged from 64 to 90% IACS for the different alloys. All of the alloys were relatively insensitive to <span class="hlt">strain</span> <span class="hlt">rate</span> at room temperature, but the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity of GlidCop Al25 increased significantly with increasing temperature. The CuNiBe alloys exhibited the best combination of high strength and high conductivity at room temperature. The strength of CuNiBe decreased slowly with increasing temperature. However, the ductility of CuNiBe decreased rapidly with increasing temperature due to localized deformation near grain boundaries, making these alloy heats unsuitable for typical structural applications above 300{degrees}C. The strength and uniform elongation of GlidCop Al25 decreased significantly with increasing temperature at a <span class="hlt">strain</span> <span class="hlt">rate</span> of 1 x 10{sup {minus}3} s{sup {minus}1}, whereas the total elongation was independent of test temperature. The strength and ductility of CuCrZr decreased slowly with increasing temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880012133','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880012133"><span id="translatedtitle">The <span class="hlt">effects</span> of temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> on the yielding behavior of the single crystal superalloy PWA 1480</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Milligan, Walter W.; Antolovich, Stephen D.</p> <p>1988-01-01</p> <p>Interrupted tensile tests were conducted on (001) oriented single crystals at temperatures from 20 to 1093 C. Two <span class="hlt">strain</span> <span class="hlt">rates</span> were used, 0.5 and 50 percent/min. After the tests, the deformation substructures were characterized by transmission electron microscopy. Results of these tests are given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5326716','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5326716"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> <span class="hlt">effects</span> for concrete and fiber-reinforced concrete subjected to impact loading. Final report, September 1982-August 1987</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Shah, S.P.</p> <p>1987-10-01</p> <p>Despite it's extensive use, low tensile strength has been recognized as one of the major drawbacks of concrete. Although one has learned to avoid exposing concrete structures to adverse static tensile loads, these structures cannot be shielded from short duration dynamic tensile loads. Such loads originate from sources such as impact from missiles and projectiles, wind gusts, earthquakes and machine vibrations. In addition, modern computer-aided analysis and use of concrete for special structures such as reactor containment vessels, missile storage silos and fall-out shelters, has led to a growing interest in the cracking behavior of concrete. Experimental results indicate that the fracture strength and cracking behavior of concrete are affected by the <span class="hlt">rate</span> of loading. To accurately predict the structural response under impact conditions, the knowledge of behavior of concrete at high <span class="hlt">rates</span> of loading is essential. Using a two degree of freedom model guidelines were developed for designing an impact test setup, thus enabling one to conduct impact tests free of adverse inertial <span class="hlt">effects</span>. Based on these guidelines, the author has developed an instrumented modified Charpy impact testing system. This experimental test setup was used to obtain basic information such as load-deflection relationship, fracture toughness, crack velocity (measured using Krak Gages), and load-<span class="hlt">strain</span> history during an impact fracture event of plain concrete and SFRC.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApPhA.121..823H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApPhA.121..823H"><span id="translatedtitle">The <span class="hlt">effects</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature on commercial acrylic artist paints aged one year to decades</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hagan, Eric W. S.; Charalambides, Maria N.; Young, Christina R. T.; Learner, Thomas J. S.</p> <p>2015-11-01</p> <p>Acrylic artist paints are viscoelastic composites containing a high molecular weight copolymer, pigment and a variety of additives. The glass transition temperature of the latex binder is typically slightly below ambient conditions, giving mechanical properties that are strongly dependent on <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature. In previous work, the viscoelastic behaviour of custom-formulated latex artist paints was reported for films with known volume fractions of pigment using data from uniaxial tensile tests at different <span class="hlt">strain</span> <span class="hlt">rates</span> and temperatures. Secant Young's modulus and failure <span class="hlt">strain</span> master curves were constructed for each film through time-temperature superposition, allowing predictions beyond the experimental timescale at a selected reference temperature. A similar analysis is now presented for a small set of commercial artist paints tested at ages of 1 and 27 years. Experimental shift factor values are reported with fits to the Arrhenius, WLF and Vogel Fulcher equations, along with a comparison with published data for acrylic polymers. The tensile results highlight a spectrum of properties that acrylic paints may exhibit—brittle glass to hyperelastic—depending on the conditions during deformation. Strong similarities are shown between products from different manufacturers, and the findings suggest a high degree of stability with age. A method for predicting failure as a function of <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature is also presented, and the methodology gives a framework for investigating other artist materials and the factors influencing their mechanical properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22886556','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22886556"><span id="translatedtitle"><span class="hlt">Effect</span> of glucose concentration on the <span class="hlt">rate</span> of fructose consumption in native <span class="hlt">strains</span> isolated from the fermentation of Agave duranguensis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Díaz-Campillo, M; Urtíz, N; Soto, O; Barrio, E; Rutiaga, M; Páez, J</p> <p>2012-12-01</p> <p>Studies on hexose consumption by Saccharomyces cerevisiae show that glucose is consumed faster than fructose when both are present (9:1 fructose to glucose) in the medium during the fermentation of Agave. The objective of this work was to select <span class="hlt">strains</span> of S. cerevisiae that consume fructose equal to or faster than glucose at high fructose concentrations by analyzing the influence of different glucose concentrations on the fructose consumption <span class="hlt">rate</span>. The optimal growth conditions were determined by a kinetics assay using high performance liquid chromatography (HPLC) using 50 g of glucose and 50 g of fructose per liter of synthetic medium containing peptone and yeast extract. Using the same substrate concentrations, <span class="hlt">strain</span> ITD-00185 was shown to have a higher reaction <span class="hlt">rate</span> for fructose over glucose. At 75 g of fructose and 25 g of glucose per liter, <span class="hlt">strain</span> ITD-00185 had a productivity of 1.02 gL(-1) h(-1) after 40 h and a fructose <span class="hlt">rate</span> constant of 0.071 h(-1). It was observed that glucose concentration positively influences fructose consumption when present in a 3:1 ratio of fructose to glucose. Therefore, adapted <span class="hlt">strains</span> at high fructose concentrations could be used as an alternative to traditional fermentation processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4856110','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4856110"><span id="translatedtitle">Recent advances in echocardiography: <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> imaging</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Mirea, Oana; Duchenne, Jurgen; Voigt, Jens-Uwe</p> <p>2016-01-01</p> <p>Deformation imaging by echocardiography is a well-established research tool which has been gaining interest from clinical cardiologists since the introduction of speckle tracking. Post-processing of echo images to analyze deformation has become readily available at the fingertips of the user. New parameters such as global longitudinal <span class="hlt">strain</span> have been shown to provide added diagnostic value, and ongoing efforts of the imaging societies and industry aimed at harmonizing methods will improve the technique further. This review focuses on recent advances in the field of echocardiographic <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> imaging, and provides an overview on its current and potential future clinical applications. PMID:27158476</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920014191','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920014191"><span id="translatedtitle">Matrix dominated stress/<span class="hlt">strain</span> behavior in polymeric composites: <span class="hlt">Effects</span> of hold time, nonlinearity and <span class="hlt">rate</span> dependency</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gates, Thomas S.</p> <p>1992-01-01</p> <p>In order to understand matrix dominated behavior in laminated polymer matrix composites, an elastic/viscoplastic constitutive model was developed and used to predict stress <span class="hlt">strain</span> behavior of off-axis and angle-ply symmetric laminates under in-plane, tensile axial loading. The model was validated for short duration tests at elevated temperatures. Short term stress relaxation and short term creep, <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity, and material nonlinearity were accounted for. The testing times were extended for longer durations, and periods of creep and stress relaxation were used to investigate the ability of the model to account for long term behavior. The model generally underestimated the total change in <span class="hlt">strain</span> and stress for both long term creep and long term relaxation respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100033100','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100033100"><span id="translatedtitle">Experimental Techniques for Evaluating the <span class="hlt">Effects</span> of Aging on Impact and High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Properties of Triaxial Braided Composite Materials</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pereira, J. Michael; Roberts, Gary D.; Ruggeri, Charles R.; Gilat, Amos; Matrka, Thomas</p> <p>2010-01-01</p> <p>An experimental program is underway to measure the impact and high <span class="hlt">strain</span> <span class="hlt">rate</span> properties of triaxial braided composite materials and to quantify any degradation in properties as a result of thermal and hygroscopic aging typically encountered during service. Impact tests are being conducted on flat panels using a projectile designed to induce high <span class="hlt">rate</span> deformation similar to that experienced in a jet engine fan case during a fan blade-out event. The tests are being conducted on as-fabricated panels and panels subjected to various numbers of aging cycles. High <span class="hlt">strain</span> <span class="hlt">rate</span> properties are being measured using a unique Hopkinson bar apparatus that has a larger diameter than conventional Hopkinson bars. This larger diameter is needed to measure representative material properties because of the large unit cell size of the materials examined in this work. In this paper the experimental techniques used for impact and high <span class="hlt">strain</span> <span class="hlt">rate</span> testing are described and some preliminary results are presented for both as-fabricated and aged composites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20748742','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20748742"><span id="translatedtitle">The <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature on the tensile properties of Sn-3.5Ag solder</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lang Fengqun . E-mail: fqlang325@yahoo.co.jp; Tanaka, Hiroyuki; Munegata, Osamu; Taguchi, Toshihiko; Narita, Toshio</p> <p>2005-03-15</p> <p>The tensile response of Sn-3.5% Ag solder was investigated and compared with that of a Sn-37% Pb eutectic solder at various <span class="hlt">strain</span> <span class="hlt">rates</span> from 2.38x10{sup -6} s{sup -1} to 2.38x10{sup -3} s{sup -1} over the temperature range from -50 deg. C to 150 deg. C. The relationship between tensile strength, {sigma} {sub UTS}, and <span class="hlt">strain</span> <span class="hlt">rate</span>, {epsilon}', for Sn-3.5Ag can be expressed by the equation {sigma} {sub UTS}=A{epsilon}' {sup m}. The influence of temperature on the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity index m was very slight for Sn-3.5Ag, whereas the m values of Sn-37Pb increased strongly with increasing temperature. The relationship between the tensile strength of the Sn-3.5Ag alloy and temperature follows an Arrhenius law, and the activation energy for creep was found to be 78 kJ/mol, close to that for the pipe diffusion controlled creep of tin. The microstructure and fracture morphologies of both solders were observed with a scanning electron microscope. Ag{sub 3}Sn particles were observed in the primary {beta}-Sn in the Sn-3.5Ag solder by transmission electron microscope.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19417327','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19417327"><span id="translatedtitle">Coupled <span class="hlt">effect</span> of size, <span class="hlt">strain</span> <span class="hlt">rate</span>, and temperature on the shape memory of a pentagonal Cu nanowire.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sutrakar, Vijay Kumar; Mahapatra, D Roy</p> <p>2009-01-28</p> <p>A body-centered pentagonal nanobridge structure with lattice constants c = 2.35 and a = 2.53 A has been observed under high <span class="hlt">strain</span> <span class="hlt">rate</span> tensile loading on an initially constrained [Formula: see text] Cu nanowire at various temperatures. Extensive molecular dynamics (MD) simulations have been performed using the embedded atom method (EAM) for cross-sectional dimensions ranging from 0.723 x 0.723 to 2.169 x 2.169 nm(2), temperature ranging from 10 to 600 K, and <span class="hlt">strain</span> <span class="hlt">rates</span> of 10(9)-10(7) s(-1). Formations of such pentagonal nanowire are observed for a temperature range 200-600 K for particular cross-sectional dimensions and <span class="hlt">strain</span> <span class="hlt">rates</span>. A large inelastic deformation of approximately 50% is obtained under both isothermal loading and adiabatic loading. With very high degree of repeatability of such pentagonal nanowire formation, the present findings indicate that the interesting stability property and high strength of elongated nanowires have various potential applications in nanomechanical and nanoelectronic devices. Further, we demonstrate a novel thermomechanical unloading mechanism by which it is possible to impart recovery from a pentagonal nanowire following a hysteresis loop: [Formula: see text].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006JPhy4.134.1175K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006JPhy4.134.1175K"><span id="translatedtitle"><span class="hlt">Effects</span> of <span class="hlt">strain-rate</span> and pre-fatigue on tensile properties of laser welded joint of high strength steel plates</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kobayashi, H.; Daimaruya, M.; Tsuda, H.; Horikawa, K.</p> <p>2006-08-01</p> <p>The impact tensile properties of laser welded butt joints of two kinds of high strength steel plates with the tensile strength level of 590 MPa and 780 MPa (denoted by HR590 and HR780, respectively), were investigated using split Hopkinson bar tensile testing apparatus. Impact tension tests for the joint specimens pre-fatigued were also carried out to examine the <span class="hlt">effect</span> of pre-fatigue. There were no significant <span class="hlt">effects</span> of <span class="hlt">strain-rate</span> and pre-fatigue on the dynamic and quasi-static tensile strength of laser welded butt joints. However, the decrease in the elongation of HR780 welded joints subjected high cycle pre-fatigue was observed only at a high <span class="hlt">strain-rate</span>. From the observation of fracture surface, it was found that the decrease in the elongation may be caused by a number of damages due to the combination of high cycle pre-fatigue and high <span class="hlt">strain-rate</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1258482','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1258482"><span id="translatedtitle">A multi-scale model of dislocation plasticity in α-Fe: Incorporating temperature, <span class="hlt">strain</span> <span class="hlt">rate</span> and non-Schmid <span class="hlt">effects</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lim, H.; Hale, L. M.; Zimmerman, J. A.; Battaile, C. C.; Weinberger, C. R.</p> <p>2015-01-05</p> <p>In this study, we develop an atomistically informed crystal plasticity finite element (CP-FE) model for body-centered-cubic (BCC) α-Fe that incorporates non-Schmid stress dependent slip with temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effects</span>. Based on recent insights obtained from atomistic simulations, we propose a new constitutive model that combines a generalized non-Schmid yield law with aspects from a line tension (LT) model for describing activation enthalpy required for the motion of dislocation kinks. Atomistic calculations are conducted to quantify the non-Schmid <span class="hlt">effects</span> while both experimental data and atomistic simulations are used to assess the temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effects</span>. The parameterized constitutive equation is implemented into a BCC CP-FE model to simulate plastic deformation of single and polycrystalline Fe which is compared with experimental data from the literature. This direct comparison demonstrates that the atomistically informed model accurately captures the <span class="hlt">effects</span> of crystal orientation, temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> on the flow behavior of siangle crystal Fe. Furthermore, our proposed CP-FE model exhibits temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> dependent flow and yield surfaces in polycrystalline Fe that deviate from conventional CP-FE models based on Schmid's law.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1258482-multi-scale-model-dislocation-plasticity-fe-incorporating-temperature-strain-rate-non-schmid-effects','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1258482-multi-scale-model-dislocation-plasticity-fe-incorporating-temperature-strain-rate-non-schmid-effects"><span id="translatedtitle">A multi-scale model of dislocation plasticity in α-Fe: Incorporating temperature, <span class="hlt">strain</span> <span class="hlt">rate</span> and non-Schmid <span class="hlt">effects</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Lim, H.; Hale, L. M.; Zimmerman, J. A.; ...</p> <p>2015-01-05</p> <p>In this study, we develop an atomistically informed crystal plasticity finite element (CP-FE) model for body-centered-cubic (BCC) α-Fe that incorporates non-Schmid stress dependent slip with temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effects</span>. Based on recent insights obtained from atomistic simulations, we propose a new constitutive model that combines a generalized non-Schmid yield law with aspects from a line tension (LT) model for describing activation enthalpy required for the motion of dislocation kinks. Atomistic calculations are conducted to quantify the non-Schmid <span class="hlt">effects</span> while both experimental data and atomistic simulations are used to assess the temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effects</span>. The parameterized constitutive equationmore » is implemented into a BCC CP-FE model to simulate plastic deformation of single and polycrystalline Fe which is compared with experimental data from the literature. This direct comparison demonstrates that the atomistically informed model accurately captures the <span class="hlt">effects</span> of crystal orientation, temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> on the flow behavior of siangle crystal Fe. Furthermore, our proposed CP-FE model exhibits temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> dependent flow and yield surfaces in polycrystalline Fe that deviate from conventional CP-FE models based on Schmid's law.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030033924','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030033924"><span id="translatedtitle">Study of High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Response of Composites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gilat, Amos</p> <p>2003-01-01</p> <p>The objective of the research was to continue the experimental study of the <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> on mechanical response (deformation and failure) of epoxy resins and carbon fibers/epoxy matrix composites, and to initiate a study of the <span class="hlt">effects</span> of temperature by developing an elevated temperature test. The experimental data provide the information needed for NASA scientists for the development of a nonlinear, <span class="hlt">rate</span> dependent deformation and strength models for composites that can subsequently be used in design. This year effort was directed into testing the epoxy resin. Three types of epoxy resins were tested in tension and shear at various <span class="hlt">strain</span> <span class="hlt">rates</span> that ranges from 5 x 10(exp -5), to 1000 per second. Pilot shear experiments were done at high <span class="hlt">strain</span> <span class="hlt">rate</span> and an elevated temperature of 80 C. The results show that all, the <span class="hlt">strain</span> <span class="hlt">rate</span>, the mode of loading, and temperature significantly affect the response of epoxy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880012129','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880012129"><span id="translatedtitle">Controlled-<span class="hlt">strain</span> <span class="hlt">rate</span> tests at very low <span class="hlt">strain</span> <span class="hlt">rates</span> of 2618 aluminum at 200 C</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ding, J. L.; Lee, S. R.</p> <p>1988-01-01</p> <p>Constant <span class="hlt">strain</span> <span class="hlt">rate</span> tests and constant load creep tests were performed on 2618 aluminum at 200 C. The <span class="hlt">strain</span> <span class="hlt">rates</span> used in the constant <span class="hlt">strain</span> <span class="hlt">rate</span> tests were 10 to the minus 6, 10 to the minus 7, 10 to the minum 8, and 10 to the minus 9/sec. Due to the fact that the <span class="hlt">strain</span> <span class="hlt">rates</span> in both tests were comparable to each other, the similarities between them can therefore be studied. It was concluded that metals are essentially <span class="hlt">rate</span> sensitive at elevated temperatures. The traditional definition of creep and plasticity used in the classical creep analysis is actually a reflection of the material behavior under different loading conditions. A constitutive equation based on the test data under one loading condition should work well for other loading conditions as long as the <span class="hlt">strain</span> <span class="hlt">rates</span> are in the same range as those under which the material constants are determined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20060008701','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20060008701"><span id="translatedtitle">High-<span class="hlt">Strain-Rate</span> Compression Testing of Ice</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Shazly, Mostafa; Prakash, Vikas; Lerch, Bradley A.</p> <p>2006-01-01</p> <p>In the present study a modified split Hopkinson pressure bar (SHPB) was employed to study the <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> on the dynamic material response of ice. Disk-shaped ice specimens with flat, parallel end faces were either provided by Dartmouth College (Hanover, NH) or grown at Case Western Reserve University (Cleveland, OH). The SHPB was adapted to perform tests at high <span class="hlt">strain</span> <span class="hlt">rates</span> in the range 60 to 1400/s at test temperatures of -10 and -30 C. Experimental results showed that the strength of ice increases with increasing <span class="hlt">strain</span> <span class="hlt">rates</span> and this occurs over a change in <span class="hlt">strain</span> <span class="hlt">rate</span> of five orders of magnitude. Under these <span class="hlt">strain</span> <span class="hlt">rate</span> conditions the ice microstructure has a slight influence on the strength, but it is much less than the influence it has under quasi-static loading conditions. End constraint and frictional <span class="hlt">effects</span> do not influence the compression tests like they do at slower <span class="hlt">strain</span> <span class="hlt">rates</span>, and therefore the diameter/thickness ratio of the samples is not as critical. The strength of ice at high <span class="hlt">strain</span> <span class="hlt">rates</span> was found to increase with decreasing test temperatures. Ice has been identified as a potential source of debris to impact the shuttle; data presented in this report can be used to validate and/or develop material models for ice impact analyses for shuttle Return to Flight efforts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26096628','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26096628"><span id="translatedtitle">The <span class="hlt">effect</span> of time step, thermostat, and <span class="hlt">strain</span> <span class="hlt">rate</span> on ReaxFF simulations of mechanical failure in diamond, graphene, and carbon nanotube.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jensen, Benjamin D; Wise, Kristopher E; Odegard, Gregory M</p> <p>2015-08-05</p> <p>As the sophistication of reactive force fields for molecular modeling continues to increase, their use and applicability has also expanded, sometimes beyond the scope of their original development. Reax Force Field (ReaxFF), for example, was originally developed to model chemical reactions, but is a promising candidate for modeling fracture because of its ability to treat covalent bond cleavage. Performing reliable simulations of a complex process like fracture, however, requires an understanding of the <span class="hlt">effects</span> that various modeling parameters have on the behavior of the system. This work assesses the <span class="hlt">effects</span> of time step size, thermostat algorithm and coupling coefficient, and <span class="hlt">strain</span> <span class="hlt">rate</span> on the fracture behavior of three carbon-based materials: graphene, diamond, and a carbon nanotube. It is determined that the simulated stress-<span class="hlt">strain</span> behavior is relatively independent of the thermostat algorithm, so long as coupling coefficients are kept above a certain threshold. Likewise, the stress-<span class="hlt">strain</span> response of the materials was also independent of the <span class="hlt">strain</span> <span class="hlt">rate</span>, if it is kept below a maximum <span class="hlt">strain</span> <span class="hlt">rate</span>. Finally, the mechanical properties of the materials predicted by the Chenoweth C/H/O parameterization for ReaxFF are compared with literature values. Some deficiencies in the Chenoweth C/H/O parameterization for predicting mechanical properties of carbon materials are observed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005PhRvB..71h5411J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005PhRvB..71h5411J"><span id="translatedtitle"><span class="hlt">Effects</span> of temperature, <span class="hlt">strain</span> <span class="hlt">rate</span>, and vacancies on tensile and fatigue behaviors of silicon-based nanotubes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jeng, Yeau-Ren; Tsai, Ping-Chi; Fang, Te-Hua</p> <p>2005-02-01</p> <p>This paper adopts the Tersoff-Brenner many-body potential function to perform molecular dynamics simulations of the tensile and fatigue behaviors of hypothetical silicon-based tubular nanostructures at various temperatures, <span class="hlt">strain</span> <span class="hlt">rates</span>, and vacancy percentages. The tensile test results indicate that with a predicted Young’s modulus of approximately 60GPa , silicon nanotubes (SiNTs) are significantly less stiff than conventional carbon nanotubes. It is observed that the presence of hydrogen has a significant influence on the tensile strength of SiNTs . Additionally, the present results indicate that the tensile strength clearly decreases with increasing temperature and with decreasing <span class="hlt">strain</span> <span class="hlt">rate</span>. Moreover, it is shown that the majority of the mechanical properties considered in the present study decrease with an increasing vacancy percentage. Regarding the fatigue tests, this study uses a standard theoretical model to derive curves of amplitude stress versus number of cycles for the current nanotubes. The results demonstrate that the fatigue limit of SiNTs increases with a decreasing vacancy percentage and with increasing temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880000040&hterms=hygroscopic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dhygroscopic','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880000040&hterms=hygroscopic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dhygroscopic"><span id="translatedtitle"><span class="hlt">Strain</span>-Energy-Release <span class="hlt">Rates</span> In Delamination</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Raju, I. S.</p> <p>1988-01-01</p> <p>Q3DG computer program developed to perform quasi-three-dimensional stress analysis of composite laminates containing delaminations. Calculates <span class="hlt">strain</span>-energy-release <span class="hlt">rates</span> for long, rectangular composite laminates containing delaminations and subjected to any combination of mechanical, thermal, and hygroscopic loading. Written in FORTRAN V.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010074019','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010074019"><span id="translatedtitle">Suppression of Low <span class="hlt">Strain</span> <span class="hlt">Rate</span> Nonpremixed Flames by an Agent</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hamins, A.; Bundy, M.; Puri, I. K.; McGrattan, K.; Park, W. C.</p> <p>2001-01-01</p> <p>The agent concentration required to achieve the suppression of low <span class="hlt">strain</span> <span class="hlt">rate</span> nonpremixed flames is an important consideration for fire protection in a microgravity environment such as a space platform. Currently, there is a lack of understanding of the structure and extinction of low <span class="hlt">strain</span> <span class="hlt">rate</span> (<20 s(exp -1)) nonpremixed flames. The exception to this statement is the study by Maruta et al., who reported measurements of low <span class="hlt">strain</span> <span class="hlt">rate</span> suppression of methane-air diffusion flames with N2 added to the fuel stream under microgravity conditions. They found that the nitrogen concentration required to achieve extinction increased as the <span class="hlt">strain</span> <span class="hlt">rate</span> decreased until a critical value was obtained. As the <span class="hlt">strain</span> <span class="hlt">rate</span> was further decreased, the required N2 concentration decreased. This phenomenon was termed "turning point" behavior and was attributed to radiation-induced nonpremixed flame extinction. In terms of fire safety, a critical agent concentration assuring suppression under all flow conditions represents a fundamental limit for nonpremixed flames. Counterflow flames are a convenient configuration for control of the flame <span class="hlt">strain</span> <span class="hlt">rate</span>. In high and moderately <span class="hlt">strained</span> near-extinction nonpremixed flames, analysis of flame structure typically neglects radiant energy loss because the flames are nonluminous and the hot gas species are confined to a thin reaction zone. In counterflowing CH4-air flames, for example, radiative heat loss fractions ranging from 1 to 6 percent have been predicted and measured. The objective of this study is to investigate the impact of radiative emission, flame <span class="hlt">strain</span>, agent addition, and buoyancy on the structure and extinction of low <span class="hlt">strain</span> <span class="hlt">rate</span> nonpremixed flames through measurements and comparison with flame simulations. The suppression <span class="hlt">effectiveness</span> of a number of suppressants (N2, CO2, or CF3Br) was considered as they were added to either the fuel or oxidizer streams of low <span class="hlt">strain</span> <span class="hlt">rate</span> methane-air diffusion flames.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active"><span>6</span></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_6 --> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JAP...118l3904D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JAP...118l3904D"><span id="translatedtitle">High <span class="hlt">strain-rate</span> magnetoelasticity in Galfenol</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Domann, J. P.; Loeffler, C. M.; Martin, B. E.; Carman, G. P.</p> <p>2015-09-01</p> <p>This paper presents the experimental measurements of a highly magnetoelastic material (Galfenol) under impact loading. A Split-Hopkinson Pressure Bar was used to generate compressive stress up to 275 MPa at <span class="hlt">strain</span> <span class="hlt">rates</span> of either 20/s or 33/s while measuring the stress-<span class="hlt">strain</span> response and change in magnetic flux density due to magnetoelastic coupling. The average Young's modulus (44.85 GPa) was invariant to <span class="hlt">strain</span> <span class="hlt">rate</span>, with instantaneous stiffness ranging from 25 to 55 GPa. A lumped parameters model simulated the measured pickup coil voltages in response to an applied stress pulse. Fitting the model to the experimental data provided the average piezomagnetic coefficient and relative permeability as functions of field strength. The model suggests magnetoelastic coupling is primarily insensitive to <span class="hlt">strain</span> <span class="hlt">rates</span> as high as 33/s. Additionally, the lumped parameters model was used to investigate magnetoelastic transducers as potential pulsed power sources. Results show that Galfenol can generate large quantities of instantaneous power (80 MW/m3 ), comparable to explosively driven ferromagnetic pulse generators (500 MW/m3 ). However, this process is much more efficient and can be cyclically carried out in the linear elastic range of the material, in stark contrast with explosively driven pulsed power generators.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10193638','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10193638"><span id="translatedtitle">Deformation twinning: Influence of <span class="hlt">strain</span> <span class="hlt">rate</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gray, G.T. III</p> <p>1993-11-01</p> <p>Twins in most crystal structures, including advanced materials such as intermetallics, form more readily as the temperature of deformation is decreased or the <span class="hlt">rate</span> of deformation is increased. Both parameters lead to the suppression of thermally-activated dislocation processes which can result in stresses high enough to nucleate and grow deformation twins. Under high-<span class="hlt">strain</span> <span class="hlt">rate</span> or shock-loading/impact conditions deformation twinning is observed to be promoted even in high stacking fault energy FCC metals and alloys, composites, and ordered intermetallics which normally do not readily deform via twinning. Under such conditions and in particular under the extreme loading <span class="hlt">rates</span> typical of shock wave deformation the competition between slip and deformation twinning can be examined in detail. In this paper, examples of deformation twinning in the intermetallics TiAl, Ti-48Al-lV and Ni{sub 3}A as well in the cermet Al-B{sub 4}C as a function of <span class="hlt">strain</span> <span class="hlt">rate</span> will be presented. Discussion includes: (1) the microstructural and experimental variables influencing twin formation in these systems and twinning topics related to high-<span class="hlt">strain-rate</span> loading, (2) the high velocity of twin formation, and (3) the influence of deformation twinning on the constitutive response of advanced materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1236557','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1236557"><span id="translatedtitle">Material mechanical characterization method for multiple <span class="hlt">strains</span> and <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Erdmand, III, Donald L.; Kunc, Vlastimil; Simunovic, Srdjan; Wang, Yanli</p> <p>2016-01-19</p> <p>A specimen for measuring a material under multiple <span class="hlt">strains</span> and <span class="hlt">strain</span> <span class="hlt">rates</span>. The specimen including a body having first and second ends and a gage region disposed between the first and second ends, wherein the body has a central, longitudinal axis passing through the first and second ends. The gage region includes a first gage section and a second gage section, wherein the first gage section defines a first cross-sectional area that is defined by a first plane that extends through the first gage section and is perpendicular to the central, longitudinal axis. The second gage section defines a second cross-sectional area that is defined by a second plane that extends through the second gage section and is perpendicular to the central, longitudinal axis and wherein the first cross-sectional area is different in size than the second cross-sectional area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDE20006M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDE20006M"><span id="translatedtitle">Stretching Behavior of Red Blood Cells at High <span class="hlt">Strain</span> <span class="hlt">Rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mancuso, Jordan; Ristenpart, William</p> <p>2016-11-01</p> <p>Most work on the mechanical behavior of red blood cells (RBCs) has focused on simple shear flows. Relatively little work has examined RBC deformations in the physiologically important extensional flow that occurs at the entrance to a constriction. In particular, previous work suggests that RBCs rapidly stretch out and then retract upon entering the constriction, but to date no model predicts this behavior for the extremely high <span class="hlt">strain</span> <span class="hlt">rates</span> typically experienced there. In this work, we use high speed video to perform systematic measurements of the dynamic stretching behavior of RBCs as they enter a microfluidic constriction. We demonstrate that a simple viscoelastic model captures the observed stretching dynamics, up to <span class="hlt">strain</span> <span class="hlt">rates</span> as high as 1000 s-1. The results indicate that the <span class="hlt">effective</span> elastic modulus of the RBC membrane at these <span class="hlt">strain</span> <span class="hlt">rates</span> is an order of magnitude larger than moduli measured by micropipette aspiration or other low <span class="hlt">strain</span> <span class="hlt">rate</span> techniques.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/82645','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/82645"><span id="translatedtitle">On certain aspects of <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity of sheet metals</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Shi, M.F.; Meuleman, D.J.</p> <p>1995-06-01</p> <p>The formability of a material depends upon the <span class="hlt">strain</span> hardening and <span class="hlt">strain</span> <span class="hlt">rate</span> hardening of the material. In this study, constitutive parameters using the power law constitutive equation are determined for six different strength steels and two aluminum alloys over different <span class="hlt">strain</span> ranges, including approximations of the postuniform elongation range. Constitutive parameters are found to be different at different <span class="hlt">strain</span> ranges. The <span class="hlt">strain</span> hardening of steels increases with <span class="hlt">strain</span> at low <span class="hlt">strain</span> levels (less than 5%) and decreases at high <span class="hlt">strain</span> levels (greater than 10%). <span class="hlt">Strain</span> <span class="hlt">rate</span> hardening decreases with <span class="hlt">strain</span> for all steels and aluminum alloys. Uniform elongation depends only on <span class="hlt">strain</span> hardening, and postuniform elongation depends only on <span class="hlt">strain</span> <span class="hlt">rate</span> hardening. However, the total elongation depends on both <span class="hlt">strain</span> hardening and <span class="hlt">strain</span> <span class="hlt">rate</span> hardening.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRB..121.4523S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRB..121.4523S"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> dependency of oceanic intraplate earthquake b-values at extremely low <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sasajima, Ryohei; Ito, Takeo</p> <p>2016-06-01</p> <p>We discovered a clear positive dependence of oceanic intraplate earthquake (OCEQ) b-values on the age of the oceanic lithosphere. OCEQ b-values in the youngest (<10 Ma) oceanic lithosphere are around 1.0, while those in middle to old (>20 Ma) oceanic lithosphere exceed 1.5, which is significantly higher than the average worldwide earthquake b-value (around 1.0). On the other hand, the b-value of intraplate earthquakes in the Ninety East-Sumatra orogen, where oceanic lithosphere has an anomalously higher <span class="hlt">strain</span> <span class="hlt">rate</span> compared with normal oceanic lithosphere, is 0.93, which is significantly lower than the OCEQ b-value (about 1.9) with the same age (50-110 Ma). Thus, the variation in b-values relates to the <span class="hlt">strain</span> <span class="hlt">rate</span> of the oceanic lithosphere and is not caused by a difference in thermal structure. We revealed a negative <span class="hlt">strain</span> <span class="hlt">rate</span> dependency of the b-value at extremely low <span class="hlt">strain</span> <span class="hlt">rates</span> (<2 × 10-10/year), which can clearly explain the above b-values. We propose that the OCEQ b-value depends strongly on <span class="hlt">strain</span> <span class="hlt">rate</span> (either directly or indirectly) at extremely low <span class="hlt">strain</span> <span class="hlt">rates</span>. The high OCEQ b-values (>1.5) in oceanic lithosphere >20 Ma old imply that future improvement in seismic observation will capture many smaller magnitude OCEQs, which will provide valuable information on the evolution of the oceanic lithosphere and the driving mechanism of plate tectonics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SPIE.9040E..15Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SPIE.9040E..15Y"><span id="translatedtitle">A new radial <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> estimation method using autocorrelation for carotid artery</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ye, Jihui; Kim, Hoonmin; Park, Jongho; Yeo, Sunmi; Shim, Hwan; Lim, Hyungjoon; Yoo, Yangmo</p> <p>2014-03-01</p> <p>Atherosclerosis is a leading cause of cardiovascular disease. The early diagnosis of atherosclerosis is of clinical interest since it can prevent any adverse <span class="hlt">effects</span> of atherosclerotic vascular diseases. In this paper, a new carotid artery radial <span class="hlt">strain</span> estimation method based on autocorrelation is presented. In the proposed method, the <span class="hlt">strain</span> is first estimated by the autocorrelation of two complex signals from the consecutive frames. Then, the angular phase from autocorrelation is converted to <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> and they are analyzed over time. In addition, a 2D <span class="hlt">strain</span> image over region of interest in a carotid artery can be displayed. To evaluate the feasibility of the proposed radial <span class="hlt">strain</span> estimation method, radiofrequency (RF) data of 408 frames in the carotid artery of a volunteer were acquired by a commercial ultrasound system equipped with a research package (V10, Samsung Medison, Korea) by using a L5-13IS linear array transducer. From in vivo carotid artery data, the mean <span class="hlt">strain</span> estimate was -0.1372 while its minimum and maximum values were -2.961 and 0.909, respectively. Moreover, the overall <span class="hlt">strain</span> estimates are highly correlated with the reconstructed M-mode trace. Similar results were obtained from the estimation of the <span class="hlt">strain</span> <span class="hlt">rate</span> change over time. These results indicate that the proposed carotid artery radial <span class="hlt">strain</span> estimation method is useful for assessing the arterial wall's stiffness noninvasively without increasing the computational complexity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/305920','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/305920"><span id="translatedtitle">The influence of <span class="hlt">strain</span> <span class="hlt">rate</span> and hydrogen on the plane-<span class="hlt">strain</span> ductility of Zircaloy cladding</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Link, T.M.; Motta, A.T.; Koss, D.A.</p> <p>1998-03-01</p> <p>The authors studied the ductility of unirradiated Zircaloy-4 cladding under loading conditions prototypical of those found in reactivity-initiated accidents (RIA), i.e.: near plane-<span class="hlt">strain</span> deformation in the hoop direction (transverse to the cladding axis) at room temperature and 300 C and high <span class="hlt">strain</span> <span class="hlt">rates</span>. To conduct these studies, they developed a specimen configuration in which near plane-<span class="hlt">strain</span> deformation is achieved in the gage section, and a testing methodology that allows one to determine both the limit <span class="hlt">strain</span> at the onset of localized necking and the fracture <span class="hlt">strain</span>. The experiments indicate that there is little <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> (10{sup {minus}3} to 10{sup 2} s{sup {minus}1}) on the ductility of unhydrided Zircaloy tubing deformed under near plane-<span class="hlt">strain</span> conditions at either room temperature or 300 C. Preliminary experiments on cladding containing 190 ppm hydrogen show only a small loss of fracture <span class="hlt">strain</span> but no clear <span class="hlt">effect</span> on limit <span class="hlt">strain</span>. The experiments also indicate that there is a significant loss of Zircaloy ductility when surface flaws are present in the form of thickness imperfections.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhyE...85...97L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhyE...85...97L"><span id="translatedtitle">The <span class="hlt">effect</span> of temperature, defect and <span class="hlt">strain</span> <span class="hlt">rate</span> on the mechanical property of multi-layer graphene: Coarse-grained molecular dynamics study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Hui; Zhang, Hong; Cheng, Xinlu</p> <p>2017-01-01</p> <p>In this work, we investigate the <span class="hlt">effect</span> of temperature, defect, and <span class="hlt">strain</span> <span class="hlt">rate</span> on the mechanical properties of multi-layer graphene using coarse-grained molecular dynamics (CGMD) simulations. The simulation results reveal that the mechanical properties of multi-layer graphene tend to be less sensitive to temperature as the layer increases, but they are sensitive to the distribution and coverage of Stone-Wales (SW) defects. For the same number of defect, there is less decline in the fracture stress and Young's modulus of graphene when the defects have a regular distribution, in contrast to random distribution. In addition, Young's modulus is less influenced by temperature and defect, compared to fracture stress. Both the fracture stress and Young's modulus have little dependence on <span class="hlt">strain</span> <span class="hlt">rate</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA212089','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA212089"><span id="translatedtitle">The <span class="hlt">Effects</span> of High <span class="hlt">Strain</span> <span class="hlt">Rate</span> and High Frequency Loading on Soil Behavior in Centrifuge Model Tests</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1989-07-01</p> <p>Laidler and Eyring, 1941). The basis of <span class="hlt">rate</span> process theory is that atoms, molecules and/or particles participating in a time dependent flow or...on the basis that interlocking between particles becomes more <span class="hlt">effective</span> when the particles are not given sufficient time to find the easiest path...Figure 31. Effecs of yield accelaration and damping on the relaton between elastic natural frequency and the predicted displacement for model</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.G43B0920K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.G43B0920K"><span id="translatedtitle">A New Global Geodetic <span class="hlt">Strain</span> <span class="hlt">Rate</span> Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kreemer, C. W.; Klein, E. C.; Blewitt, G.; Shen, Z.; Wang, M.; Chamot-Rooke, N. R.; Rabaute, A.</p> <p>2012-12-01</p> <p>As part of the Global Earthquake Model (GEM) effort to improve global seismic hazard models, we present a new global geodetic <span class="hlt">strain</span> <span class="hlt">rate</span> model. This model (GSRM v. 2) is a vast improvement on the previous model from 2004 (v. 1.2). The model is still based on a finite-element type approach and has deforming cells in between the assumed rigid plates. While v.1.2 contained ~25,000 deforming cells of 0.6° by 0.5° dimension, the new models contains >136,000 cells of 0.25° by 0.2° dimension. We redefined the geometries of the deforming zones based on the definitions of Bird (2003) and Chamot-Rooke and Rabaute (2006). We made some adjustments to the grid geometry at places where seismicity and/or GPS velocities suggested the presence of deforming areas where those previous studies did not. As a result, some plates/blocks identified by Bird (2003) we assumed to deform, and the total number of plates and blocks in GSRM v.2 is 38 (including the Bering block, which Bird (2003) did not consider). GSRM v.1.2 was based on ~5,200 GPS velocities, taken from 86 studies. The new model is based on ~17,000 GPS velocities, taken from 170 studies. The GPS velocity field consists of a 1) ~4900 velocities derived by us for CPS stations publicly available RINEX data and >3.5 years of data, 2) ~1200 velocities for China from a new analysis of all CMONOC data, and 3) velocities published in the literature or made otherwise available to us. All studies were combined into the same reference frame by a 6-parameter transformation using velocities at collocated stations. Because the goal of the project is to model the interseismic <span class="hlt">strain</span> <span class="hlt">rate</span> field, we model co-seismic jumps while estimating velocities, ignore periods of post-seismic deformation, and exclude time-series that reflect magmatic and anthropogenic activity. GPS velocities were used to estimate angular velocities for most of the 38 rigid plates and blocks (the rest being taken from the literature), and these were used as boundary</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJWC..9402019C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9402019C"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> dependency of laser sintered polyamide 12</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cook, J. E. T.; Goodridge, R. D.; Siviour, C. R.</p> <p>2015-09-01</p> <p>Parts processed by Additive Manufacturing can now be found across a wide range of applications, such as those in the aerospace and automotive industry in which the mechanical response must be optimised. Many of these applications are subjected to high <span class="hlt">rate</span> or impact loading, yet it is believed that there is no prior research on the <span class="hlt">strain</span> <span class="hlt">rate</span> dependence in these materials. This research investigates the <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> and laser energy density on laser sintered polyamide 12. In the study presented here, parts produced using four different laser sintered energy densities were exposed to uniaxial compression tests at <span class="hlt">strain</span> <span class="hlt">rates</span> ranging from 10-3 to 10+3 s-1 at room temperature, and the dependence on these parameters is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050215165','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050215165"><span id="translatedtitle">Associative Flow Rule Used to Include Hydrostatic Stress <span class="hlt">Effects</span> in Analysis of <span class="hlt">Strain-Rate</span>-Dependent Deformation of Polymer Matrix Composites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldberg, Robert K.; Roberts, Gary D.</p> <p>2004-01-01</p> <p>designing reliable composite engine cases that are lighter than the metal cases in current use. The types of polymer matrix composites that are likely to be used in such an application have a deformation response that is nonlinear and that varies with <span class="hlt">strain</span> <span class="hlt">rate</span>. The nonlinearity and the <span class="hlt">strain-rate</span> dependence of the composite response are due primarily to the matrix constituent. Therefore, in developing material models to be used in the design of impact-resistant composite engine cases, the deformation of the polymer matrix must be correctly analyzed. However, unlike in metals, the nonlinear response of polymers depends on the hydrostatic stresses, which must be accounted for within an analytical model. By applying micromechanics techniques along with given fiber properties, one can also determine the <span class="hlt">effects</span> of the hydrostatic stresses in the polymer on the overall composite deformation response. First efforts to account for the hydrostatic stress <span class="hlt">effects</span> in the composite deformation applied purely empirical methods that relied on composite-level data. In later efforts, to allow polymer properties to be characterized solely on the basis of polymer data, researchers at the NASA Glenn Research Center developed equations to model the polymers that were based on a non-associative flow rule, and efforts to use these equations to simulate the deformation of representative polymer materials were reasonably successful. However, these equations were found to have difficulty in correctly analyzing the multiaxial stress states found in the polymer matrix constituent of a composite material. To correct these difficulties, and to allow for the accurate simulation of the nonlinear <span class="hlt">strain-rate</span>-dependent deformation analysis of polymer matrix composites, in the efforts reported here Glenn researchers reformulated the polymer constitutive equations from basic principles using the concept of an associative flow rule. These revised equations were characterized and validated in an</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811277H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811277H"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> and stress field in Switzerland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Houlié, Nicolas; Woessner, Jochen; Giardini, Domenico; Rothacher, Markus</p> <p>2016-04-01</p> <p>In this study we test whether the surface deformation and the seismic activity are in agreement in terms of seismic moment release and stress/<span class="hlt">strain</span> orientations within the territory of Switzerland. We find that for most of the country, the stress released (~2.0 10E11 N·m/yr) is consistent with the lithosphere deformation (<5 10E-8 /yr) constrained using the Global Positioning System (GPS). South of the Alpine front, we note that surface <span class="hlt">strain</span> <span class="hlt">rates</span> displays few agreement with long-term (and deep) deformation of the upper mantle. In this area, we propose that shear <span class="hlt">strain</span> is being distributed in the upper crust as a result of the clockwise rotation of the Adria plate. For three regions (Basel, Swiss Jura and Ticino), we find that seismic current activity and surface deformation not to be in agreement. In the Basel area, deep seismicity exists while surface deformation is absent. This situation contrasts to what is found in the Ticino and the Swiss Jura, where seismic activity is close to absent but surface deformation is detected (~2 10E-8 /yr). While the surface deformation and seismic activity is inconsistent for the Ticino, we find them to comply in the Valais region where MW≥6 events are historically documented. Our comparison implies that the Ticino faces the potential of damaging earthquakes every hundred to few hundred years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6641398','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6641398"><span id="translatedtitle"><span class="hlt">Effect</span> of <span class="hlt">strain</span> <span class="hlt">rates</span> from 10/sup -2/ to 10 sec/sup -1/ in triaxial compression tests on three rocks</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Blanton, T.L.</p> <p>1981-02-01</p> <p>Room-temperature, compression tests at <span class="hlt">strain</span> <span class="hlt">rates</span> from 10/sup -2/ to 10 sec/sup -1/ have been run on Charcoal Granodiorite to 0.45 GPa confining pressure and on Berea Sandstone and Indiana Limestone to 0.25 GPa confining pressure. For each rock at each confining pressure, the differential stress at failure is relatively constant up to a <span class="hlt">strain</span> <span class="hlt">rate</span> of 1 sec/sup -1/ and apparently increases abruptly above this <span class="hlt">strain</span> <span class="hlt">rate</span>. Dynamic analysis of the testing apparatus indicates that the apparent sudden increase in strength is due to machine inertia and does not reflect a real increase in the strength of the rocks. Taking inertia into account, the actual failure stresses of the three rocks are relatively independent of <span class="hlt">strain</span> <span class="hlt">rate</span> betweeen 10/sup -2/ and 10 sec/sup -1/. In the same interval, the <span class="hlt">strains</span> at which the unconfined rocks begin to fragment tend to be lower at higher <span class="hlt">strain</span> <span class="hlt">rates</span>. The combination of decreasing <span class="hlt">strains</span> and relatively constant stresses with increasing <span class="hlt">strain</span> <span class="hlt">rate</span> suggests that the energy necessary to fragment the unconfined rocks is lower at higher <span class="hlt">strain</span> <span class="hlt">rates</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16600072','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16600072"><span id="translatedtitle">The electrocardiogram of the Beagle dog: reference values and <span class="hlt">effect</span> of sex, genetic <span class="hlt">strain</span>, body position and heart <span class="hlt">rate</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hanton, G; Rabemampianina, Y</p> <p>2006-04-01</p> <p>The aim of the study was to establish a database for electrocardiographic parameters of Beagle dogs used for toxicological studies and to evaluate the influence of supplier, sex, heart <span class="hlt">rate</span> (HR) and body position for electrocardiogram (ECG) recording on ECG parameters. Peripheral ECG leads were recorded from 934 female and 946 male dogs from Marshall Farms and 27 females and 30 males from Harlan, either standing on a table or restrained in a hammock. HR, RR, PQ and QT intervals, P and QRS duration and P-wave amplitude were measured. There were no major differences between sexes for ECG parameters. The axis of the heart was shifted to the left when the animals were restrained in a hammock compared to when they were standing on a table. The PQ interval was higher (about 9%) in Harlan than in Marshall dogs. HR was negatively correlated with QT (coefficient of linear correlation: r=-0.61 to -0.74), which emphasizes the need for a formula correcting QT interval for HR when interpreting changes in QT interval. HR was also negatively correlated with PQ intervals (r=-0.26 to -0.11), whereas a positive correlation was found between HR and the amplitude of the P wave (r=0.21-0.34). The level of the respiratory sinus arrhythmia (SA) was quantified by calculating the ratio of maximum to minimum RR interval measured over a 10 s period. This ratio was negatively correlated with HR (r =-0.49 to -0.33). Therefore, at high HRs, SA was less marked than at low HRs, but it did not completely disappear. Analysis of beat-to-beat variation indicated that QT and PQ intervals and the amplitude of P wave fluctuated over time and the degree of this variability was positively correlated with the level of SA. In conclusion, we have established reference values for the duration and/or amplitude of some ECG parameters both in terms of means and variability over the recording period, and we have evaluated the influence of body position, genetic <span class="hlt">strain</span> and HR on the ECG parameters. These data can</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.S13B2817K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.S13B2817K"><span id="translatedtitle">Analysis of Changing Swarm <span class="hlt">Rate</span> using Volumetric <span class="hlt">Strain</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kumazawa, T.; Ogata, Y.; Kimura, K.; Maeda, K.; Kobayashi, A.</p> <p>2015-12-01</p> <p>Near the eastern coast of Izu peninsula is an active submarine volcanic region in Japan, where magma intrusions have been observed many times. The forecast of earthquake swarm activities and eruptions are serious concern particularly in nearby hot spring resort areas. It is well known that temporal durations of the swarm activities have been correlated with early volumetric <span class="hlt">strain</span> changes at a certain observation station of about 20 km distance apart. Therefore the Earthquake Research Committee (2010) investigated some empirical statistical relations to predict sizes of the swarm activity. Here we looked at the background seismicity <span class="hlt">rate</span> changes during these swarm periods using the non-stationary ETAS model (Kumazawa and Ogata, 2013, 2014), and have found the followings. The modified volumetric <span class="hlt">strain</span> data, by removing the <span class="hlt">effect</span> of earth tides, precipitation and coseismic jumps, have significantly higher cross-correlations to the estimated background <span class="hlt">rates</span> of the ETAS model than to the swarm <span class="hlt">rate</span>-changes. Specifically, the background seismicity <span class="hlt">rate</span> synchronizes clearer to the <span class="hlt">strain</span> change by the lags around a half day. These relations suggest an enhanced prediction of earthquakes in this region using volumetric <span class="hlt">strain</span> measurements. Hence we propose an extended ETAS model where the background <span class="hlt">rate</span> is modulated by the volumetric <span class="hlt">strain</span> data. We have also found that the response function to the <span class="hlt">strain</span> data can be well approximated by an exponential functions with the same decay <span class="hlt">rate</span>, but that their intersects are inversely proportional to the distances between the volumetric <span class="hlt">strain</span>-meter and the onset location of the swarm. Our numerical results by the same proposed model show consistent outcomes for the various major swarms in this region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1793f0029S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1793f0029S"><span id="translatedtitle">High <span class="hlt">strain</span> <span class="hlt">rate</span> characterization of polymers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Siviour, Clive R.</p> <p>2017-01-01</p> <p>This paper reviews the literature on the response of polymers to high <span class="hlt">strain</span> <span class="hlt">rate</span> deformation. The main focus is on the experimental techniques used to characterize this response. The paper includes a small number of examples as well as references to experimental data over a wide range of <span class="hlt">rates</span>, which illustrate the key features of <span class="hlt">rate</span> dependence in these materials; however this is by no means an exhaustive list. The aim of the paper is to give the reader unfamiliar with the subject an overview of the techniques available with sufficient references from which further information can be obtained. In addition to the `well established' techniques of the Hopkinson bar, Taylor Impact and Transverse impact, a discussion of the use of time-temperature superposition in interpreting and experimentally replicating high <span class="hlt">rate</span> response is given, as is a description of new techniques in which mechanical parameters are derived by directly measuring wave propagation in specimens; these are particularly appropriate for polymers with low wave speeds. The vast topic of constitutive modelling is deliberately excluded from this review.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23132014','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23132014"><span id="translatedtitle">High <span class="hlt">strain</span> <span class="hlt">rate</span> deformation of layered nanocomposites.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lee, Jae-Hwang; Veysset, David; Singer, Jonathan P; Retsch, Markus; Saini, Gagan; Pezeril, Thomas; Nelson, Keith A; Thomas, Edwin L</p> <p>2012-01-01</p> <p>Insight into the mechanical behaviour of nanomaterials under the extreme condition of very high deformation <span class="hlt">rates</span> and to very large <span class="hlt">strains</span> is needed to provide improved understanding for the development of new protective materials. Applications include protection against bullets for body armour, micrometeorites for satellites, and high-speed particle impact for jet engine turbine blades. Here we use a microscopic ballistic test to report the responses of periodic glassy-rubbery layered block-copolymer nanostructures to impact from hypervelocity micron-sized silica spheres. Entire deformation fields are experimentally visualized at an exceptionally high resolution (below 10 nm) and we discover how the microstructure dissipates the impact energy via layer kinking, layer compression, extreme chain conformational flattening, domain fragmentation and segmental mixing to form a liquid phase. Orientation-dependent experiments show that the dissipation can be enhanced by 30% by proper orientation of the layers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..MARA43002C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..MARA43002C"><span id="translatedtitle">Critical scaling with <span class="hlt">strain</span> <span class="hlt">rate</span> in overdamped sheared disordered solids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Clemmer, Joel; Salerno, Kenneth; Robbins, Mark</p> <p></p> <p>In the limit of quasistatic shear, disordered solids demonstrate non-equilibrium critical behavior including power-law distributions of avalanches. Using molecular dynamics simulations of 2D and 3D overdamped binary LJ glasses, we explore the critical behavior in the limit of finite <span class="hlt">strain</span> <span class="hlt">rate</span>. We use finite-size scaling to find the critical exponents characterizing shear stress, kinetic energy, and measures of temporal and spatial correlations. The shear stress of the system rises as a power β of the <span class="hlt">strain</span> <span class="hlt">rate</span>. Larger system size extends this power law to lower <span class="hlt">rates</span>. This behavior is governed by a power law drop of the dynamic correlation length with increasing shear stress defined by the exponent ν. This finite-size <span class="hlt">effect</span> also impacts the scaling of the RMS kinetic energy with <span class="hlt">strain</span> <span class="hlt">rate</span> as avalanches begin nucleating simultaneously leading to continuous deformation of the solid. As system size increases, avalanches begin overlapping at lower <span class="hlt">rates</span>. The correlation function of non-affine displacement exhibits novel anisotropic power law scaling with the magnitude of the wave vector. Its <span class="hlt">strain</span> <span class="hlt">rate</span> dependence is used to determine the scaling of the dynamic correlation length. Support provided by: DMR-1006805; NSF IGERT-0801471; OCI-0963185; CMMI-0923018.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active"><span>7</span></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_7 --> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA208826','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA208826"><span id="translatedtitle">High-<span class="hlt">Strain</span> <span class="hlt">Rate</span> Testing of Gun Propellants</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1988-12-01</p> <p>specimen is loaded beyond the elastic range. Instrumentation of the bars allows recording of the <span class="hlt">strain</span> history in the bars during the test event. The...<span class="hlt">strain</span> history on the input bar gives a record of the <span class="hlt">strain</span> <span class="hlt">rate</span> history in the sample. )The output bar <span class="hlt">strain</span> history is proportional to the stress... history in the sample.) The data were compared to the results reported in the literature of earlier high <span class="hlt">strain</span> <span class="hlt">rate</span> tests on the same propellants. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PMM...115.1318B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PMM...115.1318B"><span id="translatedtitle">The <span class="hlt">effects</span> of crystallographic texture and hydrogen on sulfide stress corrosion cracking behavior of a steel using slow <span class="hlt">strain</span> <span class="hlt">rate</span> test method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Baik, Youl; Choi, Yong</p> <p>2014-12-01</p> <p>The <span class="hlt">effects</span> of pre-charged hydrogen inside steel and the hydrogen ions on its surface on the sulfide stress corrosion cracking (SSCC) behavior was studied by slow <span class="hlt">strain</span> <span class="hlt">rate</span> tests. The specimen had an ASTM grain size number of about 11. Most of precipitates were 30-50 nm in size, and their distribution density was about 106 mm-2. The crystallographic texture consisted of major α-fiber (<110>//RD) components with a maximum peak at {115}<110> relatively close to {001}<110>, and minor γ-fiber (<111>//ND) components with a peak slightly shifted from {111}<112> to {332}<113>. Hydrogen was pre-charged inside the steel by a high-temperature cathodic hydrogen charging (HTCHC) method. SSCC and corrosion tests were carried out in an electrolytic solution (NaCl: CH3COOH: H2O: FeCl2 = 50: 5: 944: 1, pH = 2.7). The corrosion potentials and the corrosion <span class="hlt">rates</span> of the specimen without hydrogen charging for 24 hours were -490 mVSHE and 1.2 × 10-4 A cm-2, and those with charging were -520 mVSHE and 2.8 × 10-4 A cm-2, respectively. The corrosion resistance in the solution with 1000 ppm iron chloride added was decreased significantly, such that the corrosion potential and corrosion <span class="hlt">rate</span> were -575 mVSHE and 3.5 × 10-4 A cm-2, respectively. Lower SSCC resistance of the pin-hole pre-notched specimen was observed at the open circuit potential than at the 100 mV cathodically polarized condition. Pre-charged hydrogen inside of the specimen had a greater influence on the SSCC behavior than hydrogen ions on the surface of the specimen during the slow <span class="hlt">strain</span> <span class="hlt">rate</span> test.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA564196','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA564196"><span id="translatedtitle">High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Mechanical Properties of Glassy Polymers</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2012-07-25</p> <p>Force Materiel Command  United States Air Force  Eglin Air Force Base AFRL-RW-EG-TP-2012-008 High <span class="hlt">Strain</span> <span class="hlt">Rate</span>...TITLE AND SUBTITLE High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Mechanical Properties of Glassy Polymers 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...1990s, a range of experimental data has been generated describing the response of glassy polymers to high <span class="hlt">strain</span> <span class="hlt">rate</span> loading in compression. More</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/52821','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/52821"><span id="translatedtitle">High <span class="hlt">strain-rate</span> testing of parachute materials</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gwinn, K.W.; Totten, J.J.; Waye, D.E.</p> <p>1994-12-31</p> <p>Research at Sandia National Laboratories has shown a <span class="hlt">strain</span> <span class="hlt">rate</span> dependence of many materials used in the production of parachutes. Differences in strength of 30% have been found between <span class="hlt">strain</span> <span class="hlt">rates</span> of 12 sec{sup {minus}1} and slow <span class="hlt">rates</span> normally used to define material properties for lightweight nylon cloth. These structures are sometimes deployed in a rapid fashion and the loading is experienced in milliseconds; the production of material data in the same loading regime is required for full understanding of material response. Also, material behavior suitable for structural analysis of these structures is required for successful analysis. This is especially important when different materials are used in the same fabric structure. Determining the distribution of load to various portions of a nylon and Kevlar parachute requires the correct moduli and material behavior in the analytical model. The <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> on the material properties of nylon and Kevlar components commonly used in parachute construction are reported in this paper. These properties are suitable for use in analytical models of these fabric structures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JPhD...47P5301Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JPhD...47P5301Z"><span id="translatedtitle">Temperature and <span class="hlt">strain-rate</span> dependent fracture strength of graphynes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Ying-Yan; Pei, Qing-Xiang; Mai, Yiu-Wing; Gu, Yuan-Tong</p> <p>2014-10-01</p> <p>Graphyne is an allotrope of graphene. The mechanical properties of graphynes (α-, β-, γ- and 6,6,12-graphynes) under uniaxial tension deformation at different temperatures and <span class="hlt">strain</span> <span class="hlt">rates</span> are studied using molecular dynamics simulations. It is found that graphynes are more sensitive to temperature changes than graphene in terms of fracture strength and Young's modulus. The temperature sensitivity of the different graphynes is proportionally related to the percentage of acetylenic linkages in their structures, with the α-graphyne (having 100% of acetylenic linkages) being most sensitive to temperature. For the same graphyne, temperature exerts a more pronounced <span class="hlt">effect</span> on the Young's modulus than fracture strength, which is different from that of graphene. The mechanical properties of graphynes are also sensitive to <span class="hlt">strain</span> <span class="hlt">rate</span>, in particular at higher temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005APS..SHK.F7028A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005APS..SHK.F7028A"><span id="translatedtitle">Dynamic behaviour of birch and sequoia at high <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anatoly, Bragov; Andrey, Lomunov; Ivan, Sergeichev; Gray, George, III</p> <p>2005-07-01</p> <p>The paper presents results of experimental analysis for structural woods, i.e. birch and sequoia at high <span class="hlt">strain</span> <span class="hlt">rates</span>. Monotonic and cyclic compression testing at room temperature of these materials was performed by experimental Kolsky method, using the 20-mm diameter split Hopkinson pressure bar (SHPB). The cut out specimens were loaded along and across fibers of woods, as well as, in others angles of cutting out from wooden materials. There were obtained dynamic deformation diagrams in various above conditions for these materials. Directions of specimens' cutting out, as well as, confined conditions <span class="hlt">effect</span> on mechanical dynamic properties of the woods tested. Loading and unloading branches of stress-<span class="hlt">strain</span> diagrams obtained are nonlinear and <span class="hlt">strain</span> <span class="hlt">rates</span> sensitive. Post-failure behavior of woods' specimens tested results from various forms of their fracture, such cracking and spalling. Experimental stress-<span class="hlt">strain</span> curves showed significant influence of cutting out angles of specimens on fracture stresses' values. Dynamic deformation diagrams at cyclic loading, obtained by original modification of SPHB, are also presented for tested materials. Alongside with the SHPB tests, plane-wave experiments were conducted and the shock adiabates for the wood samples were obtained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/330609','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/330609"><span id="translatedtitle"><span class="hlt">Effect</span> of irradiation temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> on the mechanical properties of V-4Cr-4Ti irradiated to low doses in fission reactors</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zinkle, S.J.; Snead, L.L.; Rowcliffe, A.F.; Alexander, D.J.; Gibson, L.T.</p> <p>1998-09-01</p> <p>Tensile tests performed on irradiated V-(3-6%)Cr-(3-6%)Ti alloys indicate that pronounced hardening and loss of <span class="hlt">strain</span> hardening capacity occurs for doses of 0.1--20 dpa at irradiation temperatures below {approximately}330 C. The amount of radiation hardening decreases rapidly for irradiation temperatures above 400 C, with a concomitant increase in <span class="hlt">strain</span> hardening capacity. Low-dose (0.1--0.5 dpa) irradiation shifts the dynamic <span class="hlt">strain</span> aging regime to higher temperatures and lower <span class="hlt">strain</span> <span class="hlt">rates</span> compared to unirradiated specimens. Very low fracture toughness values were observed in miniature disk compact specimens irradiated at 200--320 C to {approximately}1.5--15 dpa and tested at 200 C.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1329630','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1329630"><span id="translatedtitle">Impact of heat release on <span class="hlt">strain</span> <span class="hlt">rate</span> field in turbulent premixed Bunsen flames</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Coriton, Bruno Rene Leon; Frank, Jonathan H.</p> <p>2016-08-10</p> <p>The <span class="hlt">effects</span> of combustion on the <span class="hlt">strain</span> <span class="hlt">rate</span> field are investigated in turbulent premixed CH<sub>4</sub>/air Bunsen flames using simultaneous tomographic PIV and OH LIF measurements. Tomographic PIV provides three-dimensional velocity measurements, from which the complete <span class="hlt">strain</span> <span class="hlt">rate</span> tensor is determined. The OH LIF measurements are used to determine the position of the flame surface and the flame-normal orientation within the imaging plane. This combination of diagnostic techniques enables quantification of divergence as well as flame-normal and tangential <span class="hlt">strain</span> <span class="hlt">rates</span>, which are otherwise biased using only planar measurements. Measurements are compared in three lean-to-stoichiometric flames that have different amounts of heat release and Damköhler numbers greater than unity. The <span class="hlt">effects</span> of heat release on the principal <span class="hlt">strain</span> <span class="hlt">rates</span> and their alignment relative to the local flame normal are analyzed. The extensive <span class="hlt">strain</span> <span class="hlt">rate</span> preferentially aligns with the flame normal in the reaction zone, which has been indicated by previous studies. The strength of this alignment increases with increasing heat release and, as a result, the flame-normal <span class="hlt">strain</span> <span class="hlt">rate</span> becomes highly extensive. These <span class="hlt">effects</span> are associated with the gas expansion normal to the flame surface, which is largest for the stoichiometric flame. In the preheat zone, the compressive <span class="hlt">strain</span> <span class="hlt">rate</span> has a tendency to align with the flame normal. Away from the flame front, the flame – <span class="hlt">strain</span> <span class="hlt">rate</span> alignment is arbitrary in both the reactants and products. The flame-tangential <span class="hlt">strain</span> <span class="hlt">rate</span> is on average positive across the flame front, and therefore the turbulent <span class="hlt">strain</span> <span class="hlt">rate</span> field contributes to the enhancement of scalar gradients as in passive scalar turbulence. As a result, increases in heat release result in larger positive values of the divergence as well as flame-normal and tangential <span class="hlt">strain</span> <span class="hlt">rates</span>, the tangential <span class="hlt">strain</span> <span class="hlt">rate</span> has a weaker dependence on heat release than the flame-normal <span class="hlt">strain</span> <span class="hlt">rate</span> and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1329630-impact-heat-release-strain-rate-field-turbulent-premixed-bunsen-flames','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1329630-impact-heat-release-strain-rate-field-turbulent-premixed-bunsen-flames"><span id="translatedtitle">Impact of heat release on <span class="hlt">strain</span> <span class="hlt">rate</span> field in turbulent premixed Bunsen flames</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Coriton, Bruno Rene Leon; Frank, Jonathan H.</p> <p>2016-08-10</p> <p>The <span class="hlt">effects</span> of combustion on the <span class="hlt">strain</span> <span class="hlt">rate</span> field are investigated in turbulent premixed CH4/air Bunsen flames using simultaneous tomographic PIV and OH LIF measurements. Tomographic PIV provides three-dimensional velocity measurements, from which the complete <span class="hlt">strain</span> <span class="hlt">rate</span> tensor is determined. The OH LIF measurements are used to determine the position of the flame surface and the flame-normal orientation within the imaging plane. This combination of diagnostic techniques enables quantification of divergence as well as flame-normal and tangential <span class="hlt">strain</span> <span class="hlt">rates</span>, which are otherwise biased using only planar measurements. Measurements are compared in three lean-to-stoichiometric flames that have different amounts of heatmore » release and Damköhler numbers greater than unity. The <span class="hlt">effects</span> of heat release on the principal <span class="hlt">strain</span> <span class="hlt">rates</span> and their alignment relative to the local flame normal are analyzed. The extensive <span class="hlt">strain</span> <span class="hlt">rate</span> preferentially aligns with the flame normal in the reaction zone, which has been indicated by previous studies. The strength of this alignment increases with increasing heat release and, as a result, the flame-normal <span class="hlt">strain</span> <span class="hlt">rate</span> becomes highly extensive. These <span class="hlt">effects</span> are associated with the gas expansion normal to the flame surface, which is largest for the stoichiometric flame. In the preheat zone, the compressive <span class="hlt">strain</span> <span class="hlt">rate</span> has a tendency to align with the flame normal. Away from the flame front, the flame – <span class="hlt">strain</span> <span class="hlt">rate</span> alignment is arbitrary in both the reactants and products. The flame-tangential <span class="hlt">strain</span> <span class="hlt">rate</span> is on average positive across the flame front, and therefore the turbulent <span class="hlt">strain</span> <span class="hlt">rate</span> field contributes to the enhancement of scalar gradients as in passive scalar turbulence. As a result, increases in heat release result in larger positive values of the divergence as well as flame-normal and tangential <span class="hlt">strain</span> <span class="hlt">rates</span>, the tangential <span class="hlt">strain</span> <span class="hlt">rate</span> has a weaker dependence on heat release than the flame-normal <span class="hlt">strain</span> <span class="hlt">rate</span> and the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040112003&hterms=development+theory&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Ddevelopment%2Btheory','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040112003&hterms=development+theory&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Ddevelopment%2Btheory"><span id="translatedtitle">Implementation of Higher Order Laminate Theory Into <span class="hlt">Strain</span> <span class="hlt">Rate</span> Dependent Micromechanics Analysis of Polymer Matrix Composites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kim, Heung Soo; Zhu, Linfa; Chattopadhyay, Aditi; Goldberg, Robert K.</p> <p>2004-01-01</p> <p>A procedure has been developed to investigate the nonlinear response of composite plates under large <span class="hlt">strain</span> and high <span class="hlt">strain</span> <span class="hlt">rate</span> loading. A recently developed <span class="hlt">strain</span> dependent micromechanics model is extended to account for the shear <span class="hlt">effects</span> during impact. Four different assumptions of shear deformation <span class="hlt">effects</span> are investigated to improve the development <span class="hlt">strain</span> <span class="hlt">rate</span> dependent micromechanics model. A method to determine through the thickness <span class="hlt">strain</span> and transverse Poisson's ratio is developed. The revised micromechanics model is implemented into higher order laminate theory. Parametric studies are conducted to investigate transverse shear <span class="hlt">effects</span> during impact.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20226519','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20226519"><span id="translatedtitle">The <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> on the precision of penetration of short densely-packed microprojection array patches coated with vaccine.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Crichton, Michael L; Ansaldo, Alexander; Chen, Xianfeng; Prow, Tarl W; Fernando, Germain J P; Kendall, Mark A F</p> <p>2010-06-01</p> <p>If skin's non-linear viscoelastic properties are mechanically exploited for precise antigen placement, there is tremendous promise for improved vaccines. To achieve this, we designed a Nanopatch-densely packed micro-nanoprojections (>20,000/cm(2)) to directly deposit antigen to large numbers of epidermal Langerhans cells and dermal dendritic cells. Here, we controllably applied our Nanopatches with discrete conditions between peak <span class="hlt">strain</span> <span class="hlt">rates</span> of approximately 100 s(-1)-7000 s(-1) and quantified resulting penetration depths, delivery payloads and skin mechanics. Increasing the <span class="hlt">strain</span> <span class="hlt">rate</span> of application, we overcame key skin variability, achieving increases in both projection penetration depth (by over 50% length) and area coverage of a full array (from 50% to 100%). This delivery depth precision opens the way for more fully utilizing the skin's immune function. Furthermore, we yielded new insights on mechanical behaviour of skin, including: 1) internal skin property changes that could affect/facilitate penetration; 2) projection design to dictate penetration depth; 3) puncture mechanics of skin in this <span class="hlt">strain</span> <span class="hlt">rate</span> range. Indeed, we show delivery of a model vaccine using our tested range of <span class="hlt">strain</span> <span class="hlt">rates</span> achieved functionally relevant tunable systemic antibody generation in mice. These findings could be of great utility in extending skin strata vaccine targeting approaches to human use.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA472172','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA472172"><span id="translatedtitle">Investigation into the Combined <span class="hlt">Effects</span> of Compaction, <span class="hlt">Strain</span> <span class="hlt">Rate</span> Sensitivity, and Anisotropic Damage of a Geologic Target on the Trajectory Stability of Rigid Penetrators</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2007-05-01</p> <p>class of compressible rigid viscoplastic models were pro- posed to capture the solid -fluid transition in behavior at high <span class="hlt">strain</span> <span class="hlt">rates</span>, account for...that depending on their dynamical state, particulate ma- terials may display both solid and fluid like behavior. Since at low deformation <span class="hlt">rates</span> the...particulate systems are modeled using a solid mechanics approach. These models are gener- ally developed within the framework of plasticity theory</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10164171','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10164171"><span id="translatedtitle">High <span class="hlt">strain</span> <span class="hlt">rate</span> deformation of NiAl</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Maloy, S.A.; Gray, G.T. III; Darolia, R.</p> <p>1994-07-01</p> <p>NiAl is a potential high temperature structural material. Applications for which NiAl is being considered (such as rotating components in jet engines) requires knowledge of mechanical properties over a wide range of <span class="hlt">strain</span> <span class="hlt">rates</span>. Single crystal NiAl (stoichiometric and Ni 49.75Al 0.25Fe) has been deformed in compression along [100] at <span class="hlt">strain</span> <span class="hlt">rates</span> of 0.001, 0.1/s and 2000/s and temperatures of 76,298 and 773K. <111> slip was observed after 76K testing at a <span class="hlt">strain</span> <span class="hlt">rate</span> of 0.001/s and 298K testing at a <span class="hlt">strain</span> <span class="hlt">rate</span> of 2000/s. Kinking was observed after deformation at 298K and a <span class="hlt">strain</span> <span class="hlt">rate</span> of 0.001/s and sometimes at 298 K and a <span class="hlt">strain</span> <span class="hlt">rate</span> of 0.1/s. <span class="hlt">Strain</span> hardening <span class="hlt">rates</span> of 8200 and 4000 MPa were observed after 773 and 298K testing respectively, at a <span class="hlt">strain</span> <span class="hlt">rate</span> of 2000/s. Results are discussed in reference to resulting dislocation substructure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1170524','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1170524"><span id="translatedtitle">2014 Accomplishments-Tritium aging studies on stainless steel: Fracture toughness properties of forged stainless steels-<span class="hlt">Effect</span> of hydrogen, forging <span class="hlt">strain</span> <span class="hlt">rate</span>, and forging temperature</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Morgan, Michael J.</p> <p>2015-02-01</p> <p> stainless steel were measured for four different forging <span class="hlt">strain</span> <span class="hlt">rates</span> which and two forging temperatures. Tritium exposures have been and are being conducted on companion specimens for property measurements in the upcoming years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008IJMPB..22.1255K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008IJMPB..22.1255K"><span id="translatedtitle">Dynamic Tensile Properties of Iron and Steels for a Wide Range of <span class="hlt">Strain</span> <span class="hlt">Rates</span> and <span class="hlt">Strain</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kojima, Nobusato; Hayashi, Hiroyuki; Yamamoto, Terumi; Mimura, Koji; Tanimura, Shinji</p> <p></p> <p>The tensile stress-<span class="hlt">strain</span> curves of iron and a variety of steels, covering a wide range of strength level, over a wide <span class="hlt">strain</span> <span class="hlt">rate</span> range on the order of 10-3 ~ 103 s-1, were obtained systematically by using the Sensing Block Type High Speed Material Testing System (SBTS, Saginomiya). Through intensive analysis of these results, the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity of the flow stress for the large <span class="hlt">strain</span> region, including the viscous term at high <span class="hlt">strain</span> <span class="hlt">rates</span>, the true fracture strength and the true fracture <span class="hlt">strain</span> were cleared for the material group of the ferrous metals. These systematical data may be useful to develop a practical constitutive model for computer codes, including a fracture criterion for simulations of the dynamic behavior in crash worthiness studies and of work-pieces subjected to dynamic plastic working for a wide <span class="hlt">strain</span> <span class="hlt">rate</span> range.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/175242','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/175242"><span id="translatedtitle">Influence of <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature on the radial compression behavior of wet spruce</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Uhmeier, A.; Salmen, L.</p> <p>1995-12-31</p> <p>In this study, the influences of moisture content, density, <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature on the mechanical response of spruce compressed radially to 50% <span class="hlt">strain</span> were investigated. Regression models were obtained for the plateau stress, energy absorption, plastic <span class="hlt">strain</span> and reduction of plateau stress after the first compression. Temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> had a great influence on the mechanical behaviour of spruce. It was found that lumen water had a significant <span class="hlt">effect</span> on the deformation process at high <span class="hlt">strain</span> <span class="hlt">rates</span>. The reduction in plateau stress after one compression was about 30-55%, which might increase the collapsibility of the wood fibers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010MsT..........8P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010MsT..........8P"><span id="translatedtitle">Finite Element Modeling of the Behavior of Armor Materials Under High <span class="hlt">Strain</span> <span class="hlt">Rates</span> and Large <span class="hlt">Strains</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Polyzois, Ioannis</p> <p></p> <p> propagated outwards diagonally towards the front and back edges forming an hourglass pattern. This pattern matched the failure behavior of specimens tested experimentally, which also exhibited failure through the formation of adiabatic shear bands. Adiabatic shear bands are known to lead to a complete shear failure. Both mechanical and thermal mechanisms contribute to the formation of shear bands. However, the finite element simulations did not show the <span class="hlt">effects</span> of temperature rise within the material, a phenomenon which is known to contribute to thermal instabilities, whereby <span class="hlt">strain</span> hardening <span class="hlt">effects</span> are outweighed by thermal softening <span class="hlt">effects</span> and adiabatic shear bands begin to form. In the simulations, the purely mechanical maximum shear stress failure, nucleating from the center of the specimens, was used as an indicator of the time at which these shear bands begin to form. The time and compressive stress at the moment of thermal instability in experimental results which have shown to form adiabatic shear bands, matched closely to those at which shear failure was first observed in the simulations. Although versatile in modeling BCC behavior, the Johnson-Cook model did not show the correct stress response in face-centered cubic (FCC) metals, such as aluminum 5083, where <span class="hlt">effects</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature depend on <span class="hlt">strain</span>. Similar observations have been reported in literature. In the Johnson-Cook model, temperature, <span class="hlt">strain</span> <span class="hlt">rate</span> and <span class="hlt">strain</span>" parameters are independent of each other. To this end, a more physical-based model based on dislocation mechanics, namely the Feng and Bassim constitutive model, would be more appropriate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011NatSR...1E.148H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011NatSR...1E.148H"><span id="translatedtitle">Uncovering high-<span class="hlt">strain</span> <span class="hlt">rate</span> protection mechanism in nacre</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, Zaiwang; Li, Haoze; Pan, Zhiliang; Wei, Qiuming; Chao, Yuh J.; Li, Xiaodong</p> <p>2011-11-01</p> <p>Under high-<span class="hlt">strain-rate</span> compression (<span class="hlt">strain</span> <span class="hlt">rate</span> ~103 s-1), nacre (mother-of-pearl) exhibits surprisingly high fracture strength vis-à-vis under quasi-static loading (<span class="hlt">strain</span> <span class="hlt">rate</span> 10-3 s-1). Nevertheless, the underlying mechanism responsible for such sharply different behaviors in these two loading modes remains completely unknown. Here we report a new deformation mechanism, adopted by nacre, the best-ever natural armor material, to protect itself against predatory penetrating impacts. It involves the emission of partial dislocations and the onset of deformation twinning that operate in a well-concerted manner to contribute to the increased high-<span class="hlt">strain-rate</span> fracture strength of nacre. Our findings unveil that Mother Nature delicately uses an ingenious <span class="hlt">strain-rate</span>-dependent stiffening mechanism with a purpose to fight against foreign attacks. These findings should serve as critical design guidelines for developing engineered body armor materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22355664','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22355664"><span id="translatedtitle">Uncovering high-<span class="hlt">strain</span> <span class="hlt">rate</span> protection mechanism in nacre.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Huang, Zaiwang; Li, Haoze; Pan, Zhiliang; Wei, Qiuming; Chao, Yuh J; Li, Xiaodong</p> <p>2011-01-01</p> <p>Under high-<span class="hlt">strain-rate</span> compression (<span class="hlt">strain</span> <span class="hlt">rate</span> approximately 10(3) s(-1)), nacre (mother-of-pearl) exhibits surprisingly high fracture strength vis-à-vis under quasi-static loading (<span class="hlt">strain</span> <span class="hlt">rate</span> 10(-3) s(-1)). Nevertheless, the underlying mechanism responsible for such sharply different behaviors in these two loading modes remains completely unknown. Here we report a new deformation mechanism, adopted by nacre, the best-ever natural armor material, to protect itself against predatory penetrating impacts. It involves the emission of partial dislocations and the onset of deformation twinning that operate in a well-concerted manner to contribute to the increased high-<span class="hlt">strain-rate</span> fracture strength of nacre. Our findings unveil that Mother Nature delicately uses an ingenious <span class="hlt">strain-rate</span>-dependent stiffening mechanism with a purpose to fight against foreign attacks. These findings should serve as critical design guidelines for developing engineered body armor materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3216628','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3216628"><span id="translatedtitle">Uncovering high-<span class="hlt">strain</span> <span class="hlt">rate</span> protection mechanism in nacre</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Huang, Zaiwang; Li, Haoze; Pan, Zhiliang; Wei, Qiuming; Chao, Yuh J.; Li, Xiaodong</p> <p>2011-01-01</p> <p>Under high-<span class="hlt">strain-rate</span> compression (<span class="hlt">strain</span> <span class="hlt">rate</span> ∼103 s−1), nacre (mother-of-pearl) exhibits surprisingly high fracture strength vis-à-vis under quasi-static loading (<span class="hlt">strain</span> <span class="hlt">rate</span> 10−3 s−1). Nevertheless, the underlying mechanism responsible for such sharply different behaviors in these two loading modes remains completely unknown. Here we report a new deformation mechanism, adopted by nacre, the best-ever natural armor material, to protect itself against predatory penetrating impacts. It involves the emission of partial dislocations and the onset of deformation twinning that operate in a well-concerted manner to contribute to the increased high-<span class="hlt">strain-rate</span> fracture strength of nacre. Our findings unveil that Mother Nature delicately uses an ingenious <span class="hlt">strain-rate</span>-dependent stiffening mechanism with a purpose to fight against foreign attacks. These findings should serve as critical design guidelines for developing engineered body armor materials. PMID:22355664</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active"><span>8</span></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_8 --> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JMEP...25.2878M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JMEP...25.2878M"><span id="translatedtitle">Stress Corrosion Cracking Behavior of Interstitial Free Steel Via Slow <span class="hlt">Strain</span> <span class="hlt">Rate</span> Technique</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Murkute, Pratik; Ramkumar, J.; Mondal, K.</p> <p>2016-07-01</p> <p>An interstitial free steel is subjected to slow <span class="hlt">strain</span> <span class="hlt">rate</span> tests to investigate the stress corrosion cracking (SCC) behavior at <span class="hlt">strain</span> <span class="hlt">rates</span> ranging from 10-4 to 10-6s-1 in air and 3.5 wt.% NaCl solution. The ratios of time to failure, failure <span class="hlt">strain</span>, and ultimate tensile stress at different <span class="hlt">strain</span> <span class="hlt">rates</span> in air to that in corrosive were considered as SCC susceptibility. Serrated stress-<span class="hlt">strain</span> curve observed at lowest <span class="hlt">strain</span> <span class="hlt">rate</span> is explained by the Portevin-Le Chatelier <span class="hlt">effect</span>. Maximum susceptibility to SCC at lowest <span class="hlt">strain</span> <span class="hlt">rate</span> is attributed to the soluble γ-FeOOH in the rust analyzed by Fourier Transformed Infrared spectroscopy. Mechanism for SCC relates to the anodic dissolution forming the groove, where hydrogen embrittlement can set in and finally fracture happens due to triaxiality.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/976941','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/976941"><span id="translatedtitle">On the response of rubbers at high <span class="hlt">strain</span> <span class="hlt">rates</span>.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Niemczura, Johnathan Greenberg</p> <p>2010-02-01</p> <p>In this report, we examine the propagation of tensile waves of finite deformation in rubbers through experiments and analysis. Attention is focused on the propagation of one-dimensional dispersive and shock waves in strips of latex and nitrile rubber. Tensile wave propagation experiments were conducted at high <span class="hlt">strain-rates</span> by holding one end fixed and displacing the other end at a constant velocity. A high-speed video camera was used to monitor the motion and to determine the evolution of <span class="hlt">strain</span> and particle velocity in the rubber strips. Analysis of the response through the theory of finite waves and quantitative matching between the experimental observations and analytical predictions was used to determine an appropriate instantaneous elastic response for the rubbers. This analysis also yields the tensile shock adiabat for rubber. Dispersive waves as well as shock waves are also observed in free-retraction experiments; these are used to quantify hysteretic <span class="hlt">effects</span> in rubber.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.G43C..04M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.G43C..04M"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> and strength of the continental lithosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mazzotti, S.; Gueydan, F.</p> <p>2013-12-01</p> <p>Under the Wilson Cycle and Plate Tectonics paradigms, continents are divided between stable continental regions (SCR), which tend to remain un-deformed, and plate boundary zones (PBZ) that repeatedly accommodate deformation associated with opening and closing of tectonic plates. This long-term (> 1 Ma) perspective is reflected in short-term (< 100 a) deformation markers such as seismicity and GPS measurements, which highlight the first-order contrast in <span class="hlt">strain</span> <span class="hlt">rates</span> between SCR and PBZ. However, poor data resolution at low <span class="hlt">strain</span> <span class="hlt">rates</span> provides only rough upper limits on actual long- and short-term <span class="hlt">strain</span> and seismicity <span class="hlt">rates</span> in SCR regions, including in intraplate weak zones (paleo-PBZ) where debate is ongoing regarding short- and long-term deformation <span class="hlt">rates</span> (e.g., New Madrid seismic zone). We propose to constrain first-order continental <span class="hlt">strain</span> (and seismicity) <span class="hlt">rates</span> using lithosphere rheological models, including new <span class="hlt">strain</span>-weakening rheologies, driven by tectonic forces. We estimate average <span class="hlt">strain</span> <span class="hlt">rates</span> that satisfy near-failure equilibrium between net driving forces and lithosphere strength for cases that typify PBZ, cratons, and intraplate weak zones. Our model yields a range of <span class="hlt">strain</span> <span class="hlt">rates</span> that vary by up to six orders of magnitude between PBZ and cratons. In intraplate weak zones, structural and tectonic heritage results in significant weakening and yields <span class="hlt">strain</span> <span class="hlt">rates</span> compatible with GPS, seismicity, and geological markers. These results provide first-order constraints on long-term lithosphere strength and deformation <span class="hlt">rates</span>. In particular, we explore upper and lower bounds of possible <span class="hlt">strain</span> <span class="hlt">rates</span> in intraplate weak zones of North America, using a range of geotherm, rheology, and local stress conditions. These can be used to derived limits on seismicity <span class="hlt">rates</span> in these regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006APS..MARR42010L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006APS..MARR42010L"><span id="translatedtitle">Dynamic Strength of Metals at High Pressure and <span class="hlt">Strain</span> <span class="hlt">Rate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lorenz, Thomas</p> <p>2006-03-01</p> <p>A new approach to materials science at very high pressures and <span class="hlt">strain</span> <span class="hlt">rates</span> has been developed on the Omega laser, using a ramped plasma piston drive. A laser drives an ablative shock through a solid plastic reservoir where it unloads at the rear free surface, expands across a vacuum gap, and stagnates on the metal sample under study. This produces a gently increasing ram pressure, compressing the sample nearly isentropically. The peak pressure on the sample, diagnosed with VISAR measurements, can be varied by adjusting the laser energy and pulse length, gap size, and reservoir density, and obeys a simple scaling relation.^1 This has been demonstrated at OMEGA at pressures to 200 GPa in Al foils. In an important application, using in-flight x-ray radiography, the material strength of solid-state samples at high pressure can be inferred by measuring the reductions in the growth <span class="hlt">rates</span> (stabilization) of Rayleigh-Taylor (RT) unstable interfaces. RT instability measurements of solid of Al-6061-T6 ^2 and vanadium, at pressures of 20-100 GPa, and <span class="hlt">strain</span> <span class="hlt">rates</span> of 10^6 to 10^8 s-1, show clear material strength <span class="hlt">effects</span>. Modelling results for two constitutive strength models -- Steinberg-Guinan and Preston-Tonks-Wallace, show enhanced dynamic strength that may be correlated with a high-<span class="hlt">strain-rate</span>, phono-drag mechanism. Data, modeling details and future prospects for this project using the National Ignition Facility laser, will be presented. [1] J. Edwards et al., Phys. Rev. Lett., 92, 075002 (2004). [2] K. T. Lorenz et al., Phys. Plasmas 12, 056309 (2005). This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920011596','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920011596"><span id="translatedtitle">High <span class="hlt">strain</span> <span class="hlt">rate</span> properties of unidirectional composites, part 1</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Daniel, I. M.</p> <p>1991-01-01</p> <p>Experimental methods were developed for testing and characterization of composite materials at <span class="hlt">strain</span> <span class="hlt">rates</span> ranging from quasi-static to over 500 s(sup -1). Three materials were characterized, two graphite/epoxies and a graphite/S-glass/epoxy. Properties were obtained by testing thin rings 10.16 cm (4 in.) in diameter, 2.54 cm (1 in.) wide, and six to eight plies thick under internal pressure. Unidirectional 0 degree, 90 degree, and 10 degree off-axis rings were tested to obtain longitudinal, transverse, and in-plane shear properties. In the dynamic tests internal pressure was applied explosively through a liquid and the pressure was measured with a calibrated steel ring. <span class="hlt">Strains</span> in the calibration and specimen rings were recorded with a digital processing oscilloscope. The data were processed and the equation of motion solved numerically by the mini-computer attached to the oscilloscope. Results were obtained and plotted in the form of dynamic stress-<span class="hlt">strain</span> curves. Longitudinal properties which are governed by the fibers do not vary much with <span class="hlt">strain</span> <span class="hlt">rate</span> with only a moderate (up to 20 percent) increase in modulus. Transverse modulus and strength increase sharply with <span class="hlt">strain</span> <span class="hlt">rate</span> reaching values up to three times the static values. The in-plane shear modulus and shear strength increase noticeably with <span class="hlt">strain</span> <span class="hlt">rate</span> by up to approximately 65 percent. In all cases ultimate <span class="hlt">strains</span> do not vary significantly with <span class="hlt">strain</span> <span class="hlt">rates</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012MTDM...16..361O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012MTDM...16..361O"><span id="translatedtitle">Compression of polypropylene across a wide range of <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Okereke, M. I.; Buckley, C. P.; Siviour, C. R.</p> <p>2012-11-01</p> <p>Three grades of polypropylene were tested in uniaxial compression at room temperature, across a wide range of <span class="hlt">strain</span> <span class="hlt">rate</span>: 10-4 s-1 to 104 s-1. One grade is a conventional polypropylene homopolymer. The two other grades are the polypropylene forming the matrix phase of a continuous glass fibre-reinforced thermoplastic composite prepreg, with and without blending with a carbon-black master batch. Tests at the highest <span class="hlt">strain</span> <span class="hlt">rates</span> were performed using a compression split Hopkinson pressure bar. The test specimens, for all the three <span class="hlt">rates</span>, were imaged using appropriate digital cameras in order to observe the deformation process. In addition, the images obtained were analysed digitally to obtain true <span class="hlt">strain</span> measurements for the medium <span class="hlt">rates</span> category. All three grades of polypropylene showed pronounced <span class="hlt">strain-rate</span> dependence of compressive yield stress, increasing by factors of up to 4 across the range of <span class="hlt">rates</span>. At the lowest <span class="hlt">rates</span>, there was close agreement between the yield stresses for all three materials, and also close agreement with the Eyring theory. Considering the highest <span class="hlt">strain</span> <span class="hlt">rates</span>, however, yield stresses increased more rapidly with log(<span class="hlt">strain-rate</span>) than would be expected from a linear Eyring prediction and values for the three materials diverged. This was attributed to the contributions made in each material by both alpha and beta relaxation processes. Also prominent in the medium- and high-<span class="hlt">rate</span> experimental results was pronounced post-yield <span class="hlt">strain</span> softening, greatest at the highest <span class="hlt">strain-rates</span>. This resulted from a combination of thermal softening from adiabatic heating, and structural rejuvenation as often seen in glassy polymers in quasi-static tests.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JNEng..12c6002S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JNEng..12c6002S"><span id="translatedtitle">Compliant intracortical implants reduce <span class="hlt">strains</span> and <span class="hlt">strain</span> <span class="hlt">rates</span> in brain tissue in vivo</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sridharan, Arati; Nguyen, Jessica K.; Capadona, Jeffrey R.; Muthuswamy, Jit</p> <p>2015-06-01</p> <p>Objective. The objective of this research is to characterize the mechanical interactions of (1) soft, compliant and (2) non-compliant implants with the surrounding brain tissue in a rodent brain. Understanding such interactions will enable the engineering of novel materials that will improve stability and reliability of brain implants. Approach. Acute force measurements were made using a load cell in n = 3 live rats, each with 4 craniotomies. Using an indentation method, brain tissue was tested for changes in force using established protocols. A total of 4 non-compliant, bare silicon microshanks, 3 non-compliant polyvinyl acetate (PVAc)-coated silicon microshanks, and 6 compliant, nanocomposite microshanks were tested. Stress values were calculated by dividing the force by surface area and <span class="hlt">strain</span> was estimated using a linear stress-<span class="hlt">strain</span> relationship. Micromotion <span class="hlt">effects</span> from breathing and vascular pulsatility on tissue stress were estimated from a 5 s interval of steady-state measurements. Viscoelastic properties were estimated using a second-order Prony series expansion of stress-displacement curves for each shank. Main results. The distribution of <span class="hlt">strain</span> values imposed on brain tissue for both compliant nanocomposite microshanks and PVAc-coated, non-compliant silicon microshanks were significantly lower compared to non-compliant bare silicon shanks. Interestingly, step-indentation experiments also showed that compliant, nanocomposite materials significantly decreased stress relaxation <span class="hlt">rates</span> in the brain tissue at the interface (p < 0.05) compared to non-compliant silicon and PVAc-coated silicon materials. Furthermore, both PVAc-coated non-compliant silicon and compliant nanocomposite shanks showed significantly reduced (by 4-5 fold) stresses due to tissue micromotion at the interface. Significance. The results of this study showed that soft, adaptive materials reduce <span class="hlt">strains</span> and <span class="hlt">strain</span> <span class="hlt">rates</span> and micromotion induced stresses in the surrounding brain tissue</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26063842','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26063842"><span id="translatedtitle">Bone <span class="hlt">strain</span> magnitude is correlated with bone <span class="hlt">strain</span> <span class="hlt">rate</span> in tetrapods: implications for models of mechanotransduction.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Aiello, B R; Iriarte-Diaz, J; Blob, R W; Butcher, M T; Carrano, M T; Espinoza, N R; Main, R P; Ross, C F</p> <p>2015-07-07</p> <p>Hypotheses suggest that structural integrity of vertebrate bones is maintained by controlling bone <span class="hlt">strain</span> magnitude via adaptive modelling in response to mechanical stimuli. Increased tissue-level <span class="hlt">strain</span> magnitude and <span class="hlt">rate</span> have both been identified as potent stimuli leading to increased bone formation. Mechanotransduction models hypothesize that osteocytes sense bone deformation by detecting fluid flow-induced drag in the bone's lacunar-canalicular porosity. This model suggests that the osteocyte's intracellular response depends on fluid-flow <span class="hlt">rate</span>, a product of bone <span class="hlt">strain</span> <span class="hlt">rate</span> and gradient, but does not provide a mechanism for detection of <span class="hlt">strain</span> magnitude. Such a mechanism is necessary for bone modelling to adapt to loads, because <span class="hlt">strain</span> magnitude is an important determinant of skeletal fracture. Using <span class="hlt">strain</span> gauge data from the limb bones of amphibians, reptiles, birds and mammals, we identified strong correlations between <span class="hlt">strain</span> <span class="hlt">rate</span> and magnitude across clades employing diverse locomotor styles and degrees of rhythmicity. The breadth of our sample suggests that this pattern is likely to be a common feature of tetrapod bone loading. Moreover, finding that bone <span class="hlt">strain</span> magnitude is encoded in <span class="hlt">strain</span> <span class="hlt">rate</span> at the tissue level is consistent with the hypothesis that it might be encoded in fluid-flow <span class="hlt">rate</span> at the cellular level, facilitating bone adaptation via mechanotransduction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4590470','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4590470"><span id="translatedtitle">Bone <span class="hlt">strain</span> magnitude is correlated with bone <span class="hlt">strain</span> <span class="hlt">rate</span> in tetrapods: implications for models of mechanotransduction</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Aiello, B. R.; Iriarte-Diaz, J.; Blob, R. W.; Butcher, M. T.; Carrano, M. T.; Espinoza, N. R.; Main, R. P.; Ross, C. F.</p> <p>2015-01-01</p> <p>Hypotheses suggest that structural integrity of vertebrate bones is maintained by controlling bone <span class="hlt">strain</span> magnitude via adaptive modelling in response to mechanical stimuli. Increased tissue-level <span class="hlt">strain</span> magnitude and <span class="hlt">rate</span> have both been identified as potent stimuli leading to increased bone formation. Mechanotransduction models hypothesize that osteocytes sense bone deformation by detecting fluid flow-induced drag in the bone's lacunar–canalicular porosity. This model suggests that the osteocyte's intracellular response depends on fluid-flow <span class="hlt">rate</span>, a product of bone <span class="hlt">strain</span> <span class="hlt">rate</span> and gradient, but does not provide a mechanism for detection of <span class="hlt">strain</span> magnitude. Such a mechanism is necessary for bone modelling to adapt to loads, because <span class="hlt">strain</span> magnitude is an important determinant of skeletal fracture. Using <span class="hlt">strain</span> gauge data from the limb bones of amphibians, reptiles, birds and mammals, we identified strong correlations between <span class="hlt">strain</span> <span class="hlt">rate</span> and magnitude across clades employing diverse locomotor styles and degrees of rhythmicity. The breadth of our sample suggests that this pattern is likely to be a common feature of tetrapod bone loading. Moreover, finding that bone <span class="hlt">strain</span> magnitude is encoded in <span class="hlt">strain</span> <span class="hlt">rate</span> at the tissue level is consistent with the hypothesis that it might be encoded in fluid-flow <span class="hlt">rate</span> at the cellular level, facilitating bone adaptation via mechanotransduction. PMID:26063842</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26178155','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26178155"><span id="translatedtitle"><span class="hlt">Strain/strain</span> <span class="hlt">rate</span> imaging of impaired left atrial function in patients with metabolic syndrome.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fang, Ning-Ning; Sui, Dong-Xin; Yu, Jin-Gui; Gong, Hui-Ping; Zhong, Ming; Zhang, Yun; Zhang, Wei</p> <p>2015-11-01</p> <p>Left ventricular (LV) dysfunction has been demonstrated in patients with metabolic syndrome (MetS). However, alterations in left atrial (LA) function in MetS are unknown. We aimed to use <span class="hlt">strain/strain</span> <span class="hlt">rate</span> (SR) imaging to investigate the <span class="hlt">effect</span> of MetS on LA function. A total of 177 MetS patients and 156 normal subjects underwent echocardiography. <span class="hlt">Strain</span> and SR tissue Doppler imaging values were used to evaluate LA function. Partial correlation and multiple stepwise regression analyses were used to determine the risk factors for impaired LA function. Compared with the controls, the MetS patients showed significantly lower levels of mean <span class="hlt">strain</span>, mean peak systolic SR and mean peak early diastolic SR (P<0.001 for all), with no difference in the mean peak late diastolic SR. Central obesity, hypertension, dyslipidemia and LV diastolic abnormality were independent risk factors for impaired LA function. LA function was impaired in patients with MetS as a result of metabolic disturbance and LV diastolic abnormality. SR imaging is reliable in assessing LA function in MetS patients.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21003546','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21003546"><span id="translatedtitle"><span class="hlt">Effect</span> of Zn addition, <span class="hlt">strain</span> <span class="hlt">rate</span> and deformation temperature on the tensile properties of Sn-3.3 wt.% Ag solder alloy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fawzy, A. . E-mail: afawzy1955@yahoo.com</p> <p>2007-04-15</p> <p>Stress-<span class="hlt">strain</span> characteristics of the binary Sn-3.3 wt.% Ag and the tertiary Sn-3.3 wt.% Ag-1 wt.% Zn solder alloys were investigated at various <span class="hlt">strain</span> <span class="hlt">rates</span> (SR, {epsilon} {sup .}) from 2.6 x 10{sup -4} to 1.0 x 10{sup -2} s{sup -1} and deformation temperatures from 300 to 373 K. Addition of 1 wt.% Zn to the binary alloy increased the yield stress {sigma} {sub y} and the ultimate tensile stress {sigma} {sub UTS} while a decrease of ductility (total elongation {epsilon} {sub T}) was observed. Increasing the <span class="hlt">strain</span> <span class="hlt">rate</span> ({epsilon} {sup .}) increased both {sigma} {sub y} and {sigma} {sub UTS} according to the power law {sigma} = C {epsilon} {sup .m}. A normal decrease of {epsilon} {sub T} with <span class="hlt">strain</span> <span class="hlt">rate</span> was observed according to an empirical equation of the form {epsilon} {sub T} = A exp (- {lambda}{epsilon} {sup .}); A and {lambda} are constants. Increasing the deformation temperature decreased both {sigma} {sub y} and {sigma} {sub UTS} in both alloys, and decreased the total elongation {epsilon} {sub T} in the Zn-free binary alloy, whereas {epsilon} {sub T} was increased in the Zn-containing alloy. The activation energy was determined as 41 and 20 kJ mol{sup -1} for these alloys, respectively. The results obtained were interpreted in terms of the variation of the internal microstructure in both alloys. The internal microstructural variations in the present study were evaluated by optical microscopy, electron microscopy and X-ray diffraction. The results show the importance of Zn addition in enhancing the mechanical strength of the Sn-3.3 wt.% Ag base alloy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19990081117','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990081117"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">Rate</span> Dependent Modeling of Polymer Matrix Composites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldberg, Robert K.; Stouffer, Donald C.</p> <p>1999-01-01</p> <p>A research program is in progress to develop <span class="hlt">strain</span> <span class="hlt">rate</span> dependent deformation and failure models for the analysis of polymer matrix composites subject to high <span class="hlt">strain</span> <span class="hlt">rate</span> impact loads. <span class="hlt">Strain</span> <span class="hlt">rate</span> dependent inelastic constitutive equations have been developed to model the polymer matrix, and have been incorporated into a micromechanics approach to analyze polymer matrix composites. The Hashin failure criterion has been implemented within the micromechanics results to predict ply failure strengths. The deformation model has been implemented within LS-DYNA, a commercially available transient dynamic finite element code. The deformation response and ply failure stresses for the representative polymer matrix composite AS4/PEEK have been predicted for a variety of fiber orientations and <span class="hlt">strain</span> <span class="hlt">rates</span>. The predicted results compare favorably to experimentally obtained values.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APLM....4f4107S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APLM....4f4107S"><span id="translatedtitle">Elastocaloric cooling processes: The influence of material <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> on efficiency and temperature span</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmidt, Marvin; Schütze, Andreas; Seelecke, Stefan</p> <p>2016-06-01</p> <p>This paper discusses the influence of material <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> on efficiency and temperature span of elastocaloric cooling processes. The elastocaloric material, a newly developed quaternary Ni-Ti-Cu-V alloy, is characterized at different maximum <span class="hlt">strains</span> and <span class="hlt">strain</span> <span class="hlt">rates</span>. The experiments are performed with a specially designed test setup, which enables the measurement of mechanical and thermal process parameters. The material efficiency is compared to the efficiency of the Carnot process at equivalent thermal operation conditions. This method allows for a direct comparison of the investigated material with other caloric materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA179488','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA179488"><span id="translatedtitle">High-<span class="hlt">Strain-Rate</span> behavior of Hydrated Cement Paste.</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1987-01-29</p> <p>bar and the transmitter bar are made from high yield- strength material, peak loads of 150,000 psi or 10 kbar are easily reached. Typical <span class="hlt">strain</span> <span class="hlt">rates</span>...was originally set up for testing very high yield- strength materials. Therefore, for use with cement paste samples, a series of new pressure bars -- 1...a. A a.5.. ~ A - a .- ~- . . . ~0 MML TR 87-12c HIGH -<span class="hlt">STRAIN-RATE</span> BEHAVIOR OF HYDRATED CEMENT PASTE</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/762874','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/762874"><span id="translatedtitle">Imploding Liner Material Strength Measurements at High-<span class="hlt">Strain</span> and High <span class="hlt">Strain</span> <span class="hlt">Rate</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bartsch, R.R.; Lee, H.; Holtkamp, D.; Wright, B.; Stokes, J.; Morgan, D.; Anderson, W.; Broste, W.</p> <p>1998-10-18</p> <p>Imploding, cylindrical liners provide a unique, shockless means of simultaneously accessing high <span class="hlt">strain</span> and high-<span class="hlt">strain-rate</span> for measurement of strength of materials in plastic flow. The radial convergence in the liner geometry results in the liner thickening as the circumference becomes smaller. <span class="hlt">Strains</span> of up to {approximately}1.25 and <span class="hlt">strain</span> <span class="hlt">rates</span> of up to {approximately}10{sup 6} sec{sup -1} can be readily achieved in a material sample placed inside of an aluminum driver liner, using the Pegasus II capacitor bank. This provides yield strength data at conditions where none presently exists. The heating from work done against the yield strength is measured with multichannel pyrometry from infrared radiation emitted by the material sample. The temperature data as a function of liner position are unfolded to give the yield strength along the <span class="hlt">strain</span>, <span class="hlt">strain-rate</span> trajectory. Proper design of the liner and sample configuration ensures that the current diffused into the sample adds negligible heating. An important issue, in this type of temperature measurement, is shielding of the pickup optics from other sources of radiation. At <span class="hlt">strains</span> greater than those achievable on Pegasus, e.g. the LANL Atlas facility, some materials may be heated all the way to melt by this process. Recent data on 6061-T6 Aluminum will be compared with an existing model for <span class="hlt">strain</span> and <span class="hlt">strain-rate</span> heating. The liner configuration and pyrometry diagnostic will also be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1116483','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1116483"><span id="translatedtitle">Mapping <span class="hlt">Strain-rate</span> Dependent Dislocation-Defect Interactions by Atomistic Simulations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fan, Yue; Osetskiy, Yury N; Yip, Sidney; Yildiz-Botterud, Bilge</p> <p>2013-01-01</p> <p>Probing the mechanisms of defect-defect interactions at <span class="hlt">strain</span> <span class="hlt">rates</span> lower than 106 s-1 is an unresolved challenge to date to molecular dynamics (MD) techniques. Here we propose a novel atomistic approach based on transition state theory and the concept of a <span class="hlt">strain</span>-dependent <span class="hlt">effective</span> activation barrier that is capable of simulating the kinetics of dislocation-defect interactions at virtually any <span class="hlt">strain</span> <span class="hlt">rate</span>, exemplified within 10-7 to 107 s-1. We apply this approach to the problem of an edge dislocation colliding with a cluster of self-interstitial atoms (SIA) under shear deformation. Using an activation-relaxation algorithm (1), we uncover a unique <span class="hlt">strain-rate</span> dependent trigger mechanism that allows the SIA cluster to be absorbed during the process leading to dislocation climb. Guided by this finding, we determine the activation barrier of the trigger mechanism as a function of shear <span class="hlt">strain</span>, and use that in a coarse-graining <span class="hlt">rate</span> equation formulation for constructing a mechanism map in the phase space of <span class="hlt">strain-rate</span> and temperature. Our predictions of a crossover from a defect recovery at the low <span class="hlt">strain</span> <span class="hlt">rate</span> regime to defect absorption behavior in the high <span class="hlt">strain-rate</span> regime are validated against our own independent, direct MD simulations at 105 to 107 s-1. Implications of the present approach for probing molecular-level mechanisms in <span class="hlt">strain-rate</span> regimes previously considered inaccessible to atomistic simulations are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6204455','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6204455"><span id="translatedtitle">The <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> on the tensile properties of an Al[sub 2]O[sub 3p]/6061-T6 aluminum metal-matrix composite at low temperatures</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chia Chaw Perng; Jiun Ren Hwang; Ji Liang Doong )</p> <p>1993-08-01</p> <p>Alumina (Al[sub 2]O[sub 3]) particles reinforced aluminum matrix composites have recently become candidates for structural materials because of their good specific modulus and strength, and are considered to be valuable materials for aerospace and automobile industry applications. In view of such application, they might be processed or applied in high <span class="hlt">strain</span> <span class="hlt">rate</span> loading conditions, such as explosive forming, blast loading and metalworking, etc. Knowledge of the mechanical behavior of the metal matrix composites under high <span class="hlt">strain</span> <span class="hlt">rate</span> loading is a prerequisite. However, not much work related to this topic has been done. The objective of this study was to investigate the <span class="hlt">effect</span> of the <span class="hlt">strain</span> <span class="hlt">rate</span> on the tensile properties of the Al[sub 2]O[sub 3p]/6061-T6 composite at low temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25100211','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25100211"><span id="translatedtitle">Sensitive, high-<span class="hlt">strain</span>, high-<span class="hlt">rate</span> bodily motion sensors based on graphene-rubber composites.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Boland, Conor S; Khan, Umar; Backes, Claudia; O'Neill, Arlene; McCauley, Joe; Duane, Shane; Shanker, Ravi; Liu, Yang; Jurewicz, Izabela; Dalton, Alan B; Coleman, Jonathan N</p> <p>2014-09-23</p> <p>Monitoring of human bodily motion requires wearable sensors that can detect position, velocity and acceleration. They should be cheap, lightweight, mechanically compliant and display reasonable sensitivity at high <span class="hlt">strains</span> and <span class="hlt">strain</span> <span class="hlt">rates</span>. No reported material has simultaneously demonstrated all the above requirements. Here we describe a simple method to infuse liquid-exfoliated graphene into natural rubber to create conducting composites. These materials are excellent <span class="hlt">strain</span> sensors displaying 10(4)-fold increases in resistance and working at <span class="hlt">strains</span> exceeding 800%. The sensitivity is reasonably high, with gauge factors of up to 35 observed. More importantly, these sensors can <span class="hlt">effectively</span> track dynamic <span class="hlt">strain</span>, working well at vibration frequencies of at least 160 Hz. At 60 Hz, we could monitor <span class="hlt">strains</span> of at least 6% at <span class="hlt">strain</span> <span class="hlt">rates</span> exceeding 6000%/s. We have used these composites as bodily motion sensors, <span class="hlt">effectively</span> monitoring joint and muscle motion as well and breathing and pulse.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040161227','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040161227"><span id="translatedtitle">Suppression of Low <span class="hlt">Strain</span> <span class="hlt">Rate</span> Nonpremixed Flames by an Agent</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Olson, Sandra L. (Technical Monitor); Hamins, A.; Bundy, M.; Oh, C. B.; Park, J.; Puri, I. K.</p> <p>2004-01-01</p> <p>The extinction and structure of non-premixed methane/air flames were investigated in normal gravity and microgravity through the comparison of experiments and calculations using a counterflow configuration. From a fire safety perspective, low <span class="hlt">strain</span> <span class="hlt">rate</span> conditions are important for several reasons. In normal gravity, many fires start from small ignition sources where the convective flow and <span class="hlt">strain</span> <span class="hlt">rates</span> are weak. Fires in microgravity conditions, such as a manned spacecraft, may also occur in near quiescent conditions where <span class="hlt">strain</span> <span class="hlt">rates</span> are very low. When designing a fire suppression system, worst-case conditions should be considered. Most diffusion flames become more robust as the <span class="hlt">strain</span> <span class="hlt">rate</span> is decreased. The goal of this project is to investigate the extinction limits of non-premixed flames using various agents and to compare reduced gravity and normal gravity conditions. Experiments at the NASA Glenn Research Center's 2.2-second drop tower were conducted to attain extinction and temperature measurements in low-<span class="hlt">strain</span> non-premixed flames. Extinction measurements using nitrogen added to the fuel stream were performed for global <span class="hlt">strain</span> <span class="hlt">rates</span> from 7/s to 50/s. The results confirmed the "turning point" behavior observed previously by Maruta et al. in a 10 s drop tower. The maximum nitrogen volume fraction in the fuel stream needed to assure extinction for all <span class="hlt">strain</span> <span class="hlt">rates</span> was measured to be 0.855+/-0.016, associated with the turning point determined to occur at a <span class="hlt">strain</span> <span class="hlt">rate</span> of 15/s. The critical nitrogen volume fraction in the fuel stream needed for extinction of 0-g flames was measured to be higher than that of 1-g flames.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..MARX21002L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..MARX21002L"><span id="translatedtitle">Tantalum strength model incorporating temperature, <span class="hlt">strain</span> <span class="hlt">rate</span> and pressure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lim, Hojun; Battaile, Corbett; Brown, Justin; Lane, Matt</p> <p></p> <p>Tantalum is a body-centered-cubic (BCC) refractory metal that is widely used in many applications in high temperature, <span class="hlt">strain</span> <span class="hlt">rate</span> and pressure environments. In this work, we propose a physically-based strength model for tantalum that incorporates <span class="hlt">effects</span> of temperature, <span class="hlt">strain</span> <span class="hlt">rate</span> and pressure. A constitutive model for single crystal tantalum is developed based on dislocation kink-pair theory, and calibrated to measurements on single crystal specimens. The model is then used to predict deformations of single- and polycrystalline tantalum. In addition, the proposed strength model is implemented into Sandia's ALEGRA solid dynamics code to predict plastic deformations of tantalum in engineering-scale applications at extreme conditions, e.g. Taylor impact tests and Z machine's high pressure ramp compression tests, and the results are compared with available experimental data. Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850022925','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850022925"><span id="translatedtitle">Residual thermal and moisture influences on the <span class="hlt">strain</span> energy release <span class="hlt">rate</span> analysis of edge delamination</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Obrien, T. K.; Raju, I. S.; Garber, D. P.</p> <p>1985-01-01</p> <p>A laminated plate theory analysis is developed to calculate the <span class="hlt">strain</span> energy release <span class="hlt">rate</span> associated with edge delamination growth in a composite laminate. The analysis includes the contribution of residual thermal and moisture stresses to the <span class="hlt">strain</span> energy released. The <span class="hlt">strain</span> energy release <span class="hlt">rate</span>, G, increased when residual thermal <span class="hlt">effects</span> were combined with applied mechanical <span class="hlt">strains</span>, but then decreased when increasing moisture content was included. A quasi-three-dimensional finite element analysis indicated identical trends and demonstrated these same trends for the individual <span class="hlt">strain</span> energy release <span class="hlt">rate</span> components, G sub I and G sub II, associated with interlaminar tension and shear. An experimental study indicated that for T300/5208 graphite-epoxy composites, the inclusion of residual thermal and moisture stresses did not significantly alter the calculation of interlaminar fracture toughness from <span class="hlt">strain</span> energy release <span class="hlt">rate</span> analysis of edge delamination data taken at room temperature, ambient conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EPJWC..2602009K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EPJWC..2602009K"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> dependence in plasticized and un-plasticized PVC</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kendall, M. J.; Siviour, C. R.</p> <p>2012-08-01</p> <p>An experimental and analytical investigation has been made into the mechanical behaviour of two poly (vinyl chloride) (PVC) polymers - an un-plasticized PVC and a diisononyl phthalate (DINP)-plasticized PVC. Measurements of the compressive stress-<span class="hlt">strain</span> behaviour of the PVCs at <span class="hlt">strain</span> <span class="hlt">rates</span> ranging from 10-3 to 103s-1 and temperatures from - 60 to 100∘C are presented. Dynamic Mechanical Analysis was also performed in order to understand the material transitions observed in compression testing as the <span class="hlt">strain</span> <span class="hlt">rate</span> is increased. This investigation develops a better understanding of the interplay between the temperature dependence and <span class="hlt">rate</span> dependence of polymers, with a focus on locating the temperature and <span class="hlt">rate</span>-dependent material transitions that occur during high <span class="hlt">rate</span> testing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3816434','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3816434"><span id="translatedtitle">Mapping <span class="hlt">strain</span> <span class="hlt">rate</span> dependence of dislocation-defect interactions by atomistic simulations</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Fan, Yue; Osetskiy, Yuri N.; Yip, Sidney; Yildiz, Bilge</p> <p>2013-01-01</p> <p>Probing the mechanisms of defect–defect interactions at <span class="hlt">strain</span> <span class="hlt">rates</span> lower than 106 s−1 is an unresolved challenge to date to molecular dynamics (MD) techniques. Here we propose an original atomistic approach based on transition state theory and the concept of a <span class="hlt">strain</span>-dependent <span class="hlt">effective</span> activation barrier that is capable of simulating the kinetics of dislocation–defect interactions at virtually any <span class="hlt">strain</span> <span class="hlt">rate</span>, exemplified within 10−7 to 107 s−1. We apply this approach to the problem of an edge dislocation colliding with a cluster of self-interstitial atoms (SIAs) under shear deformation. Using an activation–relaxation algorithm [Kushima A, et al. (2009) J Chem Phys 130:224504], we uncover a unique <span class="hlt">strain</span>-rate–dependent trigger mechanism that allows the SIA cluster to be absorbed during the process, leading to dislocation climb. Guided by this finding, we determine the activation barrier of the trigger mechanism as a function of shear <span class="hlt">strain</span>, and use that in a coarse-graining <span class="hlt">rate</span> equation formulation for constructing a mechanism map in the phase space of <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature. Our predictions of a crossover from a defect recovery at the low <span class="hlt">strain-rate</span> regime to defect absorption behavior in the high <span class="hlt">strain-rate</span> regime are validated against our own independent, direct MD simulations at 105 to 107 s−1. Implications of the present approach for probing molecular-level mechanisms in <span class="hlt">strain-rate</span> regimes previously considered inaccessible to atomistic simulations are discussed. PMID:24114271</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/495681','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/495681"><span id="translatedtitle">Bicrystals with <span class="hlt">strain</span> gradient <span class="hlt">effects</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Shu, J.Y.</p> <p>1997-01-09</p> <p>Boundary between two perfectly bonded single crystals plays an important role in determining the deformation of the bicrystals. This work addresses the role of the grain boundary by considering the elevated hardening of a slip system due to a slip gradient. The slip gradients are associated with geometrically necessary dislocations and their <span class="hlt">effects</span> become pronounced when a representative length scale of the deformation field is comparable to the dominant microstructural length scale of a material. A new <span class="hlt">rate</span>-dependent crystal plasticity theory is presented and has been implemented within the finite element method framework. A planar bicrystal under uniform in-plane loading is studied using the new crystal theory. The <span class="hlt">strain</span> is found to be continuous but nonuniform within a boundary layer around the interface. The lattice rotation is also nonuniform within the boundary layer. The width of the layer is determined by the misorientation of the grains, the hardening of slip systems, and most importantly by the characteristic material length scales. The overall yield strength of the bicrystal is also obtained. A significant grain-size dependence of the yield strength, the Hall- Petch <span class="hlt">effect</span> is predicted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020060784','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020060784"><span id="translatedtitle">Computational Simulation of the High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Tensile Response of Polymer Matrix Composites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldberg, Robert K.</p> <p>2002-01-01</p> <p>A research program is underway to develop <span class="hlt">strain</span> <span class="hlt">rate</span> dependent deformation and failure models for the analysis of polymer matrix composites subject to high <span class="hlt">strain</span> <span class="hlt">rate</span> impact loads. Under these types of loading conditions, the material response can be highly <span class="hlt">strain</span> <span class="hlt">rate</span> dependent and nonlinear. State variable constitutive equations based on a viscoplasticity approach have been developed to model the deformation of the polymer matrix. The constitutive equations are then combined with a mechanics of materials based micromechanics model which utilizes fiber substructuring to predict the <span class="hlt">effective</span> mechanical and thermal response of the composite. To verify the analytical model, tensile stress-<span class="hlt">strain</span> curves are predicted for a representative composite over <span class="hlt">strain</span> <span class="hlt">rates</span> ranging from around 1 x 10(exp -5)/sec to approximately 400/sec. The analytical predictions compare favorably to experimentally obtained values both qualitatively and quantitatively. <span class="hlt">Effective</span> elastic and thermal constants are predicted for another composite, and compared to finite element results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050196804','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050196804"><span id="translatedtitle">High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Behavior of Polymer Matrix Composites Analyzed</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldberg, Robert K.; Roberts, Gary D.</p> <p>2001-01-01</p> <p>Procedures for modeling the high-speed impact of composite materials are needed for designing reliable composite engine cases that are lighter than the metal cases in current use. The types of polymer matrix composites that are likely to be used in such an application have a deformation response that is nonlinear and that varies with <span class="hlt">strain</span> <span class="hlt">rate</span>. To characterize and validate material models that could be used in the design of impactresistant engine cases, researchers must obtain material data over a wide variety of <span class="hlt">strain</span> <span class="hlt">rates</span>. An experimental program has been carried out through a university grant with the Ohio State University to obtain deformation data for a representative polymer matrix composite for <span class="hlt">strain</span> <span class="hlt">rates</span> ranging from quasi-static to high <span class="hlt">rates</span> of several hundred per second. This information has been used to characterize and validate a constitutive model that was developed at the NASA Glenn Research Center.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22560644','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22560644"><span id="translatedtitle">Evaluation of the influence of <span class="hlt">strain</span> <span class="hlt">rate</span> on Colles' fracture load.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ural, Ani; Zioupos, Peter; Buchanan, Drew; Vashishth, Deepak</p> <p>2012-06-26</p> <p>Colles' fracture, a transverse fracture of the distal radius bone, is one of the most frequently observed osteoporotic fractures resulting from low energy or traumatic events, associated with low and high <span class="hlt">strain</span> <span class="hlt">rates</span>, respectively. Although experimental studies on Colles' fracture were carried out at various loading <span class="hlt">rates</span> ranging from static to impact loadings, there is no systematic study in the literature that isolates the influence of <span class="hlt">strain</span> <span class="hlt">rate</span> on Colles' fracture load. In order to provide a better understanding of fracture risk, the current study combines experimental material property measurements under varying <span class="hlt">strain</span> <span class="hlt">rates</span> with computational modeling and presents new information on the <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> on Colles' fracture. The simulation results showed that Colles' fracture load decreased with increasing <span class="hlt">strain</span> <span class="hlt">rate</span> with a steeper change in lower <span class="hlt">strain</span> <span class="hlt">rates</span>. Specifically, <span class="hlt">strain</span> <span class="hlt">rate</span> values (0.29s(-1)) associated with controlled falling without fracture corresponded to a 3.7% reduction in the fracture load. On the other hand, the reduction in the fracture load was 34% for <span class="hlt">strain</span> <span class="hlt">rate</span> of 3.7s(-1) reported in fracture inducing impact cadaver experiments. Further increase in the <span class="hlt">strain</span> <span class="hlt">rate</span> up to 18s(-1) led to an additional 22% reduction. The most drastic reduction in fracture load occurs at <span class="hlt">strain</span> <span class="hlt">rates</span> corresponding to the transition from controlled to impact falling. These results are particularly important for the improvement of fracture risk assessment in the elderly because they identify a critical range of loading <span class="hlt">rates</span> (10-50mm/s) that can dramatically increase the risk of Colles' fracture.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3391025','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3391025"><span id="translatedtitle">EVALUATION OF THE INFLUENCE OF <span class="hlt">STRAIN</span> <span class="hlt">RATE</span> ON COLLES’ FRACTURE LOAD</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ural, Ani; Zioupos, Peter; Buchanan, Drew; Vashishth, Deepak</p> <p>2012-01-01</p> <p>Colles’ fracture, a transverse fracture of the distal radius bone, is one of the most frequently observed osteoporotic fractures resulting from low energy or traumatic events, associated with low and high <span class="hlt">strain</span> <span class="hlt">rates</span>, respectively. Although experimental studies on Colles’ fracture were carried out at various loading <span class="hlt">rates</span> ranging from static to impact loading, there is no systematic study in the literature that isolates the influence of <span class="hlt">strain</span> <span class="hlt">rate</span> on Colles’ fracture load. In order to provide a better understanding of fracture risk, the current study combines experimental material property measurements under varying <span class="hlt">strain</span> <span class="hlt">rates</span> with computational modeling and presents new information on the <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> on Colles’ fracture. The simulation results showed that the Colles’ fracture load decreased with increasing <span class="hlt">strain</span> <span class="hlt">rate</span> with a steeper change in lower <span class="hlt">strain</span> <span class="hlt">rates</span>. Specifically, <span class="hlt">strain</span> <span class="hlt">rate</span> values (0.29 s−1) associated with controlled falling without fracture corresponded to a 3.7% reduction in the fracture load. On the other hand, the reduction in the fracture load was 34% for <span class="hlt">strain</span> <span class="hlt">rate</span> of 3.7 s−1 reported in fracture inducing impact cadaver experiments. Further increase in the <span class="hlt">strain</span> <span class="hlt">rate</span> up to 18 s−1 lead to an additional 22% reduction. The most drastic reduction in fracture load occurs at <span class="hlt">strain</span> <span class="hlt">rates</span> corresponding to the transition from controlled to impact falling. These results are particularly important for the improvement of fracture risk assessment in the elderly because they identify a critical range of loading <span class="hlt">rates</span> (10–50 mm/s) that can dramatically increase the risk of Colles’ fracture. PMID:22560644</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24883355','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24883355"><span id="translatedtitle">Experimental and numerical study on tensile strength of concrete under different <span class="hlt">strain</span> <span class="hlt">rates</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Min, Fanlu; Yao, Zhanhu; Jiang, Teng</p> <p>2014-01-01</p> <p>The dynamic characterization of concrete is fundamental to understand the material behavior in case of heavy earthquakes and dynamic events. The implementation of material constitutive law is of capital importance for the numerical simulation of the dynamic processes as those caused by earthquakes. Splitting tensile concrete specimens were tested at <span class="hlt">strain</span> <span class="hlt">rates</span> of 10(-7) s(-1) to 10(-4) s(-1) in an MTS material test machine. Results of tensile strength versus <span class="hlt">strain</span> <span class="hlt">rate</span> are presented and compared with compressive strength and existing models at similar <span class="hlt">strain</span> <span class="hlt">rates</span>. Dynamic increase factor versus <span class="hlt">strain</span> <span class="hlt">rate</span> curves for tensile strength were also evaluated and discussed. The same tensile data are compared with strength data using a thermodynamic model. Results of the tests show a significant <span class="hlt">strain</span> <span class="hlt">rate</span> sensitive behavior, exhibiting dynamic tensile strength increasing with <span class="hlt">strain</span> <span class="hlt">rate</span>. In the quasistatic <span class="hlt">strain</span> <span class="hlt">rate</span> regime, the existing models often underestimate the experimental results. The thermodynamic theory for the splitting tensile strength of concrete satisfactorily describes the experimental findings of strength as <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rates</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4030507','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4030507"><span id="translatedtitle">Experimental and Numerical Study on Tensile Strength of Concrete under Different <span class="hlt">Strain</span> <span class="hlt">Rates</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Min, Fanlu; Yao, Zhanhu; Jiang, Teng</p> <p>2014-01-01</p> <p>The dynamic characterization of concrete is fundamental to understand the material behavior in case of heavy earthquakes and dynamic events. The implementation of material constitutive law is of capital importance for the numerical simulation of the dynamic processes as those caused by earthquakes. Splitting tensile concrete specimens were tested at <span class="hlt">strain</span> <span class="hlt">rates</span> of 10−7 s−1 to 10−4 s−1 in an MTS material test machine. Results of tensile strength versus <span class="hlt">strain</span> <span class="hlt">rate</span> are presented and compared with compressive strength and existing models at similar <span class="hlt">strain</span> <span class="hlt">rates</span>. Dynamic increase factor versus <span class="hlt">strain</span> <span class="hlt">rate</span> curves for tensile strength were also evaluated and discussed. The same tensile data are compared with strength data using a thermodynamic model. Results of the tests show a significant <span class="hlt">strain</span> <span class="hlt">rate</span> sensitive behavior, exhibiting dynamic tensile strength increasing with <span class="hlt">strain</span> <span class="hlt">rate</span>. In the quasistatic <span class="hlt">strain</span> <span class="hlt">rate</span> regime, the existing models often underestimate the experimental results. The thermodynamic theory for the splitting tensile strength of concrete satisfactorily describes the experimental findings of strength as <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rates</span>. PMID:24883355</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/759337','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/759337"><span id="translatedtitle">Magnetic Implosion for Novel Strength Measurements at High <span class="hlt">Strain</span> <span class="hlt">Rates</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lee, H.; Preston, D.L.; Bartsch, R.R.; Bowers, R.L.; Holtkamp, D.; Wright, B.L.</p> <p>1998-10-19</p> <p>Recently Lee and Preston have proposed to use magnetic implosions as a new method for measuring material strength in a regime of large <span class="hlt">strains</span> and high <span class="hlt">strain</span> <span class="hlt">rates</span> inaccessible to previously established techniques. By its shockless nature, this method avoids the intrinsic difficulties associated with an earlier approach using high explosives. The authors illustrate how the stress-<span class="hlt">strain</span> relation for an imploding liner can be obtained by measuring the velocity and temperature history of its inner surface. They discuss the physical requirements that lead us to a composite liner design applicable to different test materials, and also compare the code-simulated prediction with the measured data for the high <span class="hlt">strain-rate</span> experiments conducted recently at LANL. Finally, they present a novel diagnostic scheme that will enable us to remove the background in the pyrometric measurement through data reduction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890015180','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890015180"><span id="translatedtitle">Pressure-<span class="hlt">strain-rate</span> events in homogeneous turbulent shear flow</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brasseur, James G.; Lee, Moon J.</p> <p>1988-01-01</p> <p>A detailed study of the intercomponent energy transfer processes by the pressure-<span class="hlt">strain-rate</span> in homogeneous turbulent shear flow is presented. Probability density functions (pdf's) and contour plots of the rapid and slow pressure-<span class="hlt">strain-rate</span> show that the energy transfer processes are extremely peaky, with high-magnitude events dominating low-magnitude fluctuations, as reflected by very high flatness factors of the pressure-<span class="hlt">strain-rate</span>. A concept of the energy transfer class was applied to investigate details of the direction as well as magnitude of the energy transfer processes. In incompressible flow, six disjoint energy transfer classes exist. Examination of contours in instantaneous fields, pdf's and weighted pdf's of the pressure-<span class="hlt">strain-rate</span> indicates that in the low magnitude regions all six classes play an important role, but in the high magnitude regions four classes of transfer processes, dominate. The contribution to the average slow pressure-<span class="hlt">strain-rate</span> from the high magnitude fluctuations is only 50 percent or less. The relative significance of high and low magnitude transfer events is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4306125','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4306125"><span id="translatedtitle">MRI-based <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> analysis of left ventricle: a modified hierarchical transformation model</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2015-01-01</p> <p>Background Different from other indicators of cardiac function, such as ejection fraction and transmitral early diastolic velocity, myocardial <span class="hlt">strain</span> is promising to capture subtle alterations that result from early diseases of the myocardium. In order to extract the left ventricle (LV) myocardial <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> from cardiac cine-MRI, a modified hierarchical transformation model was proposed. Methods A hierarchical transformation model including the global and local LV deformations was employed to analyze the <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> of the left ventricle by cine-MRI image registration. The endocardial and epicardial contour information was introduced to enhance the registration accuracy by combining the original hierarchical algorithm with an Iterative Closest Points using Invariant Features algorithm. The hierarchical model was validated by a normal volunteer first and then applied to two clinical cases (i.e., the normal volunteer and a diabetic patient) to evaluate their respective function. Results Based on the two clinical cases, by comparing the displacement fields of two selected landmarks in the normal volunteer, the proposed method showed a better performance than the original or unmodified model. Meanwhile, the comparison of the radial <span class="hlt">strain</span> between the volunteer and patient demonstrated their apparent functional difference. Conclusions The present method could be used to estimate the LV myocardial <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> during a cardiac cycle and thus to quantify the analysis of the LV motion function. PMID:25602778</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AIPC..845.1511B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AIPC..845.1511B"><span id="translatedtitle">Dynamic Behaviour of Birch and Sequoia at High <span class="hlt">Strain</span> <span class="hlt">Rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bragov, A. M.; Lomunov, A. K.; Sergeichev, I. V.; Gray, G. T.</p> <p>2006-07-01</p> <p>This paper presents results of the dynamic mechanical response of for two structural woods, i.e. birch and sequoia. Monotonic and cyclic compression testing at room temperature of these materials was performed using a modified Kolsky method; a 20-mm diameter split-Hopkinson pressure bar (SHPB). The birch and sequoia specimens were loaded parallel and orthogonal to the grain of the wood, as well as, at other angles relative to the wood grain. The dynamic mechanical behavior of the two woods was measured as a function of loading orientation under a uniaxial stress state as well as under circumferential confinement using a collar surrounding the sample to quantify the <span class="hlt">effect</span> of lateral confinement on mechanical behavior. The loading and unloading responses of both woods were found to exhibit nonlinear behavior and a strong dependency on the <span class="hlt">strain</span> <span class="hlt">rate</span> of loading. The dynamic stress-<span class="hlt">strain</span> responses of the birch and sequoia showed a strong influence of grain orientation of the flow stress and fracture behavior. Examination of the damage evolution and fracture responses of the birch and sequoia displayed a strong dependence on grain orientation. Cyclic dynamic loading data, obtained using a modification of the original SHPB testing method, is also presented for the two structural woods studied. In addition to the SHPB tests, plane-wave Shockwave loading experiments were conducted and the shock adiabates for birch was obtained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AIPC.1300..166M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AIPC.1300..166M"><span id="translatedtitle">Mechanical Solder Characterisation Under High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meier, Karsten; Roellig, Mike; Wiese, Steffen; Wolter, Klaus-Juergen</p> <p>2010-11-01</p> <p>Using a setup for high <span class="hlt">strain</span> <span class="hlt">rate</span> tensile experiments the mechanical behavior of two lead-free tin based solders is investigated. The first alloy is SnAg1.3Cu0.5Ni. The second alloy has a higher silver content but no addition of Ni. Solder joints are the main electrical, thermal and mechanical interconnection technology on the first and second interconnection level. With the recent rise of 3D packaging technologies many novel interconnection ideas are proposed with innovative or visionary nature. Copper pillar, stud bump, intermetallic (SLID) and even spring like joints are presented in a number of projects. However, soldering will remain one of the important interconnect technologies. Knowing the mechanical properties of solder joints is important for any reliability assessment, especially when it comes to vibration and mechanical shock associated with mobile applications. Taking the ongoing miniaturization and linked changes in solder joint microstructure and mechanical behavior into account the need for experimental work on that issue is not satisfied. The tests are accomplished utilizing miniature bulk specimens to match the microstructure of real solder joints as close as possible. The dogbone shaped bulk specimens have a crucial diameter of 1 mm, which is close to BGA solder joints. Experiments were done in the <span class="hlt">strain</span> <span class="hlt">rate</span> range from 20 s-1 to 600 s-1. Solder strengthening has been observed with increased <span class="hlt">strain</span> <span class="hlt">rate</span> for both SAC solder alloys. The yield stress increases by about 100% in the investigated <span class="hlt">strain</span> <span class="hlt">rate</span> range. The yield level differs strongly. A high speed camera system was used to assist the evaluation process of the stress and <span class="hlt">strain</span> data. Besides the stress and <span class="hlt">strain</span> data extracted from the experiment the ultimate fracture <span class="hlt">strain</span> is determined and the fracture surfaces are evaluated using SEM technique considering <span class="hlt">rate</span> dependency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016E%26PSL.439..129S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26PSL.439..129S"><span id="translatedtitle">Stress, <span class="hlt">strain</span> <span class="hlt">rate</span> and anisotropy in Kyushu, Japan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Savage, M. K.; Aoki, Y.; Unglert, K.; Ohkura, T.; Umakoshi, K.; Shimizu, H.; Iguchi, M.; Tameguri, T.; Ohminato, T.; Mori, J.</p> <p>2016-04-01</p> <p>Seismic anisotropy, the directional dependence of wave speeds, may be caused by stress-oriented cracks or by <span class="hlt">strain</span>-oriented minerals, yet few studies have quantitatively compared anisotropy to stress and <span class="hlt">strain</span> over large regions. Here we compare crustal stress and <span class="hlt">strain</span> <span class="hlt">rates</span> on the Island of Kyushu, Japan, as measured from inversions of focal mechanisms, GPS and shear wave splitting. Over 85,000 shear wave splitting measurements from local and regional earthquakes are obtained from the NIED network between 2004 and 2012, and on Aso, Sakurajima, Kirishima and Unzen volcano networks. <span class="hlt">Strain</span> <span class="hlt">rate</span> measurements are made from the Japanese Geonet stations. JMA-determined S arrival times processed with the MFAST shear wave splitting code measure fast polarisations (Φ), related to the orientation of the anisotropic medium and time delays (dt), related to the path length and the percent anisotropy. We apply the TESSA 2-D delay time tomography and spatial averaging code to the highest quality events, which have nearly vertical incidence angles, separating the 3455 shallow (depth < 40 km) from the 4957 deep (> = 40 km) earthquakes. Using square grids with 30 km sides for all the inversions, the best correlations are observed between splitting from shallow earthquakes and stress. Axes of maximum horizontal stress (SHmax) and Φ correlate with a coefficient c of 0.56, significant at the 99% confidence level. Their mean difference is 31.9°. Axes of maximum compressional <span class="hlt">strain</span> <span class="hlt">rate</span> and SHmax are also well aligned, with an average difference of 28°, but they do not correlate with each other, meaning that where they differ, the difference is not systematic. Anisotropy strength is negatively correlated with the stress ratio parameter determined from focal mechanism inversion (c = - 0.64; significant at the 99% confidence level). The anisotropy and stress results are consistent with stress-aligned microcracks in the crust in a dominantly strike-slip regime. Eigenvalues of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900034881&hterms=Rosemary&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DRosemary','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900034881&hterms=Rosemary&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DRosemary"><span id="translatedtitle"><span class="hlt">Effects</span> of H2O, CO2, and N2 air contaminants on critical airside <span class="hlt">strain</span> <span class="hlt">rates</span> for extinction of hydrogen-air counterflow diffusion flames</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pellett, G. L.; Northam, G. B.; Wilson, L. G.; Guerra, Rosemary</p> <p>1989-01-01</p> <p>Dish-shaped counterflow diffusion flames centered by opposing laminar jets of H2 and clean and contaminant O2/N2 mixtures in an argon bath at 1 atm were used to study the <span class="hlt">effects</span> of contaminants on critical airside <span class="hlt">strain</span>. The jet velocities for both flame extinction and restoration are found for a wide range of contaminant and O2 concentrations in the air jet. The tests are also conducted for a variety of input H2 concentrations. The results are compared with those from several other studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MMTA...48..601Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MMTA...48..601Q"><span id="translatedtitle">High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Compression of Martensitic NiTi Shape Memory Alloy at Different Temperatures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Qiu, Ying; Young, Marcus L.; Nie, Xu</p> <p>2017-02-01</p> <p>The compressive response of martensitic NiTi shape memory alloy (SMA) rods has been investigated using a modified Kolsky compression bar at various <span class="hlt">strain</span> <span class="hlt">rates</span> (400, 800, and 1200 s-1) and temperatures [room temperature and 373 K (100 °C)], i.e., in the martensitic state and in the austenitic state. SEM, DSC, and XRD were performed on NiTi SMA rod samples after high <span class="hlt">strain</span> <span class="hlt">rate</span> compression in order to reveal the influence of <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature on the microstructural evolution, phase transformation, and crystal structure. It is found that at room temperature, the critical stress increases slightly as <span class="hlt">strain</span> <span class="hlt">rate</span> increases, whereas the <span class="hlt">strain</span>-hardening <span class="hlt">rate</span> decreases. However, the critical stress under high <span class="hlt">strain</span> <span class="hlt">rate</span> compression at 373 K (100 °C) increase first and then decrease due to competing <span class="hlt">strain</span> hardening and thermal softening <span class="hlt">effects</span>. After high <span class="hlt">rate</span> compression, the microstructure of both martensitic and austenitic NiTi SMAs changes as a function of increasing <span class="hlt">strain</span> <span class="hlt">rate</span>, while the phase transformation after deformation is independent of the <span class="hlt">strain</span> <span class="hlt">rate</span> at room temperature and 373 K (100 °C). The preferred crystal plane of the martensitic NiTi SMA changes from ( 1bar{1}1 )M before compression to (111)M after compression, while the preferred plane remains the same for austenitic NiTi SMA before and after compression. Additionally, dynamic recovery and recrystallization are also observed to occur after deformation of the austenitic NiTi SMA at 373 K (100 °C). The findings presented here extend the basic understanding of the deformation behavior of NiTi SMAs and its relation to microstructure, phase transformation, and crystal structure, especially at high <span class="hlt">strain</span> <span class="hlt">rates</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/94016','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/94016"><span id="translatedtitle">High <span class="hlt">strain-rate</span> model for fiber-reinforced composites</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Aidun, J.B.; Addessio, F.L.</p> <p>1995-07-01</p> <p>Numerical simulations of dynamic uniaxial <span class="hlt">strain</span> loading of fiber-reinforced composites are presented that illustrate the wide range of deformation mechanisms that can be captured using a micromechanics-based homogenization technique as the material model in existing continuum mechanics computer programs. Enhancements to the material model incorporate high <span class="hlt">strain-rate</span> plastic response, elastic nonlinearity, and <span class="hlt">rate</span>-dependent strength degradation due to material damage, fiber debonding, and delamination. These make the model relevant to designing composite structural components for crash safety, armor, and munitions applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/626461','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/626461"><span id="translatedtitle">Low <span class="hlt">strain</span> <span class="hlt">rate</span> compression measurements of PBX 9501, PBXN-9, and MOCK 9501</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Idar, D.J.; Peterson, P.D.; Scott, P.D.; Funk, D.J.</p> <p>1997-07-01</p> <p>Low <span class="hlt">strain</span> <span class="hlt">rate</span> (10{sup -3} to 10{sup -1} 1/s) compression measurements have been obtained on three different composite materials: PBX 9501, PBXN-9, and a sugar mock of PBX 9501. These measurements expand on earlier efforts to identify the behavior of PBX 9501 and sugar mocks at different <span class="hlt">rates</span>, aspect ratios (L/d) and temperatures. PBX 9501 samples at three different L/d`s were <span class="hlt">strained</span> at the same <span class="hlt">rate</span> to evaluate Lid <span class="hlt">effects</span> on the stress <span class="hlt">strain</span> parameters. Extensometer and <span class="hlt">strain</span> gage data obtained with these measurements were also compared for precision. PBXN-9 data were obtained at two different L/ds, two different temperatures, and at three different <span class="hlt">rates</span>. The PBXN-9 data exhibit similar trends to other energetic materials data, i.e. 1) increased ultimate compressive strength and modulus of elasticity with either an increase in <span class="hlt">strain</span> <span class="hlt">rate</span>, or decrease in temperature, and 2) small changes in the <span class="hlt">strain</span> at maximum stress with changes in temperature or <span class="hlt">strain</span> <span class="hlt">rate</span>. A comparison of the PBXN-9 data to the PBX 9501 data shows that both begin to fail at comparable <span class="hlt">strains</span>, however the PBXN- 9 data is considerably weaker in terms of the ultimate compressive strength.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997APS..SHK..E104I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997APS..SHK..E104I"><span id="translatedtitle">Low <span class="hlt">Strain</span> <span class="hlt">Rate</span> Compression Measurements of PBX 9501, PBXN-9, and Mock 9501</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Idar, D. J.; Peterson, P. D.; Scott, P. D.; Funk, D. J.</p> <p>1997-07-01</p> <p>Low <span class="hlt">strain</span> <span class="hlt">rate</span> (10-3 to 10-1 1/s) compression measurements have been obtained on three different composite materials: PBX 9501, PBXN-9, and a sugar mock of PBX 9501. These measurements expand on earlier efforts to identify the behavior of PBX 9501 and sugar mocks at different <span class="hlt">rates</span>, aspect ratios (L/d) and temperatures. PBX 9501 samples at three different L/d's were <span class="hlt">strained</span> at the same <span class="hlt">rate</span> to evalute the <span class="hlt">effect</span> of aspect ration on stress-<span class="hlt">strain</span> parameters. Extensometer and <span class="hlt">strain</span> gage data obtained with these measurements were also compared for precision. PBXN-9 data were obtained at two different L/d's, two different temperatures, an at three different <span class="hlt">rates</span>. The PBXN-9 data exhibit similar trends to other energetic materials data, i.e. 1) increased ultimate compressive strength and modulus of elasticity with either an increase in <span class="hlt">strain</span> <span class="hlt">rate</span>, or decrease in temperature, and 2) small changes in the <span class="hlt">strain</span> at maximum stress with changes in temperature or <span class="hlt">strain</span> <span class="hlt">rate</span>. A comparison of the PBXN-9 data to the PBX 9501 data shows that both begin to fail at comparable <span class="hlt">strains</span>. However, PBXN-9 is considerably weaker in terms of the ultimate compressive strength.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900031313&hterms=Rate+Displacement&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DRate%2BDisplacement','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900031313&hterms=Rate+Displacement&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DRate%2BDisplacement"><span id="translatedtitle">A simplified approach to <span class="hlt">strain</span> energy release <span class="hlt">rate</span> computations for interlaminar fracture of composites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Armanios, Erian A.; Rehfield, Lawrence W.</p> <p>1989-01-01</p> <p>A simple approach for the <span class="hlt">strain</span> energy release <span class="hlt">rate</span> computations based on the finite element method and a singular fitting model is presented. The model uses the stress and displacement distributions at the delamination front. The method is applied to a mixed-mode double cracked-lap-shear composite configuration. The <span class="hlt">strain</span> energy release <span class="hlt">rate</span> components predicted by the model are compared with the finite element crack-closure method. The <span class="hlt">effect</span> of the mesh size on the stress and displacement distribution is isolated. The <span class="hlt">strain</span> energy release <span class="hlt">rates</span> predicted by relatively coarse mesh sizes are in good agreement with the finite element crack closure method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030112671','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030112671"><span id="translatedtitle">Analytical Modeling of the High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Deformation of Polymer Matrix Composites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldberg, Robert K.; Roberts, Gary D.; Gilat, Amos</p> <p>2003-01-01</p> <p>The results presented here are part of an ongoing research program to develop <span class="hlt">strain</span> <span class="hlt">rate</span> dependent deformation and failure models for the analysis of polymer matrix composites subject to high <span class="hlt">strain</span> <span class="hlt">rate</span> impact loads. State variable constitutive equations originally developed for metals have been modified in order to model the nonlinear, <span class="hlt">strain</span> <span class="hlt">rate</span> dependent deformation of polymeric matrix materials. To account for the <span class="hlt">effects</span> of hydrostatic stresses, which are significant in polymers, the classical 5 plasticity theory definitions of <span class="hlt">effective</span> stress and <span class="hlt">effective</span> plastic <span class="hlt">strain</span> are modified by applying variations of the Drucker-Prager yield criterion. To verify the revised formulation, the shear and tensile deformation of a representative toughened epoxy is analyzed across a wide range of <span class="hlt">strain</span> <span class="hlt">rates</span> (from quasi-static to high <span class="hlt">strain</span> <span class="hlt">rates</span>) and the results are compared to experimentally obtained values. For the analyzed polymers, both the tensile and shear stress-<span class="hlt">strain</span> curves computed using the analytical model correlate well with values obtained through experimental tests. The polymer constitutive equations are implemented within a strength of materials based micromechanics method to predict the nonlinear, <span class="hlt">strain</span> <span class="hlt">rate</span> dependent deformation of polymer matrix composites. In the micromechanics, the unit cell is divided up into a number of independently analyzed slices, and laminate theory is then applied to obtain the <span class="hlt">effective</span> deformation of the unit cell. The composite mechanics are verified by analyzing the deformation of a representative polymer matrix composite (composed using the representative polymer analyzed for the correlation of the polymer constitutive equations) for several fiber orientation angles across a variety of <span class="hlt">strain</span> <span class="hlt">rates</span>. The computed values compare favorably to experimentally obtained results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1003589','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1003589"><span id="translatedtitle">Soft Tissue <span class="hlt">Strain</span> <span class="hlt">Rates</span> in Side-Blast Incidents</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2014-11-02</p> <p>for Human Head Impacts. Proceedings ASME Biomechanics of Human Factors Conference. [22] Hannon P, Knapp K. 2006. Forensic Biomechanics. Lawyers...J, Song, B, Pintar, F, Yoganandan N, Chen W, Gennarelli TA. 2008. How to test brain and brain simulant at ballistic and blast <span class="hlt">strain</span> <span class="hlt">rates</span>. Rocky</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/932063','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/932063"><span id="translatedtitle">High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Tensile Testing of DOP-26 Iridium</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Schneibel, Joachim H; Carmichael Jr, Cecil Albert; George, Easo P</p> <p>2007-11-01</p> <p>The iridium alloy DOP-26 was developed through the Radioisotope Power Systems Program in the Office of Nuclear Energy of the Department of Energy. It is used for clad vent set cups containing radioactive fuel in radioisotope thermoelectric generator (RTG) heat sources which provide electric power for spacecraft. This report describes mechanical testing results for DOP-26. Specimens were given a vacuum recrystallization anneal of 1 hour at 1375 C and tested in tension in orientations parallel and perpendicular to the rolling direction of the sheet from which they were fabricated. The tests were performed at temperatures ranging from room temperature to 1090 C and <span class="hlt">strain</span> <span class="hlt">rates</span> ranging from 1 x 10{sup -3} to 50 s{sup -1}. Room temperature testing was performed in air, while testing at elevated temperatures was performed in a vacuum better than 1 x 10{sup -4} Torr. The yield stress (YS) and the ultimate tensile stress (UTS) decreased with increasing temperature and increased with increasing <span class="hlt">strain</span> <span class="hlt">rate</span>. Between 600 and 1090 C, the ductility showed a slight increase with increasing temperature. Within the scatter of the data, the ductility did not depend on the <span class="hlt">strain</span> <span class="hlt">rate</span>. The reduction in area (RA), on the other hand, decreased with increasing <span class="hlt">strain</span> <span class="hlt">rate</span>. The YS and UTS values did not differ significantly for the longitudinal and transverse specimens. The ductility and RA values of the transverse specimens were marginally lower than those of the longitudinal specimens.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUSM.G21B..02M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUSM.G21B..02M"><span id="translatedtitle">Interactive Web Interface to the Global <span class="hlt">Strain</span> <span class="hlt">Rate</span> Map Project</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meertens, C. M.; Estey, L.; Kreemer, C.; Holt, W.</p> <p>2004-05-01</p> <p>An interactive web interface allows users to explore the results of a global <span class="hlt">strain</span> <span class="hlt">rate</span> and velocity model and to compare them to other geophysical observations. The most recent model, an updated version of Kreemer et al., 2003, has 25 independent rigid plate-like regions separated by deformable boundaries covered by about 25,000 grid areas. A least-squares fit was made to 4900 geodetic velocities from 79 different geodetic studies. In addition, Quaternary fault slip <span class="hlt">rate</span> data are used to infer geologic <span class="hlt">strain</span> <span class="hlt">rate</span> estimates (currently only for central Asia). Information about the style and direction of expected <span class="hlt">strain</span> <span class="hlt">rate</span> is inferred from the principal axes of the seismic <span class="hlt">strain</span> <span class="hlt">rate</span> field. The current model, as well as source data, references and an interactive map tool, are located at the International Lithosphere Program (ILP) "A Global <span class="hlt">Strain</span> <span class="hlt">Rate</span> Map (ILP II-8)" project website: http://www-world-<span class="hlt">strain</span>-map.org. The purpose of the ILP GSRM project is to provide new information from this, and other investigations, that will contribute to a better understanding of continental dynamics and to the quantification of seismic hazards. A unique aspect of the GSRM interactive Java map tool is that the user can zoom in and make custom views of the model grid and results for any area of the globe selecting <span class="hlt">strain</span> <span class="hlt">rate</span> and style contour plots and principal axes, observed and model velocity fields in specified frames of reference, and geologic fault data. The results can be displayed with other data sets such Harvard CMT earthquake focal mechanisms, stress directions from the ILP World Stress Map Project, and topography. With the GSRM Java map tool, the user views custom maps generated by a Generic Mapping Tool (GMT) server. These interactive capabilities greatly extend what is possible to present in a published paper. A JavaScript version, using pre-constructed maps, as well as a related information site have also been created for broader education and outreach access</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1713k0001H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1713k0001H"><span id="translatedtitle">Determination of the <span class="hlt">strain</span> <span class="hlt">rate</span> dependent thermal softening behavior of thermoplastic materials for crash simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hopmann, Christian; Klein, Jan; Schöngart, Maximilian</p> <p>2016-03-01</p> <p>Thermoplastic materials are increasingly used as a light weight replacement for metal, especially in automotive applications. Typical examples are frontends and bumpers. The loads on these structures are very often impulsive, for example in a crash situation. A high <span class="hlt">rate</span> of loading causes a high <span class="hlt">strain</span> <span class="hlt">rate</span> in the material which has a major impact on the mechanical behavior of thermoplastic materials. The stiffness as well as the rigidity of polymers increases to higher <span class="hlt">strain</span> <span class="hlt">rates</span>. The increase of the mechanical properties is superimposed at higher <span class="hlt">rates</span> of loading by another <span class="hlt">effect</span> which works reducing on stiffness and rigidity, the increase of temperature caused by plastic deformation. The mechanical behavior of thermoplastic materials is influenced by temperature opposing to <span class="hlt">strain</span> <span class="hlt">rate</span>. The stiffness and rigidity are decreased to higher values of temperature. The <span class="hlt">effect</span> of thermal softening on thermoplastic materials is investigated at IKV. For this purpose high-speed tensile tests are performed on a blend, consisting of Polybutylenterephthalate (PBT) and Polycarbonate (PC). In preliminary investigations the <span class="hlt">effects</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> on the thermomechanical behavior of thermoplastic materials was studied by different authors. Tensile impact as well as split Hopkinson pressure bar (SHPB) tests were conducted in combination with high-speed temperature measurement, though, the authors struggled especially with temperature measurement. This paper presents an approach which uses high-speed <span class="hlt">strain</span> measurement to transpire the link between <span class="hlt">strain</span>, <span class="hlt">strain</span> <span class="hlt">rate</span> and thermal softening as well as the interdependency between <span class="hlt">strain</span> hardening and thermal softening. The results show a superimposition of <span class="hlt">strain</span> hardening and thermal softening, which is consistent to preliminary investigations. The advantage of the presented research is that the results can be used to calibrate damage and material models to perform mechanical simulations using Finite Element Analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JOM....68g1861B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JOM....68g1861B"><span id="translatedtitle">Quasi-Static and High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Compressive Response of Injection-Molded Cenosphere/HDPE Syntactic Foam</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bharath Kumar, B. R.; Singh, Ashish Kumar; Doddamani, Mrityunjay; Luong, Dung D.; Gupta, Nikhil</p> <p>2016-07-01</p> <p>High <span class="hlt">strain</span> <span class="hlt">rate</span> compressive properties of high-density polyethylene (HDPE) matrix syntactic foams containing cenosphere filler are investigated. Thermoplastic matrix syntactic foams have not been studied extensively for high <span class="hlt">strain</span> <span class="hlt">rate</span> deformation response despite interest in them for lightweight underwater vehicle structures and consumer products. Quasi-static compression tests are conducted at 10-4 s-1, 10-3 s-1 and 10-2 s-1 <span class="hlt">strain</span> <span class="hlt">rates</span>. Further, a split-Hopkinson pressure bar is utilized for characterizing syntactic foams for high <span class="hlt">strain</span> <span class="hlt">rate</span> compression. The compressive strength of syntactic foams is higher than that of HDPE resin at the same <span class="hlt">strain</span> <span class="hlt">rate</span>. Yield strength shows an increasing trend with <span class="hlt">strain</span> <span class="hlt">rate</span>. The average yield strength values at high <span class="hlt">strain</span> <span class="hlt">rates</span> are almost twice the values obtained at 10-4 s-1 for HDPE resin and syntactic foams. Theoretical models are used to estimate the <span class="hlt">effectiveness</span> of cenospheres in reinforcing syntactic foams.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15005327','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15005327"><span id="translatedtitle">Modeling Large-<span class="hlt">Strain</span>, High-<span class="hlt">Rate</span> Deformation in Metals</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lesuer, D R; Kay, G J; LeBlanc, M M</p> <p>2001-07-20</p> <p>The large <span class="hlt">strain</span> deformation response of 6061-T6 and Ti-6Al-4V has been evaluated over a range in <span class="hlt">strain</span> <span class="hlt">rates</span> from 10{sup -4} s{sup -1} to over 10{sup 4} s{sup -1}. The results have been used to critically evaluate the strength and damage components of the Johnson-Cook (JC) material model. A new model that addresses the shortcomings of the JC model was then developed and evaluated. The model is derived from the <span class="hlt">rate</span> equations that represent deformation mechanisms active during moderate and high <span class="hlt">rate</span> loading. Another model that accounts for the influence of void formation on yield and flow behavior of a ductile metal (the Gurson model) was also evaluated. The characteristics and predictive capabilities of these models are reviewed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920011638','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920011638"><span id="translatedtitle">High <span class="hlt">strain</span> <span class="hlt">rate</span> properties of angle-ply composite laminates, part 3</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Daniel, I. M.</p> <p>1991-01-01</p> <p>Angle-ply graphite/epoxy and graphite/S-glass/epoxy laminates were characterized in uniaxial tension at <span class="hlt">strain</span> <span class="hlt">rates</span> ranging from quasi-static to over 500 s(sup -1). Laminate ring specimens of +/-15(sub 2s), +/-22.5(sub 2s), +/-30(sub 2s), +/-45(sub 2s), +/-60(sub 2s), +/-67.5(sub 2s), and +/-75(sub 2s) degree layups were loaded under internal pressure. Results were presented in the form of stress-<span class="hlt">strain</span> curves to failure. Properties determined included moduli, Poisson's ratios, strength, and ultimate <span class="hlt">strain</span>. In all seven laminates for the two materials tested the modulus and strength increase with <span class="hlt">strain</span> <span class="hlt">rate</span>. The <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> varies with layup, being lowest for the fiber dominated +/-15(sub 2s) degree laminates and highest for the matrix dominated +/-75(sub 2s) degree laminates. The highest increments over the static values are 10 to 25 percent for the +/-15(sub 2s) degree layup and 200 to 275 percent for the +/-75(sub 2s) degree layup. Ultimate <span class="hlt">strains</span> do not show any significant trends with <span class="hlt">strain</span> <span class="hlt">rate</span>. In almost all cases the ultimate <span class="hlt">strain</span> values are within +/-20 percent of the mean value and in half of the cases the deviation from the mean are less than 10 percent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004AGUFM.G21A0101Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004AGUFM.G21A0101Z"><span id="translatedtitle">A Comparison of Geodetic <span class="hlt">Strain</span> <span class="hlt">Rates</span> With Earthquake Moment Tensors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhu, W.; Holt, W. E.</p> <p>2004-12-01</p> <p>In this paper we compare the global model from interpolation of GPS data with the global model inferred from earthquake moment tensors. We use the Harvard CMT catalog to calculate moment <span class="hlt">rates</span> based on 3 assumptions: a. we assume earthquakes are self-similar; b. we assume a uniform Beta value of the Gutenberg-Richter distribution; c. we assume that all of the long-term <span class="hlt">strain</span> is accommodated seismically. If these assumptions are correct then the seismicity <span class="hlt">rate</span> is proportional to the tectonic moment <span class="hlt">rate</span>. We then inferred a long-term moment <span class="hlt">rate</span> tensor field estimate for all plate boundary zones from which we inferred a long-term seismic <span class="hlt">strain</span> <span class="hlt">rate</span> estimate. Using this estimate we solved for a self-consistent kinematic global solution (motions of rigid spherical caps and motions within plate boundary zones) using bi-cubic spline interpolation of the inferred <span class="hlt">strain</span> <span class="hlt">rates</span>. We tested the above assumptions by comparing the global kinematic model obtained from earthquake data with a global model inferred from interpolation of space geodetic data [Kreemer et al., 2003]. A comparison between the two models shows good agreement for motion directions of the North American, and Eurasian plates and for the plate boundary zones within these regions (e.g., Tibet). Problems arise, and our assumptions break down, for plates adjacent to fast spreading ridges where divergence of plates appears to be accommodated aseismically. We next investigated the correlation of <span class="hlt">strain</span> <span class="hlt">rate</span> tensor inferred from the interpolation of GPS observations within deforming Asia with the earthquake moment tensors, using both elastic and viscous rheologies. Our solutions satisfy the force balance equations for a given rheology. Our goal for this exercise is to investigate whether the interseismic signal, inferred from GPS, correlates better with moment tensor style for an elastic rheology as opposed to a viscous rheology. Results to date suggest that the viscous models only provide a better agreement</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007JSG....29.1301O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007JSG....29.1301O"><span id="translatedtitle">Reaction weakening and emplacement of crystalline thrusts: Diffusion control on reaction <span class="hlt">rate</span> and <span class="hlt">strain</span> <span class="hlt">rate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>O'Hara, Kieran</p> <p>2007-08-01</p> <p>In the southern Appalachians, the Blue Ridge-Piedmont crystalline thrust sheet was emplaced onto low-grade Late Precambrian and Paleozoic sedimentary rocks in the footwall along a basal detachment consisting of phyllosilicate-rich mylonites (phyllonites). The phyllonites developed first by mechanical breakdown of feldspar followed by chemical breakdown to white mica in the presence of a pore fluid. Diffusion of solute in the pore fluid is the <span class="hlt">rate</span> limiting step in controlling reaction <span class="hlt">rate</span> and also the <span class="hlt">strain</span> <span class="hlt">rate</span>. Assuming solute diffusion follows the Stokes-Einstein equation, the shear <span class="hlt">strain</span> <span class="hlt">rate</span> is given by ⅆγ/ⅆt=2ωkT/5ηrx for shear stress ≥20 MPa, where n is a constant, ω is a geometric factor, k is Boltzmann's constant, T is absolute temperature, η is water viscosity, r is the atomic radius of the diffusing species, and x is the diffusion distance. A bulk diffusion coefficient in the range of ˜10 -10 to 10 -12 m 2/s over distances of 10-100 m results in <span class="hlt">strain</span> <span class="hlt">rates</span> of 10 -14 to 10 -13 s -1 in the temperature range 200-400 °C. It is concluded that greenschist grade crystalline thrust sheets develop on pre-existing basement faults that become weak during reaction softening and localize into high <span class="hlt">strain</span> phyllonite zones in which pore fluid diffusion controls reaction <span class="hlt">rate</span> and <span class="hlt">strain</span> <span class="hlt">rate</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27810728','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27810728"><span id="translatedtitle">Material properties of bovine intervertebral discs across <span class="hlt">strain</span> <span class="hlt">rates</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Newell, Nicolas; Grigoriadis, Grigorios; Christou, Alexandros; Carpanen, Diagarajen; Masouros, Spyros D</p> <p>2017-01-01</p> <p>The intervertebral disc (IVD) is a complex structure responsible for distributing compressive loading to adjacent vertebrae and allowing the vertebral column to bend and twist. To study the mechanical behaviour of individual components of the IVD, it is common for specimens to be dissected away from their surrounding tissues for mechanical testing. However, disrupting the continuity of the IVD to obtain material properties of each component separately may result in erroneous values. In this study, an inverse finite element (FE) modelling optimisation algorithm has been used to obtain material properties of the IVD across <span class="hlt">strain</span> <span class="hlt">rates</span>, therefore bypassing the need to harvest individual samples of each component. Uniaxial compression was applied to ten fresh-frozen bovine intervertebral discs at <span class="hlt">strain</span> <span class="hlt">rates</span> of 10(-3)-1/s. The experimental data were fed into the inverse FE optimisation algorithm and each experiment was simulated using the subject specific FE model of the respective specimen. A sensitivity analysis revealed that the IVD's response was most dependent upon the Young's modulus (YM) of the fibre bundles and therefore this was chosen to be the parameter to optimise. Based on the obtained YM values for each test corresponding to a different <span class="hlt">strain</span> <span class="hlt">rate</span> (ε̇), the following relationship was derived:YM=35.5lnε̇+527.5. These properties can be used in finite element models of the IVD that aim to simulate spinal biomechanics across loading <span class="hlt">rates</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6537816','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6537816"><span id="translatedtitle">Influence of <span class="hlt">strain</span> <span class="hlt">rate</span> on the structure/property of Ti-48Al-1V</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gray, G.T. III.</p> <p>1990-01-01</p> <p>While the influence of <span class="hlt">strain</span> <span class="hlt">rate</span> on the structure/property response of pure titanium and a variety of titanium alloys has been extensively studied, the <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> on the stress-<span class="hlt">strain</span> and deformation response of titanium aluminides remains largely unknown. In this paper, a preliminary study of the <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature on the substructure evolution and mechanical response of a (48Al-1V)TiAl alloy is presented. The compressive true stress-true <span class="hlt">strain</span> response of Ti-48Al-1V was found to depend on both the applied <span class="hlt">strain</span> <span class="hlt">rate</span>, varied between 0.001 and 7500 s{sup {minus}1}, and the test temperature, varied between 25 and 700{degree}C. The <span class="hlt">rate</span> of <span class="hlt">strain</span> hardening in Ti-48Al-1V is seen to increase with increasing <span class="hlt">strain</span> <span class="hlt">rate</span>. The substructure evolution of Ti-48Al-1V was observed to depend on the applied <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature of deformation. The substructure of Ti-48Al-1V deformed to {var epsilon} = 0.20 at 0.001 s{sup {minus}1} at 25{degree}C was seen to consist of predominately random dislocation debris and isolated grains containing a high density of stacking faults. The majority of the dislocations appear to be (111) 1/2{l angle}110{r angle} unit type ordinary dislocations which is consistent with previous observations on Ti-48Al. Increasing the <span class="hlt">rate</span> of deformation at room temperature to 75000 s{sup {minus}1} is seen to increase the density of deformation twins and the overall random dislocation debris density. The substructure of Ti-48Al-1V deformed a at high-<span class="hlt">strain-rate</span> at elevated temperatures was seen to be quite similar to that observed following high-<span class="hlt">rate</span> deformation at room temperature except for an even higher incidence of twinning. The defect generation and the <span class="hlt">rate</span> sensitivity of TiAl are discussed as a function of <span class="hlt">strain</span> <span class="hlt">rate</span> and contrasted to that observed in conventional titanium alloys. 34 refs., 8 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010047399','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010047399"><span id="translatedtitle">Implementation of Fiber Substructuring Into <span class="hlt">Strain</span> <span class="hlt">Rate</span> Dependent Micromechanics Analysis of Polymer Matrix Composites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldberg, Robert K.</p> <p>2001-01-01</p> <p>A research program is in progress to develop <span class="hlt">strain</span> <span class="hlt">rate</span> dependent deformation and failure models for the analysis of polymer matrix composites subject to impact loads. Previously, <span class="hlt">strain</span> <span class="hlt">rate</span> dependent inelastic constitutive equations developed to model the polymer matrix were incorporated into a mechanics of materials based micromechanics method. In the current work, the micromechanics method is revised such that the composite unit cell is divided into a number of slices. Micromechanics equations are then developed for each slice, with laminate theory applied to determine the elastic properties, <span class="hlt">effective</span> stresses and <span class="hlt">effective</span> inelastic <span class="hlt">strains</span> for the unit cell. Verification studies are conducted using two representative polymer matrix composites with a nonlinear, <span class="hlt">strain</span> <span class="hlt">rate</span> dependent deformation response. The computed results compare well to experimentally obtained values.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000121259','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000121259"><span id="translatedtitle">Implementation of Laminate Theory Into <span class="hlt">Strain</span> <span class="hlt">Rate</span> Dependent Micromechanics Analysis of Polymer Matrix Composites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldberg, Robert K.</p> <p>2000-01-01</p> <p>A research program is in progress to develop <span class="hlt">strain</span> <span class="hlt">rate</span> dependent deformation and failure models for the analysis of polymer matrix composites subject to impact loads. Previously, <span class="hlt">strain</span> <span class="hlt">rate</span> dependent inelastic constitutive equations developed to model the polymer matrix were implemented into a mechanics of materials based micromechanics method. In the current work, the computation of the <span class="hlt">effective</span> inelastic <span class="hlt">strain</span> in the micromechanics model was modified to fully incorporate the Poisson <span class="hlt">effect</span>. The micromechanics equations were also combined with classical laminate theory to enable the analysis of symmetric multilayered laminates subject to in-plane loading. A quasi-incremental trapezoidal integration method was implemented to integrate the constitutive equations within the laminate theory. Verification studies were conducted using an AS4/PEEK composite using a variety of laminate configurations and <span class="hlt">strain</span> <span class="hlt">rates</span>. The predicted results compared well with experimentally obtained values.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJWC..9404030J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9404030J"><span id="translatedtitle"><span class="hlt">Strain-rate</span> dependence for Ni/Al hybrid foams</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jung, Anne; Larcher, Martin; Jirousek, Ondrej; Koudelka, Petr; Solomos, George</p> <p>2015-09-01</p> <p>Shock absorption often needs stiff but lightweight materials that exhibit a large kinetic energy absorption capability. Open-cell metal foams are artificial structures, which due to their plateau stress, including a strong hysteresis, can in principle absorb large amounts of energy. However, their plateau stress is too low for many applications. In this study, we use highly novel and promising Ni/Al hybrid foams which consist of standard, open-cell aluminium foams, where nanocrystalline nickel is deposited by electrodeposition as coating on the strut surface. The mechanical behaviour of cellular materials, including their behaviour under higher <span class="hlt">strain-rates</span>, is governed by their microstructure due to the properties of the strut material, pore/strut geometry and mass distribution over the struts. Micro-inertia <span class="hlt">effects</span> are strongly related to the microstructure. For a conclusive model, the exact real microstructure is needed. In this study a micro-focus computer tomography (μCT) system has been used for the analysis of the microstructure of the foam samples and for the development of a microstructural Finite Element (micro-FE) mesh. The microstructural FE models have been used to model the mechanical behaviour of the Ni/Al hybrid foams under dynamic loading conditions. The simulations are validated by quasi-static compression tests and dynamic split Hopkinson pressure bar tests.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JPhCS.500r2036R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JPhCS.500r2036R"><span id="translatedtitle">High <span class="hlt">strain</span> <span class="hlt">rate</span> fracture behaviour of fused silica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruggiero, A.; Iannitti, G.; Testa, G.; Limido, J.; Lacome, J. L.; Olovsson, L.; Ferraro, M.; Bonora, N.</p> <p>2014-05-01</p> <p>Fused silica is a high purity synthetic amorphous silicon dioxide characterized by low thermal expansion coefficient, excellent optical qualities and exceptional transmittance over a wide spectral range. Because of its wide use in the military industry as window material, it may be subjected to high-energy ballistic impacts. Under such dynamic conditions, post-yield response of the ceramic as well as the <span class="hlt">strain</span> <span class="hlt">rate</span> related <span class="hlt">effects</span> become significant and should be accounted for in the constitutive modelling. In this study, the Johnson-Holmquist (J-H) model parameters have been identified by inverse calibration technique, on selected validation test configurations, according to the procedure described hereafter. Numerical simulations were performed with LS-DYNA and IMPETUS-FEA, a general non-linear finite element software which offers NURBS finite element technology for the simulation of large deformation and fracture in materials. In order to overcome numerical drawbacks associated with element erosion, a modified version of the J-H model is proposed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013APS..SHK.V6002T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APS..SHK.V6002T"><span id="translatedtitle">High <span class="hlt">strain</span> <span class="hlt">rate</span> behavior of pure metals at elevated temperature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Testa, Gabriel; Bonora, Nicola; Ruggiero, Andrew; Iannitti, Gianluca; Domenico, Gentile</p> <p>2013-06-01</p> <p>In many applications and technology processes, such as stamping, forging, hot working etc., metals and alloys are subjected to elevated temperature and high <span class="hlt">strain</span> <span class="hlt">rate</span> deformation process. Characterization tests, such as quasistatic and dynamic tension or compression test, and validation tests, such as Taylor impact and DTE - dynamic tensile extrusion -, provide the experimental base of data for constitutive model validation and material parameters identification. Testing material at high <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature requires dedicated equipment. In this work, both tensile Hopkinson bar and light gas gun where modified in order to allow material testing under sample controlled temperature conditions. Dynamic tension tests and Taylor impact tests, at different temperatures, on high purity copper (99.98%), tungsten (99.95%) and 316L stainless steel were performed. The accuracy of several constitutive models (Johnson and Cook, Zerilli-Armstrong, etc.) in predicting the observed material response was verified by means of extensive finite element analysis (FEA).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PMM...116..592C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PMM...116..592C"><span id="translatedtitle">Elastoplastic behavior of copper upon high-<span class="hlt">strain-rate</span> deformation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chembarisova, R. G.</p> <p>2015-06-01</p> <p>The deformation behavior of copper under conditions of high-<span class="hlt">strain-rate</span> deformation has been investigated based on the model of elastoplastic medium with allowance for the kinetics of plastic deformation. Data have been obtained on the evolution of the dislocation subsystem, namely, on the average dislocation density, density of mobile dislocations, velocity of dislocation slip, concentration of deformation-induced vacancies, and density of twins. The coefficient of the annihilation of screw dislocations has been estimated depending on pressure and temperature. It has been shown that severe shear stresses that arise upon high-<span class="hlt">strain-rate</span> deformation can lead to a significant increase in the concentration of vacancies. The time of the dislocation annihilation upon their nonconservative motion has been estimated. It has been shown that this time is much greater than the time of the deformation process in the samples, which makes it possible to exclude the annihilation of dislocations upon their nonconservative motion from the active mechanisms of deformation.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA528977','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA528977"><span id="translatedtitle">Finite <span class="hlt">Strain</span> Behavior of Polyurea for a Wide Range of <span class="hlt">Strain</span> <span class="hlt">Rates</span></span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2010-02-01</p> <p>R.W. (1984) Non-linear Elastic Deformations, New York, NY, Ellis Horwood Limited, p.209. [75] Othman, R. and Gary, G. (2007) "Testing aluminum alloy ...elastomer that features fast setting time as well as good chemical and fire resistance. It has also good mechanical properties such as its high...nylon bar system (700/s to 1200/s) and an aluminum bar system (2300/s to 3700/s). Lastly, the <span class="hlt">rate</span>-sensitivity for intermediate <span class="hlt">strain</span> <span class="hlt">rates</span> (10/s to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3782713','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3782713"><span id="translatedtitle">Right ventricular involvement in anterior myocardial infarction: a tissue Doppler-derived <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> study</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sonmez, Osman; Kayrak, Mehmet; Altunbas, Gokhan; Abdulhalikov, Turyan; Alihanoglu, Yusuf; Bacaksiz, Ahmet; Ozdemir, Kurtulus; Gok, Hasan</p> <p>2013-01-01</p> <p>OBJECTIVE: <span class="hlt">Strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> imaging is currently the most popular echocardiographic technique that reveals subclinical myocardial damage. There are currently no available data on this imaging method with regard to assessing right ventricular involvement in anterior myocardial infarction. Therefore, we aimed to evaluate right ventricular regional functions using a derived <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> imaging tissue Doppler method in patients who were successfully treated for their first anterior myocardial infarction. METHODS: The patient group was composed of 44 patients who had experienced their first anterior myocardial infarction and had undergone successful percutaneous coronary intervention. Twenty patients were selected for the control group. The right ventricular myocardial samplings were performed in three regions: the basal, mid, and apical segments of the lateral wall. The individual myocardial velocity, <span class="hlt">strain</span>, and <span class="hlt">strain</span> <span class="hlt">rate</span> values of each basal, mid, and apical segment were obtained. RESULTS: The right ventricular myocardial velocities of the patient group were significantly decreased with respect to all three velocities in the control group. The <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> values of the right mid and apical ventricular segments in the patient group were significantly lower than those of the control group (excluding the right ventricular basal <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span>). In addition, changes in the right ventricular mean <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> values were significant. CONCLUSION: Right ventricular involvement following anterior myocardial infarction can be assessed using tissue Doppler based <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> PMID:24141839</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26968547','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26968547"><span id="translatedtitle">The influence of acute unloading on left ventricular <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> by speckle tracking echocardiography in a porcine model.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dahle, Geir Olav; Stangeland, Lodve; Moen, Christian Arvei; Salminen, Pirjo-Riitta; Haaverstad, Rune; Matre, Knut; Grong, Ketil</p> <p>2016-05-15</p> <p>Noninvasive measurements of myocardial <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> by speckle tracking echocardiography correlate to cardiac contractile state but also to load, which may weaken their value as indices of inotropy. In a porcine model, we investigated the influence of acute dynamic preload reductions on left ventricular <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> and their relation to the pressure-conductance catheter-derived preload recruitable stroke work (PRSW) and peak positive first derivative of left ventricular pressure (LV-dP/dtmax). Speckle tracking <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> in the longitudinal, circumferential, and radial directions were measured during acute dynamic reductions of end-diastolic volume during three different myocardial inotropic states. Both <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> were sensitive to unloading of the left ventricle (P < 0.001), but the load dependency for <span class="hlt">strain</span> <span class="hlt">rate</span> was modest compared with <span class="hlt">strain</span>. Changes in longitudinal and circumferential <span class="hlt">strain</span> correlated more strongly to changes in end-diastolic volume (r = -0.86 and r = -0.72) than did radial <span class="hlt">strain</span> (r = 0.35). Longitudinal, circumferential, and radial <span class="hlt">strain</span> significantly correlated with LV-dP/dtmax (r = -0.53, r = -0.46, and r = 0.86), whereas only radial <span class="hlt">strain</span> correlated with PRSW (r = 0.55). <span class="hlt">Strain</span> <span class="hlt">rate</span> in the longitudinal, circumferential and radial direction significantly correlated with both PRSW (r = -0.64, r = -0.58, and r = 0.74) and LV-dP/dtmax (r = -0.95, r = -0.70, and r = 0.85). In conclusion, the speckle tracking echocardiography-derived <span class="hlt">strain</span> <span class="hlt">rate</span> is more robust to dynamic ventricular unloading than <span class="hlt">strain</span>. Longitudinal and circumferential <span class="hlt">strain</span> could not predict load-independent contractility. <span class="hlt">Strain</span> <span class="hlt">rates</span>, and especially in the radial direction, are good predictors of preload-independent inotropic markers derived from conductance catheter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27643676','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27643676"><span id="translatedtitle">Material properties of the heel fat pad across <span class="hlt">strain</span> <span class="hlt">rates</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Grigoriadis, Grigoris; Newell, Nicolas; Carpanen, Diagarajen; Christou, Alexandros; Bull, Anthony M J; Masouros, Spyros D</p> <p>2017-01-01</p> <p>The complex structural and material behaviour of the human heel fat pad determines the transmission of plantar loading to the lower limb across a wide range of loading scenarios; from locomotion to injurious incidents. The aim of this study was to quantify the hyper-viscoelastic material properties of the human heel fat pad across <span class="hlt">strains</span> and <span class="hlt">strain</span> <span class="hlt">rates</span>. An inverse finite element (FE) optimisation algorithm was developed and used, in conjunction with quasi-static and dynamic tests performed to five cadaveric heel specimens, to derive specimen-specific and mean hyper-viscoelastic material models able to predict accurately the response of the tissue at compressive loading of <span class="hlt">strain</span> <span class="hlt">rates</span> up to 150s(-1). The mean behaviour was expressed by the quasi-linear viscoelastic (QLV) material formulation, combining the Yeoh material model (C10=0.1MPa, C30=7MPa, K=2GPa) and Prony׳s terms (A1=0.06, A2=0.77, A3=0.02 for τ1=1ms, τ2=10ms, τ3=10s). These new data help to understand better the functional anatomy and pathophysiology of the foot and ankle, develop biomimetic materials for tissue reconstruction, design of shoe, insole, and foot and ankle orthoses, and improve the predictive ability of computational models of the foot and ankle used to simulate daily activities or predict injuries at high <span class="hlt">rate</span> injurious incidents such as road traffic accidents and underbody blast.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMNG13A..03F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMNG13A..03F"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rates</span>, stress markers and earthquake clustering (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fry, B.; Gerstenberger, M.; Abercrombie, R. E.; Reyners, M.; Eberhart-Phillips, D. M.</p> <p>2013-12-01</p> <p>The 2010-present Canterbury earthquakes comprise a well-recorded sequence in a relatively low <span class="hlt">strain-rate</span> shallow crustal region. We present new scientific results to test the hypothesis that: Earthquake sequences in low-<span class="hlt">strain</span> <span class="hlt">rate</span> areas experience high stress drop events, low-post seismic relaxation, and accentuated seismic clustering. This hypothesis is based on a physical description of the aftershock process in which the spatial distribution of stress accumulation and stress transfer are controlled by fault strength and orientation. Following large crustal earthquakes, time dependent forecasts are often developed by fitting parameters defined by Omori's aftershock decay law. In high-<span class="hlt">strain</span> <span class="hlt">rate</span> areas, simple forecast models utilizing a single p-value fit observed aftershock sequences well. In low-<span class="hlt">strain</span> <span class="hlt">rate</span> areas such as Canterbury, assumptions of simple Omori decay may not be sufficient to capture the clustering (sub-sequence) nature exhibited by the punctuated rise in activity following significant child events. In Canterbury, the moment release is more clustered than in more typical Omori sequences. The individual earthquakes in these clusters also exhibit somewhat higher stress drops than in the average crustal sequence in high-<span class="hlt">strain</span> <span class="hlt">rate</span> regions, suggesting the earthquakes occur on strong Andersonian-oriented faults, possibly juvenile or well-healed . We use the spectral ratio procedure outlined in (Viegas et al., 2010) to determine corner frequencies and Madariaga stress-drop values for over 800 events in the sequence. Furthermore, we will discuss the relevance of tomographic results of Reyners and Eberhart-Phillips (2013) documenting post-seismic stress-driven fluid processes following the three largest events in the sequence as well as anisotropic patterns in surface wave tomography (Fry et al., 2013). These tomographic studies are both compatible with the hypothesis, providing strong evidence for the presence of widespread and hydrated regional</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhA.122..897Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhA.122..897Z"><span id="translatedtitle">A parametric study on the dynamic behavior of porous bronze at various <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Yue; Hu, Jianxing; Lei, Jianyin; Wang, Zhihua; Zhao, Longmao</p> <p>2016-10-01</p> <p>An experimental investigation on the porous bronze at various <span class="hlt">strain</span> <span class="hlt">rates</span> is firstly carried out in this study to explore the <span class="hlt">effects</span> of relative density and <span class="hlt">strain</span> <span class="hlt">rate</span> in the mechanical behavior. Furthermore, a multi-parameter constitutive model of describing the <span class="hlt">rate</span>-dependent behavior for porous bronze is developed. The parameters in the constitutive model are density dependent, and the specific forms of these parameters as functions of relative density are obtained. It can be concluded from the test results and constitutive model that the high relative density leads to increase in yield strength and energy absorption capacity of the materials and the <span class="hlt">strain</span> <span class="hlt">rate</span> also has positive <span class="hlt">effects</span> on the yield strength and energy absorption capacity of porous bronze.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27956510','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27956510"><span id="translatedtitle">Measurement of fracture properties of concrete at high <span class="hlt">strain</span> <span class="hlt">rates</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rey-De-Pedraza, V; Cendón, D A; Sánchez-Gálvez, V; Gálvez, F</p> <p>2017-01-28</p> <p>An analysis of the spalling technique of concrete bars using the modified Hopkinson bar was carried out. A new experimental configuration is proposed adding some variations to previous works. An increased length for concrete specimens was chosen and finite-element analysis was used for designing a conic projectile to obtain a suitable triangular impulse wave. The aim of this initial work is to establish an experimental framework which allows a simple and direct analysis of concrete subjected to high <span class="hlt">strain</span> <span class="hlt">rates</span>. The efforts and configuration of these primary tests, as well as the selected geometry and dimensions for the different elements, have been focused to achieve a simple way of identifying the fracture position and so the tensile strength of tested specimens. This dynamic tensile strength can be easily compared with previous values published in literature giving an idea of the accuracy of the method and technique proposed and the possibility to extend it in a near future to obtain other mechanical properties such as the fracture energy. The tests were instrumented with <span class="hlt">strain</span> gauges, accelerometers and high-speed camera in order to validate the results by different ways. Results of the dynamic tensile strength of the tested concrete are presented.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high <span class="hlt">strain</span> <span class="hlt">rates</span>'.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017RSPTA.37560174R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017RSPTA.37560174R"><span id="translatedtitle">Measurement of fracture properties of concrete at high <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rey-De-Pedraza, V.; Cendón, D. A.; Sánchez-Gálvez, V.; Gálvez, F.</p> <p>2017-01-01</p> <p>An analysis of the spalling technique of concrete bars using the modified Hopkinson bar was carried out. A new experimental configuration is proposed adding some variations to previous works. An increased length for concrete specimens was chosen and finite-element analysis was used for designing a conic projectile to obtain a suitable triangular impulse wave. The aim of this initial work is to establish an experimental framework which allows a simple and direct analysis of concrete subjected to high <span class="hlt">strain</span> <span class="hlt">rates</span>. The efforts and configuration of these primary tests, as well as the selected geometry and dimensions for the different elements, have been focused to achieve a simple way of identifying the fracture position and so the tensile strength of tested specimens. This dynamic tensile strength can be easily compared with previous values published in literature giving an idea of the accuracy of the method and technique proposed and the possibility to extend it in a near future to obtain other mechanical properties such as the fracture energy. The tests were instrumented with <span class="hlt">strain</span> gauges, accelerometers and high-speed camera in order to validate the results by different ways. Results of the dynamic tensile strength of the tested concrete are presented. This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high <span class="hlt">strain</span> <span class="hlt">rates</span>'.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/975917','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/975917"><span id="translatedtitle">Single chain stochastic polymer modeling at high <span class="hlt">strain</span> <span class="hlt">rates</span>.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Harstad, E. N.; Harlow, Francis Harvey,; Schreyer, H. L.</p> <p>2001-01-01</p> <p>Our goal is to develop constitutive relations for the behavior of a solid polymer during high-<span class="hlt">strain-rate</span> deformations. In contrast to the classic thermodynamic techniques for deriving stress-<span class="hlt">strain</span> response in static (equilibrium) circumstances, we employ a statistical-mechanics approach, in which we evolve a probability distribution function (PDF) for the velocity fluctuations of the repeating units of the chain. We use a Langevin description for the dynamics of a single repeating unit and a Lioville equation to describe the variations of the PDF. Moments of the PDF give the conservation equations for a single polymer chain embedded in other similar chains. To extract single-chain analytical constitutive relations these equations have been solved for representative loading paths. By this process we discover that a measure of nonuniform chain link displacement serves this purpose very well. We then derive an evolution equation for the descriptor function, with the result being a history-dependent constitutive relation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/329541','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/329541"><span id="translatedtitle">High- and low-<span class="hlt">strain</span> <span class="hlt">rate</span> compression properties of several energetic material composites as a function of <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gray, G.T. III; Idar, D.J.; Blumenthal, W.R.; Cady, C.M.; Peterson, P.D.</p> <p>1998-12-31</p> <p>High- and low-<span class="hlt">strain</span> <span class="hlt">rate</span> compression data were obtained on several different energetic composites: PBX 9501, X0242-92-4-4, PBXN-9, as well as the polymeric binder used in PBX 9501 and X0242-92-4-4 composites. The <span class="hlt">effects</span> of energetic-to-binder ratios, different binder systems, and different energetic formulations were investigated. All the energetic composites exhibit increasing elastic modulus, E, maximum flow stresses, {sigma}{sub m}, and <span class="hlt">strain</span>-at-maximum stress, {var_epsilon}{sub m}, with increasing <span class="hlt">strain</span> <span class="hlt">rate</span> at ambient temperature. PBX 9501 displays marginally higher ultimate flow strength than X0242-92-4-4, and significantly higher ultimate compressive strength than PBXN-9 at quasi-static and dynamic <span class="hlt">strain</span> <span class="hlt">rates</span>. The failure mode of PBX 9501 and X0242-92-4-4 under high-<span class="hlt">rate</span> loading changes from a mixture of ductile binder tearing and transgranular cleavage and cracking of the HMX when tested at 20 C to transgranular brittle HMX cleavage and glassy fracture of the binder at {minus}40 C.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JMEP...23.1641S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JMEP...23.1641S"><span id="translatedtitle">Mechanical Behavior of Glidcop Al-15 at High Temperature and <span class="hlt">Strain</span> <span class="hlt">Rate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scapin, M.; Peroni, L.; Fichera, C.</p> <p>2014-05-01</p> <p><span class="hlt">Strain</span> <span class="hlt">rate</span> and temperature are variables of fundamental importance for the definition of the mechanical behavior of materials. In some elastic-plastic models, the <span class="hlt">effects</span>, coming from these two quantities, are considered to act independently. This approach should, in some cases, allow to greatly simplify the experimental phase correlated to the parameter identification of the material model. Nevertheless, in several applications, the material is subjected to dynamic load at very high temperature, as, for example, in case of machining operation or high energy deposition on metals. In these cases, to consider the <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature decoupled could not be acceptable. In this perspective, in this work, a methodology for testing materials varying both <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature was described and applied for the mechanical characterization of Glidcop Al-15, a copper-based composite reinforced with alumina dispersion, often used in nuclear applications. The tests at high <span class="hlt">strain</span> <span class="hlt">rate</span> were performed using the Hopkinson Bar setup for the direct tensile tests. The heating of the specimen was performed using an induction coil system and the temperature was controlled on the basis of signals from thermocouples directly welded on the specimen surface. Varying the <span class="hlt">strain</span> <span class="hlt">rate</span>, Glidcop Al-15 shows a moderate <span class="hlt">strain-rate</span> sensitivity at room temperature, while it considerably increases at high temperature: material thermal softening and <span class="hlt">strain-rate</span> hardening are strongly coupled. The experimental data were fitted using a modified formulation of the Zerilli-Armstrong model able to reproduce this kind of behavior with a good level of accuracy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880013724','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880013724"><span id="translatedtitle">Evaluation of a theory for pressure-<span class="hlt">strain</span> <span class="hlt">rate</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Weinstock, J.; Shariff, K.</p> <p>1987-01-01</p> <p>A theoretical expression for the slow part (the nonlinear fluctuation part) of the pressure-<span class="hlt">strain</span> <span class="hlt">rate</span> is compared with simulations of anisotropic homogeneous flows. The objective is to determine the quantitative accuracy of the theory and to test its prediction that the generalized Rotta coefficient, a non-dimensionalized ratio of slow term to the Reynolds stress anisotropy, varies with direction and can be negative. Comparisons are made between theoretical and simulation values of the slow term itself and of the generalized Rotta coefficients. The implications of the comparison for two-point closure theories and for Reynolds stress modeling are pointed out.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050179433','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050179433"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">Rate</span> Sensitivity of Epoxy Resin in Tensile and Shear Loading</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gilat, Amos; Goldberg, Robert K.; Roberts, Gary D.</p> <p>2005-01-01</p> <p>The mechanical response of E-862 and PR-520 resins is investigated in tensile and shear loadings. At both types of loading the resins are tested at <span class="hlt">strain</span> <span class="hlt">rates</span> of about 5x10(exp 5), 2, and 450 to 700 /s. In addition, dynamic shear modulus tests are carried out at various frequencies and temperatures, and tensile stress relaxation tests are conducted at room temperature. The results show that the toughened PR-520 resin can carry higher stresses than the untoughened E-862 resin. <span class="hlt">Strain</span> <span class="hlt">rate</span> has a significant <span class="hlt">effect</span> on the response of both resins. In shear both resins show a ductile response with maximum stress that is increasing with <span class="hlt">strain</span> <span class="hlt">rate</span>. In tension a ductile response is observed at low <span class="hlt">strain</span> <span class="hlt">rate</span> (approx. 5x10(exp 5) /s), and brittle response is observed at the medium and high <span class="hlt">strain</span> <span class="hlt">rates</span> (2, and 700 /s). The hydrostatic component of the stress in the tensile tests causes premature failure in the E-862 resin. Localized deformation develops in the PR-520 resin when loaded in shear. An internal state variable constitutive model is proposed for modeling the response of the resins. The model includes a state variable that accounts for the <span class="hlt">effect</span> of the hydrostatic component of the stress on the deformation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE.9710E..15D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE.9710E..15D"><span id="translatedtitle">Measurement of <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> in embryonic chick heart using spectral domain optical coherence tomography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dou, Shidan; Suo, Yanyan; Liang, Chengbo; Wang, Yi; Zhao, Yuqian; Liu, Jian; Xu, Tao; Wang, Ruikang; Ma, Zhenhe</p> <p>2016-03-01</p> <p>It is important to measure embryonic heart myocardial wall <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> for understanding the mechanisms of embryonic heart development. Optical coherence tomography (OCT) can provide depth resolved images with high spatial and temporal resolution, which makes it have the potential to reveal the complex myocardial activity in the early stage embryonic heart. We develop a novel method to measure <span class="hlt">strain</span> in embryonic chick heart based on spectral domain OCT images and subsequent image processing. We perform 4D(x,y,z,t) scanning on the outflow tract (OFT) of chick embryonic hearts in HH18 stage (~3 days of incubation). Only one image sequence acquired at the special position is selected based on the Doppler blood flow information where the probe beam penetrates through the OFT perpendicularly. For each image of the selected sequence, the cross-section of the myocardial wall can be approximated as an annulus. The OFT is segmented with a semi-automatic boundary detection algorithm, thus the area and mean circumference of the annular myocardial wall can be achieved. The myocardial wall thickness was calculated using the area divided by the mean circumference, and then the <span class="hlt">strain</span> was obtained. The results demonstrate that OCT can be a useful tool to describe the biomechanical characteristics of the embryonic heart.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.7786R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.7786R"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> dependent calcite microfabric evolution - an experiment carried out by nature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rogowitz, Anna; Grasemann, Bernhard; Rice, A. Hugh N.; Huet, Benjamin; Habler, Gerlinde</p> <p>2013-04-01</p> <p>The deformation behaviour of calcite has been studied experimentally in detail. Different <span class="hlt">strain</span> <span class="hlt">rates</span> and pressure and temperature conditions have been used to investigate a wide range of deformation regimes/mechanisms. However, a direct comparison with natural fault rocks remains difficult because of the extreme differences between experimental and natural <span class="hlt">strain</span> <span class="hlt">rates</span>. An a-type flanking structure developed in calcite-marbles of the Pyrgos unit, on Syros, provides a natural laboratory for directly studying the <span class="hlt">effects</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> variations at constant P-T conditions. The rocks of the Pyrgos unit underwent Eocene blueschist-facies metamorphism, resulting in coarse grained recrystallized marbles. During the subsequent greenschist-facies overprinting, the flanking structure started to form adjacent to a several meters long cross-cutting element (CE), which rotated into the shear direction, developing an antithetic offset. Comparing the microfabrics in the 1-2 cm thick CE mylonites and in the surrounding host rocks, which formed under the same metamorphic conditions but with different <span class="hlt">strain</span> <span class="hlt">rates</span>, is the central focus of this study. Numerical models have shown that a-type flanking folds form with a background shear <span class="hlt">strain</span> of only about 1-2. However, the displacement along the CE varies between 60 and 120 cm, resulting in shear <span class="hlt">strains</span> between 30 and 120. Assuming that all the deformation took place during the same event, significant <span class="hlt">strain</span> <span class="hlt">rate</span> variations (1 to 2 orders of magnitude) must have occurred between the CE and the host rock. Due to the extreme variations in <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span>, different deformation mechanisms and types of dynamic recrystallization were active, leading to the development of different microstructures and textures. With increasing <span class="hlt">strain</span>, the dominant deformation mechanism changed from twinning to dislocation glide and -climb and finally to diffusion creep. Additionally, a change from subgrain rotation to bulging recrystallization</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19970020562&hterms=rate+diffusion&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Drate%2Bdiffusion','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19970020562&hterms=rate+diffusion&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Drate%2Bdiffusion"><span id="translatedtitle"><span class="hlt">Strain-Rate</span>-Free Diffusion Flames: Initiation, Properties, and Quenching</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fendell, Francis; Rungaldier, Harald; Gokoglu, Suleyman; Schultz, Donald</p> <p>1997-01-01</p> <p>For about a half century, the stabilization of a steady planar deflagration on a heat-sink-type flat-flame burner has been of extraordinary service for the theoretical modeling and diagnostic probing of combusting gaseous mixtures. However, most engineering devices and most unwanted fire involve the burning of initially unmixed reactants. The most vigorous burning of initially separated gaseous fuel and oxidizer is the diffusion flame. In this useful idealization (limiting case), the reactants are converted to product at a mathematically thin interface, so no interpenetration of fuel and oxidizer occurs. This limit is of practical importance because it often characterizes the condition of optimal performance (and sometimes environmentally objectionable operation) of a combustor. A steady planar diffusion flame is most closely approached in the laboratory in the counterflow apparatus. The utility of this simple-<span class="hlt">strain-rate</span> flow for the modeling and probing of diffusion flames was noted by Pandya and Weinberg 35 years ago, though only in the last decade or so has its use become internationally common place. However, typically, as the <span class="hlt">strain</span> <span class="hlt">rate</span> a is reduced below about 20 cm(exp -1), and the diffusion-flame limit (reaction <span class="hlt">rate</span> much faster than the flow <span class="hlt">rate</span>) is approached, the burning is observed to become unstable in earth gravity. The advantageous steady planar flow is not available in the diffusion-flame limit in earth gravity. This is unfortunate because the typical spatial scale in a counterflow is (k/a)(sup 1/2), where k denotes a characteristic diffusion coefficient; thus, the length scale becomes large, and the reacting flow is particularly amenable to diagnostic probing, as the diffusion-flame limit is approached. The disruption of planar symmetry is owing the fact that, as the <span class="hlt">strain</span> <span class="hlt">rate</span> a decreases, the residence time (l/a) of the throughput in the counterflow burner increases. Observationally, when the residence time exceeds about 50 msec, the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/791440','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/791440"><span id="translatedtitle">Solid State Experiments at High Pressure and <span class="hlt">Strain</span> <span class="hlt">Rates</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kalantar, D.H.; Remington, B.A.; Colvin, J.D.; Mikaelian, K.O.; Weber, S.V.; Wiley, L.G.; Wark, J.S.; Loveridge, A.; Allen, A.M.; Hauer, A.; Meyers, M.A.</p> <p>1999-11-24</p> <p>Experiments have been developed using high powered laser facilities to study the response of materials in the solid state under extreme pressures and <span class="hlt">strain</span> <span class="hlt">rates</span>. Details of the target and drive development required for solid state experiments and results from two separate experiments are presented. In the first, thin foils were compressed to a peak pressure of 180 GPa and accelerated. A pre-imposed modulation at the embedded RT unstable interface was observed to grow. The growth <span class="hlt">rates</span> were fluid-like at early time, but suppressed at later time. This result is suggestive of the theory of localized heating in shear bands, followed by dissipation of the heat, allowing for recovery of the bulk material strength. In the second experiment, the response of Si was studied by dynamic x-ray diffraction. The crystal was observed to respond with uni-axial compression at a peak pressure 11.5-13.5 GPa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19412170','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19412170"><span id="translatedtitle">Tissue tectonics: morphogenetic <span class="hlt">strain</span> <span class="hlt">rates</span>, cell shape change and intercalation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Blanchard, Guy B; Kabla, Alexandre J; Schultz, Nora L; Butler, Lucy C; Sanson, Benedicte; Gorfinkiel, Nicole; Mahadevan, L; Adams, Richard J</p> <p>2009-06-01</p> <p>The dynamic reshaping of tissues during morphogenesis results from a combination of individual cell behaviors and collective cell rearrangements. However, a comprehensive framework to unambiguously measure and link cell behavior to tissue morphogenesis is lacking. Here we introduce such a kinematic framework, bridging cell and tissue behaviors at an intermediate, mesoscopic, level of cell clusters or domains. By measuring domain deformation in terms of the relative motion of cell positions and the evolution of their shapes, we characterized the basic invariant quantities that measure fundamental classes of cell behavior, namely tensorial <span class="hlt">rates</span> of cell shape change and cell intercalation. In doing so we introduce an explicit definition of cell intercalation as a continuous process. We mapped <span class="hlt">strain</span> <span class="hlt">rates</span> spatiotemporally in three models of tissue morphogenesis, gaining insight into morphogenetic mechanisms. Our quantitative approach has broad relevance for the precise characterization and comparison of morphogenetic phenotypes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/505749','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/505749"><span id="translatedtitle">Influence of <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature on the structure/property behavior of high-purity titanium</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gray, G.T. III</p> <p>1997-05-01</p> <p>The <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span>, temperature, grain size, and texture on the substructure and mechanical response of high-purity polycrystalline titanium is presented. The compressive stress-<span class="hlt">strain</span> response of 20 and 240 {mu}m grain size high-purity Ti was found to depend on both the applied <span class="hlt">strain</span> <span class="hlt">rate</span>; 0.001 {le} {epsilon} {le} 7500 s{sup -1}, and the test temperature; 77 {le} T {le} 873 K. The <span class="hlt">rate</span> of <span class="hlt">strain</span> hardening in Ti is seen to increase with increasing <span class="hlt">strain</span> <span class="hlt">rate</span>. The substructure of high-purity Ti deformed at high-<span class="hlt">strain-rate</span> or quasi-statically at 77K displayed a higher incidence of deformation twinning than during quasi-static deformation at 298K.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MMTA...48..126Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MMTA...48..126Z"><span id="translatedtitle">Twin Interactions in Pure Ti Under High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Compression</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Ping; Xiao, Dawu; Jiang, Chunli; Sang, Ge; Zou, Dongli</p> <p>2017-01-01</p> <p>Twin interactions associated with {11 overline{2} 1} (E2) twins in titanium deformed by high <span class="hlt">strain</span> <span class="hlt">rate</span> ( 2600 s-1) compression were studied using electron backscatter diffraction technique. Three types of twins, {10 overline{1} 2} (E1), {11 overline{2} 2} (C1), and {11 overline{2} 4} (C3), were observed to interact with the preformed E2 twins in four parent grains. The E1 variants nucleated at twin boundaries of some E2 variants. And the C3 twins were originated from the intersection of C1 and E2. The selection of twin variant was investigated by the Schmid factors (SFs) and the twinning shear displacement gradient tensors (DGTs) calculations. The results show that twin variants that did not follow the Schmid law were more frequently observed under high <span class="hlt">strain</span> <span class="hlt">rate</span> deformation than quasi-static deformation. Among these low-SF active variants, 73 pct (8 out of 11) can be interpreted by DGT. Besides, 26 variants that have SF values close to or higher than their active counterparts were absent. Factors that may affect the twin variant selections were discussed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJWC..9401019L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9401019L"><span id="translatedtitle">Computational modeling of dynamic mechanical properties of pure polycrystalline magnesium under high loading <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Qizhen</p> <p>2015-09-01</p> <p>Computational simulations were performed to investigate the dynamic mechanical behavior of pure polycrystalline magnesium under different high loading <span class="hlt">strain</span> <span class="hlt">rates</span> with the values of 800, 1000, 2000, and 3600 s-1. The Johnson-Cook model was utilized in the simulations based on finite element modeling. The results showed that the simulations provided well-matched predictions of the material behavior such as the <span class="hlt">strain</span> <span class="hlt">rate</span>-time history, the stress-<span class="hlt">strain</span> curve, and the temperature increase. Under high loading <span class="hlt">strain</span> <span class="hlt">rates</span>, the tested material experienced linear <span class="hlt">strain</span> hardening at the early stage of plastic deformation, increased <span class="hlt">strain</span> hardening at the intermediate plastic deformation region, and decreased <span class="hlt">strain</span> hardening at the region before fracture. The <span class="hlt">strain</span> hardening <span class="hlt">rates</span> for the studied high loading <span class="hlt">strain</span> <span class="hlt">rate</span> cases do not vary much with the change of <span class="hlt">strain</span> <span class="hlt">rates</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20522182','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20522182"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> does not affect cortical microtubule orientation in the isolated epidermis of sunflower hypocotyls.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Burian, A; Hejnowicz, Z</p> <p>2010-05-01</p> <p>A hypothesis exists that external and internal factors affect the orientation of cortical microtubules in as much as these lead to changes in cell elongation <span class="hlt">rate</span>. Factors that stimulate elongation are proposed to lead to transverse microtubule orientation, whereas factors that inhibit elongation lead to longitudinal orientation. The elongation <span class="hlt">rate</span> is equal to the <span class="hlt">rate</span> of longitudinal irreversible <span class="hlt">strain</span> in cell walls. Incubated epidermis peeled from sunflower hypocotyls does not extend unless it is stretched by loading and the pH of the incubation medium is appropriately low. Thus, peels provide a convenient model to investigate the relationship between longitudinal <span class="hlt">strain</span> <span class="hlt">rate</span> and cortical microtubule orientation. In the present study, it was found that peeling affects microtubule orientation. Peels were incubated for several hours in Murashige & Skoog medium (both unbuffered and buffered) to attain a steady state of microtubule orientation before loading. The <span class="hlt">effects</span> of loading and pH on <span class="hlt">strain</span> <span class="hlt">rate</span> and orientation of microtubules under the outer epidermal walls were examined in three portions of peels positioned with respect to the cotyledonary node. Appropriate loading caused longitudinal <span class="hlt">strain</span> of peels at pH 4.5 but not at pH 6.5. However, no clear <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> on microtubule orientation in the peels was observed. Independent of applied load and pH of the incubation medium, the microtubule orientation remained unchanged, i.e. orientation was mainly oblique. Our results show that <span class="hlt">strain</span> <span class="hlt">rate</span> does not affect cortical microtubule orientation in isolated epidermis of the sunflower hypocotyl model system, although orientation could be changed by white light.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JMPSo..63..113N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JMPSo..63..113N"><span id="translatedtitle">A numerical basis for <span class="hlt">strain</span>-gradient plasticity theory: <span class="hlt">Rate</span>-independent and <span class="hlt">rate</span>-dependent formulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nielsen, K. L.; Niordson, C. F.</p> <p>2014-02-01</p> <p>A numerical model formulation of the higher order flow theory (<span class="hlt">rate</span>-independent) by Fleck and Willis [2009. A mathematical basis for <span class="hlt">strain</span>-gradient plasticity theory - part II: tensorial plastic multiplier. Journal of the Mechanics and Physics of Solids 57, 1045-1057.], that allows for elastic-plastic loading/unloading and the interaction of multiple plastic zones, is proposed. The predicted model response is compared to the corresponding <span class="hlt">rate</span>-dependent version of visco-plastic origin, and coinciding results are obtained in the limit of small <span class="hlt">strain-rate</span> sensitivity. First, (i) the evolution of a single plastic zone is analyzed to illustrate the agreement with earlier published results, whereafter examples of (ii) multiple plastic zone interaction, and (iii) elastic-plastic loading/unloading are presented. Here, the simple shear problem of an infinite slab constrained between rigid plates is considered, and the <span class="hlt">effect</span> of <span class="hlt">strain</span> gradients, <span class="hlt">strain</span> hardening and <span class="hlt">rate</span> sensitivity is brought out. For clarity of results, a 1D model is constructed following a procedure suitable for generalization to 2D and 3D.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21230063','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21230063"><span id="translatedtitle">Statistical physics of elastoplastic steady states in amorphous solids: finite temperatures and <span class="hlt">strain</span> <span class="hlt">rates</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Karmakar, Smarajit; Lerner, Edan; Procaccia, Itamar; Zylberg, Jacques</p> <p>2010-09-01</p> <p>The <span class="hlt">effect</span> of finite temperature T and finite <span class="hlt">strain</span> <span class="hlt">rate</span> γ on the statistical physics of plastic deformations in amorphous solids made of N particles is investigated. We recognize three regimes of temperature where the statistics are qualitatively different. In the first regime the temperature is very low, T<T(cross)(N), and the <span class="hlt">strain</span> is quasistatic. In this regime the elastoplastic steady state exhibits highly correlated plastic events whose statistics are characterized by anomalous exponents. In the second regime T(cross)(N)<T<T(max)(γ) the system-size dependence of the stress fluctuations becomes normal, but the variance depends on the <span class="hlt">strain</span> <span class="hlt">rate</span>. The physical mechanism of the crossover is different for increasing temperature and increasing <span class="hlt">strain</span> <span class="hlt">rate</span>, since the plastic events are still dominated by the mechanical instabilities (seen as an eigenvalue of the Hessian matrix going to zero), and the <span class="hlt">effect</span> of temperature is only to facilitate the transition. A third regime occurs above the second crossover temperature T(max)(γ) where stress fluctuations become dominated by thermal noise. Throughout the paper we demonstrate that scaling concepts are highly relevant for the problem at hand, and finally we present a scaling theory that is able to collapse the data for all the values of temperatures and <span class="hlt">strain</span> <span class="hlt">rates</span>, providing us with a high degree of predictability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18786670','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18786670"><span id="translatedtitle">Microcracking damage and the fracture process in relation to <span class="hlt">strain</span> <span class="hlt">rate</span> in human cortical bone tensile failure.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zioupos, Peter; Hansen, Ulrich; Currey, John D</p> <p>2008-10-20</p> <p>It is difficult to define the 'physiological' mechanical properties of bone. Traumatic failures in-vivo are more likely to be orders of magnitude faster than the quasistatic tests usually employed in-vitro. We have reported recently [Hansen, U., Zioupos, P., Simpson, R., Currey, J.D., Hynd, D., 2008. The <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> on the mechanical properties of human cortical bone. Journal of Biomechanical Engineering/Transactions of the ASME 130, 011011-1-8] results from tests on specimens of human femoral cortical bone loaded in tension at <span class="hlt">strain</span> <span class="hlt">rates</span> (epsilon ) ranging from low (0.08s(-1)) to high (18s(-1)). Across this <span class="hlt">strain</span> <span class="hlt">rate</span> range the modulus of elasticity generally increased, stress at yield and failure and <span class="hlt">strain</span> at failure decreased for <span class="hlt">rates</span> higher than 1s(-1), while <span class="hlt">strain</span> at yield was invariant for most <span class="hlt">strain</span> <span class="hlt">rates</span> and only decreased at <span class="hlt">rates</span> higher than 10s(-1). The results showed that <span class="hlt">strain</span> <span class="hlt">rate</span> has a stronger <span class="hlt">effect</span> on post-yield deformation than on initiation of macroscopic yielding. In general, specimens loaded at high <span class="hlt">strain</span> <span class="hlt">rates</span> were brittle, while those loaded at low <span class="hlt">strain</span> <span class="hlt">rates</span> were much tougher. Here, a post-test examination of the microcracking damage reveals that microcracking was inversely related to the <span class="hlt">strain</span> <span class="hlt">rate</span>. Specimens loaded at low <span class="hlt">strain</span> <span class="hlt">rates</span> showed considerable post-yield <span class="hlt">strain</span> and also much more microcracking. Partial correlation and regression analysis suggested that the development of post-yield <span class="hlt">strain</span> was a function of the amount of microcracking incurred (the cause), rather than being a direct result of the <span class="hlt">strain</span> <span class="hlt">rate</span> (the excitation). Presumably low <span class="hlt">strain</span> <span class="hlt">rates</span> allow time for microcracking to develop, which increases the compliance of the specimen, making them tougher. This behaviour confirms a more general rule that the degree to which bone is brittle or tough depends on the amount of microcracking damage it is able to sustain. More importantly, the key to bone toughness is its ability to avoid a ductile</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24730833','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24730833"><span id="translatedtitle"><span class="hlt">Strain-rate</span>-dependent model for the dynamic compression of elastoplastic spheres.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Burgoyne, Hayden A; Daraio, Chiara</p> <p>2014-03-01</p> <p>We present a force-displacement contact model for the compressive loading of elastoplastic spheres. This model builds from the well known Hertz contact law for elastic, quasistatic compression to incorporate a material's <span class="hlt">strain-rate</span>-dependent plasticity in order to describe collisions between particles. In the quasistatic regime, finite-element analysis is used to derive an empirical function of the material properties. A Johnson-Cook <span class="hlt">strain</span> <span class="hlt">rate</span> dependence is then included into the model to study dynamic <span class="hlt">effects</span>. We validate the model using split Hopkinson bar experiments and show that the model can accurately simulate the force-displacement response of <span class="hlt">strain-rate</span>-dependent elastoplastic spheres during dynamic compression and unloading.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhRvE..89c2203B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhRvE..89c2203B"><span id="translatedtitle"><span class="hlt">Strain-rate</span>-dependent model for the dynamic compression of elastoplastic spheres</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burgoyne, Hayden A.; Daraio, Chiara</p> <p>2014-03-01</p> <p>We present a force-displacement contact model for the compressive loading of elastoplastic spheres. This model builds from the well known Hertz contact law for elastic, quasistatic compression to incorporate a material's <span class="hlt">strain-rate</span>-dependent plasticity in order to describe collisions between particles. In the quasistatic regime, finite-element analysis is used to derive an empirical function of the material properties. A Johnson-Cook <span class="hlt">strain</span> <span class="hlt">rate</span> dependence is then included into the model to study dynamic <span class="hlt">effects</span>. We validate the model using split Hopkinson bar experiments and show that the model can accurately simulate the force-displacement response of <span class="hlt">strain-rate</span>-dependent elastoplastic spheres during dynamic compression and unloading.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4777412','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4777412"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">Rate</span> and Anisotropic Microstructure Dependent Mechanical Behaviors of Silkworm Cocoon Shells</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Xu, Jun; Zhang, Wen; Gao, Xiang; Meng, Wanlin; Guan, Juan</p> <p>2016-01-01</p> <p>Silkworm cocoons are multi-layered composite structures comprised of high strength silk fiber and sericin, and their mechanical properties have been naturally selected to protect pupas during metamorphosis from various types of external attacks. The present study attempts to gain a comprehensive understanding of the mechanical properties of cocoon shell materials from wild silkworm species Antheraea pernyi under dynamic loading <span class="hlt">rates</span>. Five dynamic <span class="hlt">strain</span> <span class="hlt">rates</span> from 0.00625 s-1 to 12.5 s-1 are tested to show the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity of the cocoon shell material. In the meantime, the anisotropy of the cocoon shell is considered and the cocoon shell specimens are cut along 0°, 45° and 90° orientation to the short axis of cocoons. Typical mechanical properties including Young’s modulus, yield strength, ultimate strength and ultimate <span class="hlt">strain</span> are extracted and analyzed from the stress-<span class="hlt">strain</span> curves. Furthermore, the fracture morphologies of the cocoon shell specimens are observed under scanning electron microscopy to help understand the relationship between the mechanical properties and the microstructures of the cocoon material. A discussion on the dynamic <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effect</span> on the mechanical properties of cocoon shell material is followed by fitting our experimental results to two previous models, and the <span class="hlt">effect</span> could be well explained. We also compare natural and dried cocoon materials for the dynamic <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effect</span> and interestingly the dried cocoon shells show better overall mechanical properties. This study provides a different perspective on the mechanical properties of cocoon material as a composite material, and provides some insight for bio-inspired engineering materials. PMID:26939063</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26939063','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26939063"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">Rate</span> and Anisotropic Microstructure Dependent Mechanical Behaviors of Silkworm Cocoon Shells.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xu, Jun; Zhang, Wen; Gao, Xiang; Meng, Wanlin; Guan, Juan</p> <p>2016-01-01</p> <p>Silkworm cocoons are multi-layered composite structures comprised of high strength silk fiber and sericin, and their mechanical properties have been naturally selected to protect pupas during metamorphosis from various types of external attacks. The present study attempts to gain a comprehensive understanding of the mechanical properties of cocoon shell materials from wild silkworm species Antheraea pernyi under dynamic loading <span class="hlt">rates</span>. Five dynamic <span class="hlt">strain</span> <span class="hlt">rates</span> from 0.00625 s-1 to 12.5 s-1 are tested to show the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity of the cocoon shell material. In the meantime, the anisotropy of the cocoon shell is considered and the cocoon shell specimens are cut along 0°, 45° and 90° orientation to the short axis of cocoons. Typical mechanical properties including Young's modulus, yield strength, ultimate strength and ultimate <span class="hlt">strain</span> are extracted and analyzed from the stress-<span class="hlt">strain</span> curves. Furthermore, the fracture morphologies of the cocoon shell specimens are observed under scanning electron microscopy to help understand the relationship between the mechanical properties and the microstructures of the cocoon material. A discussion on the dynamic <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effect</span> on the mechanical properties of cocoon shell material is followed by fitting our experimental results to two previous models, and the <span class="hlt">effect</span> could be well explained. We also compare natural and dried cocoon materials for the dynamic <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effect</span> and interestingly the dried cocoon shells show better overall mechanical properties. This study provides a different perspective on the mechanical properties of cocoon material as a composite material, and provides some insight for bio-inspired engineering materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4304325','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4304325"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> viscoelastic analysis of soft and highly hydrated biomaterials</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Tirella, A; Mattei, G; Ahluwalia, A</p> <p>2014-01-01</p> <p>Measuring the viscoelastic behavior of highly hydrated biological materials is challenging because of their intrinsic softness and labile nature. In these materials, it is difficult to avoid prestress and therefore to establish precise initial stress and <span class="hlt">strain</span> conditions for lumped parameter estimation using creep or stress-relaxation (SR) tests. We describe a method ( or epsilon dot method) for deriving the viscoelastic parameters of soft hydrated biomaterials which avoids prestress and can be used to rapidly test degradable samples. Standard mechanical tests are first performed compressing samples using different <span class="hlt">strain</span> <span class="hlt">rates</span>. The dataset obtained is then analyzed to mathematically derive the material's viscoelastic parameters. In this work a stable elastomer, polydimethylsiloxane, and a labile hydrogel, gelatin, were first tested using the, in parallel SR was used to compare lumped parameter estimation. After demonstrating that the elastic parameters are equivalent and that the estimation of short-time constants is more precise using the proposed method, the viscoelastic behavior of porcine liver was investigated using this approach. The results show that the constitutive parameters of hepatic tissue can be quickly quantified without the application of any prestress and before the onset of time-dependent degradation phenomena. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 3352–3360, 2014 PMID:23946054</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006JPhy4.134..325R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006JPhy4.134..325R"><span id="translatedtitle">Theoretical and numerical study of <span class="hlt">strain</span> localization under high <span class="hlt">strain</span> <span class="hlt">rate</span> solicitation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ranc, N.; Raynal, R.; Taravella, L.; Pina, V.; Hervé, P.</p> <p>2006-08-01</p> <p>Our study deals with the dynamic behavior of metallic materials and in particular of titanium alloy TA6V. For high <span class="hlt">strain</span> <span class="hlt">rates</span>, we can notice the occurrence of a phenomenon called adiabatic shearing. This phenomenon is about a plastic instability, which results in the appearance of a <span class="hlt">strain</span> localization in narrow bands. In this paper we developed a thermo mechanical model to reproduce the formation and the propagation of adiabatic shear bands. A Johnson Cook thermo visco plastic behavior law was chosen for the titanium alloy TA6V. The law parameters were identified from static and dynamic torsion tests at various temperatures between ambient and 350circC. A 2D numerical simulation of torsion test was performed with the explicit finite elements code Abaqus. The thermo mechanical coupling and the heat conduction are taken into account. A roughness defect was inserted in the centre of a torsion specimen. The results showed that the <span class="hlt">strain</span> of localization and the shear band speed increase when the amplitude and the size of the defect decrease.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006JPhy4.134..269G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006JPhy4.134..269G"><span id="translatedtitle">High <span class="hlt">strain</span> <span class="hlt">rate</span> and high temperature behaviour of metallic materials for jet engine turbine containment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gálvez, F.; Cendón, D.; Enfedaque, A.; Sánchez-Gálvez, V.</p> <p>2006-08-01</p> <p>This work presents a study on the mechanical characterisation of the materials involved in air jet engine turbines. The final objective is to analyse the phenomenon of a turbine blade off failure, to verify the requirements of the case containment. The materials in the turbine are under high temperatures, ranging from 400circC to 800circC and when the fail of the blade occurs if impacts against the case, reaching <span class="hlt">strain</span> <span class="hlt">rates</span> up to 103 s - 1. To obtain the behaviour of the materials, testing at high <span class="hlt">strain</span> <span class="hlt">rate</span> and high temperature at one time is necessary. The experimental set-up used was a split Hopkinson pressure bar, with a high temperature furnace adapted. The bars used on the device were high strength nickel alloys with a cooling system to decrease the temperature of the measurement devices. The <span class="hlt">effect</span> of wave dispersion due to the temperature gradient has been also studied to correct the measurements if necessary. The material tested has been the FV535 stainless steel used on the case. The full stress-<span class="hlt">strain</span> curves at different temperatures and at <span class="hlt">strain</span> <span class="hlt">rates</span> up to 103 s-1 have been obtained. The experimental results show a marked influence of the <span class="hlt">strain</span> <span class="hlt">rate</span> and the temperature that cannot be neglected. The Johnson-Cook material model has been used to fit the results of the material tests.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/989822','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/989822"><span id="translatedtitle">Deviatoric constitutive model: domain of <span class="hlt">strain</span> <span class="hlt">rate</span> validity</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zocher, Marvin A</p> <p>2009-01-01</p> <p>A case is made for using an enhanced methodology in determining the parameters that appear in a deviatoric constitutive model. Predictability rests on our ability to solve a properly posed initial boundary value problem (IBVP), which incorporates an accurate reflection of material constitutive behavior. That reflection is provided through the constitutive model. Moreover, the constitutive model is required for mathematical closure of the IBVP. Common practice in the shock physics community is to divide the Cauchy tensor into spherical and deviatoric parts, and to develop separate models for spherical and deviatoric constitutive response. Our focus shall be on the Cauchy deviator and deviatoric constitutive behavior. Discussions related to the spherical part of the Cauchy tensor are reserved for another time. A number of deviatoric constitutive models have been developed for utilization in the solution of IBVPs that are of interest to those working in the field of shock physics, e.g. All of these models are phenomenological and contain a number of parameters that must be determined in light of experimental data. The methodology employed in determining these parameters dictates the loading regime over which the model can be expected to be accurate. The focus of this paper is the methodology employed in determining model parameters and the consequences of that methodology as it relates to the domain of <span class="hlt">strain</span> <span class="hlt">rate</span> validity. We shall begin by describing the methodology that is typically employed. We shall discuss limitations imposed upon predictive capability by the typically employed methodology. We shall propose a modification to the typically employed methodology that significantly extends the domain of <span class="hlt">strain</span> <span class="hlt">rate</span> validity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.S13C..03B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.S13C..03B"><span id="translatedtitle">Global Earthquake Activity <span class="hlt">Rate</span> models based on version 2 of the Global <span class="hlt">Strain</span> <span class="hlt">Rate</span> Map</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bird, P.; Kreemer, C.; Kagan, Y. Y.; Jackson, D. D.</p> <p>2013-12-01</p> <p>Global Earthquake Activity <span class="hlt">Rate</span> (GEAR) models have usually been based on either relative tectonic motion (fault slip <span class="hlt">rates</span> and/or distributed <span class="hlt">strain</span> <span class="hlt">rates</span>), or on smoothing of seismic catalogs. However, a hybrid approach appears to perform better than either parent, at least in some retrospective tests. First, we construct a Tectonic ('T') forecast of shallow (≤ 70 km) seismicity based on global plate-boundary <span class="hlt">strain</span> <span class="hlt">rates</span> from version 2 of the Global <span class="hlt">Strain</span> <span class="hlt">Rate</span> Map. Our approach is the SHIFT (Seismic Hazard Inferred From Tectonics) method described by Bird et al. [2010, SRL], in which the character of the <span class="hlt">strain</span> <span class="hlt">rate</span> tensor (thrusting and/or strike-slip and/or normal) is used to select the most comparable type of plate boundary for calibration of the coupled seismogenic lithosphere thickness and corner magnitude. One difference is that activity of offshore plate boundaries is spatially smoothed using empirical half-widths [Bird & Kagan, 2004, BSSA] before conversion to seismicity. Another is that the velocity-dependence of coupling in subduction and continental-convergent boundaries [Bird et al., 2009, BSSA] is incorporated. Another forecast component is the smoothed-seismicity ('S') forecast model of [Kagan & Jackson, 1994, JGR; Kagan & Jackson, 2010, GJI], which was based on optimized smoothing of the shallow part of the GCMT catalog, years 1977-2004. Both forecasts were prepared for threshold magnitude 5.767. Then, we create hybrid forecasts by one of 3 methods: (a) taking the greater of S or T; (b) simple weighted-average of S and T; or (c) log of the forecast <span class="hlt">rate</span> is a weighted average of the logs of S and T. In methods (b) and (c) there is one free parameter, which is the fractional contribution from S. All hybrid forecasts are normalized to the same global <span class="hlt">rate</span>. Pseudo-prospective tests for 2005-2012 (using versions of S and T calibrated on years 1977-2004) show that many hybrid models outperform both parents (S and T), and that the optimal weight on S</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EPJST.206....3E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EPJST.206....3E"><span id="translatedtitle"><span class="hlt">Effect</span> of the temperature, <span class="hlt">strain</span> <span class="hlt">rate</span> and microstructure on flow and fracture characteristics of Ti-45Al-2Nb-2Mn+0.8vol.% TiB2 XD alloy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Erice, B.; Pérez-Martín, M. J.; Cendón, D. A.; Gálvez, F.</p> <p>2012-05-01</p> <p>A series of quasi-static and dynamic tensile tests at varying temperatures were carried out to determine the mechanical behaviour of Ti-45Al-2Nb-2Mn+0.8vol.% TiB2 XD as-HIPed alloy. The temperature for the tests ranged from room temperature to 850 ∘C. The <span class="hlt">effect</span> of the temperature on the ultimate tensile strength, as expected, was almost negligible within the selected temperature range. Nevertheless, the plastic flow suffered some softening because of the temperature. This alloy presents a relatively low ductility; thus, a low tensile <span class="hlt">strain</span> to failure. The dynamic tests were performed in a Split Hopkinson Tension Bar, showing an increase of the ultimate tensile strength due to the <span class="hlt">strain</span> <span class="hlt">rate</span> hardening <span class="hlt">effect</span>. Johnson-Cook constitutive relation was used to model the plastic flow. A post-testing microstructural of the specimens revealed an inhomogeneous structure, consisting of lamellar α2 + γ structure and γ phase equiaxed grains in the centre, and a fully lamellar structure on the rest. The assessment of the duplex-fully lamellar area ratio showed a clear relationship between the microstructure and the fracture behaviour.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.734c2140V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.734c2140V"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">Rate</span> Dependant Material Model for Orthotropic Metals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vignjevic, Rade</p> <p>2016-08-01</p> <p>In manufacturing processes anisotropic metals are often exposed to the loading with high <span class="hlt">strain</span> <span class="hlt">rates</span> in the range from 102 s-1 to 106 s-1 (e.g. stamping, cold spraying and explosive forming). These types of loading often involve generation and propagation of shock waves within the material. The material behaviour under such a complex loading needs to be accurately modelled, in order to optimise the manufacturing process and achieve appropriate properties of the manufactured component. The presented research is related to development and validation of a thermodynamically consistent physically based constitutive model for metals under high <span class="hlt">rate</span> loading. The model is capable of modelling damage, failure and formation and propagation of shock waves in anisotropic metals. The model has two main parts: the strength part which defines the material response to shear deformation and an equation of state (EOS) which defines the material response to isotropic volumetric deformation [1]. The constitutive model was implemented into the transient nonlinear finite element code DYNA3D [2] and our in house SPH code. Limited model validation was performed by simulating a number of high velocity material characterisation and validation impact tests. The new damage model was developed in the framework of configurational continuum mechanics and irreversible thermodynamics with internal state variables. The use of the multiplicative decomposition of deformation gradient makes the model applicable to arbitrary plastic and damage deformations. To account for the physical mechanisms of failure, the concept of thermally activated damage initially proposed by Tuller and Bucher [3], Klepaczko [4] was adopted as the basis for the new damage evolution model. This makes the proposed damage/failure model compatible with the Mechanical Threshold Strength (MTS) model Follansbee and Kocks [5], 1988; Chen and Gray [6] which was used to control evolution of flow stress during plastic deformation. In</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhD...49W3002Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhD...49W3002Y"><span id="translatedtitle">Atomistic modeling at experimental <span class="hlt">strain</span> <span class="hlt">rates</span> and timescales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yan, Xin; Cao, Penghui; Tao, Weiwei; Sharma, Pradeep; Park, Harold S.</p> <p>2016-12-01</p> <p>Modeling physical phenomena with atomistic fidelity and at laboratory timescales is one of the holy grails of computational materials science. Conventional molecular dynamics (MD) simulations enable the elucidation of an astonishing array of phenomena inherent in the mechanical and chemical behavior of materials. However, conventional MD, with our current computational modalities, is incapable of resolving timescales longer than microseconds (at best). In this short review article, we briefly review a recently proposed approach—the so-called autonomous basin climbing (ABC) method—that in certain instances can provide valuable information on slow timescale processes. We provide a general summary of the principles underlying the ABC approach, with emphasis on recent methodological developments enabling the study of mechanically-driven processes at slow (experimental) <span class="hlt">strain</span> <span class="hlt">rates</span> and timescales. Specifically, we show that by combining a strong physical understanding of the underlying phenomena, kinetic Monte Carlo, transition state theory and minimum energy pathway methods, the ABC method has been found to be useful in a variety of mechanically-driven problems ranging from the prediction of creep-behavior in metals, constitutive laws for grain boundary sliding, void nucleation <span class="hlt">rates</span>, diffusion in amorphous materials to protein unfolding. Aside from reviewing the basic ideas underlying this approach, we emphasize some of the key challenges encountered in our own personal research work and suggest future research avenues for exploration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJWC..9401047Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9401047Y"><span id="translatedtitle">The compressive behaviour and constitutive equation of polyimide foam in wide <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yoshimoto, Akifumi; Kobayashi, Hidetoshi; Horikawa, Keitaro; Tanigaki, Kenichi</p> <p>2015-09-01</p> <p>These days, polymer foams, such as polyurethane foam and polystyrene foam, are used in various situations as a thermal insulator or shock absorber. In general, however, their strength is insufficient in high temperature environments because of their low glass transition temperature. Polyimide is a polymer which has a higher glass transition temperature and high strength. Its mechanical properties do not vary greatly, even in low temperature environments. Therefore, polyimide foam is expected to be used in the aerospace industry. Thus, the constitutive equation of polyimide foam that can be applied across a wide range of <span class="hlt">strain</span> <span class="hlt">rates</span> and ambient temperature is very useful. In this study, a series of compression tests at various <span class="hlt">strain</span> <span class="hlt">rates</span>, from 10-3 to 103 s-1 were carried out in order to examine the <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> on the compressive properties of polyimide foam. The flow stress of polyimide foam increased rapidly at dynamic <span class="hlt">strain</span> <span class="hlt">rates</span>. The <span class="hlt">effect</span> of ambient temperature on the properties of polyimide foam was also investigated at temperature from - 190 °C to 270°∘C. The flow stress decreased with increasing temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015StGM...37Q..57S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015StGM...37Q..57S"><span id="translatedtitle">Influence of <span class="hlt">Strain</span> <span class="hlt">Rate</span> on Tensile Strength of Woven Geotextile in the Selected Range of Temperature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stępień, Sylwia; Szymański, Alojzy</p> <p>2015-06-01</p> <p>Investigation of geosynthetics behaviour has been carried out for many years. Before using geosynthetics in practice, the standard laboratory tests had been carried out to determine basic mechanical parameters. In order to examine the tensile strength of the sample which extends at a constant <span class="hlt">strain</span> <span class="hlt">rate</span>, one should measure the value of the tensile force and <span class="hlt">strain</span>. Note that geosynthetics work under different conditions of stretching and temperatures, which significantly reduce the strength of these materials. The paper presents results of the tensile test of geotextile at different <span class="hlt">strain</span> <span class="hlt">rates</span> and temperatures from 20 °C to 100 °C. The aim of this study was to determine the <span class="hlt">effect</span> of temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> on tensile strength and <span class="hlt">strain</span> of the woven geotextile. The article presents the method of investigation and the results. The data obtained allowed us to assess the parameters of material which should be considered in the design of the load-bearing structures that work at temperatures up to 100 °C.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.G13A1014G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.G13A1014G"><span id="translatedtitle">Present-day CGPS-derived Crustal <span class="hlt">Strain</span> <span class="hlt">Rate</span> Field of the Saint Lawrence River Valley</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goudarzi, M. A.; Cocard, M.; Santerre, R.</p> <p>2015-12-01</p> <p>The Saint Lawrence River valley (SLRV) is one of the most seismically active areas in eastern Canada. Along the SLRV and the Ottawa valley, earthquakes are concentrated on three distinct zones of western Quebec along the Ottawa River, Charlevoix, and Lower Saint Lawrence. The entire area is also subject to the glacial isostatic adjustment (GIA). We studied the earth's surface deformation of the area using the velocity field of 51 continuous GPS (CGPS) stations and the least-squares collocation method. While the intraplate horizontal velocities showed a coherent horizontal motion towards southeast with the typical magnitude of ~1.3 mm/yr for stations along the SLRV, the interpolated vertical velocities demonstrated a coherent uplift with the average <span class="hlt">rate</span> of 3.1 mm/yr. We estimated <span class="hlt">strain</span> <span class="hlt">rate</span> tensors including the <span class="hlt">effect</span> of vertical velocity. A NNW-SSE shortening with a typical <span class="hlt">rate</span> of ~3.6-8.1 nstrain/yr was observed over Lower Saint Lawrence. In Charlevoix, an extension with a typical <span class="hlt">rate</span> of ~3.0-7.1 nstrain/yr was oriented in ENE-WSW parallel to the SLRV. In western Quebec, the deformation has a shear <span class="hlt">straining</span> mechanism with a typical shortening <span class="hlt">rate</span> of ~1.0-5.1 nstrain/yr and extension <span class="hlt">rate</span> of ~1.6-4.1 nstrain/yr. The extension over the northern model is consistent with the prediction of the GIA models. The range of the estimated <span class="hlt">strain</span> <span class="hlt">rates</span> of the area (~1.0-8.1 nstrain/yr) is between typical values of rigid blocks (< 0.1 nstrain/yr) and active tectonic regions (> 100 μ<span class="hlt">strain</span>/yr). A strong correlation was observed between epicenters of earthquakes and areas with the highest <span class="hlt">rate</span> of shear <span class="hlt">strain</span>. We found a good agreement between the orientations of the principal axes of <span class="hlt">strain</span> <span class="hlt">rate</span> tensors and the maximum horizontal compressional stress σH from World Stress Map 2008 for both strike-slip and thrust faulting regimes especially those derived from focal mechanisms. This shows our CGPS intraplate velocities are representative of the current crustal deformation</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006MTDM...10...83L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006MTDM...10...83L"><span id="translatedtitle">The compressive behavior of isocyanate-crosslinked silica aerogel at high <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Luo, H.; Lu, H.; Leventis, N.</p> <p>2006-06-01</p> <p>Aerogels are low-density, highly nano-porous materials. Their engineering applications are limited due to their brittleness and hydrophilicity. Recently, a strong lightweight crosslinked silica aerogel has been developed by encapsulating the skeletal framework of amine-modified silica aerogels with polyureas derived by isocyanate. The mesoporous structure of the underlying silica framework is preserved through conformal polymer coating, and the thermal conductivity remains low. Characterization has been conducted on the thermal, physical properties and the mechanical properties under quasi-static loading conditions. In this paper, we present results on the dynamic compressive behavior of the crosslinked silica aerogel (CSA) using a split Hopkinson pressure bar (SHPB). A new tubing pulse shaper was employed to help reach the dynamic stress equilibrium and constant <span class="hlt">strain</span> <span class="hlt">rate</span>. The stress-<span class="hlt">strain</span> relationship was determined at high <span class="hlt">strain</span> <span class="hlt">rates</span> within 114-4386 s-1. The <span class="hlt">effects</span> of <span class="hlt">strain</span> <span class="hlt">rate</span>, density, specimen thickness and water absorption on the dynamic behavior of the CSA were investigated through a series of dynamic experiments. The Young’s moduli (or 0.2% offset compressive yield strengths) at a <span class="hlt">strain</span> <span class="hlt">rate</span> ˜350 s-1 were determined as 10.96/2.08, 159.5/6.75, 192.2/7.68, 304.6/11.46, 407.0/20.91 and 640.5/30.47 MPa for CSA with densities 0.205, 0.454, 0.492, 0.551, 0.628 and 0.731 g cm-3, respectively. The deformation and failure behaviors of a native silica aerogel with density (0.472 g cm-3), approximately the same as a typical CSA sample were observed with a high speed digital camera. Digital image correlation technique was used to determine the surface <span class="hlt">strains</span> through a series of images acquired using high speed photography. The relative uniform axial deformation indicated that localized compaction did not occur at a compressive <span class="hlt">strain</span> level of ˜17%, suggesting most likely failure mechanism at high <span class="hlt">strain</span> <span class="hlt">rate</span> to be different from that under quasi</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20070008243&hterms=Young+modulus+strain+rate+effect&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DYoung%2Bmodulus%252C%2Bstrain%2Brate%2Beffect','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20070008243&hterms=Young+modulus+strain+rate+effect&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DYoung%2Bmodulus%252C%2Bstrain%2Brate%2Beffect"><span id="translatedtitle">The Compressive Behavior of Isocyanate-crosslinked Silica Aerogel at High <span class="hlt">Strain</span> <span class="hlt">Rates</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Luo, H.; Lu, H.; Leventis, N.</p> <p>2006-01-01</p> <p>Aerogels are low-density, highly nano-porous materials. Their engineering applications are limited due to their brittleness and hydrophilicity. Recently, a strong lightweight crosslinked silica aerogel has been developed by encapsulating the skeletal framework of amine-modified silica aerogels with polyureas derived by isocyanate. The mesoporous structure of the underlying silica framework is preserved through conformal polymer coating, and the thermal conductivity remains low. Characterization has been conducted on the thermal, physical properties and the mechanical properties under quasi-static loading conditions. In this paper, we present results on the dynamic compressive behavior of the crosslinked silica aerogel (CSA) using a split Hopkinson pressure bar (SHPB). A new tubing pulse shaper was employed to help reach the dynamic stress equilibrium and constant <span class="hlt">strain</span> <span class="hlt">rate</span>. The stress-<span class="hlt">strain</span> relationship was determined at high <span class="hlt">strain</span> <span class="hlt">rates</span> within 114-4386/s. The <span class="hlt">effects</span> of <span class="hlt">strain</span> <span class="hlt">rate</span>, density, specimen thickness and water absorption on the dynamic behavior of the CSA were investigated through a series of dynamic experiments. The Young's moduli (or 0.2% offset compressive yield strengths) at a <span class="hlt">strain</span> <span class="hlt">rate</span> approx.350/s were determined as 10.96/2.08, 159.5/6.75, 192.2/7.68, 304.6/11.46, 407.0/20.91 and 640.5/30.47 MPa for CSA with densities 0.205, 0.454, 0.492, 0.551,0.628 and 0.731 g/cu cm, respectively. The deformation and failure behaviors of a native silica aerogel with density (0.472 g/cu cm ), approximately the same as a typical CSA sample were observed with a high speed digital camera. Digital image correlation technique was used to determine the surface <span class="hlt">strains</span> through a series of images acquired using high speed photography. The relative uniform axial deformation indicated that localized compaction did not occur at a compressive <span class="hlt">strain</span> level of approx.17%, suggesting most likely failure mechanism at high <span class="hlt">strain</span> <span class="hlt">rate</span> to be different from that under quasi</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21640354','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21640354"><span id="translatedtitle">A method to characterize in vivo tendon force-<span class="hlt">strain</span> relationship by combining ultrasonography, motion capture and loading <span class="hlt">rates</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gerus, Pauline; Rao, Guillaume; Berton, Eric</p> <p>2011-08-11</p> <p>The ultrasonography contributes to investigate in vivo tendon force-<span class="hlt">strain</span> relationship during isometric contraction. In previous studies, different methods are available to estimate the tendon <span class="hlt">strain</span>, using different loading <span class="hlt">rates</span> and models to fit the tendon force-<span class="hlt">strain</span> relationship. This study was aimed to propose a standard method to characterize the in vivo tendon force-<span class="hlt">strain</span> relationship. We investigated the influence on the force-<span class="hlt">strain</span> relationship for medialis gastrocnemius (MG) of (1) one method which takes into account probe and joint movements to estimate the instantaneous tendon length, (2) models used to fit the force-<span class="hlt">strain</span> relationship for uniaxial test (polynomial vs. Ogden), and (3) the loading <span class="hlt">rate</span> on tendon <span class="hlt">strain</span>. Subjects performed ramp-up contraction during isometric contractions at two different target speeds: 1.5s and minimal time with ultrasound probe fixed over the muscle-tendon junction of the MG muscle. The used method requires three markers on ultrasound probe and a marker on calcaneum to take into account all movements, and was compared to the <span class="hlt">strain</span> estimated using ultrasound images only. The method using ultrasound image only overestimated the tendon <span class="hlt">strain</span> from 40% of maximal force. The polynomial model showed similar fitting results than the Ogden model (R²=0.98). A loading <span class="hlt">rate</span> <span class="hlt">effect</span> was found on tendon <span class="hlt">strain</span>, showing a higher <span class="hlt">strain</span> when loading <span class="hlt">rate</span> decreases. The characterization of tendon force-<span class="hlt">strain</span> relationship needs to be standardized by taking into account all movements to estimate tendon <span class="hlt">strain</span> and controlling the loading <span class="hlt">rate</span>. The polynomial model appears to be appropriate to represent the tendon force-<span class="hlt">strain</span> relationship.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25503536','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25503536"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">effects</span> on oxygen migration in perovskites.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mayeshiba, Tam; Morgan, Dane</p> <p>2015-01-28</p> <p>Fast oxygen transport materials are necessary for a range of technologies, including efficient and cost-<span class="hlt">effective</span> solid oxide fuel cells, gas separation membranes, oxygen sensors, chemical looping devices, and memristors. <span class="hlt">Strain</span> is often proposed as a method to enhance the performance of oxygen transport materials, but the magnitude of its <span class="hlt">effect</span> and its underlying mechanisms are not well-understood, particularly in the widely-used perovskite-structured oxygen conductors. This work reports on an ab initio prediction of <span class="hlt">strain</span> <span class="hlt">effects</span> on migration energetics for nine perovskite systems of the form LaBO3, where B = [Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga]. Biaxial <span class="hlt">strain</span>, as might be easily produced in epitaxial systems, is predicted to lead to approximately linear changes in migration energy. We find that tensile biaxial <span class="hlt">strain</span> reduces the oxygen vacancy migration barrier across the systems studied by an average of 66 meV per percent <span class="hlt">strain</span> for a single selected hop, with a low of 36 and a high of 89 meV decrease in migration barrier per percent <span class="hlt">strain</span> across all systems. The estimated range for the change in migration barrier within each system is ±25 meV per percent <span class="hlt">strain</span> when considering all hops. These results suggest that <span class="hlt">strain</span> can significantly impact transport in these materials, e.g., a 2% tensile <span class="hlt">strain</span> can increase the diffusion coefficient by about three orders of magnitude at 300 K (one order of magnitude at 500 °C or 773 K) for one of the most <span class="hlt">strain</span>-responsive materials calculated here (LaCrO3). We show that a simple elasticity model, which assumes only dilative or compressive <span class="hlt">strain</span> in a cubic environment and a fixed migration volume, can qualitatively but not quantitatively model the <span class="hlt">strain</span> dependence of the migration energy, suggesting that factors not captured by continuum elasticity play a significant role in the <span class="hlt">strain</span> response.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/7045489','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/7045489"><span id="translatedtitle">On the influence of <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity on wear in the Archard regime</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Brechet, Y. . Lab. de Thermodynamique et Physico-Chimie Metallurgique); Estrin, Y. . Dept. of Mechanical and Materials Engineering)</p> <p>1994-06-01</p> <p>Relating wear characteristics of a metallic material to its mechanical properties (yield strength, <span class="hlt">strain</span> hardening coefficient) and its microstructural features (size and volume fraction of inclusions) is a long-standing problem. The diversity of mechanisms which are involved during wear processes makes it practically impossible to have a general theory which would encompass all thinkable situations corresponding to various loads and various regimes of sliding. Different regimes and the conditions for their occurrence have been systematized in wear mechanism maps. In this communication the authors are going to restrict their consideration to plasticity dominated wear which is expected to occur in the low velocity range where surface heating is negligible. In this regime, the prevalent wear mechanism is the removal of slivers of metal by plastic failure due to shearing of contact asperities. The classic works by Rabinowicz have demonstrated clearly that solid friction is a <span class="hlt">rate</span> dependent problem and that the velocity dependence of dynamic solid friction is nothing else than a consequence of the increase of static solid friction with time during which normal load was applied prior to the commencement of sliding. Creep under normal compression stress leads to flattening of the junctions causing their strength to increase with time. Like solid friction, wear appears to be a <span class="hlt">rate</span> dependent phenomenon, and the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity of the flow stress can be expected to be relevant for wear resistance. The <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity is known to play an important role in other damage related properties, such as ductility and fracture toughness. The authors felt that it would be of interest to evaluate the <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity on the wear <span class="hlt">rate</span> as part of an attempt to relate the wear properties to a bulk constitutive equation, and as a guideline for assessing the influence of alloying elements known to affect the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6372873','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6372873"><span id="translatedtitle">Comparison of <span class="hlt">strain</span> <span class="hlt">rates</span> of dart impacted plaques and pendulum impacted bumpers</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Scammell, K.L.</p> <p>1987-01-01</p> <p>The difference in <span class="hlt">strain</span> <span class="hlt">rates</span> prevailing during pendulum impact of bumpers versus high speed dart impact of plaques was investigated. Uni-axial <span class="hlt">strain</span> gages were applied to the tension side of the plaques and bumpers directly opposite the point of impact. The plaques were impacted with an instrumented high <span class="hlt">rate</span> dart impact tester and the bumpers impacted with a full scale bumper pendulum impact tester. Theoretical calculations and actual <span class="hlt">strain</span> <span class="hlt">rate</span> data support the conclusion that the <span class="hlt">strain</span> <span class="hlt">rate</span> of a plaque during dart impact significantly exceeds that of bumper <span class="hlt">strain</span> <span class="hlt">rate</span> during pendulum impact.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/875626','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/875626"><span id="translatedtitle">Servohydraulic methods for mechanical testing in the Sub-Hopkinson <span class="hlt">rate</span> regime up to <span class="hlt">strain</span> <span class="hlt">rates</span> of 500 1/s.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Crenshaw, Thomas B.; Boyce, Brad Lee</p> <p>2005-10-01</p> <p>Tensile and compressive stress-<span class="hlt">strain</span> experiments on metals at <span class="hlt">strain</span> <span class="hlt">rates</span> in the range of 1-1000 1/s are relevant to many applications such as gravity-dropped munitions and airplane accidents. While conventional test methods cover <span class="hlt">strain</span> <span class="hlt">rates</span> up to {approx}10 s{sup -1} and split-Hopkinson and other techniques cover <span class="hlt">strain</span> <span class="hlt">rates</span> in excess of {approx}1000 s{sup -1}, there are no well defined techniques for the intermediate or ''Sub-Hopkinson'' <span class="hlt">strain-rate</span> regime. The current work outlines many of the challenges in testing in the Sub-Hopkinson regime, and establishes methods for addressing these challenges. The resulting technique for obtaining intermediate <span class="hlt">rate</span> stress-<span class="hlt">strain</span> data is demonstrated in tension on a high-strength, high-toughness steel alloy (Hytuf) that could be a candidate alloy for earth penetrating munitions and in compression on a Au-Cu braze alloy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21903290','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21903290"><span id="translatedtitle"><span class="hlt">Effect</span> of dilution <span class="hlt">rate</span> and nutrients addition on the fermentative capability and synthesis of aromatic compounds of two indigenous <span class="hlt">strains</span> of Saccharomyces cerevisiae in continuous cultures fed with Agave tequilana juice.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Morán-Marroquín, G A; Córdova, J; Valle-Rodríguez, J O; Estarrón-Espinosa, M; Díaz-Montaño, D M</p> <p>2011-11-15</p> <p>Knowledge of physiological behavior of indigenous tequila yeast used in fermentation process is still limited. Yeasts have significant impact on the productivity fermentation process as well as the sensorial characteristics of the alcoholic beverage. For these reasons a better knowledge of the physiological and metabolic features of these yeasts is required. The <span class="hlt">effects</span> of dilution <span class="hlt">rate</span>, nitrogen and phosphorus source addition and micro-aeration on growth, fermentation and synthesis of volatile compounds of two native Saccharomyces cerevisiae <span class="hlt">strains</span>, cultured in continuous fed with Agave tequilana juice were studied. For S1 and S2 <span class="hlt">strains</span>, maximal concentrations of biomass, ethanol, consumed sugars, alcohols and esters were obtained at 0.04 h⁻¹. Those concentrations quickly decreased as D increased. For S. cerevisiae S1 cultures (at D=0.08 h⁻¹) supplemented with ammonium phosphate (AP) from 1 to 4 g/L, concentrations of residual sugars decreased from 29.42 to 17.60 g/L and ethanol increased from 29.63 to 40.08 g/L, respectively. The S1 culture supplemented with AP was then micro-aerated from 0 to 0.02 vvm, improving all the kinetics parameters: biomass, ethanol and glycerol concentrations increased from 5.66, 40.08 and 3.11 g/L to 8.04, 45.91 and 4.88 g/L; residual sugars decreased from 17.67 g/L to 4.48 g/L; and <span class="hlt">rates</span> of productions of biomass and ethanol, and consumption of sugars increased from 0.45, 3.21 and 7.33 g/L·h to 0.64, 3.67 and 8.38 g/L·h, respectively. Concentrations of volatile compounds were also influenced by the micro-aeration <span class="hlt">rate</span>. Ester and alcohol concentrations were higher, in none aerated and in aerated cultures respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050041969','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050041969"><span id="translatedtitle">Implementation of Improved Transverse Shear Calculations and Higher Order Laminate Theory Into <span class="hlt">Strain</span> <span class="hlt">Rate</span> Dependent Analyses of Polymer Matrix Composites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zhu, Lin-Fa; Kim, Soo; Chattopadhyay, Aditi; Goldberg, Robert K.</p> <p>2004-01-01</p> <p>A numerical procedure has been developed to investigate the nonlinear and <span class="hlt">strain</span> <span class="hlt">rate</span> dependent deformation response of polymer matrix composite laminated plates under high <span class="hlt">strain</span> <span class="hlt">rate</span> impact loadings. A recently developed strength of materials based micromechanics model, incorporating a set of nonlinear, <span class="hlt">strain</span> <span class="hlt">rate</span> dependent constitutive equations for the polymer matrix, is extended to account for the transverse shear <span class="hlt">effects</span> during impact. Four different assumptions of transverse shear deformation are investigated in order to improve the developed <span class="hlt">strain</span> <span class="hlt">rate</span> dependent micromechanics model. The validities of these assumptions are investigated using numerical and theoretical approaches. A method to determine through the thickness <span class="hlt">strain</span> and transverse Poisson's ratio of the composite is developed. The revised micromechanics model is then implemented into a higher order laminated plate theory which is modified to include the <span class="hlt">effects</span> of inelastic <span class="hlt">strains</span>. Parametric studies are conducted to investigate the mechanical response of composite plates under high <span class="hlt">strain</span> <span class="hlt">rate</span> loadings. Results show the transverse shear stresses cannot be neglected in the impact problem. A significant level of <span class="hlt">strain</span> <span class="hlt">rate</span> dependency and material nonlinearity is found in the deformation response of representative composite specimens.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26649476','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26649476"><span id="translatedtitle">Mechanical <span class="hlt">strain</span> <span class="hlt">effects</span> on black phosphorus nanoresonators.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Cui-Xia; Zhang, Chao; Jiang, Jin-Wu; Park, Harold S; Rabczuk, Timon</p> <p>2016-01-14</p> <p>We perform classical molecular dynamics simulations to investigate the <span class="hlt">effects</span> of mechanical <span class="hlt">strain</span> on single-layer black phosphorus nanoresonators at different temperatures. We find that the resonant frequency is highly anisotropic in black phosphorus due to its intrinsic puckered configuration, and that the quality factor in the armchair direction is higher than in the zigzag direction at room temperature. The quality factors are also found to be intrinsically larger than those in graphene and MoS2 nanoresonators. The quality factors can be increased by more than a factor of two by applying tensile <span class="hlt">strain</span>, with uniaxial <span class="hlt">strain</span> in the armchair direction being the most <span class="hlt">effective</span>. However, there is an upper bound for the quality factor increase due to nonlinear <span class="hlt">effects</span> at large <span class="hlt">strains</span>, after which the quality factor decreases. The tension induced nonlinear <span class="hlt">effect</span> is stronger along the zigzag direction, resulting in a smaller maximum <span class="hlt">strain</span> for quality factor enhancement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100002839','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100002839"><span id="translatedtitle">Fiber-Optic <span class="hlt">Strain</span> Gauge With High Resolution And Update <span class="hlt">Rate</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Figueroa, Fernando; Mahajan, Ajay; Sayeh, Mohammad; Regez, Bradley</p> <p>2007-01-01</p> <p>An improved fiber-optic <span class="hlt">strain</span> gauge is capable of measuring <span class="hlt">strains</span> in the approximate range of 0 to 50 microstrains with a resolution of 0.1 microstrain. (To some extent, the resolution of the <span class="hlt">strain</span> gauge can be tailored and may be extensible to 0.01 microstrain.) The total cost of the hardware components of this <span class="hlt">strain</span> gauge is less than $100 at 2006 prices. In comparison with prior <span class="hlt">strain</span> gauges capable of measurement of such low <span class="hlt">strains</span>, this <span class="hlt">strain</span> gauge is more accurate, more economical, and more robust, and it operates at a higher update <span class="hlt">rate</span>. <span class="hlt">Strain</span> gauges like this one are useful mainly for measuring small <span class="hlt">strains</span> (including those associated with vibrations) in such structures as rocket test stands, buildings, oilrigs, bridges, and dams. The technology was inspired by the need to measure very small <span class="hlt">strains</span> on structures supporting liquid oxygen tanks, as a way to measure accurately mass of liquid oxygen during rocket engine testing. This improved fiber-optic <span class="hlt">strain</span> gauge was developed to overcome some of the deficiencies of both traditional foil <span class="hlt">strain</span> gauges and prior fiber-optic <span class="hlt">strain</span> gauges. Traditional foil <span class="hlt">strain</span> gages do not have adequate signal-to-noise ratios at such small <span class="hlt">strains</span>. Fiber-optic <span class="hlt">strain</span> gauges have been shown to be potentially useful for measuring such small <span class="hlt">strains</span>, but heretofore, the use of fiberoptic <span class="hlt">strain</span> gauges has been inhibited, variously, by complexity, cost, or low update <span class="hlt">rate</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SMaS...25h5002P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SMaS...25h5002P"><span id="translatedtitle">Investigation of thermomechanical couplings, <span class="hlt">strain</span> localization and shape memory properties in a shape memory polymer subjected to loading at various <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pieczyska, E. A.; Staszczak, M.; Maj, M.; Kowalczyk-Gajewska, K.; Golasiński, K.; Cristea, M.; Tobushi, H.; Hayashi, S.</p> <p>2016-08-01</p> <p>This paper presents experimental and modeling results of the <span class="hlt">effects</span> of thermomechanical couplings occurring in a polyurethane shape memory polymer (SMP) subjected to tension at various <span class="hlt">strain</span> <span class="hlt">rates</span> within large <span class="hlt">strains</span>. The SMP mechanical curves, recorded using a testing machine, and the related temperature changes, measured in a contactless manner using an IR camera, were used to investigate the polymer deformation process at various loading stages. The <span class="hlt">effects</span> of thermomechanical couplings allowed the determination of the material yield point in the initial loading stage, the investigation of nucleation and development of the <span class="hlt">strain</span> localization at larger <span class="hlt">strains</span> and the estimation of the <span class="hlt">effects</span> of thermoelastic behavior during the unloading process. The obtained stress-<span class="hlt">strain</span> and thermal characteristics, the results of the dynamic mechanical analysis and estimated values of the shape fixity and shape recovery parameters confirmed that the shape memory polymer (T g = 45 °C) is characterized by good mechanical and shape memory properties, as well as high sensitivity to the <span class="hlt">strain</span> <span class="hlt">rate</span>. The mechanical response of the SMP subjected to tension was simulated using the finite element method and applying the large <span class="hlt">strain</span>, two-phase model. <span class="hlt">Strain</span> localization observed in the experiment was well reproduced in simulations and the temperature spots were correlated with the accumulated viscoplastic deformation of the SMP glassy phase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21178449','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21178449"><span id="translatedtitle">Local changes in <span class="hlt">rates</span> of group A Streptococcus disease and antibiotic resistance are associated with geographically widespread <span class="hlt">strain</span> turnover events.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Metzgar, David; McDonough, Erin A; Hansen, Christian J; Blaesing, Carl R; Baynes, Darcie; Hawksworth, Anthony W; Blair, Patrick J; Faix, Dennis J; Russell, Kevin L</p> <p>2010-01-01</p> <p>This study addresses the <span class="hlt">effects</span> of dynamic <span class="hlt">strain</span> turnover and antibiotic prophylaxis on <span class="hlt">rates</span> of group A Streptococcus (GAS) antibiotic resistance and disease. The authors analyzed the <span class="hlt">strain</span> distributions, disease <span class="hlt">rates</span>, and patterns of antibiotic resistance of 802 GAS isolates collected from 2002 through 2007. These samples were collected from patients with GAS infection symptoms at 10 military facilities. Macrolide resistance peaked at 25% during 2004, due to the geographically widespread dominance of a single resistant <span class="hlt">strain</span> (M75). The resistant <span class="hlt">strain</span> was not retained regardless of local patterns of macrolide use, and resistance <span class="hlt">rates</span> decreased upon replacement of M75 with macrolide-susceptible <span class="hlt">strains</span>. Disease <span class="hlt">rates</span> were similarly correlated with dominance of specific M types. Statistical analysis revealed temporal correlations between <span class="hlt">strain</span> distributions at multiple locations. Only the most common <span class="hlt">strains</span> yielded enough data at multiple sites for statistically significant comparison of temporal fluctuations in dominance, but these (including M44, M3, M18, M118, and M6) all yielded highly significant temporal correlations of 90% or greater on yearly scales. As expected given the complexity and variability of <span class="hlt">strain</span> distributions on shorter time scales, analysis on a monthly scale yielded lower degrees of positive correlation (31-62%), but in this case all significant correlations were still positive. Shifts in antibiotic resistance profiles and disease <span class="hlt">rates</span> at specific sites appear to be associated with <span class="hlt">strain</span> replacements happening on larger scales, independent of antibiotic use at individual sites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22303848','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22303848"><span id="translatedtitle">Yield strength dependence on <span class="hlt">strain</span> <span class="hlt">rate</span> of molybdenum-alloy nanofibers</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Loya, P. E.; Peng, C.; Zhang, P.; Zhang, J.; Lou, J.; Xia, Y. Z.; Bei, H.; George, E. P.; Gao, Y. F.</p> <p>2014-06-23</p> <p>The yield strength dependence on <span class="hlt">strain</span> <span class="hlt">rate</span> was studied for molybdenum-alloy nanofibers with varying initial dislocation density at three different pre-<span class="hlt">strain</span> levels. In-situ tensile experiments at three displacement <span class="hlt">rates</span> were carried out in a scanning electron microscope. Yield strength and its scatter decreased as a function of the pre-<span class="hlt">strain</span> level for different displacement <span class="hlt">rates</span>. A statistical model was used to analyze the results, and a negative <span class="hlt">strain</span> <span class="hlt">rate</span> dependence was inferred from the yield experiments. This finding suggests the need for theoretical investigations since classical models such as dynamic <span class="hlt">strain</span> aging may have limitations at such nanoscales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010JNuM..405...83E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JNuM..405...83E"><span id="translatedtitle">Modelling of the <span class="hlt">effect</span> of dislocation channel on intergranular microcrack nucleation in pre-irradiated austenitic stainless steels during low <span class="hlt">strain</span> <span class="hlt">rate</span> tensile loading</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Evrard, Pierre; Sauzay, Maxime</p> <p>2010-10-01</p> <p>In the present article, the <span class="hlt">effect</span> of dislocation channel on intergranular microcrack nucleation during the tensile deformation of pre-irradiated austenitic stainless steels is studied. Because several slip planes are activated within the dislocation channel, the simple dislocation pile-up model seems not well suited to predict grain boundary stress field. Finite element computations, using crystal plasticity laws and meshes including a channel of finite thickness, are also performed in order to study the <span class="hlt">effect</span> of some microstructural characteristics on grain boundary stress field. Numerical results show that: the thickness and the length of the dislocation channel influence strongly the grain boundary normal stress field. The grain boundary orientation with respect the stress axis does not affect so much the grain boundary normal stresses close to the dislocation channel. On the contrary far away the dislocation channel, the grain boundary stress field depends on the grain boundary orientation. Based on these numerical results, an analytical model is proposed to predict grain boundary stress fields. It is valuable for large ranges of dislocation channel thickness, length as well as applied stress. Then, a macroscopic microcrack nucleation criterion is deduced based on the elastic-brittle Griffith model. The proposed criterion predicts correctly the influence of grain boundary characteristics (low-angle boundaries (LABs), non-coincident site lattice (non-CSL) high-angle boundaries (HABs), special grain boundaries (GBs)) on intergranular microcrack nucleation and the macroscopic tensile stress required for grain boundary microcrack nucleation for pre-irradiated austenitic stainless steels deformed in argon environment. The criterion based on a dislocation pile-up model (Smith and Barnby) underestimates strongly the nucleation stress. These results confirm that pile-up models are not well suited to predict microcrack nucleation stress in the case of dislocation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/1158105','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/1158105"><span id="translatedtitle">Longevity, growth <span class="hlt">rate</span> and related traits among <span class="hlt">strains</span> of Tribolium castaneum.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Soliman, M H; Lints, F A</p> <p>1975-01-01</p> <p>Longevity of eight laboratory <span class="hlt">strains</span> of the flour beetle Tribolium castaneum, with various geographic backgrounds, was studied under constant laboratory conditions of 33 degrees C and 70% relative humidity in standard medium (95% whole wheat flour and 5% dried yeast) during a period of 227 days starting from the egg stage. The eggs were collected from the same parents, first a few days after emergence and afterwards at intervals of 13, 9, 10 and 11 days. Mean survival time (MST) was found to be <span class="hlt">strain</span>-specified. It ranges from 128.6 days for KJ (Kyoto, Japan) to 174.2 days for ES (Edinburgh, Scotland). MST was highly correlated with the percentage of adults alive after 227 days, which did not change the ranking order of <span class="hlt">strain</span> longevity. Parental age had no <span class="hlt">effect</span> on longevity. The mean adult longevity of the <span class="hlt">strains</span> was correlated with the available data on adult weight, growth <span class="hlt">rate</span>, viability and productivity. There was no relationship between adult weight and longevity. LIfe span was found to depend on growth <span class="hlt">rate</span> (measured as 13-day larval weight), percent viability (from 13-day larvae to adulthood) and productivity. Developmental time was also found to influence adult life span within certain limits (two extreme <span class="hlt">strains</span> deviated). The data suggest that ageing and death in T. castaneum is under genetic control and support the idea that ageing, allied to development, is genetically controlled.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/376399','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/376399"><span id="translatedtitle">Influence of high-<span class="hlt">strain</span> <span class="hlt">rate</span> and temperature on the mechanical behavior of Nl-, Fe-, and Ti- based aluminides</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gray, G.T. III</p> <p>1996-09-01</p> <p>The majority of the strength characterization studies on ordered intermetallics have concentrated on the assessment of strength and work-hardening at conventional <span class="hlt">strain</span> <span class="hlt">rates</span>. Although the influence of <span class="hlt">strain</span> <span class="hlt">rate</span> on the structure/property relationships of pure nickel, iron, and titanium and a variety of their alloys have been extensively studied, the <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> on the stress-<span class="hlt">strain</span> response of Ni-, Fe-, and Ti-based aluminides remains poorly understood. Dynamic constitutive behavior is however relevant to high speed impact performance of these materials such as during foreign object damage in aerospace applications, high-<span class="hlt">rate</span> forging, and localized deformation behavior during machining. The influence of <span class="hlt">strain</span> <span class="hlt">rate</span>, varied between 0.001 and 10{sup 4} s{sup -1}, and temperatures, between 77 & 800K, on the compressive mechanical behavior of Ni{sub 3}A1, NiAl, Fe{sub 3}Al, Fe-40Al-0.1B, Ti-24Al-11Nb, and Ti-48Al-2Cr-2Nb will be presented. In this paper the influence of <span class="hlt">strain</span> <span class="hlt">rate</span> on the anomalous temperature dependency of the flow stresses in these aluminides will be reviewed and compared between aluminides. The <span class="hlt">rate</span> sensitivity and work hardening of each aluminide will be discussed as a function of <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature and contrasted to each other and to the values typical for their respective disordered base metals. 66 refs., 16 figs., 2 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/973332','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/973332"><span id="translatedtitle">High-<span class="hlt">rate</span> Plastic Deformation of Nanocrystalline Tantalum to Large <span class="hlt">Strains</span>: Molecular Dynamics Simulation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rudd, R E</p> <p>2009-02-05</p> <p>Recent advances in the ability to generate extremes of pressure and temperature in dynamic experiments and to probe the response of materials has motivated the need for special materials optimized for those conditions as well as a need for a much deeper understanding of the behavior of materials subjected to high pressure and/or temperature. Of particular importance is the understanding of <span class="hlt">rate</span> <span class="hlt">effects</span> at the extremely high <span class="hlt">rates</span> encountered in those experiments, especially with the next generation of laser drives such as at the National Ignition Facility. Here we use large-scale molecular dynamics (MD) simulations of the high-<span class="hlt">rate</span> deformation of nanocrystalline tantalum to investigate the processes associated with plastic deformation for <span class="hlt">strains</span> up to 100%. We use initial atomic configurations that were produced through simulations of solidification in the work of Streitz et al [Phys. Rev. Lett. 96, (2006) 225701]. These 3D polycrystalline systems have typical grain sizes of 10-20 nm. We also study a rapidly quenched liquid (amorphous solid) tantalum. We apply a constant volume (isochoric), constant temperature (isothermal) shear deformation over a range of <span class="hlt">strain</span> <span class="hlt">rates</span>, and compute the resulting stress-<span class="hlt">strain</span> curves to large <span class="hlt">strains</span> for both uniaxial and biaxial compression. We study the <span class="hlt">rate</span> dependence and identify plastic deformation mechanisms. The identification of the mechanisms is facilitated through a novel technique that computes the local grain orientation, returning it as a quaternion for each atom. This analysis technique is robust and fast, and has been used to compute the orientations on the fly during our parallel MD simulations on supercomputers. We find both dislocation and twinning processes are important, and they interact in the weak <span class="hlt">strain</span> hardening in these extremely fine-grained microstructures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014SPIE.9061E..31R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SPIE.9061E..31R"><span id="translatedtitle">Distributed <span class="hlt">strain</span> monitoring for bridges: temperature <span class="hlt">effects</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Regier, Ryan; Hoult, Neil A.</p> <p>2014-03-01</p> <p>To better manage infrastructure assets as they reach the end of their service lives, quantitative data is required to better assess structural behavior and allow for more informed decision making. Distributed fiber optic <span class="hlt">strain</span> sensors are one sensing technology that could provide comprehensive data for use in structural assessments as these systems potentially allow for <span class="hlt">strain</span> to be measured with the same accuracy and gage lengths as conventional <span class="hlt">strain</span> sensors. However, as with many sensor technologies, temperature can play an important role in terms of both the structure's and sensor's performance. To investigate this issue a fiber optic distributed <span class="hlt">strain</span> sensor system was installed on a section of a two span reinforced concrete bridge on the TransCanada Highway. <span class="hlt">Strain</span> data was acquired several times a day as well as over the course of several months to explore the <span class="hlt">effects</span> of changing temperature on the data. The results show that the <span class="hlt">strain</span> measurements are affected by the bridge behavior as a whole. The <span class="hlt">strain</span> measurements due to temperature are compared to <span class="hlt">strain</span> measurements that were taken during a load test on the bridge. The results show that even a small change in temperature can produce crack width and <span class="hlt">strain</span> changes similar to those due to a fully loaded transport truck. Future directions for research in this area are outlined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA559004','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA559004"><span id="translatedtitle">DEET Insect Repellent: <span class="hlt">Effects</span> on Thermoregulatory Sweating and Physiological <span class="hlt">Strain</span></span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2011-01-01</p> <p>s sampling <span class="hlt">rate</span> was selected as this interval is well within the latency period that extends between sweat gland stimulation and sweat emergence...code) 2011 Journal Article-Eur Journal of Applied Physiology DEET insect repellent: <span class="hlt">effects</span> on thermoregulatory sweating and physiological <span class="hlt">strain</span> R.W...toluamide or DEET) applied to the skin can potentially interfere with sweat production and evaporation, thus increasing physiological <span class="hlt">strain</span> during</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA041560','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA041560"><span id="translatedtitle">Tensile Stress-<span class="hlt">Strain</span> Curves--III, Rolled Homogeneous Armor at a <span class="hlt">Strain</span> <span class="hlt">Rate</span> of 0.042 per second</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1977-06-01</p> <p>adhesive. The gage resistance is nominally 120 ohms and the nominal gage factor is 2.03. One <span class="hlt">strain</span> gage pair measured the axial <span class="hlt">strain</span>, the second gage...Proving Ground , MD, November 1976. AD #B0~6015L 8. G. E. Hauver, "The Alpha Phase Hugoniot of Rolled Homogeneous Armor ", BRL Memorandum Report No...1 i ’ ! .,: MEMORANDUM REPORT NO. 2760 "" ’ l TENSILE STRESS-<span class="hlt">STRAIN</span> CURVES--Ill, ROLLED HOMOGENEOUS ARMOR AT A <span class="hlt">STRAIN</span> <span class="hlt">RATE</span> OF 0.42 S-l Ralph</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003JPhy4.110...63H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003JPhy4.110...63H"><span id="translatedtitle">Continuum damage modeling for ductile metals under high <span class="hlt">strain</span> <span class="hlt">rate</span> deformation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Husson, C.; Ahzi, S.; Daridon, L.; Courtine, T.</p> <p>2003-09-01</p> <p>The accuracy of the computational investigation on the response of ductile materials under dynamic condition depends on the capability of the constitutive model in accounting for <span class="hlt">strain</span> <span class="hlt">rate</span>, temperature and microstructural <span class="hlt">effects</span>. In this work, we propose a damage evolution law, valid for a wide range of <span class="hlt">strain</span> <span class="hlt">rates</span>, based on the theory of continuum damage mechanics (CDM). This model implicitly accounts for the three stages of damage: the nucleation, the growth and the coalescence. This non-linear isotropic CDM model for ductile damage is developed by assuming the existence of a new ductile damage dissipation potential. The proposed damage law is coupled with an evolution law for the flow stress. Like in the mechanical threshold stress (M.T.S.) model, the flow stress is decomposed as the sum of an athermal component and a temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> dependent component. Results from our motel are in agreement with the existing experimental results for stress-<span class="hlt">strain</span> behavior and damage evolution in oxygen-free high-conducting (OFHC) copper under both quasi-static and dynamic loading conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.S51A4412K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.S51A4412K"><span id="translatedtitle">Predicting Offshore Swarm <span class="hlt">Rate</span> Changes by Volumetric <span class="hlt">Strain</span> Changes in Izu Peninsula, Japan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kumazawa, T.; Ogata, Y.; Kimura, Y.; Maeda, K.; Kobayashi, A.</p> <p>2014-12-01</p> <p>The eastern offshore of Izu peninsula is one of the well known volcanic active regions in Japan, where magma intrusions have been observed several times since 1980s monitored by <span class="hlt">strain</span>-meters located nearby. Major swarm activities have been synchronously associated with coseismic and preseismic significant sizes of a volumetric <span class="hlt">strain</span> changes (Earthquake Research Committee, 2010). We investigated the background seismicity changes during these earthquake swarms using the nonstationary ETAS model (Kumazawa and Ogata, 2013), and have found the followings. The modified volumetric <span class="hlt">strain</span> change data by removing the <span class="hlt">effect</span> of earth tides and precipitation as well as removing coseismic jumps have much higher cross-correlations to the background <span class="hlt">rates</span> of the ETAS model than to the whole seismicity <span class="hlt">rate</span> change of the ETAS, and further the <span class="hlt">strain</span> changes precede the background seismicity by lag of about a day. This relation suggests an enhanced prediction of earthquakes in this region using volumetric <span class="hlt">strain</span> measurements. Thus we propose an extended ETAS model where the background seismicity <span class="hlt">rate</span> is predicted by the time series of preceding volumetric <span class="hlt">strain</span> changes. Our numerical results for Izu region show consistent outcomes throughout the major swarms in this region. References Earthquake Research Committee (2010). Report on "Prediction of seismic activity in the Izu Eastern Region" (in Japanese), http://www.jishin.go.jp/main/yosoku/izu/index.htm Kumazawa, T. and Ogata, Y. (2013). Quantitative description of induced seismic activity before and after the 2011 Tohoku-Oki earthquake by nonstationary ETAS model, J Geophys.Res. 118, 6165-6182.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..SHK.H6004T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..SHK.H6004T"><span id="translatedtitle">Modelling and Simulation of Dynamic Recrystallization (DRX) In OFHC Copper at Very High <span class="hlt">Strain</span> <span class="hlt">Rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Testa, Gabriel; Bonora, Nicola; Ruggiero, Andrew; Iannitti, Gianluca; Hörnqvist, Magnus; Mortazavi, Nooshin</p> <p>2015-06-01</p> <p>At high <span class="hlt">strain</span> <span class="hlt">rates</span>, the deformation process is essentially adiabatic and if the plastic work is large enough, dynamic recrystallization can occur. In this work, an examination on microstructure evolution in Dynamic Tensile Extrusion (DTE) test of OFHC copper, performed at 400 m/s, was carried out. EBSD investigations, along the center line of the fragment remaining in the extrusion die, showed a progressive elongation of the grains, and an accompanying development of a strong < 001 > + < 111 > dual fiber texture. Meta-dynamic discontinuous dynamic recrystallization (DRX) occurred at larger <span class="hlt">strains</span>, and it was showed that nucleation occurred during <span class="hlt">straining</span>. A criterion, based on the evolution of Zener-Hollomon parameter during the dynamic deformation process, was proposed. Finally, DTE test was simulated using the modified Rusinek-Klepaczko constitutive model incorporating restoring <span class="hlt">effects</span> induced by recrystallization processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/936455','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/936455"><span id="translatedtitle">Material dynamics under extreme conditions of pressure and <span class="hlt">strain</span> <span class="hlt">rate</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Remington, B A; Allen, P; Bringa, E; Hawreliak, J; Ho, D; Lorenz, K T; Lorenzana, H; Meyers, M A; Pollaine, S W; Rosolankova, K; Sadik, B; Schneider, M S; Swift, D; Wark, J; Yaakobi, B</p> <p>2005-09-06</p> <p>Solid state experiments at extreme pressures (10-100 GPa) and <span class="hlt">strain</span> <span class="hlt">rates</span> ({approx}10{sup 6}-10{sup 8}s{sup -1}) are being developed on high-energy laser facilities, and offer the possibility for exploring new regimes of materials science. These extreme solid-state conditions can be accessed with either shock loading or with a quasi-isentropic ramped pressure drive. Velocity interferometer measurements establish the high pressure conditions. Constitutive models for solid-state strength under these conditions are tested by comparing 2D continuum simulations with experiments measuring perturbation growth due to the Rayleigh-Taylor instability in solid-state samples. Lattice compression, phase, and temperature are deduced from extended x-ray absorption fine structure (EXAFS) measurements, from which the shock-induced {alpha}-{omega} phase transition in Ti and the {alpha}-{var_epsilon} phase transition in Fe are inferred to occur on sub-nanosec time scales. Time resolved lattice response and phase can also be measured with dynamic x-ray diffraction measurements, where the elastic-plastic (1D-3D) lattice relaxation in shocked Cu is shown to occur promptly (< 1 ns). Subsequent large-scale molecular dynamics (MD) simulations elucidate the microscopic dynamics that underlie the 3D lattice relaxation. Deformation mechanisms are identified by examining the residual microstructure in recovered samples. The slip-twinning threshold in single-crystal Cu shocked along the [001] direction is shown to occur at shock strengths of {approx}20 GPa, whereas the corresponding transition for Cu shocked along the [134] direction occurs at higher shock strengths. This slip-twinning threshold also depends on the stacking fault energy (SFE), being lower for low SFE materials. Designs have been developed for achieving much higher pressures, P > 1000 GPa, in the solid state on the National Ignition Facility (NIF) laser.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/671890','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/671890"><span id="translatedtitle">Chemical response of methane/air diffusion flames to unsteady <span class="hlt">strain</span> <span class="hlt">rate</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Im, H.G.; Chen, J.H.; Chen, J.Y.</p> <p>1998-03-01</p> <p><span class="hlt">Effects</span> of unsteady <span class="hlt">strain</span> <span class="hlt">rate</span> on the response of methane/air diffusion flames are studied. The authors use the finite-domain opposed flow configuration in which the nozzle exit velocity is imposed as a function of time. The GRI mechanism v2.11 is used for the detailed methane/air chemistry. The response of individual species to monochromatic oscillation in <span class="hlt">strain</span> <span class="hlt">rate</span> with various frequencies reveals that the fluctuation of slow species, such as CO and NO{sub x}, is more rapidly suppressed as the flow time scale decreases. It is also observed that the maximum CO concentration is very insensitive to the variation in the scalar dissipation <span class="hlt">rate</span>. An extinction event due to an abrupt imposition of high <span class="hlt">strain</span> <span class="hlt">rates</span> is also simulated by an impulsive velocity with various frequencies. For a fast impulse, a substantial overshoot in NO{sub 2} concentration is observed after extinction. Finally, the overall fuel burning <span class="hlt">rate</span> shows a nonmonotonic response to the variation in characteristic unsteady time scale, while the emission indices for NO{sub x} shows monotonic decay in response as frequency is increased.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA305387','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA305387"><span id="translatedtitle">High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Properties of Angle Ply Composite Laminates,</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1981-11-01</p> <p>properties, dynamic stress-<span class="hlt">strain</span> curvesUnlsiedUlmtd For sale by the National Technical Information Service. Sprinefield. Virginia 2?161 NASA-C.168 (Rev 10-7S...<span class="hlt">Strain</span> records in steel ring and [±1 5]p2 SP288/AS graphite/epoxy ring under dynamic loadTng for Specimen No. 35-10 (0.65 g shotgun powder). 3-23 3-3...<span class="hlt">Strain</span> records in steel ring and [±151 2 SP288/AS graphite/epoxy ring under dynamic loading for Specimen No. 35-11 (0.65 g shotgun powder). 3-24 3-4 Stress</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920035353&hterms=milford&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmilford','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920035353&hterms=milford&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dmilford"><span id="translatedtitle">Slow <span class="hlt">strain</span> <span class="hlt">rate</span> 1200-1400 K compressive properties of NiAl-1Hf</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Whittenberger, J. D.; Nathal, M. V.; Raj, S. V.; Pathare, V. M.</p> <p>1991-01-01</p> <p>Compression tests are conducted on NiAl-1Hf to assess the elevated-temperature creep behavior of this precipitation-hardened aluminide. While the strength is high under fast <span class="hlt">strain</span> <span class="hlt">rates</span> (more than 10 exp -5/s), under slower conditions the alloy is weak. Thus, it is unlikely that <span class="hlt">effective</span> creep resistance can be obtained in NiAl through small Hf additions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26275487','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26275487"><span id="translatedtitle">Investigation of the mechanical behavior of kangaroo humeral head cartilage tissue by a porohyperelastic model based on the <span class="hlt">strain-rate</span>-dependent permeability.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thibbotuwawa, Namal; Oloyede, Adekunle; Senadeera, Wijitha; Li, Tong; Gu, YuanTong</p> <p>2015-11-01</p> <p>Solid-interstitial fluid interaction, which depends on tissue permeability, is significant to the <span class="hlt">strain-rate</span>-dependent mechanical behavior of humeral head (shoulder) cartilage. Due to anatomical and biomechanical similarities to that of the human shoulder, kangaroos present a suitable animal model. Therefore, indentation experiments were conducted on kangaroo shoulder cartilage tissues from low (10(-4)/s) to moderately high (10(-2)/s) <span class="hlt">strain-rates</span>. A porohyperelastic model was developed based on the experimental characterization; and a permeability function that takes into account the <span class="hlt">effect</span> of <span class="hlt">strain-rate</span> on permeability (<span class="hlt">strain-rate</span>-dependent permeability) was introduced into the model to investigate the <span class="hlt">effect</span> of <span class="hlt">rate</span>-dependent fluid flow on tissue response. The prediction of the model with the <span class="hlt">strain-rate</span>-dependent permeability was compared with those of the models using constant permeability and <span class="hlt">strain</span>-dependent permeability. Compared to the model with constant permeability, the models with <span class="hlt">strain</span>-dependent and <span class="hlt">strain-rate</span>-dependent permeability were able to better capture the experimental variation at all <span class="hlt">strain-rates</span> (p < 0.05). Significant differences were not identified between models with <span class="hlt">strain</span>-dependent and <span class="hlt">strain-rate</span>-dependent permeability at <span class="hlt">strain-rate</span> of 5 × 10(-3)/s (p = 0.179). However, at <span class="hlt">strain-rate</span> of 10(-2)/s, the model with <span class="hlt">strain-rate</span>-dependent permeability was significantly better at capturing the experimental results (p < 0.005). The findings thus revealed the significance of <span class="hlt">rate</span>-dependent fluid flow on tissue behavior at large <span class="hlt">strain-rates</span>, which provides insights into the mechanical deformation mechanisms of cartilage tissues.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/364023','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/364023"><span id="translatedtitle">The variation of the yield stress of Ti alloys with <span class="hlt">strain</span> <span class="hlt">rate</span> at high temperatures</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rosen, R.S.; Paddon, S.P.; Kassner, M.E.</p> <p>1999-06-01</p> <p>This study extended investigation on the elevated-temperature yield-strength dependence of beta-phase titanium alloys on <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature. Yield stresses were found to increase substantially with increasing <span class="hlt">strain</span> <span class="hlt">rate</span> at elevated temperatures due to the high <span class="hlt">strain-rate</span> sensitivity of titanium at high temperatures. Above 1000 C, the <span class="hlt">strain-rate</span> sensitivities were found to increase substantially with increasing temperature and/or decreasing <span class="hlt">strain</span> <span class="hlt">rate</span>. The six alloys examined were TIMETAL 21S, Ti-15-3-, Ti-6-4, Ti-13-11-3, Beta C, and Beta III. There was particular interest in determining the <span class="hlt">strain-rate</span> sensitivity of these alloys through <span class="hlt">strain-rate</span> change tests above 1000 C. The yield stresses of all the titanium alloys at temperatures above 1093 C were less than 1% of their ambient temperature values. <span class="hlt">strain</span> hardening was negligible in the alloys tested at these high temperatures. Extended tensile ductilities of 100 to 200% were observed due to the pronounced <span class="hlt">strain</span>-rare sensitivity. The <span class="hlt">rate</span> controlling mechanism for plasticity, based on activation energy and the <span class="hlt">strain-rate</span> sensitivity measurements, is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25723227','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25723227"><span id="translatedtitle">Grain-size-independent plastic flow at ultrahigh pressures and <span class="hlt">strain</span> <span class="hlt">rates</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Park, H-S; Rudd, R E; Cavallo, R M; Barton, N R; Arsenlis, A; Belof, J L; Blobaum, K J M; El-dasher, B S; Florando, J N; Huntington, C M; Maddox, B R; May, M J; Plechaty, C; Prisbrey, S T; Remington, B A; Wallace, R J; Wehrenberg, C E; Wilson, M J; Comley, A J; Giraldez, E; Nikroo, A; Farrell, M; Randall, G; Gray, G T</p> <p>2015-02-13</p> <p>A basic tenet of material science is that the flow stress of a metal increases as its grain size decreases, an <span class="hlt">effect</span> described by the Hall-Petch relation. This relation is used extensively in material design to optimize the hardness, durability, survivability, and ductility of structural metals. This Letter reports experimental results in a new regime of high pressures and <span class="hlt">strain</span> <span class="hlt">rates</span> that challenge this basic tenet of mechanical metallurgy. We report measurements of the plastic flow of the model body-centered-cubic metal tantalum made under conditions of high pressure (>100  GPa) and <span class="hlt">strain</span> <span class="hlt">rate</span> (∼10(7)  s(-1)) achieved by using the Omega laser. Under these unique plastic deformation ("flow") conditions, the <span class="hlt">effect</span> of grain size is found to be negligible for grain sizes >0.25  μm sizes. A multiscale model of the plastic flow suggests that pressure and <span class="hlt">strain</span> <span class="hlt">rate</span> hardening dominate over the grain-size <span class="hlt">effects</span>. Theoretical estimates, based on grain compatibility and geometrically necessary dislocations, corroborate this conclusion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5126507','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5126507"><span id="translatedtitle">The high-<span class="hlt">strain-rate</span> and spallation response of tantalum, Ta-10W, and T-111</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gray, G.T. III; Rollett, A.D.</p> <p>1991-01-01</p> <p>The compressive true stress-true response of tantalum, Ta-10W, and T-111 were found to depend on the applied <span class="hlt">strain</span> <span class="hlt">rate</span>, in the range 0.001 to 7000 s{sup {minus}1}. The <span class="hlt">strain-rate</span> sensitivities of the flow stress of tantalum, Ta-10W, and T-111 a 1% <span class="hlt">strain</span> are 0.062, 0.031, and 0.024, respectively. The <span class="hlt">rates</span> of <span class="hlt">strain</span> hardening in Tantalum, Ta-10W, and T-111 are seen to exhibit differing behavior with increasing <span class="hlt">strain</span> <span class="hlt">rate</span>. The calculated average <span class="hlt">strain</span>-hardening <span class="hlt">rate</span> in tantalum, {Theta}, for the quasi-static (0.001 s{sup {minus}1}) data at 25{degrees}C is 2080 MPa/unit <span class="hlt">strain</span>. The hardening <span class="hlt">rate</span> at 3000s{sup {minus}1} at 25{degrees}C decreases to 846 MPa/unit <span class="hlt">strain</span>. Normalizing the work hardening <span class="hlt">rate</span> in tantalum with the Taylor Factor for a random polycrystal, ({Theta} / (3.07){sup 2}), yields work hardening <span class="hlt">rates</span> of {mu}/276 at quasi-static <span class="hlt">strain</span> <span class="hlt">rates</span> and {mu}/680 at high-<span class="hlt">rates</span>, assuming a shear modulus of 61 GPa for tantalum at room temperature. While the work hardening of all the tantalum-based materials are similar at quasi-static <span class="hlt">rates</span>, alloying results in a small reduction in hardening <span class="hlt">rate</span>. With increasing <span class="hlt">strain</span> <span class="hlt">rate</span>, the work hardening <span class="hlt">rate</span> in tantalum decreases by approximately a factor of two compared to the alloys. Alloying tantalum with substitutional or interstitial elements is thought to result in increased edge dislocation storage and screw dislocation cross-slip due to interactions with the alloying elements at high <span class="hlt">strain</span> <span class="hlt">rates</span>. 28 refs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA430675','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA430675"><span id="translatedtitle">A Miniaturized Split Hopkinson Pressure Bar for Very High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Testing</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2004-03-01</p> <p>AFRL-MN-EG-TR-2005-7014 A Miniaturized Split Hopkinson Pressure Bar for Very High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Testing Clive R. Siviour Physics and Chemistry of...Very High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Testing 5. FUNDING NUMBERS PE: 61102F 6. AUTHOR(S) Clive R. Siviour, Jennifer L. Jordan PR: 2302...Measurements of material properties at very high <span class="hlt">rates</span> of <span class="hlt">strain</span> give an important insight into the structure of these materials, as well as</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013APS..SHK.W1005P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APS..SHK.W1005P"><span id="translatedtitle">Plastic flow, inferred strength, and incipient failure in BCC metals at high pressures, <span class="hlt">strains</span>, and <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Park, Hye-Sook</p> <p>2013-06-01</p> <p>We present our extensive experimental results from the Omega laser to test models of high pressure, high <span class="hlt">strain</span> <span class="hlt">rate</span> strength at ~1 Mbar peak pressures, <span class="hlt">strains</span> >10%, and <span class="hlt">strain</span> <span class="hlt">rates</span> of ~107 s-1 in Ta, V, and Fe, using plastic flows driven by the Rayleigh-Taylor instability. The observed time evolution of the plastic deformation is compared with 2D simulations incorporating a strength model. This methodology allows average values of strength at peak pressure and peak <span class="hlt">strain</span> <span class="hlt">rate</span> conditions to be inferred. The observed values of strength are typically factors of 5-10 higher than ambient strength, with contributions coming from pressure hardening (via the shear modulus), and <span class="hlt">strain</span> <span class="hlt">rate</span> hardening. For Fe, there is the added contribution from the alpha-epsilon phase transition. Ta has been studied as a function of grain size, and at the high <span class="hlt">strain</span> <span class="hlt">rates</span> and short durations of the experiments, no grain size dependence was observed; the observed deformation and inferred strength were independent of grain size. Both Ta and V have been driven to large enough <span class="hlt">strains</span> that incipient failure (softening) has been observed. Both the Ta and V experiments were compared favorably with multiscale strength models, with the conclusion that the Ta deformation was in the thermal activation regime, whereas the V deformation was in the phonon drag regime. Finally, preliminary results of new iron RT strength experiments done at ~1 Mbar pressures, and ~107 s-1 <span class="hlt">strain</span> <span class="hlt">rates</span>, well beyond the alpha-epsilon phase transition, will be given. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=standardized+AND+testing&pg=5&id=EJ914088','ERIC'); return false;" href="http://eric.ed.gov/?q=standardized+AND+testing&pg=5&id=EJ914088"><span id="translatedtitle">Sequential <span class="hlt">Effects</span> in Essay <span class="hlt">Ratings</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Attali, Yigal</p> <p>2011-01-01</p> <p>Contrary to previous research on sequential <span class="hlt">ratings</span> of student performance, this study found that professional essay raters of a large-scale standardized testing program produced <span class="hlt">ratings</span> that were drawn toward previous <span class="hlt">ratings</span>, creating an assimilation <span class="hlt">effect</span>. Longer intervals between the two adjacent <span class="hlt">ratings</span> and higher degree of agreement with…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1345315-modeling-grain-size-strengthening-tantalum-high-pressures-strain-rates','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1345315-modeling-grain-size-strengthening-tantalum-high-pressures-strain-rates"><span id="translatedtitle">Modeling of grain size strengthening in tantalum at high pressures and <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Rudd, Robert E.; Park, H. -S.; Cavallo, R. M.; ...</p> <p>2017-01-01</p> <p>Laser-driven ramp wave compression experiments have been used to investigate the strength (flow stress) of tantalum and other metals at high pressures and high <span class="hlt">strain</span> <span class="hlt">rates</span>. Recently this kind of experiment has been used to assess the dependence of the strength on the average grain size of the material, finding no detectable variation with grain size. The insensitivity to grain size has been understood theoretically to result from the dominant <span class="hlt">effect</span> of the high dislocation density generated at the extremely high <span class="hlt">strain</span> <span class="hlt">rates</span> of the experiment. Here we review the experiments and describe in detail the multiscale strength model usedmore » to simulate them. The multiscale strength model has been extended to include the <span class="hlt">effect</span> of geometrically necessary dislocations generated at the grain boundaries during compatible plastic flow in the polycrystalline metal. Lastly, we use the extended model to make predictions of the threshold <span class="hlt">strain</span> <span class="hlt">rates</span> and grain sizes below which grain size strengthening would be observed in the laser-driven Rayleigh-Taylor experiments.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1345315','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1345315"><span id="translatedtitle">Modeling of grain size strengthening in tantalum at high pressures and <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rudd, Robert E.; Park, H. -S.; Cavallo, R. M.; Arsenlis, A.; Orlikowski, D. A.; Prisbrey, S. T.; Wehrenberg, C. E.; Remington, B. A.</p> <p>2017-01-01</p> <p>Laser-driven ramp wave compression experiments have been used to investigate the strength (flow stress) of tantalum and other metals at high pressures and high <span class="hlt">strain</span> <span class="hlt">rates</span>. Recently this kind of experiment has been used to assess the dependence of the strength on the average grain size of the material, finding no detectable variation with grain size. The insensitivity to grain size has been understood theoretically to result from the dominant <span class="hlt">effect</span> of the high dislocation density generated at the extremely high <span class="hlt">strain</span> <span class="hlt">rates</span> of the experiment. Here we review the experiments and describe in detail the multiscale strength model used to simulate them. The multiscale strength model has been extended to include the <span class="hlt">effect</span> of geometrically necessary dislocations generated at the grain boundaries during compatible plastic flow in the polycrystalline metal. Lastly, we use the extended model to make predictions of the threshold <span class="hlt">strain</span> <span class="hlt">rates</span> and grain sizes below which grain size strengthening would be observed in the laser-driven Rayleigh-Taylor experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1793k0004R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1793k0004R"><span id="translatedtitle">Modeling of grain size strengthening in tantalum at high pressures and <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rudd, Robert E.; Park, H.-S.; Cavallo, R. M.; Arsenlis, A.; Orlikowski, D. A.; Prisbrey, S. T.; Wehrenberg, C. E.; Remington, B. A.</p> <p>2017-01-01</p> <p>Laser-driven ramp wave compression experiments have been used to investigate the strength (flow stress) of tantalum and other metals at high pressures and high <span class="hlt">strain</span> <span class="hlt">rates</span>. Recently this kind of experiment has been used to assess the dependence of the strength on the average grain size of the material, finding no detectable variation with grain size. The insensitivity to grain size has been understood theoretically to result from the dominant <span class="hlt">effect</span> of the high dislocation density generated at the extremely high <span class="hlt">strain</span> <span class="hlt">rates</span> of the experiment. Here we review the experiments and describe in detail the multiscale strength model used to simulate them. The multiscale strength model has been extended to include the <span class="hlt">effect</span> of geometrically necessary dislocations generated at the grain boundaries during compatible plastic flow in the polycrystalline metal. We use the extended model to make predictions of the threshold <span class="hlt">strain</span> <span class="hlt">rates</span> and grain sizes below which grain size strengthening would be observed in the laser-driven Rayleigh-Taylor experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22846301','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22846301"><span id="translatedtitle">Method for obtaining simple shear material properties of the intervertebral disc under high <span class="hlt">strain</span> <span class="hlt">rates</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ott, Kyle A; Armiger, Robert S; Wickwire, Alexis C; Carneal, Catherine M; Trexler, Morgana M; Lennon, Andrew M; Zhang, Jiangyue; Merkle, Andrew C</p> <p>2012-01-01</p> <p>Predicting spinal injury under high <span class="hlt">rates</span> of vertical loading is of interest, but the success of computational models in modeling this type of loading scenario is highly dependent on the material models employed. Understanding the response of these biological materials at high <span class="hlt">strain</span> <span class="hlt">rates</span> is critical to accurately model mechanical response of tissue and predict injury. While data exists at lower <span class="hlt">strain</span> <span class="hlt">rates</span>, there is a lack of the high <span class="hlt">strain</span> <span class="hlt">rate</span> material data that are needed to develop constitutive models. The Split Hopkinson Pressure Bar (SHPB) has been used for many years to obtain properties of various materials at high <span class="hlt">strain</span> <span class="hlt">rates</span>. However, this apparatus has mainly been used for characterizing metals and ceramics and is difficult to apply to softer materials such as biological tissue. Recently, studies have shown that modifications to the traditional SHPB setup allow for the successful characterization of mechanical properties of biological materials at <span class="hlt">strain</span> <span class="hlt">rates</span> and peak <span class="hlt">strain</span> values that exceed alternate soft tissue testing techniques. In this paper, the previously-reported modified SHPB technique is applied to characterize human intervertebral disc material under simple shear. The <span class="hlt">strain</span> <span class="hlt">rates</span> achieved range from 5 to 250 <span class="hlt">strain</span> s-1. The results demonstrate the sensitivity to the disc composition and structure, with the nucleus pulposus and annulus fibrosus exhibiting different behavior under shear loading. Shear tangent moduli are approximated at varying <span class="hlt">strain</span> levels from 5 to 20% <span class="hlt">strain</span>. This data and technique facilitates determination of mechanical properties of intervertebral disc materials under shear loading, for eventual use in constitutive models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013RMRE...46..373H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013RMRE...46..373H"><span id="translatedtitle">Numerical Investigation of the Dynamic Compressive Behaviour of Rock Materials at High <span class="hlt">Strain</span> <span class="hlt">Rate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hao, Y.; Hao, H.</p> <p>2013-03-01</p> <p>The dynamic compressive strength of rock materials increases with the <span class="hlt">strain</span> <span class="hlt">rate</span>. They are usually obtained by conducting laboratory tests such as split Hopkinson pressure bar (SHPB) test or drop-weight test. It is commonly agreed now that the dynamic increase factor (DIF) obtained from impact test is affected by lateral inertia confinement, friction confinement between the specimen and impact materials and the specimen sizes and geometries. Therefore, those derived directly from testing data do not necessarily reflect the true dynamic material properties. The influences of these parameters, however, are not straightforward to be quantified in laboratory tests. Therefore, the empirical DIF relations of rock materials obtained directly from impact tests consist of contributions from lateral inertia and end friction confinements, which need be eliminated to reflect the true dynamic material properties. Moreover, different rocks, such as granite, limestone and tuff have different material parameters, e.g., equation of state (EOS) and strength, which may also affect the DIF of materials but are not explicitly studied in the open literature. In the present study, numerical models of granite, limestone and tuff materials with different EOS and strength under impact loads are developed to simulate SHPB tests and to study the influences of EOS and strength, lateral inertia confinement and end friction confinement <span class="hlt">effects</span> on their respective DIFs in the <span class="hlt">strain</span> <span class="hlt">rate</span> range between 1 and 1,000 s-1. The commercial software AUTODYN with user-provided subroutines is used to perform the numerical simulations of SHPB tests. Numerical simulation results indicate that the lateral inertia confinement, friction confinement and specimen aspect ( L/ D) ratio significantly influence DIF obtained from impact tests and the inertia confinement <span class="hlt">effect</span> is different for different rocks. Based on the numerical results, quantifications on the relative contributions from the lateral inertia</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/175397','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/175397"><span id="translatedtitle">Experimental determination of the <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> dependence of the fraction of plastic work converted to heat</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hodowany, J.; Ravichandran, G.; Rosakis, A.J.</p> <p>1995-12-31</p> <p>When metals are deformed dynamically, there is insufficient time for heat generated by plastic deformation to be conducted to the surroundings. Thus, the conversion of plastic work into heat at high <span class="hlt">strain</span> <span class="hlt">rates</span> can result in significant temperature increases, which contribute to thermal softening, thereby altering a material`s constitutive response. The fraction of plastic work converted to heat represents the strength of the coupling term between temperature and mechanical fields in thermalmechanical problems involving plastic flow. The experimental determination of this constitutive function is important since it is an integral part of the formulation of coupled thermomechanical field equations. This fraction also plays an important role in failure mode characterization for metals deforming at high <span class="hlt">rates</span> of <span class="hlt">strain</span>, such as the formation of adiabatic shear bands. This investigation systematically examines the <span class="hlt">rate</span> of conversion of plastic work to heat in metals under dynamic loading. Temperature was measured in-situ using an array of high speed In-Sb infrared detectors. The plastic work <span class="hlt">rate</span> and the heat generation <span class="hlt">rate</span> were determined directly from experimental data. The ratio of heat generation <span class="hlt">rate</span> to plastic work <span class="hlt">rate</span>, i.e., the relative <span class="hlt">rate</span> at which plastic work is converted to heat, was calculated from this data. The functional dependence of this quantity upon <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> is reported for 1020 steel, 2024 aluminum, Ti-6Al-4V titanium alloy, and C300 maraging steel.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016E%26PSL.442...51K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26PSL.442...51K"><span id="translatedtitle">Background <span class="hlt">rates</span> of swarm earthquakes that are synchronized with volumetric <span class="hlt">strain</span> changes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kumazawa, Takao; Ogata, Yosihiko; Kimura, Kazuhiro; Maeda, Kenji; Kobayashi, Akio</p> <p>2016-05-01</p> <p>Off the east coast of the Izu Peninsula in Japan, there is a submarine volcanic region where earthquake swarms occur caused by magma intrusions. We investigated the background seismicity <span class="hlt">rates</span> of the swarm activity by removing the triggering <span class="hlt">effect</span> of aftershocks. We found that such background <span class="hlt">rate</span> changes coincide with the changes of exponentially weighted averages of volumetric <span class="hlt">strain</span> increments at the Higashi-Izu station. We further found that such a relationship consistently depends on the distance between the strainmeter station and the location of the swarm onset. The quantitative relationships revealed here may be used to monitor magma intrusions that drive the stress changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/215303','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/215303"><span id="translatedtitle">The role of reactant unmixedness, <span class="hlt">strain</span> <span class="hlt">rate</span>, and length scale on premixed combustor performance</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Samuelsen, S.; LaRue, J.; Vilayanur, S.; Guillaume, D.</p> <p>1995-12-31</p> <p>Lean premixed combustion provides a means to reduce pollutant formation and increase combustion efficiency. However, fuel-air mixing is rarely uniform in space and time. This nonuniformity in concentration will lead to relative increases in pollutant formation and decreases in combustion efficiency. The nonuniformity of the concentration at the exit of the premixer has been defined by Lyons (1981) as the ``unmixedness.`` Although turbulence properties such as length scales and <span class="hlt">strain</span> <span class="hlt">rate</span> are known to <span class="hlt">effect</span> unmixedness, the exact relationship is unknown. Evaluating this relationship and the <span class="hlt">effect</span> of unmixedness in premixed combustion on pollutant formation and combustion efficiency are an important part of the overall goal of US Department of Energy`s Advanced Turbine System (ATS) program and are among the goals of the program described herein. The information obtained from ATS is intended to help to develop and commercialize gas turbines. The contributions to the program which the University of California (Irvine) Combustion Lab (UCICL) will provide are: (1) establish the relationship of inlet unmixedness, length scales, and mean <span class="hlt">strain</span> <span class="hlt">rate</span> to performance, (2) determine the optimal levels of inlet unmixedness, length scales, and mean <span class="hlt">strain</span> <span class="hlt">rates</span> to maximize combustor performance, and (3) identify efficient premixing methods for achieving the necessary inlet conditions. The program during this reporting period is focused on developing a means to measure and qualify different degrees of temporal and spatial unmixedness. Laser diagnostic methods for planer unmixedness measurements are being developed and preliminary results are presented herein. These results will be used to (1), aid in the design of experimental premixers, and (2), determine the unmixedness which will be correlated with the emissions of the combustor. This measure of unmixedness coupled with length scale, <span class="hlt">strain</span> <span class="hlt">rate</span> and intensity information is required to attain the UCI goals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MRE.....4c5303A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MRE.....4c5303A"><span id="translatedtitle">Mechanical behaviour of glass fibre reinforced composite at varying <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Acharya, Saikat; Mondal, D. K.; Ghosh, K. S.; Mukhopadhyay, A. K.</p> <p>2017-03-01</p> <p>Here we report the results of compressive split Hopkinson pressure bar experiments (SHPB) conducted on unidirectional glass fibre reinforced polymer (GFRP) in the <span class="hlt">strain</span> <span class="hlt">rate</span> regime 5  ×  102–1.3  ×  103 s‑1. The maximum compressive strength of GFRP was found to increase by as much as 55% with increase in <span class="hlt">strain</span> <span class="hlt">rate</span>. However, the corresponding relative <span class="hlt">strain</span> to failure response was measured to increase only marginally with increase in <span class="hlt">strain</span> <span class="hlt">rates</span>. Based on the experimental results and photomicrographs obtained from FE-SEM based post mortem examinations, the failure phenomena are suggested to be associated with increase in absorption of energy from low to high <span class="hlt">strain</span> <span class="hlt">rates</span>. Attempts have been made to explain these observations in terms of changes in deformation mechanisms primarily as a function of <span class="hlt">strain</span> <span class="hlt">rates</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/956645','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/956645"><span id="translatedtitle">Compressive properties of a closed-cell aluminum foam as a function of <span class="hlt">strain-rate</span> and temperature</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cady, Carl M; Gray, Ill, George T; Liu, Cheng; Lovato, Manuel L; Mukai, T</p> <p>2008-01-01</p> <p>The compressive constitutive behavior of a closed-cell aluminum foam (ALPORAS) manufactured by Shinko Wire Co. in Japan was evaluated under static and dynamic loading conditions as a function of temperature. High-<span class="hlt">strain-rate</span> tests (1000-2000 s{sup -1}) were conducted using a split-Hopkinson pressure bar (SHPB). Quasi-static and intermediate-<span class="hlt">strain-rate</span> tests were conducted on a hydraulic load frame. A small but discernable change in the flow stress behavior as a function of <span class="hlt">strain</span> <span class="hlt">rate</span> was measured. The deformation behavior of the Al-foam was however found to be strongly temperature dependent under both quasi-static and dynamic loading. Localized deformation and stress state instability during testing of metal foams is discussed in detail since the mechanical behavior over the entire range of <span class="hlt">strain</span> <span class="hlt">rates</span> indicates non-uniform deformation. Additionally, investigation of the <span class="hlt">effect</span> of residual stresses created during manufacturing on the mechanical behavior was investigated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JMEP...21.1462B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JMEP...21.1462B"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">Rate</span> Dependency of Bronze Metal Matrix Composite Mechanical Properties as a Function of Casting Technique</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, Lloyd; Joyce, Peter; Radice, Joshua; Gregorian, Dro; Gobble, Michael</p> <p>2012-07-01</p> <p><span class="hlt">Strain</span> <span class="hlt">rate</span> dependency of mechanical properties of tungsten carbide (WC)-filled bronze castings fabricated by centrifugal and sedimentation-casting techniques are examined, in this study. Both casting techniques are an attempt to produce a functionally graded material with high wear resistance at a chosen surface. Potential applications of such materials include shaft bushings, electrical contact surfaces, and brake rotors. Knowledge of <span class="hlt">strain</span> <span class="hlt">rate</span>-dependent mechanical properties is recommended for predicting component response due to dynamic loading or impact events. A brief overview of the casting techniques for the materials considered in this study is followed by an explanation of the test matrix and testing techniques. Hardness testing, density measurement, and determination of the volume fraction of WC particles are performed throughout the castings using both image analysis and optical microscopy. The <span class="hlt">effects</span> of particle filling on mechanical properties are first evaluated through a microhardness survey of the castings. The volume fraction of WC particles is validated using a thorough density survey and a rule-of-mixtures model. Split Hopkinson Pressure Bar (SHPB) testing of various volume fraction specimens is conducted to determine <span class="hlt">strain</span> dependence of mechanical properties and to compare the process-property relationships between the two casting techniques. The baseline performances of C95400 bronze are provided for comparison. The results show that the addition of WC particles improves microhardness significantly for the centrifugally cast specimens, and, to a lesser extent, in the sedimentation-cast specimens, largely because the WC particles are more concentrated as a result of the centrifugal-casting process. Both metal matrix composites (MMCs) demonstrate <span class="hlt">strain</span> <span class="hlt">rate</span> dependency, with sedimentation casting having a greater, but variable, <span class="hlt">effects</span> on material response. This difference is attributed to legacy <span class="hlt">effects</span> from the casting process, namely</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20505994','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20505994"><span id="translatedtitle">The influence of <span class="hlt">strain</span> <span class="hlt">rate</span> dependency on the structure-property relations of porcine brain.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Begonia, Mark T; Prabhu, Raj; Liao, Jun; Horstemeyer, Mark F; Williams, Lakiesha N</p> <p>2010-10-01</p> <p>This study examines the internal microstructure evolution of porcine brain during mechanical deformation. <span class="hlt">Strain</span> <span class="hlt">rate</span> dependency of porcine brain was investigated under quasi-static compression for <span class="hlt">strain</span> <span class="hlt">rates</span> of 0.00625, 0.025, and 0.10 s(-1). Confocal microscopy was employed at 15, 30, and 40% <span class="hlt">strain</span> to quantify microstructural changes, and image analysis was implemented to calculate the area fraction of neurons and glial cells. The nonlinear stress-<span class="hlt">strain</span> behavior exhibited a viscoelastic response from the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity observed, and image analysis revealed that the mean area fraction of neurons and glial cells increased according to the applied <span class="hlt">strain</span> level and <span class="hlt">strain</span> <span class="hlt">rate</span>. The area fraction for the undamaged state was 7.85 ± 0.07%, but at 40% <span class="hlt">strain</span> the values were 11.55 ± 0.35%, 13.30 ± 0.28%, and 19.50 ± 0.14% for respective <span class="hlt">strain</span> <span class="hlt">rates</span> of 0.00625, 0.025, and 0.10 s(-1). The increased area fractions were a function of the applied <span class="hlt">strain</span> <span class="hlt">rate</span> and were attributed to the compaction of neural constituents and the stiffening tissue response. The microstructural variations in the tissue were linked to mechanical properties at progressive levels of compression in order to generate structure-property relationships useful for refining current FE material models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3246303','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3246303"><span id="translatedtitle">Dynamic Mechanical Response of Biomedical 316L Stainless Steel as Function of <span class="hlt">Strain</span> <span class="hlt">Rate</span> and Temperature</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Lee, Woei-Shyan; Chen, Tao-Hsing; Lin, Chi-Feng; Luo, Wen-Zhen</p> <p>2011-01-01</p> <p>A split Hopkinson pressure bar is used to investigate the dynamic mechanical properties of biomedical 316L stainless steel under <span class="hlt">strain</span> <span class="hlt">rates</span> ranging from 1 × 103 s−1 to 5 × 103 s−1 and temperatures between 25°C and 800°C. The results indicate that the flow stress, work-hardening <span class="hlt">rate</span>, <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity, and thermal activation energy are all significantly dependent on the <span class="hlt">strain</span>, <span class="hlt">strain</span> <span class="hlt">rate</span>, and temperature. For a constant temperature, the flow stress, work-hardening <span class="hlt">rate</span>, and <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity increase with increasing <span class="hlt">strain</span> <span class="hlt">rate</span>, while the thermal activation energy decreases. Catastrophic failure occurs only for the specimens deformed at a <span class="hlt">strain</span> <span class="hlt">rate</span> of 5 × 103 s−1 and temperatures of 25°C or 200°C. Scanning electron microscopy observations show that the specimens fracture in a ductile shear mode. Optical microscopy analyses reveal that the number of slip bands within the grains increases with an increasing <span class="hlt">strain</span> <span class="hlt">rate</span>. Moreover, a dynamic recrystallisation of the deformed microstructure is observed in the specimens tested at the highest temperature of 800°C. PMID:22216015</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22216015','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22216015"><span id="translatedtitle">Dynamic Mechanical Response of Biomedical 316L Stainless Steel as Function of <span class="hlt">Strain</span> <span class="hlt">Rate</span> and Temperature.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lee, Woei-Shyan; Chen, Tao-Hsing; Lin, Chi-Feng; Luo, Wen-Zhen</p> <p>2011-01-01</p> <p>A split Hopkinson pressure bar is used to investigate the dynamic mechanical properties of biomedical 316L stainless steel under <span class="hlt">strain</span> <span class="hlt">rates</span> ranging from 1 × 10(3) s(-1) to 5 × 10(3) s(-1) and temperatures between 25°C and 800°C. The results indicate that the flow stress, work-hardening <span class="hlt">rate</span>, <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity, and thermal activation energy are all significantly dependent on the <span class="hlt">strain</span>, <span class="hlt">strain</span> <span class="hlt">rate</span>, and temperature. For a constant temperature, the flow stress, work-hardening <span class="hlt">rate</span>, and <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity increase with increasing <span class="hlt">strain</span> <span class="hlt">rate</span>, while the thermal activation energy decreases. Catastrophic failure occurs only for the specimens deformed at a <span class="hlt">strain</span> <span class="hlt">rate</span> of 5 × 10(3) s(-1) and temperatures of 25°C or 200°C. Scanning electron microscopy observations show that the specimens fracture in a ductile shear mode. Optical microscopy analyses reveal that the number of slip bands within the grains increases with an increasing <span class="hlt">strain</span> <span class="hlt">rate</span>. Moreover, a dynamic recrystallisation of the deformed microstructure is observed in the specimens tested at the highest temperature of 800°C.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/616455','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/616455"><span id="translatedtitle">High <span class="hlt">strain</span> <span class="hlt">rate</span> superplasticity in a continuously recrystallized Al-6%Mg-0.3%Sc alloy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nieh, T.G.; Hsiung, L.M.; Wadsworth, J.; Kaibyshev, R.</p> <p>1998-05-01</p> <p>The superplastic properties of a cold-rolled Al-6Mg-0.3Sc alloy were studied at temperatures between 450 and 560 C and <span class="hlt">strain</span> <span class="hlt">rates</span> between 10{sup {minus}4} and 10{sup 0} s{sup {minus}1}. The alloy was observed to exhibit superplasticity over wide temperature (475--520 C) and <span class="hlt">strain</span> <span class="hlt">rate</span> ranges ({approximately} 10{sup {minus}3}--10{sup {minus}1} s{sup {minus}1}). It was found that the addition of Sc to Al-Mg alloys resulted in a uniform distribution of fine coherent Al{sub 3}Sc precipitates which <span class="hlt">effectively</span> pinned subgrain and grain boundaries during static and dynamic recrystallization. In this paper, the microstructural evolution during superplastic deformation was systematically examined using both optical and transmission electron microscopy. Based upon this microstructural examination, a mechanism is proposed to explain the observed high <span class="hlt">strain</span> <span class="hlt">rate</span> superplasticity in the alloy. A model is also proposed that describes grain boundary sliding accommodated by dislocations gliding across grains containing coherent precipitates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020052425','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020052425"><span id="translatedtitle">Tensile Strength of Carbon Nanotubes Under Realistic Temperature and <span class="hlt">Strain</span> <span class="hlt">Rate</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wei, Chen-Yu; Cho, Kyeong-Jae; Srivastava, Deepak; Biegel, Bryan (Technical Monitor)</p> <p>2002-01-01</p> <p><span class="hlt">Strain</span> <span class="hlt">rate</span> and temperature dependence of the tensile strength of single-wall carbon nanotubes has been investigated with molecular dynamics simulations. The tensile failure or yield <span class="hlt">strain</span> is found to be strongly dependent on the temperature and <span class="hlt">strain</span> <span class="hlt">rate</span>. A transition state theory based predictive model is developed for the tensile failure of nanotubes. Based on the parameters fitted from high-<span class="hlt">strain</span> <span class="hlt">rate</span> and temperature dependent molecular dynamics simulations, the model predicts that a defect free micrometer long single-wall nanotube at 300 K, stretched with a <span class="hlt">strain</span> <span class="hlt">rate</span> of 1%/hour, fails at about 9 plus or minus 1% tensile <span class="hlt">strain</span>. This is in good agreement with recent experimental findings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23937993','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23937993"><span id="translatedtitle">Longitudinal <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> by two-dimensional speckle tracking in non-sedated healthy cats.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Silva, A C; Muzzi, R A L; Oberlender, G; Nogueira, R B; Muzzi, L A L; Reis, G F M; Mantovani, M M</p> <p>2013-12-01</p> <p>Two dimensional speckle tracking (2D-ST) is a relatively new tool that has been used in veterinary medicine to quantify myocardial function. However, there is little information about the use of this tool in healthy cats. Thus, the aim of this study was to evaluate left ventricular longitudinal <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> in non-sedated healthy cats, as well as longitudinal velocity and displacement, by means of 2D-ST echocardiography. Thirty non-sedated healthy cats were examined and 2D images were obtained for 2D-ST analyzes. The global mean <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> was -15.65 ± 5.46% and -1.80 ± 0.59 s(-1), respectively. Velocity and displacement were 1.41 ± 0.87 cm/s and 1.27 ± 0.80 mm, respectively. Thus, 2D-ST demonstrated to be feasible for measuring left ventricular longitudinal <span class="hlt">strain</span>, <span class="hlt">strain</span> <span class="hlt">rate</span>, velocity and displacement in cats and preliminary reference values for non-sedated healthy cats can be established from the results of this study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/902598','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/902598"><span id="translatedtitle">The <span class="hlt">strain-rate</span> sensitivity of high-strength high-toughness steels.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dilmore, M.F.; Crenshaw, Thomas B.; Boyce, Brad Lee</p> <p>2006-01-01</p> <p>The present study examines the <span class="hlt">strain-rate</span> sensitivity of four high strength, high-toughness alloys at <span class="hlt">strain</span> <span class="hlt">rates</span> ranging from 0.0002 s-1 to 200 s-1: Aermet 100, a modified 4340, modified HP9-4-20, and a recently developed Eglin AFB steel alloy, ES-1c. A refined dynamic servohydraulic method was used to perform tensile tests over this entire range. Each of these alloys exhibit only modest <span class="hlt">strain-rate</span> sensitivity. Specifically, the <span class="hlt">strain-rate</span> sensitivity exponent m, is found to be in the range of 0.004-0.007 depending on the alloy. This corresponds to a {approx}10% increase in the yield strength over the 7-orders of magnitude change in <span class="hlt">strain-rate</span>. Interestingly, while three of the alloys showed a concominant {approx}3-10% drop in their ductility with increasing <span class="hlt">strain-rate</span>, the ES1-c alloy actually exhibited a 25% increase in ductility with increasing <span class="hlt">strain-rate</span>. Fractography suggests the possibility that at higher <span class="hlt">strain-rates</span> ES-1c evolves towards a more ductile dimple fracture mode associated with microvoid coalescence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016LPICo1921.6276Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016LPICo1921.6276Z"><span id="translatedtitle">High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Response Testing with the Split Hopkinson Pressure Bar Technique</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zwiessler, R.; Kenkmann, T.; Poelchau, M. H.; Nau, S.; Hess, S.</p> <p>2016-08-01</p> <p>We present a newly developed split Hopkinson pressure bar which is used to quantify the <span class="hlt">rate</span> dependent uniaxial stress-<span class="hlt">strain</span> response of rocks in the high <span class="hlt">strain</span> <span class="hlt">rate</span> regime as well as results of our first study on a sandstone and Carrara marble.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1243352-experimental-study-vorticity-strain-rate-interaction-turbulent-partially-premixed-jet-flames-using-tomographic-particle-image-velocimetry','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1243352-experimental-study-vorticity-strain-rate-interaction-turbulent-partially-premixed-jet-flames-using-tomographic-particle-image-velocimetry"><span id="translatedtitle">Experimental study of vorticity-<span class="hlt">strain</span> <span class="hlt">rate</span> interaction in turbulent partially-premixed jet flames using tomographic particle image velocimetry</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Coriton, Bruno; Frank, Jonathan H.</p> <p>2016-02-16</p> <p>In turbulent flows, the interaction between vorticity, ω, and <span class="hlt">strain</span> <span class="hlt">rate</span>, s, is considered a primary mechanism for the transfer of energy from large to small scales through vortex stretching. The ω-s coupling in turbulent jet flames is investigated using tomographic particle image velocimetry (TPIV). TPIV provides a direct measurement of the three-dimensional velocity field from which ω and s are determined. The <span class="hlt">effects</span> of combustion and mean shear on the ω-s interaction are investigated in turbulent partially premixed methane/air jet flames with high and low probabilities of localized extinction as well as in a non-reacting isothermal air jet withmore » Reynolds number of approximately 13,000. Results show that combustion causes structures of high vorticity and <span class="hlt">strain</span> <span class="hlt">rate</span> to agglomerate in highly correlated, elongated layers that span the height of the probe volume. In the non-reacting jet, these structures have a more varied morphology, greater fragmentation, and are not as well correlated. The enhanced spatiotemporal correlation of vorticity and <span class="hlt">strain</span> <span class="hlt">rate</span> in the stable flame results in stronger ω-s interaction characterized by increased enstrophy and <span class="hlt">strain-rate</span> production <span class="hlt">rates</span> via vortex stretching and <span class="hlt">straining</span>, respectively. The probability of preferential local alignment between ω and the eigenvector of the intermediate principal <span class="hlt">strain</span> <span class="hlt">rate</span>, s2, which is intrinsic to the ω-s coupling in turbulent flows, is larger in the flames and increases with the flame stability. The larger mean shear in the flame imposes a preferential orientation of ω and s2 tangential to the shear layer. The extensive and compressive principal <span class="hlt">strain</span> <span class="hlt">rates</span>, s1 and s3, respectively, are preferentially oriented at approximately 45° with respect to the jet axis. As a result, the production <span class="hlt">rates</span> of <span class="hlt">strain</span> and vorticity tend to be dominated by instances in which ω is parallel to the s1¯-s2¯ plane and orthogonal to s3¯.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1323605','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1323605"><span id="translatedtitle">Dynamic High-Temperature Characterization of an Iridium Alloy in Compression at High <span class="hlt">Strain</span> <span class="hlt">Rates</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Song, Bo; Nelson, Kevin; Lipinski, Ronald J.; Bignell, John L.; Ulrich, G. B.; George, E. P.</p> <p>2014-06-01</p> <p>Iridium alloys have superior strength and ductility at elevated temperatures, making them useful as structural materials for certain high-temperature applications. However, experimental data on their high-temperature high-<span class="hlt">strain-rate</span> performance are needed for understanding high-speed impacts in severe elevated-temperature environments. Kolsky bars (also called split Hopkinson bars) have been extensively employed for high-<span class="hlt">strain-rate</span> characterization of materials at room temperature, but it has been challenging to adapt them for the measurement of dynamic properties at high temperatures. Current high-temperature Kolsky compression bar techniques are not capable of obtaining satisfactory high-temperature high-<span class="hlt">strain-rate</span> stress-<span class="hlt">strain</span> response of thin iridium specimens investigated in this study. We analyzed the difficulties encountered in high-temperature Kolsky compression bar testing of thin iridium alloy specimens. Appropriate modifications were made to the current high-temperature Kolsky compression bar technique to obtain reliable compressive stress-<span class="hlt">strain</span> response of an iridium alloy at high <span class="hlt">strain</span> <span class="hlt">rates</span> (300 – 10000 s<sup>-1</sup>) and temperatures (750°C and 1030°C). Uncertainties in such high-temperature high-<span class="hlt">strain-rate</span> experiments on thin iridium specimens were also analyzed. The compressive stress-<span class="hlt">strain</span> response of the iridium alloy showed significant sensitivity to <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050192390','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050192390"><span id="translatedtitle">Nonlinearity and <span class="hlt">Strain-Rate</span> Dependence in the Deformation Response of Polymer Matrix Composites Modeled</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldberg, Robert K.</p> <p>2000-01-01</p> <p>There has been no accurate procedure for modeling the high-speed impact of composite materials, but such an analytical capability will be required in designing reliable lightweight engine-containment systems. The majority of the models in use assume a linear elastic material response that does not vary with <span class="hlt">strain</span> <span class="hlt">rate</span>. However, for containment systems, polymer matrix composites incorporating ductile polymers are likely to be used. For such a material, the deformation response is likely to be nonlinear and to vary with <span class="hlt">strain</span> <span class="hlt">rate</span>. An analytical model has been developed at the NASA Glenn Research Center at Lewis Field that incorporates both of these features. A set of constitutive equations that was originally developed to analyze the viscoplastic deformation of metals (Ramaswamy-Stouffer equations) was modified to simulate the nonlinear, <span class="hlt">rate</span>-dependent deformation of polymers. Specifically, the <span class="hlt">effects</span> of hydrostatic stresses on the inelastic response, which can be significant in polymers, were accounted for by a modification of the definition of the <span class="hlt">effective</span> stress. The constitutive equations were then incorporated into a composite micromechanics model based on the mechanics of materials theory. This theory predicts the deformation response of a composite material from the properties and behavior of the individual constituents. In this manner, the nonlinear, <span class="hlt">rate</span>-dependent deformation response of a polymer matrix composite can be predicted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70028377','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70028377"><span id="translatedtitle">Mechanical deformation model of the western United States instantaneous <span class="hlt">strain-rate</span> field</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Pollitz, F.F.; Vergnolle, M.</p> <p>2006-01-01</p> <p> system is systematically underpredicted by models which account only for relaxation from known large earthquakes. This strongly suggests that in addition to viscoelastic-cycle <span class="hlt">effects</span>, steady deep slip in the lower lithosphere is needed to explain the observed <span class="hlt">strain-rate</span> field. ?? 2006 The Authors Journal compilation ?? 2006 RAS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EP%26S...68..207M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EP%26S...68..207M"><span id="translatedtitle">Inelastic <span class="hlt">strain</span> <span class="hlt">rate</span> in the seismogenic layer of Kyushu Island, Japan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matsumoto, Satoshi; Nishimura, Takuya; Ohkura, Takahiro</p> <p>2016-12-01</p> <p>Seismic activity is associated with crustal stress relaxation, creating inelastic <span class="hlt">strain</span> in a medium due to faulting. Inelastic <span class="hlt">strain</span> affects the stress field around a weak body and causes stress concentration around the body, because the body itself has already released stress. Therefore, the understanding of inelastic deformation is important as it generates earthquakes. We investigated average inelastic <span class="hlt">strain</span> in a spatial bin of Kyushu Island, Japan, and obtained the inelastic <span class="hlt">strain</span> <span class="hlt">rate</span> distribution associated with crustal earthquakes, based on the analysis of fault plane solutions and seismic moments. Large inelastic <span class="hlt">strains</span> (>10-7 year-1) were found in the Beppu-Shimabara area, located in the center of Kyushu Island. The <span class="hlt">strain</span> <span class="hlt">rate</span> tensor was similar to that of the stress tensor except the absolute value in the area, implying that the inelastic <span class="hlt">strain</span> was controlled by the stress field. The 2016 Kumamoto earthquake sequence (maximum magnitude 7.3) occurred in the Beppu-Shimabara area, with the major earthquakes located around the high inelastic <span class="hlt">strain</span> <span class="hlt">rate</span> area. Inelastic <span class="hlt">strain</span> in the volume released the stress. In addition, the inelastic <span class="hlt">strain</span> created an increment of stress around the volume. This indicates that the spatial heterogeneity of inelastic <span class="hlt">strain</span> might concentrate stress.[Figure not available: see fulltext.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19920011652','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920011652"><span id="translatedtitle">High <span class="hlt">strain</span> <span class="hlt">rate</span> properties of off-axis composite laminates, part 2</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Daniel, I. M.</p> <p>1991-01-01</p> <p>Unidirectional off-axis graphite/epoxy and graphite/S-glass/epoxy laminates were characterized in uniaxial tension at <span class="hlt">strain</span> <span class="hlt">rates</span> ranging from quasi-static to over 500 s(sup -1). Laminate ring specimens were loaded by internal pressure with the tensile stress at 22.5, 30, and 45 degrees relative to the fiber direction. Results were presented in the form of stress-<span class="hlt">strain</span> curves to failure. Properties determined included moduli, Poisson's ratios, strength, and ultimate <span class="hlt">strain</span>. In all three laminates of both materials the modulus and strength increase sharply with <span class="hlt">strain</span> <span class="hlt">rate</span>, reaching values roughly 100, 150, and 200 percent higher than corresponding static values for the 22.5(sub 8), 30(sub 8), and 45(sub 8) degree laminates, respectively. In the case of ultimate <span class="hlt">strain</span> no definite trends could be established, but the maximum deviation from the average of any value for any <span class="hlt">strain</span> <span class="hlt">rate</span> was less than 18 percent.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27757525','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27757525"><span id="translatedtitle">Characteristic systolic waveform of left ventricular longitudinal <span class="hlt">strain</span> <span class="hlt">rate</span> in patients with hypertrophic cardiomyopathy.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Okada, Kazunori; Kaga, Sanae; Mikami, Taisei; Masauzi, Nobuo; Abe, Ayumu; Nakabachi, Masahiro; Yokoyama, Shinobu; Nishino, Hisao; Ichikawa, Ayako; Nishida, Mutsumi; Murai, Daisuke; Hayashi, Taichi; Shimizu, Chikara; Iwano, Hiroyuki; Yamada, Satoshi; Tsutsui, Hiroyuki</p> <p>2016-10-18</p> <p>We analyzed the waveform of systolic <span class="hlt">strain</span> and <span class="hlt">strain-rate</span> curves to find a characteristic left ventricular (LV) myocardial contraction pattern in patients with hypertrophic cardiomyopathy (HCM), and evaluated the utility of these parameters for the differentiation of HCM and LV hypertrophy secondary to hypertension (HT). From global <span class="hlt">strain</span> and <span class="hlt">strain-rate</span> curves in the longitudinal and circumferential directions, the time from mitral valve closure to the peak <span class="hlt">strains</span> (T-LS and T-CS, respectively) and the peak systolic <span class="hlt">strain</span> <span class="hlt">rates</span> (T-LSSR and T-CSSR, respectively) were measured in 34 patients with HCM, 30 patients with HT, and 25 control subjects. The systolic <span class="hlt">strain-rate</span> waveform was classified into 3 patterns ("V", "W", and "√" pattern). In the HCM group, T-LS was prolonged, but T-LSSR was shortened; consequently, T-LSSR/T-LS ratio was distinctly lower than in the HT and control groups. The "√" pattern of longitudinal <span class="hlt">strain-rate</span> waveform was more frequently seen in the HCM group (74 %) than in the control (4 %) and HT (20 %) groups. Similar but less distinct results were obtained in the circumferential direction. To differentiate HCM from HT, the sensitivity and specificity of the T-LSSR/T-LS ratio <0.34 and the "√"-shaped longitudinal <span class="hlt">strain-rate</span> waveform were 85 and 63 %, and 74 and 80 %, respectively. In conclusion, in patients with HCM, a reduced T-LSSR/T-LS ratio and a characteristic "√"-shaped waveform of LV systolic <span class="hlt">strain</span> <span class="hlt">rate</span> was seen, especially in the longitudinal direction. The timing and waveform analyses of systolic <span class="hlt">strain</span> <span class="hlt">rate</span> may be useful to distinguish between HCM and HT.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..MAR.P1148A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..MAR.P1148A"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">Rate</span> Dependence of Compressive Yield and Relaxation in DGEBA Epoxies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arechederra, Gabriel K.; Reprogle, Riley C.; Clarkson, Caitlyn M.; McCoy, John D.; Kropka, Jamie M.; Long, Kevin N.; Chambers, Robert S.</p> <p>2015-03-01</p> <p>The mechanical response in uniaxial compression of two diglycidyl ether of bisphenol-A epoxies were studied. These were 828DEA (Epon 828 cured with diethanolamine (DEA)) and 828T403 (Epon 828 cured with Jeffamine T-403). Two types of uniaxial compression tests were performed: A) constant <span class="hlt">strain</span> <span class="hlt">rate</span> compression and B) constant <span class="hlt">strain</span> <span class="hlt">rate</span> compression followed by a constant <span class="hlt">strain</span> relaxation. The peak (yield) stress was analyzed as a function of <span class="hlt">strain</span> <span class="hlt">rate</span> from Eyring theory for activation volume. Runs at different temperatures permitted the construction of a mastercurve, and the resulting shift factors resulted in an activation energy. <span class="hlt">Strain</span> and hold tests were performed for a low <span class="hlt">strain</span> <span class="hlt">rate</span> where a peak stress was lacking and for a higher <span class="hlt">strain</span> <span class="hlt">rate</span> where the peak stress was apparent. Relaxation from <span class="hlt">strains</span> at different places along the stress-<span class="hlt">strain</span> curve was tracked and compared. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGeo...81...91N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGeo...81...91N"><span id="translatedtitle">Refined models of gravitational potential energy compared with stress and <span class="hlt">strain</span> <span class="hlt">rate</span> patterns in Iberia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Neves, Maria C.; Fernandes, Rui M.; Adam, Claudia</p> <p>2014-11-01</p> <p>This study examines the role of gravitational potential energy (GPE) in generating second-order (spatial scale ∼102 km) variations in the Iberia stress and <span class="hlt">strain-rate</span> patterns. We present a new map of present-day <span class="hlt">strain</span> <span class="hlt">rate</span> field derived from the secular velocity field computed using all available continuously operating Global Navigation Satellite Systems (GNSS) stations in Iberia. The estimated <span class="hlt">strain</span> <span class="hlt">rate</span> field is generally consistent with the tectonic framework of the Iberian region, even though sporadic sharp local variations downgrade its correlation with the regional stress patterns. Many of the sharp spatial variations in the <span class="hlt">strain</span> <span class="hlt">rate</span> map are consistent with local changes of deformation style determined by prevailing faults. To obtain a more accurate estimate of GPE we use new data on the structure of the crust and apply a thin sheet approach using a 3-D definition of deviatoric stress. The GPE is derived from two isostatically compensated models (GPEd and GPEe compensated by density and elevation adjustment, respectively) and from the truncated geoid (GPEg). The GPE stresses are then summed with the first-order stress field due to the Eurasia-Nubia (EU-NU) convergence and the results compared with both the stress and <span class="hlt">strain</span> <span class="hlt">rate</span> data. In agreement with previous studies, we find that the GPE does not significantly change the NW-SE average direction of the most compressive stress (SHmax) imposed by the EU-NU collision, its main <span class="hlt">effect</span> being to cause spatially changing stress regimes. From the analysis of the different GPE models we find: (1) in the Pyrenees, the tectonic forces have a secondary role when compared to the GPE. In this region, the model that best correlates with observations is the one emphasizing the role of surface elevation as a source of GPE (GPEe); (2) in the Iberian Chain and the Betics, the GPE imposes NE-SW extension consistent with a strike-slip regime and is equally (GPEe) or more (GPEg) important than the tectonic forces. In</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1793k0017K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1793k0017K"><span id="translatedtitle">Comparison of epoxy-based encapsulating materials over temperature and <span class="hlt">strain</span> <span class="hlt">rate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khan, Amnah S.; Wilgeroth, James; Balzer, Jens; Proud, William G.</p> <p>2017-01-01</p> <p>The highly insulating, adhesive and bonding properties of thermosetting epoxies, their ability to be injection moulded in an uncured state, as well as their presence in a wide number of composites, has resulted in their widespread use in both electrical and aerospace applications. There is thus a need to understand the compressive response of epoxies over the range of temperatures likely to be experienced within their working environment. The <span class="hlt">effects</span> of varying <span class="hlt">strain</span> <span class="hlt">rates</span> and temperatures on an epoxy resin (Scotchcast 8) and an epoxy-based syntactic foam (Stycast 1090) were investigated. The samples were studied from -20 °C to +80 °C over a range of <span class="hlt">strain</span> <span class="hlt">rates</span> (10-4 - 10+3 s-1). Stress-<span class="hlt">strain</span> data was obtained, with further analysis from high-speed images. Dynamic Mechanical Analysis (DMA) was also performed on the two materials. Data obtained from these experiments demonstrated key differences in the behaviour of the two materials, forming a basis for comparison with numerical simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJWC..9401034M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9401034M"><span id="translatedtitle">Tensile behaviour of geopolymer-based materials under medium and high <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Menna, Costantino; Asprone, Domenico; Forni, Daniele; Roviello, Giuseppina; Ricciotti, Laura; Ferone, Claudio; Bozza, Anna; Prota, Andrea; Cadoni, Ezio</p> <p>2015-09-01</p> <p>Geopolymers are a promising class of inorganic materials typically obtained from an alluminosilicate source and an alkaline solution, and characterized by an amorphous 3-D framework structure. These materials are particularly attractive for the construction industry due to mechanical and environmental advantages they exhibit compared to conventional systems. Indeed, geopolymer-based concretes represent a challenge for the large scale uses of such a binder material and many research studies currently focus on this topic. However, the behaviour of geopolymers under high dynamic loads is rarely investigated, even though it is of a fundamental concern for the integrity/vulnerability assessment under extreme dynamic events. The present study aims to investigate the <span class="hlt">effect</span> of high dynamic loading conditions on the tensile behaviour of different geopolymer formulations. The dynamic tests were performed under different <span class="hlt">strain</span> <span class="hlt">rates</span> by using a Hydro-pneumatic machine and a modified Hopkinson bar at the DynaMat laboratory of the University of Applied Sciences of Southern Switzerland. The results are processed in terms of stress-<span class="hlt">strain</span> relationships and strength dynamic increase factor at different <span class="hlt">strain-rate</span> levels. The dynamic increase factor was also compared with CEB recommendations. The experimental outcomes can be used to assess the constitutive laws of geopolymers under dynamic load conditions and implemented into analytical models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010SPIE.7522E..6BT','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010SPIE.7522E..6BT"><span id="translatedtitle">Constitutive equation for hardened SKD11 steel at high temperature and high <span class="hlt">strain</span> <span class="hlt">rate</span> using the SHPB technique</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tang, D. W.; Wang, C. Y.; Hu, Y. N.; Song, Y. X.</p> <p>2010-03-01</p> <p>In this present work, dynamic tests have been performed on hardened SKD11 steel (62 Rockwell C hardness) specimens by means of a high temperature split Hopkinson pressure bar (SHPB) test system. <span class="hlt">Effects</span> of temperature as well as those of <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> for the hardened steel are taken into account by using two ellipsoidal radiant heating reflectors with two halogen lamps and magnetic valve. The result obtained at high stain <span class="hlt">rates</span> were compared with those at low <span class="hlt">strain</span> <span class="hlt">rates</span> under the different temperature. It was seen that the flow stress curves are found to include a work hardening region and a work softening region and the mechanical behavior of the hardened steel is highly sensitive to both the <span class="hlt">strain</span> <span class="hlt">rate</span> and the temperature. To determine the true flow stress- true <span class="hlt">strain</span>, temperature relationship, specimens are tested from room temperature to 1073K at a <span class="hlt">strain</span> <span class="hlt">rate</span> form 0.01 s-1 to 104 s-1: The parameters for a Johnson-Cook constitutive equation and a modified Johnson-Cook constitutive equation are determined from the test results by fitting the data from both quasi-static compression and high temperature-dynamic compression tests. The modified Johnson-Cook constitutive equation is more suitable for expressing the dynamic behavior of the hardened SKD11 steel above the vicinity of the recrystallization temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009SPIE.7522E..6BT','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009SPIE.7522E..6BT"><span id="translatedtitle">Constitutive equation for hardened SKD11 steel at high temperature and high <span class="hlt">strain</span> <span class="hlt">rate</span> using the SHPB technique</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tang, D. W.; Wang, C. Y.; Hu, Y. N.; Song, Y. X.</p> <p>2009-12-01</p> <p>In this present work, dynamic tests have been performed on hardened SKD11 steel (62 Rockwell C hardness) specimens by means of a high temperature split Hopkinson pressure bar (SHPB) test system. <span class="hlt">Effects</span> of temperature as well as those of <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> for the hardened steel are taken into account by using two ellipsoidal radiant heating reflectors with two halogen lamps and magnetic valve. The result obtained at high stain <span class="hlt">rates</span> were compared with those at low <span class="hlt">strain</span> <span class="hlt">rates</span> under the different temperature. It was seen that the flow stress curves are found to include a work hardening region and a work softening region and the mechanical behavior of the hardened steel is highly sensitive to both the <span class="hlt">strain</span> <span class="hlt">rate</span> and the temperature. To determine the true flow stress- true <span class="hlt">strain</span>, temperature relationship, specimens are tested from room temperature to 1073K at a <span class="hlt">strain</span> <span class="hlt">rate</span> form 0.01 s-1 to 104 s-1: The parameters for a Johnson-Cook constitutive equation and a modified Johnson-Cook constitutive equation are determined from the test results by fitting the data from both quasi-static compression and high temperature-dynamic compression tests. The modified Johnson-Cook constitutive equation is more suitable for expressing the dynamic behavior of the hardened SKD11 steel above the vicinity of the recrystallization temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJWC..9401068L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9401068L"><span id="translatedtitle">Investigating strength of materials at very high <span class="hlt">strain</span> <span class="hlt">rates</span> using magnetically driven expanding cylinders</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lovinger, Zev; Nemirovsky, Ron; Avriel, Eyal; Dorogoy, Avraham; Ashuach, Yehezkel; Rittel, Daniel</p> <p>2015-09-01</p> <p>Dynamic characterization of strength properties is done, in common practice by the means of a Split-Hopkinson Pressure Bar (also named Kolsky-Bar) apparatus. In such systems, <span class="hlt">strain</span> <span class="hlt">rates</span> are limited up to ˜ 5 ṡ 103 sec-1. For higher <span class="hlt">strain</span> <span class="hlt">rates</span>, the <span class="hlt">strain</span> <span class="hlt">rate</span> hardening is assumed to be the same as that measured at lower <span class="hlt">rates</span>, with no direct measurement to validate the assumptions used for this extrapolation. In this work we are using a pulsed current generator (PCG) to create electro-magnetic (EM) driving forces on expanding cylinders. Most standard techniques for creating EM driving forces on cylinders or rings, as reported in the literature, reach <span class="hlt">strain</span> <span class="hlt">rates</span> of 1e3-1e4. Using our PCG, characterized by a fast rise time, we reach <span class="hlt">strain</span> <span class="hlt">rates</span> of ˜1e5, thus paving the way to a standard technique to measure strength at very high <span class="hlt">strain</span> <span class="hlt">rates</span>. To establish the experimental technique, we conducted a numerical study of the expanding cylinder set up using 2D hydrodynamic simulations to reach the desired high <span class="hlt">strain</span> <span class="hlt">rates</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.5457M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.5457M"><span id="translatedtitle">Role of inherited structures on the strength and <span class="hlt">strain</span> <span class="hlt">rate</span> of continental lithosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mazzotti, Stephane; Gueydan, Frédéric</p> <p>2014-05-01</p> <p>Under the Wilson Cycle and Plate Tectonics paradigms, continents are divided between stable continental regions (SCR), which tend to remain un-deformed, and plate boundary zones (PBZ) that repeatedly accommodate deformation associated with opening and closing of tectonic plates. This long-term (> 1 Ma) perspective is reflected in short-term (< 100 a) deformation markers such as seismicity and GPS measurements, which highlight the first-order contrast in <span class="hlt">strain</span> <span class="hlt">rates</span> between SCR and PBZ. Despite this clear first-order view, significant debate remains regarding short- and long-term strength and deformation <span class="hlt">rates</span> in intraplate weak zones (e.g., Rhine Graben, New Madrid seismic zone). We propose to constrain first-order strength and <span class="hlt">strain</span> <span class="hlt">rates</span> using lithosphere rheological models, including new <span class="hlt">strain</span>-weakening rheologies, driven by tectonic forces. We estimate average <span class="hlt">strain</span> <span class="hlt">rates</span> that satisfy near-failure equilibrium between net driving forces and lithosphere strength for cases that typify PBZ, cratons, and intraplate weak zones. Our model yields a range of <span class="hlt">strain</span> <span class="hlt">rates</span> that vary by up to six orders of magnitude between PBZ and cratons. In intraplate weak zones, structural and tectonic heritage results in significant weakening and yields <span class="hlt">strain</span> <span class="hlt">rates</span> compatible with GPS, seismicity, and geological markers. These results provide first-order constraints on long-term lithosphere strength and deformation <span class="hlt">rates</span>. In particular, we explore upper and lower bounds of possible <span class="hlt">strain</span> <span class="hlt">rates</span> in intraplate weak zones, using a range of geotherm, rheology, and local stress conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2185040','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2185040"><span id="translatedtitle">Surface properties of Entamoeba: increased <span class="hlt">rates</span> of human erythrocyte phagocytosis in pathogenic <span class="hlt">strains</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>1978-01-01</p> <p>The assertion that ingestion of human erythrocytes is restricted to invasive <span class="hlt">strains</span> of Entamoeba histolytica has not been evaluated previously by comparative studies. In this report we describe the in vitro ingestion of human erythrocytes by pathogenic and nonpathogenic Entamoeba. Microscopic evaluation of erythrophagocytosis by eight different Entamoeba grown in culture revealed that <span class="hlt">strains</span> of E. histolytica isolated from cases of human dysentery show a much higher <span class="hlt">rate</span> of erythrocyte ingestion than nonpathogenic <span class="hlt">strains</span>. However, all <span class="hlt">strains</span> are able to phagocytize erythrocytes. The extremely high <span class="hlt">rate</span> of phagocytic activity shown by pathogenic E. histolytica could be one of the properties related to the pathogenicity of this parasitic protozoan. PMID:722237</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790004051','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790004051"><span id="translatedtitle"><span class="hlt">Strain-rate</span>/temperature behavior of high density polyethylene in compression</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Clements, L. L.; Sherby, O. D.</p> <p>1978-01-01</p> <p>The compressive <span class="hlt">strain</span> <span class="hlt">rate</span>/temperature behavior of highly linear, high density polyethylene was analyzed in terms of the predictive relations developed for metals and other crystalline materials. For <span class="hlt">strains</span> of 5 percent and above, the relationship between applied <span class="hlt">strain</span> <span class="hlt">rate</span>, dotted epsilon, and resulting flow stress, sigma, was found to be: dotted epsilon exp times (Q sub f/RT) = k'(sigma/sigma sub c) to the nth power; the left-hand side is the activation-energy-compensated <span class="hlt">strain</span> <span class="hlt">rate</span>, where Q sub f is activation energy for flow, R is gas constant, and T is temperature; k is a constant, n is temperature-independent stress exponent, and sigma/sigma sub c is structure-compensated stress. A master curve resulted from a logarithmic plot of activation-energy-compensated <span class="hlt">strain</span> <span class="hlt">rate</span> versus structure-compensated stress.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008MMI....14..679R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008MMI....14..679R"><span id="translatedtitle">Mechanical analysis of woven composites at high <span class="hlt">strain</span> <span class="hlt">rates</span> and its application to predicting impact behavior</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ryou, Hansun; Chung, Kwansoo; Lim, Ji-Ho</p> <p>2008-12-01</p> <p>The deformation behavior of woven composites at high <span class="hlt">strain</span> <span class="hlt">rates</span> was analyzed using a constitutive equation developed to describe the nonlinear, anisotropic/asymmetric and <span class="hlt">rate</span>-dependent mechanical behavior of woven composites. The <span class="hlt">rate</span>-dependent nonlinear behavior of woven composites was characterized at high <span class="hlt">strain</span> <span class="hlt">rates</span> (1 s-1 to 100 s-1) using a tensile testing method first proposed in this research. The material properties for the developed constitutive equation were determined and subsequently used in a finite element analysis of the deformation behavior of woven composites at high <span class="hlt">strain</span> <span class="hlt">rates</span>. Finally, the impact behavior of woven composites was predicted using the constitutive equation and the results were compared with experiments, showing that the current constitutive equation including the characterization method is adequate to describe the deformation behavior of woven composites at high <span class="hlt">strain</span> <span class="hlt">rates</span> up to impact level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27480807','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27480807"><span id="translatedtitle"><span class="hlt">Strain</span> and <span class="hlt">rate</span>-dependent neuronal injury in a 3D in vitro compression model of traumatic brain injury.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bar-Kochba, Eyal; Scimone, Mark T; Estrada, Jonathan B; Franck, Christian</p> <p>2016-08-02</p> <p>In the United States over 1.7 million cases of traumatic brain injury are reported yearly, but predictive correlation of cellular injury to impact tissue <span class="hlt">strain</span> is still lacking, particularly for neuronal injury resulting from compression. Given the prevalence of compressive deformations in most blunt head trauma, this information is critically important for the development of future mitigation and diagnosis strategies. Using a 3D in vitro neuronal compression model, we investigated the role of impact <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> on neuronal lifetime, viability, and pathomorphology. We find that <span class="hlt">strain</span> magnitude and <span class="hlt">rate</span> have profound, yet distinctively different <span class="hlt">effects</span> on the injury pathology. While <span class="hlt">strain</span> magnitude affects the time of neuronal death, <span class="hlt">strain</span> <span class="hlt">rate</span> influences the pathomorphology and extent of population injury. Cellular injury is not initiated through localized deformation of the cytoskeleton but rather driven by excess <span class="hlt">strain</span> on the entire cell. Furthermore we find that, mechanoporation, one of the key pathological trigger mechanisms in stretch and shear neuronal injuries, was not observed under compression.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016NatSR...630550B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016NatSR...630550B"><span id="translatedtitle"><span class="hlt">Strain</span> and <span class="hlt">rate</span>-dependent neuronal injury in a 3D in vitro compression model of traumatic brain injury</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bar-Kochba, Eyal; Scimone, Mark T.; Estrada, Jonathan B.; Franck, Christian</p> <p>2016-08-01</p> <p>In the United States over 1.7 million cases of traumatic brain injury are reported yearly, but predictive correlation of cellular injury to impact tissue <span class="hlt">strain</span> is still lacking, particularly for neuronal injury resulting from compression. Given the prevalence of compressive deformations in most blunt head trauma, this information is critically important for the development of future mitigation and diagnosis strategies. Using a 3D in vitro neuronal compression model, we investigated the role of impact <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> on neuronal lifetime, viability, and pathomorphology. We find that <span class="hlt">strain</span> magnitude and <span class="hlt">rate</span> have profound, yet distinctively different <span class="hlt">effects</span> on the injury pathology. While <span class="hlt">strain</span> magnitude affects the time of neuronal death, <span class="hlt">strain</span> <span class="hlt">rate</span> influences the pathomorphology and extent of population injury. Cellular injury is not initiated through localized deformation of the cytoskeleton but rather driven by excess <span class="hlt">strain</span> on the entire cell. Furthermore we find that, mechanoporation, one of the key pathological trigger mechanisms in stretch and shear neuronal injuries, was not observed under compression.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4969749','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4969749"><span id="translatedtitle"><span class="hlt">Strain</span> and <span class="hlt">rate</span>-dependent neuronal injury in a 3D in vitro compression model of traumatic brain injury</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bar-Kochba, Eyal; Scimone, Mark T.; Estrada, Jonathan B.; Franck, Christian</p> <p>2016-01-01</p> <p>In the United States over 1.7 million cases of traumatic brain injury are reported yearly, but predictive correlation of cellular injury to impact tissue <span class="hlt">strain</span> is still lacking, particularly for neuronal injury resulting from compression. Given the prevalence of compressive deformations in most blunt head trauma, this information is critically important for the development of future mitigation and diagnosis strategies. Using a 3D in vitro neuronal compression model, we investigated the role of impact <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> on neuronal lifetime, viability, and pathomorphology. We find that <span class="hlt">strain</span> magnitude and <span class="hlt">rate</span> have profound, yet distinctively different <span class="hlt">effects</span> on the injury pathology. While <span class="hlt">strain</span> magnitude affects the time of neuronal death, <span class="hlt">strain</span> <span class="hlt">rate</span> influences the pathomorphology and extent of population injury. Cellular injury is not initiated through localized deformation of the cytoskeleton but rather driven by excess <span class="hlt">strain</span> on the entire cell. Furthermore we find that, mechanoporation, one of the key pathological trigger mechanisms in stretch and shear neuronal injuries, was not observed under compression. PMID:27480807</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/335367','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/335367"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> dependence of the tensile properties of V-(4--5%)Cr-(4--5%)Ti irradiated in EBR-II and HFBR</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zinkle, S.J.; Snead, L.L.; Robertson, J.P.; Rowcliffe, A.F.</p> <p>1998-03-01</p> <p>Elevated temperature tensile tests performed on V-(405)Cr-(4-5)Ti indicate that the yield stress increases with increasing <span class="hlt">strain</span> <span class="hlt">rate</span> for irradiation and test temperatures near 200 C, and decreases with increasing <span class="hlt">strain</span> <span class="hlt">rate</span> for irradiation and test temperatures near 400 C. This observation is in qualitative agreement with the temperature-dependent <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effects</span> observed on unirradiated specimens, and implies that some interstitial solute remains free to migrate in irradiated specimens. Additional <span class="hlt">strain</span> <span class="hlt">rate</span> data at different temperatures are needed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/394365','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/394365"><span id="translatedtitle">Mechanical response and microcrack formation in a fine-grained duplex TiAl at different <span class="hlt">strain</span> <span class="hlt">rates</span> and temperatures</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jin, Z.; Cady, C.; Gray, G.T. III; Kim, Y.-W.</p> <p>1996-10-01</p> <p>Compressive behavior of this alloy was studied at <span class="hlt">strain</span> <span class="hlt">rates</span> of 0. 001 and 2000 sec{sup -1} and temperatures from -196 C to 1200 C. Temperature dependence of yield stress was found to depend on <span class="hlt">strain</span> <span class="hlt">rate</span>: At the quasi-static <span class="hlt">strain</span> <span class="hlt">rate</span>, 0.001 sec{sup -1}, the yield stress decreases with temperature with a plateau between 200 and 800 C. At the high <span class="hlt">strain</span> <span class="hlt">rate</span>, 2000 sec{sup -1}, the yield stress exhibits a positive temperature dependence above 600 C. <span class="hlt">Strain</span> hardening <span class="hlt">rate</span> decreases dramatically with temperature in the very low and high temperature regions with a plateau at intermediate temperatures for both <span class="hlt">strain</span> <span class="hlt">rates</span>. As the <span class="hlt">strain</span> <span class="hlt">rate</span> increases, the <span class="hlt">strain</span> hardening <span class="hlt">rate</span> plateaus extended to higher temperatures. The <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity increases slightly with temperature (but less than 0.1) for <span class="hlt">strain</span> <span class="hlt">rates</span> above 0.001 sec{sup -1}. However, at a <span class="hlt">strain</span> <span class="hlt">rate</span> of 0.001 sec{sup -1}, there is a dramatic increase in the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity with temperature; above 1100 C, the <span class="hlt">rate</span> sensitivity becomes much larger. Microcracks occurring in grain interiors and at grain boundaries were observed at all <span class="hlt">strain</span> <span class="hlt">rates</span> and temperatures. Formation and distribution of microcracks were found to vary depending on <span class="hlt">strain</span> <span class="hlt">rate</span> and deformation temperature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27186468','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27186468"><span id="translatedtitle">Dynamic mechanical response and a constitutive model of Fe-based high temperature alloy at high temperatures and <span class="hlt">strain</span> <span class="hlt">rates</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Su, Xiang; Wang, Gang; Li, Jianfeng; Rong, Yiming</p> <p>2016-01-01</p> <p>The <span class="hlt">effects</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature on the dynamic behavior of Fe-based high temperature alloy was studied. The <span class="hlt">strain</span> <span class="hlt">rates</span> were 0.001-12,000 s(-1), at temperatures ranging from room temperature to 800 °C. A phenomenological constitutive model (Power-Law constitutive model) was proposed considering adiabatic temperature rise and accurate material thermal physical properties. During which, the <span class="hlt">effects</span> of the specific heat capacity on the adiabatic temperature rise was studied. The constitutive model was verified to be accurate by comparison between predicted and experimental results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PMagL..94...30G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PMagL..94...30G"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> response of a Ni-Ti shape memory alloy after hydrogen charging</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gamaoun, Fehmi; Hassine, Tarak; Bouraoui, Tarak</p> <p>2014-01-01</p> <p>In this work, we investigate the susceptibility of Ni-Ti superelastic wires to the <span class="hlt">strain</span> <span class="hlt">rates</span> during tensile testing after hydrogen charging. Cathodic hydrogen charging is performed at a current density of 10 A/m² during 2-12 h in 0.9% NaCl solution and aged for 24 h at room temperature. Specimens underwent one cycle of loading-unloading reaching a stress value of 700 MPa. During loading, <span class="hlt">strain</span> <span class="hlt">rates</span> from 10-6 to 5 × 10-2 s-1 have been achieved. After 8 h of hydrogen charging, an embrittlement has been detected in the tensile <span class="hlt">strain</span> <span class="hlt">rate</span> range of 10-6 to 10-4 s-1. In contrast, no embrittlement has been detected for <span class="hlt">strain</span> <span class="hlt">rates</span> of 10-3 s-1 and higher. However, after 12 h of hydrogen charging and 24 h of annealing at room temperature, the embrittlement occurs in the beginning of the austenite-martensite transformation for all the studied <span class="hlt">strain</span> <span class="hlt">rate</span> values. These results show that for a range of critical amounts of diffused hydrogen, the embrittlement of the Ni-Ti superelastic alloy strongly depends on the <span class="hlt">strain</span> <span class="hlt">rate</span> during the tensile test. Moreover, it has been shown that this embrittlement occurs for low values of <span class="hlt">strain</span> <span class="hlt">rates</span> rather than the higher ones. This behaviour is attributed to the interaction between the diffused hydrogen and growth of the martensitic domain.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT.......309K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT.......309K"><span id="translatedtitle">Predictions and Experimental Microstructural Characterization of High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Failure Modes in Layered Aluminum Composites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khanikar, Prasenjit</p> <p></p> <p> applications. The second major objective of this investigation was the use of recently developed dynamic fracture formulations to model and analyze the crack nucleation and propagation of aluminum layered composites subjected to high <span class="hlt">strain</span> <span class="hlt">rate</span> loading conditions and how microstructural <span class="hlt">effects</span>, such as precipitates, dispersed particles, and GB orientations affect failure evolution. This dynamic fracture approach is used to investigate crack nucleation and crack growth as a function of the different microstructural characteristics of each alloy in layered composites with and without pre-existing cracks. The zigzag nature of the crack paths were mainly due to the microstructural features, such as precipitates and dispersed particles distributions and orientations ahead of the crack front, and it underscored the capabilities of the fracture methodology. The evolution of dislocation density and the formation of localized shear slip contributed to the blunting of the propagating crack. Extensive geometrical and thermal softening due to the localized plastic slip also affected crack path orientations and directions. These softening mechanisms resulted in the switching of cleavage planes, which affected crack path orientations. Interface delamination can also have an important role in the failure and toughening of the layered composites. Different scenarios of delamination were investigated, such as planar crack growth and crack penetration into the layers. The presence of brittle surface oxide platelets in the interface region also significantly influenced the interface delamination process. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Optical Microscopy (OM) characterization provided further physical insights and validation of the predictive capabilities. The inherent microstructural features of each alloy play a significant role in the dynamic fracture, shear <span class="hlt">strain</span> localization, and interface delamination of the layered metallic composite</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/992761','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/992761"><span id="translatedtitle">EXPERIMENTAL TESTS OF VANADIUM STRENGTH MODELS AT HIGH PRESSURES AND <span class="hlt">STRAIN</span> <span class="hlt">RATES</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Park, H; Barton, N R; Becker, R C; Bernier, J V; Cavallo, R M; Lorenz, K T; Pollaine, S M; Remington, B A; Rudd, R E</p> <p>2010-03-02</p> <p>Experimental results showing significant reductions from classical in the Rayleigh-Taylor (RT) instability growth <span class="hlt">rate</span> due to high pressure material strength or <span class="hlt">effective</span> lattice viscosity in metal foils are presented. On the Omega Laser in the Laboratory for Laser Energetics, University of Rochester, target samples of polycrystalline vanadium are compressed and accelerated quasi-isentropically at {approx}1 Mbar pressures, while maintaining the samples in the solid-state. Comparison of the results with constitutive models for solid state strength under these conditions show that the measured RT growth is substantially lower than predictions using existing models that work well at low pressures and long time scales. High pressure, high <span class="hlt">strain</span> <span class="hlt">rate</span> data can be explained by the enhanced strength due to a phonon drag mechanism, creating a high <span class="hlt">effective</span> lattice viscosity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJWC..9402026W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9402026W"><span id="translatedtitle">Dynamic behaviour and shock-induced martensite transformation in near-beta Ti-5553 alloy under high <span class="hlt">strain</span> <span class="hlt">rate</span> loading</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Lin; Wang, Yangwei; Xu, Xin; Liu, Chengze</p> <p>2015-09-01</p> <p>Ti-5553 alloy is a near-beta titanium alloy with high strength and high fracture toughness. In this paper, the dynamic behaviour and shock-induced martensite phase transformation of Ti-5553 alloy with alpha/beta phases were investigated. Split Hopkinson Pressure Bar was employed to investigate the dynamic properties. Microstructure evolutions were characterized by Scanning Electronic Microscopy and Transmission Electron Microscope. The experimental results have demonstrated that Ti-5553 alloy with alpha/beta phases exhibits various <span class="hlt">strain</span> <span class="hlt">rate</span> hardening <span class="hlt">effects</span>, both failure through adiabatic shear band. Ti-5553 alloy with Widmannstatten microstructure exhibit more obvious <span class="hlt">strain</span> <span class="hlt">rate</span> hardening <span class="hlt">effect</span>, lower critical <span class="hlt">strain</span> <span class="hlt">rate</span> for ASB nucleation, compared with the alloy with Bimodal microstructures. Under dynamic compression, shock-induced beta to alpha" martensite transformation occurs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJWC..9404022S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9404022S"><span id="translatedtitle"><span class="hlt">Strain-rate</span> sensitivity of foam materials: A numerical study using 3D image-based finite element model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sun, Yongle; Li, Q. M.; Withers, P. J.</p> <p>2015-09-01</p> <p>Realistic simulations are increasingly demanded to clarify the dynamic behaviour of foam materials, because, on one hand, the significant variability (e.g. 20% scatter band) of foam properties and the lack of reliable dynamic test methods for foams bring particular difficulty to accurately evaluate the <span class="hlt">strain-rate</span> sensitivity in experiments; while on the other hand numerical models based on idealised cell structures (e.g. Kelvin and Voronoi) may not be sufficiently representative to capture the actual structural <span class="hlt">effect</span>. To overcome these limitations, the <span class="hlt">strain-rate</span> sensitivity of the compressive and tensile properties of closed-cell aluminium Alporas foam is investigated in this study by means of meso-scale realistic finite element (FE) simulations. The FE modelling method based on X-ray computed tomography (CT) image is introduced first, as well as its applications to foam materials. Then the compression and tension of Alporas foam at a wide variety of applied nominal <span class="hlt">strain-rates</span> are simulated using FE model constructed from the actual cell geometry obtained from the CT image. The stain-<span class="hlt">rate</span> sensitivity of compressive strength (collapse stress) and tensile strength (0.2% offset yield point) are evaluated when considering different cell-wall material properties. The numerical results show that the <span class="hlt">rate</span> dependence of cell-wall material is the main cause of the <span class="hlt">strain-rate</span> hardening of the compressive and tensile strengths at low and intermediate <span class="hlt">strain-rates</span>. When the <span class="hlt">strain-rate</span> is sufficiently high, shock compression is initiated, which significantly enhances the stress at the loading end and has complicated <span class="hlt">effect</span> on the stress at the supporting end. The plastic tensile wave <span class="hlt">effect</span> is evident at high <span class="hlt">strain-rates</span>, but shock tension cannot develop in Alporas foam due to the softening associated with single fracture process zone occurring in tensile response. In all cases the micro inertia of individual cell walls subjected to localised deformation is found to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/215380','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/215380"><span id="translatedtitle">Minimum <span class="hlt">strain</span> <span class="hlt">rate</span> and primary transient creep analysis of a fine structure orthorhombic titanium aluminide</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hayes, R.W.</p> <p>1996-03-15</p> <p>The purpose of the present paper is to present a preliminary analysis of the primary transient creep behavior of an orthorhombic titanium aluminide having a very fine microstructure. In order to analyze and understand the creep behavior within the primary transient regime it is necessary to understand the mechanisms controlling deformation within the minimum <span class="hlt">strain</span> <span class="hlt">rate</span> region. Therefore an analysis of the minimum <span class="hlt">strain</span> <span class="hlt">rate</span> behavior is also presented. It will be shown that the primary transient creep behavior is dependent upon whether creep in the minimum <span class="hlt">strain</span> <span class="hlt">rate</span> region is controlled by a viscous flow mechanism or a dislocation mechanism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA543927','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA543927"><span id="translatedtitle">Experimental Study of Solder/Copper Interface Failure Under Varying <span class="hlt">Strain</span> <span class="hlt">Rates</span></span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2011-03-01</p> <p>subjected to dynamic axial loads at <span class="hlt">strain</span> <span class="hlt">rates</span> between 10.0 s-1 and 0.05 s-1. The copper is alloy 101 and the lead-free solder has a composition of 96...OF SOLDER/COPPER INTERFACE FAILURE UNDER VARYING <span class="hlt">STRAIN</span> <span class="hlt">RATES</span> by Andrew Michael Luteran March 2011 Thesis Advisor: Young W. Kwon Second...tin and 4% silver. The tests results revealed that as the <span class="hlt">strain</span> <span class="hlt">rate</span> increases so do the ultimate and yield strengths but the elastic modulus</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990054047&hterms=rate+diffusion&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Drate%2Bdiffusion','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990054047&hterms=rate+diffusion&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Drate%2Bdiffusion"><span id="translatedtitle">The Extinction of Low <span class="hlt">Strain</span> <span class="hlt">Rate</span> Diffusion Flames by a Suppressant</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hamins, A.; Yang, J.; Puri, I. K.</p> <p>1999-01-01</p> <p>This paper describes plans for an experimental and computational study on the structure and extinction of low <span class="hlt">strain</span> <span class="hlt">rate</span> diffusion flames by a suppressant added to the oxidizer stream. Stable low <span class="hlt">strain</span> <span class="hlt">rate</span> flames will be established through ground based reduced gravity experiments using the 2.2 s drop tower. A variety of agents will be investigated, including both physically and chemically acting agents (He, N2, CO2, and CF3Br) for flames burning methane and propane. A computational model of flame structure and extinction will be modified to include radiative losses, which is thought to be a significant heat loss mechanism at low <span class="hlt">strain</span> <span class="hlt">rates</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA565575','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA565575"><span id="translatedtitle"><span class="hlt">Effect</span> of Hollow Sphere Size and Distribution on the Quasi-Static and High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Compressive Properties of Al-A380-Al2O3 Syntactic Foams</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2012-01-01</p> <p>static and high <span class="hlt">strain</span> <span class="hlt">rate</span> compressive properties of Al-A380-Al2O3 syntactic foams J. A. Santa Maria 1 , B. F. Schultz 1 , J. B. Ferguson 1 , N...variety of matrices including aluminum [7-22], magnesium [23], zinc [24], iron [15,22,25-26] and titanium [15,27] alloys. Various hollow spheres have been...5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) J. Santa Maria; B;. Schultz ; J. Ferguson; N. Gupta; P. Rohatgi 5d. PROJECT NUMBER 5e</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18352118','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18352118"><span id="translatedtitle">Local and nonlocal <span class="hlt">strain</span> <span class="hlt">rate</span> fields and vorticity alignment in turbulent flows.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hamlington, Peter E; Schumacher, Jörg; Dahm, Werner J A</p> <p>2008-02-01</p> <p>Local and nonlocal contributions to the total <span class="hlt">strain</span> <span class="hlt">rate</span> tensor S(ij) at any point x in a flow are formulated from an expansion of the vorticity field in a local spherical neighborhood of radius R centered on x. The resulting exact expression allows the nonlocal (background) <span class="hlt">strain</span> <span class="hlt">rate</span> tensor S(ij)(B)(x) to be obtained from S(ij)(x). In turbulent flows, where the vorticity naturally concentrates into relatively compact structures, this allows the local alignment of vorticity with the most extensional principal axis of the background <span class="hlt">strain</span> <span class="hlt">rate</span> tensor to be evaluated. In the vicinity of any vortical structure, the required radius R and corresponding order n to which the expansion must be carried are determined by the viscous length scale lambda(nu). We demonstrate the convergence to the background <span class="hlt">strain</span> <span class="hlt">rate</span> field with increasing R and n for an equilibrium Burgers vortex, and show that this resolves the anomalous alignment of vorticity with the intermediate eigenvector of the total <span class="hlt">strain</span> <span class="hlt">rate</span> tensor. We then evaluate the background <span class="hlt">strain</span> field S(ij)(B)(x) in direct numerical simulations of homogeneous isotropic turbulence where, even for the limited R and n corresponding to the truncated series expansion, the results show an increase in the expected equilibrium alignment of vorticity with the most extensional principal axis of the background <span class="hlt">strain</span> <span class="hlt">rate</span> tensor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApPhL.107j3701T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApPhL.107j3701T"><span id="translatedtitle">Physical mechanisms underlying the <span class="hlt">strain-rate</span>-dependent mechanical behavior of kangaroo shoulder cartilage</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thibbotuwawa, Namal; Oloyede, Adekunle; Li, Tong; Singh, Sanjleena; Senadeera, Wijitha; Gu, YuanTong</p> <p>2015-09-01</p> <p>Due to anatomical and biomechanical similarities to human shoulder, kangaroo was chosen as a model to study shoulder cartilage. Comprehensive enzymatic degradation and indentation tests were applied on kangaroo shoulder cartilage to study mechanisms underlying its <span class="hlt">strain-rate</span>-dependent mechanical behavior. We report that superficial collagen plays a more significant role than proteoglycans in facilitating <span class="hlt">strain-rate</span>-dependent behavior of the kangaroo shoulder cartilage. By comparing the mechanical properties of degraded and normal cartilages, it was noted that proteoglycan and collagen degradation significantly compromised <span class="hlt">strain-rate</span>-dependent mechanical behavior of the cartilage. Superficial collagen contributed equally to the tissue behavior at all <span class="hlt">strain-rates</span>. This is different to the studies reported on knee cartilage and confirms the importance of superficial collagen on shoulder cartilage mechanical behavior. A porohyperelastic numerical model also indicated that collagen disruption would lead to faster damage of the shoulder cartilage than when proteoglycans are depleted.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ChPhB..25l6201X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ChPhB..25l6201X"><span id="translatedtitle"><span class="hlt">Strain-rate</span>-induced bcc-to-hcp phase transformation of Fe nanowires</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xie, Hongxian; Yu, Tao; Fang, Wei; Yin, Fuxing; Faraz Khan, Dil</p> <p>2016-12-01</p> <p>Using molecular dynamics simulation method, the plastic deformation mechanism of Fe nanowires is studied by applying uniaxial tension along the [110] direction. The simulation result shows that the bcc-to-hcp martensitic phase transformation mechanism controls the plastic deformation of the nanowires at high <span class="hlt">strain</span> <span class="hlt">rate</span> or low temperature; however, the plastic deformation mechanism will transform into a dislocation nucleation mechanism at low <span class="hlt">strain</span> <span class="hlt">rate</span> and higher temperature. Furthermore, the underlying cause of why the bcc-to-hcp martensitic phase transition mechanism is related to high <span class="hlt">strain</span> <span class="hlt">rate</span> and low temperature is also carefully studied. Based on the present study, a <span class="hlt">strain</span> <span class="hlt">rate</span>-temperature plastic deformation map for Fe nanowires has been proposed. Project supported by the National Natural Science Foundation of China (Grant No. 51571082) and China Postdoctoral Science Foundation (Grant No. 2015M580191).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD0614567','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD0614567"><span id="translatedtitle"><span class="hlt">STRAIN</span>-ENERGY <span class="hlt">RATES</span> FOR A CLASS OF PERTURBATIONS OF BOUNDARY GEOMETRIES,</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p></p> <p>perturbations of boundary geometry. Application of the argument to the calculation of the <span class="hlt">rate</span> of change of the elastic <span class="hlt">strain</span> energy for a family of edge notches in tensile sheet is then demonstrated. (Author)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JMPSo..64..236C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JMPSo..64..236C"><span id="translatedtitle">Impact comminution of solids due to local kinetic energy of high shear <span class="hlt">strain</span> <span class="hlt">rate</span>: II-Microplane model and verification</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Caner, Ferhun C.; Bažant, Zdeněk P.</p> <p>2014-03-01</p> <p>The new theory presented in the preceding paper, which models the dynamic comminution of concrete due to very high shear <span class="hlt">strain</span> <span class="hlt">rate</span>, is now compared to recent test data on the penetration of projectiles through concrete walls of different thicknesses, ranging from 127 to 254 mm. These data are analyzed by an explicit finite element code using the new microplane constitutive model M7 for concrete, which was previously shown to provide the most realistic description of the quasi-static uni-, bi- and tri-axial test data with complex loading path and unloading. Model M7 incorporates the quasi-static <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effects</span> due viscoelasticity and to the <span class="hlt">rate</span> of cohesive crack debonding based on activation energy of bond ruptures, which are expected to extend to very high <span class="hlt">rates</span>. Here model M7 is further enhanced by apparent viscosity capturing the energy dissipation due to the <span class="hlt">strain-rate</span> <span class="hlt">effect</span> of comminution. The maximum shear <span class="hlt">strain</span> <span class="hlt">rates</span> in the computations are of the order of 105 s-1. The simulations document that, within the inevitable uncertainties, the measured exit velocities of the projectiles can be matched quite satisfactorily and the observed shapes of the entry and exit craters can be reproduced correctly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1981JMPSo..29..375M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1981JMPSo..29..375M"><span id="translatedtitle">Plastic flow of mild steel (En8) at different <span class="hlt">strain-rates</span> under abruptly-changing deformation paths</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meguid, S. A.</p> <p>1981-12-01</p> <p><span class="hlt">STRAIN</span>-GAUGED thin-walled tubular specimens of annealed medium carbon steel (En8) were tested at room temperature in combined twisting and extension using a closed-loop, servo-controlled, electro-hydraulic biaxial testing machine. Bilinear deformation paths of twisting at a constant <span class="hlt">rate</span> followed by extension at three different <span class="hlt">rates</span> were investigated. Precise measurements of the resulting torque and load, together with the controlled deformation parameters, were recorded as functions of time. This study extends earlier work ( MEGUID, MALVERN and CAMPBELL, 1979, J. Engng Mater. Technol.101, 248) in which a notable feature of this particular type of bilinear testing was reported: namely, that it was possible to obtain almost the entire positive quadrant of the initial yield locus from a single run without unloading or reloading (neutral loading). Here, particular attention has been given to the <span class="hlt">effect</span> of the axial <span class="hlt">strain-rate</span> on the shape of these "initial" yield loci. Attention has also been given to the <span class="hlt">effect</span> of the sudden change of direction in the deformation path upon the deviatoric stress and the plastic <span class="hlt">strain-rate</span> vectors. The results indicate that there exist appreciable differences between the Mises equivalent stress and equivalent plastic <span class="hlt">strain</span> curves (up to <span class="hlt">strains</span> of order 2%) for the three axial <span class="hlt">strain-rates</span> investigated. These differences are attributed to the <span class="hlt">rate</span>-sensitivity of the material. The results also show a much slower alignment of the deviatoric stress vector direction to the direction of the plastic <span class="hlt">strain-rate</span> vector than had been expected. Comparisons with two theoretical analyses of a bilinear deformation path of quasistatic twisting followed by extension at a constant <span class="hlt">strain-rate</span> are made, one using PERZYNA'S (1966) viscoplastic constitutive law for <span class="hlt">rate</span>-sensitive (but non-strainhardening) material and the other using a <span class="hlt">rate</span>-independent theory. Refinements in the test procedures now reveal that significant differences exist between</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA568946','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA568946"><span id="translatedtitle">Deformation Mechanisms and High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Properties of Magnesium (Mg) and Mg Alloys</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2012-08-01</p> <p>Deformation Mechanisms and High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Properties of Magnesium (Mg) and Mg Alloys by Bin Li, Logan Shannahan, Evan Ma, Kaliatt T. Ramesh...Properties of Magnesium (Mg) and Mg Alloys Bin Li, Logan Shannahan, Evan Ma, and Kaliatt T. Ramesh Johns Hopkins University Suveen Mathaudhu...Mechanisms and High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Properties of Magnesium (Mg) and Mg Alloys 5a. CONTRACT NUMBER W911NF-06-2-0006 5b. GRANT NUMBER 5c. PROGRAM ELEMENT</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20104684','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20104684"><span id="translatedtitle">Materials design and processings for industrial high-<span class="hlt">strain-rate</span> superplastic forming</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hosokawa, H.; Higashi, K.</p> <p>2000-07-01</p> <p>The optimum materials design in microstructural control could be developed for the high-<span class="hlt">strain-rate</span> superplastic materials in the industrial scale. In the present work, it is reported that the high-performance-engine pistons with near-net-shape can be fabricated by the superplastic forging technology in the high-<span class="hlt">strain-rate</span> superplastic PM Al-Si based alloy, which is produced by using this optimum materials design.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA598482','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA598482"><span id="translatedtitle">Dynamic Evolution of Acrylonitrile Butadiene Styrene (ABS) Subjected to High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Compressive Loads</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2013-01-01</p> <p>Salisbury, M. Worswick, D. Lloyd, M. Finn, High <span class="hlt">strain</span> <span class="hlt">rate</span> tensile testing of automotive aluminum alloy sheet, International Journal of Impact...selected aluminum alloys, Materials Science and Engineering: A, Volume 278, Issues 1–2, 15 February 2000, Pages 225-235 [6] A.G. Odeshi, S. Al-ameeri...mechanical behavior of the of 3D-printed Acrylonitrile Butadiene Styrene material to assess potential <span class="hlt">strain</span> <span class="hlt">rate</span> dependency. The mechanical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/225140','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/225140"><span id="translatedtitle">Yield and work hardening of TiAl in the regime of inverse <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature dependence</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bartels, A.; Koeppe, C.; Zhang, T.; Mecking, H.</p> <p>1995-12-31</p> <p>By a two-step forging method an equiaxed microstructure was adjusted in Ti-48Al-2Cr and compression tests were performed between room temperature and 600 C. Above 250 C the normalized yield stress increases with increasing temperature but does not depend on <span class="hlt">strain</span> <span class="hlt">rate</span>. Up to about 400 C the work hardening is insensitive to temperature and dynamic recovery occurs above this temperature. A negative <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity {partial_derivative}{sigma}/{partial_derivative}(ln{dot {var_epsilon}}) in combination with serrated flow (Portevin Le Chatelier <span class="hlt">effect</span>) develops during deformation in a temperature range between about 150 C and 450 C.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhL.109i4102C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhL.109i4102C"><span id="translatedtitle">Yielding of tantalum at <span class="hlt">strain</span> <span class="hlt">rates</span> up to 109 s-1</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Crowhurst, Jonathan C.; Armstrong, Michael R.; Gates, Sean D.; Zaug, Joseph M.; Radousky, Harry B.; Teslich, Nick E.</p> <p>2016-08-01</p> <p>We have used a 45 μJ laser pulse to accelerate the free surface of fine-grained tantalum films up to peak velocities of ˜1.2 km s-1. The films had thicknesses of ˜1-2 μm and in-plane grain widths of ˜75-150 nm. Using ultrafast interferometry, we have measured the time history of the velocity of the surface at different spatial positions across the accelerated region. The initial part of the histories (assumed to correspond to the "elastic precursor" observed previously) exhibited measured <span class="hlt">strain</span> <span class="hlt">rates</span> of ˜0.6 to ˜3.2 × 109 s-1 and stresses of ˜4 to ˜22 GPa. Importantly, we find that elastic amplitudes exhibit little variation with <span class="hlt">strain</span> <span class="hlt">rate</span> for a constant peak surface velocity, even though, via covariation of the <span class="hlt">strain</span> <span class="hlt">rate</span> with peak surface velocity, they vary with <span class="hlt">strain</span> <span class="hlt">rate</span>. Furthermore, by comparison with data obtained at lower <span class="hlt">strain</span> <span class="hlt">rates</span>, we find that amplitudes are much better predicted by peak velocities rather than by either <span class="hlt">strain</span> <span class="hlt">rate</span> or sample thickness.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PApGe.173.2857P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PApGe.173.2857P"><span id="translatedtitle">Micromechanics-Based Permeability Evolution in Brittle Materials at High <span class="hlt">Strain</span> <span class="hlt">Rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Perol, Thibaut; Bhat, Harsha S.</p> <p>2016-08-01</p> <p>We develop a micromechanics-based permeability evolution model for brittle materials at high <span class="hlt">strain</span> <span class="hlt">rates</span> (≥ 100 s^{-1}). Extending for undrained deformation the mechanical constitutive description of brittle solids, whose constitutive response is governed by micro-cracks, we now relate the damage-induced <span class="hlt">strains</span> to micro-crack aperture. We then use an existing permeability model to evaluate the permeability evolution. This model predicts both the percolative and connected regime of permeability evolution of Westerly Granite during triaxial loading at high <span class="hlt">strain</span> <span class="hlt">rate</span>. This model can simulate pore pressure history during earthquake coseismic dynamic ruptures under undrained conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EPJST.225..295S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EPJST.225..295S"><span id="translatedtitle">High speed imaging for material parameters calibration at high <span class="hlt">strain</span> <span class="hlt">rate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sasso, M.; Fardmoshiri, M.; Mancini, E.; Rossi, M.; Cortese, L.</p> <p>2016-05-01</p> <p>To describe the material behaviour at high <span class="hlt">strain</span> <span class="hlt">rates</span> dynamic experimental tests are necessary, and appropriate constitutive models are to be calibrated accordingly. A way to achieve this is through an inverse procedure, based on the minimization of an error function calculated as the difference between experimental and numerical data coming from Finite Element analysis. This approach, widely used in the literature, has a heavy computational cost associated with the minimization process that requires, for each variation of the material model parameters, the execution of FE calculations. In this work, a faster but yet <span class="hlt">effective</span> calibration procedure is studied Experimental tests were performed on an aluminium alloy AA6061-T6, by means of a direct tension-compression Split Hopkinson bar. A fast camera with a resolution of 192 × 128 pixels and capable of a sample <span class="hlt">rate</span> of 100,000 fps captured images of the deformation process undergone by the samples during the tests. The profile of the sample obtained after the image binarization and processing, was postprocessed to derive the deformation history; afterwards it was possible to calculate the true stress and <span class="hlt">strain</span>, and carry out the inverse calibration by analytical computations. The results of this method were compared with the ones coming from the Finite Element approach.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUSM.G33A..05M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUSM.G33A..05M"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">Rate</span> into South American Plate by SIRGAS-CON Geodetic Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marotta, G. S.; Franca, G. S.; Monico, J. G.; Fuck, R. A.</p> <p>2013-05-01</p> <p>In this study were investigated the surface <span class="hlt">strain</span> <span class="hlt">rates</span> computed from the direction variations and velocity values estimated from the coordinates of the continuous monitoring geodetic network called SIRGAS-CON. That investigation was done using points located in the South American plate. The determination of the <span class="hlt">strain</span> <span class="hlt">rate</span> was based on the Finite Element method using points defined by Delaunay triangulation (sub-networks). Each one of sub-networks was considered as an homogeneous solid body. Using these methods was possible to separate the <span class="hlt">strain</span> from the plate movement. The results showed that there are differences of <span class="hlt">strain</span> <span class="hlt">rate</span> along the South American plate. From the results were suggest that near to the west board of the plate, the <span class="hlt">strain</span> is more significant, as expected, because this region is near to one area where Nazca Plate subduct South American Plate. It was detected that the contraction region founded in this area coincides whit the region where occurs most of earthquakes of greater magnitude. Far from the board, there are some areas with anomalies of significant <span class="hlt">strain</span> of extension and contraction that can be originated by differences of stress aligned with different geological composites. By the results, It may be concluded that large surface movements occur in regions with more heterogeneous geological structures and multiple event of rupture, that large earthquakes arising from large tectonic activity into South American Plate are concentrated in areas with contraction <span class="hlt">strain</span> <span class="hlt">rates</span> predominantly oriented towards northeast-southwest, that significant amounts of elastic <span class="hlt">strain</span> can be accumulated over geological structures away from fault plate boundary and that the behavior of contractions and extensions are similar to that found by different researches involving geophysical studies. Dilation and principal components of <span class="hlt">strain</span> <span class="hlt">rate</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030068093','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030068093"><span id="translatedtitle">LS-DYNA Implementation of Polymer Matrix Composite Model Under High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Impact</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zheng, Xia-Hua; Goldberg, Robert K.; Binienda, Wieslaw K.; Roberts, Gary D.</p> <p>2003-01-01</p> <p>A recently developed constitutive model is implemented into LS-DYNA as a user defined material model (UMAT) to characterize the nonlinear <span class="hlt">strain</span> <span class="hlt">rate</span> dependent behavior of polymers. By utilizing this model within a micromechanics technique based on a laminate analogy, an algorithm to analyze the <span class="hlt">strain</span> <span class="hlt">rate</span> dependent, nonlinear deformation of a fiber reinforced polymer matrix composite is then developed as a UMAT to simulate the response of these composites under high <span class="hlt">strain</span> <span class="hlt">rate</span> impact. The models are designed for shell elements in order to ensure computational efficiency. Experimental and numerical stress-<span class="hlt">strain</span> curves are compared for two representative polymers and a representative polymer matrix composite, with the analytical model predicting the experimental response reasonably well.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JAP...114x4901E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JAP...114x4901E"><span id="translatedtitle">Dynamic tensile fracture of mortar at ultra-high <span class="hlt">strain-rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Erzar, B.; Buzaud, E.; Chanal, P.-Y.</p> <p>2013-12-01</p> <p>During the lifetime of a structure, concrete and mortar may be exposed to highly dynamic loadings, such as impact or explosion. The dynamic fracture at high loading <span class="hlt">rates</span> needs to be well understood to allow an accurate modeling of this kind of event. In this work, a pulsed-power generator has been employed to conduct spalling tests on mortar samples at <span class="hlt">strain-rates</span> ranging from 2 × 104 to 4 × 104 s-1. The ramp loading allowed identifying the <span class="hlt">strain-rate</span> anytime during the test. A power law has been proposed to fit properly the <span class="hlt">rate</span>-sensitivity of tensile strength of this cementitious material over a wide range of <span class="hlt">strain-rate</span>. Moreover, a specimen has been recovered damaged but unbroken. Micro-computed tomography has been employed to study the characteristics of the damage pattern provoked by the dynamic tensile loading.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12884964','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12884964"><span id="translatedtitle">A <span class="hlt">rating</span> scale for wildness and ease of handling laboratory mice: results for 21 inbred <span class="hlt">strains</span> tested in two laboratories.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wahlsten, D; Metten, P; Crabbe, J C</p> <p>2003-04-01</p> <p><span class="hlt">Rating</span> scales for difficulty in capturing and holding mice were devised that proved to be easy to use and highly sensitive to differences among mouse <span class="hlt">strains</span> on the A and B priority lists of the Mouse Phenome Project. The simplicity of the scales makes it feasible to <span class="hlt">rate</span> wildness during behavioral test sessions without adding much to testing time or distracting the technician from the principal task at hand. Overall wildness and placidity <span class="hlt">ratings</span> obtained by combining capture and hold <span class="hlt">ratings</span> provide a good impression of the difficulties encountered while working with lab mice in the course of complex experiments. <span class="hlt">Ratings</span> of 21 inbred <span class="hlt">strains</span> during the course of 15 behavioral tests in two laboratories demonstrated that the SPRET/Ei, PERA/Ei, CAST/Ei and SWR/J <span class="hlt">strains</span> were particularly difficult to handle. The NOD/LtJ <span class="hlt">strain</span> posed no special challenge in the Edmonton laboratory but was very difficult to handle in the Portland lab. The <span class="hlt">rating</span> scales should be useful for judging the difficulties in working with novel targeted or induced mutations in mice as well as <span class="hlt">effects</span> of a variety of environmental treatments or drugs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/6654926','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/6654926"><span id="translatedtitle"><span class="hlt">Strain-rate</span> dependence of the compressive properties of normal and carbon-fiber-reinforced bone cement.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Saha, S; Pal, S</p> <p>1983-11-01</p> <p>Normal and carbon-fiber-reinforced (1 wt. %) bone cement samples were tested in compression at various <span class="hlt">strain</span> <span class="hlt">rates</span>. Both the compressive strength and proportional limit increased in general with increasing <span class="hlt">strain</span> <span class="hlt">rate</span>. Similar <span class="hlt">strain-rate</span> sensitivity was also shown by the carbon-fiber-reinforced bone cement. The mechanical properties, namely the modulus of elasticity, the proportional limit, and the compressive strength of the carbon-fiber-reinforced bone cement showed highly significant positive correlations with the <span class="hlt">strain</span> <span class="hlt">rate</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950021867','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950021867"><span id="translatedtitle">Static and dynamic <span class="hlt">strain</span> energy release <span class="hlt">rates</span> in toughened thermosetting composite laminates</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cairns, Douglas S.</p> <p>1992-01-01</p> <p>In this work, the static and dynamic fracture properties of several thermosetting resin based composite laminates are presented. Two classes of materials are explored. These are homogeneous, thermosetting resins and toughened, multi-phase, thermosetting resin systems. Multi-phase resin materials have shown enhancement over homogenous materials with respect to damage resistance. The development of new dynamic tests are presented for composite laminates based on Width Tapered Double Cantilevered Beam (WTDCB) for Mode 1 fracture and the End Notched Flexure (ENF) specimen. The WTDCB sample was loaded via a low inertia, pneumatic cylinder to produce rapid cross-head displacements. A high <span class="hlt">rate</span>, piezo-electric load cell and an accelerometer were mounted on the specimen. A digital oscilloscope was used for data acquisition. Typical static and dynamic load versus displacement plots are presented. The ENF specimen was impacted in three point bending with an instrumented impact tower. Fracture initiation and propagation energies under static and dynamic conditions were determined analytically and experimentally. The test results for Mode 1 fracture are relatively insensitive to <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effects</span> for the laminates tested in this study. The test results from Mode 2 fracture indicate that the toughened systems provide superior fracture initiation and higher resistance to propagation under dynamic conditions. While the static fracture properties of the homogeneous systems may be relatively high, the apparent Mode 2 dynamic critical <span class="hlt">strain</span> energy release <span class="hlt">rate</span> drops significantly. The results indicate that static Mode 2 fracture testing is inadequate for determining the fracture performance of composite structures subjected to conditions such as low velocity impact. A good correlation between the basic Mode 2 dynamic fracture properties and the performance is a combined material/structural Compression After Impact (CAI) test is found. These results underscore the importance of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19830016271','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19830016271"><span id="translatedtitle">Flow <span class="hlt">rate</span>/pressure drop data gathered from testing a sample of the Space Shuttle <span class="hlt">Strain</span> Isolation Pad (SIP): <span class="hlt">Effects</span> of ambient pressure combined with tension and compression conditions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Springfield, R. D.; Lawing, P. L.</p> <p>1983-01-01</p> <p>Tests were conducted on a sample of <span class="hlt">strain</span> isolation pad (SIP) typical of that used in the shuttle orbiter thermal protection system to determine the characteristics of SIP internal flow. Data obtained were pressure drop as a function of flow <span class="hlt">rate</span> for a range of ambient pressures representing various points along the Shuttle trajectory and for stretched and compressed conditions of the SIP. Flow was in the direction of the weave parallel to most of the fibers. The data are plotted in several standard engineering formats in order to be of maximum utility to the user. In addition to providing support to the Space Shuttle Program, these data are a source of experimental information on flow through fiberous (rather than the more usual sand bed type) porous media.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/237733','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/237733"><span id="translatedtitle">High <span class="hlt">strain</span> <span class="hlt">rate</span> mechanical properties of IM7/8551-7 graphite epoxy composite</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Powers, B.M.; Vinson, J.R.; Hall, I.W.</p> <p>1995-12-31</p> <p>Polymer matrix composites offer excellent mechanical properties such as high specific strength and stiffness which make them attractive for many naval, aerospace and automotive structural components. Although they are candidate materials for many applications where high <span class="hlt">strain</span> <span class="hlt">rate</span> loading is probable, little is known of the material responses to shock loading for most composite materials. Because mechanical properties vary significantly with <span class="hlt">strain</span> <span class="hlt">rate</span>, the use of static properties in the analysis and design of structures which undergo dynamic loadings can on one hand lead to a very conservative overweight design, or on the other hand can lead to designs which fail prematurely and unexpectedly. The use of dynamic material properties will ensure the design of composite structures which are weight efficient and structurally sound when they are subjected to dynamic loads. In this study, a Split Hopkinson Pressure Bar is used to obtain compressive mechanical properties of a unidirectional IM7/8551-7 graphite epoxy composite. For each of the three principal directions, the yield stress, yield <span class="hlt">strain</span>, ultimate stress, ultimate <span class="hlt">strain</span>, modulus of elasticity, elastic <span class="hlt">strain</span> energy function and the total <span class="hlt">strain</span> energy to failure are presented for <span class="hlt">strain</span> <span class="hlt">rates</span> varying from 49 sec{sup {minus}1} to 1430 sec{sup {minus}1}. The data from 72 tests are statistically analyzed, represented by equations, and discussed in some detail.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MS%26E...75a2031M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MS%26E...75a2031M"><span id="translatedtitle">Study of mechanical properties, microstructures and corrosion behavior of al 7075 t651 alloy with varying <span class="hlt">strain</span> <span class="hlt">rate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mukherjee, A.; Ghosh, M.; Mondal, K.; Venkitanarayanan, P.; Moon, A. P.; Varshney, A.</p> <p>2015-02-01</p> <p>Compression test of Al 7075 T651 was carried out at high <span class="hlt">strain</span> <span class="hlt">rates</span> (1138 - 2534 s-1) using Split Hopkinson Pressure Bar and at slow <span class="hlt">strain</span> <span class="hlt">rate</span> (10-4s-1) in 100KN Universal Testing machine to understand the improvement in mechanical properties and associated changes in microstructures. Cylindrical specimens of 6 mm height and 6 mm diameter were compressed dynamically. The influence of <span class="hlt">strain</span> <span class="hlt">rates</span> on mechanical properties, microstructure evolution and corrosion behavior after immersion test in 3.5% NaCl solution was also investigated. <span class="hlt">Strain</span> <span class="hlt">rate</span>, withdrawal stress and yield stress were observed to increase with impact velocity in high <span class="hlt">strain</span> <span class="hlt">rate</span> tests, while in slow <span class="hlt">strain</span> <span class="hlt">rate</span> tests, n value was observed to increase with increasing total <span class="hlt">strain</span>. Microstructural observations revealed that after high <span class="hlt">strain</span> <span class="hlt">rate</span> test, grains of Al matrix were elongated. It was observed that corrosion resistance decreased with increase in impact velocity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JNR....19...21A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JNR....19...21A"><span id="translatedtitle">Influence of particle size on the low and high <span class="hlt">strain</span> <span class="hlt">rate</span> behavior of dense colloidal dispersions of nanosilica</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Asija, Neelanchali; Chouhan, Hemant; Gebremeskel, Shishay Amare; Bhatnagar, Naresh</p> <p>2017-01-01</p> <p>Shear thickening is a non-Newtonian flow behavior characterized by the increase in apparent viscosity with the increase in applied shear <span class="hlt">rate</span>, particularly when the shear <span class="hlt">rate</span> exceeds a critical value termed as the critical shear <span class="hlt">rate</span> (CSR). Due to this remarkable property of shear-thickening fluids (STFs), they are extensively used in hip protection pads, protective gear for athletes, and more recently in body armor. The use of STFs in body armor has led to the development of the concept of liquid body armor. In this study, the <span class="hlt">effect</span> of particle size is explored on the low and high <span class="hlt">strain</span> <span class="hlt">rate</span> behavior of nanosilica dispersions, so as to predict the efficacy of STF-aided personal protection systems (PPS), specifically for ballistic applications. The low <span class="hlt">strain</span> <span class="hlt">rate</span> study was conducted on cone and plate rheometer, whereas the high <span class="hlt">strain</span> <span class="hlt">rate</span> characterization of STF was conducted on in-house fabricated split Hopkinson pressure bar (SHPB) system. Spherical nanosilica particles of three different sizes (100, 300, and 500 nm) as well as fumed silica particles of four different specific surface areas (Aerosil A-90, A-130, A-150, and A-200), respectively, were used in this study. The test samples were prepared by dispersing nanosilica particles in polypropylene glycol (PPG) using ultrasonic homogenization method. The low <span class="hlt">strain</span> <span class="hlt">rate</span> studies aided in determining the CSR of the synthesized STF dispersions, whereas the high <span class="hlt">strain</span> <span class="hlt">rate</span> studies explored the impact-resisting ability of STFs in terms of the impact toughness and the peak stress attained during the impact loading of STF in SHPB testing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1021293','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1021293"><span id="translatedtitle">High-<span class="hlt">Strain-Rate</span> Forming of Aluminum and Steel Sheets for Automotive Applications</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rohatgi, Aashish; Stephens, Elizabeth V; Soulami, Ayoub; Davies, Richard W; Smith, Mark T</p> <p>2010-06-01</p> <p>The formability of aluminum alloy AA5182-O and DP600 steel sheets at high-<span class="hlt">strain-rates</span> was investigated using an electrohydraulic forming (EHF) setup. Test sheets, ~150 mm diameter x 1 mm thick, were clamped around their circumference and subjected to a pressure-pulse (several 100's duration) generated by a high-energy (up to ~34 kJ) under-water electrical discharge. The real-time <span class="hlt">strain</span> and <span class="hlt">strain-rate</span> of the deforming sheets were quantified by the digital image correlation (DIC) technique using a pair of high-speed cameras (~15's per frame). <span class="hlt">Strain-rate</span> amplification was observed when the sheets were deformed into a conical die, with the maximum in-plane <span class="hlt">strain-rate</span> and <span class="hlt">strain</span> for aluminum measured as ~1200 /s and ~0.2, respectively. The deformation behavior of the sheets was modeled using ABAQUS/finite element explicit code and better correlation, between the predicted and the experimental sheet deformation behavior, was observed when an alternate pressure-profile was used instead of the one available from the literature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoJI.205..509R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoJI.205..509R"><span id="translatedtitle">Earthquake potential and magnitude limits inferred from a geodetic <span class="hlt">strain-rate</span> model for southern Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rong, Y.; Bird, P.; Jackson, D. D.</p> <p>2016-04-01</p> <p>The project Seismic Hazard Harmonization in Europe (SHARE), completed in 2013, presents significant improvements over previous regional seismic hazard modeling efforts. The Global <span class="hlt">Strain</span> <span class="hlt">Rate</span> Map v2.1, sponsored by the Global Earthquake Model Foundation and built on a large set of self-consistent geodetic GPS velocities, was released in 2014. To check the SHARE seismic source models that were based mainly on historical earthquakes and active fault data, we first evaluate the SHARE historical earthquake catalogues and demonstrate that the earthquake magnitudes are acceptable. Then, we construct an earthquake potential model using the Global <span class="hlt">Strain</span> <span class="hlt">Rate</span> Map data. SHARE models provided parameters from which magnitude-frequency distributions can be specified for each of 437 seismic source zones covering most of Europe. Because we are interested in proposed magnitude limits, and the original zones had insufficient data for accurate estimates, we combine zones into five groups according to SHARE's estimates of maximum magnitude. Using the <span class="hlt">strain</span> <span class="hlt">rates</span>, we calculate tectonic moment <span class="hlt">rates</span> for each group. Next, we infer seismicity <span class="hlt">rates</span> from the tectonic moment <span class="hlt">rates</span> and compare them with historical and SHARE seismicity <span class="hlt">rates</span>. For two of the groups, the tectonic moment <span class="hlt">rates</span> are higher than the seismic moment <span class="hlt">rates</span> of the SHARE models. Consequently, the <span class="hlt">rates</span> of large earthquakes forecast by the SHARE models are lower than those inferred from tectonic moment <span class="hlt">rate</span>. In fact, the SHARE models forecast higher seismicity <span class="hlt">rates</span> than the historical <span class="hlt">rates</span>, which indicate that the authors of SHARE were aware of the potentially higher seismic activities in the zones. For one group, the tectonic moment <span class="hlt">rate</span> is lower than the seismic moment <span class="hlt">rates</span> forecast by the SHARE models. As a result, the <span class="hlt">rates</span> of large earthquakes in that group forecast by the SHARE model are higher than those inferred from tectonic moment <span class="hlt">rate</span>, but lower than what the historical data show. For the other two</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA378949','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA378949"><span id="translatedtitle">High <span class="hlt">Strain-Rate</span> and Quasi-Static Ductile Failure Mechanisms in Porous Materials</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2007-11-02</p> <p>detailed understanding of the interrelated physical mechanisms that can result in ductile material failure in <span class="hlt">rate</span>-dependent porous crystalline materials subjected...<span class="hlt">strains</span> and slip-<span class="hlt">rates</span>, and hydrostatic stresses on failure paths and ligament damage in face centered cubic (f.c.c.) crystalline materials have been</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19810007620','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19810007620"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span>, temperature, and humidity on strength and moduli of a graphite/epoxy composite</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lifshitz, J. M.</p> <p>1981-01-01</p> <p>Results of an experimental study of the influence of <span class="hlt">strain</span> <span class="hlt">rate</span>, temperature and humidity on the mechanical behavior of a graphite/epoxy fiber composite are presented. Three principal strengths (longitudinal, transverse and shear) and four basic moduli (E1, E2, G12 and U12) of a unidirectional graphite/epoxy composite were followed as a function of <span class="hlt">strain</span> <span class="hlt">rate</span>, temperature and humidity. Each test was performed at a constant tensile <span class="hlt">strain</span> <span class="hlt">rate</span> in an environmental chamber providing simultaneous temperature and humidity control. Prior to testing, specimens were given a moisture preconditioning treatment at 60 C. Values for the matrix dominated moduli and strength were significantly influenced by both environmental and <span class="hlt">rate</span> parameters, whereas the fiber dominated moduli were not. However, the longitudinal strength was significantly influenced by temperature and moisture content. A qualitative explanation for these observations is presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MMI....21..823X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MMI....21..823X"><span id="translatedtitle">Compressive behavior and constitutive analysis of AZ31B magnesium alloy over wide range of <span class="hlt">strain</span> <span class="hlt">rates</span> and temperatures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xiao, Jing; Shu, Dong Wei</p> <p>2015-09-01</p> <p>Magnesium and its alloys with low specific weight, high specific strength, vast resources, easy recyclability and biodegradation have attracted extensive interest in recent years as an ideal candidate to aluminium and steel alloys. The knowledge of the mechanical properties under high <span class="hlt">strain</span> <span class="hlt">rate</span> loading and elevated temperature is necessary for the structural application of magnesium alloy in automotive, aerospace and defence industries. Compressive tests on AZ31B magnesium alloy were carried out at both quasi-static and high <span class="hlt">strain</span> <span class="hlt">rate</span> loading in a range between 10-3 s-1 and 3300 s-1 while temperature varies from -30 °C to 200 °C. <span class="hlt">Strain</span> <span class="hlt">rate</span> and temperature <span class="hlt">effect</span> on flow stress, hardening behavior, <span class="hlt">rate</span> sensitivity, ductility and energy absorption capability of the alloy is discussed. Optical and scanning electron microscopy was performed on selected specimens at quasi-static and high <span class="hlt">strain</span> <span class="hlt">rates</span> under room temperature. The Johnson-Cook model is fit to the measured data and predictions from the model are compared with the experimental data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1243352','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1243352"><span id="translatedtitle">Experimental study of vorticity-<span class="hlt">strain</span> <span class="hlt">rate</span> interaction in turbulent partially-premixed jet flames using tomographic particle image velocimetry</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Coriton, Bruno; Frank, Jonathan H.</p> <p>2016-02-16</p> <p>In turbulent flows, the interaction between vorticity, ω, and <span class="hlt">strain</span> <span class="hlt">rate</span>, s, is considered a primary mechanism for the transfer of energy from large to small scales through vortex stretching. The ω-s coupling in turbulent jet flames is investigated using tomographic particle image velocimetry (TPIV). TPIV provides a direct measurement of the three-dimensional velocity field from which ω and s are determined. The <span class="hlt">effects</span> of combustion and mean shear on the ω-s interaction are investigated in turbulent partially premixed methane/air jet flames with high and low probabilities of localized extinction as well as in a non-reacting isothermal air jet with Reynolds number of approximately 13,000. Results show that combustion causes structures of high vorticity and <span class="hlt">strain</span> <span class="hlt">rate</span> to agglomerate in highly correlated, elongated layers that span the height of the probe volume. In the non-reacting jet, these structures have a more varied morphology, greater fragmentation, and are not as well correlated. The enhanced spatiotemporal correlation of vorticity and <span class="hlt">strain</span> <span class="hlt">rate</span> in the stable flame results in stronger ω-s interaction characterized by increased enstrophy and <span class="hlt">strain-rate</span> production <span class="hlt">rates</span> via vortex stretching and <span class="hlt">straining</span>, respectively. The probability of preferential local alignment between ω and the eigenvector of the intermediate principal <span class="hlt">strain</span> <span class="hlt">rate</span>, s<sub>2</sub>, which is intrinsic to the ω-s coupling in turbulent flows, is larger in the flames and increases with the flame stability. The larger mean shear in the flame imposes a preferential orientation of ω and s<sub>2</sub> tangential to the shear layer. The extensive and compressive principal <span class="hlt">strain</span> <span class="hlt">rates</span>, s<sub>1</sub> and s<sub>3</sub>, respectively, are preferentially oriented at approximately 45° with respect to the jet axis. As a result, the production <span class="hlt">rates</span> of <span class="hlt">strain</span> and vorticity tend to be dominated by instances in which ω is parallel to the s<sub>1</sub>¯-s<sub>2</sub>¯ plane and orthogonal</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDR17006R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDR17006R"><span id="translatedtitle">Influence of Aerodynamic <span class="hlt">Strain</span> <span class="hlt">Rate</span> on Local Extinction in Turbulent Non-premixed Jet Flames</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ramachandran, Aravind; Narayanaswamy, Venkateswaran; Lyons, Kevin</p> <p>2016-11-01</p> <p>2-D velocity field measurements obtained from Particle Image Velocimetry (PIV) are used to obtain aerodynamic <span class="hlt">strain</span> <span class="hlt">rate</span> information in regions of local extinction in lifted turbulent non-premixed methane jet flames in coflow. Diluting the coflow to reduce the oxygen molefraction results in increased occurrences of local extinction. Statistical analysis is performed to correlate regions of high local <span class="hlt">strain</span> <span class="hlt">rate</span> with local extinctions in both air coflow and diluted coflow cases to study the influence of <span class="hlt">strain</span> <span class="hlt">rate</span> against vortical structures in extinguishing the flame front. A comparison is also made with heated and vitiated coflow cases, where autoignition is a flame stabilization mechanism and influenced by local <span class="hlt">strain</span> <span class="hlt">rate</span>. At high jet exit velocities (Ux > > Ur), the out-of-plane <span class="hlt">strain</span> <span class="hlt">rate</span> component can be neglected but the convection of extinguished pockets into the measurement plane needs to be resolved by stereoscopic (3-D) measurements which will be done in a future work. This work has been supported by the U.S. Army Research Office (Contracts W911NF1210140 and W911NF1610087) Dr. Ralph Anthenien, Technical Monitor, ARO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JMEP...25.3558V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JMEP...25.3558V"><span id="translatedtitle">On the <span class="hlt">Strain</span> <span class="hlt">Rate</span> Sensitivity of Abs and Abs Plus Fused Deposition Modeling Parts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vairis, A.; Petousis, M.; Vidakis, N.; Savvakis, K.</p> <p>2016-09-01</p> <p>In this work the <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> on the tensile strength of fused deposition modeling parts built with Acrylonitrile-butadiene-styrene (ABS) and ABS plus material is presented. ASTM D638-02a specimens were built with ABS and ABS plus and they were tested on a Schenck Trebel Co. tensile test machine at three different test speeds, equal, lower, and higher to the test speed required by the ASTM D638-02a standard. The experimental tensile strength results were compared and evaluated. The fracture surfaces of selected specimens were examined with a scanning electron microscope, to determine failure mode of the filament strands. It was found that, as the test speed increases, specimens develop higher tensile strength and have higher elastic modulus. Specimens tested in the highest speed of the experiment had on average about 10% higher elastic modulus and developed on average about 11% higher tensile strength.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJWC..9404061E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9404061E"><span id="translatedtitle">Numerical analysis of high <span class="hlt">strain</span> <span class="hlt">rate</span> failure of electro-magnetically loaded steel sheets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Erice, Borja; Mohr, Dirk</p> <p>2015-09-01</p> <p>Electro-magnetic forces provide a potentially power full means in designing dynamic experiments with active control of the loading conditions. This article deals with the development of computational models to simulate the thermo-mechanical response of electro-magnetically loaded metallic structures. The model assumes linear electromagnetic constitutive equations and time-independent electric induction to estimate the Joule heating and the Lorentz forces. The latter are then taken into account when evaluating stress equilibrium. A thermo-visco-plastic model with Johnson-Cook type of temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> dependence and combined Swift-Voce hardening is used to evaluate the material's thermo-mechanical response. As a first application, the model is used to analyse the <span class="hlt">effect</span> of electro-magnetic loading on the ductility of advanced high strength steels.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995JGR...10017991H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995JGR...10017991H"><span id="translatedtitle">The kinematics of northern South Island, New Zealand, determined from geologic <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Holt, William E.; Haines, A. J.</p> <p>1995-09-01</p> <p>Relative motions within the distributed plate boundary zone of northern South Island, New Zealand, are determined through an inversion of geologic <span class="hlt">strain</span> <span class="hlt">rate</span> estimates. The Quaternary fault slip <span class="hlt">rate</span> estimates define the shear <span class="hlt">strain</span> <span class="hlt">rates</span>, and rock uplift <span class="hlt">rates</span> provide information on the horizontal divergence <span class="hlt">rates</span>. An erosion <span class="hlt">rate</span> to rock uplift <span class="hlt">rate</span> ratio along with a crustal compensation factor is estimated in order to convert rock uplift <span class="hlt">rates</span> to horizontal divergence <span class="hlt">rates</span>. Because of the uncertainty in erosion <span class="hlt">rates</span>, horizontal divergence <span class="hlt">rates</span> σ˙ are given a large standard error of ± σ˙. The three horizontal <span class="hlt">strain</span> <span class="hlt">rate</span> components obtained from these data completely define the horizontal velocity gradient tensor. <span class="hlt">Strain</span> <span class="hlt">rate</span> distributions are matched with spline polynomial functions, which can be constrained to behave rigidly within specified regions, such as the Pacific or Australian plates. Inversion of the <span class="hlt">strain</span> <span class="hlt">rate</span> distribution, assuming uniform erosion <span class="hlt">rates</span> across the northern South Island, yields a velocity field that has small differences in both magnitude (10% larger) and direction with the NUVEL-1A plate motion model between Pacific and Australian plates. A revised <span class="hlt">strain</span> <span class="hlt">rate</span> data set, obtained from a variable erosion model in which erosion <span class="hlt">rates</span> are a linear function of the log of the average annual rainfall magnitudes, yields a velocity field with expected directions that are indistinguishable from the NUVEL-1A plate motion model between Pacific and Australian plates, but velocity magnitudes are still 10-15% higher than the plate motion model. Therefore the average values of slip <span class="hlt">rate</span> on strike-slip faults in Marlborough, required by the NUVEL-1A plate motion model, are typically close to the low end of the published range of slip values for those structures. The major strike-slip structures within the Marlborough region are accommodating 80-100% of the total plate motion between Australia and Pacific plates on northern South Island; as</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JNuM..456...54S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JNuM..456...54S"><span id="translatedtitle">Experimental characterization and modelling of UO2 behavior at high temperatures and high <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Salvo, Maxime; Sercombe, Jérôme; Ménard, Jean-Claude; Julien, Jérôme; Helfer, Thomas; Désoyer, Thierry</p> <p>2015-01-01</p> <p>This work presents an experimental characterization of uranium dioxide (UO2) in compression under Reactivity Initiated Accident (RIA) conditions. Pellet samples were tested at four temperatures (1100, 1350, 1550 and 1700 °C) and at a <span class="hlt">strain</span> <span class="hlt">rate</span> varying over 4 decades (10-4-10-3-10-2-10-1 /s). The experimental results show that the stress-<span class="hlt">strain</span> curves cannot be fitted with a unique power law as it is the case at smaller <span class="hlt">strain</span> <span class="hlt">rates</span> (10-9-10-5 /s). A <span class="hlt">strain</span>-hardening also appears in most of the tests. The microstructural observations show a pronounced evolution of the porosity at the pellet center during the tests. A hyperbolic sine model which accounts for volume variations (pore compressibility) was therefore proposed to describe the behavior of UO2 on a large range of temperatures (1100 - 1700 °C) and <span class="hlt">strain</span> <span class="hlt">rates</span> (10-9-10-1 /s). The Finite Element simulations of the compression tests lead to results (maximum stress, axial and hoop <span class="hlt">strain</span> distribution, porosity distribution) in good agreement with the measurements. The model was then assessed on a database of more than two hundred creep tests.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1994AIPC..309.1031K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994AIPC..309.1031K"><span id="translatedtitle">Flow stress and material model study at high <span class="hlt">strain</span> <span class="hlt">rate</span> and low temperature</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kandasamy, R.; Brar, N. S.</p> <p>1994-07-01</p> <p>The flow stress of M200 maraging steel, C1008 steel, and 6061-T6 aluminum at low temperatures to 123 K and at a <span class="hlt">strain</span> <span class="hlt">rate</span> of about 103 s-1 is measured using split Hopkinson bar (SHB). Liquid nitrogen is used to cool the specimen to the desired temperature. The flow stress of M200 increased to 1.93 GPa at 123 K, an increase of 22 percent compared to 1.58 GPa at room temperature. In the case of 6061-T6 aluminum the flow stress remains at about 390 MPa at temperatures in the range 293 to 123 K. For C1008 steel, the flow stress increased to 860 MPa at 123 K from its room temperature value of 610 MPa. The failure <span class="hlt">strain</span> for C1008 steel at 123 K was 0.02, compared to 0.2 at room temperature, suggesting a ductile to brittle transition. The Johnson-Cook material model constant ``m'', which accounts for temperature <span class="hlt">effect</span>, is 0.5 for C1008 at temperatures in the range 123 K to 950 K.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..SHK.Z3003B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..SHK.Z3003B"><span id="translatedtitle">Porosity evolution at high <span class="hlt">strain</span> <span class="hlt">rates</span>: atomistic simulations, dislocation analysis, and constitutive modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bringa, Eduardo; Ruestes, Carlos; Rodriguez Nieva, Joaquin; Tramontina, Diego; Tang, Yizhe; Meyers, Marc</p> <p>2015-06-01</p> <p>Mimicking shock compression experiments, our molecular dynamics simulations explore the mechanical response and plasticity <span class="hlt">effects</span> under uniaxial high <span class="hlt">strain</span> <span class="hlt">rate</span> compression (10**7/s to 10**9/s) for Au and Ta single crystals with a collection of spherical nanovoids, with a radius of 3-4 nm, resulting in an initial porosity of %-10%. Dislocation analysis was used to evaluate and quantify the evolution of plasticity. The evolution of dislocations configuration and densities were predicted and successfully compared to an analysis based on Ashby's concept of geometrically-necessary dislocations. The temperature excursion during plastic deformation was used to estimate the mobile dislocation density. The results obtained are compared with a variety of dislocation-based constitutive models. Plastic activity leads to a decrease in porosity until voids disappear completely. Based on the atomistic simulations, a densification regime was observed in all nanoporous samples studied. With these results, a new <span class="hlt">strain</span>- based porosity model for metals is proposed for simulations at the continuum scale. EB, CR and DT thank support from PICT-0092 and a SeCTyP-UNCuyo grant.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24529781','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24529781"><span id="translatedtitle">Development of a <span class="hlt">strain</span> <span class="hlt">rate</span> dependent material model of human cortical bone for computer-aided reconstruction of injury mechanisms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Asgharpour, Zahra; Zioupos, Peter; Graw, Matthias; Peldschus, Steffen</p> <p>2014-03-01</p> <p>Computer-aided methods such as finite-element simulation offer a great potential in the forensic reconstruction of injury mechanisms. Numerous studies have been performed on understanding and analysing the mechanical properties of bone and the mechanism of its fracture. Determination of the mechanical properties of bones is made on the same basis used for other structural materials. The mechanical behaviour of bones is affected by the mechanical properties of the bone material, the geometry, the loading direction and mode and of course the loading <span class="hlt">rate</span>. <span class="hlt">Strain</span> <span class="hlt">rate</span> dependency of mechanical properties of cortical bone has been well demonstrated in literature studies, but as many of these were performed on animal bones and at non-physiological <span class="hlt">strain</span> <span class="hlt">rates</span> it is questionable how these will apply in the human situations. High <span class="hlt">strain-rates</span> dominate in a lot of forensic applications in automotive crashes and assault scenarios. There is an overwhelming need to a model which can describe the complex behaviour of bone at lower <span class="hlt">strain</span> <span class="hlt">rates</span> as well as higher ones. Some attempts have been made to model the viscoelastic and viscoplastic properties of the bone at high <span class="hlt">strain</span> <span class="hlt">rates</span> using constitutive mathematical models with little demonstrated success. The main objective of the present study is to model the <span class="hlt">rate</span> dependent behaviour of the bones based on experimental data. An isotropic material model of human cortical bone with <span class="hlt">strain</span> <span class="hlt">rate</span> dependency <span class="hlt">effects</span> is implemented using the LS-DYNA material library. We employed a human finite element model called THUMS (Total Human Model for Safety), developed by Toyota R&D Labs and the Wayne State University, USA. The finite element model of the human femur is extracted from the THUMS model. Different methods have been employed to develop a <span class="hlt">strain</span> <span class="hlt">rate</span> dependent material model for the femur bone. Results of one the recent experimental studies on human femur have been employed to obtain the numerical model for cortical femur. A</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..SHK.D4005C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..SHK.D4005C"><span id="translatedtitle">Elastic precursor shock waves in tantalum at very high <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Crowhurst, Jonathan; Armstrong, Michael; Gates, Sean; Radousky, Harry; Zaug, Joseph</p> <p>2015-06-01</p> <p>We have obtained data from micron-thick tantalum films using our ultrafast laser shock platform. By measuring free surface velocity time histories at breakout, and shock wave arrival times at different film thicknesses, we have been able to estimate the dependence of particle and shock velocities on propagation distances and <span class="hlt">strain</span> <span class="hlt">rates</span>. We will show how elastic precursor shock waves depend on <span class="hlt">strain</span> <span class="hlt">rate</span> in the regime up to and above 109 s-1. We find that while elastic amplitudes are very large at very early times decay occurs rapidly as propagation distance increases. Finally we will consider the prospects for using these data to obtain the dynamic strength of tantalum at these very high <span class="hlt">strain</span> <span class="hlt">rates</span>. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344 with Laboratory directed Research and Development funding (12ERD042).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..MARA34002C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..MARA34002C"><span id="translatedtitle">Elastic precursor shock waves in tantalum at very high <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Crowhurst, Jonathan; Armstrong, Michael; Radousky, Harry; Zaug, Joseph; Gates, Sean</p> <p>2015-03-01</p> <p>We have obtained data from micron-thick tantalum films using our ultrafast laser shock platform. By measuring free surface velocity time histories at breakout, and shock wave arrival times at different film thicknesses, we have been able to estimate the dependence of particle and shock velocities on propagation distances and <span class="hlt">strain</span> <span class="hlt">rates</span>. We will show how elastic precursor shock waves depend on <span class="hlt">strain</span> <span class="hlt">rate</span> in the regime up to and above 109 s-1. We find that while elastic amplitudes are very large at very early times decay occurs rapidly as propagation distance increases. Finally we will consider the prospects for using these data to obtain the dynamic strength of tantalum at these very high <span class="hlt">strain</span> <span class="hlt">rates</span>. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344 with Laboratory directed Research and Development funding (12ERD042).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26232812','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26232812"><span id="translatedtitle">Peak <span class="hlt">strain</span> magnitudes and <span class="hlt">rates</span> in the tibia exceed greatly those in the skull: An in vivo study in a human subject.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hillam, Richard A; Goodship, Allen E; Skerry, Tim M</p> <p>2015-09-18</p> <p>Bone mass and architecture are the result of a genetically determined baseline structure, modified by the <span class="hlt">effect</span> of internal hormonal/biochemical regulators and the <span class="hlt">effect</span> of mechanical loading. Bone <span class="hlt">strain</span> is thought to drive a feedback mechanism to regulate bone formation and resorption to maintain an optimal, but not excessive mass and organisation of material at each skeletal location. Because every site in the skeleton has different functions, we have measured bone <span class="hlt">strains</span> induced by physiological and more unusual activities, at two different sites, the tibia and cranium of a young human male in vivo. During the most vigorous activities, tibial <span class="hlt">strains</span> were shown to exceed 0.2%, when ground reaction exceeded 5 times body weight. However in the skull the highest <span class="hlt">strains</span> recorded were during heading a heavy medicine/exercise ball where parietal <span class="hlt">strains</span> were up to 0.0192%. Interestingly parietal <span class="hlt">strains</span> during more physiological activities were much lower, often below 0.01%. <span class="hlt">Strains</span> during biting were not dependent upon bite force, but could be induced by facial contortions of similar appearance without contact between the teeth. <span class="hlt">Rates</span> of <span class="hlt">strain</span> change in the two sites were also very different, where peak tibial <span class="hlt">strain</span> <span class="hlt">rate</span> exceeded <span class="hlt">rate</span> in the parietal bone by more than 5 fold. These findings suggest that the skull and tibia are subject to quite different regulatory influences, as <span class="hlt">strains</span> that would be normal in the human skull would be likely to lead to profound bone loss by disuse in the long bones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4601046','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4601046"><span id="translatedtitle">Peak <span class="hlt">strain</span> magnitudes and <span class="hlt">rates</span> in the tibia exceed greatly those in the skull: An in vivo study in a human subject</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hillam, Richard A; Goodship, Allen E; Skerry, Tim M</p> <p>2015-01-01</p> <p>Bone mass and architecture are the result of a genetically determined baseline structure, modified by the <span class="hlt">effect</span> of internal hormonal/biochemical regulators and the <span class="hlt">effect</span> of mechanical loading. Bone <span class="hlt">strain</span> is thought to drive a feedback mechanism to regulate bone formation and resorption to maintain an optimal, but not excessive mass and organisation of material at each skeletal location. Because every site in the skeleton has different functions, we have measured bone <span class="hlt">strains</span> induced by physiological and more unusual activities, at two different sites, the tibia and cranium of a young human male in vivo. During the most vigorous activities, tibial <span class="hlt">strains</span> were shown to exceed 0.2%, when ground reaction exceeded 5 times body weight. However in the skull the highest <span class="hlt">strains</span> recorded were during heading a heavy medicine/exercise ball where parietal <span class="hlt">strains</span> were up to 0.0192%. Interestingly parietal <span class="hlt">strains</span> during more physiological activities were much lower, often below 0.01%. <span class="hlt">Strains</span> during biting were not dependent upon bite force, but could be induced by facial contortions of similar appearance without contact between the teeth. <span class="hlt">Rates</span> of <span class="hlt">strain</span> change in the two sites were also very different, where peak tibial <span class="hlt">strain</span> <span class="hlt">rate</span> exceeded <span class="hlt">rate</span> in the parietal bone by more than 5 fold. These findings suggest that the skull and tibia are subject to quite different regulatory influences, as <span class="hlt">strains</span> that would be normal in the human skull would be likely to lead to profound bone loss by disuse in the long bones. PMID:26232812</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoJI.200.1483W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoJI.200.1483W"><span id="translatedtitle">Quantifying velocity, <span class="hlt">strain</span> <span class="hlt">rate</span> and stress distribution in coalescing salt sheets for safer drilling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Weijermars, R.; van Harmelen, A.</p> <p>2015-03-01</p> <p>Reaching sub-salt hydrocarbon targets in the deeper part of the Gulf of Mexico requires drilling through a salt canopy. The suture zones in the salt canopy are potential drilling hazards due to anomalous pressure behaviour of entrapped sediments. The Pólya vector field of coalescing salt sheets inside the canopy is used to explain suture formation and distinguish between upright and inclined suture contacts. Our analytical models, based on complex potentials, provide exact solutions for multiple source flows as they compete for space when spreading into the viscous continuum of the salt canopy. The velocity gradient tensor yields the <span class="hlt">strain</span> <span class="hlt">rate</span> tensor, which is used to map the principal <span class="hlt">strain</span> <span class="hlt">rate</span> magnitude inside the canopy. Quantification of one of the principal <span class="hlt">strain</span> <span class="hlt">rates</span> is sufficient because the plane deformation assumption ensures the two principal <span class="hlt">strain</span> <span class="hlt">rates</span> are equal in magnitude (but of opposite sign); the third principal dimension can have neither <span class="hlt">strain</span> nor deviatoric stress. Visualization of the locations where the principal stress vanishes or peaks (with highs and lows) is useful for pre-drilling plans because such peaks must be avoided and the stress-free locations provide the safer drilling sites. A case study-of the Walker Ridge region-demonstrates the practical application of our new method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26318572','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26318572"><span id="translatedtitle"><span class="hlt">Strain-rate</span> and temperature dependent material properties of Agar and Gellan Gum used in biomedical applications.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schiavi, Alessandro; Cuccaro, Rugiada; Troia, Adriano</p> <p>2016-01-01</p> <p>Agar and Gellan Gum are biocompatible polymers extensively used in several fields of tissue engineering research (e.g. tissue replacement, tissue support, tissue mimicking), due to their mechanical behaviour <span class="hlt">effectively</span> representative of actual biological tissues. Since mechanical properties of artificial tissues are related to biocompatibility and functionality of medical implants and significantly influence adhesion, growth and differentiation of cells in tissue-engineering scaffolds, an accurate characterization of Young׳s modulus and relaxation time processes is needed. In this study, the <span class="hlt">strain-rate</span> and temperature dependent material properties of Agarose and one among the numerous kind of Gellan Gum commercially available, known as Phytagel(®), have been investigated. Nine hydrogel samples have been realized with different mechanical properties: the first one Agar-based as a reference material, the further eight samples Gellan Gum based in which the <span class="hlt">effect</span> of dispersed solid particles like kieselguhr and SiC, as enhancing mechanical properties factors, have been investigated as a function of concentration. Stress-<span class="hlt">strain</span> has been investigated in compression and relaxation time has been evaluated by means of the Kohlrausch-Williams-Watts time decay function. Mechanical properties have been measured as a function of temperature between 20 °C and 35 °C and at different <span class="hlt">strain</span> <span class="hlt">rates</span>, from ~10(-3)s(-1) and ~10(-2)s(-1) (or deformation <span class="hlt">rate</span> from ~0.01 mms(-1) to ~0.1 mms(-1)). From experimental data, the combined temperature and <span class="hlt">strain-rate</span> dependence of hydrogels Young׳s modulus is determined on the basis of a constitutive model. In addition to a dependence of Young׳s modulus on temperature, a remarkable influence of <span class="hlt">strain-rate</span> has been observed, especially in the sample containing solid particles; in same ranges of temperature and <span class="hlt">strain-rate</span>, also relaxation time variations have been monitored in order to identify a possible dependence of damping</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD0878153','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD0878153"><span id="translatedtitle">The <span class="hlt">Strain</span>-Potential <span class="hlt">Effect</span> of Silver Iodide.</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p></p> <p>SILVER COMPOUNDS, SEEBECK <span class="hlt">EFFECT</span> ), IODIDES, IMPURITIES, CONCENTRATION(CHEMISTRY), IONS, IONIZATION, IONIZATION POTENTIALS, ELECTRODES, ELECTROLYTES, INTERFACES, MOBILE, DISLOCATIONS, DEFORMATION, CRYSTAL DEFECTS, ELECTRICAL CONDUCTIVITY, SENSITIVITY, <span class="hlt">STRAIN</span> GAGES, <span class="hlt">STRAIN</span>(MECHANICS).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA258802','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA258802"><span id="translatedtitle">High <span class="hlt">Strain-Rate</span> Compression Testing of a Ceramic Matrix Composite</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>1992-12-01</p> <p>AD-A25 8 802 HIGH <span class="hlt">STRAIN-RATE</span> COMPRESSION TESTING OF A CERAMIC MATRIX COMPOSITE AcQQ3L- For• by James M. Parker Avwii;a11itv Codes Si~ve i!nnd/or...Williams for their hands-on help in every aspect of the testing and analysis. Finally, you can’t have a dance without music and for this dance, the music...1 2 HIGH <span class="hlt">STRAIN-RATE</span> COMPRESSION TESTING OF CERAMIC MATRIX COMPOSITES ........ ........... 3 3 DESCRIPTION OF LANXIDE® CERAMIC MATRIX COMPOSITE</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/175427','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/175427"><span id="translatedtitle">Implementation of <span class="hlt">strain</span> <span class="hlt">rate</span> sensitive material properties into impact related problems</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Laubscher, R.F.; Merwe, P. van der</p> <p>1995-12-31</p> <p><span class="hlt">Strain</span> <span class="hlt">rate</span> sensitivity is discussed in general. A general <span class="hlt">strain</span> <span class="hlt">rate</span> sensitive constitutive model is then derived with a yield criterion for an isotropic hardening material incorporating a modified version of the Cowper Symonds equation. Experimental data for 10 different metals ranging from carbon steels to titanium alloys are fitted to this constitutive model. It is shown that with this relatively simple model a good agreement can be achieved between the constitutive model and the experimental data for most metals. The manner in which this constitutive model may be used in design is discussed along with its incorporation into numerical methods such as finite elements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJWC..9401030F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9401030F"><span id="translatedtitle">Energy absorption at high <span class="hlt">strain</span> <span class="hlt">rate</span> of glass fiber reinforced mortars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fenu, Luigi; Forni, Daniele; Cadoni, Ezio</p> <p>2015-09-01</p> <p>In this paper, the dynamic behaviour of cement mortars reinforced with glass fibers was studied. The influence of the addition of glass fibers on energy absorption and tensile strength at high <span class="hlt">strain-rate</span> was investigated. Static tests in compression, in tension and in bending were first performed. Dynamic tests by means of a Modified Hopkinson Bar were then carried out in order to investigate how glass fibers affected energy absorption and tensile strength at high <span class="hlt">strain-rate</span> of the fiber reinforced mortar. The Dynamic Increase Factor (DIF) was finally evaluated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhA.122..794J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhA.122..794J"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> sensitivity of nanoindentation creep in an AlCoCrFeNi high-entropy alloy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiao, Z. M.; Wang, Z. H.; Wu, R. F.; Qiao, J. W.</p> <p>2016-09-01</p> <p>Creep behaviors of an AlCoCrFeNi high-entropy alloy with the body-centered cubic structure were investigated by nanoindentation. The enhanced <span class="hlt">strain</span> gradient induced by higher <span class="hlt">strain</span> <span class="hlt">rate</span> leads to decreased <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity during creep process. The present alloy exhibits excellent creep resistance, mainly due to its large entropy of mixing and highly distorted lattice structure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12465851','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12465851"><span id="translatedtitle">Short-term changes in consumption and oviposition <span class="hlt">rates</span> of Neoseiulus californicus <span class="hlt">strains</span> (Acari: Phytoseiidae) after a diet shift.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Castagnoli, M; Simoni, S; Nachman, G</p> <p>2001-01-01</p> <p>Short-term <span class="hlt">effects</span> on consumption and oviposition <span class="hlt">rates</span> of four <span class="hlt">strains</span> of Neoseiulus californicus (McGregor) after a diet shift were evaluated. The new feeding conditions experienced by the predators were six fixed densities of eggs or protonymphs of Tetranychus urticae Koch placed on excised strawberry leaflet discs and maintained under laboratory conditions (25 +/- 1 degrees C, 75-85% RH, 16L: 8D). The observations were made on the first and the fifth day of the experiment. The phytoseiids came from three long-term mass-reared <span class="hlt">strains</span> fed on T. urticae, Dermatophagoidesfarinae Hughes, or Quercus spp. pollen, respectively. The fourth <span class="hlt">strain</span> was collected directly in a strawberry field. Time since diet transfer can be added to the factors (i.e. feeding history and prey density) already known to affect the functional and numerical responses of N. californicus, both when it feeds on prey eggs and protonymphs. If consumption <span class="hlt">rates</span> were averaged over all <span class="hlt">strains</span> and densities, 9.04 and 11.41 eggs, and 6.97 and 6.48 protonymphs were consumed on the first and the fifth day, respectively. If the same was done for oviposition <span class="hlt">rates</span>, predators feeding on eggs produced 1.46 and 2.36 eggs/female/day, whereas predators feeding on protonymphs produced 1.35 and 2.29 eggs/female/day. Time had the greatest impact on the functional response of the <span class="hlt">strain</span> that had previously fed on tetranychids, while an <span class="hlt">effect</span> of time on the numerical response was detectable in all <span class="hlt">strains</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20120008792&hterms=joint&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Djoint','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20120008792&hterms=joint&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Djoint"><span id="translatedtitle">Adhesive-Bonded Composite Joint Analysis with Delaminated Surface Ply Using <span class="hlt">Strain</span>-Energy Release <span class="hlt">Rate</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chadegani, Alireza; Yang, Chihdar; Smeltzer, Stanley S. III</p> <p>2012-01-01</p> <p>This paper presents an analytical model to determine the <span class="hlt">strain</span> energy release <span class="hlt">rate</span> due to an interlaminar crack of the surface ply in adhesively bonded composite joints subjected to axial tension. Single-lap shear-joint standard test specimen geometry with thick bondline is followed for model development. The field equations are formulated by using the first-order shear-deformation theory in laminated plates together with kinematics relations and force equilibrium conditions. The stress distributions for the adherends and adhesive are determined after the appropriate boundary and loading conditions are applied and the equations for the field displacements are solved. The system of second-order differential equations is solved to using the symbolic computation tool Maple 9.52 to provide displacements fields. The equivalent forces at the tip of the prescribed interlaminar crack are obtained based on interlaminar stress distributions. The <span class="hlt">strain</span> energy release <span class="hlt">rate</span> of the crack is then determined by using the crack closure method. Finite element analyses using the J integral as well as the crack closure method are performed to verify the developed analytical model. It has been shown that the results using the analytical method correlate well with the results from the finite element analyses. An attempt is made to predict the failure loads of the joints based on limited test data from the literature. The <span class="hlt">effectiveness</span> of the inclusion of bondline thickness is justified when compared with the results obtained from the previous model in which a thin bondline and uniform adhesive stresses through the bondline thickness are assumed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JAP...109j3512G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JAP...109j3512G"><span id="translatedtitle">A method for intermediate <span class="hlt">strain</span> <span class="hlt">rate</span> compression testing and study of compressive failure mechanism of Mg-Al-Zn alloy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gupta, Nikhil; Luong, Dung D.; Rohatgi, Pradeep K.</p> <p>2011-05-01</p> <p>Obtaining meaningful information from the test results is a challenge in the split-Hopkinson pressure bar (SHPB) test method if the specimen does not fail during the test. Although SHPB method is now widely used for high <span class="hlt">strain</span> <span class="hlt">rate</span> testing, this limitation has made it difficult to use it for characterization of materials in the intermediate <span class="hlt">strain</span> <span class="hlt">rate</span> range (typically 10-1000 s-1). In the present work, a method is developed to characterize materials in the intermediate <span class="hlt">strain</span> <span class="hlt">rate</span> range using SHPB setup. In this method, the specimen is repeatedly tested under compression at a given <span class="hlt">strain</span> <span class="hlt">rate</span> until failure is achieved. The stress-<span class="hlt">strain</span> graphs obtained from each test cycle are used to plot the master stress-<span class="hlt">strain</span> graph for that <span class="hlt">strain</span> <span class="hlt">rate</span>. This method is used to study the <span class="hlt">strain</span> <span class="hlt">rate</span> dependence of compressive response of a Mg-Al-Zn alloy in the intermediate <span class="hlt">strain</span> <span class="hlt">rate</span> range. A remarkable difference is observed in the failure mechanism of the alloy under quasi-static and intermediate <span class="hlt">strain</span> <span class="hlt">rate</span> compression. Matrix cracking is the main failure mechanism under quasi-static compression, whereas shattering of intermetallic precipitates, along with plastic deformation of the matrix, is discovered to become prominent as the <span class="hlt">strain</span> <span class="hlt">rate</span> is increased.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27553875','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27553875"><span id="translatedtitle">Estimation of the HIV-1 backward mutation <span class="hlt">rate</span> from transmitted drug-resistant <span class="hlt">strains</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kitayimbwa, J M; Mugisha, J Y T; Saenz, R A</p> <p>2016-12-01</p> <p>One of the serious threats facing the administration of antiretroviral therapy to human immunodeficiency virus (HIV-1) infected patients is the reported increasing prevalence of transmitted drug resistance. However, given that HIV-1 drug-resistant <span class="hlt">strains</span> are often less fit than the wild-type <span class="hlt">strains</span>, it is expected that drug-resistant <span class="hlt">strains</span> that are present during the primary phase of the HIV-1 infection are replaced by the fitter wild-type <span class="hlt">strains</span>. This replacement of HIV-1 resistant mutations involves the emergence of wild-type <span class="hlt">strains</span> by a process of backward mutation. How quickly the replacement happens is dependent on the class of HIV-1 mutation group. We estimate the backward mutation <span class="hlt">rates</span> and relative fitness of various mutational groups known to confer HIV-1 drug resistance. We do this by fitting a stochastic model to data for individuals who were originally infected by an HIV-1 <span class="hlt">strain</span> carrying any one of the known drug resistance-conferring mutations and observed over a period of time to see whether the resistant <span class="hlt">strain</span> is replaced. To do this, we seek a distribution, generated from simulations of the stochastic model, that best describes the observed (clinical data) replacement times of a given mutation. We found that Lamivudine/Emtricitabine-associated mutations have a distinctly higher, backward mutation <span class="hlt">rate</span> and low relative fitness compared to the other classes (as has been reported before) while protease inhibitors-associated mutations have a slower backward mutation <span class="hlt">rate</span> and high relative fitness. For the other mutation classes, we found more uncertainty in their estimates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFM.T31C0472S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFM.T31C0472S"><span id="translatedtitle">Measuring Local <span class="hlt">Strain</span> <span class="hlt">Rates</span> In Ductile Shear Zones: A New Approach From Deformed Syntectonic Dykes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sassier, C.; Leloup, P.; Rubatto, D.; Galland, O.; Yue, Y.; Ding, L.</p> <p>2006-12-01</p> <p>At the Earth surface, deformation is mostly localized in fault zones in between tectonic plates. In the upper crust, the deformation is brittle and the faults are narrow and produce earthquakes. In contrast, deformation in the lower ductile crust results in larger shear zones. While it is relatively easy to measure in situ deformation <span class="hlt">rates</span> at the surface using for example GPS data, it is more difficult to determinate in situ values of <span class="hlt">strain</span> <span class="hlt">rate</span> in the ductile crust. Such <span class="hlt">strain</span> <span class="hlt">rates</span> can only be estimated in paleo-shear zones. Various methods have been used to assess paleo-<span class="hlt">strain</span> <span class="hlt">rates</span> in paleo-shear zones. For instance, cooling and/or decompression <span class="hlt">rates</span> associated with assumptions on geothermic gradients and shear zone geometry can lead to such estimates. Another way to estimate <span class="hlt">strain</span> <span class="hlt">rates</span> is the integration of paleo-stress measurements in a power flow law. But these methods are indirect and imply strong assumptions. Dating of helicitic garnets or syntectonic fibres are more direct estimates. However these last techniques have been only applied in zones of low deformation and not in major shear zones. We propose a new direct method to measure local <span class="hlt">strain</span> <span class="hlt">rates</span> in major ductile shear zones from syntectonic dykes by coupling quantification of deformation and geochronology. We test our method in a major shear zone in a well constrained tectonic setting: the Ailao-Shan - Red River Shear Zone (ASRRsz) located in SE Asia. For this 10 km wide shear zone, large-scale fault <span class="hlt">rates</span>, determined in three independent ways, imply <span class="hlt">strain</span> <span class="hlt">rates</span> between 1.17×10^{-13 s-1 and 1.52×10^{-13 s-1 between 35 and 16 Ma. Our study focused on one outcrop where different generations of syntectonic dykes are observed. First, we quantified the minimum shear <span class="hlt">strain</span> γ for each dyke using several methods: (1) by measuring the stretching of dykes with a surface restoration method (2) by measuring the final angle of the dykes with respect to the shear direction and (3) by combining the two</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013APS..SHK.E1004R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APS..SHK.E1004R"><span id="translatedtitle">Solid state Rayleigh-Taylor measurements in Ta and V at high pressures and <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Remington, Bruce; Park, Hye-Sook; Cavallo, Robert; Prisbrey, Shon; Rudd, Robert; Plechaty, Chris; Wehrenberg, Chris; Maddox, Brian; Kostinski, Natalie; Terry, Matthew; Huntington, C.</p> <p>2013-06-01</p> <p>We will report on Rayleigh-Taylor (RT) strength experiments in solid-state driven foils of vanadium and tantalum at high <span class="hlt">strain</span> <span class="hlt">rates</span> (~1.e7 1/s) and high pressures (~1 Mbar), where softening (a decrease in strength) is observed when the <span class="hlt">strains</span> get large. When the single-mode RT bubble penetration in this plastic flow regime reaches ~20-30% of the initial foil thickness, the inferred high strength in the foils starts to drop. In the extreme, this drop in strength may be an indication of incipient failure. We will discuss the similarities and differences between the observed softening in the V-RT and Ta-RT experiments, and consider the implications for future planned experiments on the National Ignition Facility (NIF) at higher pressures (~5 Mbar), but similar <span class="hlt">strain</span> <span class="hlt">rates</span>. Prepared by LLNL under Contract DE-AC52-07NA27344.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1793j0007R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1793j0007R"><span id="translatedtitle">Deformation and failure of OFHC copper under high <span class="hlt">strain</span> <span class="hlt">rate</span> shear compression</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruggiero, Andrew; Testa, Gabriel; Bonora, Nicola; Iannitti, Gianluca; Persechino, Italo; Colliander, Magnus Hörnqvist</p> <p>2017-01-01</p> <p>Hat-shaped specimen geometries were developed to generate high <span class="hlt">strain</span>, high-<span class="hlt">strain-rates</span> deformation under prescribed conditions. These geometries offer also the possibility to investigate the occurrence of ductile rupture under low or negative stress triaxiality, where most failure models fail. In this work, three tophat geometries were designed, by means of extensive numerical simulation, to obtain desired stress triaxiality values within the shear region that develops across the ligament. Material failure was simulated using the Continuum Damage Model (CDM) formulation with a unilateral condition for damage accumulation and validated by comparing with quasi-static and high <span class="hlt">strain</span> <span class="hlt">rate</span> compression tests results on OFHC copper. Preliminary results seem to indicate that ductile tearing initiates at the specimen corner location where positive stress triaxiality occurs because of local rotation and eventually propagates along the ligament.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JNuM..473....1S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JNuM..473....1S"><span id="translatedtitle">High <span class="hlt">strain</span> <span class="hlt">rate</span> behavior of alloy 800H at high temperatures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shafiei, E.</p> <p>2016-05-01</p> <p>In this paper, a new model using linear estimation of <span class="hlt">strain</span> hardening <span class="hlt">rate</span> vs. stress, has been developed to predict dynamic behavior of alloy 800H at high temperatures. In order to prove the accuracy and competency of the presented model, Johnson-Cook model pertaining modeling of flow stress curves was used. Evaluation of mean error of flow stress at deformation temperatures from 850 °C to 1050 °C and at <span class="hlt">strain</span> <span class="hlt">rates</span> of 5 S-1 to 20 S-1 indicates that the predicted results are in a good agreement with experimentally measured ones. This analysis has been done for the stress-<span class="hlt">strain</span> curves under hot working condition for alloy 800H. However, this model is not dependent on the type of material and can be extended for any similar conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4750461','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4750461"><span id="translatedtitle">Mechanical Characterization of Immature Porcine Brainstem in Tension at Dynamic <span class="hlt">Strain</span> <span class="hlt">Rates</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhao, Hui; Yin, Zhiyong; Li, Kui; Liao, Zhikang; Xiang, Hongyi; Zhu, Feng</p> <p>2016-01-01</p> <p>Background Many brain injury cases involve pediatric road traffic accidents, and among these, brainstem injury causes disastrous outcomes. A thorough understanding of the tensile characterization of immature brainstem tissue is crucial in modeling traumatic brain injury sustained by children, but limited experimental data in tension is available for the immature brain tissue at dynamic <span class="hlt">strain</span> <span class="hlt">rates</span>. Material/Methods We harvested brainstem tissue from immature pigs (about 4 weeks old, and at a developmental stage similar to that of human toddlers) as a byproduct from a local slaughter house and very carefully prepared the samples. Tensile tests were performed on specimens at dynamic <span class="hlt">strain</span> <span class="hlt">rates</span> of 2/s, 20/s, and 100/s using a biological material instrument. The constitutive models, Fung, Ogden, Gent, and exponential function, for immature brainstem tissue material property were developed for the recorded experimental data using OriginPro® 8.0 software. The t test was performed for infinitesimal shear modules. Results The curves of stress-versus-stretch ratio were convex in shape, and inflection points were found in all the test groups at the <span class="hlt">strain</span> of about 2.5%. The average Lagrange stress of the immature brainstem specimen at the 30% <span class="hlt">strain</span> at the <span class="hlt">strain</span> <span class="hlt">rates</span> of 2, 20, and 100/s was 273±114, 515±107, and 1121±197 Pa, respectively. The adjusted R-Square (R2) of Fung, Ogden, Gent, and exponential model was 0.820≤R2≤0.933, 0.774≤R2≤0.940, 0.650≤R2≤0.922, and 0.852≤R2≤0.981, respectively. The infinitesimal shear modulus of the <span class="hlt">strain</span> energy functions showed a significant association with the <span class="hlt">strain</span> <span class="hlt">rate</span> (p<0.01). Conclusions The immature brainstem is a <span class="hlt">rate</span>-dependent material in dynamic tensile tests, and the tissue becomes stiffer with increased <span class="hlt">strain</span> <span class="hlt">rate</span>. The reported results may be useful in the study of brain injuries in children who sustain injuries in road traffic accidents. Further research in more detail should be performed in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24031783','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24031783"><span id="translatedtitle"><span class="hlt">Effect</span> of ph and salt gradient on the autolysis of Lactococcus lactis <span class="hlt">strains</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ramírez-Nuñez, Jennifer; Romero-Medrano, Ruth; Nevárez-Moorillón, Guadalupe V; Gutiérrez-Méndez, Néstor</p> <p>2011-10-01</p> <p>The aim of this work was to assess in-vitro the <span class="hlt">effect</span> of pH and salt concentration on the <span class="hlt">rate</span> of autolysis in L. lactis <span class="hlt">strains</span>. Regardless autolysis variation among L. lactis <span class="hlt">strains</span>, statistical analysis showed evidence of increase of autolysis in L. lactis under low salt concentration and acidic conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017RSPTA.37560168L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017RSPTA.37560168L"><span id="translatedtitle">Use of simulated experiments for material characterization of brittle materials subjected to high <span class="hlt">strain</span> <span class="hlt">rate</span> dynamic tension</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lukić, Bratislav; Saletti, Dominique; Forquin, Pascal</p> <p>2017-01-01</p> <p>Rapid progress in ultra-high-speed imaging has allowed material properties to be studied at high <span class="hlt">strain</span> <span class="hlt">rates</span> by applying full-field measurements and inverse identification methods. Nevertheless, the sensitivity of these techniques still requires a better understanding, since various extrinsic factors present during an actual experiment make it difficult to separate different sources of errors that can significantly affect the quality of the identified results. This study presents a methodology using simulated experiments to investigate the accuracy of the so-called spalling technique (used to study tensile properties of concrete subjected to high <span class="hlt">strain</span> <span class="hlt">rates</span>) by numerically simulating the entire identification process. The experimental technique uses the virtual fields method and the grid method. The methodology consists of reproducing the recording process of an ultra-high-speed camera by generating sequences of synthetically deformed images of a sample surface, which are then analysed using the standard tools. The investigation of the uncertainty of the identified parameters, such as Young's modulus along with the stress-<span class="hlt">strain</span> constitutive response, is addressed by introducing the most significant user-dependent parameters (i.e. acquisition speed, camera dynamic range, grid sampling, blurring), proving that the used technique can be an <span class="hlt">effective</span> tool for error investigation. This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high <span class="hlt">strain</span> <span class="hlt">rates</span>'.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4123638','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4123638"><span id="translatedtitle"><span class="hlt">Effect</span> of Local Tidal Lung <span class="hlt">Strain</span> on Inflammation in Normal and Lipopolysaccharide-Exposed Sheep</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wellman, Tyler J.; Winkler, Tilo; Costa, Eduardo L.V.; Musch, Guido; Harris, R. Scott; Zheng, Hui; Venegas, Jose G.; Vidal Melo, Marcos F.</p> <p>2014-01-01</p> <p>Objective Regional tidal lung <span class="hlt">strain</span> may trigger local inflammation during mechanical ventilation, particularly when additional inflammatory stimuli are present. However, it is unclear whether inflammation develops proportionally to tidal <span class="hlt">strain</span> or only above a threshold. We aimed to: (1) assess the relationship between regional tidal <span class="hlt">strain</span> and local inflammation in vivo during the early stages of lung injury in lungs with regional aeration heterogeneity comparable to that of humans; and (2) determine how this <span class="hlt">strain</span>-inflammation relationship is affected by endotoxemia. Design Interventional animal study. Setting Experimental laboratory and positron emission tomography (PET) facility. Subjects Eighteen 2–4-month-old sheep. Interventions Three groups of sheep (n=6) were mechanically ventilated to the same plateau pressure (30–32 cmH2O) with High-<span class="hlt">Strain</span> (VT=18.2±6.5 ml/kg, PEEP=0), High-<span class="hlt">Strain</span> plus intravenous lipopolysaccharide (LPS) (VT=18.4±4.2 ml/kg, PEEP=0), or Low-<span class="hlt">Strain</span> plus LPS (VT=8.1±0.2 ml/kg, PEEP=17±3 cmH2O). At baseline, we acquired respiratory-gated PET scans of inhaled 13NN to measure tidal <span class="hlt">strain</span> from end-expiratory and end-inspiratory images in six regions of interest (ROIs). After 3 hours of mechanical ventilation, dynamic [18F]fluoro-2-deoxy-D-glucose (18F-FDG) scans were acquired to quantify metabolic activation, indicating local neutrophilic inflammation, in the same ROIs. Measurements and Main Results Baseline regional tidal <span class="hlt">strain</span> had a significant <span class="hlt">effect</span> on 18F-FDG net uptake <span class="hlt">rate</span> Ki in High-<span class="hlt">Strain</span> LPS (p=0.036) and on phosphorylation <span class="hlt">rate</span> k3 in High-<span class="hlt">Strain</span> (p=0.027) and High-<span class="hlt">Strain</span> LPS (p=0.004). LPS exposure increased the k3-tidal <span class="hlt">strain</span> slope 3-fold (p=0.009), without significant lung edema. The Low-<span class="hlt">Strain</span> LPS group showed lower baseline regional tidal <span class="hlt">strain</span> (0.33±0.17) than High-<span class="hlt">Strain</span> (1.21±0.62; p<0.001) or High-<span class="hlt">Strain</span> LPS (1.26±0.44; p<0.001), and lower k3 (p<0.001) and Ki (p<0.05) than High-<span class="hlt">Strain</span> LPS. Conclusions Local</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27575211','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27575211"><span id="translatedtitle">Influence of compressibility on the Lagrangian statistics of vorticity-<span class="hlt">strain-rate</span> interactions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Danish, Mohammad; Sinha, Sawan Suman; Srinivasan, Balaji</p> <p>2016-07-01</p> <p>The objective of this study is to investigate the influence of compressibility on Lagrangian statistics of vorticity and <span class="hlt">strain-rate</span> interactions. The Lagrangian statistics are extracted from "almost" time-continuous data sets of direct numerical simulations of compressible decaying isotropic turbulence by employing a cubic spline-based Lagrangian particle tracker. We study the influence of compressibility on Lagrangian statistics of alignment in terms of compressibility parameters-turbulent Mach number, normalized dilatation-<span class="hlt">rate</span>, and flow topology. In comparison to incompressible turbulence, we observe that the presence of compressibility in a flow field weakens the alignment tendency of vorticity toward the largest <span class="hlt">strain-rate</span> eigenvector. Based on the Lagrangian statistics of alignment conditioned on dilatation and topology, we find that the weakened tendency of alignment observed in compressible turbulence is because of a special group of fluid particles that have an initially negligible dilatation-<span class="hlt">rate</span> and are associated with stable-focus-stretching topology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.T42C..07B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.T42C..07B"><span id="translatedtitle">A Micromechanics Based Constitutive Model For Brittle Failure at High <span class="hlt">Strain</span> <span class="hlt">Rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bhat, H. S.; Rosakis, A.; Sammis, C. G.</p> <p>2011-12-01</p> <p>The micromechanical damage mechanics formulated by Ashby and Sammis [1] and generalized by Desh- pande and Evans [2] has been extended to allow for a more generalized stress state and to incorporate an ex- perimentally motivated new crack growth (damage evo- lution) law that is valid over a wide range of loading <span class="hlt">rates</span>. This law is sensitive to both the crack tip stress field and its time derivative. Incorporating this feature produces <span class="hlt">strain-rate</span> sensitivity in the constitutive re- sponse. The model is also experimentally verified by predicting the failure strength of Dionysus-Pentelicon marble over <span class="hlt">strain</span> <span class="hlt">rates</span> ranging from ˜ 10-6 to 103 s-1. Model parameters determined from from quasi-static experiments were used to predict the failure strength at higher loading <span class="hlt">rates</span>. Agreement with experimental results was excellent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25174668','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25174668"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> hardening: a hidden but critical mechanism for biological composites?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chintapalli, Ravi Kiran; Breton, Stephanie; Dastjerdi, Ahmad Khayer; Barthelat, Francois</p> <p>2014-12-01</p> <p>Natural materials such as nacre, bone, collagen and spider silk boast unusual combinations of stiffness, strength and toughness. Behind this performance is a staggered microstructure, which consists of stiff and elongated inclusions embedded in a softer and more deformable matrix. The micromechanics of deformation and failure associated with this microstructure are now well understood at the "unit cell" level, the smallest representative volume for this type of material. However, these mechanisms only translate to high performance if they propagate throughout large volumes, an important condition which is often overlooked. Here we present, for the first time, a model which captures the conditions for either spreading of deformations or localization, which determines whether a staggered composite is brittle or deformable at the macroscale. The macroscopic failure <span class="hlt">strain</span> for the material was calculated as function of the viscoplastic properties of the interfaces and the severity of the defect. As expected, larger <span class="hlt">strains</span> at failure can be achieved when smaller defects are present within the material, or with more <span class="hlt">strain</span> hardening at the interface. The model also shows that <span class="hlt">strain</span> <span class="hlt">rate</span> hardening is a powerful source of large deformations for the material as well, a result we confirmed and validated with tensile experiments on glass-polydimethylsiloxane (PDMS) nacre-like staggered composites. An important implication is that natural materials, largely made of <span class="hlt">rate</span>-dependent materials, could rely on <span class="hlt">strain</span> <span class="hlt">rate</span> hardening to tolerate initial defects and damage to maintain their functionality. <span class="hlt">Strain</span> <span class="hlt">rate</span> hardening could also be harnessed and optimized in bio-inspired composites in order to maximize their overall performance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/841358','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/841358"><span id="translatedtitle">TRP 9904 - Constitutive Behavior of High Strength Multiphase Sheel Steel Under High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Deformation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>David Matlock; John Speer</p> <p>2005-03-31</p> <p>The focus of the research project was to systematically assess the <span class="hlt">strain</span> <span class="hlt">rate</span> dependence of strengthening mechanisms in new advanced high strength sheet steels. Data were obtained on specially designed and produced Duel Phase and TRIP steels and compared to the properties of automotive steels currently in use.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017RSPTA.37560167Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017RSPTA.37560167Z"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> sensitivity of the tensile strength of two silicon carbides: experimental evidence and micromechanical modelling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zinszner, Jean-Luc; Erzar, Benjamin; Forquin, Pascal</p> <p>2017-01-01</p> <p>Ceramic materials are commonly used to design multi-layer armour systems thanks to their favourable physical and mechanical properties. However, during an impact event, fragmentation of the ceramic plate inevitably occurs due to its inherent brittleness under tensile loading. Consequently, an accurate model of the fragmentation process is necessary in order to achieve an optimum design for a desired armour configuration. In this work, shockless spalling tests have been performed on two silicon carbide grades at <span class="hlt">strain</span> <span class="hlt">rates</span> ranging from 103 to 104 s-1 using a high-pulsed power generator. These spalling tests characterize the tensile strength <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity of each ceramic grade. The microstructural properties of the ceramics appear to play an important role on the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity and on the dynamic tensile strength. Moreover, this experimental configuration allows for recovering damaged, but unbroken specimens, giving unique insight on the fragmentation process initiated in the ceramics. All the collected data have been compared with corresponding results of numerical simulations performed using the Denoual-Forquin-Hild anisotropic damage model. Good agreement is observed between numerical simulations and experimental data in terms of free surface velocity, size and location of the damaged zones along with crack density in these damaged zones. This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high <span class="hlt">strain</span> <span class="hlt">rates</span>'.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJWC..9403006P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9403006P"><span id="translatedtitle">Intermediate <span class="hlt">strain</span> <span class="hlt">rate</span> behaviour of cancellous bone: Links between microstructural and mechanical properties</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prot, Marianne; Cloete, Trevor; Saletti, Dominique; Laporte, Sebastien</p> <p>2015-09-01</p> <p>Relationships between the micro-architecture description of cancellous bone, obtained from medical imaging, and its mechanical properties can be used to assess the compression fracture risk at high and low <span class="hlt">strain</span> <span class="hlt">rate</span>. This study extends the rupture prediction to the intermediate <span class="hlt">strain</span> <span class="hlt">rate</span> regime. The micro-architecture description was obtained with a CT-scan, for which geometry, topology, connectivity and anisotropy parameters were computed and compared to mechanical identified parameters in order to confirm their usefulness. Three <span class="hlt">strain</span> <span class="hlt">rates</span> were investigated: 1/s, 10/s and 100/s using two different devices: a Wedge-Bar apparatus and a conventional split Hopkinson pressure bar implemented with a Cone-in-Tube striker and a tandem momentum trap. This setup provides a constant <span class="hlt">strain</span> <span class="hlt">rate</span> loading with routine specimen recovery allowing the fracture zone to be investigated. This study reveals that a transition in the response behaviour occurred in the intermediate regime and confirms the significant porous organization influence through the regimes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27956504','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27956504"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> sensitivity of the tensile strength of two silicon carbides: experimental evidence and micromechanical modelling.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zinszner, Jean-Luc; Erzar, Benjamin; Forquin, Pascal</p> <p>2017-01-28</p> <p>Ceramic materials are commonly used to design multi-layer armour systems thanks to their favourable physical and mechanical properties. However, during an impact event, fragmentation of the ceramic plate inevitably occurs due to its inherent brittleness under tensile loading. Consequently, an accurate model of the fragmentation process is necessary in order to achieve an optimum design for a desired armour configuration. In this work, shockless spalling tests have been performed on two silicon carbide grades at <span class="hlt">strain</span> <span class="hlt">rates</span> ranging from 10(3) to 10(4) s(-1) using a high-pulsed power generator. These spalling tests characterize the tensile strength <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity of each ceramic grade. The microstructural properties of the ceramics appear to play an important role on the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity and on the dynamic tensile strength. Moreover, this experimental configuration allows for recovering damaged, but unbroken specimens, giving unique insight on the fragmentation process initiated in the ceramics. All the collected data have been compared with corresponding results of numerical simulations performed using the Denoual-Forquin-Hild anisotropic damage model. Good agreement is observed between numerical simulations and experimental data in terms of free surface velocity, size and location of the damaged zones along with crack density in these damaged zones.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high <span class="hlt">strain</span> <span class="hlt">rates</span>'.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApPhL.109q4103P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhL.109q4103P"><span id="translatedtitle">The significance of grain morphology, moisture, and <span class="hlt">strain</span> <span class="hlt">rate</span> on the rapid compaction of silica sands</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Perry, J. I.; Braithwaite, C. H.; Taylor, N. E.; Pullen, A. D.; Jardine, A. P.</p> <p>2016-10-01</p> <p>There is considerable interest in the high-<span class="hlt">rate</span> compaction of brittle granular materials such as sand. However, the vast majority of studies focus on a single granular system, limiting our ability to make comparisons between materials to discern how granular structure manifests as bulk material response. Here, three different silica sands with similar grain size and shape are studied: we compare a rough quarry sand, a smoother-grained sand, and a sandy loam. Quasi-static compaction and planar shock loading responses are compared, and recovered samples analyzed. The combination provides information regarding the interplay between granular properties, loading conditions, and material response. We show that the fundamental grain-scale behaviour depends on loading conditions: At low <span class="hlt">strain</span> <span class="hlt">rates</span> compaction behaviour is dominated by grain morphology, and in particular, smoothness and particle size distribution. Under shock loading, grain rearrangement and force chain <span class="hlt">effects</span> are suppressed, and the nature of inter-granular contact points, modified by the presence of moisture or fines, is most important. Furthermore, grain fracture under shock loading is substantially reduced with increasing moisture content.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5266008','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5266008"><span id="translatedtitle">Stress corrosion cracking of alloy 600 using the constant <span class="hlt">strain</span> <span class="hlt">rate</span> test</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bulischeck, T. S.; van Rooyen, D.</p> <p>1980-01-01</p> <p>The most recent corrosion problems experienced in nuclear steam generators tubed with Inconel alloy 600 is a phenomenon labeled ''denting''. Denting has been found in various degrees of severity in many operating pressurized water reactors. Laboratory investigations have shown that Inconel 600 exhibits intergranular SCC when subjected to high stresses and exposed to deoxygenated water at elevated temperatures. A research project was initiated at Brookhaven National Laboratory in an attempt to improve the qualitative and quantitative understanding of factors influencing SCC in high temperature service-related environments. An effort is also being made to develop an accelerated test method which could be used to predict the service life of tubes which have been deformed or are actively denting. Several heats of commercial Inconel 600 tubing were procured for testing in deaerated pure and primary water at temperatures from 290 to 365/sup 0/C. U-bend type specimens were used to determine crack initiation times which may be expected for tubes where denting has occurred but is arrested and provide baseline data for judging the accelerating <span class="hlt">effects</span> of the slow <span class="hlt">strain</span> <span class="hlt">rate</span> method. Constant extension <span class="hlt">rate</span> tests were employed to determine the crack velocities experienced in the crack propagation stage and predict failure times of tubes which are actively denting. 8 refs., 17 figs., 5 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21542642','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21542642"><span id="translatedtitle">Controlling the lithiation-induced <span class="hlt">strain</span> and charging <span class="hlt">rate</span> in nanowire electrodes by coating.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Li Qiang; Liu, Xiao Hua; Liu, Yang; Huang, Shan; Zhu, Ting; Gui, Liangjin; Mao, Scott X; Ye, Zhi Zhen; Wang, Chong Min; Sullivan, John P; Huang, Jian Yu</p> <p>2011-06-28</p> <p>The advanced battery system is critically important for a wide range of applications, from portable electronics to electric vehicles. Lithium ion batteries (LIBs) are presently the best performing ones, but they cannot meet requirements for more demanding applications due to limitations in capacity, charging <span class="hlt">rate</span>, and cyclability. One leading cause of those limitations is the lithiation-induced <span class="hlt">strain</span> (LIS) in electrodes that can result in high stress, fracture, and capacity loss. Here we report that, by utilizing the coating strategy, both the charging <span class="hlt">rate</span> and LIS of SnO(2) nanowire electrodes can be altered dramatically. The SnO(2) nanowires coated with carbon, aluminum, or copper can be charged about 10 times faster than the noncoated ones. Intriguingly, the radial expansion of the coated nanowires was completely suppressed, resulting in enormously reduced tensile stress at the reaction front, as evidenced by the lack of formation of dislocations. These improvements are attributed to the <span class="hlt">effective</span> electronic conduction and mechanical confinement of the coatings. Our work demonstrates that nanoengineering the coating enables the simultaneous control of electrical and mechanical behaviors of electrodes, pointing to a promising route for building better LIBs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JNR....17...65H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JNR....17...65H"><span id="translatedtitle">Influence of oxygen concentration, fuel composition, and <span class="hlt">strain</span> <span class="hlt">rate</span> on synthesis of carbon nanomaterials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hou, Shuhn-Shyurng; Huang, Wei-Cheng</p> <p>2015-02-01</p> <p>This paper investigates the influence of flame parameters including oxygen concentration, fuel composition, and <span class="hlt">strain</span> <span class="hlt">rate</span> on the synthesis of carbon nanomaterials in opposed-jet ethylene diffusion flames with or without rigid-body rotation. In the experiments, a mixture of ethylene and nitrogen was introduced from the upper burner; meanwhile, a mixture of oxygen and nitrogen was supplied from the lower burner. A nascent nickel mesh was used as the catalytic metal substrate to collect deposited materials. With non-rotating opposed-jet diffusion flames, carbon nanotubes (CNTs) were successfully produced for oxygen concentrations in the range of 21-50 % at a fixed ethylene concentration of 20 %, and for ethylene concentrations ranging from 14 to 24 % at a constant oxygen concentration of 40 %. With rotating opposed-jet diffusion flames, the <span class="hlt">strain</span> <span class="hlt">rate</span> was varied by adjusting the angular velocities of the upper and lower burners. The <span class="hlt">strain</span> <span class="hlt">rate</span> governed by flow rotation greatly affects the synthesis of carbon nanomaterials [i.e., CNTs and carbon nano-onions (CNOs)] either through the residence time or carbon sources available. An increase in the angular velocity lengthened the residence time of the flow and thus caused the diffusion flame to experience a decreased <span class="hlt">strain</span> <span class="hlt">rate</span>, which in turn produced more carbon sources. The growth of multi-walled CNTs was achieved for the stretched flames experiencing a higher <span class="hlt">strain</span> <span class="hlt">rate</span> [i.e., angular velocity was equal to 0 or 1 rotations per second (rps)]. CNOs were synthesized at a lower <span class="hlt">strain</span> <span class="hlt">rate</span> (i.e., angular velocity was in the range of 2-5 rps). It is noteworthy that the <span class="hlt">strain</span> <span class="hlt">rate</span> controlled by flow rotation greatly influences the fabrication of carbon nanostructures owing to the residence time as well as carbon source. Additionally, more carbon sources and higher temperature are required for the synthesis of CNOs compared with those required for CNTs (i.e., about 605-625 °C for CNTs and 700-800 °C for CNOs).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18946156','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18946156"><span id="translatedtitle">A real-time heat <span class="hlt">strain</span> risk classifier using heart <span class="hlt">rate</span> and skin temperature.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Buller, Mark J; Latzka, William A; Yokota, Miyo; Tharion, William J; Moran, Daniel S</p> <p>2008-12-01</p> <p>Heat injury is a real concern to workers engaged in physically demanding tasks in high heat <span class="hlt">strain</span> environments. Several real-time physiological monitoring systems exist that can provide indices of heat <span class="hlt">strain</span>, e.g. physiological <span class="hlt">strain</span> index (PSI), and provide alerts to medical personnel. However, these systems depend on core temperature measurement using expensive, ingestible thermometer pills. Seeking a better solution, we suggest the use of a model which can identify the probability that individuals are 'at risk' from heat injury using non-invasive measures. The intent is for the system to identify individuals who need monitoring more closely or who should apply heat <span class="hlt">strain</span> mitigation strategies. We generated a model that can identify 'at risk' (PSI 7.5) workers from measures of heart <span class="hlt">rate</span> and chest skin temperature. The model was built using data from six previously published exercise studies in which some subjects wore chemical protective equipment. The model has an overall classification error <span class="hlt">rate</span> of 10% with one false negative error (2.7%), and outperforms an earlier model and a least squares regression model with classification errors of 21% and 14%, respectively. Additionally, the model allows the classification criteria to be adjusted based on the task and acceptable level of risk. We conclude that the model could be a valuable part of a multi-faceted heat <span class="hlt">strain</span> management system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25803703','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25803703"><span id="translatedtitle">Compressive viscoelasticity of freshly excised mouse skin is dependent on specimen thickness, <span class="hlt">strain</span> level and <span class="hlt">rate</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Yuxiang; Marshall, Kara L; Baba, Yoshichika; Lumpkin, Ellen A; Gerling, Gregory J</p> <p>2015-01-01</p> <p>Although the skin's mechanical properties are well characterized in tension, little work has been done in compression. Here, the viscoelastic properties of a population of mouse skin specimens (139 samples from 36 mice, aged 5 to 34 weeks) were characterized upon varying specimen thickness, as well as <span class="hlt">strain</span> level and <span class="hlt">rate</span>. Over the population, we observed the skin's viscoelasticity to be quite variable, yet found systematic correlation of residual stress ratio with skin thickness and <span class="hlt">strain</span>, and of relaxation time constants with <span class="hlt">strain</span> <span class="hlt">rates</span>. In particular, as specimen thickness ranged from 211 to 671 μm, we observed significant variation in both quasi-linear viscoelasticity (QLV) parameters, the relaxation time constant (τ1 = 0.19 ± 0.10 s) and steady-state residual stress ratio (G∞ = 0.28 ± 0.13). Moreover, when τ1 was decoupled and fixed, we observed that G∞ positively correlated with skin thickness. Second, as steady-state stretch was increased (λ∞ from 0.22 to 0.81), we observed significant variation in both QLV parameters (τ1 = 0.26 ± 0.14 s, G∞ = 0.47 ± 0.17), and when τ1 was fixed, G∞ positively correlated with stretch level. Third, as <span class="hlt">strain</span> <span class="hlt">rate</span> was increased from 0.06 to 22.88 s-1, the median time constant τ1 varied from 1.90 to 0.31 s, and thereby negatively correlated with <span class="hlt">strain</span> <span class="hlt">rate</span>. These findings indicate that the natural range of specimen thickness, as well as experimental controls of compression level and <span class="hlt">rate</span>, significantly influence measurements of skin viscoelasticity.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.G22A..07S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.G22A..07S"><span id="translatedtitle">Horizontal <span class="hlt">strain</span> <span class="hlt">rate</span> estimation using discrete geodetic data and its application to Southern California (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shen, Z.; Zeng, Y.</p> <p>2010-12-01</p> <p>We present an algorithm to calculate horizontal <span class="hlt">strain</span> <span class="hlt">rates</span> through interpolation of a geodetically derived velocity field. To derive a smoothly distributed <span class="hlt">strain</span> <span class="hlt">rate</span> field using discrete geodetic observations is an under-determined inverse problem. Therefore a priori information, in the form of weighted smoothing, is required to facilitate the solution. Our method is revised from the previous approaches of Shen et al. (1996, 2007). At a given location, the velocity field in its vicinity is approximated by a linear function of positions and can be represented by two velocity components, three <span class="hlt">strain</span> <span class="hlt">rate</span> components, and a rotation <span class="hlt">rate</span> at that point. The velocity data in the neighborhood, after re-weighting, are used to estimate the field parameters through a least-squares procedure. Data weighting is done with following considerations: (a) Data are weighted according to either the Voronoi cell area of each neighboring site, or the station azimuthal span of two azimuthally adjacent neighboring sites. (b) A distance weighting factor is assigned according to site-to-station distances, in the form of either a Gaussian or quadratic decay function. (c) The distance decay coefficient is determined from setting a minimum total weighting threshold which is defined as the sum of the weighting coefficients for all the data input. We also developed an algorithm to exclude contributions of the non-elastic <span class="hlt">strain</span> associated with fault creep such as creeping along the Central California Creeping segment of the San Andres fault system. We apply this method to derive the <span class="hlt">strain</span> <span class="hlt">rate</span> field for southern California using the SCEC CMM4 velocity field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT.......483S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT.......483S"><span id="translatedtitle">The chemical and mechanical behaviors of polymer / reactive metal systems under high <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shen, Yubin</p> <p></p> <p>As one category of energetic materials, impact-initiated reactive materials are able to release a high amount of stored chemical energy under high <span class="hlt">strain</span> <span class="hlt">rate</span> impact loading, and are used extensively in civil and military applications. In general, polymers are introduced as binder materials to trap the reactive metal powders inside, and also act as an oxidizing agent for the metal ingredient. Since critical attention has been paid on the metal / metal reaction, only a few types of polymer / reactive metal interactions have been studied in the literature. With the higher requirement of materials resistant to different thermal and mechanical environments, the understanding and characterization of polymer / reactive metal interactions are in great demand. In this study, PTFE (Polytetrafluoroethylene) 7A / Ti (Titanium) composites were studied under high <span class="hlt">strain</span> <span class="hlt">rates</span> by utilizing the Taylor impact and SHPB tests. Taylor impact tests with different impact velocities, sample dimensions and sample configurations were conducted on the composite, equipped with a high-speed camera for tracking transient images during the sudden process. SHPB and Instron tests were carried out to obtain the stress vs. <span class="hlt">strain</span> curves of the composite under a wide range of <span class="hlt">strain</span> <span class="hlt">rates</span>, the result of which were also utilized for fitting the constitutive relations of the composite based on the modified Johnson-Cook strength model. Thermal analyses by DTA tests under different flow <span class="hlt">rates</span> accompanied with XRD identification were conducted to study the reaction mechanism between PTFE 7A and Ti when only heat was provided. Numerical simulations on Taylor impact tests and microstructural deformations were also performed to validate the constitutive model built for the composite system, and to investigate the possible reaction mechanism between two components. The results obtained from the high <span class="hlt">strain</span> <span class="hlt">rate</span> tests, thermal analyses and numerical simulations were combined to provide a systematic study on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4372409','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4372409"><span id="translatedtitle">Compressive Viscoelasticity of Freshly Excised Mouse Skin Is Dependent on Specimen Thickness, <span class="hlt">Strain</span> Level and <span class="hlt">Rate</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wang, Yuxiang; Marshall, Kara L.; Baba, Yoshichika; Lumpkin, Ellen A.; Gerling, Gregory J.</p> <p>2015-01-01</p> <p>Although the skin’s mechanical properties are well characterized in tension, little work has been done in compression. Here, the viscoelastic properties of a population of mouse skin specimens (139 samples from 36 mice, aged 5 to 34 weeks) were characterized upon varying specimen thickness, as well as <span class="hlt">strain</span> level and <span class="hlt">rate</span>. Over the population, we observed the skin’s viscoelasticity to be quite variable, yet found systematic correlation of residual stress ratio with skin thickness and <span class="hlt">strain</span>, and of relaxation time constants with <span class="hlt">strain</span> <span class="hlt">rates</span>. In particular, as specimen thickness ranged from 211 to 671 μm, we observed significant variation in both quasi-linear viscoelasticity (QLV) parameters, the relaxation time constant (τ1 = 0.19 ± 0.10 s) and steady-state residual stress ratio (G∞ = 0.28 ± 0.13). Moreover, when τ1 was decoupled and fixed, we observed that G∞ positively correlated with skin thickness. Second, as steady-state stretch was increased (λ∞ from 0.22 to 0.81), we observed significant variation in both QLV parameters (τ1 = 0.26 ± 0.14 s, G∞ = 0.47 ± 0.17), and when τ1 was fixed, G∞ positively correlated with stretch level. Third, as <span class="hlt">strain</span> <span class="hlt">rate</span> was increased from 0.06 to 22.88 s−1, the median time constant τ1 varied from 1.90 to 0.31 s, and thereby negatively correlated with <span class="hlt">strain</span> <span class="hlt">rate</span>. These findings indicate that the natural range of specimen thickness, as well as experimental controls of compression level and <span class="hlt">rate</span>, significantly influence measurements of skin viscoelasticity. PMID:25803703</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EPJWC..9404055S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9404055S"><span id="translatedtitle">Flow and failure of an aluminium alloy from low to high temperature and <span class="hlt">strain</span> <span class="hlt">rate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sancho, Rafael; Cendón, David; Gálvez, Francisco</p> <p>2015-09-01</p> <p>The mechanical behaviour of an aluminium alloy is presented in this paper. The study has been carried out to analyse the flow and failure of the aluminium alloy 7075-T73. An experimental study has been planned performing tests of un-notched and notched tensile specimens at low <span class="hlt">strain</span> <span class="hlt">rates</span> using a servo-hydraulic machine. High <span class="hlt">strain</span> <span class="hlt">rate</span> tests have been carried out using the same geometry in a Hopkinson Split Tensile Bar. The dynamic experiments at low temperature were performed using a cryogenic chamber, and the high temperature ones with a furnace, both incorporated to the Hopkinson bar. Testing temperatures ranged from - 50 ∘C to 100 ∘C and the <span class="hlt">strain</span> <span class="hlt">rates</span> from 10-4 s-1 to 600 s-1. The material behaviour was modelled using the Modified Johnson-Cook model and simulated using LS-DYNA. The results show that the Voce type of <span class="hlt">strain</span> hardening is the most accurate for this material, while the traditional Johnson-Cook is not enough accurate to reproduce the necking of un-notched specimens. The failure criterion was obtained by means of the numerical simulations using the analysis of the stress triaxiality versus the <span class="hlt">strain</span> to failure. The diameters at the failure time were measured using the images taken with an image camera, and the <span class="hlt">strain</span> to failure was computed for un-notched and notched specimens. The numerical simulations show that the analysis of the evolution of the stress triaxiality is crucial to achieve accurate results. A material model using the Modified Johnson-Cook for flow and failure is proposed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990053983&hterms=squat&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dsquat','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990053983&hterms=squat&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dsquat"><span id="translatedtitle">Planar <span class="hlt">Strain-Rate</span>-Free Diffusion Flames: Initiation, Properties, and Extinction</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Fendell, Francis; Gokoglu, Suleyman; Rungaldier, Harald; Schultz, Donald</p> <p>1999-01-01</p> <p>An <span class="hlt">effectively</span> <span class="hlt">strain-rate</span>-free diffusion flame constitutes the most vigorous laminar combustion of initially unmixed reactive gases. Such a diffusion flame is characterized by a relatively long residence time and by a relatively large characteristic length scale. If such a flame were also planar, providing high symmetry, it would be particularly suitable for experimental and theoretical investigations of key combustion phenomena, such as multicomponent diffusion, chemical kinetics, and soot inception, growth, and oxidation. Unfortunately, a planar <span class="hlt">strain-rate</span>-free diffusion flame is highly disrupted in earth-gravity (e.g., in a counterflow-diffusion-flame apparatus) because of the very rapid onset (approx. 100 ms) of gravity-induced instability. Accordingly, a specially dedicated apparatus was designed, fabricated, and initially checked out for the examination of a planar <span class="hlt">strain-rate</span>-free diffusion flame in microgravity. Such a diffusion flame may be formed within a hollowed-out squat container (initially configured as 25 cm x 25 cm x 9 cm), with isothermal, noncatalytic, impervious walls. At test initiation, a thin metallic sheet (approx. 1 mm in thickness) that separates the internal volume into two equal portions, each of dimensions 25 cm x 25 cm x 4.5 cm, is withdrawn, by uniform translation (approx. 50 cm/s) in its own plane, through a tightly fitting slit in one side wall. Thereupon, diluted fuel vapor (initially confined to one half-volume of the container) gains access to diluted oxygen (initially with the same pressure, density, and temperature as the fuel, but initially confined to the other half-volume). After a brief delay (approx. 10 ms), to permit limited but sufficient-for-flammability diffusional interpenetration of fuel vapor and oxidizer, burning is initiated by discharge of a line igniter, located along that side wall from which the trailing edge of the separator withdraws. The ignition spawns a triple-flame propagation across the 25 cm x 25 cm</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10194975','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10194975"><span id="translatedtitle">Deviatoric stresses and plastic <span class="hlt">strain</span> <span class="hlt">rates</span> in strong shock waves for six metals</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tonks, D.L.</p> <p>1993-11-01</p> <p>The strong shock theory of D. C. Wallace [Phys. Rev. B24, 5597 (198 1) and Phys. Rev. B24, 5607 (1981)] is used to calculate the shock structure for 1100 Al, 2024 Al, Cu, Fe, Ta, and U. Emphasis is given to the behavior of plasticity, i.e., average deviatoric stresses, plastic and total <span class="hlt">strains</span>, and <span class="hlt">strain</span> <span class="hlt">rates</span>, which are given in figures for a number of shock strengths. This information will be useful for modeling plasticity in metals under extreme conditions. It was used for part of the PTW model for mechanical behavior.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3878538','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3878538"><span id="translatedtitle">Detection of Left Ventricular Regional Function in Asymptomatic Children with beta-Thalassemia Major by Longitudinal <span class="hlt">Strain</span> and <span class="hlt">Strain</span> <span class="hlt">Rate</span> Imaging</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bay, Ali; Başpınar, Osman; Leblebisatan, Göksel; Yalçın, Ali Seçkin; İrdem, Ahmet</p> <p>2013-01-01</p> <p>Objective: Cardiac failure due to iron overload remains the most common cause of death in patients with beta-thalassemia major. This study aimed to evaluate myocardial function in children with beta-thalassemia major using standard echocardiography technique and <span class="hlt">strain</span> <span class="hlt">rate</span> imaging. Materials and Methods: Conventional echocardiographic analysis, tissue velocity imaging, and <span class="hlt">strain/strain</span> <span class="hlt">rate</span> imaging of the left ventricle were evaluated in 48 children with beta-thalassemia major (19 girls, 29 boys; 8.39±4.05 years) and 22 healthy children (11 girls, 11 boys; 8±3.72 years). Results: Conventional echocardiographic examinations revealed that beta-thalassemia patients had larger left ventricular end-systolic diameter, end-diastolic and end-systolic volume, left ventricular mass index, and mitral early/late diastolic flow velocity ratio (p<0.05). <span class="hlt">Strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> imaging study of the basal lateral wall of the left ventricle was higher in patients than in controls, at p=0.035 and p=0.008, respectively. Conclusion: We found that superior systolic <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> imaging of the left ventricle indicated the presence of regional systolic function in the left ventricular wall. We suggest that left ventricle volume and mass index parameters might be more sensitive than the other conventional and <span class="hlt">strain/strain</span> <span class="hlt">rate</span> imaging parameters during childhood. However, the adulthood <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> imaging values may be lower than controls, exceeding the critical level of iron overload. Conflict of interest:None declared. PMID:24385808</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870011944','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870011944"><span id="translatedtitle">Convergence of <span class="hlt">strain</span> energy release <span class="hlt">rate</span> components for edge-delaminated composite laminates</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Raju, I. S.; Crews, J. H., Jr.; Aminpour, M. A.</p> <p>1987-01-01</p> <p><span class="hlt">Strain</span> energy release <span class="hlt">rates</span> for edge delaminated composite laminates were obtained using quasi 3 dimensional finite element analysis. The problem of edge delamination at the -35/90 interfaces of an 8-ply composite laminate subjected to uniform axial <span class="hlt">strain</span> was studied. The individual components of the <span class="hlt">strain</span> energy release <span class="hlt">rates</span> did not show convergence as the delamination tip elements were made smaller. In contrast, the total <span class="hlt">strain</span> energy release <span class="hlt">rate</span> converged and remained unchanged as the delamination tip elements were made smaller and agreed with that calculated using a classical laminated plate theory. The studies of the near field solutions for a delamination at an interface between two dissimilar isotropic or orthotropic plates showed that the imaginary part of the singularity is the cause of the nonconvergent behavior of the individual components. To evaluate the accuracy of the results, an 8-ply laminate with the delamination modeled in a thin resin layer, that exists between the -35 and 90 plies, was analyzed. Because the delamination exists in a homogeneous isotropic material, the oscillatory component of the singularity vanishes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880057797&hterms=convergence+media&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dconvergence%2Bmedia','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880057797&hterms=convergence+media&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dconvergence%2Bmedia"><span id="translatedtitle">Convergence of <span class="hlt">strain</span> energy release <span class="hlt">rate</span> components for edge-delaminated composite laminates</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Raju, I. S.; Crews, J. H., Jr.; Aminpour, M. A.</p> <p>1988-01-01</p> <p><span class="hlt">Strain</span> energy release <span class="hlt">rates</span> for edge delaminated composite laminates were obtained using quasi 3 dimensional finite element analysis. The problem of edge delamination at the -35/90 interfaces of an 8-ply composite laminate subjected to uniform axial <span class="hlt">strain</span> was studied. The individual components of the <span class="hlt">strain</span> energy release <span class="hlt">rates</span> did not show convergence as the delamination tip elements were made smaller. In contrast, the total <span class="hlt">strain</span> energy release <span class="hlt">rate</span> converged and remained unchanged as the delamination tip elements were made smaller and agreed with that calculated using a classical laminated plate theory. The studies of the near field solutions for a delamination at an interface between two dissimilar isotropic or orthotropic plates showed that the imaginary part of the singularity is the cause of the nonconvergent behavior of the individual components. To evaluate the accuracy of the results, an 8-ply laminate with the delamination modeled in a thin resin layer, that exists between the -35 and 90 plies, was analyzed. Because the delamination exists in a homogeneous isotropic material, the oscillatory component of the singularity vanishes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997JFM...350...29H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997JFM...350...29H"><span id="translatedtitle">Vorticity, <span class="hlt">strain-rate</span> and dissipation characteristics in the near-wall region of turbulent boundary layers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Honkan, Anant; Andreopoulos, Yiannis</p> <p>1997-11-01</p> <p>Experimental results are presented that reveal the structure of a two-dimensional turbulent boundary layer which has been investigated by measuring the time-dependent vorticity flux at the wall, vorticity vector, <span class="hlt">strain-rate</span> tensor and dissipation-<span class="hlt">rate</span> tensor in the near-wall region with spatial resolution of the order of 7 Kolmogorov viscous length scales. Considerations of the structure function of velocity and pressure, which constitute vorticity flux and vorticity, indicated that, in the limit of vanishing distance, the maximum attainable content of these quantities which corresponds to unrestricted resolution, is determined by Taylor's microscale. They also indicated that most of the contributions to vorticity or vorticity flux come from the uncorrelated part of the two signals involved. The measurements allowed the computation of all components of the vorticity stretching vector, which indicates the <span class="hlt">rate</span> of change of vorticity on a Lagrangian reference frame if viscous <span class="hlt">effects</span> are negligible, and several matrix invariants of the velocity gradient or <span class="hlt">strain-rate</span> tensor and terms appearing in the transport equations of vorticity, <span class="hlt">strain</span> <span class="hlt">rate</span> and their squared fluctuations. The orientation of vorticity revealed several preferential directions. During bursts or sweeps vorticity is inclined at 35° to the longitudinal direction. It was also found that there is high probability of the vorticity vector aligning with the direction of the intermediate extensive <span class="hlt">strain</span> corresponding to the middle eigenvector of the <span class="hlt">strain-rate</span> matrix. The results of the joint probability distributions of the vorticity vector orientation angles showed that these angles may be related to those of hairpin vortex structures. All invariants considered exhibit a very strong intermittent behaviour which is characterized by large-amplitude bursts which may be of the order of 10 r.m.s. values. Small-scale motions dominated by high <span class="hlt">rates</span> of turbulent kinetic energy dissipation and high enstrophy</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980227139','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980227139"><span id="translatedtitle">High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Deformation Modeling of a Polymer Matrix Composite. Part 1; Matrix Constitutive Equations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldberg, Robert K.; Stouffer, Donald C.</p> <p>1998-01-01</p> <p>Recently applications have exposed polymer matrix composite materials to very high <span class="hlt">strain</span> <span class="hlt">rate</span> loading conditions, requiring an ability to understand and predict the material behavior under these extreme conditions. In this first paper of a two part report, background information is presented, along with the constitutive equations which will be used to model the <span class="hlt">rate</span> dependent nonlinear deformation response of the polymer matrix. <span class="hlt">Strain</span> <span class="hlt">rate</span> dependent inelastic constitutive models which were originally developed to model the viscoplastic deformation of metals have been adapted to model the nonlinear viscoelastic deformation of polymers. The modified equations were correlated by analyzing the tensile/ compressive response of both 977-2 toughened epoxy matrix and PEEK thermoplastic matrix over a variety of <span class="hlt">strain</span> <span class="hlt">rates</span>. For the cases examined, the modified constitutive equations appear to do an adequate job of modeling the polymer deformation response. A second follow-up paper will describe the implementation of the polymer deformation model into a composite micromechanical model, to allow for the modeling of the nonlinear, <span class="hlt">rate</span> dependent deformation response of polymer matrix composites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/9756','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/9756"><span id="translatedtitle">Intermediate <span class="hlt">Strain-Rate</span> Loading Experiments - Technique and Applications to Ceramics</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chhabildas, L.C.; Reinhart, W.D.</p> <p>1999-08-16</p> <p>A new test methodology is described which allows access to loading <span class="hlt">rates</span> that lie between split Hopkinson bar and shock-loading techniques. Gas gun experiments combined with velocity interferometry techniques have been used to experimentally determine the intermediate <span class="hlt">strain-rate</span> loading behavior of Coors AD995 alumina and Cercom silicon-carbide rods. Graded-density materials have been used as impactors; thereby eliminating the tension states generated by the radial stress components during the loading phase. Results of these experiments demonstrate that the time-dependent stress pulse generated during impact allows an efficient transition from the initial uniaxial <span class="hlt">strain</span> loading to a uniaxial stress state as the stress pulse propagates through the rod. This allows access to intermediate loading <span class="hlt">rates</span> over 5 x 10{sup 3}/s to a few times 10{sup 4}/s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980237009','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980237009"><span id="translatedtitle">High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Deformation Modeling of a Polymer Matrix Composite. Part 2; Composite Micromechanical Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldberg, Robert K.; Stouffer, Donald C.</p> <p>1998-01-01</p> <p>Recently applications have exposed polymer matrix composite materials to very high <span class="hlt">strain</span> <span class="hlt">rate</span> loading conditions, requiring an ability to understand and predict the material behavior under these extreme conditions. In this second paper of a two part report, a three-dimensional composite micromechanical model is described which allows for the analysis of the <span class="hlt">rate</span> dependent, nonlinear deformation response of a polymer matrix composite. <span class="hlt">Strain</span> <span class="hlt">rate</span> dependent inelastic constitutive equations utilized to model the deformation response of a polymer are implemented within the micromechanics method. The deformation response of two representative laminated carbon fiber reinforced composite materials with varying fiber orientation has been predicted using the described technique. The predicted results compare favorably to both experimental values and the response predicted by the Generalized Method of Cells, a well-established micromechanics analysis method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/269462','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/269462"><span id="translatedtitle">The role of reactant unmixedness, <span class="hlt">strain</span> <span class="hlt">rate</span>, and length scale on premixed combustor performance</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Samuelsen, S.; LaRue, J.; Vilayanur, S.</p> <p>1995-10-01</p> <p>Lean premixed combustion provides a means to reduce pollutant formation and increase combustion efficiency. However, fuel-air mixing is rarely uniform in space and time. This nonuniformity in concentration will lead to relative increases in pollutant formation and decreases in combustion efficiency. The nonuniformity of the concentration at the exit of the premixer has been defined by Lyons (1981) as the {open_quotes}unmixedness.{close_quotes} Although turbulence properties such as length scales and <span class="hlt">strain</span> <span class="hlt">rate</span> are known to <span class="hlt">effect</span> unmixedness, the exact relationship is unknown. Evaluating this relationship and the <span class="hlt">effect</span> of unmixedness in premixed combustion on pollutant formation and combustion efficiency are an important part of the overall goal of US Department of Energy`s Advanced Turbine Systems (ATS) program and are among the goals of the program described herein. The information obtained from ATS is intended to help to develop and commercialize gas turbines which have (1) a wide range of operation/stability, (2) a minimal amount of pollutant formation, and (3) high combustion efficiency. Specifically, with regard to pollutants, the goals are to reduce the NO{sub x} emissions by at least 10%, obtain less than 20 PPM of both CO and UHC, and increase the combustion efficiency by 5%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4204971','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4204971"><span id="translatedtitle">Morphology and mycelial growth <span class="hlt">rate</span> of Pleurotus spp. <span class="hlt">strains</span> from the Mexican mixtec region</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Guadarrama-Mendoza, P.C.; del Toro, G. Valencia; Ramírez-Carrillo, R.; Robles-Martínez, F.; Yáñez-Fernández, J.; Garín-Aguilar, M.E.; Hernández, C.G.; Bravo-Villa, G.</p> <p>2014-01-01</p> <p>Two native Pleurotus spp. <span class="hlt">strains</span> (white LB-050 and pale pink LB-051) were isolated from rotten tree trunks of cazahuate (Ipomoea murucoides) from the Mexican Mixtec Region. Both <span class="hlt">strains</span> were chemically dedikaryotized to obtain their symmetrical monokaryotic components (neohaplonts). This was achieved employing homogenization time periods from 60 to 65 s, and 3 day incubation at 28 °C in a peptone-glucose solution (PGS). Pairing of compatible neohaplonts resulted in 56 hybrid <span class="hlt">strains</span> which were classified into the four following hybrid types: (R1-nxB1-n, R1-nxB2-1, R2-nxB1-n and R2-nxB2-1). The mycelial growth of Pleurotus spp. monokaryotic and dikaryotic <span class="hlt">strains</span> showed differences in texture (cottony or floccose), growth (scarce, regular or abundant), density (high, regular or low), and pigmentation (off-white, white or pale pink). To determine the <span class="hlt">rate</span> and the amount of mycelium growth in malt extract agar at 28 °C, the diameter of the colony was measured every 24 h until the Petri dish was completely colonized. A linear model had the best fit to the mycelial growth kinetics. A direct relationship between mycelial morphology and growth <span class="hlt">rate</span> was observed. Cottony mycelium presented significantly higher growth <span class="hlt">rates</span> (p < 0.01) in comparison with floccose mycelium. Thus, mycelial morphology can be used as criterion to select which pairs must be used for optimizing compatible-mating studies. Hybrids resulting from cottony neohaplonts maintained the characteristically high growth <span class="hlt">rates</span> of their parental <span class="hlt">strains</span> with the hybrid R1-nxB1-n being faster than the latter. PMID:25477920</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15773268','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15773268"><span id="translatedtitle">Quantitation of stress echocardiography by tissue Doppler and <span class="hlt">strain</span> <span class="hlt">rate</span> imaging: a dream come true?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Galderisi, Maurizio; Mele, Donato; Marino, Paolo Nicola</p> <p>2005-01-01</p> <p>Tissue Doppler (TD) is an ultrasound tool providing a quantitative agreement of left ventricular regional myocardial function in different modalities. Spectral pulsed wave (PW) TD, performed online during the examination, measures instantaneous myocardial velocities. By means of color TD, velocity images are digitally stored for subsequent off-line analysis and mean myocardial velocities are measured. An implementation of color TD includes <span class="hlt">strain</span> <span class="hlt">rate</span> imaging (SRI), based on post-processing conversion of regional velocities in local myocardial deformation <span class="hlt">rate</span> (<span class="hlt">strain</span> <span class="hlt">rate</span>) and percent deformation (<span class="hlt">strain</span>). These three modalities have been applied to stress echocardiography for quantitative evaluation of regional left ventricular function and detection of ischemia and viability. They present advantages and limitations. PWTD does not permit the simultaneous assessment of multiple walls and therefore is not compatible with clinical stress echocardiography while it could be used in a laboratory setting. Color TD provides a spatial map of velocity throughout the myocardium but its results are strongly affected by the frame <span class="hlt">rate</span>. Both color TD and PWTD are also influenced by overall cardiac motion and tethering from adjacent segments and require reference velocity values for interpretation of regional left ventricular function. High frame <span class="hlt">rate</span> (i.e. > 150 ms) post-processing-derived SRI can potentially overcome these limitations, since measurements of myocardial deformation have not any significant apex-to-base gradient. Preliminary studies have shown encouraging results about the ability of SRI to detect ischemia and viability, in terms of both <span class="hlt">strain</span> <span class="hlt">rate</span> changes and/or evidence of post-systolic thickening. SRI is, however, Doppler-dependent and time-consuming. Further technical refinements are needed to improve its application and introduce new ultrasound modalities to overcome the limitations of the Doppler-derived deformation analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFMIN43A0907R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFMIN43A0907R"><span id="translatedtitle">Using Google Earth to Explore <span class="hlt">Strain</span> <span class="hlt">Rate</span> Models of Southern California</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Richard, G. A.; Bell, E. A.; Holt, W. E.</p> <p>2007-12-01</p> <p>A series of <span class="hlt">strain</span> <span class="hlt">rate</span> models for the Transverse Ranges of southern California were developed based on Quaternary fault slip data and geodetic data from high precision GPS stations in southern California. Pacific-North America velocity boundary conditions are applied for all models. Topography changes are calculated using the model dilatation <span class="hlt">rates</span>, which predict crustal thickness changes under the assumption of Airy isostasy and a specified <span class="hlt">rate</span> of crustal volume loss through erosion. The models were designed to produce graphical and numerical output representing the configuration of the region from 3 million years ago to 3 million years into the future at intervals of 50 thousand years. Using a North American reference frame, graphical output for the topography and faults and numerical output for locations of faults and points on the crust marked by the locations on cities were used to create data in KML format that can be used in Google Earth to represent time intervals of 50 thousand years. As markers familiar to students, the cities provide a geographic context that can be used to quantify crustal movement, using the Google Earth ruler tool. By comparing distances that markers for selected cities have moved in various parts of the region, students discover that the greatest amount of crustal deformation has occurred in the vicinity of the boundary between the North American and Pacific plates. Students can also identify areas of compression or extension by finding pairs of city markers that have converged or diverged, respectively, over time. The Google Earth layers also reveal that faults that are not parallel to the plate boundary have tended to rotate clockwise due to the right lateral motion along the plate boundary zone. KML TimeSpan markup was added to two versions of the model, enabling the layers to be displayed in an automatic sequenced loop for a movie <span class="hlt">effect</span>. The data is also available as QuickTime (.mov) and Graphics Interchange Format (.gif</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1111029','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1111029"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">effects</span> on oxygen transport in tetragonal zirconium dioxide</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Xian-Ming Bai; Yongfeng Zhang; Michael R. Tonks</p> <p>2013-11-01</p> <p>Temperature accelerated dynamics and molecular dynamics simulations are used to investigate the <span class="hlt">strain</span> <span class="hlt">effects</span> on oxygen interstitial and vacancy migration in tetragonal zirconium dioxide. At zero external <span class="hlt">strain</span>, the anisotropic migration mechanisms of oxygen defects are characterized. At non-zero <span class="hlt">strains</span>, both the crystal structure and defect migration barriers are modified by <span class="hlt">strain</span>. Under compressive <span class="hlt">strains</span>, the defect migration barrier increases with the increasing <span class="hlt">strain</span> for both interstitials and vacancies. The crystal structure transforms from a tetragonal to a nearly cubic fluorite structure. Accordingly, the defect migration becomes nearly isotropic. Under dilative <span class="hlt">strains</span>, the migration barrier first decreases then increases with increasing <span class="hlt">strain</span> for both types of defects. The tetragonal phase transforms to a lower symmetry structure that is close to the orthorhombic phase. In turn, the defect migration becomes highly anisotropic. Under both compressive and dilative <span class="hlt">strains</span>, interstitials respond to <span class="hlt">strain</span> more strongly than vacancies. At small dilative <span class="hlt">strains</span>, an oxygen interstitial has comparable diffusivity to a vacancy, suggesting that both types of defects can contribute to oxygen transport, if they are present. Although currently no previous result is available to validate oxygen interstitial diffusion behavior, the trend of <span class="hlt">strain</span> <span class="hlt">effects</span> on oxygen vacancy diffusion is in good agreement with available experimental and theoretical studies in the literature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150000883','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150000883"><span id="translatedtitle">Slow <span class="hlt">Strain</span> <span class="hlt">Rate</span> Tensile Testing to Assess the Ability of Superalloys to Resist Environment-Assisted Intergranular Cracking</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gabb, Timothy P.; Telesman, Jack; Banik, Anthony; McDevitt, Erin</p> <p>2014-01-01</p> <p>Intergranular fatigue crack initiation and growth due to environmental degradation, especially at notched features, can often limit the fatigue life of disk superalloys at high temperatures. For clear comparisons, the <span class="hlt">effects</span> of alloy composition on cracking in air needs to be understood and compared separately from variables associated with notches and cracks such as <span class="hlt">effective</span> stress concentration, plastic flow, stress relaxation, and stress redistribution. The objective of this study was to attempt using simple tensile tests of specimens with uniform gage sections to compare the <span class="hlt">effects</span> of varied alloy composition on environment-assisted cracking of several powder metal and cast and wrought superalloys including ME3, LSHR, Udimet 720, ATI 718Plus alloy, Haynes 282, and Inconel 740. Slow and fast <span class="hlt">strain-rate</span> tensile tests were found to be a useful tool to compare propensities for intergranular surface crack initiation and growth. The <span class="hlt">effects</span> of composition and heat treatment on tensile fracture <span class="hlt">strain</span> and associated failure modes were compared. Environment interactions were determined to often limit ductility, by promoting intergranular surface cracking. The response of various superalloys and heat treatments to slow <span class="hlt">strain</span> <span class="hlt">rate</span> tensile testing varied substantially, showing that composition and microstructure can significantly influence environmental resistance to cracking.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMMR41B..05P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMMR41B..05P"><span id="translatedtitle">Micromechanics based permeability evolution in brittle materials at high <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Perol, T.; Bhat, H.</p> <p>2013-12-01</p> <p>We develop a micro-mechanics based permeability evolution model for brittle materials that are <span class="hlt">strain</span> <span class="hlt">rate</span> sensitive. Extending the mechanical constitutive description of brittle solids, whose constitutive response is governed by micro-cracks, developed by Bhat et al. (2012) we now relate the damage related <span class="hlt">strains</span> (plastic <span class="hlt">strains</span>) to calculate the evolution of micro-crack aperture. We then use the permeability model developed by Gueguen and Dienes (1989) and Simpson et al. (2001) to evaluate the permeability evolution. Permeability evolution computed using this model is shown to be in very good agreement with experimental results. Pore pressure evolution in a damaged medium, due to waste water injection for example, is then computed and we show that spatially variable permeability plays a major role in determining the pore pressure excess in the surrounding medium.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1793j0034T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1793j0034T"><span id="translatedtitle">Modelling and simulation of dynamic recrystallization (DRX) in OFHC copper at very high <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Testa, G.; Bonora, N.; Ruggiero, A.; Iannitti, G.; Persechino, I.; Hörnqvist, M.; Mortazavi, N.</p> <p>2017-01-01</p> <p>At high <span class="hlt">strain</span> <span class="hlt">rates</span>, deformation processes are essentially adiabatic and if the plastic work is large enough dynamic recrystallization can occur. In this work, an examination on microstructure evolution of OFHC copper in Dynamic Tensile Extrusion (DTE) test, performed at 400 m/s, was carried out. EBSD investigations, along the center line of the fragment remaining in the extrusion die, showed a progressive elongation of the grains, and an accompanying development of a strong <001> + <111> dual fiber texture. Discontinuous dynamic recrystallization (DRX) occurred at larger <span class="hlt">strains</span>, and it was showed that nucleation occurred during <span class="hlt">straining</span>. A criterion for DRX to occur, based on the evolution of Zener-Hollomon parameter during the dynamic deformation process, is proposed. Finally, DTE test was simulated using the modified Rusinek-Klepaczko constitutive model incorporating a model for the prediction of DRX initiation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/10103430','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10103430"><span id="translatedtitle">The temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> dependence of the flow stress of single crystal NiAl deformed along <110></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Maloy, S.A.; Gray, G.T. III</p> <p>1995-12-31</p> <p>Single crystal NiAl and Ni-49.75Al-0.25Fe have been deformed along <110> at temperatures of 77, 298 and 773K and <span class="hlt">strain</span> <span class="hlt">rates</span> of 0.001/s, and 2000/s. The flow stress of <110> NiAl is <span class="hlt">rate</span> and temperature sensitive. The 0.25 at.% Fe addition resulted in a small increase in flow stress at <span class="hlt">strain</span> <span class="hlt">rates</span> of 0.001 and 0.1/s at 298 and 77K. A significant decrease in the work hardening <span class="hlt">rate</span> is observed after deformation at 77K and a <span class="hlt">strain</span> <span class="hlt">rate</span> of 2000/s. Coarse [110] slip traces are observed after deformation at a <span class="hlt">strain</span> <span class="hlt">rate</span> of 2000/s at 77K, while no slip traces were observed after deformation under all other conditions. TEM observations reveal distinct [110] slip bands after deformation at 77K and a <span class="hlt">strain</span> <span class="hlt">rate</span> of 2000/s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16682046','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16682046"><span id="translatedtitle">The <span class="hlt">effect</span> of muscle fatigue on in vivo tibial <span class="hlt">strains</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Milgrom, Charles; Radeva-Petrova, Denitsa R; Finestone, Aharon; Nyska, Meir; Mendelson, Stephen; Benjuya, Nisim; Simkin, Ariel; Burr, David</p> <p>2007-01-01</p> <p>Stress fracture is a common musculoskeletal problem affecting athletes and soldiers. Repetitive high bone <span class="hlt">strains</span> and <span class="hlt">strain</span> <span class="hlt">rates</span> are considered to be its etiology. The <span class="hlt">strain</span> level necessary to cause fatigue failure of bone ex vivo is higher than the <span class="hlt">strains</span> recorded in humans during vigorous physical activity. We hypothesized that during fatiguing exercises, bone <span class="hlt">strains</span> may increase and reach levels exceeding those measured in the non-fatigued state. To test this hypothesis, we measured in vivo tibial <span class="hlt">strains</span>, the maximum gastrocnemius isokinetic torque and ground reaction forces in four subjects before and after two fatiguing levels of exercise: a 2km run and a 30km desert march. <span class="hlt">Strains</span> were measured using <span class="hlt">strain</span>-gauged staples inserted percutaneously in the medial aspect of their mid-tibial diaphysis. There was a decrease in the peak gastrocnemius isokinetic torque of all four subjects' post-march as compared to pre-run (p=0.0001), indicating the presence of gastrocnemius muscle fatigue. Tension <span class="hlt">strains</span> increased 26% post-run (p=0.002, 95 % confidence interval (CI) and 29% post-march (p=0.0002, 95% CI) as compared to the pre-run phase. Tension <span class="hlt">strain</span> <span class="hlt">rates</span> increased 13% post-run (p=0.001, 95% CI) and 11% post-march (p=0.009, 95% CI) and the compression <span class="hlt">strain</span> <span class="hlt">rates</span> increased 9% post-run (p=0.0004, 95% CI) and 17% post-march (p=0.0001, 95% CI). The fatigue state increases bone <span class="hlt">strains</span> well above those recorded in rested individuals and may be a major factor in the stress fracture etiology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22217924','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22217924"><span id="translatedtitle">Shear avalanches in metallic glasses under nanoindentation: Deformation units and <span class="hlt">rate</span> dependent <span class="hlt">strain</span> burst cut-off</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bian, X. L.; Wang, G.; Gao, Y. L.; Zhai, Q. J.; Chan, K. C.; Ren, J. L.</p> <p>2013-09-02</p> <p>Indented metallic glasses at the nanoscale deform via <span class="hlt">strain</span> bursts. Conventional continuum descriptions are not appropriate for such highly stochastic, intermittent deformations. In this study, after a statistical analysis of <span class="hlt">strain</span> bursts in five metallic glasses, the dependence of the cut-off of the <span class="hlt">strain</span> burst size on deformation units and loading <span class="hlt">rate</span> is established. For soft metallic glasses with smaller deformation units, cut-off of the <span class="hlt">strain</span> burst size truncates the scale-free behavior at larger <span class="hlt">strain</span> burst sizes. For hard metallic glasses, scale-free behavior occurs in a wide range of <span class="hlt">strain</span> burst sizes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/495445','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/495445"><span id="translatedtitle">Slow <span class="hlt">strain</span> <span class="hlt">rate</span> testing of aluminum alloy 7050 in different tempers using various synthetic environments</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Braun, R.</p> <p>1997-06-01</p> <p>The slow <span class="hlt">strain</span> <span class="hlt">rate</span> testing (SSRT) technique was used to investigate the stress corrosion cracking (SCC) behavior of aluminum alloy Al 7050 in different tempers in various electrolytes at the free-corrosion potential. Smooth tensile specimens were <span class="hlt">strained</span> dynamically in the short transverse direction under permanent immersion conditions. <span class="hlt">Strain</span> <span class="hlt">rates</span> were from 5 {times} 10{sup {minus}8}/s to 1 {times} 10{sup {minus}4}/s. Using substitute ocean water, Al 7050 was found sensitive and immune to environmentally assisted cracking in the peak-aged temper T651 and in the over-aged temper T7351, respectively. In the less-over-aged heat treatment T7651, fracture energy data revealed a large scatter. An aqueous solution of 0.5 M sodium perchlorate was not conducive to environmentally assisted cracking. SSRT performed in an aqueous solution of 0.1 M sodium chloride + 0.05 M sodium sulfate + 0.05 M sodium nitrate + 0.01 M sodium bicarbonate at pH 3.5 indicated SCC susceptibility for Al 7050-T651. The latter electrolyte did not promote SCC with the alloy in the heat treatments T7651 and T7351. Scatter was observed in the fracture energy data of Al 7050-T7351 specimens dynamically <span class="hlt">strained</span> in the mixed salt solution. Deterioration was attributed to pitting attack, as supported by fractography.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011PhDT.......236K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011PhDT.......236K"><span id="translatedtitle">An Evaluation of Constitutive Laws and their Ability to Predict Flow Stress over Large Variations in Temperature, <span class="hlt">Strain</span>, and <span class="hlt">Strain</span> <span class="hlt">Rate</span> Characteristic of Friction Stir Welding</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuykendall, Katherine</p> <p>2011-07-01</p> <p>Constitutive laws commonly used to model friction stir welding have been evaluated, both qualitatively and quantitatively, and a new application of a constitutive law which can be extended to materials commonly used in FSW is presented. Existing constitutive laws have been classified as path-dependent or path-independent. Path-independent laws have been further classified according to the physical phenomena they capture: <span class="hlt">strain</span> hardening, <span class="hlt">strain</span> <span class="hlt">rate</span> hardening, and/or thermal softening. Path-dependent laws can track gradients in temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> characteristic to friction stir welding; however, path-independent laws cannot. None of the path-independent constitutive laws evaluated has been validated over the full range of <span class="hlt">strain</span>, <span class="hlt">strain</span> <span class="hlt">rate</span>, and temperature in friction stir welding. Holding all parameters other than constitutive law constant in a friction stir weld model resulted in temperature differences of up to 21%. Varying locations for maximum temperature difference indicate that the constitutive laws resulted in different temperature profiles. The Sheppard and Wright law is capable of capturing saturation but incapable of capturing <span class="hlt">strain</span> hardening with errors as large as 57% near yield. The Johnson-Cook law is capable of capturing <span class="hlt">strain</span> hardening; however, its inability to capture saturation causes over-predictions of stress at large <span class="hlt">strains</span> with errors as large as 37% near saturation. The Kocks and Mecking model is capable of capturing <span class="hlt">strain</span> hardening and saturation with errors less than 5% over the entire range of plastic <span class="hlt">strain</span>. The Sheppard and Wright and Johnson-Cook laws are incapable of capturing transients characteristic of material behavior under interrupted temperature or <span class="hlt">strain</span> <span class="hlt">rate</span>. The use of a state variable in the Kocks and Mecking law allows it to predict such transients. Constants for the Kocks and Mecking model for AA 5083, AA 3004, and Inconel 600 were determined from Atlas of Formability data. Constants for AA 5083 and AA</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JPhCS.382a2043G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JPhCS.382a2043G"><span id="translatedtitle">Finite element analysis of the high <span class="hlt">strain</span> <span class="hlt">rate</span> testing of polymeric materials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gorwade, C. V.; Alghamdi, A. S.; Ashcroft, I. A.; Silberschmidt, V. V.; Song, M.</p> <p>2012-08-01</p> <p>Advanced polymer materials are finding an increasing range of industrial and defence applications. Ultra-high molecular weight polymers (UHMWPE) are already used in lightweight body armour because of their good impact resistance with light weight. However, a broader use of such materials is limited by the complexity of the manufacturing processes and the lack of experimental data on their behaviour and failure evolution under high-<span class="hlt">strain</span> <span class="hlt">rate</span> loading conditions. The current study deals with an investigation of the internal heat generation during tensile of UHMWPE. A 3D finite element (FE) model of the tensile test is developed and validated the with experimental work. An elastic-plastic material model is used with adiabatic heat generation. The temperature and stresses obtained with FE analysis are found to be in a good agreement with the experimental results. The model can be used as a simple and cost <span class="hlt">effective</span> tool to predict the thermo-mechanical behaviour of UHMWPE part under various loading conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MSMSE..24d5013M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MSMSE..24d5013M"><span id="translatedtitle">Numerical implementation of a crystal plasticity model with dislocation transport for high <span class="hlt">strain</span> <span class="hlt">rate</span> applications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mayeur, Jason R.; Mourad, Hashem M.; Luscher, Darby J.; Hunter, Abigail; Kenamond, Mark A.</p> <p>2016-05-01</p> <p>This paper details a numerical implementation of a single crystal plasticity model with dislocation transport for high <span class="hlt">strain</span> <span class="hlt">rate</span> applications. Our primary motivation for developing the model is to study the influence of dislocation transport and conservation on the mesoscale response of metallic crystals under extreme thermo-mechanical loading conditions (e.g. shocks). To this end we have developed a single crystal plasticity theory (Luscher et al (2015)) that incorporates finite deformation kinematics, internal stress fields caused by the presence of geometrically necessary dislocation gradients, advection equations to model dislocation density transport and conservation, and constitutive equations appropriate for shock loading (equation of state, drag-limited dislocation velocity, etc). In the following, we outline a coupled finite element-finite volume framework for implementing the model physics, and demonstrate its capabilities in simulating the response of a [1 0 0] copper single crystal during a plate impact test. Additionally, we explore the <span class="hlt">effect</span> of varying certain model parameters (e.g. mesh density, finite volume update scheme) on the simulation results. Our results demonstrate that the model performs as intended and establishes a baseline of understanding that can be leveraged as we extend the model to incorporate additional and/or refined physics and move toward a multi-dimensional implementation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JMEP...25.4959J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JMEP...25.4959J"><span id="translatedtitle">The Dynamic Tensile Behavior of Railway Wheel Steel at High <span class="hlt">Strain</span> <span class="hlt">Rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jing, Lin; Han, Liangliang; Zhao, Longmao; Zhang, Ying</p> <p>2016-11-01</p> <p>The dynamic tensile tests on D1 railway wheel steel at high <span class="hlt">strain</span> <span class="hlt">rates</span> were conducted using a split Hopkinson tensile bar (SHTB) apparatus, compared to quasi-static tests. Three different types of specimens, which were machined from three different positions (i.e., the rim, web and hub) of a railway wheel, were prepared and examined. The rim specimens were checked to have a higher yield stress and ultimate tensile strength than those web and hub specimens under both quasi-static and dynamic loadings, and the railway wheel steel was demonstrated to be <span class="hlt">strain</span> <span class="hlt">rate</span> dependent in dynamic tension. The dynamic tensile fracture surfaces of all the wheel steel specimens are cup-cone-shaped morphology on a macroscopic scale and with the quasi-ductile fracture features on the microscopic scale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EPJWC..2605003C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EPJWC..2605003C"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> behaviour of multi-phase and complex-phase steels for automotive applications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cadoni, E.; Singh, N. K.; Singha, M. K.; Gupta, N. K.</p> <p>2012-08-01</p> <p>A combined study on the mechanical behaviour of multi-phase 800 high yield strength steel (MP800HY) and complex-phase 800 steel (CP800) is carried out under tensile loads in the <span class="hlt">strain</span> <span class="hlt">rate</span> range from 0.001s-1 to 750s-1. Quasi-static (0.001s-1) tests are performed on electromechanical machine, whereas, medium (5s-1 and 25s-1) and high <span class="hlt">strain</span> <span class="hlt">rate</span> (250s-1, 500s-1 and 750s-1) experiments are conducted on hydro-pneumatic machine (HPM) and modified Hopkinson bar (MHB) setup respectively. The thermal softening behaviors of the materials are investigated at quasi-static condition and the materials' m-parameters of the existing Johnson-Cook model are imposed in authors' previous work. Thereafter, the predicted flow stress by Johnson-Cook model has been compared with the experimental results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/972425','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/972425"><span id="translatedtitle">High <span class="hlt">Strain-Rate</span> Response of High Purity Aluminum at Temperatures Approaching Melt</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Grunschel, S E; Clifton, R J; Jiao, T</p> <p>2010-01-28</p> <p>High-temperature, pressure-shear plate impact experiments were conducted to investigate the <span class="hlt">rate</span>-controlling mechanisms of the plastic response of high-purity aluminum at high <span class="hlt">strain</span> <span class="hlt">rates</span> (10{sup 6} s{sup -1}) and at temperatures approaching melt. Since the melting temperature of aluminum is pressure dependent, and a typical pressure-shear plate impact experiment subjects the sample to large pressures (2 GPa-7 GPa), a pressure-release type experiment was used to reduce the pressure in order to measure the shearing resistance at temperatures up to 95% of the current melting temperature. The measured shearing resistance was remarkably large (50 MPa at a shear <span class="hlt">strain</span> of 2.5) for temperatures this near melt. Numerical simulations conducted using a version of the Nemat-Nasser/Isaacs constitutive equation, modified to model the mechanism of geometric softening, appear to capture adequately the hardening/softening behavior observed experimentally.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013DokPh..58..362K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013DokPh..58..362K"><span id="translatedtitle">Integrability of the equilibrium and compatibility equations for a viscoplastic medium with negative <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Keller, I. E.</p> <p>2013-08-01</p> <p>The equilibrium and compatibility equations for viscoplastic medium with an arbitrary material function relating the stress intensity to the <span class="hlt">strain</span> <span class="hlt">rate</span> intensity is considered. A general form of the function ensuring complete integrability of two-dimensional equations has been found. The obtained function has an N-shaped (spinodal) graph and in particular cases corresponds to a linearly viscous liquid and perfectly plastic solid. A change of the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity sign corresponds to a change in the type of the system and passing over the discontinuity line in a solid. The obtained function provides decoupling of the operator in a pair of two-dimensional subspaces where the equations are exactly linearized. The results of this study allows us to extend the class of integrable problems to so-called "active materials" (or "materials with internal dynamics"), which have aroused considerable interest.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3284136','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3284136"><span id="translatedtitle">Biologically inspired crack delocalization in a high <span class="hlt">strain-rate</span> environment</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Knipprath, Christian; Bond, Ian P.; Trask, Richard S.</p> <p>2012-01-01</p> <p>Biological materials possess unique and desirable energy-absorbing mechanisms and structural characteristics worthy of consideration by engineers. For example, high levels of energy dissipation at low <span class="hlt">strain</span> <span class="hlt">rates</span> via triggering of crack delocalization combined with interfacial hardening by platelet interlocking are observed in brittle materials such as nacre, the iridescent material in seashells. Such behaviours find no analogy in current engineering materials. The potential to mimic such toughening mechanisms on different length scales now exists, but the question concerning their suitability under dynamic loading conditions and whether these mechanisms retain their energy-absorbing potential is unclear. This paper investigates the kinematic behaviour of an ‘engineered’ nacre-like structure within a high <span class="hlt">strain-rate</span> environment. A finite-element (FE) model was developed which incorporates the pertinent biological design features. A parametric study was carried out focusing on (i) the use of an overlapping discontinuous tile arrangement for crack delocalization and (ii) application of tile waviness (interfacial hardening) for improved post-damage behaviour. With respect to the material properties, the model allows the permutation and combination of a variety of different material datasets. The advantage of such a discontinuous material shows notable improvements in sustaining high <span class="hlt">strain-rate</span> deformation relative to an equivalent continuous morphology. In the case of the continuous material, the shockwaves propagating through the material lead to localized failure while complex shockwave patterns are observed in the discontinuous flat tile arrangement, arising from platelet interlocking. The influence of the matrix properties on impact performance is investigated by varying the dominant material parameters. The results indicate a deceleration of the impactor velocity, thus delaying back face nodal displacement. A final series of FE models considered the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008RuMet2008..164A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008RuMet2008..164A"><span id="translatedtitle">Determination of the ductile-brittle transition temperature from the microplastic-<span class="hlt">strain</span> <span class="hlt">rate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Andreev, A. K.; Solntsev, Yu. P.</p> <p>2008-04-01</p> <p>The possibility of the determination of the tendency of cast and deformed steels to brittle fracture using the temperature dependence of the small-plastic-<span class="hlt">strain</span> <span class="hlt">rate</span> is studied. The temperature corresponding to the maximum in this curve is found to indicate an abrupt decrease in the steel plasticity, which makes it possible to interpret it as the ductile-brittle transition temperature depending only on the structure of a material.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA527680','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA527680"><span id="translatedtitle"><span class="hlt">Strain-Rate</span> Dependency of Strength of Soft Marine Deposits of the Gulf of Mexico</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2010-06-01</p> <p>abstract number: 090612-057 <span class="hlt">Strain-rate</span> dependency of strength of soft marine deposits of the Gulf of Mexico Andrei Abelev and Philip Valent...from the Gulf of Mexico . The vane test may not always be the most accurate method of describing the undrained shear strength, mainly because it...deposits of the Gulf of Mexico 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1814830B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1814830B"><span id="translatedtitle">Some influences of rock strength and <span class="hlt">strain</span> <span class="hlt">rate</span> on propagation of rock avalanches</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bowman, Elisabeth; Rait, Kim</p> <p>2016-04-01</p> <p>Rock avalanches are extreme and destructive mass movements in which large volumes of rock (typically >1 million cubic metres) travel at high speeds, covering large distances, and the occurrence of which is highly unpredictable. The "size <span class="hlt">effect</span>" in rock avalanches, whereby those with larger volumes produce greater spreading efficiency (as defined by an increase in normalised runout) or lower farboschung angle (defined as the tangent of the ratio of fall height to runout length), is well known. Studies have shown that rock strength is a controlling factor in the mobility of rock avalanches - that is, mass movements involving lower strength rock are generally found to produce greater mobility as evidenced by the spread of deposits or low farboschung angle. However, there are conflicting ideas as to how and why this influence is manifested. This paper discusses different theories of rock comminution in light of numerical simulations of rock clasts undergoing normal and shear induced loading, experimental work on rock avalanche behaviour, and dynamic fracture mechanics. In doing so, we introduce the idea of thresholds of <span class="hlt">strain</span> <span class="hlt">rate</span> for the production of dynamic fragmentation (as opposed to pseudo-static clast crushing) that are based, inter alia, on static rock strength. To do this, we refer to data from physical models using rock analogue materials, field data on chalk cliff collapses, and field statistics from documented rock avalanches. The roles of normal and shear loading and loading <span class="hlt">rate</span> within a rock avalanche are examined numerically using 3D Discrete Element Method models of rock clasts loaded to failure. Results may help to reconcile the observations that large rock avalanches in stronger materials tend not to fragment as much as those in weaker materials and also possess lower mobility, while small cliff collapses (typically > 1000 cubic metres) in weak chalk can exhibit rock avalanche-like behaviour at much smaller volumes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.2358A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.2358A"><span id="translatedtitle">GNSS <span class="hlt">strain</span> <span class="hlt">rate</span> patterns and their application to investigate geodynamical credibility of the GNSS velocities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Araszkiewicz, Andrzej; Figurski, Mariusz</p> <p>2015-04-01</p> <p>The potential that lies in the use of GNSS measurements for crustal deformation studies have already noticed in the beginning of the first of such a system (GPS). Today thanks to the development of satellite positioning techniques it is possible to detect displacement on the Earth surface with an accuracy less than 1 cm. With long-term observations we can determine the velocities even more accurately. Growing demand in the last years for GNSS applications, both for scientific and civil use, meant that new networks of the reference stations were created. Such a dense GNSS networks allow to conduct research in the field of crust deformation at a higher spatial resolution than before. In Europe most of the research focuses on Mediterranean regions, where we can monitor events resulting from the tectonic plates collision. But even in Central Europe we can see <span class="hlt">effect</span> of Africa push. In our research we focused on Polish territory, where in the past 5 years a nearly 300 reference stations were established. With minimal movements that have been observed in Poland, a key issue in this type of research is to determine the geodynamic reliability of the estimated stations velocities. While the long-term observations enable us to determine the very accurate velocities, it hard to indicate how reliably they reflect actual tectonic movements is. In this paper we proposed a method for testing the reliability of stations velocities based on the <span class="hlt">strain</span> <span class="hlt">rate</span> field analysis. The method is based on the analysis of the distribution of the <span class="hlt">rate</span> of deformation tensor components obtained for triangular elements built on the basis of assessed station. The paper presents the results of numerical simulations and initial use of the method for the Polish network of reference stations: ASG-EUPOS</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19830024945','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19830024945"><span id="translatedtitle"><span class="hlt">Effect</span> of <span class="hlt">strain</span> isolator pad modulus on inplane <span class="hlt">strain</span> in Shuttle Orbiter thermal protection system tiles</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sawyer, J. W.</p> <p>1983-01-01</p> <p>The thermal protection system used on the Space Shuttle orbiter to determine <span class="hlt">strains</span> in the reusable surface insulation tiles under simulated flight loads was investigated. The <span class="hlt">effects</span> of changes in the <span class="hlt">strain</span> isolator pad (SIP) moduli on the <span class="hlt">strains</span> in the tile were evaluated. To analyze the SIP/tile system, it was necessary to conduct tests to determine inplane tension and compression modulus and inplane failure <span class="hlt">strain</span> for the densified layer of the tiles. It is shown that densification of the LI-900 tile material increases the modulus by a factor of 6 to 10 and reduces the failure <span class="hlt">strain</span> by about 50%. It is indicated that the inplane <span class="hlt">strain</span> levels in the Shuttle tiles in the highly loaded regions are approximately 2 orders of magnitude lower than the failure <span class="hlt">strain</span> of the material. It is concluded that most of the LI-900 tiles on the Shuttle could be mounted on a SIP with tensile and shear stiffnesses 10 times those of the present SIP without inplane <span class="hlt">strain</span> failure in the tile.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70160311','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70160311"><span id="translatedtitle">A fault-based model for crustal deformation, fault slip-<span class="hlt">rates</span> and off-fault <span class="hlt">strain</span> <span class="hlt">rate</span> in California</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Zeng, Yuehua; Shen, Zheng-Kang</p> <p>2016-01-01</p> <p>We invert Global Positioning System (GPS) velocity data to estimate fault slip <span class="hlt">rates</span> in California using a fault‐based crustal deformation model with geologic constraints. The model assumes buried elastic dislocations across the region using Uniform California Earthquake Rupture Forecast Version 3 (UCERF3) fault geometries. New GPS velocity and geologic slip‐<span class="hlt">rate</span> data were compiled by the UCERF3 deformation working group. The result of least‐squares inversion shows that the San Andreas fault slips at 19–22  mm/yr along Santa Cruz to the North Coast, 25–28  mm/yr along the central California creeping segment to the Carrizo Plain, 20–22  mm/yr along the Mojave, and 20–24  mm/yr along the Coachella to the Imperial Valley. Modeled slip <span class="hlt">rates</span> are 7–16  mm/yr lower than the preferred geologic <span class="hlt">rates</span> from the central California creeping section to the San Bernardino North section. For the Bartlett Springs section, fault slip <span class="hlt">rates</span> of 7–9  mm/yr fall within the geologic bounds but are twice the preferred geologic <span class="hlt">rates</span>. For the central and eastern Garlock, inverted slip <span class="hlt">rates</span> of 7.5 and 4.9  mm/yr, respectively, match closely with the geologic <span class="hlt">rates</span>. For the western Garlock, however, our result suggests a low slip <span class="hlt">rate</span> of 1.7  mm/yr. Along the eastern California shear zone and southern Walker Lane, our model shows a cumulative slip <span class="hlt">rate</span> of 6.2–6.9  mm/yr across its east–west transects, which is ∼1  mm/yr increase of the geologic estimates. For the off‐coast faults of central California, from Hosgri to San Gregorio, fault slips are modeled at 1–5  mm/yr, similar to the lower geologic bounds. For the off‐fault deformation, the total moment <span class="hlt">rate</span> amounts to 0.88×1019  N·m/yr, with fast <span class="hlt">straining</span> regions found around the Mendocino triple junction, Transverse Ranges and Garlock fault zones, Landers and Brawley seismic zones, and farther south. The overall California moment <span class="hlt">rate</span> is 2.76×1019</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvF...1f4405F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvF...1f4405F"><span id="translatedtitle">Scale dependence of the alignment between <span class="hlt">strain</span> <span class="hlt">rate</span> and rotation in turbulent shear flow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fiscaletti, D.; Elsinga, G. E.; Attili, A.; Bisetti, F.; Buxton, O. R. H.</p> <p>2016-10-01</p> <p>The scale dependence of the statistical alignment tendencies of the eigenvectors of the <span class="hlt">strain-rate</span> tensor ei, with the vorticity vector ω , is examined in the self-preserving region of a planar turbulent mixing layer. Data from a direct numerical simulation are filtered at various length scales and the probability density functions of the magnitude of the alignment cosines between the two unit vectors | ei.ω ̂| are examined. It is observed that the alignment tendencies are insensitive to the concurrent large-scale velocity fluctuations, but are quantitatively affected by the nature of the concurrent large-scale velocity-gradient fluctuations. It is confirmed that the small-scale (local) vorticity vector is preferentially aligned in parallel with the large-scale (background) extensive <span class="hlt">strain-rate</span> eigenvector e1, in contrast to the global tendency for ω to be aligned in parallel with the intermediate <span class="hlt">strain-rate</span> eigenvector [Hamlington et al., Phys. Fluids 20, 111703 (2008), 10.1063/1.3021055]. When only data from regions of the flow that exhibit strong swirling are included, the so-called high-enstrophy worms, the alignment tendencies are exaggerated with respect to the global picture. These findings support the notion that the production of enstrophy, responsible for a net cascade of turbulent kinetic energy from large scales to small scales, is driven by vorticity stretching due to the preferential parallel alignment between ω and nonlocal e1 and that the strongly swirling worms are kinematically significant to this process.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3982653','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3982653"><span id="translatedtitle">Hopkinson bar techniques for the intermediate <span class="hlt">strain</span> <span class="hlt">rate</span> testing of bovine cortical bone</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Cloete, T. J.; Paul, G.; Ismail, E. B.</p> <p>2014-01-01</p> <p>Detailed knowledge of the dynamic viscoelastic properties of bone is required to understand the mechanisms of macroscopic bone fracture in humans, and other terrestrial mammals, during impact loading events (e.g. falls, vehicle accidents, etc.). While the dynamic response of bone has been studied for several decades, high-quality data remain limited, and it is only within the last decade that techniques for conducting dynamic compression tests on bone at near-constant <span class="hlt">strain</span> <span class="hlt">rates</span> have been developed. Furthermore, there appears to be a lack of published bone data in the intermediate <span class="hlt">strain</span> <span class="hlt">rate</span> (ISR) range (i.e. 1–100 s−1), which represents a regime in which many dynamic bone fractures occur. In this paper, preliminary results for the dynamic compression of bovine cortical bone in the ISR regime are presented. The results are obtained using two Hopkinson-bar-related techniques, namely the conventional split Hopkinson bar arrangement incorporating a novel cone-in-tube striker design, and the recently developed wedge bar apparatus. The experimental results show a rapid transition in the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitive behaviour of bovine cortical bone in the ISR range. Finally, a new viscoelastic model is proposed that captures the observed transition behaviour. PMID:24711493</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24711493','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24711493"><span id="translatedtitle">Hopkinson bar techniques for the intermediate <span class="hlt">strain</span> <span class="hlt">rate</span> testing of bovine cortical bone.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cloete, T J; Paul, G; Ismail, E B</p> <p>2014-05-13</p> <p>Detailed knowledge of the dynamic viscoelastic properties of bone is required to understand the mechanisms of macroscopic bone fracture in humans, and other terrestrial mammals, during impact loading events (e.g. falls, vehicle accidents, etc.). While the dynamic response of bone has been studied for several decades, high-quality data remain limited, and it is only within the last decade that techniques for conducting dynamic compression tests on bone at near-constant <span class="hlt">strain</span> <span class="hlt">rates</span> have been developed. Furthermore, there appears to be a lack of published bone data in the intermediate <span class="hlt">strain</span> <span class="hlt">rate</span> (ISR) range (i.e. 1-100 s(-1)), which represents a regime in which many dynamic bone fractures occur. In this paper, preliminary results for the dynamic compression of bovine cortical bone in the ISR regime are presented. The results are obtained using two Hopkinson-bar-related techniques, namely the conventional split Hopkinson bar arrangement incorporating a novel cone-in-tube striker design, and the recently developed wedge bar apparatus. The experimental results show a rapid transition in the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitive behaviour of bovine cortical bone in the ISR range. Finally, a new viscoelastic model is proposed that captures the observed transition behaviour.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/936793','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/936793"><span id="translatedtitle">HIGH-<span class="hlt">STRAIN</span> <span class="hlt">RATE</span> RESPONSE OF ULTRA-FINE GRAINED COPPER: EXPERIMENTS AND ANALYSIS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mishra, Anuj; Kad, Bimal; Martin, Morgana; Thadhani, Naresh; Kenik, Edward A; Myers, Marc A.</p> <p>2008-07-01</p> <p>The high-<span class="hlt">strain</span> <span class="hlt">rate</span> response of ultra-fine grained (UFG) copper processed by Equal Channel Angular Pressing (ECAP) was characterized by reverse Taylor impact and Hopkinson-bar experiments. Two types of copper samples are tested using Hopkinson bar: (a) cylindrical samples to investigate the response at high <span class="hlt">strain-rates</span>,(b) hat shaped samples to compare the shear band characteristics in UFG copper with the ones that have been studied in coarse grained samples. This can be attributed to the high <span class="hlt">strain-rate</span> sensitivity of the fine grained FCC metals. Upon impact, the samples were found to undergo heat induced static recrystallization at a calculated temperature of 360K, indicating that the UFG copper is thermally unstable. Reverse Taylor tests were conducted on as-received OFHC Cu rod and ECAP specimens with sequential ECAP passes (2 and 8). The dynamic deformations of the samples are modeled using AUTODYN-2D and a modified Johnson-Cook constitutive equation was found to capture the dynamic response. Similar to the compression test results, the impacted front of the samples were found to recrystallize extensively and preferentially.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22217786','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22217786"><span id="translatedtitle">Ultrahigh <span class="hlt">strain-rate</span> bending of copper nanopillars with laser-generated shock waves</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Colorado, H. A.; Navarro, A.; Prikhodko, S. V.; Yang, J. M.; Ghoniem, N.; Gupta, V.</p> <p>2013-12-21</p> <p>An experimental study to bend FIB-prepared cantilevered single crystal Cu nanopillars of several hundred nanometers in diameter and length at ultrahigh <span class="hlt">strain</span> <span class="hlt">rate</span> is presented. The deformation is induced by laser-generated stress waves, resulting in local <span class="hlt">strain</span> <span class="hlt">rates</span> exceeding 10{sup 7} s{sup −1}. Loading of nano-scale Cu structures at these extremely short loading times shows unique deformation characteristics. At a nominal stress value of 297 MPa, TEM examination along with selected area electron diffraction characterization revealed that twins within the unshocked Cu pillars interacted with dislocations that nucleated from free surfaces of the pillars to form new subgrain boundaries. MD simulation results were found to be consistent with the very low values of the stress required for dislocation activation and nucleation because of the extremely high surface area to volume ratio of the nanopillars. Specifically, simulations show that the stress required to nucleate dislocations at these ultrahigh <span class="hlt">strain</span> <span class="hlt">rates</span> is about one order of magnitude smaller than typical values required for homogeneous nucleation of dislocation loops in bulk copper single crystals under quasi-static conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/361737','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/361737"><span id="translatedtitle">Severe plastic deformation processing and high <span class="hlt">strain</span> <span class="hlt">rate</span> superplasticity in an aluminum matrix composite</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mishra, R.S.; McFadden, S.X.; Mukherjee, A.K.; Valiev, R.Z.; Islamgaliev, R.K.</p> <p>1999-04-23</p> <p>Metal matrix composites possess an attractive set of properties for structural applications. For example, reinforcement of conventional aluminum alloys with second phase ceramic particulates increases the stiffness, high temperature strength, etc. A drawback of ceramic phase reinforcement is that it makes machining of components difficult. Superplastic forming is quite attractive for hard-to-machine materials like composites. A number of aluminum matrix composites exhibit superplasticity. The most attractive feature of superplasticity in aluminum matrix composite is the high <span class="hlt">strain</span> <span class="hlt">rate</span> (10{sup {minus}2}--10{sup 1} s{sup {minus}1}) for optimum ductility. This is significantly higher than the optimum superplastic <span class="hlt">strain</span> <span class="hlt">rates</span> of 10{sup {minus}4}--10{sup {minus}3} s{sup {minus}1} in conventional fine grained alloys. The optimum superplasticity in aluminum matrix composites is influenced by the thermo-mechanical processing. In the last five years or so, a number of aluminum alloys have been processes by severe plastic deformation (SePD). Severe plastic deformation processing leads to ultrafine grained aluminum alloys with attractive superplastic properties. In this short paper the authors report on successful processing of an ultrafine grained aluminum matrix composite by severe plastic deformation technique. The SePD processes 2009 Al-SiC{sub 2} composite exhibits high <span class="hlt">strain</span> <span class="hlt">rate</span> superplasticity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3942497','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3942497"><span id="translatedtitle">The <span class="hlt">Effect</span> of Ivermectin in Seven <span class="hlt">Strains</span> of Aedes aegypti (Diptera: Culicidae) Including a Genetically Diverse Laboratory <span class="hlt">Strain</span> and Three Permethrin Resistant <span class="hlt">Strains</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Deus, K. M.; Saavedra-rodriguez, K.; Butters, M. P.; Black, W. C.; Foy, B. D.</p> <p>2014-01-01</p> <p>Seven different <span class="hlt">strains</span> of Aedes aegypti (L.), including a genetically diverse laboratory <span class="hlt">strain</span>, three laboratory-selected permethrin-resistant <span class="hlt">strains</span>, a standard reference <span class="hlt">strain</span>, and two recently colonized <span class="hlt">strains</span> were fed on human blood containing various concentrations of ivermectin. Ivermectin reduced adult survival, fecundity, and hatch <span class="hlt">rate</span> of eggs laid by ivermectin-treated adults in all seven <span class="hlt">strains</span>. The LC50 of ivermectin for adults and the concentration that prevented 50% of eggs from hatching was calculated for all <span class="hlt">strains</span>. Considerable variation in adult survival after an ivermectin-bloodmeal occurred among <span class="hlt">strains</span>, and all three permethrin-resistant <span class="hlt">strains</span> were significantly less susceptible to ivermectin than the standard reference <span class="hlt">strain</span>. The hatch <span class="hlt">rate</span> after an ivermectin bloodmeal was less variable among <span class="hlt">strains</span>, and only one of the permethrin-resistant <span class="hlt">strains</span> differed significantly from the standard reference <span class="hlt">strain</span>. Our studies suggest that ivermectin induces adult mortality and decreases the hatch <span class="hlt">rate</span> of eggs through different mechanisms. A correlation analysis of log-transformed LC50 among <span class="hlt">strains</span> suggests that permethrin and ivermectin cross-resistance may occur. PMID:22493855</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JAP...121g5302A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JAP...121g5302A"><span id="translatedtitle"><span class="hlt">Effect</span> of asymmetric <span class="hlt">strain</span> relaxation on dislocation relaxation processes in heteroepitaxial semiconductors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Andersen, D.; Hull, R.</p> <p>2017-02-01</p> <p>The <span class="hlt">effect</span> of asymmetric interfacial <span class="hlt">strain</span> configurations upon the generation of misfit dislocation arrays in lattice mismatched epitaxy is considered. For example, elastic <span class="hlt">strain</span> relaxation for Si1-xGex/Si(110) films is uniaxial, assuming glide on {111} planes as expected for the diamond cubic system, which leads to asymmetric <span class="hlt">strain</span> relief. Here, we extend our previously developed relaxation model for generation of dislocation arrays in SiGe/Si, by accounting for how the different energetics of asymmetrically <span class="hlt">strained</span> films affect the kinetics of the relaxation process. Similarly, non-polar III-nitride epitaxial films have asymmetric <span class="hlt">strain</span> from the outset of growth due to the different c/a lattice parameter ratios. In both systems, the asymmetric <span class="hlt">strain</span> is represented by an additional term in the misfit dislocation applied stress equation. In SiGe/Si(110), a simple elasticity analysis of the <span class="hlt">strain</span> produced by the uniaxial array of dislocations predicts that the relaxation orthogonal to the dislocation line direction occurs at a faster <span class="hlt">rate</span> than predicted by purely biaxial <span class="hlt">strain</span> relief due to the contributions of the <span class="hlt">strain</span> parallel to the dislocations. This difference is because the <span class="hlt">strain</span> parallel to the dislocation line directions continues to resolve stress onto the misfit dislocations even as the orthogonal <span class="hlt">strain</span> is minimized. As a result, the minimum <span class="hlt">strain</span> energy is predicted to occur for a dislocation spacing, which produces tensile layer <span class="hlt">strain</span> in the orthogonal direction. Such tensile <span class="hlt">strain</span> may modify the (opto)electronic properties of a Si, Ge, or GeSi epilayer but is only predicted to occur for advanced stages of relaxation. These asymmetric derivations are applicable to any thin film system where <span class="hlt">strain</span> is not strictly biaxial.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22261767','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22261767"><span id="translatedtitle"><span class="hlt">Effect</span> of <span class="hlt">strain</span> on thermoelectric power of suspended graphene</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Vaidya, R. G.; Sankeshwar, N. S. Mulimani, B. G.</p> <p>2013-12-04</p> <p>Thermoelectric power, S, of suspended graphene in the presence of <span class="hlt">strain</span> is investigated. The electrons are considered to be scattered by in-plane and flexural phonons. The dominant contribution to S of non-<span class="hlt">strained</span> and <span class="hlt">strained</span> suspended graphene (SG) is found to be from the phonon drag component, S{sub g} for T < 90K. For T > 150 K contribution from diffusion thermopower becomes important. The <span class="hlt">effect</span> of <span class="hlt">strain</span> is found to be suppress S{sub d} and to alter its behavior, the <span class="hlt">effect</span> being larger at higher temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25465570','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25465570"><span id="translatedtitle">Short communication: Antiproliferative <span class="hlt">effect</span> of 8 different Lactobacillus <span class="hlt">strains</span> on K562 cells.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tuo, Yanfeng; Jiang, Shujuan; Qian, Fang; Mu, Guangqing; Liu, Peng; Guo, Yuanji; Ma, Changlu</p> <p>2015-01-01</p> <p>Some <span class="hlt">strains</span> of Lactobacillus genus have antiproliferative activities against cancer cells. However, until now, the exact effector molecules of Lactobacillus <span class="hlt">strains</span> with anticancer activity have not been identified. The aim of the present study was to explore which fraction of the Lactobacillus cells exerts the highest antiproliferative <span class="hlt">effect</span>. For this purpose, the heat-killed bacterial cells, bacterial cell wall extract, and genomic DNA of 8 Lactobacillus <span class="hlt">strains</span> were prepared to assess their antiproliferative activities against human myeloid leukemia cell lines K562. The heat-killed bacterial cells of the 8 lactobacilli <span class="hlt">strains</span> exerted antiproliferative <span class="hlt">effect</span> on K562 cells, and the inhibition <span class="hlt">rates</span> exerted by the heat-killed bacterial cells of the <span class="hlt">strains</span> G15AL, M5AL, SB31AL, SB5AL, and T3AL were significantly higher than those exerted by the cell walls and genomic DNA of the <span class="hlt">strains</span>. The bacterial DNA of G15AL exerted higher antiproliferative <span class="hlt">effect</span> on K562 cells. The exact effector molecules and the <span class="hlt">effect</span> mechanism of the <span class="hlt">strains</span> should be further explored for the application of these <span class="hlt">strains</span> as probiotic <span class="hlt">strains</span> or bioactive probiotic molecules.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19910013931','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19910013931"><span id="translatedtitle"><span class="hlt">Rate</span> dependent stress-<span class="hlt">strain</span> behavior of advanced polymer matrix composites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gates, Thomas S.</p> <p>1991-01-01</p> <p>The formulation of an elastic/viscoplastic constitutive model which was used to predict the measured behavior of graphite/thermoplastic and graphite/bismaleimide composite materials at elevated temperature is described. The model incorporates the concepts of overstress and <span class="hlt">effective</span> <span class="hlt">strain/strain</span> to provide a simple formulation which was able to account for material behavior under monotonic tension or compression loads over a temperature range of 23 to 200 C. Observed behavior such as stress relaxation and steady state creep, in off-axis tension and compression tests, were predicted by the model. Material constants required by the model were extracted from simple off-axis test data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.8353Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.8353Z"><span id="translatedtitle">High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Testing of Rocks using a Split-Hopkinson-Pressure Bar</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zwiessler, Ruprecht; Kenkmann, Thomas; Poelchau, Michael; Nau, Siegfried; Hess, Sebastian</p> <p>2016-04-01</p> <p>Dynamic mechanical testing of rocks is important to define the onset of <span class="hlt">rate</span> dependency of brittle failure. The <span class="hlt">strain</span> <span class="hlt">rate</span> dependency occurs through the propagation velocity limit (Rayleigh wave speed) of cracks and their reduced ability to coalesce, which, in turn, significantly increases the strength of the rock. We use a newly developed pressurized air driven Split-Hopkinson-Pressure Bar (SHPB), that is specifically designed for the investigation of high <span class="hlt">strain</span> <span class="hlt">rate</span> testing of rocks, consisting of several 10 to 50 cm long strikers and bar components of 50 mm in diameter and 2.5 meters in length each. The whole set up, composed of striker, incident- and transmission bar is available in aluminum, titanium and maraging steel to minimize the acoustic impedance contrast, determined by the change of density and speed of sound, to the specific rock of investigation. Dynamic mechanical parameters are obtained in compression as well as in spallation configuration, covering a wide spectrum from intermediate to high <span class="hlt">strain</span> <span class="hlt">rates</span> (100-103 s-1). In SHPB experiments [1] one-dimensional longitudinal compressive pulses of diverse shapes and lengths - formed with pulse shapers - are used to generate a variety of loading histories under 1D states of stress in cylindrical rock samples, in order to measure the respective stress-<span class="hlt">strain</span> response at specific <span class="hlt">strain</span> <span class="hlt">rates</span>. Subsequent microstructural analysis of the deformed samples is aimed at quantification fracture orientation, fracture pattern, fracture density, and fracture surface properties as a function of the loading <span class="hlt">rate</span>. Linking mechanical and microstructural data to natural dynamic deformation processes has relevance for the understanding of earthquakes, landslides, impacts, and has several rock engineering applications. For instance, experiments on dynamic fragmentation help to unravel super-shear rupture events that pervasively pulverize rocks up to several hundred meters from the fault core [2, 3, 4]. The dynamic, <span class="hlt">strain</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AIPC.1219..337T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AIPC.1219..337T"><span id="translatedtitle">Torsion <span class="hlt">Strain</span> <span class="hlt">Effects</span> on Critical Currents of Hts Superconducting Tapes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takayasu, Makoto; Minervini, Joseph V.; Bromberg, Leslie</p> <p>2010-04-01</p> <p>A torsional twist <span class="hlt">strain</span> <span class="hlt">effect</span> on the critical current of a thin HTS tape has been found to be well described by a longitudinal <span class="hlt">strain</span> model taking into account the internal shortening compressive <span class="hlt">strains</span> accompanied with the tensile longitudinal <span class="hlt">strains</span> due to a torsional twist. The critical current of a twisted tape is given by the integration of the critical current densities corresponding to the <span class="hlt">strain</span> distribution over the tape cross-section using axial <span class="hlt">strain</span> data of the tape. The model is supported with experimental results of YBCO and BSCCO-2223 tapes. It has been also found that torsional twisting <span class="hlt">effects</span> on the critical currents of a tape composing of the conventional lapped-tape cable and the twisted stacked-tape cable are described by the same equation as that of a twisted single tape.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3345833','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3345833"><span id="translatedtitle">GPS Velocity and <span class="hlt">Strain</span> <span class="hlt">Rate</span> Fields in Southwest Anatolia from Repeated GPS Measurements</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Erdoğan, Saffet; Şahin, Muhammed; Tiryakioğlu, İbrahim; Gülal, Engin; Telli, Ali Kazım</p> <p>2009-01-01</p> <p>Southwestern Turkey is a tectonically active area. To determine kinematics and <span class="hlt">strain</span> distribution in this region, a GPS network of sixteen stations was established. We have used GPS velocity field data for southwest Anatolia from continuous measurements covering the period 2003 to 2006 to estimate current crustal deformation of this tectonically active region. GPS data were processed using GAMIT/GLOBK software and velocity and <span class="hlt">strain</span> <span class="hlt">rate</span> fields were estimated in the study area. The measurements showed velocities of 15–30 mm/yr toward the southwest and <span class="hlt">strain</span> values up to 0.28–8.23×10−8. Results showed that extension has been determined in the Burdur-Isparta region. In this study, all of <span class="hlt">strain</span> data reveal an extensional neotectonic regime through the northeast edge of the Isparta Angle despite the previously reported compressional neotectonic regime. Meanwhile, results showed some small differences relatively with the 2006 model of Reilinger et al. As a result, active tectonic movements, in agreement with earthquake fault plane solutions showed important activity. PMID:22573998</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PMM...116..385B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PMM...116..385B"><span id="translatedtitle">Mechanical and structural aspects of high-<span class="hlt">strain-rate</span> deformation of NiTi alloy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bragov, A. M.; Danilov, A. N.; Konstantinov, A. Yu.; Lomunov, A. K.; Motorin, A. S.; Razov, A. I.</p> <p>2015-04-01</p> <p>The mechanical behavior of the binary polycrystalline NiTi alloy with a quasi-equilibrium structure has been considered in the course of the high-<span class="hlt">strain-rate</span> extension in a temperature range of 20-300°C. The quasi-equilibrium structure, which is necessary to ensure the long-term stability of special properties of the alloy, was achieved using aging, after which both the forward and reverse martensitic transformations exhibited a multistage character and the phase composition at room temperature was characterized by the presence of R and B19' martensites. To separate the contributions that come from the equilibrium structure and from the high <span class="hlt">rate</span> of tension to the mechanical behavior of the alloy, a comparative analysis of the diagrams of high-<span class="hlt">strain-rate</span> and quasi-static tension has been performed. It has been shown that the action of several mechanisms of reversible deformation is determined by the specific features of the equilibrium structure, and the level of stresses at which these mechanisms are developed is controlled by the <span class="hlt">rate</span> of tension. The results of the X-ray diffraction study of the phase composition of the alloy samples after high-<span class="hlt">strain-rate</span> tension, which make it possible to conclude that the mechanical behavior of martensite and austenite upon the dynamic tension of the alloy is determined by the development of stress-induced R → B19', B2 → R, and B2 → B19' transformations and by the processes of the detwinning and reorientation of crystals of B19' martensite, are given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JAP...116u3507R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JAP...116u3507R"><span id="translatedtitle">Integrated experimental and computational studies of deformation of single crystal copper at high <span class="hlt">strain</span> <span class="hlt">rates</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Rawat, S.; Chandra, S.; Chavan, V. M.; Sharma, S.; Warrier, M.; Chaturvedi, S.; Patel, R. J.</p> <p>2014-12-01</p> <p>Quasi-static (0.0033 s-1) and dynamic (103 s-1) compression experiments were performed on single crystal copper along ⟨100⟩ and ⟨110⟩ directions and best-fit parameters for the Johnson-Cook (JC) material model, which is an important input to hydrodynamic simulations for shock induced fracture, have been obtained. The deformation of single crystal copper along the ⟨110⟩ direction showed high yield strength, more <span class="hlt">strain</span> hardening, and less <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity as compared to the ⟨100⟩ direction. Although the JC model at the macro-scale is easy to apply and describes a general response of material deformation, it lacks physical mechanisms that describe the influence of texture and initial orientation on the material response. Hence, a crystal plasticity model based on the theory of thermally activated motion of dislocations was used at the meso-scale, in which the evolution equations permit one to study and quantify the influence of initial orientation on the material response. Hardening parameters of the crystal plasticity model show less <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity along the ⟨110⟩ orientation as compared to the ⟨100⟩ orientation, as also shown by the JC model. Since the deformation process is inherently multiscale in nature, the shape changes observed in the experiments due to loading along ⟨100⟩ and ⟨110⟩ directions are also validated by molecular dynamics simulations at the nano-scale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JAP...112a4903W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JAP...112a4903W"><span id="translatedtitle">Dynamic compressive behavior of Pr-Nd alloy at high <span class="hlt">strain</span> <span class="hlt">rates</span> and temperatures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Huanran; Cai, Canyuan; Chen, Danian; Ma, Dongfang</p> <p>2012-07-01</p> <p>Based on compressive tests, static on 810 material test system and dynamic on the first compressive loading in split Hopkinson pressure bar (SHPB) tests for Pr-Nd alloy cylinder specimens at high <span class="hlt">strain</span> <span class="hlt">rates</span> and temperatures, this study determined a J-C type [G. R. Johnson and W. H. Cook, in Proceedings of Seventh International Symposium on Ballistics (The Hague, The Netherlands, 1983), pp. 541-547] compressive constitutive equation of Pr-Nd alloy. It was recorded by a high speed camera that the Pr-Nd alloy cylinder specimens fractured during the first compressive loading in SHPB tests at high <span class="hlt">strain</span> <span class="hlt">rates</span> and temperatures. From high speed camera images, the critical <span class="hlt">strains</span> of the dynamic shearing instability for Pr-Nd alloy in SHPB tests were determined, which were consistent with that estimated by using Batra and Wei's dynamic shearing instability criterion [R. C. Batra and Z. G. Wei, Int. J. Impact Eng. 34, 448 (2007)] and the determined compressive constitutive equation of Pr-Nd alloy. The transmitted and reflected pulses of SHPB tests for Pr-Nd alloy cylinder specimens computed with the determined compressive constitutive equation of Pr-Nd alloy and Batra and Wei's dynamic shearing instability criterion could be consistent with the experimental data. The fractured Pr-Nd alloy cylinder specimens of compressive tests were investigated by using 3D supper depth digital microscope and scanning electron microscope.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/619531','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/619531"><span id="translatedtitle">High <span class="hlt">strain</span> <span class="hlt">rate</span> superplasticity in an Al-Mg alloy containing scandium</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Komura, Shogo; Horita, Zenji; Nemoto, Minoru; Berbon, P.B.; Langdon, T.G.; Furukawa, Minoru</p> <p>1998-05-12</p> <p>Superplastic forming is a well-established industrial process for the fabrication of complex shapes in sheet metals. It has been suggested that it may be possible to achieve superplasticity at high <span class="hlt">strain</span> <span class="hlt">rates</span> in conventional materials by making a substantial reduction in the grain size. This may be achieved by using a process such as equal-channel angular (ECA) pressing, where the sample is subjected to intense plastic <span class="hlt">straining</span> in simple shear, because it is well established that ECA pressing leads to significant grain refinement in large-grained polycrystalline materials down to the submicrometer or even the nanometer level. High <span class="hlt">strain</span> <span class="hlt">rate</span> superplasticity (HSR SP) has been widely documented in a range of metal matrix composites, mechanically alloyed materials and in alloys fabricated using powder metallurgy procedures and very recently there was a report of HSR SP in commercial cast Al-based alloys after ECA pressing. The present investigation was initiated in order to evaluate the potential for achieving HSR SP in an Al-3% Mg alloy containing a scandium addition. Scandium was selected for use in this investigation because it is well established that dilute amounts of scandium in the Al-Mg system lead to a considerable enhancement in both the strength and the thermal stability of the material.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/571705','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/571705"><span id="translatedtitle"><span class="hlt">Strain</span> <span class="hlt">rate</span> sensitivity of mechanical properties and related thermal activation process in a two-phase {gamma} titanium aluminide</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lin, D.; Wang, Y.; Lin, Y.; Kim, Y.W.</p> <p>1997-12-31</p> <p>Tensile properties of a two-phase {gamma} titanium aluminide with duplex microstructure are tested under different <span class="hlt">strain</span> <span class="hlt">rates</span> from 5 {times} 10{sup {minus}5} to 5 {times} 10{sup {minus}3}s{sup {minus}1} at temperature from 1,123 K to 1,273 K. It is found that there exists approximate linear relationship between the flow stresses and the logarithm of the <span class="hlt">strain</span> <span class="hlt">rate</span> at different temperatures. The <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity can be explained by thermal activation theory, and dislocation climbing is identified as the <span class="hlt">rate</span> controlling mechanism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70027478','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70027478"><span id="translatedtitle">Interseismic <span class="hlt">strain</span> and rotation <span class="hlt">rates</span> in the northeast Mojave domain, eastern California</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Savage, J.C.; Svarc, J.L.; Prescott, II W.</p> <p>2004-01-01</p> <p>The northeast Mojave domain, a type locality for bookshelf faulting, is a region of east striking, left-lateral faults in the northeast comer of the Mojave block, a block otherwise dominated by ??N40??W striking, right-lateral faults. Paleomagnetic evidence suggests that blocks within the domain have rotated clockwise about a vertical axis as much as 60?? since 12.8 Ma [Schermer et al., 1996]. In 1994, and again in 2002, the U.S. Geological Survey surveyed an array of 14 geodetic monuments distributed across the northeast Mojave domain. The 2002 survey results were adjusted to remove the coseismic offsets imposed by the nearby Hector Mine earthquake (16 October 1999, Mw = 7.1). The adjusted deformation across the array appears to be uniform and can be approximated by the principal <span class="hlt">strain</span> <span class="hlt">rates</span> ??:1 = 28.9 ?? 9.1 N77.2??W ?? 4.8?? and ??2 = -48.2 ?? 8.9 N12.8??E ?? 4.8?? nstrain yr-1; extension reckoned positive, and quoted uncertainties are standard deviations. That <span class="hlt">strain</span> accumulation could be released by slip . on faults striking N32??W but not by bookshelf faulting on the east striking faults alone. The vertical axis rotation <span class="hlt">rate</span> of the northeast Mojave domain as a whole relative to fixed North America is 71.0 ?? 6.4 nrad yr-1 (4.07?? ?? 0.37?? Myr-1) clockwise, about twice the maximum tenser shear <span class="hlt">strain</span> <span class="hlt">rate</span>. The observed rotation <span class="hlt">rate</span> acting over 12.8 Myr would produce'a clockwise rotation of 52.1?? ?? 4.7??, exclusive of possible coseismic rotations. That rotation is in rough agreement with the paleomagnetic rotation accumulated in the individual fault blocks within the northeast Mojave domain since 12.8 Ma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012APS..MAR.D2005D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012APS..MAR.D2005D"><span id="translatedtitle">Directly probing the <span class="hlt">effect</span> of <span class="hlt">strain</span> on magnetic exchange interactions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dorr, Kathrin</p> <p>2012-02-01</p> <p>Thin films of transition metal oxides of the perovskite type ABO3 (B = 3d or 4d metal) have revealed abundant examples for <span class="hlt">strain</span>-driven changes of magnetic ordering. One most popular is the <span class="hlt">strain</span>-induced ferromagnetic ferroelectric state of otherwise antiferromagnetic paraelectric EuTiO3. Another promising example is the <span class="hlt">strain</span> control of orbital occupation and magnetic coupling at oxide interfaces of SrRuO3 with manganites. In spite of strong efforts, the theoretical treatment of magnetic exchange in complex oxides has remained a challenge, and experiments continue to show unpredicted / unexplained large <span class="hlt">effects</span> of the epitaxial <span class="hlt">strains</span> in films. In order to provide meaningful experimental data on <span class="hlt">strain</span> dependences, epitaxial thin films should be grown in various coherent <span class="hlt">strain</span> states on different substrates without changing anything but the <span class="hlt">strain</span>. This is inherently difficult: possible problems may arise from a <span class="hlt">strain</span>-dependent oxidation level or microstructure. As a complementary approach, the in-plane <span class="hlt">strain</span> of epitaxial oxide films can be controlled reversibly using a piezoelectric substrate, even though the accessible reversible <span class="hlt">strain</span> of 0.1 -- 0.2% is an order of magnitude smaller. In my talk, I will address reversible-<span class="hlt">strain</span> studies on La0.7Sr0.3MnO3, La1-xSrxCoO3 (x = 0, 0.2, 0.3) und SrRuO3 films, showing the <span class="hlt">strain</span> response of the magnetic Curie temperature, the magnetization and the electrical resistance and discussing the current understanding of the <span class="hlt">strain</span> <span class="hlt">effects</span> on magnetic ordering. In La0.8Sr0.2CoO3, a <span class="hlt">strain</span>-driven phase transition between ferromagnetic and spin-glass-like could be established by combining the piezoelectric substrate with a tuned buffer system providing varied as-grown <span class="hlt">strain</span> states. In SrRuO3, a tetragonal tensile <span class="hlt">strain</span> state shows a suppression of the ordered magnetic moment. Lattice parameters and symmetries of the films were determined by x-ray diffraction. It is noted that the atomic displacements (bond lengths and</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.T33A2650D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.T33A2650D"><span id="translatedtitle">Network estimation of noise in GPS data with implications for uncertainty in intraplate <span class="hlt">strain-rate</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dmitrieva, K.; Segall, P.</p> <p>2012-12-01</p> <p>Geological evidence suggests that large earthquakes strike the New Madrid Seismic Zone (NMSZ) on average every 500 years. However, continuous GPS observations spanning over a decade show little or possibly no <span class="hlt">strain</span> <span class="hlt">rate</span> in this region. The uncertainty in geodetically derived <span class="hlt">strain-rates</span> is dominated by time-dependent noise in GPS time series - typically modeled as power-law noise, including random walk and flicker noise. Hence a good understanding of GPS noise is essential for quantifying <span class="hlt">strain</span> <span class="hlt">rates</span> and their uncertainties in continental interiors. We develop a network noise estimator that is able to determine the time-dependent noise properties of GPS time series in regions of low deformation <span class="hlt">rates</span>. Specifically, we investigate spatial correlations of different components of the data. In our filtering approach we decompose the signal within a stable plate interior into a spatially coherent plate rotation (possibly plus post-glacial rebound) and noise. Currently the noise is a sum of flicker, random walk, and white noise. Assuming that there are no other signals in stable parts of the plate, we process all stations simultaneously use a Kalman filter to estimate the different components of the data. We use maximum likelihood estimation (MLE) to solve for the best fitting variance parameters in the noise model. Preliminary work using synthetic data shows that our method can recover even low levels of time-dependent noises in the data. We compare our network method with commonly used "baseline fit" MLE techniques by running both methods on sets of synthetic data with constant white and flicker noise, but varying random walk variance. Each method can determine flicker noise and white noise values well; however, the baseline fit fails to detect random walk if its magnitude is significantly lower than flicker noise. For example, for flicker noise of 2 mm/yr^0.25 and random walk of 0.38 mm/yr^0.5, the baseline fit finds no random walk, and yet our network approach</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890011915','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890011915"><span id="translatedtitle"><span class="hlt">Strain</span> energy release <span class="hlt">rate</span> as a function of temperature and preloading history utilizing the edge delamination fatique test method</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zimmerman, Richard S.; Adams, Donald F.</p> <p>1989-01-01</p> <p>Static laminate and tension-tension fatigue tests of IM7/8551-7 composite materials was performed. The Edge Delamination Test (EDT) was utilized to evaluate the temperature and preloading history <span class="hlt">effect</span> on the critical <span class="hlt">strain</span> energy release <span class="hlt">rate</span>. Static and fatigue testing was performed at room temperature and 180 F (82 C). Three preloading schemes were used to precondition fatigue test specimens prior to performing the normal tension-tension fatigue EDT testing. Computer software