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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. Strain rate effect in high-speed wire drawing process

    NASA Astrophysics Data System (ADS)

    He, S.; Van Houtte, P.; Van Bael, A.; Mei, F.; Sarban, A.; Boesman, P.; Galvez, F.; Atienza, J. M.

    2002-05-01

    This paper presents a study on the strain rate effect during high-speed wire drawing process by means of finite element simulation. Based on the quasistatic stresses obtained by normal tensile tests and dynamic stresses at high strain rates by split Hopkinson pressure bar tests, the wire drawing process was simulated for low carbon steel and high carbon steel. The results show that both the deformation process and the final properties of drawn wires are influenced by the strain rate.

  7. 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.

  8. Strain Rate Effects on the Mechanical Response of Polypropylene-Based Composites Deformed at Small Strains

    SciTech Connect

    Pessey, D.; Bahlouli, N.; Ahzi, Said; Khaleel, Mohammad A.

    2008-06-01

    The mechanical properties and response of two composites based polypropylene (PP) have been determined for small strains and for a range of strain rates in the quasi static domain. These two materials are the talc-filled and non-filled high impact PP. Uni-axial tensile tests were performed at different strain rates in order to characterize the mechanical response and the strain rate effect. Experimental results showed that both unfilled and talc-filled high impact polypropylene were sensitive to strain rate and have a non linear behavior even at relatively low strains. SEM analysis has been conducted to obtain a better comprehension of deformation mechanisms involved during loading by observations of the microstructure evolution. For each of these two materials, two existing modeling approaches are proposed. The first one is a three-parameter nonlinear constitutive model based on the experimental results. The second is a micromechanically-based approach for the elastic-viscoplastic behavior of the composite materials. The stress-strain curves predicted by these models are in fairly good agreement with our experimental results.

  9. 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.

  10. 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

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

    NASA Astrophysics Data System (ADS)

    Khan, Amnah; Proud, William

    2015-06-01

    The effects of varying strain rates and temperatures on the charge output and fracture of the piezoceramic PZT 95/5 have been investigated. The samples are studied in the temperature range of - 20° C to + 80° C ; a range of strain rates (10-4 s-1 to 10+3 s-1) is achieved using quasi-static loading equipment, drop weights and Split Hopkinson Pressure Bars. Stress-strain data is obtained, along with high-speed images, allowing the physical processes e.g. fracture, to be quantified. The Institute of Shock Physics acknowledges the support of AWE, Aldermaston, UK and Imperial College London.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Effect of Strain Rate on the Mechanical Behavior of Red Blood Cells Entering a Constriction

    NASA Astrophysics Data System (ADS)

    Mancuso, Jordan; Ristenpart, William

    2014-11-01

    Most work on the effect of hydrodynamic stress on red blood cells (RBCs) has focused on linear velocity profiles. Microfluidic devices have provided a means to examine the mechanical behavior of RBCs undergoing a sudden increase in shear stress at the entrance of a constriction, with previous work primarily focused on a fixed constriction taper angle and corresponding hydrodynamic strain rate. Here we investigate the effect of strain rate on the stretching dynamics exhibited by RBCs as they enter a microfluidic constriction. Systematic variations in the constriction taper angle allow the strain rate to be precisely tuned, and high speed video yields precise measurements of the corresponding RBC deformations. We demonstrate that maximal RBC stretching occurs at an intermediate constriction taper angle, despite the lower magnitude of the strain rate. We interpret the results in terms of the time integral of the elongational strain rate, and we discuss the implications for shear-induced mechanotransduction.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. Effects of Zr on the high strain rate superplasticity of 2124 Al

    SciTech Connect

    Nieh, T.G.; Wadsworth, J. )

    1993-05-01

    Many years ago, Nieh and Wadsworth, reported an observation that a 0.6wt%Zr-modified 2124 Al alloy, which has a fine grain size of about 1[mu]m, behaved superplastically at 475 C at high strain rates ([approximately] 10[sup [minus]1]s[sup [minus]1]). The present paper is an extension of the above study, demonstrating the effects of Zr additions to an Al alloy on superplastic strain rates. The deformation properties of a 2124 Al alloy containing 0.6wt%Zr have been characterized. As a result of the Zr addition, the alloy has a relatively fine grain size ([approximately] 1[mu]m). At relatively low strain rates (< 10[sup [minus]2]s[sup [minus]1]), the fine-grained 2124-0.6Zr alloy behaves like conventional coarse-grained alloys, i.e., it deforms by a dislocation climb mechanism at elevated temperatures (approximately 425-500 C). At high strain rates, however, the 2124-0.6Zr alloy exhibits superplasticity, similar to that observed in SiC whisker reinforced 2124 Al composites. The maximum tensile elongation is about 500%, recorded at 475 C, and at a strain rate of 3.3 [times] 10[sup [minus]1]s[sup [minus]1]. The high strain rate phenomenon is consistent with the general trend observed in aluminum-based alloys, namely, an increased strain rate for optimal superplastic flow with a decrease in grain size.

  7. Modeling temperature and strain rate history in effects in OFHU Cu

    NASA Astrophysics Data System (ADS)

    Tanner, Albert Buck

    Accurate material behavior prediction during large deformations is essential. For the U.S. Army, explosively formed projectiles (EFP), penetrators, and vehicle armor are applications which will benefit from a better understanding of and ability to predict material behavior when subjected to high and varying strain rates and temperatures. Linking macro-scale material behavior with the evolution of microstructure has proven effective in obtaining an appropriate mathematical structure for constitutive relationships. Incorporation of strain rate, temperature, and deformation path history effects are especially critical to accurately predict material responses for arbitrary nonisothermal, variable strain rate conditions. Material constitutive equations contain numerous parameters which must be determined experimentally, and often are not fully optimized. The goal of this research was to develop more physically descriptive kinematics and kinetics models for large strain deformation based on internal state variable (ISV) evolution laws which include strain rate and temperature history dependence. A unique and comprehensive set of experiments involving sequences of different strain rates, temperatures, and deformation paths, as well as, constant strain rate, isothermal and experiments characterizing restoration processes, were conducted on OFHC Cu. Microstructural examinations found that recrystallization occurs and has a significant influence on the flow stress. The performance of various models, including state-of-the-art models such as the BCJ (Sandia), MTS (Los Alamos), and McDowell models were correlated and compared to experimental data. A novel hybrid optimization strategy was used to obtain the optimum parameter set possible corresponding to each model form. To account for the observed flow stress softening, an internal state variable representing the "softened" recrystallized state was incorporated into the hardening evolution equations in the BCJ and Mc

  8. 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

  9. The effect of strain rate history on the ductility in superplastic AA-5083

    SciTech Connect

    Khaleel, M.A.; Smith, M.T.; Pitman, S.G.

    1997-12-15

    Rapid oscillations of load during deformation of superplastic materials have been reported by several researchers. In an investigation on AA7475, Ghosh and Raj developed a model to study the oscillations observed within the strain rate range from 10{sup {minus}3}s{sup {minus}1} to 5 {times} 10{sup {minus}3}s{sup {minus}1}. The oscillations in the stress-strain curve were related to changes in the grain size due to refinement by dynamic recrystallization and grain growth during deformation. Using the same alloy Hamilton et al. observed oscillations in stress-strain curves at strain rates of 5 {times} 10{sup {minus}3}s{sup {minus}1} and 10{sup {minus}2}s{sup {minus}1}. These oscillations were attributed to dynamic strain aging. Yang et al. observed serrations in the stress-strain curves of AA7475 tested at temperatures ranging from 20 to 525 C. The amplitude of the load fluctuation was related to the strain-rate sensitivity. The explanation they gave for this was that serrations are caused by continuous shifting of multiple necks from one region to another, and dynamic change in the grain structure. Li and Blackwell studied load oscillations in tensile deformation of Al-Li and Al-Mg alloys at temperatures > 500 C and strain rate < 10{sup {minus}2}s{sup {minus}1}. They also observed that the amplitude of the fluctuations was found to very according to the strain rate sensitivity of the material. They concluded that load serrations observed in their study are a closed-loop controlled screw-driven machine effect. They also observed that cross-head speed varied in a cyclic manner. The purpose of this study is to determine the effects of applying non-uniform strain rates on superplastic properties of AA5083 using a motor-driven system operating in an open-loop mode.

  10. 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.

  11. 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.

  12. 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

  13. The Effect of Temperature and Strain Rate on Porosity Loss in Granular Material

    NASA Astrophysics Data System (ADS)

    Choens, R. C.; Chester, F. M.

    2013-12-01

    Experimental rock deformation was used to quantify the relationship between temperature, stress, and strain rate for brittle consolidation of wet quartz sand at hydrostatic conditions. Petrographic analysis of natural quartz sandstone employing cathode luminescence has shown that grain-scale fracture and grain rearrangement, and associated sealing of fractures, can contribute significantly to consolidation during burial, and that fracturing is similar to that produced during pressure induced consolidation in experiments. The crushing pressure (P*) for granular material, which largely depends on grain size and porosity, is typically defined by room temperature laboratory experiments at strain rates of 10-4 to 10-5 sec-1. Failure envelopes determined for natural sandstones based on measurement of P* generally imply burial depths in excess of inferred burial history. Previous work has shown that elevated temperature decreases the failure strength necessary to cause intergranular fractures, and thus P* should be a strong function of temperature and time. We use soil mechanics principles to determine rate laws for brittle consolidation of sand to better estimate in situ failure conditions of porous geomaterials. Experiments were conducted on St. Peter's sand, a sub rounded quartz sand sieved to 250 to 350 μm grain size. Three different hydrostatic load paths were used for this study: constant plastic strain rate consolidation, plastic strain rate stepping consolidation, and secondary creep consolidation experiments. Constant rate experiments were performed at 10-5 to 10-7 sec-1, and at 20, 150, and 225 C. Creep experiments reached strain rates as low as 10-10 sec-1. Comparison of results from consolidation experiments at different temperatures and strain rates in volume strain versus log pressure space show the consolidation curves are parallel and the effect of increase in temperature and decrease in plastic strain rate is to shift the curves to lower pressures

  14. Strain rate and anisotropy effects on the tensile failure characteristics of human skin.

    PubMed

    Ottenio, Mélanie; Tran, Doris; Ní Annaidh, Aisling; Gilchrist, Michael D; Bruyère, Karine

    2015-01-01

    The anisotropic failure characteristics of human skin are relatively unknown at strain rates typical in impact biomechanics. This study reports the results of an experimental protocol to quantify the effect of dynamic strain rates and the effect of sample orientation with respect to the Langer lines. Uniaxial tensile tests were carried out at three strain rates (0.06s(-1), 53s(-1), and 167s(-1)) on 33 test samples excised from the back of a fresh cadaver. The mean ultimate tensile stress, mean elastic modulus and mean strain energy increased with increasing strain rates. While the stretch ratio at ultimate tensile stress was not affected by the strain rate, it was influenced by the orientation of the samples (parallel and perpendicular to the Langer lines. The orientation of the sample also had a strong influence on the ultimate tensile stress, with a mean value of 28.0 ± 5.7 MPa for parallel samples, and 15.6 ± 5.2 MPa for perpendicular samples, and on the elastic modulus, with corresponding mean values of 160.8 MPa ± 53.2 MPa and 70.6 MPa ± 59.5 MPa. The study also pointed out the difficulties in controlling the effective applied strain rate in dynamic characterization of soft tissue and the resulting abnormal stress-strain relationships. Finally, data collected in this study can be used to develop constitutive models where high loading rates are of primary interest. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. 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

  16. 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'.

  17. 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'.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Effect of high strain rates on peak stress in a Zr-based bulk metallic glass

    SciTech Connect

    Sunny, George; Yuan Fuping; Prakash, Vikas; Lewandowski, John

    2008-11-01

    The mechanical behavior of Zr{sub 41.25}Ti{sub 13.75}Cu{sub 12.5}Ni{sub 10}Be{sub 22.5} (LM-1) has been extensively characterized under quasistatic loading conditions; however, its mechanical behavior under dynamic loading conditions is currently not well understood. A Split-Hopkinson pressure bar (SHPB) and a single-stage gas gun are employed to characterize the mechanical behavior of LM-1 in the strain-rate regime of 10{sup 2}-10{sup 5}/s. The SHPB experiments are conducted with a tapered insert design to mitigate the effects of stress concentrations and preferential failure at the specimen-insert interface. The higher strain-rate plate-impact compression-and-shear experiments are conducted by impacting a thick tungsten carbide (WC) flyer plate with a sandwich sample comprising a thin bulk metallic glass specimen between two thicker WC target plates. Specimens employed in the SHPB experiments failed in the gage-section at a peak stress of approximately 1.8 GPa. Specimens in the high strain-rate plate-impact experiments exhibited a flow stress in shear of approximately 0.9 GPa, regardless of the shear strain-rate. The flow stress under the plate-impact conditions was converted to an equivalent flow stress under uniaxial compression by assuming a von Mises-like material behavior and accounting for the plane strain conditions. The results of these experiments, when compared to the previous work conducted at quasistatic loading rates, indicate that the peak stress of LM-1 is essentially strain rate independent over the strain-rate range up to 10{sup 5}/s.

  4. 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.

  5. Effect of strain rate and dislocation density on the twinning behavior in Tantalum

    DOE PAGES

    Florando, Jeffrey N.; El-Dasher, Bassem S.; Chen, Changqiang; ...

    2016-04-28

    The conditions which affect twinning in tantalum have been investigated across a range of strain rates and initial dislocation densities. Tantalum samples were subjected to a range of strain rates, from 10–4/s to 103/s under uniaxial stress conditions, and under laser-induced shock-loading conditions. In this study, twinning was observed at 77K at strain rates from 1/s to 103/s, and during laser-induced shock experiments. The effect of the initial dislocation density, which was imparted by deforming the material to different amounts of pre-strain, was also studied, and it was shown that twinning is suppressed after a given amount of pre-strain, evenmore » as the global stress continues to increase. These results indicate that the conditions for twinning cannot be represented solely by a critical global stress value, but are also dependent on the evolution of the dislocation density. Additionally, the analysis shows that if twinning is initiated, the nucleated twins may continue to grow as a function of strain, even as the dislocation density continues to increase.« less

  6. Effect of strain rate and dislocation density on the twinning behavior in tantalum

    SciTech Connect

    Florando, Jeffrey N. Swift, Damian C.; Barton, Nathan R.; McNaney, James M.; Kumar, Mukul; El-Dasher, Bassem S.; Chen, Changqiang; Ramesh, K. T.; Hemker, Kevin J.

    2016-04-15

    The conditions which affect twinning in tantalum have been investigated across a range of strain rates and initial dislocation densities. Tantalum samples were subjected to a range of strain rates, from 10{sup −4}/s to 10{sup 3}/s under uniaxial stress conditions, and under laser-induced shock-loading conditions. In this study, twinning was observed at 77 K at strain rates from 1/s to 10{sup 3}/s, and during laser-induced shock experiments. The effect of the initial dislocation density, which was imparted by deforming the material to different amounts of pre-strain, was also studied, and it was shown that twinning is suppressed after a given amount of pre-strain, even as the global stress continues to increase. These results indicate that the conditions for twinning cannot be represented solely by a critical global stress value, but are also dependent on the evolution of the dislocation density. In addition, the analysis shows that if twinning is initiated, the nucleated twins may continue to grow as a function of strain, even as the dislocation density continues to increase.

  7. 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.

  8. Effects of tissue preservation temperature on high strain-rate material properties of brain.

    PubMed

    Zhang, Jiangyue; Yoganandan, Narayan; Pintar, Frank A; Guan, Yabo; Shender, Barry; Paskoff, Glenn; Laud, Purushottam

    2011-02-03

    Postmortem preservation conditions may be one of factors contributing to wide material property variations in brain tissues in literature. The objective of present study was to determine the effects of preservation temperatures on high strain-rate material properties of brain tissues using the split Hopkinson pressure bar (SHPB). Porcine brains were harvested immediately after sacrifice, sliced into 2 mm thickness, preserved in ice cold (group A, 10 samples) and 37°C (group B, 9 samples) saline solution and warmed to 37°C just prior to the test. A SHPB with tube aluminum transmission bar and semi-conductor strain gauges were used to enhance transmitted wave signals. Data were gathered using a digital acquisition system and processed to obtain stress-strain curves. All tests were conducted within 4 h postmortem. The mean strain-rate was 2487±72 s(-1). A repeated measures model with specimen-level random effects was used to analyze log transformed stress-strain responses through the entire loading range. The mean stress-strain curves with ±95% confidence bands demonstrated typical power relationships with the power value of 2.4519 (standard error, 0.0436) for group A and 2.2657 (standard error, 0.0443) for group B, indicating that responses for the two groups are significantly different. Stresses and tangent moduli rose with increasing strain levels in both groups. These findings indicate that storage temperatures affected brain tissue material properties and preserving tissues at 37°C produced a stiffer response at high strain-rates. Therefore, it is necessary to incorporate material properties obtained from appropriately preserved tissues to accurately predict the responses of brain using stress analyses models, such as finite element simulations. Published by Elsevier Ltd.

  9. 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.

  10. 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

  11. A Study on the Effect of Strain Rate on the Dynamic Recrystallization Mechanism of Alloy 617B

    NASA Astrophysics Data System (ADS)

    Jiang, He; Dong, Jianxin; Zhang, Maicang; Yao, Zhihao

    2016-10-01

    The effect of strain rate on dynamic recrystallization (DRX) behavior and mechanism of alloy 617B was investigated by isothermal compression test in a temperature range of 1393 K to 1483 K (1120 °C to 1210 °C) with a wide strain rate scope of 0.01 to 20 s-1. The microstructure evolution was investigated comprehensively by optical microscopy, electron backscatter diffraction (EBSD), electron channeling contrast imaging (ECCI), and transmission electron microscopy (TEM) to provide detailed insight into the effect of strain rate on DRX mechanism. The study shows that DRX is accelerated at both low strain rate and high strain rate conditions with an apparent sluggish kinetics at the intermediate strain rate of 1 s-1. In the low strain rate condition ( i.e., <1 s-1), DRX is mainly controlled by the growth of DRX nuclei due to the sufficient time. When the strain rate is higher than 1 s-1, besides the commonly accepted reason of adiabatic heat generated by high strain rate, enhanced DRX nucleation mechanism is crucial for the promotion of DRX at high strain rate. High strain rate could lead to enhanced pile-up of dislocation and higher stored energy, which can facilitate the process of DRX. In addition, distortion or subdivision of twins and "grain fragment" are detected when the strain rate is higher than 1 s-1, which provide additional DRX nucleation mechanism. As a result, the combined effect leads to the higher DRX nucleation rate to promote DRX at high strain rate. The effect of strain rate on DRX is the completion result between sufficiency of time on the one hand and adiabatic heat and enhanced nucleation mechanism on the other.

  12. 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].

  13. 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.

  14. 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.

  15. 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.

  16. Strain-Rate Effects on Microstructural Deformation in Irradiated 316 SS

    SciTech Connect

    James I. Cole; Todd R. Allen; Naoaki Akasaka; Hanchung Tsai; Tsunemitsu Yoshitake; Ichiro Yamagata; Yasuo Nakamura

    2005-02-01

    A series of studies have been performed to investigate the post-irradiation deformation and failure behavior of 12% cold-worked 316 stainless steel following irradiation to variety of doses and temperatures in the outer rows of the experimental breeder reactor II (EBR-II). In the current phase of these studies, three sets of samples with different radiation induced microstructures have been characterized with transmission electron microscopy (TEM) following tensile testing to failure at a ‘fast’ strain-rate (1 x 10-3 s-1) and a ‘slow’ strain-rate (1 x 10-7 s-1). The samples were irradiated to doses between 9 and 41 dpa at temperatures between 383 and 443 degrees C. Tensile tests were conducted at a temperature of 430 degrees C and only regions outside of the necked region were examined. Over the parameters tested, strain-rate had a negligible effect on the deformation microstructure. In addition, there was no clear evidence of localized deformation behavior and the deformation appeared relatively homogeneous, characterized by unfaulting and incorporation of faulted dislocation loops into the general dislocation network structure. The influence of the defect microstructures and strain-rate on deformation behavior is discussed.

  17. 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

  18. Effects of gamma radiation sterilization and strain rate on compressive behavior of equine cortical bone.

    PubMed

    Tüfekci, Kenan; Kayacan, Ramazan; Kurbanoğlu, Cahit

    2014-06-01

    Gamma radiation has been widely used for sterilization of bone allograft. However, sterilization by gamma radiation damages the material properties of bone which is a major clinical concern since bone allograft is used in load bearing applications. While the degree of this damage is well investigated for quasi-static and cyclic loading conditions, there does not appear any information on mechanical behavior of gamma-irradiated cortical bone at high speed loading conditions. In this study, the effects of gamma irradiation on high strain rate compressive behavior of equine cortical bone were investigated using a Split Hopkinson Pressure Bar (SHPB). Quasi-static compression testing was also performed. Equine cortical bone tissue from 8year old retired racehorses was divided into two groups: non-irradiated and gamma-irradiated at 30kGy. Quasi-static and high strain rate compression tests were performed at average strain rates of 0.0045/s and 725/s, respectively. Agreeing with previous results on the embrittlement of cortical bone when gamma-irradiated, the quasi-static results showed that gamma-irradiation significantly decreased ultimate strength (9%), ultimate strain (27%) and toughness (41%), while not having significant effect on modulus of elasticity, yield strain and resilience. More importantly, contrary to what is typically observed in quasi-static loading, the gamma-irradiated bone under high speed loading showed significantly higher modulus of elasticity (45%), ultimate strength (24%) and toughness (26%) than those of non-irradiated bone, although the failure was at a similar strain. Under high speed loading, the mechanical properties of bone allografts were not degraded by irradiation, in contrast to the degradation measured in this and prior studies under quasi-static loading. This result calls into question the assumption that bone allograft is always degraded by gamma irradiation, regardless of loading conditions. However, it needs further investigation

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

    PubMed

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

    2017-01-15

    This 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. Samples were tested in the rehydrated (35wt% water) and ambient dry (10wt% 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. 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. 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. The horn of the bighorn sheep is an anisotropic composite composed of keratin that is highly sensitive to moisture content. Keratin is also found in many other animals in the form of hooves, claws, beaks, and feathers. Only one previous study contains high rate experimental data, which was performed in the dry condition and only in compression. Considering the bighorn sheep horns' protective role in high speed impacts along with the moisture and strain rate sensitivity, more high strain rate data is needed to fully characterize and model the material. This study provides high strain

  20. 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.

  1. Time dependent deformation of a basalt at low differential stress. [strain rate and moisture content effects

    NASA Technical Reports Server (NTRS)

    Brodsky, N.; Spetzler, H.

    1979-01-01

    A detailed study of linear elastic deformation in Ralston basalt during triaxial loading has been made as a function of strain rate (8 x 10 to the -8th per sec to 5 x 10 to the -5th per sec) and moisture content under constant confining pressure (500 bars) and temperature (20 C). Young's modulus was found to be constant and independent of moisture content and strain rate; however, Poisson's ratio decreased 5.7 plus or minus 1.6% and 6.7 plus or minus 1.6% per order of magnitude increase in strain rate for two suites of dry samples and 1.4 plus or minus 1.2% per equivalent change in strain rate for one suite of wet rocks. Lateral expansion in dry rocks is therefore a more sensitive function of strain rate than it is in wet rocks. It is suggested that this strain-rate dependence is related to microcracking.

  2. 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.

  3. Effect of microstructure on anomalous strain-rate-dependent behaviour of bacterial cellulose hydrogel.

    PubMed

    Gao, Xing; Shi, Zhijun; Lau, Andrew; Liu, Changqin; Yang, Guang; Silberschmidt, Vadim V

    2016-05-01

    This study is focused on anomalous strain-rate-dependent behaviour of bacterial cellulose (BC) hydrogel that can be strain-rate insensitive, hardening, softening, or strain-rate insensitive in various ranges of strain rate. BC hydrogel consists of randomly distributed nanofibres and a large content of free water; thanks to its ideal biocompatibility, it is suitable for biomedical applications. Motivated by its potential applications in complex loading conditions of body environment, its time-dependent behaviour was studied by means of in-aqua uniaxial tension tests at constant temperature of 37 °C at various strain rates ranging from 0.000 1s(-1) to 0.3s(-1). Experimental results reflect anomalous strain-rate-dependent behaviour that was not documented before. Micro-morphological observations allowed identification of deformation mechanisms at low and high strain rates in relation to microstructural changes. Unlike strain-rate softening behaviours in other materials, reorientation of nanofibres and kinematics of free-water flow dominate the softening behaviour of BC hydrogel at high strain rates. Copyright © 2016 Elsevier B.V. All rights reserved.

  4. 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.

  5. Effects of strain rate and anisotropy on the tensile deformation properties of extruded AlZnMg alloys

    SciTech Connect

    Fjeldly, A.; Roven, H.J.

    2000-03-01

    Two extruded AlZnMg alloys have been investigated in uniaxial tension, emphasizing the mechanical anisotropy and strain-rate effects. A strong mechanical anisotropy was found in the extruded profiles which had recrystallized and nonrecrystallized microstructures. The recrystallized alloy had a lower strength level and less variation in ductility and formability parameters than the noncrystallized alloy. Mg in solid solution causes dynamic strain aging (DSA) in both alloys. With increasing strain rate, the DSA became less effective and the strain localization caused by DSA vanished. Thus, the room-temperature formability, in the solution heat-treated and quenched condition, may be improved significantly by a sufficient increase of the strain rate. Additional tests on an as-cast sheet-ingot AlMg alloy were performed to isolate the effect of Mg from Zn in solid solution. These tests confirmed the effect of strain rate on the tensile behavior.

  6. Effect of Dynamic Change in Strain Rate on Mechanical and Stress Corrosion Cracking Behavior of a Mild Steel

    NASA Astrophysics Data System (ADS)

    Krishnan, Govinda; Varshney, A.; Parameswaran, Venkitanarayanan; Mondal, K.

    2017-05-01

    The current work analyzes the effect of the dynamic change in strain rate during tensile loading of a mild steel on its mechanical and stress corrosion behavior in 3.5 wt.% NaCl solution. The sample experiences high strain rate (10-2 s-1) up to 10, 15 and 20% of total deformation and then very low strain rate of 10-6 s-1 till fracture without any unloading in between. The behavioral characteristics of the steel under these circumstances are found to be different from that exhibited during complete loading till fracture both at high and slow strain rates separately. Total strain increases with the increase in the strain at which change in strain rate happens, and this is attributed to the generation of large number of dislocations at higher strain rate and subsequently release of dislocation at low strain rate during change over due to more time available for dynamic recovery. This observation is common for both in air and corrosive environment. One unique observation in this study is the higher total strain and lower strength observed during dynamic change in strain rate in the corrosive environment compared to that in air, which is attributed to the hydrogen-induced plasticity mechanism.

  7. 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.

  8. 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.

  9. The effect of strain rates on tensile deformation of ultrafine-grained copper

    NASA Astrophysics Data System (ADS)

    Li, M.; Jiang, Q. W.

    2017-07-01

    Tensile deformation behavior of ultrafine-grained (UFG) copper processed by accumulative roll-bonding (ARB) was studied under different strain rates at room temperature. It was found that the UFG copper under the strain rate of 10-2 s-1 led to a higher strength (higher flow stress level), flow stability (higher stress hardening rate) and fracture elongation. In the fracture surface of the sample appeared a large number of cleavage steps under the strain rate of 10-3 s-1, indicating a typical brittle fracture mode. When the strain rate is 10-2 or 10-1 s-1, a great amount of dimples with few cleavage steps were observed, showing a transition from brittle to plastic deformation with increasing strain rate.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. Effect of Strain Rate on the Deformation of Red Blood Cells Entering a Constriction

    NASA Astrophysics Data System (ADS)

    Mancuso, Jordan; Ristenpart, William

    2015-11-01

    Although much work has investigated the stretching behavior of RBCs in shear flows, relatively little work has examined the deformation that occurs in the physiologically important extensional flow at the entrance to a constriction. In particular, there is currently no analytical model to predict the extent of deformation as a function of the strain rate in the constriction entrance. Here we experimentally elucidate the relationship between strain rate and the dynamic stretching behavior of RBCs as they enter a microfluidic constriction. We systematically varied the flow rate and the microchannel geometry to vary the strain rate, and we measured the resulting RBC deformations with high speed video. We demonstrate that the Kelvin Voigt model captures the stretching dynamics, and that the RBC membrane elastic shear modulus increases approximately linearly with increasing strain rate.

  17. 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.

  18. 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

    2017-06-01

    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.

  19. 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.

  20. The effect of strain rate on the evolution of microstructure in aluminium alloys.

    PubMed

    Leszczyńska-Madej, B; Richert, M

    2010-03-01

    Intensive deformations influence strongly microstructure. The very well-known phenomenon is the diminishing dimension of grain size by the severe plastic deformation (SPD) methods. The nanometric features of microstructure were discovered after the SPD deformation of various materials, such as aluminium alloys, iron and others. The observed changes depended on the kind of the deformed material, amount of deformation, strain rate, existence of different phases and stacking fault energy. The influence of the strain and strain rate on the microstructure is commonly investigated nowadays. It was found that the high strain rates activate deformation in shear bands, microbands and adiabatic shear bands. It was observed that bands were places of the nucleation of nanograins in the material deformed by SPD methods. In the work, the refinement of microstructure of the aluminium alloys influenced by the high strain rate was investigated. The samples were compressed by a specially designed hammer to the deformation of phi= 0/0.62 with the strain rate in the range of [Formula in text]. The highest reduction of microbands width with the increase of the strain was found in the AlCu4Zr alloy. The influence of the strain rate on the microstructure refinement indicated that the increase of the strain rate caused the reduction of the microbands width in the all investigated materials (Al99.5, AlCu4Zr, AlMg5, AlZn6Mg2.5CuZr). A characteristic feature of the microstructure of the compressed material was large density of the shear bands and microbands. It was found that the microbands show a large misorientation to the surrounds and, except Al99.5, the large density of dislocation.

  1. Size and strain rate effects in tensile strength of penta-twinned Ag nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, Xuan; Li, Xiaoyan; Gao, Huajian

    2017-08-01

    Penta-twinned Ag nanowires (pt-AgNWs) have recently attracted much attention due to their interesting mechanical and physical properties. Here we perform large-scale atomistic simulations to investigate the influence of sample size and strain rate on the tensile strength of pt-AgNWs. The simulation results show an apparent size effect in that the nanowire strength (defined as the critical stress for dislocation nucleation) increases with decreasing wire diameter. To account for such size effect, a theoretical model involving the interaction between an emerging dislocation and the twin boundary has been developed for the surface nucleation of dislocations. It is shown that the model predictions are in quantitative agreement with the results from atomistic simulations and previous experimental studies in the literatures. The simulations also reveal that nanowire strength is strain-rate dependent, which predicts an activation volume for dislocation nucleation in the range of 1-10b3, where b is the magnitude of the Burgers vector for a full dislocation.

  2. Evidence concerning crack-tip constraint and strain-rate effects in fracture-toughness testing

    SciTech Connect

    Merkle, J.G.

    1986-01-01

    The procedures for measuring the plane strain fracture toughness, K/sub Ic/, of metals were originally developed for relatively high yield strength materials, the toughnesses of which were not affected by stain rate. The application of these procedures to lower yield strength and higher toughness structural and pressure vessel steels have since revealed a perplexing combination of problems involving the effects of geometry, stable crack growth and strain rate on the measured values of toughness. Only the geometric problems were encountered in the development of the procedures for measuring K/sub Ic/. For fracture in the linear elastic range of the load-displacement curve, these problems were overcome by specifying specimen dimensions sufficiently large with respect of the plastic zone size at fracture. However, in the case of structural and pressure vessel steels, it is not always possible to test specimens large enough for fracture to occur prior to general yielding. Therefore, in these cases, the effects of large-scale yielding prior to fracture cannot be avoided, but since they presently have no analytical explanation they are being treated empirically.

  3. Size and strain rate effects in tensile strength of penta-twinned Ag nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, Xuan; Li, Xiaoyan; Gao, Huajian

    2017-06-01

    Penta-twinned Ag nanowires (pt-AgNWs) have recently attracted much attention due to their interesting mechanical and physical properties. Here we perform large-scale atomistic simulations to investigate the influence of sample size and strain rate on the tensile strength of pt-AgNWs. The simulation results show an apparent size effect in that the nanowire strength (defined as the critical stress for dislocation nucleation) increases with decreasing wire diameter. To account for such size effect, a theoretical model involving the interaction between an emerging dislocation and the twin boundary has been developed for the surface nucleation of dislocations. It is shown that the model predictions are in quantitative agreement with the results from atomistic simulations and previous experimental studies in the literatures. The simulations also reveal that nanowire strength is strain-rate dependent, which predicts an activation volume for dislocation nucleation in the range of 1-10b3 , where b is the magnitude of the Burgers vector for a full dislocation.

  4. 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

  5. Effects of Adiabatic Heating on the High Strain Rate Deformation of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Sorini, Chris; Chattopadhyay, Aditi; Goldberg, Robert K.

    2017-01-01

    Polymer matrix composites (PMCs) are increasingly being used in aerospace structures that are expected to experience complex dynamic loading conditions throughout their lifetime. As such, a detailed understanding of the high strain rate behavior of the constituents, particularly the strain rate, temperature, and pressure dependent polymer matrix, is paramount. In this paper, preliminary efforts in modeling experimentally observed temperature rises due to plastic deformation in PMCs subjected to dynamic loading are presented. To this end, an existing isothermal viscoplastic polymer constitutive formulation is extended to model adiabatic conditions by incorporating temperature dependent elastic properties and modifying the components of the inelastic strain rate tensor to explicitly depend on temperature. It is demonstrated that the modified polymer constitutive model is capable of capturing strain rate and temperature dependent yield as well as thermal softening associated with the conversion of plastic work to heat at high rates of strain. The modified constitutive model is then embedded within a strength of materials based micromechanics framework to investigate the manifestation of matrix thermal softening, due to the conversion of plastic work to heat, on the high strain rate response of a T700Epon 862 (T700E862) unidirectional composite. Adiabatic model predictions for high strain rate composite longitudinal tensile, transverse tensile, and in-plane shear loading are presented. Results show a substantial deviation from isothermal conditions; significant thermal softening is observed for matrix dominated deformation modes (transverse tension and in-plane shear), highlighting the importance of accounting for the conversion of plastic work to heat in the polymer matrix in the high strain rate analysis of PMC structures.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. Effect of Temperature and Strain Rate on Microstructure of a Deformed, Superplastic Al-10%Mg-0.1%Zr Alloy.

    DTIC Science & Technology

    1985-06-01

    16] and Herring [Ref. 171 proposed that the creep process was controlled by 17 ! V stress-directed diffusion . This ’ diffusional creep’ involves the...AD-A159 015 EFFECT OF TEMPERATURE AND STRAIN RATE ON MICROSTRUCTURE 1/1 OF A DEFORMED SUPERPLRSTIC RL-iOMG-OiZR RLLOY(U) NRVAL POSTGRADUATE SCHOOL...RESOLUTION TEST CHART NATIONAL BUREAU OF STANOARDS-1963 -A 11 . p NAVAL POSTGRADUATE SCHOOL Monterey, California THESIS EFFECT OF TEMPERATURE AND STRAIN RATE

  11. 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.

  12. Effect of equivalence ratio on premixed flame response to unsteady strain-rate and curvature

    SciTech Connect

    Najm, H.N.; Wyckoff, P.S.; Knio, O.M.

    1998-03-01

    The interaction of a premixed stoichiometric methane-air flame with a two-dimensional counter-rotating vortex pair is studied under stoichiometric and rich conditions using a detailed C{sub 1}C{sub 2} chemical mechanism. The focus is on the effect of equivalence ratio on flame response to unsteady strain-rate and curvature. Flame structure and transient response are studied, both at curved cusps and on the vortex-pair centerline. The rich flame is found to exhibit faster response to flow disturbances. Results suggest this is due to the increased sensitivity of the flame to H concentration at rich conditions. Significant differences are observed in the unsteady behavior of some C{sub 2} species, where substantial transient accumulation is observed at stoichiometric conditions, but not at rich conditions. Transient response of flame observables, such as CH, OH, and HCO, is studied and compared to experimental data.

  13. Thixoforming of Steel: New Tools Conception to Analyse Thermal Exchanges and Strain Rate Effects

    SciTech Connect

    Cezard, P.; Bigot, R.; Becker, E.; Mathieu, S.; Pierret, J. C.; Rassili, A.

    2007-04-07

    Through different papers, authors shown that the influence of thermal exchanges was a first order parameter on the semi-solid steel behaviour, and certainly for every semi-solid metallic materials. These thermal exchanges hide other parameters effect like, for example, the strain rate influence. This paper tries to determine the influence of these two parameters by using a new extrusion device on a hydraulic press. This new tools conception annihilated the influence of the decrease of the punch speed before stopping and permitted to have a constant speed during the experiment. This work also deals with the homogeneous flow during thixoforming of steel and shows the importance to couple initial temperature of the slug with punch speed. This paper presents different conditions which permitted to have a homogeneous flow by keeping a low load.

  14. Effect of the strain rate on the properties of electrical copper

    NASA Astrophysics Data System (ADS)

    Loginov, Yu. N.; Demakov, S. L.; Illarionov, A. G.; Popov, A. A.

    2011-03-01

    The effect of the strain rate on the texture and strength characteristics of electrical copper is analyzed using an industrial experiment on low- and high-speed wire drawing. The mechanical properties of the product are determined. The strength of the wire drawn at a high speed is found to be about 20 MPa higher than that of the wire drawn at a low speed. Metallographic analysis shows no differences in the wire structures, and texture analysis reveals differences in the behavior of dominant texture components. The directions of the dominant texture components are found to rotate near the periphery of the workpiece (i.e., at the workpiece surface). The solution of the drawing problem by the finite element method demonstrates an analogous rotation of the principal elongation directions.

  15. 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.

  16. 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.

  17. 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

  18. Effect of growth rate and selection pressure on rates of transfer of an antibiotic resistance plasmid between E. coli strains.

    PubMed

    Schuurmans, Jasper M; van Hijum, Sacha A F T; Piet, Jurgen R; Händel, Nadine; Smelt, Jan; Brul, Stanley; ter Kuile, Benno H

    2014-03-01

    Antibiotic resistance increases costs for health care and causes therapy failure. An important mechanism for spreading resistance is transfer of plasmids containing resistance genes and subsequent selection. Yet the factors that influence the rate of transfer are poorly known. Rates of plasmid transfer were measured in co-cultures in chemostats of a donor and a acceptor strain under various selective pressures. To document whether specific mutations in either plasmid or acceptor genome are associated with the plasmid transfer, whole genome sequencing was performed. The DM0133 TetR tetracycline resistance plasmid was transferred between Escherichia coli K-12 strains during co-culture at frequencies that seemed higher at increased growth rate. Modeling of the take-over of the culture by the transformed strain suggests that in reality more transfer events occurred at low growth rates. At moderate selection pressure due to an antibiotic concentration that still allowed growth, a maximum transfer frequency was determined of once per 10(11) cell divisions. In the absence of tetracycline or in the presence of high concentrations the frequency of transfer was sometimes zero, but otherwise reduced by at least a factor of 5. Whole genome sequencing showed that the plasmid was transferred without mutations, but two functional mutations in the genome of the recipient strain accompanied this transfer. Exposure to concentrations of antibiotics that fall within the mutant selection window stimulated transfer of the resistance plasmid most. Copyright © 2014 Elsevier Inc. All rights reserved.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. Analytical and experimental studies on the strain rate effects in penetration of 10wt % ballistic gelatin

    NASA Astrophysics Data System (ADS)

    Liu, L.; Jia, Z.; Ma, X. L.; Fan, Y. R.

    2013-07-01

    This work concentrates on modeling the super-elastic behavior of 10wt% ballistic gelatin at 4°C and the mechanical responses at quasi-static and high-speed penetrations. Uniaxial compression and simple shearing experiments were carried out to determine the moduli in Mooney-Rivlin model describing the elastic behavior of gelatin at low strain rates. The failure mode is determined to be elastic fracture as the tensile stretch ratio exceeds a critical value. For high compression strain rates, the available results from the split Hopkinson pressure bar (SHPB) experiments for 10wt% gelatin were carefully examined and assessed. Linear relationship between the moduli and the strain rate is established. Based on these material parameters, an analytic solution of stress for the quasi-static and quasi-dynamic expansion of spherical cavity in gelatin is derived. As a consequence, the work needed to open unit volume of cavity, Ps, which is the key parameter in studying penetration problems, is linearly increasing with the characteristic strain rate. The application of Ps to our quasi-static and high-speed penetration experiments is discussed and assessed.

  6. 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

  7. Temperature and strain-rate effects on deformation mechanisms in irradiated stainless steel

    SciTech Connect

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

    1994-11-01

    Analysis of the deformation microstructures in ion-irradiated stainless steel shows twinning to be the predominant deformation mode at room temperature. Dislocation channelling also occurs under slow strain rate conditions. Stresses required for twinning were calculated by the model of Venables and are compatible with observed yield stresses in neutron-irradiated material if loops are the principal twin source. Computation of the expected radiation hardening from the defect structure, based on a simple model, is consistent with yield strengths measured on neutron-irradiated steels. Lower yield stresses and greater thermal energy at 288 C lessen the probability of twinning and dislocation channeling becomes the primary deformation mode at the higher temperature. However, preliminary early results show that some twinning does occur in the irradiated stainless steel even at the higher temperature when higher strain rates are used.

  8. 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.

  9. 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.

  10. 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).

  11. Effect of pulse duration and strain rate on incipient spall fracture in copper

    SciTech Connect

    Johnson, J.N.; Gray, G.T. III; Bourne, N.K.

    1999-11-01

    Data are presented on real time (VISAR) measurements of the spall fracture of copper for various pulse durations and tensile strain rates at the spall plane. The impactors consist of Teflon, {ital Y}-cut quartz, and a tungsten heavy alloy. VISAR data are compared with finite-difference calculations employing a rate-dependent void-growth model. The data and comparisons show little dependence of the onset of void growth on either pulse duration or tensile strain rate. Also, it is shown that hydrodynamics (wave propagation properties) involving the transmission of the spall signal from the spall plane to the free surface (plane of the VISAR measurement) can mask slight differences in the void-growth or fracture response. In addition, new results are presented for the elastic description of planar wave propagation in {ital Y}-cut quartz; expressions are given for the six independent stress components to second order in infinitesimal Lagrangian strains. A discussion with regard to additional use of {ital Y}-cut quartz in impact experiments is presented. {copyright} {ital 1999 American Institute of Physics.}

  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 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.

  14. 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.

  15. The effect of shearing strain-rate on the ultimate shearing resistance of clay

    NASA Technical Reports Server (NTRS)

    Cheng, R. Y. K.

    1975-01-01

    An approach for investigating the shearing resistance of cohesive soils subjected to a high rate of shearing strain is described. A fast step-loading torque apparatus was used to induce a state of pure shear in a hollow cylindrical soil specimen. The relationship between shearing resistance and rate of shear deformation was established for various soil densities expressed in terms of initial void ratio or water content. For rate of shearing deformation studies, the shearing resistance increases initially with shearing velocity, but subsequently reaches a terminal value as the shearing velocity increases. The terminal shearing resistance is also found to increase as the density of the soil increases. The results of this investigation are useful in the rheological study of clay. It is particularly important for mobility problems of soil runways, since the soil resistance is found to be sensitive to the rate of shearing.

  16. Effect of transcatheter pulmonary valve implantation on short-term right ventricular function as determined by two-dimensional speckle tracking strain and strain rate imaging.

    PubMed

    Moiduddin, Nasser; Asoh, Kentaro; Slorach, Cameron; Benson, Leland N; Friedberg, Mark K

    2009-09-15

    Transcatheter pulmonary valve implantation (PVI) is an emerging therapy for right ventricular (RV) outflow dysfunction in congenital heart disease. We investigated, for the first time in children after surgery for congenital heart disease, the short-term effects of PVI on RV and left ventricular (LV) function using 2-dimensional speckle tracking echocardiography and tissue Doppler imaging. We hypothesized that the short-term RV and LV function would improve. Two-dimensional speckle tracking echocardiograms and pulsed tissue Doppler images were obtained before and 1 to 2 days after PVI (18-mm Melody valve). The catheter right heart hemodynamics were recorded. The strain and strain rate of the basal lateral left ventricle, lateral right ventricle, and interventricular septum were measured by 2-dimensional speckle tracking echo, and the pre- and postprocedure values were compared. Of the 16 eligible patients (age 16 +/- 2 years), the scans of 10 had correct image format and adequate quality. PVI was performed for volume (n = 4) or combined pressure-volume (n = 6) loading. After PVI, the RV to pulmonary artery pressure gradient (33 +/- 22 to 12 +/- 4 mm Hg, p = 0.02), pulmonary regurgitation, and RV end-diastolic volume (3.2 +/- 0.8 to 2.8 +/- 0.6 cm, p = 0.02) decreased, and the septal systolic velocities (3.5 +/- 1.1 to 4.7 +/- 1.1 cm/s, p = 0.04), strain (-7.6 +/- 9.3% to -15.6% +/- 6.7%, p = 0.01) and strain rate (-0.3 +/- 1.1 to -1.1 +/- 0.5 1/s, p = 0.04) and RV free wall strain increased (-17.4 +/- 8.6% to -23.4% +/- 6.2%, p = 0.03). The LV tissue velocities, strain, and strain rate were unchanged. In conclusion, PVI leads to RV unloading and acutely improves RV and septal function.

  17. Effect of the strain rate on the mechanical properties of a sheet TRIP steel with a high martensite content

    NASA Astrophysics Data System (ADS)

    Eliseev, E. A.; Terent'ev, V. F.; Voznesenskaya, N. M.; Slizov, A. K.; Sirotinkin, V. P.; Baikin, A. S.; Seval'nev, G. S.

    2017-04-01

    The laws of changing the mechanical properties of sheet austenitic-martensitic VNS9-Sh (23Kh15N5AM3-Sh) TRIP steel are studied when the static strain rate changes in the range 0.1-20 mm/min (8.3 × 10-5-17 × 10-3 s-1). The 0.35-mm strip under study is characterized by a high martensite content (≈100%) in the surface layer at an average content of 80-85%. The transformation induced plasticity effect is maximal at a strain rate of 0.1 mm/min (8.3 × 10-5 s-1).

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. EFFECTS OF TEMPERATURE, STRAIN RATE, AND SWELLING ON THE STRESS-STRAIN PROPERTIES OF ETHYLENE-PROPYLENE GUM VULCANIZATES OF VARYING CROSSLINK DENSITY

    DTIC Science & Technology

    stress-strain curves were always greater than values obtained from the Mooney - Rivlin constants. Thermo elastic measurements showed that EPR undergoes a...two temperatures and two strain rates. A swell-deswell technique was employed to obtain equilibrium results at low volume fraction of rubber. The Mooney ... Rivlin constants were found to depend on temperature, strain rate, and crosslink density. The network structural parameters obtained from swollen

  8. 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

  9. The effect of water on strain localization in calcite fault gouge sheared at seismic slip rates

    NASA Astrophysics Data System (ADS)

    Rempe, Marieke; Smith, Steven; Mitchell, Thomas; Hirose, Takehiro; Di Toro, Giulio

    2017-04-01

    Strain localization during coseismic slip in fault gouges is a critical mechanical process that has implications for understanding frictional heating, the earthquake energy budget and the evolution of fault rock microstructure. To assess the nature of strain localization during shearing of calcite fault gouges, high-velocity (vmax = 1m /s) rotary-shear experiments at normal stresses of 3-20 MPa were conducted under room-dry and wet conditions on synthetic calcite gouges containing dolomite gouge strain markers. When sheared at 1 m/s, the room-dry gouges showed a prolonged strengthening phase prior to dynamic weakening, whereas the wet gouges weakened nearly instantaneously. Microstructural analysis revealed that a thin (<600 μm) high-strain layer and through-going principal slip surface (PSS) developed after several centimeters of slip in both dry and wet gouges, and that strain localization at 1 m/s occurred progressively and rapidly. The strain accommodated in the bulk gouge layer did not change significantly with increasing displacement indicating that, once formed, the high-strain layer and PSS accommodated most of the displacement. Thus, a substantial strain gradient is present in the gouge layer. In water-dampened gouges, localization likely occurs during and after dynamic weakening. Our results suggest that natural fault zones in limestone are more prone to rapid dynamic weakening if water is present in the granular slipping zones.

  10. 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).

  11. Effect of Strain Rate on Hot Ductility Behavior of a High Nitrogen Cr-Mn Austenitic Steel

    NASA Astrophysics Data System (ADS)

    Wang, Zhenhua; Meng, Qing; Qu, Minggui; Zhou, Zean; Wang, Bo; Fu, Wantang

    2016-03-01

    18Mn18Cr0.6N steel specimens were tensile tested between 1173 K and 1473 K (900 °C and 1200 °C) at 9 strain rates ranging from 0.001 to 10 s-1. The tensile strained microstructures were analyzed through electron backscatter diffraction analysis. The strain rate was found to affect hot ductility by influencing the strain distribution, the extent of dynamic recrystallization and the resulting grain size, and dynamic recovery. The crack nucleation sites were primarily located at grain boundaries and were not influenced by the strain rate. At 1473 K (1200 °C), a higher strain rate was beneficial for grain refinement and preventing hot cracking; however, dynamic recovery appreciably occurred at 0.001 s-1 and induced transgranular crack propagation. At 1373 K (1100 °C), a high extent of dynamic recrystallization and fine new grains at medium strain rates led to good hot ductility. The strain gradient from the interior of the grain to the grain boundary increased with decreasing strain rate at 1173 K and 1273 K (900 °C and 1000 °C), which promoted hot cracking. Grain boundary sliding accompanied grain rotation and did not contribute to hot cracking.

  12. 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.

  13. Major effect of inherited rheology weakening in the crust and mantle on continental intraplate strain and seismicity rates

    NASA Astrophysics Data System (ADS)

    Gueydan, Frédéric; Mazzotti, Stephane

    2017-04-01

    Stable Continental Regions (SCR, i.e., intraplate) are commonly viewed as non-deforming and very high resistance lithosphere domains, except in localized regions of higher strain and seismicity rates that often related to fossilized tectonic zones acting as weaker domains (e.g., Rhine Graben, New Madrid). Two main categories of models have been proposed to explain strain concentration in SCR: Local stress concentration (fault intersection, erosion pulse, …) and local lithosphere weakness (high geotherm, mantle anisotropy, …). In order to test the respective role of these various parameters of the stress - rheology - strain relationship, we propose a simple 1D model to quantify first-order continental strain rate variations using laboratory and field-based rheology laws for the crust and mantle. In particular, we include new strain-weakening rheologies in order to simulate tectonic heritage. Within the framework of near-failure equilibrium between tectonic forces and strain rates, we show that inherited rheology weakening plays a fundamental role in allowing for and explaining strain and seismicity concentration in intraplate weak zones. A comparison with empirical strain rate estimations in SCR and intraplate weak zones shows that inherited weakening rheologies can increase local strain rates by as much as three orders of magnitude, about one to two orders higher than that permitted by other processes such as stress concentration, thermal anomaly, etc.

  14. High Strain Rate Behavior of Nanoporous Tantalum

    NASA Astrophysics Data System (ADS)

    Ruestes, Carlos J.; Bringa, Eduardo M.; Stukowski, Alexander; Rodriguez Nieva, Joaquin F.; Bertolino, Graciela; Tang, Yizhe; Meyers, Marc A.

    2012-02-01

    Nano-scale failure under extreme conditions is not well understood. In addition to porosity arising from mechanical failure at high strain rates, porous structures also develop due to radiation damage. Therefore, understanding the role of porosity on mechanical behavior is important for the assessment and development of materials like metallic foams, and materials for new fission and fusion reactors, with improved mechanical properties. We carry out molecular dynamics (MD) simulations of a Tantalum (a model body-centered cubic metal) crystal with a collection of nanovoids under compression. The effects of high strain rate, ranging from 10^7s-1 to 10^10s-1, on the stress strain curve and on dislocation activity are examined. We find massive total dislocation densities, and estimate a much lower density of mobile dislocations, due to the formation of junctions. Despite the large stress and strain rate, we do not observe twin formation, since nanopores are effective dislocation production sources. A significant fraction of dislocations survive unloading, unlike what happens in fcc metals, and future experiments might be able to study similar recovered samples and find clues to their plastic behavior during loading.

  15. 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

  16. 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.

  17. 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('https://www.osti.gov/scitech/biblio/21516755','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21516755"><span>The <span class="hlt">Effect</span> of transient change in <span class="hlt">strain</span> <span class="hlt">rate</span> on plastic flow behaviour of Al-Mg-Si alloy at elevated temperatures</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Petrov, P.; Voronkov, V.; Potapenko, K.; Ivanov, V.</p> <p>2011-05-04</p> <p>In extrusion forging processes, the abrupt changes in <span class="hlt">strain</span> <span class="hlt">rate</span> follows the plastic deformation of a material within the deforming zone. To simulate accurately this <span class="hlt">effect</span>, the specific experimental investigation of the plastic flow during the transient change in <span class="hlt">strain</span> <span class="hlt">rate</span> should be performed. The present paper deals with the investigation of this <span class="hlt">effect</span> on the flow stress of an Al-Mg-Si alloy during its deformation at 350 deg. C. The investigation consists of two steps. Both steps are connected to the monotonic uniaxial compression loading of a cylindrical specimen. During the first step the flow behaviour of the alloy is investigated at the constant <span class="hlt">strain</span> <span class="hlt">rate</span> wihin the range of 0.1-50 s{sup -1} at the temperature range of 350-430 deg. C. During the second step the <span class="hlt">strain</span> <span class="hlt">rate</span> is abruptly increased or decreased from its current value at a fixed engineering <span class="hlt">strain</span> of 17-21%. From the beginning of the test up to the <span class="hlt">strain</span> of 17-21% the value of the <span class="hlt">strain</span> <span class="hlt">rate</span> is constant and equal to either 1 s{sup -1} or 10 s{sup -1}. At the <span class="hlt">strain</span> of 17-21% the value of a <span class="hlt">strain</span> <span class="hlt">rate</span> is either increased to 10 s{sup -1} or decreased to 1 s{sup -1}.The results of the experimental investigations were used to determine the isothermal flow stress-<span class="hlt">strain</span> curves of the Al-Mg-Si alloy as well as the heat <span class="hlt">effect</span> of plastic deformation of the alloy. On basis of these curves, the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity index m as a function of true <span class="hlt">strain</span> and temperature was determined. This parameter allows to optimize a technological process of hot forging of the aluminium alloy as well as it is very important data for the construction of a phenomenological flow stress model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AIPC.1353..374P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AIPC.1353..374P"><span>The <span class="hlt">Effect</span> of transient change in <span class="hlt">strain</span> <span class="hlt">rate</span> on plastic flow behaviour of Al-Mg-Si alloy at elevated temperatures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petrov, P.; Voronkov, V.; Potapenko, K.; Ivanov, V.</p> <p>2011-05-01</p> <p>In extrusion forging processes, the abrupt changes in <span class="hlt">strain</span> <span class="hlt">rate</span> follows the plastic deformation of a material within the deforming zone. To simulate accurately this <span class="hlt">effect</span>, the specific experimental investigation of the plastic flow during the transient change in <span class="hlt">strain</span> <span class="hlt">rate</span> should be performed. The present paper deals with the investigation of this <span class="hlt">effect</span> on the flow stress of an Al-Mg-Si alloy during its deformation at 350° C. The investigation consists of two steps. Both steps are connected to the monotonic uniaxial compression loading of a cylindrical specimen. During the first step the flow behaviour of the alloy is investigated at the constant <span class="hlt">strain</span> <span class="hlt">rate</span> wihin the range of 0.1-50 s-1 at the temperature range of 350-430° C. During the second step the <span class="hlt">strain</span> <span class="hlt">rate</span> is abruptly increased or decreased from its current value at a fixed engineering <span class="hlt">strain</span> of 17-21%. From the beginning of the test up to the <span class="hlt">strain</span> of 17-21% the value of the <span class="hlt">strain</span> <span class="hlt">rate</span> is constant and equal to either 1 s-1 or 10 s-1. At the <span class="hlt">strain</span> of 17-21% the value of a <span class="hlt">strain</span> <span class="hlt">rate</span> is either increased to 10 s-1 or decreased to 1 s-1. The results of the experimental investigations were used to determine the isothermal flow stress-<span class="hlt">strain</span> curves of the Al-Mg-Si alloy as well as the heat <span class="hlt">effect</span> of plastic deformation of the alloy. On basis of these curves, the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity index m as a function of true <span class="hlt">strain</span> and temperature was determined. This parameter allows to optimize a technological process of hot forging of the aluminium alloy as well as it is very important data for the construction of a phenomenological flow stress model.</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>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> </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://adsabs.harvard.edu/abs/2003APS..DFD.KK006C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003APS..DFD.KK006C"><span>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://hdl.handle.net/2060/20030065962','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030065962"><span>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/2011APS..SHK.Y5002J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011APS..SHK.Y5002J"><span>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('https://www.osti.gov/scitech/biblio/1079844','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1079844"><span><span class="hlt">Strain</span> <span class="hlt">Rate</span> <span class="hlt">Effects</span> on the Energy Absorption of Rapidly Manufactured Composite Tubes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Brighton, Aaron M; Forrest, Mark; Starbuck, J Michael; ERDMAN III, DONALD L; Fox, Bronwyn</p> <p>2009-01-01</p> <p>Quasi-static and intermediate <span class="hlt">rate</span> axial crush tests were conducted on tubular specimens of Carbon/Epoxy (Toray T700/G83C) and Glass/Polypropylene (Twintex). The quasi-static tests were conducted at 10 mm/min (1.67x10-4 m/s); five different crush initiators were used. Tests at intermediate <span class="hlt">rates</span> were performed at speeds of 0.25 m/s, 0.5 m/s, 0.75 m/s 1m/s, 2 m/s and 4 m/s. Quasi-static tests of tubular specimens showed high specific energy absorption (SEA) values with 86 kJ/kg for Carbon/Epoxy specimens. The specific energy absorption of the Glass/Polypropylene specimens was measured to be 29 kJ/kg. Results from the intermediate test <span class="hlt">rates</span> showed that while a decrease in specific energy absorbed was observed as speeds increased, values did not fall below 55kj/kg for carbon specimens or 35 kJ/kg for the Glass/Polypropylene specimens. When compared with steel and aluminium, specific energy absorption values of 15 kJ/kg and 30 kJ/kg respectively, the benefits of using composite materials in crash structures are apparent.</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>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/2060/20040082455','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040082455"><span>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://www.dtic.mil/docs/citations/AD0414975','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD0414975"><span><span class="hlt">EFFECTS</span> OF TEMPERATURE, <span class="hlt">STRAIN</span> <span class="hlt">RATE</span>, AND SWELLING ON THE STRESS-<span class="hlt">STRAIN</span> PROPERTIES OF STYRENEBUTADIENE GUM VULCANIZATES OF VARYING CROSS-LINK DENSITIES,</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p></p> <p>measurements at high temperatures. The Mooney - Rivlin constants were found to depend on temperature, <span class="hlt">strain</span> <span class="hlt">rate</span>, and cross-link density. The constant...within the chains; however, this did not decrease the Mooney - Rivlin C sub 2 term. The ultimate properties (swollen and unswollen), when plotted as log</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>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=Rebound&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DRebound','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950047316&hterms=Rebound&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DRebound"><span>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('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>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('https://www.ncbi.nlm.nih.gov/pubmed/28773023','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28773023"><span>Ultra High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Nanoindentation Testing.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sudharshan Phani, Pardhasaradhi; Oliver, Warren Carl</p> <p>2017-06-17</p> <p><span class="hlt">Strain</span> <span class="hlt">rate</span> dependence of indentation hardness has been widely used to study time-dependent plasticity. However, the currently available techniques limit the range of <span class="hlt">strain</span> <span class="hlt">rates</span> that can be achieved during indentation testing. Recent advances in electronics have enabled nanomechanical measurements with very low noise levels (sub nanometer) at fast time constants (20 µs) and high data acquisition <span class="hlt">rates</span> (100 KHz). These capabilities open the doors for a wide range of ultra-fast nanomechanical testing, for instance, indentation testing at very high <span class="hlt">strain</span> <span class="hlt">rates</span>. With an accurate dynamic model and an instrument with fast time constants, step load tests can be performed which enable access to indentation <span class="hlt">strain</span> <span class="hlt">rates</span> approaching ballistic levels (i.e., 4000 1/s). A novel indentation based testing technique involving a combination of step load and constant load and hold tests that enables measurement of <span class="hlt">strain</span> <span class="hlt">rate</span> dependence of hardness spanning over seven orders of magnitude in <span class="hlt">strain</span> <span class="hlt">rate</span> is presented. A simple analysis is used to calculate the equivalent uniaxial response from indentation data and compared to the conventional uniaxial data for commercial purity aluminum. Excellent agreement is found between the indentation and uniaxial data over several orders of magnitude of <span class="hlt">strain</span> <span class="hlt">rate</span>.</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><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>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('https://www.ncbi.nlm.nih.gov/pubmed/24205490','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24205490"><span>Antibiotic resistance in Helicobacter pylori <span class="hlt">strains</span> and its <span class="hlt">effect</span> on H. pylori eradication <span class="hlt">rates</span> in a single center in Korea.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>An, Byoungrak; Moon, Byung Soo; Kim, Heejung; Lim, Hyun Chul; Lee, Yong Chan; Lee, Gyusang; Kim, Sa-Hyun; Park, Min; Kim, Jong Bae</p> <p>2013-11-01</p> <p>Clarithromycin, amoxicillin, metronidazole, tetracycline, and levofloxacin have been commonly used for the eradication of Helicobacter pylori. We compared the change in antibiotic resistance of H. pylori <span class="hlt">strains</span> during two separate periods and investigated the <span class="hlt">effect</span> of antibiotic resistance on H. pylori eradication. H. pylori <span class="hlt">strains</span> were isolated from 71 patients between 2009 and 2010 and from 94 patients between 2011 and 2012. The distribution of minimal inhibitory concentration (MIC) of 5 antibiotics was assessed using the agar dilution method, and H. pylori eradication based on the antimicrobial susceptibility of the isolates was investigated retrospectively. Antibiotic resistance <span class="hlt">rate</span> against clarithromycin, amoxicillin, tetracycline, metronidazole, and levofloxacin for the 2009-2010 isolates were 7.0% (5/71), 2.8% (2/71), 0% (0/71), 45.1% (32/71), and 26.8% (19/71), respectively, and for the 2011-2012 isolates were 16.0% (15/94), 2.1% (2/94), 0% (0/94), 56.3% (53/94), and 22.3% (21/94), respectively. Multi-drug resistance for 2 or more antibiotics increased slightly from 16.9% (12/71) in the 2009-2010 isolates to 23.4% (22/94) in the 2011-2012 isolates. In follow-up testing of 66 patients, first-line treatment successfully eradicated H. pylori in 50 patients (75.8%) and failed in 4 of 7 patients (57.1%) in a clarithromycin-resistant and amoxicillin-susceptible group. We observed an increase in resistance to clarithromycin and an overall increase in multi-drug resistance during the 2 study periods. The <span class="hlt">effectiveness</span> of the eradication regimen was low with combinations of clarithromycin and amoxicillin, particularly in the clarithromycin-resistant group. Thus, eradication of H. pylori depends upon periodic monitoring of antimicrobial susceptibility.</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>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('http://www.osti.gov/scitech/servlets/purl/543291','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/543291"><span><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://adsabs.harvard.edu/abs/2017MS%26E..181a2022P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MS%26E..181a2022P"><span>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> <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><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('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>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('https://www.ncbi.nlm.nih.gov/pubmed/22886556','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22886556"><span><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> </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/2015ApPhA.121..823H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApPhA.121..823H"><span>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('http://pubs.er.usgs.gov/publication/70187494','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70187494"><span>Using <span class="hlt">strain</span> <span class="hlt">rates</span> to forecast seismic hazards</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Evans, Eileen</p> <p>2017-01-01</p> <p>One essential component in forecasting seismic hazards is observing the gradual accumulation of tectonic <span class="hlt">strain</span> accumulation along faults before this <span class="hlt">strain</span> is suddenly released as earthquakes. Typically, seismic hazard models are based on geologic estimates of slip <span class="hlt">rates</span> along faults and historical records of seismic activity, neither of which records actively accumulating <span class="hlt">strain</span>. But this <span class="hlt">strain</span> can be estimated by geodesy: the precise measurement of tiny position changes of Earth’s surface, obtained from GPS, interferometric synthetic aperture radar (InSAR), or a variety of other instruments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995MMTA...26.1183T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995MMTA...26.1183T"><span><span class="hlt">Effect</span> of cooling <span class="hlt">rate</span> after hot rolling and of multistage <span class="hlt">strain</span> aging on the drawability of low-carbon-steel wire rod</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Taheri, A. Karimi; Maccagno, T. M.; Jonas, J. J.</p> <p>1995-05-01</p> <p>Tensile testing was used to simulate the multistage <span class="hlt">strain</span> aging occurring in low-C steel during the relatively short intervals between dies in a multiple-die wire-drawing machine. The <span class="hlt">effects</span> were examined of three simulated post-hot-rolling cooling <span class="hlt">rates</span> and three thermal treatments on the <span class="hlt">strain</span>-aging susceptibility of a high- and a low-N steel. This was measured by applying a 6 pct tensile <span class="hlt">strain</span>, followed by aging at either 65° or 100 °C for 20 seconds, and then pulling the specimen to failure at room temperature. Increases in flow stress and decreases in the elongation to fracture both indicated high susceptibility to <span class="hlt">strain</span> aging. It was found that the nitrogen content, the cooling <span class="hlt">rate</span> from the hot-rolling temperature to about 300 °C, as well as the cooling <span class="hlt">rate</span> below 300 °C, all have dramatic <span class="hlt">effects</span> on the <span class="hlt">strain</span>-aging behavior. Moreover, multistage <span class="hlt">strain</span> aging is more severe than single-stage <span class="hlt">strain</span> aging. The implications of these observations on increasing the drawability of low-carbon-steel wire are discussed.</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>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>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>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>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><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://adsabs.harvard.edu/abs/2016RuMet2016...34T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016RuMet2016...34T"><span><span class="hlt">Effect</span> of the removal of the surface layer of a TRIP steel sheet on its phase composition after static tension 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>Terent'ev, V. F.; Slizov, A. K.; Sirotinkin, V. P.; Prosvirnin, D. V.; Kobeleva, L. I.; Eliseev, E. A.; Rybal'chenko, O. V.; Ashmarin, A. A.</p> <p>2016-01-01</p> <p>The <span class="hlt">effect</span> of the removal of the surface layer of a thin strip made of austenitic-martensitic VNS9-Sh (23Kh15N5AM3-Sh) TRIP steel on the phase composition of the strip surface is studied after static tension at various <span class="hlt">strain</span> <span class="hlt">rates</span>. An increase in the <span class="hlt">strain</span> <span class="hlt">rate</span> is shown to increase the austenite content in the surface layer of the metal. The removal of a 10-μm-thick surface layer by electropolishing results in an increase in the austenite content due to the initial nonuniform phase composition of the thin TRIP steel strip across its thickness after cold rolling.</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>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>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>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>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>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('http://adsabs.harvard.edu/abs/2005PhRvB..71h5411J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005PhRvB..71h5411J"><span><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><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>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> <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>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/2015JAP...118l3904D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JAP...118l3904D"><span>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>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> </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/2060/20040053579','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040053579"><span>Suppression and Structure of Low <span class="hlt">Strain</span> <span class="hlt">Rate</span> Nonpremixed Flames</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hamins, Anthony; Bundy, Matthew; Park, Woe Chul; Lee, Ki Yong; Logue, Jennifer</p> <p>2003-01-01</p> <p>The agent concentration required to achieve suppression of low <span class="hlt">strain</span> <span class="hlt">rate</span> nonpremixed flames is an important fire safety consideration. In a microgravity environment such as a space platform, unwanted fires will likely occur in near quiescent conditions where <span class="hlt">strain</span> <span class="hlt">rates</span> are very low. Diffusion flames typically become more robust as the <span class="hlt">strain</span> <span class="hlt">rate</span> is decreased. When designing a fire suppression system for worst-case conditions, low <span class="hlt">strain</span> <span class="hlt">rates</span> should be considered. 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 suppressant (N2) added to the fuel stream of low <span class="hlt">strain</span> <span class="hlt">rate</span> methane-air diffusion flames was measured. Flame temperature measurements were attained in the high temperature region of the flame (T greater than 1200 K) by measurement of thin filament emission intensity. The time varying temperature was measured and simulated as the flame made the transition from normal to microgravity conditions and as the flame extinguished.</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>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('http://adsabs.harvard.edu/abs/2009JAP...106e3530V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JAP...106e3530V"><span>On measuring the strength of metals at ultrahigh <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>Vogler, T. J.</p> <p>2009-09-01</p> <p>The <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity of materials is normally measured through a combination of quasistatic, Hopkinson bar, and pressure-shear experiments. Recent advances in uniaxial <span class="hlt">strain</span> ramp loading provide a new means to reach <span class="hlt">strain</span> <span class="hlt">rates</span> significantly higher than achievable in pressure-shear experiments. One way to determine strength in ramp loading is by comparing the uniaxial stress-<span class="hlt">strain</span> response to an appropriate pressure-density response obtained from an equation of state for the material. Using this approach, strengths for aluminum are obtained for <span class="hlt">strain</span> <span class="hlt">rates</span> of 105-108 s-1. Two issues arise in this calculation: heating due to plastic work and the <span class="hlt">effect</span> of the superimposed hydrostatic stress on the strength. Heating due to plastic work is calculated and accounted for within the context of the equation of state for the material in a straightforward manner, but neglecting this heating can lead to significant errors in the calculated strength at higher compression levels. A simple scaling of strength with the pressure-dependent shear modulus is utilized to estimate the strength at zero pressure for ramp loading and pressure-shear experiments. When examined in this manner, the <span class="hlt">strain</span> <span class="hlt">rate</span> dependence of aluminum is found to be less than previously reported, with little increase in strength below <span class="hlt">strain</span> <span class="hlt">rates</span> of about 107s-1. The <span class="hlt">effects</span> on ramp loading strength measurements of heating due to plastic work and of hydrostatic pressure are also examined for copper and tantalum using simple equation of state and strength models. The <span class="hlt">effect</span> of plastic heating is similar for the three materials for a given <span class="hlt">strain</span> level but quite different for a constant stress, with aluminum showing greater <span class="hlt">effects</span> than the other materials. The <span class="hlt">effect</span> of hydrostatic pressure in ramp loading experiments is similar for all three materials, but the <span class="hlt">effect</span> is likely to be much greater in pressure-shear experiments for aluminum than the other materials.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMMR51B2708M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMMR51B2708M"><span><span class="hlt">Strain</span> <span class="hlt">Rate</span> Dependency of Fracture Toughness, Energy Release <span class="hlt">Rate</span> and Geomechanical Attributes of Select Indian Shales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mahanta, B.; Vishal, V.; Singh, T. N.; Ranjith, P.</p> <p>2016-12-01</p> <p>In addition to modern improved technology, it requires detailed understanding of rock fractures for the purpose of enhanced energy extraction through hydraulic fracturing of gas shales and geothermal energy systems. The understanding of rock fracture behavior, patterns and properties such as fracture toughness; energy release <span class="hlt">rate</span>; strength and deformation attributes during fracturing hold significance. Environmental factors like temperature, pressure, humidity, water vapor and experimental condition such as <span class="hlt">strain</span> <span class="hlt">rate</span> influence the estimation of these properties. In this study, the <span class="hlt">effects</span> of <span class="hlt">strain</span> <span class="hlt">rates</span> on fracture toughness, energy release <span class="hlt">rate</span> as well as geomechanical properties like uniaxial compressive strength, Young's modulus, failure <span class="hlt">strain</span>, tensile strength, and brittleness index of gas shales were investigated. In addition to the rock-mechanical parameters, the fracture toughness and the energy release <span class="hlt">rates</span> were measured for three different modes viz. mode I, mixed mode (I-II) and mode II. Petrographic and X-ray diffraction (XRD) analyses were performed to identify the mineral composition of the shale samples. Scanning electron microscope (SEM) analyses were conducted to have an insight about the <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effects</span> on micro-structure of the rock. The results suggest that the fracture toughness; the energy release <span class="hlt">rate</span> as well as other geomechanical properties are a function of <span class="hlt">strain</span> <span class="hlt">rates</span>. At high <span class="hlt">strain</span> <span class="hlt">rates</span>, the strength and stiffness of shale increases which in turn increases the fracture toughness and the energy release <span class="hlt">rate</span> of shale that may be due to stress redistribution during grain fracturing. The fracture toughness and the <span class="hlt">strain</span> energy release <span class="hlt">rates</span> for all the modes (I/I-II/II) are comparable at lower <span class="hlt">strain</span> <span class="hlt">rates</span>, but they vary considerably at higher <span class="hlt">strain</span> <span class="hlt">rates</span>. In all the cases, mode I and mode II fracturing requires minimum and maximum applied energy, respectively. Mode I energy release <span class="hlt">rate</span> is maximum, compared to the other modes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/2388111','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/2388111"><span>The <span class="hlt">effects</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> on the properties of the medial collateral ligament in skeletally immature and mature rabbits: a biomechanical and histological study.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Woo, S L; Peterson, R H; Ohland, K J; Sites, T J; Danto, M I</p> <p>1990-09-01</p> <p>The <span class="hlt">effects</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> on the structural properties of the femur-medial collateral ligament-tibia complex (FMTC) and on the mechanical (material) properties of the medial collateral ligament (MCL) of skeletally immature and skeletally mature rabbits were studied. The FMTCs were tested in tension to failure, at five extension <span class="hlt">rates</span> (0.008 mm/s-113 mm/s). For the FMTCs from the skeletally immature animals, values of load, elongation, and energy absorbed at failure increased substantially with extension <span class="hlt">rates</span>. Such increases also existed for skeletally mature animals, but they were much less in magnitude. All samples from the skeletally immature animals failed by tibial avulsion, whereas samples from the skeletally mature animals failed within the ligament substance. The mechanical properties of the ligament substance were minimally <span class="hlt">strain-rate</span> sensitive for both groups. Histological sections of the ligament substance and insertion sites from the failed samples were examined, and these observations were correlated with the biomechanical findings. For the rabbit model used in this study, we conclude that skeletal maturity has more influence on the biomechanical properties of the MCL than does <span class="hlt">strain</span> <span class="hlt">rate</span>.</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>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/2014SPIE.9040E..15Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014SPIE.9040E..15Y"><span>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://adsabs.harvard.edu/abs/2014JPhCS.500l2006S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JPhCS.500l2006S"><span><span class="hlt">Strain</span> <span class="hlt">rate</span> behavior of magnetorheological materials</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seminuk, Kenneth; Joshi, Vasant; Gump, Jared; Stoltz, Chad; Forbes, Jerry</p> <p>2014-05-01</p> <p><span class="hlt">Strain</span> <span class="hlt">rate</span> response of two Hydroxyl-terminated Polybutadiene/ Iron (HTPB/Fe) compositions under electromagnetic fields has been investigated using a Split Hopkinson Pressure bar arrangement equipped with aluminum bars. Two HTPB/Fe compositions were developed, the first without plasticizer and the second containing plasticizer. Samples were tested with and without the application of a 0.01 Tesla magnetic field. <span class="hlt">Strain</span> gauge data taken from the Split Hopkinson Pressure Bar has been used to determine the extent of change in mechanical properties by inducing a mild electromagnetic field onto each sample. Raw data from <span class="hlt">strain</span> gages was processed using commercial software (Signo) and Excel spreadsheet. It is of particular interest to determine whether the mechanical properties of binder systems can be manipulated by adding ferrous or Magnetostrictive particulates. Data collected from the Split Hopkinson Pressure bar indicate changes in the Mechanical Stress-<span class="hlt">Strain</span> curves and suggest that the impedance of a binder system can be altered by means of a magnetic field.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AIPC..845..809J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AIPC..845..809J"><span>High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Response of an Elastomer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jiao, Tong; Clifton, Rodney J.; Grunschel, Stephen E.</p> <p>2006-07-01</p> <p>Pressure-shear plate impact experiments are used to study the nonlinear dynamic response of an elastomer at shearing <span class="hlt">rates</span> of 105 - 106 s-1. Samples with thicknesses in the range 100 μm - 400 μm are cast between two hard steel plates. Because of the comparatively low impedance of the elastomer, longitudinal waves reverberating through the thickness of the sample — and recorded with a laser interferometer — are used to determine the isentrope of the material under uniaxial <span class="hlt">strain</span> compression. Once the sample is fully compressed a shear wave arrives and imposes a simple shearing deformation. From the transverse velocity, measured interferometrically at the rear surface of the sandwich target, the shear stress and the transverse velocity at the rear surface of the sample are determined. These measurements provide an indication of the shearing resistance of the material under pressure. When the longitudinal unloading wave arrives from the rear surface of the target, these same measurements provide an indication of the shearing resistance of the material at zero pressure. Because the sample adheres to the bounding plates the reflection of unloading waves from both the rear surface of the flyer and the rear surface of the target allows the sample to be <span class="hlt">strained</span> in uniaxial extension. Thus, from a single experiment, one obtains the response of the elastomer in uniaxial <span class="hlt">strain</span> compression, simple shear and uniaxial <span class="hlt">strain</span> extension.</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><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://www.osti.gov/scitech/servlets/purl/305920','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/305920"><span>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>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://adsabs.harvard.edu/abs/2012AGUFM.G43B0920K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.G43B0920K"><span>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/1997PhDT.......211G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997PhDT.......211G"><span>High-<span class="hlt">strain-rate</span> behavior of metal matrix composites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guden, Mustafa</p> <p></p> <p>Dynamic loading response is an important design parameter, which is critical in severe applications where impact loading occurs, but which has been little investigated to date for MMCs. Those MMCs which have been tested at high <span class="hlt">strain-rates</span> so far have been diverse in terms of matrix alloy and reinforcement type, size and shape, making comparisons difficult. In this study, four different MMCs, SiC particulate and whisker reinforced, Alsb2Osb3 short and long fiber reinforced, representing currently available MMC groups, have been compression tested at quasi-static and high <span class="hlt">strain</span> <span class="hlt">rates</span> ({˜}10sp3\\ ssp{-1}). It has been shown that the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity of the composite is very similar to that of the corresponding unreinforced alloy for the following composites: SiCsb{p}/2024 Al MMC, SiCsb{w}/2124-T6 Al MMC, Alsb2Osb3 (Saffil) short fiber reinforced Al-1.2wt%Cu in a direction normal to the Planar Random Fiber Plane, and Alsb2Osb3 (FP) long fiber reinforced Al-3wt%Li MMC tested in the transverse direction. In Alsb2Osb3 Saffil short fiber reinforced Al-1.2wt%Cu MMC tested in a direction parallel to the Planar Random Fiber Plane and FP-Alsb2Osb3 long fiber MMC in the longitudinal direction, the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivities of the flow stress or maximum stress were found to be higher than those of the monolithic alloy. The increased <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity in Saffil short fiber reinforced MMC was found to be a combined <span class="hlt">effect</span> of matrix <span class="hlt">rate</span> sensitivity and load carried by fiber until about 5% <span class="hlt">strains</span>. The increased <span class="hlt">rate</span> sensitivity of FP reinforced MMC in the longitudinal direction was due to the increased fiber buckling stress which scaled with matrix shear stress. Microscopic observations have shown that, in SiC whisker reinforced MMC, the failure was controlled by thermal softening and <span class="hlt">strain</span> localization at high <span class="hlt">strain</span> <span class="hlt">rates</span>. In Saffil reinforced MMC, the reduced fiber fragment size at high <span class="hlt">strain</span> <span class="hlt">rates</span> and increased extent of matrix voiding were the dominant</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><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('http://adsabs.harvard.edu/abs/2015EPJWC..9402019C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9402019C"><span><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>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/2015EPJWC..9401080M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9401080M"><span>A <span class="hlt">rate</span>-dependent Hosford-Coulomb model for predicting ductile fracture 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>Marcadet, Stephane J.; Roth, Christian C.; Erice, Borja; Mohr, Dirk</p> <p>2015-09-01</p> <p>The Hosford-Coulomb model incorporates the important <span class="hlt">effect</span> of the Lode angle parameter in addition to the stress triaxiality to predict the initiation of ductile fracture. A <span class="hlt">strain-rate</span> dependent extension of the Hosford-Coulomb model is presented to describe the results from low, intermediate and high <span class="hlt">strain</span> <span class="hlt">rate</span> fracture experiments on advanced high strength steels (DP590 and TRIP780). The model predictions agree well with the experimental observation of an increase in ductility as function of <span class="hlt">strain</span> <span class="hlt">rate</span> for stress states ranging from uniaxial to equi-biaxial tension.</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><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>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> </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/2015AGUFM.S13B2817K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.S13B2817K"><span>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('https://www.osti.gov/scitech/biblio/55411','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/55411"><span><span class="hlt">Strain</span> energy release <span class="hlt">rates</span> for skin-stiffener debonding</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Raju, I.S.; Sistla, R.; Krishnamurthy, T.</p> <p>1995-06-01</p> <p>Fracture mechanics analyses of a debonded skin-stiffener configuration using three-dimensional (3D) finite element method are presented. Twenty noded isoparametric elements were used to model the debond configurations. The virtual crack closure technique (VCCT) was used to evaluate the <span class="hlt">strain</span> energy release <span class="hlt">rate</span> distributions across the debond front. The <span class="hlt">strain</span> energy release <span class="hlt">rate</span> (G-value) distributions showed that there is a boundary layer <span class="hlt">effect</span> near the ends of the debond and there is an elevation in the G-values in the region of the blade of the stiffener. The analyses also showed that the mode-II is the dominant mode for this debond configuration.</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>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>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/2012NatCo...3E1164L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012NatCo...3E1164L"><span>High <span class="hlt">strain</span> <span class="hlt">rate</span> deformation of layered nanocomposites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</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>2012-11-01</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/1999PPCF...41..967P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999PPCF...41..967P"><span>On the role of <span class="hlt">strain</span> <span class="hlt">rate</span> and vorticity in plasmas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Polygiannakis, J. M.; Moussas, X.</p> <p>1999-08-01</p> <p>It is shown that the magnetic field's local evolution in plasmas is directly affected by an interplay between the deformation (<span class="hlt">strain</span> <span class="hlt">rate</span>) and the self-rotation (vorticity) of the elementary plasma fluid volumes. At regions of strong <span class="hlt">strain</span> <span class="hlt">rate</span>, the fast local convergence or divergence of the flow causes exponential increase or decrease of the field's components, respectively. At regions of strong vorticity, faster directional than magnitude variations of the field occur, explaining the field alignment of the field minimum-variance direction and the random wandering of the field's tip on a sphere, both observed in the solar wind plasma, even in the absence of Alfvén waves. We further investigate the coupling between the maximum <span class="hlt">strain-rate</span> direction and the local magnetic field, that was previously deduced from magnetic field measurements in the outer heliosphere. Cases of long-lasting, non-Parkerian, radial heliospheric magnetic field are also shown to be periods of field-aligned <span class="hlt">strain</span> <span class="hlt">rate</span>. A statistical proof for this alignment is given, assuming that the small-scale field fluctuations are weakly stationary and time reversible. We further propose a generalization of the Stokesian fluid stress-<span class="hlt">strain</span> relation to the case of one-fluid, collisionless MHD plasmas, including the <span class="hlt">effects</span> of turbulent viscosity and magnetically induced shearing motion. For a negligible or isotropic or `field-aligned' thermal pressure tensor, the proposed `Stokesian plasma' relation implies the field alignment of the solar wind plasma <span class="hlt">strain-rate</span> direction and leads to anisotropic stress-<span class="hlt">strain</span> balance equations, related to those of `firehose' plasma instability. The field alignment of a principal <span class="hlt">strain-rate</span> direction leads to simplifications in the magnetic-induction equation, especially in the case of force-free fields. For the simplified case of homogeneous, isotropic and incompressible plasma turbulence, the proposed stress-<span class="hlt">strain-rate</span> relation implies that the velocity and</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>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> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20999337','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20999337"><span>Pressure <span class="hlt">effects</span> on nonpremixed <span class="hlt">strained</span> flames</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Pons, Laetitia; Darabiha, Nasser; Candel, Sebastien</p> <p>2008-01-15</p> <p>This article deals with the <span class="hlt">effect</span> of pressure on the structure and consumption <span class="hlt">rate</span> of nonpremixed <span class="hlt">strained</span> flames. An analysis based on the fast chemistry limit indicates that the flame thickness is inversely proportional to the square root of pressure and that the flame structure may be described in terms of a similarity variable that scales like the product of pressure and the <span class="hlt">strain</span> <span class="hlt">rate</span> to the power 1/2. This scaling rule also applies to flames submitted to a time-variable <span class="hlt">strain</span> <span class="hlt">rate</span> provided that the frequencies characterizing these changes are low compared to the mean <span class="hlt">strain</span> <span class="hlt">rate</span>. It is also confirmed that reactants consumption <span class="hlt">rates</span> per unit flame surface vary like the square root of pressure and that this rule holds for time-variable <span class="hlt">strain</span> <span class="hlt">rates</span> of arbitrary nature. Complex chemistry calculations carried out over a broad range of operating pressures indicate that the pressure dependences deduced analytically are remarkably accurate and can be used for a broad range of <span class="hlt">strain</span> <span class="hlt">rates</span>, excluding values in the near vicinity of extinction conditions, where finite <span class="hlt">rate</span> chemistry <span class="hlt">effects</span> become important and influence the flame response to pressure. Thus, it appears that the pressure exponent characterizing the heat release <span class="hlt">rate</span> in nonpremixed <span class="hlt">strained</span> flames is essentially constant and equal to 1/2. This exponent is independent of finite <span class="hlt">rate</span> chemistry <span class="hlt">effects</span>, except when conditions are close to extinction. (author)</p> </li> <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>High-<span class="hlt">Strain</span> <span class="hlt">Rate</span> Testing of Gun Propellants</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">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/2017AIPC.1835b0007S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1835b0007S"><span>Deformation behavior of open-cell dry natural rubber foam: <span class="hlt">Effect</span> of different concentration of blowing agent and compression <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>Samsudin, M. S. F.; Ariff, Z. M.; Ariffin, A.</p> <p>2017-04-01</p> <p>Compression and deformation behavior of partially open cell natural rubber (NR) foam produced from dry natural rubber (DNR), were investigated by performing compressive deformation at different <span class="hlt">strains</span> and <span class="hlt">strain</span> <span class="hlt">rates</span>. Different concentrations of sodium bicarbonate as a blowing agent (BA) were utilized, from 4 to 16 phr in order to produce foams with range of cell size and morphology. Overall, increasing of blowing agent concentration had significantly changed relative foam density. Compression stress-<span class="hlt">strain</span> curves of the foams exhibited that the compression behavior was directly correlated to the foam cells morphology and physical density. Pronounced changes were noticed for foams with bigger cells particularly at 4 phr concentration of BA where the compression stress at plateau region was greater compared to those with higher concentration of BA. Cell deformation progressive images confirmed that the foams demonstrated small degree of struts bending at 15% of <span class="hlt">strain</span> and followed by continuous severe struts bending and elastic buckling up to 50% of <span class="hlt">strain</span>. Compression test at different <span class="hlt">strain</span> <span class="hlt">rates</span> revealed that the <span class="hlt">strain</span> <span class="hlt">rate</span> factor only affected the foams with 4 phr of BA by causing immediate increment in the compression stress value when higher <span class="hlt">strain</span> <span class="hlt">rate</span> was applied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1222108','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1222108"><span>HIGH-<span class="hlt">RATE</span> FORMABILITY OF HIGH-STRENGTH ALUMINUM ALLOYS: A STUDY ON OBJECTIVITY OF MEASURED <span class="hlt">STRAIN</span> 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>Upadhyay, Piyush; Rohatgi, Aashish; Stephens, Elizabeth V.; Davies, Richard W.; Catalini, David</p> <p>2015-02-18</p> <p>Al alloy AA7075 sheets were deformed at room temperature at <span class="hlt">strain-rates</span> exceeding 1000 /s using the electrohydraulic forming (EHF) technique. A method that combines high speed imaging and digital image correlation technique, developed at Pacific Northwest National Laboratory, is used to investigate high <span class="hlt">strain</span> <span class="hlt">rate</span> deformation behavior of AA7075. For <span class="hlt">strain-rate</span> sensitive materials, the ability to accurately model their high-<span class="hlt">rate</span> deformation behavior is dependent upon the ability to accurately quantify the <span class="hlt">strain-rate</span> that the material is subjected to. This work investigates the objectivity of software-calculated <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> by varying different parameters within commonly used commercially available digital image correlation software. Except for very close to the time of crack opening the calculated <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rates</span> are very consistent and independent of the adjustable parameters of the software.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.G41A0913F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.G41A0913F"><span>Geodetic <span class="hlt">strain-rate</span> field of Iberia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fernandes, R. M.; Bos, M. S.; Apolinário, J. P.; Dias, N. A.; Neves, M. L.; Miranda, J. M.</p> <p>2013-12-01</p> <p>Currently, the number of available GNSS (Global Navigation Satellite System) CORS (Continuous Operating Reference Stations) in Iberia reaches almost 300 stations distributed over several national and regional networks. The majority of these stations were installed for surveying and cadaster applications (RTK networks). Although the required stability of the monuments for such applications is lower than for geodynamic purposes, we demonstrate, by investigating the level and type of noise, that the majority of these stations provide reliable information about their secular tectonic motions. The large number and relative uniform distribution over the entire Iberia also facilitate to identify stations showing abnormal and unexplained artifacts in their time-series. We computed the uniform velocity field using the stations with observations spanning 3 years or longer (~100 stations). Most of Iberia shows no relative motion with respect to Eurasia - their residuals are below the computed uncertainty of the velocity. However, the southern part of Iberia is affected by the convergence of Nubia towards Iberia. The clockwise rotation of the southern part of the Peninsula is clearly observed with an increment of the motion towards west until the Gibraltar area. This is also clearly observed in the derived <span class="hlt">strain</span> <span class="hlt">rate</span> field, which shows significant deformation <span class="hlt">rates</span> in this region. The residual westward motion is still evident in the south of Portugal even if the magnitude is smaller - suggesting this area is already more stable with respect to the plate boundary. This work is carried out in the framework of the European Project EPOS and Portuguese Project SMOG (PTDC/CTE-ATM/119922/2010).</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>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://adsabs.harvard.edu/abs/2007APS..SHK.Q6003A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007APS..SHK.Q6003A"><span>High <span class="hlt">Strain</span>, <span class="hlt">Strain</span> <span class="hlt">Rate</span> Behavior of PTFE/Al/W</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Addiss, John; Cai, Jing; Walley, Steve; Proud, William; Nesterenko, Vitali</p> <p>2007-06-01</p> <p>Conventional dropweight technique was modified to accommodate low amplitude signals from low strength, cold isostatically pressed energetic ``heavy'' composites of polytetrafluoroethylene (PTFE)/AL/W. The fracture strength, <span class="hlt">strain</span> and post-critical behaviour of fractured samples were measured for samples of different porosity and W grain size (the masses of each component being the same in each case). Unusual phenomenon of significantly higher strength (55 MPa) of porous composites (density 5.9 g/cc) with small tungsten particles (1 micron) in comparison with strength (32 MPa) of dense composites (7.1 g/cc) with larger tungsten particles (20 micron) was observed. This is attributed to force chains created by a network of small tungsten particles. Interrupted tests at the different level of <span class="hlt">strains</span> revealed mechanism of fracture under dynamic compression.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/977941','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/977941"><span>High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Compression Testing of Ceramics and Ceramic Composites.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Blumenthal, W. R.</p> <p>2005-01-01</p> <p>The compressive deformation and failure behavior of ceramics and ceramic-metal composites for armor applications has been studied as a function of <span class="hlt">strain</span> <span class="hlt">rate</span> at Los Alamos National Laboratory since the late 1980s. High <span class="hlt">strain</span> <span class="hlt">rate</span> ({approx}10{sup 3} s{sup -1}) uniaxial compression loading can be achieved using the Kolsky-split-Hopkinson pressure bar (SHPB) technique, but special methods must be used to obtain valid strength results. This paper reviews these methods and the limitations of the Kolsky-SHPB technique for this class of materials. The Kolsky-split-Hopkinson pressure bar (Kolsky-SHPB) technique was originally developed to characterize the mechanical behavior of ductile materials such as metals and polymers where the results can be used to develop <span class="hlt">strain-rate</span> and temperature-dependent constitutive behavior models that empirically describe macroscopic plastic flow. The flow behavior of metals and polymers is generally controlled by thermally-activated and <span class="hlt">rate</span>-dependent dislocation motion or polymer chain motion in response to shear stresses. Conversely, the macroscopic mechanical behavior of dense, brittle, ceramic-based materials is dominated by elastic deformation terminated by rapid failure associated with the propagation of defects in the material in response to resolved tensile stresses. This behavior is usually characterized by a distribution of macroscopically measured failure strengths and <span class="hlt">strains</span>. The basis for any <span class="hlt">strain-rate</span> dependence observed in the failure strength must originate from <span class="hlt">rate</span>-dependence in the damage and fracture process, since uniform, uniaxial elastic behavior is <span class="hlt">rate</span>-independent (e.g. inertial <span class="hlt">effects</span> on crack growth). The study of microscopic damage and fracture processes and their <span class="hlt">rate</span>-dependence under dynamic loading conditions is a difficult experimental challenge that is not addressed in this paper. The purpose of this paper is to review the methods that have been developed at the Los Alamos National Laboratory to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000AIPC..505..679J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000AIPC..505..679J"><span>High-<span class="hlt">strain</span> <span class="hlt">rate</span> testing of HMX-based explosive</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>John, Henry J.; Alamo, Mike F.</p> <p>2000-04-01</p> <p>A split Hopkinson pressure bar (SHPB) was used to measure the mechanical behavior of Navy explosive PBXC-129 (a high-solids-loaded explosive material) with <span class="hlt">strain</span> <span class="hlt">rates</span> up to ˜3500 s-1. The PBXC-129's high-<span class="hlt">strain</span> response is typical of other explosive and propellant behavior. At higher <span class="hlt">strain</span> <span class="hlt">rates</span>, the PBXC-129 shows significant stiffening with a possible reaction. Stress-<span class="hlt">strain</span> curves and material properties for PBXC-129 are presented in this paper.</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>High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Mechanical Properties of Glassy Polymers</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">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>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/1998AIPC..429..603J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998AIPC..429..603J"><span>High <span class="hlt">strain</span> <span class="hlt">rate</span> testing of AP/Al/HTPB solid propellants</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>John, Henry J.; Hudson, Frank E.; Robbs, Rodney</p> <p>1998-07-01</p> <p>Ammonium perchlorate (AP), aluminum (Al), and hydroxy-terminater polybutadiene (HTPB) solid propellant samples were subjected to <span class="hlt">strain</span> <span class="hlt">rates</span> up to 700 sec-1 using the Split-Hopkinson Pressure Bar apparatus. The issues are the <span class="hlt">effects</span> of temperature on the mechanical behavior of these propellants at high <span class="hlt">strain</span> <span class="hlt">rates</span>. <span class="hlt">Strain</span> <span class="hlt">rates</span> were between 100 sec-1 and 700 sec-1 over wide range of temperature regions. Included in this paper are the <span class="hlt">strain</span> <span class="hlt">rates</span>, <span class="hlt">strain</span>, and stress curves and material response properties for Aluminum, AP, and HTPB based propellants formulation.</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>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> </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://adsabs.harvard.edu/abs/2005APS..SHK.F7028A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005APS..SHK.F7028A"><span>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://adsabs.harvard.edu/abs/2017JSV...407..240M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JSV...407..240M"><span>On <span class="hlt">strain-rate</span> independent damping in continuum mechanics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mulder, Gerben</p> <p>2017-10-01</p> <p><span class="hlt">Strain-rate</span> independent damping is a theory of energy dissipation in solids. It is based on the assumption that an increase or decrease in the <span class="hlt">strain</span>-energy density correlates with a multiplication of 1+η or 1-η respectively, of the material stiffness matrix, with 0≤ η <<1 with η either a constant or a function of the <span class="hlt">strain</span>-energy density. This type of damping has a loss (Watt m-3) of η times the absolute value of the <span class="hlt">rate</span> of change of the <span class="hlt">strain</span>-energy density. For uni-axial <span class="hlt">strain</span> and a suitable function of the <span class="hlt">strain</span>-energy density, the energy dissipation (Joule m-3) due to an infinitesimal change of the <span class="hlt">strain</span> is <span class="hlt">strain-rate</span> independent and proportional to the absolute value of the <span class="hlt">strain</span> raised to a power ranging from 1 to 2. This is an idealization of tests results, based on forced harmonic <span class="hlt">strain</span> cycles, with an energy dissipation (Joule m-3 cycle-1) found to be nearly frequency independent and almost proportional to the <span class="hlt">strain</span> amplitude raised to a power ranging from 2 to 3. The PDEs derived for <span class="hlt">strain-rate</span> independent damping can be solved for 1, 2 or 3 dimensions via direct integration, provided that the software supports PDE coefficients that are functions of the solution and its space and time derivatives. A 3D problem with 22,000 DOF's and 10,000 time steps was solved successfully and convincingly.</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><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/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>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('http://www.osti.gov/scitech/servlets/purl/1329630','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1329630"><span>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/scitech/biblio/1329630','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1329630"><span>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://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>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('http://adsabs.harvard.edu/abs/2013APS..MARB24003B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APS..MARB24003B"><span>Atomistic simulations of high <span class="hlt">strain</span> <span class="hlt">rate</span> loading of nanocrystals</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bringa, E. M.; Tramontina, D.; Ruestes, C. J.; Tang, Y.; Meyers, M. A.; Gunkelmann, N.; Urbassek, H. M.</p> <p>2013-03-01</p> <p>Materials loaded at high <span class="hlt">strain</span> <span class="hlt">rates</span> can reach extreme temperature and pressure conditions. Most experiments on loading of simple materials use poly crystals, while most atomistic simulations of shock wave loading deal with single crystals, due to the higher computational cost of running polycrystal samples. Of course, atomistic simulations of polycrystals with micron-sized grains are beyond the capabilities of current supercomputers. On the other hand, nanocrystals (nc) with grain sizes below 50 nm can be obtained experimentally and modeled reasonably well at high <span class="hlt">strain</span> <span class="hlt">rates</span>, opening the possibility of nearly direct comparison between atomistic molecular dynamics (MD) simulations and experiments using high power lasers. We will discuss MD simulations and links to experiments for nc Cu and Ni, as model f.c.c. solids, and nc Ta and Fe, as model b.c.c. solids. In all cases, the microstructure resulting from loading depends strongly on grain size, <span class="hlt">strain</span> <span class="hlt">rate</span> and peak applied pressure. We will also discuss <span class="hlt">effects</span> related to target porosity in nc's. E.M.B. thanks funding from PICT2008-1325.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA134342','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA134342"><span>High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Characterization of Materials</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1983-08-01</p> <p>OISTRIOUTION STATEIMENT rte the obstrwt eterd in ill.4* 20. It diffrent fros Report) 1S. SUPPI.CMENTARYV NOTtHS is. Kay WORDS (Coems ess, e side if aoemovand...Design ( Dimensions i~n Inches). 38 bushing mounts, an oven was designed and fabricated, and new <span class="hlt">strain</span> gauges were mounted. The essential equations used...annealed. The thinness of the warhead liners dictated that only compression specimens could be machined and tested. The dimensions of the compressive</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>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://adsabs.harvard.edu/abs/2008IJMPB..22.1255K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008IJMPB..22.1255K"><span>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('http://adsabs.harvard.edu/abs/2016AGUFM.G31A1041A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.G31A1041A"><span>a Comparison of Geodetic and Seismic <span class="hlt">Strain</span> <span class="hlt">Rates</span> in Turkey</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aktug, B.</p> <p>2016-12-01</p> <p>The seismic potential of a region is often characterized by the deformation <span class="hlt">rates</span> observed by the modern geodetic methods and seismic history during the instrumental period compiled in catalogues. While both are related, a direct comparison is not straightforward due to the various factors including the incomplete catalogues both in time and space, parameterization of seismic <span class="hlt">strain</span> <span class="hlt">rates</span>, discretization of seismic domain, and the difficulty in the definition of seismic volume. In this study, the most complete and up-to-date seismic catalogues and GNSS velocities were employed to derive and compare the geodetic and seismic <span class="hlt">rates</span>, the <span class="hlt">effect</span> of different zonations were tested, the possible implications and correlation of the difference between geodetic and seismic <span class="hlt">rates</span> with the static stress drop, time after the last earthquake and heat flow were analyzed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/2592653','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/2592653"><span><span class="hlt">Effect</span> of inoculation <span class="hlt">rate</span> of selected <span class="hlt">strains</span> of lactic acid bacteria on fermentation and in vitro digestibility of grass-legume forage.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Harrison, J H; Soderlund, S D; Loney, K A</p> <p>1989-09-01</p> <p>Grass-legume forage was used to evaluate the <span class="hlt">effect</span> of inoculation <span class="hlt">rate</span> of selected <span class="hlt">strains</span> of lactic acid bacteria on fermentation and in vitro digestibility during 57 d of ensiling. Chopped forage (DM = 28%) was ensiled in 4 to 6-kg quantities and treated as: 1) control, 10(3) epiphytic lactic acid bacteria; 2) 10(5) added lactic acid bacteria; and 3) 10(6) added lactic bacteria/g of wet forage. Samples were obtained for analyses on d 0, 1, 2, 3, 6, 10, 14, 29, and 57 of fermentation. Treated silages were observed to have: 1) greater quantities of lactic acid bacteria, 2) a greater proportion of homofermentative lactic acid bacteria, and 3) lactic acid bacteria with greater biological activity. Addition of each amount of lactic acid bacteria: 1) increased the <span class="hlt">rate</span> of utilization of water-soluble carbohydrate and decline in pH, 2) limited the formation of NH3 N, and 3) increased the in vitro digestibility of DM and ADF. No differences were observed in the lactic acid content of the silages after 57 d of fermentation.</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>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://adsabs.harvard.edu/abs/2010MsT..........8P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010MsT..........8P"><span>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://www.osti.gov/scitech/servlets/purl/1170524','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1170524"><span>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('https://www.osti.gov/scitech/biblio/175242','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/175242"><span>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/2016CMT....28..977A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016CMT....28..977A"><span>A numerical method for determining the <span class="hlt">strain</span> <span class="hlt">rate</span> intensity factor under plane <span class="hlt">strain</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>Alexandrov, S.; Kuo, C.-Y.; Jeng, Y.-R.</p> <p>2016-07-01</p> <p>Using the classical model of rigid perfectly plastic solids, the <span class="hlt">strain</span> <span class="hlt">rate</span> intensity factor has been previously introduced as the coefficient of the leading singular term in a series expansion of the equivalent <span class="hlt">strain</span> <span class="hlt">rate</span> in the vicinity of maximum friction surfaces. Since then, many <span class="hlt">strain</span> <span class="hlt">rate</span> intensity factors have been determined by means of analytical and semi-analytical solutions. However, no attempt has been made to develop a numerical method for calculating the <span class="hlt">strain</span> <span class="hlt">rate</span> intensity factor. This paper presents such a method for planar flow. The method is based on the theory of characteristics. First, the <span class="hlt">strain</span> <span class="hlt">rate</span> intensity factor is derived in characteristic coordinates. Then, a standard numerical slip-line technique is supplemented with a procedure to calculate the <span class="hlt">strain</span> <span class="hlt">rate</span> intensity factor. The distribution of the <span class="hlt">strain</span> <span class="hlt">rate</span> intensity factor along the friction surface in compression of a layer between two parallel plates is determined. A high accuracy of this numerical solution for the <span class="hlt">strain</span> <span class="hlt">rate</span> intensity factor is confirmed by comparison with an analytic solution. It is shown that the distribution of the <span class="hlt">strain</span> <span class="hlt">rate</span> intensity factor is in general discontinuous.</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>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('http://adsabs.harvard.edu/abs/2016APS..MARR21009H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..MARR21009H"><span>Spall Response of Tantalum at Extreme <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>Hahn, Eric; Germann, Tim; Meyers, Marc</p> <p></p> <p><span class="hlt">Strain-rate</span> and microstructure play a significant role in the ultimate mechanical response of materials. Using non-equilibrium molecular dynamics simulations, we characterize the ductile tensile failure of single and nanocrystalline tantalum over multiple orders of magnitude of <span class="hlt">strain-rate</span>. This comparison is extended to over nine orders of magnitude including experimental results from resent laser shock campaigns. Spall strength primarily follows a power law dependence with <span class="hlt">strain-rate</span> over this extensive range. In all cases, voids nucleate heterogeneously at pre-existing defects. Predictions based on traditional theory suggest that, as <span class="hlt">strain-rate</span> increases, tensile strength should increase. Alternatively, as grain size decreases, tensile strength may decrease due to an increased propensity to fail at a growing volume fraction of grain boundaries. <span class="hlt">Strain-rate</span> and grain size dictate void nucleation sites by changing the type and density of available defects: vacancies, dislocations, twins, and grain boundaries.</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('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>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> <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>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('http://adsabs.harvard.edu/abs/2016JMEP...25.2878M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JMEP...25.2878M"><span>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://adsabs.harvard.edu/abs/2002AIPC..620..693S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AIPC..620..693S"><span><span class="hlt">Strain</span> <span class="hlt">Rate</span> Sensitivity of Graphite/Polymer Laminate Composites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Syed, Izhar H.; Brar, N. S.</p> <p>2002-07-01</p> <p><span class="hlt">Strain</span> <span class="hlt">rate</span> sensitivities of Graphite/Epoxy and Graphite/Peek laminate composites are investigated by measuring their stress-<span class="hlt">strain</span> response at <span class="hlt">strain</span> <span class="hlt">rates</span> of 0.001/s, 0.1/s, and 400/s. Tension specimens of the composite laminates are fabricated in a dog-bone shape. Stress-<span class="hlt">strain</span> data at quasi-static <span class="hlt">rates</span> of 0.001/s and 0.1/s are obtained using a servohydraulic test system. High <span class="hlt">strain</span> <span class="hlt">rate</span> data are produced with a Direct Tension Split Hopkinson Bar (DTSHB). A tensile stress pulse is generated in the DTSHB by impacting a stopper flange at the end of the incident bar with an aluminum/polymeric tube launched around the incident bar. The failure (flow) tensile stress of Graphite/Epoxy increases from 240 MPa to 280±10 MPa (ɛ = 0.06) when the <span class="hlt">strain</span> <span class="hlt">rate</span> is raised from 0.001/s to 400/s. For Graphite/Peek, failure (flow) tension stress increases from 175 MPa at a <span class="hlt">strain</span> <span class="hlt">rate</span> of 0.001/s to 270±20 MPa at a <span class="hlt">strain</span> <span class="hlt">rate</span> of 400/s.</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>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><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('https://www.ncbi.nlm.nih.gov/pubmed/20047945','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20047945"><span><span class="hlt">Strain</span> <span class="hlt">rate</span> sensitivity of skin tissue under thermomechanical loading.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhou, B; Xu, F; Chen, C Q; Lu, T J</p> <p>2010-02-13</p> <p>There have been limited studies addressing the thermally dependent mechanical properties of skin tissue, although this can contribute to a variety of medical applications. To address this, an experimental study on the tensile behaviour of pig skin tissue under different thermal loading conditions and different mechanical stretching <span class="hlt">rates</span> was performed. The results indicate that there is a significant variation among skin tensile behaviours under different temperatures and loading <span class="hlt">rates</span>, which is correlated with dermal collagen denaturation. The Ogden model was used to summarize the <span class="hlt">effect</span> of the <span class="hlt">strain</span> <span class="hlt">rate</span> and the temperature upon the measured constitutive response through two parameters (alpha and mu). These results can be used in future models to improve clinical thermal treatments for skin tissue.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997APS..SHK..L144C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997APS..SHK..L144C"><span>High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Response of Tungsten Heavy Alloy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chang, S. N.</p> <p>1997-07-01</p> <p>Tungsten heavy alloy (WHA) is studied to investigate the <span class="hlt">effect</span> of thickness variation on its dynamic behaviors. Exploding Bridgwire (EBW) detonator has been used to drive the alloy plate. The particle velocity at the rear free surface was measured by means of VISAR. The experimental technique in this paper has been introduced to simply obtain the Hugoniot elastic limit and spall strength of materials of small disc plate (diamter of 7mm) with varying thickness. Peak pressure decay is analyzed as a function of the thickness of samples. The fracture behavior of WHA caused by this high <span class="hlt">strain</span> <span class="hlt">rate</span> is similar to that due to the conventional tensile test.</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>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/2006APS..MARR42010L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006APS..MARR42010L"><span>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://adsabs.harvard.edu/abs/2015JNEng..12c6002S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JNEng..12c6002S"><span>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>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>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('http://adsabs.harvard.edu/abs/2012MTDM...16..361O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012MTDM...16..361O"><span>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('https://www.osti.gov/scitech/biblio/20001576','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20001576"><span>The <span class="hlt">effects</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> and minor boron addition on brittle-to-ductile transition temperature in gamma TiAl alloy</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lin, T.L.; Wang, Y.; Liu, J.; Law, C.C.</p> <p>1999-07-01</p> <p>Brittle-to-ductile transition (BDT) temperature (T{sub BD}) was evaluated according to temperature dependence of tensile properties under different <span class="hlt">strain</span> <span class="hlt">rates</span> from 10{sup {minus}5} to 10{sup {minus}1} s{sup {minus}1} in two-phase Ti-47Al-2Mn-2Nb and Ti-47Al-2Mn-2Nb-0.8TiB{sub 2} alloys with nearly lamellar microstructure. Based on the <span class="hlt">strain</span> <span class="hlt">rate</span> dependence of the determined T{sub BD} values, apparent BDT activation energies were determined using Zener-Hollomon factor. Tensile fracture surfaces were observed using a scanning electron microscope while deformation substructures were investigated by transmission electron microscopy. It was found that the BDTT of both alloys increased sharply with the <span class="hlt">strain</span> <span class="hlt">rate</span> and that the minor addition of 0.8 vol% TiB{sub 2} reduced T{sub BD} by about 100K at the same <span class="hlt">strain</span> <span class="hlt">rate</span>. The TiB{sub 2} addition also decreases the apparent BDT activation energy from 324 to 256 kJ/mol. Both of these values approximate to self- or inter-diffusion of Ti and Al atoms in TiAl phase. Transgranular fracture and dimple fracture were found dominant in fracture surfaces below and above T{sub BD}, respectively. The most common 1/2[{l{underscore}angle}110] ordinary dislocations were found to begin climb at around T{sub BD}. All this evidence, as well as a theoretical calculation using the Nabarro Model, add up to a conclusion that the BDT is controlled by dislocation climb in both alloys.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16580516','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16580516"><span>Measurement of <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> by echocardiography: ready for prime time?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Marwick, Thomas H</p> <p>2006-04-04</p> <p><span class="hlt">Strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> (SR) are measures of deformation that are basic descriptors of both the nature and the function of cardiac tissue. These properties may now be measured using either Doppler or two-dimensional ultrasound techniques. Although these measurements are feasible in routine clinical echocardiography, their acquisition and analysis nonetheless presents a number of technical challenges and complexities. Echocardiographic <span class="hlt">strain</span> and SR imaging has been applied to the assessment of resting ventricular function, the assessment of myocardial viability using low-dose dobutamine infusion, and stress testing for ischemia. Resting function assessment has been applied in both the left and the right ventricles, and may prove particularly valuable for identifying myocardial diseases and following up the treatment response. Although the evidence base is limited, SR imaging seems to be feasible and <span class="hlt">effective</span> for the assessment of myocardial viability. The use of the technique for the detection of ischemia during stress echocardiography is technically challenging and likely to evolve further. The clinical availability of <span class="hlt">strain</span> and SR measurement may offer a solution to the ongoing need for quantification of regional and global cardiac function. Nonetheless, these techniques are susceptible to artifact, and further technical development is necessary.</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><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.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5378936','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5378936"><span><span class="hlt">Strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> echocardiography in children with Wilson’s disease</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Cemşit, Karakurt; Serkan, Çelik; Ayşe, Selimoğlu; İlknur, Varol; Hamza, Karabiber; Saim, Yoloğlu</p> <p>2016-01-01</p> <p>Summary Objective This study aimed to evaluate <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> echocardiography in children with Wilson’s disease to detect early cardiac dysfunction. Methods In this study, 21 patients with Wilson’s disease and a control group of 20 age- and gender-matched healthy children were included. All the patients and the control group were evaluated with two-dimensional (2D) and colour-coded conventional transthoracic echocardiography by the same paediatric cardiologist using the same echocardiography machine (Vivid E9, GE Healthcare, Norway) in standard precordial positions, according to the American Society of Echocardiography recommendations. 2D <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> echocardiography were performed after the ECG probes of the echocardiography machine were adjusted for ECG monitoring. Longitudinal, transverse and radial <span class="hlt">strain</span>, and <span class="hlt">strain</span> <span class="hlt">rate</span> were assessed from six basal and six mid-ventricular segments of the left ventricle, as recommended by the American Society of Echocardiography. Results Left ventricular wall thickness, systolic and diastolic diameters, left ventricular diameters normalised to body surface area, end-systolic and end-diastolic volumes, cardiac output and cardiac index values were within normal limits and statistically similar in the patient and control groups (p < 0.05). Global <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span>: the patient group had a statistically significant lower peak A longitudinal velocity of the left basal point and peak E longitudinal velocity of the left basal (VAbasR) point, and higher global peak A longitudinal/circumferential <span class="hlt">strain</span> <span class="hlt">rate</span> (GSRa) compared to the corresponding values of the control group (p < 0.05). Radial <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span>: end-systolic rotation [ROT (ES)] was statistically significantly lower in the patient group (p < 0.05). Longitudinal <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span>: end-systolic longitudinal <span class="hlt">strain</span> [SLSC (ES)] and positive peak transverse <span class="hlt">strain</span> (STSR peak P) were statistically significantly lower in the patient group (p</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><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://adsabs.harvard.edu/abs/2016APLM....4f4107S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APLM....4f4107S"><span>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> </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://hdl.handle.net/2060/19990081117','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990081117"><span><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://www.dtic.mil/docs/citations/ADA179488','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA179488"><span>High-<span class="hlt">Strain-Rate</span> behavior of Hydrated Cement Paste.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">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>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.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2936195','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2936195"><span>Gradients of <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> in the hollow muscular organs of soft-bodied animals</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Thompson, Joseph T.; Taylor, Kari R.; Gentile, Christopher</p> <p>2010-01-01</p> <p>The cylindrical shape of soft-bodied invertebrates is well suited to functions in skeletal support and locomotion, but may result in a previously unrecognized cost—large non-uniformities in muscle <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> among the circular muscle fibres of the body wall. We investigated such gradients of <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> in the mantle of eight long-finned squid Doryteuthis pealeii and two oval squid Sepioteuthis lessoniana. Transmural gradients of circumferential <span class="hlt">strain</span> were present during all jets (n = 312); i.e. for a given change in the circumference of the outer surface of the mantle, the inner surface experienced a greater proportional change. The magnitude of the difference increased with the amplitude of the mantle movement, with circular muscle fibres at the inner surface of the mantle experiencing a total range of <span class="hlt">strains</span> up to 1.45 times greater than fibres at the outer surface during vigorous jets. Differences in <span class="hlt">strain</span> <span class="hlt">rate</span> between the circular fibres near the inner versus the outer surface of the mantle were also present in all jets, with the greatest differences occurring during vigorous jetting. The transmural gradients of circumferential <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> we describe probably apply not only to squids and other coleoid cephalopods, but also to diverse soft-bodied invertebrates with hollow cylindrical or conical bodies and muscular organs. PMID:20106857</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20106857','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20106857"><span>Gradients of <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> in the hollow muscular organs of soft-bodied animals.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thompson, Joseph T; Taylor, Kari R; Gentile, Christopher</p> <p>2010-08-23</p> <p>The cylindrical shape of soft-bodied invertebrates is well suited to functions in skeletal support and locomotion, but may result in a previously unrecognized cost-large non-uniformities in muscle <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> among the circular muscle fibres of the body wall. We investigated such gradients of <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> in the mantle of eight long-finned squid Doryteuthis pealeii and two oval squid Sepioteuthis lessoniana. Transmural gradients of circumferential <span class="hlt">strain</span> were present during all jets (n = 312); i.e. for a given change in the circumference of the outer surface of the mantle, the inner surface experienced a greater proportional change. The magnitude of the difference increased with the amplitude of the mantle movement, with circular muscle fibres at the inner surface of the mantle experiencing a total range of <span class="hlt">strains</span> up to 1.45 times greater than fibres at the outer surface during vigorous jets. Differences in <span class="hlt">strain</span> <span class="hlt">rate</span> between the circular fibres near the inner versus the outer surface of the mantle were also present in all jets, with the greatest differences occurring during vigorous jetting. The transmural gradients of circumferential <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> we describe probably apply not only to squids and other coleoid cephalopods, but also to diverse soft-bodied invertebrates with hollow cylindrical or conical bodies and muscular organs.</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>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>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('https://www.osti.gov/scitech/biblio/1116483','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1116483"><span>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>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('http://adsabs.harvard.edu/abs/2016APS..MARX21002L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..MARX21002L"><span>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> <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>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><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('http://hdl.handle.net/2060/20040086471','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040086471"><span>Creep <span class="hlt">Strain</span> and <span class="hlt">Strain</span> <span class="hlt">Rate</span> Response of 2219 Al Alloy at High Stress Levels</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Taminger, Karen M. B.; Wagner, John A.; Lisagor, W. Barry</p> <p>1998-01-01</p> <p>As a result of high localized plastic deformation experienced during proof testing in an International Space Station connecting module, a study was undertaken to determine the deformation response of a 2219-T851 roll forging. After prestraining 2219-T851 Al specimens to simulate <span class="hlt">strains</span> observed during the proof testing, creep tests were conducted in the temperature range from ambient temperature to 107 C (225 F) at stress levels approaching the ultimate tensile strength of 2219-T851 Al. <span class="hlt">Strain</span>-time histories and <span class="hlt">strain</span> <span class="hlt">rate</span> responses were examined. The <span class="hlt">strain</span> <span class="hlt">rate</span> response was extremely high initially, but decayed rapidly, spanning as much as five orders of magnitude during primary creep. Select specimens were subjected to incremental step loading and exhibited initial creep <span class="hlt">rates</span> of similar magnitude for each load step. Although the creep <span class="hlt">rates</span> decreased quickly at all loads, the creep <span class="hlt">rates</span> dropped faster and reached lower <span class="hlt">strain</span> <span class="hlt">rate</span> levels for lower applied loads. The initial creep <span class="hlt">rate</span> and creep <span class="hlt">rate</span> decay associated with primary creep were similar for specimens with and without prestrain; however, prestraining (<span class="hlt">strain</span> hardening) the specimens, as in the aforementioned proof test, resulted in significantly longer creep life.</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>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('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>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('https://www.ncbi.nlm.nih.gov/pubmed/18644460','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18644460"><span>Geobacter sulfurreducens <span class="hlt">strain</span> engineered for increased <span class="hlt">rates</span> of respiration.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Izallalen, Mounir; Mahadevan, Radhakrishnan; Burgard, Anthony; Postier, Bradley; Didonato, Raymond; Sun, Jun; Schilling, Christopher H; Lovley, Derek R</p> <p>2008-09-01</p> <p>Geobacter species are among the most <span class="hlt">effective</span> microorganisms known for the bioremediation of radioactive and toxic metals in contaminated subsurface environments and for converting organic compounds to electricity in microbial fuel cells. However, faster <span class="hlt">rates</span> of electron transfer could aid in optimizing these processes. Therefore, the Optknock <span class="hlt">strain</span> design methodology was applied in an iterative manner to the constraint-based, in silico model of Geobacter sulfurreducens to identify gene deletions predicted to increase respiration <span class="hlt">rates</span>. The common factor in the Optknock predictions was that each resulted in a predicted increase in the cellular ATP demand, either by creating ATP-consuming futile cycles or decreasing the availability of reducing equivalents and inorganic phosphate for ATP biosynthesis. The in silico model predicted that increasing the ATP demand would result in higher fluxes of acetate through the TCA cycle and higher <span class="hlt">rates</span> of NADPH oxidation coupled with decreases in flux in reactions that funnel acetate toward biosynthetic pathways. A <span class="hlt">strain</span> of G. sulfurreducens was constructed in which the hydrolytic, F(1) portion of the membrane-bound F(0)F(1) (H(+))-ATP synthase complex was expressed when IPTG was added to the medium. Induction of the ATP drain decreased the ATP content of the cell by more than half. The cells with the ATP drain had higher <span class="hlt">rates</span> of respiration, slower growth <span class="hlt">rates</span>, and a lower cell yield. Genome-wide analysis of gene transcript levels indicated that when the higher <span class="hlt">rate</span> of respiration was induced transcript levels were higher for genes involved in energy metabolism, especially in those encoding TCA cycle enzymes, subunits of the NADH dehydrogenase, and proteins involved in electron acceptor reduction. This was accompanied by lower transcript levels for genes encoding proteins involved in amino acid biosynthesis, cell growth, and motility. Several changes in gene expression that involve processes not included in the in silico</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MTDM..tmp...33W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MTDM..tmp...33W"><span>A thermovisco-hyperelastic constitutive model of HTPB propellant with damage at intermediate <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>Wang, Zhejun; Qiang, Hongfu; Wang, Tiejun; Wang, Guang; Hou, Xiao</p> <p>2017-08-01</p> <p>The uniaxial compressive tests at different temperatures (223-298 K) and <span class="hlt">strain</span> <span class="hlt">rates</span> ( 0.40-63 s^{-1}) are reported to study the properties of hydroxyl-terminated polybutadiene (HTPB) propellant at intermediate <span class="hlt">strain</span> <span class="hlt">rates</span>, using a new INSTRON testing machine. The experimental results indicate that the compressive properties (mechanical properties and damage) of HTPB propellant are remarkably affected by temperature and <span class="hlt">strain</span> <span class="hlt">rate</span> and display significant nonlinear material behaviors at large <span class="hlt">strains</span> under all the test conditions. Continuously decreasing temperature and increasing <span class="hlt">strain</span> <span class="hlt">rate</span>, the characteristics of stress-<span class="hlt">strain</span> curves and damage for HTPB propellant are more complex and are significantly different from that at room temperature or at lower <span class="hlt">strain</span> <span class="hlt">rates</span>. A new constitutive model was developed to describe the compressive behaviors of HTPB propellant at room temperature and intermediate <span class="hlt">strain</span> <span class="hlt">rates</span> by simply coupling the <span class="hlt">effect</span> of <span class="hlt">strain</span> <span class="hlt">rate</span> into the conventional hyperelastic model. Based on the compressive behaviors of HTPB propellant and the nonlinear viscoelastic constitutive theories, a new thermovisco-hyperelastic constitutive model with damage was proposed to predict the stress responses of the propellant at low temperatures and intermediate <span class="hlt">strain</span> <span class="hlt">rates</span>. In this new model, the damage is related to the viscoelastic properties of the propellant. Meanwhile, the <span class="hlt">effect</span> of temperature on the hyperelastic properties, viscoelastic properties and damage are all considered by the macroscopical method. The constitutive parameters in the proposed constitutive models were identified by the genetic algorithm (GA)-based optimization method. By comparing the predicted and experimental results, it can be found that the developed constitutive models can correctly describe the uniaxial compressive behaviors of HTPB propellant at intermediate <span class="hlt">strain</span> <span class="hlt">rates</span> and different temperatures.</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>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('http://hdl.handle.net/2060/20020060784','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020060784"><span>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('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>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> </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://adsabs.harvard.edu/abs/2015APS..MARJ43003H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..MARJ43003H"><span><span class="hlt">Effect</span> of temperature on segmental mobility is reduced, but not eliminated during constant <span class="hlt">strain</span> <span class="hlt">rate</span> deformation of poly(methyl methacrylate) glasses</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hebert, Kelly; Bending, Benjamin; Ricci, Josh; Ediger, M. D.</p> <p>2015-03-01</p> <p>Deformation of polymer glasses is typically nonlinear and not understood at a molecular level. During deformation, segmental motion in polymer glasses can be accelerated by over a factor of 1000. While temperature has a big impact on the segmental motion of polymer glasses in the absence of deformation, some workers suggest that segmental mobility in polymer glasses undergoing deformation should be independent of temperature. We have measured segmental mobility in poly(methyl methacrylate) glasses during constant <span class="hlt">strain</span> <span class="hlt">rate</span> deformation at four different temperatures using a probe reorientation method. We find that during deformation, the dependence of segmental mobility on temperature is significantly reduced, though not eliminated. This is in qualitative agreement with the work of Chen and Schweizer. We also find that the KWW β parameter increases during deformation, indicating a narrower distribution of segmental relaxation times. At a given <span class="hlt">strain</span> <span class="hlt">rate</span>, this increase of the KWW β parameter is larger at lower temperature. We thank the National Science Foundation (DMR-1404614) for support of this research.</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>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('https://www.ncbi.nlm.nih.gov/pubmed/22560644','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22560644"><span>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. Copyright © 2012 Elsevier Ltd. All rights reserved.</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>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.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>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('https://www.ncbi.nlm.nih.gov/pubmed/24883355','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24883355"><span>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('http://hdl.handle.net/2060/19890015180','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890015180"><span>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('http://adsabs.harvard.edu/abs/2010APS..DPPJO6007R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010APS..DPPJO6007R"><span>Material deformation dynamics at ultrahigh 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, B. A.; Park, H. S.; Maddox, B. R.; May, M. J.; Pollaine, S. M.; Prisbrey, S. T.; Rudd, R. E.; Hawreliak, J. A.; Perry, T. S.; Comley, A. J.; Wark, J. S.; Meyers, M. A.</p> <p>2010-11-01</p> <p>Solid-state dynamics experiments at extreme pressures, up to 10 Mbar, and <span class="hlt">strain</span> <span class="hlt">rates</span> (1.e6 -1.e8 1/s) are being developed for the NIF laser. The experimental methods are being developed on the Omega laser facility. VISAR measurements establish the ramped, high-pressure conditions. Recovery experiments offer a look at the residual microstructure. Dynamic diffraction measurements allow phase, shear stress (strength), and possibly twin volume fraction and dislocation density to be inferred. Constitutive models for material strength at these conditions by comparing 2D simulations with experiments measuring the Rayleigh-Taylor instability evolution in solid-state samples of vanadium and tantalum. The material deformation likely falls into the phonon drag regime. We estimate of the (microscopic) phonon drag coefficient, by relating to the (macroscopic) <span class="hlt">effective</span> lattice viscosity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998AIPC..429..415C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998AIPC..429..415C"><span>High <span class="hlt">strain</span> <span class="hlt">rate</span> response of a tungsten heavy alloy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chang, S. N.; Choi, J. H.</p> <p>1998-07-01</p> <p>The <span class="hlt">effect</span> of thickness change of a tungsten heavy alloy (WHA) on its dynamic behaviors has been studied. Exploding bridgwire (EBW) detonator has been used to drive the alloy plate. The particle velocity at the rear free surface of a specimen was measured by means of VISAR. Simple experimental technique has been introduced herein to obtain the Hugoniot elastic limit and spall strength of materials in the form of small disc plate (diameter of ˜7 mm) with varying thickness. The peak pressure decay is analyzed as a function of time for traveling of the wave through each specimen. The fracture behavior of WHA caused by the high <span class="hlt">strain</span> <span class="hlt">rate</span> herein is similar to that due to the Charpy impact test.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JNuM..489...33T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JNuM..489...33T"><span><span class="hlt">Strain-rate</span> dependent fatigue behavior of 316LN stainless steel in high-temperature water</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tan, Jibo; Wu, Xinqiang; Han, En-Hou; Ke, Wei; Wang, Xiang; Sun, Haitao</p> <p>2017-06-01</p> <p>Low cycle fatigue behavior of forged 316LN stainless steel was investigated in high-temperature water. It was found that the fatigue life of 316LN stainless steel decreased with decreasing <span class="hlt">strain</span> <span class="hlt">rate</span> from 0.4 to 0.004 %s-1 in 300 °C water. The stress amplitude increased with decreasing <span class="hlt">strain</span> <span class="hlt">rate</span> during fatigue tests, which was a typical characteristic of dynamic <span class="hlt">strain</span> aging. The fatigue cracks mainly initiated at pits and slip bands. The interactive <span class="hlt">effect</span> between dynamic <span class="hlt">strain</span> aging and electrochemical factors on fatigue crack initiation is discussed.</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>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/2006AIPC..845.1511B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AIPC..845.1511B"><span>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://www.osti.gov/scitech/servlets/purl/10189802','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10189802"><span>High <span class="hlt">strain</span> <span class="hlt">rate</span> superplasticity in metals and composites</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Nieh, T.G.; Wadsworth, J.; Higashi, K.</p> <p>1993-07-01</p> <p>Superplastic behavior at very high <span class="hlt">strain</span> <span class="hlt">rates</span> (at or above 1 s{sup {minus}1}) in metallic-based materials is an area of increasing interest. The phenomenon has been observed quite extensively in metal alloys, metal-matrix composites (MMC), and mechanically-alloyed (MA) materials. In the present paper, experimental results on high <span class="hlt">strain</span> <span class="hlt">rate</span> behavior in 2124 Al-based materials, including Zr-modified 2124, SiC-reinforced 2124, MA 2124, and MA 2124 MMC, are presented. Except for the required fine grain size, details of the structural requirements of this phenomenon are not yet understood. Despite this, a systematic approach to produce high <span class="hlt">strain</span> <span class="hlt">rate</span> superplasticity (HSRS) in metallic materials is given in this paper. Evidences indicate that the presence of a liquid phase, or a low melting point region, at boundary interfaces is responsible for HSRS.</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>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('http://adsabs.harvard.edu/abs/2016AGUFM.G51B1115O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.G51B1115O"><span><span class="hlt">Strain</span> <span class="hlt">rate</span> orientations near the Coso Geothermal Field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ogasa, N. T.; Kaven, J. O.; Barbour, A. J.; von Huene, R.</p> <p>2016-12-01</p> <p>Many geothermal reservoirs derive their sustained capacity for heat exchange in large part due to continuous deformation of preexisting faults and fractures that permit permeability to be maintained. Similarly, enhanced geothermal systems rely on the creation of suitable permeability from fracture and faults networks to be viable. Stress measurements from boreholes or earthquake source mechanisms are commonly used to infer the tectonic conditions that drive deformation, but here we show that geodetic data can also be used. Specifically, we quantify variations in the horizontal <span class="hlt">strain</span> <span class="hlt">rate</span> tensor in the area surrounding the Coso Geothermal Field (CGF) by analyzing more than two decades of high accuracy differential GPS data from a network of 14 stations from the University of Nevada Reno Geodetic Laboratory. To handle offsets in the data, from equipment changes and coseismic deformation, we segment the data, perform a piecewise linear fit and take the average of each segment's <span class="hlt">strain</span> <span class="hlt">rate</span> to determine secular velocities at each station. With respect to North America, all stations tend to travel northwest at velocities ranging from 1 to 10 mm/yr. The nearest station to CGF shows anomalous motion compared to regional stations, which otherwise show a coherent increase in network velocity from the northeast to the southwest. We determine <span class="hlt">strain</span> <span class="hlt">rates</span> via linear approximation using GPS velocities in Cartesian reference frame due to the small area of our network. Principal <span class="hlt">strain</span> <span class="hlt">rate</span> components derived from this inversion show maximum extensional <span class="hlt">strain</span> <span class="hlt">rates</span> of 30 nanostrain/a occur at N87W with compressional <span class="hlt">strain</span> <span class="hlt">rates</span> of 37nanostrain/a at N3E. These results generally align with previous stress measurements from borehole breakouts, which indicate the least compressive horizontal principal stress is east-west oriented, and indicative of the basin and range tectonic setting. Our results suggest that the CGF represents an anomaly in the crustal deformation field, which</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><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('https://ntrs.nasa.gov/search.jsp?R=19900034881&hterms=hydrogen+diffusion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dhydrogen%2Bdiffusion','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900034881&hterms=hydrogen+diffusion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dhydrogen%2Bdiffusion"><span><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>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>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://adsabs.harvard.edu/abs/2017EGUGA..1911165P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1911165P"><span>Temporal evolution of <span class="hlt">strain</span> <span class="hlt">rates</span> at western Greenland moulins</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Poinar, Kristin; Andrews, Lauren; Chu, Vena; Moon, Twila; Nowicki, Sophie</p> <p>2017-04-01</p> <p>Moulins are key sources for subglacial water across western Greenland. The <span class="hlt">rate</span> and timing at which they deliver surface meltwater to the subglacial system are crucial inputs for ice-sheet hydrology models. Intensive field campaigns coupled to remote sensing efforts have provided, to date, information on the timing of supraglacial lake drainages and water flux through the consequent moulins, but predicting the dates of moulin activation has remained an area of active research. This is vital for the construction of spatially variable basal-input hydrographs for models that will predict the future evolution of Greenland ice flow and sliding. In this study, we combine multiple remote sensing datasets to investigate the degree to which local <span class="hlt">strain</span> <span class="hlt">rates</span> can predict moulin activation dates, as indicated by supraglacial lake drainage events. We find that over the period 2009-2011 in the Pâkitsoq region, moulins with more-tensile background (wintertime InSAR-derived) <span class="hlt">strain</span> <span class="hlt">rates</span> tend to activate first, followed by moulins in less-tensile background <span class="hlt">strain</span> regimes. This pattern is relatively consistent across years, although we find that background <span class="hlt">strain</span> <span class="hlt">rates</span> are less important in explaining the date of moulin activation than are moulin elevation or cumulative days of runoff. In the Russell Glacier area, we examine the temporal evolution of summertime, Landsat-derived <span class="hlt">strain</span> <span class="hlt">rates</span> at moulin locations. Principal component analysis shows that <span class="hlt">strain</span> <span class="hlt">rates</span> at moulin locations increased abruptly over June 2012, independent of moulin elevation; <span class="hlt">strain</span> <span class="hlt">rates</span> in localities without moulins varied more smoothly in time. We also compare the <span class="hlt">strain</span> <span class="hlt">rate</span> time series at each moulin to lake drainage dates derived from MODIS and Landsat imagery from 2012. We hypothesize that the contrasting bedrock topography of the regions (Pâkitsoq is rougher than Russell at the few-km scale) may drive variations in moulin opening patterns across the two regions. Our results will have</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('http://adsabs.harvard.edu/abs/2012JMEP...21.2263J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JMEP...21.2263J"><span>Gas Pressure Profile Prediction from Variable <span class="hlt">Strain</span> <span class="hlt">Rate</span> Deformation Paths in AA5083 Bulge Forming</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jarrar, F. S.; Hector, L. G.; Khraisheh, M. K.; Deshpande, K.</p> <p>2012-11-01</p> <p>Two approaches to gas pressure profile prediction for bulge forming of AA5083 sheet under Quick Plastic Forming (QPF) conditions at 450 °C were investigated. The first was based on an algorithm internal to ABAQUS™ wherein the gas pressure results from maintaining a constant <span class="hlt">effective</span> target <span class="hlt">strain</span> <span class="hlt">rate</span> at the dome pole. In the second, the nonlinear long wavelength stability analysis was combined with a single creep mechanism material model that accounts for hardening/softening. A series of stability curves, which denote combinations of <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> for unmitigated thinning and, ultimately, rupture of an AA5083 bar, were computed. These are based on a parameter that characterizes an assumed geometric non-uniformity, η. The associated uniaxial <span class="hlt">strains</span> and <span class="hlt">strain</span> <span class="hlt">rates</span> were expressed in terms of von Mises <span class="hlt">effective</span> <span class="hlt">strains</span> and <span class="hlt">strains</span> <span class="hlt">rates</span>, and pressure profiles were computed. An ancillary approach to variable <span class="hlt">strain</span> <span class="hlt">rate</span> path prediction based on a thinning factor was used to suggest a suitable value of η in the stability analysis for a reasonable thinning level at the end of forming. Key advantages and disadvantages of both approaches to pressure profile prediction are examined relative to bulge forming time and thinning at a 50-mm dome displacement.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EPJWC...639008R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EPJWC...639008R"><span>Determination of Tensile Properties of Polymers 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>Reiter, M.; Major, Z.</p> <p>2010-06-01</p> <p>In the field of high <span class="hlt">rate</span> testing of polymers the measured properties are highly dependent on the applied methodology. Hence, the test setup as whole but in particular also the geometrical type of specimen plays a decisive role. The widely used standard for the determination of tensile properties of polymers (ISO527-2) was extended by a novel standard (ISO18872:2007), which is targeted on the determination of tensile properties at high <span class="hlt">strain</span> <span class="hlt">rates</span>. In this standard also a novel specimen shape is proposed. Hand in hand with the introduction of new specimen geometry the question of comparability arises. To point out the differences in stress-<span class="hlt">strain</span> response of the ISO18872 specimen and the ISO527-2 multipurpose specimen tensile tests over a wide loading <span class="hlt">rate</span> range were conducted in this paper. A digital image correlation system in combination with a high speed camera was used to characterize the local material behaviour. Different parameters like nominal stress, true stress, nominal <span class="hlt">strain</span>, true <span class="hlt">strain</span> as well as volumetric <span class="hlt">strain</span> were determined and used to compare the two specimen geometries.</p> </li> <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>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('http://www.osti.gov/scitech/servlets/purl/626461','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/626461"><span>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> <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>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://www.osti.gov/scitech/servlets/purl/6667062','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6667062"><span>Mechanical and microstructural response of Ni sub 3 Al at high <span class="hlt">strain</span> <span class="hlt">rate</span> and elevated temperatures</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sizek, H.W.; Gray, G.T. III.</p> <p>1990-01-01</p> <p>In this paper, 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 Ni{sub 3}Al will be presented. The <span class="hlt">strain</span> <span class="hlt">rate</span> response of Ni{sub 3}Al was studied at <span class="hlt">strain</span> <span class="hlt">rates</span> from 10{sup {minus}3} s{sup {minus}1} (quasi-static) to 10{sup 4} s{sup {minus}1} using a Split Hopkinson Pressure Bar. The Hopkinson Bar tests were conducted at temperatures ranging from 77K to 1273K. At high <span class="hlt">strain</span> <span class="hlt">rates</span> the flow strength increased significantly with increasing temperature, similar to the behavior observed at quasi-static <span class="hlt">rates</span>. The work hardening <span class="hlt">rates</span> increased with <span class="hlt">strain</span> <span class="hlt">rate</span> and varied with temperatures. The work hardening <span class="hlt">rates</span>, appeared to be significantly higher than those found for Ni270. The substructure evolution was characterized utilizing TEM. The defect generation and <span class="hlt">rate</span> sensitivity of Ni{sub 3}Al are also discussed as a function of <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature. 15 refs., 4 figs.</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>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.osti.gov/scitech/servlets/purl/932063','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/932063"><span>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://www.dtic.mil/docs/citations/ADA261683','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA261683"><span>Mechanical Response of Gun Propellant Beds at Low <span class="hlt">Strain</span> <span class="hlt">Rates</span></span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1993-02-01</p> <p>SUBTITLE 5. FUNDING NUMBERS IL161 102AH43 Mechanical Response of Gun Propellant Beds at Low <span class="hlt">Strain</span> <span class="hlt">Rates</span> So AUTHOR(S) Robert J. Lieb and Michael G. Leadore...REFERENCES 1. K. P. Resnik , "Charge Development for Advanced 105-mm Penetrator," 22nd JANNAF Com- bustion Meeting, CPIA Publication 432, Vol. II, pp</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>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('https://www.ncbi.nlm.nih.gov/pubmed/15769537','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15769537"><span>Shrinkage <span class="hlt">strain-rates</span> of dental resin-monomer and composite systems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Atai, Mohammad; Watts, David C; Atai, Zahra</p> <p>2005-08-01</p> <p>The purpose of this study was to investigate the shrinkage <span class="hlt">strain</span> <span class="hlt">rate</span> of different monomers, which are commonly used in dental composites and the <span class="hlt">effect</span> of monomer functionality and molecular mass on the <span class="hlt">rate</span>. Bis-GMA, TEGDMA, UDMA, MMA, HEMA, HPMA and different ratios of Bis-GMA/TEGDMA were mixed with Camphorquinone and Dimethyl aminoethyle methacrylate as initiator system. The shrinkage <span class="hlt">strain</span> of the samples photopolymerised at Ca. 550 mW/cm2 and 23 degrees C was measured using the bonded-disk technique of Watts and Cash (Meas. Sci. Technol. 2 (1991) 788-794), and initial shrinkage-<span class="hlt">strain</span> <span class="hlt">rates</span> were obtained by numerical differentiation. Shrinkage-<span class="hlt">strain</span> <span class="hlt">rates</span> rose rapidly to a maximum, and then fell rapidly upon vitrification. <span class="hlt">Strain</span> and initial <span class="hlt">strain</span> <span class="hlt">rate</span> were dependent upon monomer functionality, molecular mass and viscosity. <span class="hlt">Strain</span> <span class="hlt">rates</span> were correlated with Bis-GMA in Bis-GMA/TEGDMA mixtures up to 75-80 w/w%, due to the higher molecular mass of Bis-GMA affecting termination reactions, and then decreased due to its higher viscosity affecting propagation reactions. Monofunctional monomers exhibited lower <span class="hlt">rates</span>. UDMA, a difunctional monomer of medium viscosity, showed the highest shrinkage <span class="hlt">strain</span> <span class="hlt">rate</span> (P < 0.05). Shrinkage <span class="hlt">strain</span> <span class="hlt">rate</span>, related to polymerization <span class="hlt">rate</span>, is an important factor affecting the biomechanics and marginal integrity of composites cured in dental cavities. This study shows how this is related to monomer molecular structure and viscosity. The results are significant for the production, optimization and clinical application of dental composite restoratives.</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>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>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>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://www.osti.gov/scitech/servlets/purl/9510','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/9510"><span>Intermediate <span class="hlt">Strain-Rate</span> Loading - Techniques and Applications</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chhabildas, L.C.; Reinhart, W.D.; Holland, K.G.</p> <p>1999-07-22</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/2060/19920011638','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19920011638"><span>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>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('https://www.ncbi.nlm.nih.gov/pubmed/27810728','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27810728"><span>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>. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.</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>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>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> </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('http://hdl.handle.net/2060/20000121259','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000121259"><span>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/2011GeoJI.185..703W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011GeoJI.185..703W"><span>Comparison of GPS <span class="hlt">strain</span> <span class="hlt">rate</span> computing methods and their reliability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, Yanqiang; Jiang, Zaisen; Yang, Guohua; Wei, Wenxin; Liu, Xiaoxia</p> <p>2011-05-01</p> <p>Using modelled and simulated data for comparison of several methods to compute GPS <span class="hlt">strain</span> <span class="hlt">rate</span> fields in terms of their precision and robustness reveals that least-squares collocation is superior. Large scale (75°E-135°E and 20°N-50°N) analyses of 1° grid sampling data and decimated 50 per cent data by resampling (then erasing data in two 5°× 10° region) reveal that the Delaunay method has poor performance and that the other three methods show high accuracy. The correlation coefficients between theoretical results and calculated results obtained with different errors in input data show that the order in terms of robustness, from good to bad, is least-squares collocation, spherical harmonics, multisurface function and the Delaunay method. The influence of data sparseness on different methods shows that least-squares collocation is better than spherical harmonics and multisurface function when sample data are distributed from a 2° grid to a 1° grid. Analysis to medium scale (90°E-120°E, 25°N-40°N) in 1°-0.5° grid sampling data reveals that least-squares collocation is superior to other methods in terms of robustness and sensitivity to data sparseness, but their difference is slight. <span class="hlt">Strain</span> <span class="hlt">rate</span> results obtained for the Chinese mainland using GPS data from 1999 to 2004 show that the spherical harmonics method has edge <span class="hlt">effects</span> and that its value and range increase concomitantly with increased sparseness. The multisurface function method shows non-steady-state characteristics; the errors of results increase concomitantly with increased sparseness. The least-squares collocation method shows steady characteristics. The errors of results show no significant increase even though 50 per cent of input data are decimated by resampling. The spherical harmonics and multisurface function methods are affected by the geometric distribution of input data, but the least-squares collocation method is not.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1047146','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1047146"><span><span class="hlt">Strain</span> <span class="hlt">rate</span>, temperature and representative length scale influence on plasticity and yield stress in copper</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dupont, Virginie; Germann, Timothy C</p> <p>2011-01-18</p> <p>Shock compression of materials constitutes a complex process involving high <span class="hlt">strain</span> <span class="hlt">rates</span>, elevated temperatures and compression of the lattice. Materials properties are greatly affected by temperature, the representative length scale and the <span class="hlt">strain</span> <span class="hlt">rate</span> of the deformation. Experimentally, it is difficult to study the dynamic microscopic mechanisms that affect materials properties following high intensity shock loading, but they can be investigated using molecular dynamics (MD) simulations. Moreover, MD allows a better control over some parameters. We are using MD simulations to study the <span class="hlt">effect</span> of the <span class="hlt">strain</span> <span class="hlt">rate</span>, representative length scale and temperature on the properties of metals during compression. A half-million-atom Cu sample is subjected to <span class="hlt">strain</span> <span class="hlt">rates</span> ranging from 10{sup 7} s{sup -1} to 10{sup 12} s{sup -1} at different temperatures ranging from 50K to 1500K. Single crystals as well as polycrystals are investigated. Plasticity mechanisms as well as the evolution of the micro- and macro-yield stress are observed. Our results show that the yield stress increases with increasing <span class="hlt">strain</span> <span class="hlt">rate</span> and decreasing temperature. We also show that the <span class="hlt">strain</span> <span class="hlt">rate</span> at which the transition between constant and increasing yield stress as a function of the temperature occurs increases with increasing temperature. Calculations at different grain sizes will give an insight into the grain size <span class="hlt">effect</span> on the plasticity mechanisms and the yield stress.</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>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('http://www.dtic.mil/docs/citations/ADA528977','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA528977"><span>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="http://www.dtic.mil/">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('http://adsabs.harvard.edu/abs/2017ApCM..tmp...99M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApCM..tmp...99M"><span>Characterization of a New Fully Recycled Carbon Fiber Reinforced Composite Subjected to High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Tension</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Meftah, H.; Tamboura, S.; Fitoussi, J.; BenDaly, H.; Tcharkhtchi, A.</p> <p>2017-08-01</p> <p>The aim of this study is the complete physicochemical characterization and <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effect</span> multi-scale analysis of a new fully recycled carbon fiber reinforced composites for automotive crash application. Two composites made of 20% wt short recycled carbon fibers (CF) are obtained by injection molding. The morphology and the degree of dispersion of CF in the matrixes were examined using a new ultrasonic method and SEM. High <span class="hlt">strain</span> tensile behavior up to 100 s-1 is investigated. In order to avoid perturbation due to inertial <span class="hlt">effect</span> and wave propagation, the specimen geometry was optimized. The elastic properties appear to be insensitive to the <span class="hlt">strain</span> <span class="hlt">rate</span>. However, a high <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effect</span> on the local visco-plasticity of the matrix and fiber/matrix interface visco-damageable behavior is emphasized. The predominant damage mechanisms evolve from generalized matrix local ductility at low <span class="hlt">strain</span> <span class="hlt">rate</span> regime to fiber/matrix interface debonding and fibers pull-out at high <span class="hlt">strain</span> <span class="hlt">rate</span> regime.</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><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>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('https://www.ncbi.nlm.nih.gov/pubmed/26968547','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26968547"><span>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('http://adsabs.harvard.edu/abs/2013APS..SHK.V6002T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APS..SHK.V6002T"><span>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://www.osti.gov/scitech/servlets/purl/15005365','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15005365"><span>Materials Science at the Extremes 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; Cavallo, R M; Edwards, M J; Lasinski, B F; Lorenz, K T; Lorenzana, H E; McNaney, J; Pollaine, S M; Rowley, D P; Yaakobi, B</p> <p>2003-08-20</p> <p>Solid state experiments at very high pressures and <span class="hlt">strain</span> <span class="hlt">rates</span> are possible on high power laser facilities, albeit over brief intervals of time and spatial small scales. A new shockless drive has been developed on the Omega laser. VISAR measurements establish the high <span class="hlt">strain</span> <span class="hlt">rates</span>, 10{sup 7}-10{sup 8} s{sup -1}. Solid-state strength is inferred using the Rayleigh-Taylor instability as a ''diagnostic''. Temperature and compression in polycrystalline samples can be deduced from EXAFS measurements. Lattice response can be inferred from time-resolved x-ray diffraction. Deformation mechanisms can be identified by examining recovered samples. We will briefly review this new area of laser-based materials science research, then present a path forward for carrying these solid-state experiments to much higher pressures, P >> 1 Mbar, on the NIF laser facility.</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>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> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26750682','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26750682"><span><span class="hlt">Strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span>: An emerging technology in the perioperative period.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Malik, Vishwas; Subramaniam, Arun; Kapoor, Poonam Malhotra</p> <p>2016-01-01</p> <p>Newer noninvasive parameters are being used for perioperative detection of myocardial ischaemia. TDI and global <span class="hlt">strain</span> <span class="hlt">rate</span> are some of these parameters. TDI signal is a modification of the routine Doppler flow signal. It is obtained by using thresholding and filtering algorithms that reject echoes originating from the blood pool (by-passing the high pass filter). Set-Up of the machine by activating the TDI function allows decreasing the system gain using a low pass filter and eliminates the signal produced by blood flow. Doppler shift obtained from myocardial tissue motion are of higher amplitudes (reflectivity 40 dB higher) and move about 10 times slower than blood (velocity range: 0.06 to 0.24 m/s). Speckle tracking echocardiography (tissue tracking, 2D <span class="hlt">strain</span>) utilizes routine gray-scale 2D echo images to calculate myocardial <span class="hlt">strain</span>. Interactions of ultrasound with myocardium result in reflection and scattering. These interactions generate a finely gray-shaded, speckled pattern (acoustic marker). This speckled pattern is unique for each myocardial region and relatively stable throughout the cardiac cycle. Spatial and temporal image processing of acoustic speckles in both 2D and 3D allows for the calculation of myocardial velocity, <span class="hlt">strain</span>, and <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/AD1003589','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1003589"><span>Soft Tissue <span class="hlt">Strain</span> <span class="hlt">Rates</span> in Side-Blast Incidents</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>2014-11-02</p> <p>light armour vehicles (LAV). The establishment of meaningful injury criteria is, however, a challenging task that is still under extensive studies...improve models’ representativeness. This paper introduces a simplified finite element model of a human neck to study the reaction of armour vehicle...crashes or falls. Therefore, there is no consensus on what <span class="hlt">strain</span> <span class="hlt">rate</span> should be used to elaborate accurate human body models under various impact</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/15005361','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/15005361"><span>Materials Science 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; Bazan, G; Bringa, E; Caturla, M; Edwards, M J; Glendinning, S G; Kad, B; Kalantar, D H; Kumar, M; Lasinski, B F; Lorenz, K T; McNaney, J; Meyerhofer, D; Meyers, M A; Pollaine, S M; Reisman, D B; Rowley, D; Schneider, M; Stolken, J; Wark, J; Yaakobi, B</p> <p>2003-03-27</p> <p>Solid state dynamics experiments at very high pressures (P >> 10 GPa) and <span class="hlt">strain</span> <span class="hlt">rates</span> ({var_epsilon} >> 10{sup 5} s{sup -1}) have been demonstrated on high energy laser facilities, albeit over brief intervals of time and small spatial scales. We have developed two methods for driving samples to high pressures (10-100 GPa) at high <span class="hlt">strain</span> <span class="hlt">rate</span> (10{sup 6}-10{sup 8} s{sup -1}) in the solid state. One method uses a shockless compression technique, and the other uses multiple staged shocks. These drives are calibrated with VISAR measurements of the resulting compression wave. Deformation mechanisms are inferred under these conditions by characterizing recovered samples. Material strength at high pressures and <span class="hlt">strain</span> <span class="hlt">rates</span> is deduced by measuring the reduced growth of material perturbations at a hydrodynamically unstable interface. Microscopic lattice response is determined by time-resolved Bragg diffraction and x-ray absorption spectroscopy (EXAFS). Large-scale simulations, both at the continuum level using constitutive models and at the lattice level using molecular dynamics simulation, are used to interpret these integral experiments. We will review our progress in this new area of laser-based materials science research, then present a vision for carrying these solid-state experiments to much higher pressures, P > 1000 GPa, on the National Ignition Facility (NIF) laser facility.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1857d0006S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1857d0006S"><span>Rotation and <span class="hlt">strain</span> <span class="hlt">rate</span> of Sulawesi from geometrical velocity field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sarsito, D. A.; Susilo, Simons, W. J. F.; Abidin, H. Z.; Sapiie, B.; Triyoso, W.; Andreas, H.</p> <p>2017-07-01</p> <p>One of methods that can be used to determine the tectonic deformation status is <span class="hlt">rate</span> estimation from geometric rotation and <span class="hlt">strain</span> using quantitative velocity data from GPS observations. Microplate Sulawesi region located in the zone of triple junction (Eurasia, Australia and Philippine Sea Plates) has very complex tectonic and seismic condition, which is why become very important to know its recent deformation status in order to study neo-tectonic and disaster mitigation. Deformation <span class="hlt">rate</span> quantification is estimated in two parameters: rotation and geodetic <span class="hlt">strain</span> <span class="hlt">rate</span> of each GPS station Delaunay triangle in the study area. The analysis in this study is not done using the grids since there is no rheological information at location that can be used as the interpolation-extrapolation constraints. Our analysis reveals that Sulawesi is characterized by rapid rotation in several different domains and compression-<span class="hlt">strain</span> pattern that varies depending on the type and boundary conditions of microplate. This information is useful for studying neo tectonic deformation status and earthquake disaster mitigation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24795295','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24795295"><span><span class="hlt">Effects</span> of feeder space allocations during rearing, female <span class="hlt">strain</span>, and feed increase <span class="hlt">rate</span> from photostimulation to peak egg production on broiler breeder female performance.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Leksrisompong, N; Romero-Sanchez, H; Oviedo-Rondón, E O; Brake, J</p> <p>2014-05-01</p> <p>A study was conducted to determine if there were differences in female broiler breeder performance of 2 <span class="hlt">strains</span> that had been subjected to 2 feeder space allocations during the growing period followed by 2 feeding to peak programs. Ross 308 and 708 pullets were reared with a single feeding program to 23 wk of age and with 2 circumferential feeder space allocations (5.3 cm/female or 7.0 cm/female) and then assigned to 2 feed increase programs (slow or fast) from photostimulation to peak egg production. The flock was moved to the laying house with 8.8 cm/female of female feeder space and photostimulated at 23 wk of age when Ross 344 males were added to create 16 pens with 60 females and 7 males each in a 2 × 2 × 2 design. The fast feed increase program significantly increased female BW at 31 wk of age, which could have contributed to an increased female mortality during the summer weather of early lay. The 708 females with 5.3 cm/female feeder space produced smaller eggs at 28 and 30 wk of age. The 708 females exhibited better fertile hatchability than 308 females due to fewer late dead embryos. There were no differences in egg production, fertility, or fertile hatchability due to the main <span class="hlt">effects</span> of feeding to peak program or growing feeder space, but the slow feed increase from photostimulation to peak production reduced cumulative mortality.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhRvL.119k8004V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvL.119k8004V"><span>Evidence That <span class="hlt">Strain-Rate</span> Softening Is Not Necessary for Material Instability Patterns</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Valdes, Julio R.; Guillard, François; Einav, Itai</p> <p>2017-09-01</p> <p><span class="hlt">Strain-rate</span> softening has been associated with a wide variety of material instabilities, from the Portevin-Le Chatelier <span class="hlt">effect</span> in metal alloys to stick-slip motion in crust faults. Dynamic instability patterns have been recently discovered in brittle porous media: diffused, oscillatory, and erratic compaction. Using model simulations inspired by experiments with puffed rice, we question the link between these dynamic patterns and <span class="hlt">strain-rate</span> sensitivity in such media. An important feature of our model is that it can recover <span class="hlt">strain-rate</span> softening as an emergent phenomenon, without imposing it a priori at its microstructural scale. More importantly, the model also demonstrates that the full range of dynamic patterns can develop without presenting macroscopic <span class="hlt">strain-rate</span> softening. Based on this counterexample model, we therefore argue that <span class="hlt">strain-rate</span> softening should not be taken as a necessary condition for the emergence of instability patterns. Our findings in brittle porous media have implications on models that require <span class="hlt">strain-rate</span> softening to explain earthquake and metal alloy instabilities.</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><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/2010EPJWC...639002G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EPJWC...639002G"><span>A New Compression Intermediate <span class="hlt">Strain</span> <span class="hlt">Rate</span> Testing Apparatus</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gilat, A.; Matrka, T. A.</p> <p>2010-06-01</p> <p>A new apparatus for testing in compression at intermediate <span class="hlt">strain</span> <span class="hlt">rates</span> is introduced. The apparatus consists of a loading hydraulic actuator and a very long (40 m) transmitter bar. The specimen is placed with one end touching the end surface of the long bar and the other end free. The specimen is loaded by the actuator that impacts the specimen’s free end directly. Once loaded, the specimen deforms between the actuator and the transmitter bar. As the specimen is loaded and deformed, a compression wave propagates into the transmitter bar. The amplitude of this wave is measured with <span class="hlt">strain</span> gages that are placed on the transmitter bar at a distance of about five diameters from the specimen. The wave in the transmitter bar propagates all the way to the end of the bar and then reflects back toward the specimen. The experiment can continue until the reflected wave reaches the <span class="hlt">strain</span> gages (milliseconds). The <span class="hlt">strain</span> in the specimen (full field) is measured directly on the specimen using Digital Image Correlation with high speed cameras.</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://adsabs.harvard.edu/abs/2016ApPhA.122..897Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApPhA.122..897Z"><span>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('http://adsabs.harvard.edu/abs/2017RSPTA.37560174R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017RSPTA.37560174R"><span>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('https://www.ncbi.nlm.nih.gov/pubmed/27956510','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27956510"><span>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://www.osti.gov/scitech/servlets/purl/10104863','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/10104863"><span>Evolution of plastic anisotropy for high-<span class="hlt">strain-rate</span> computations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Schiferl, S.K.; Maudlin, P.J.</p> <p>1994-12-01</p> <p>A model for anisotropic material strength, and for changes in the anisotropy due to plastic <span class="hlt">strain</span>, is described. This model has been developed for use in high-<span class="hlt">rate</span>, explicit, Lagrangian multidimensional continuum-mechanics codes. The model handles anisotropies in single-phase materials, in particular the anisotropies due to crystallographic texture--preferred orientations of the single-crystal grains. Textural anisotropies, and the changes in these anisotropies, depend overwhelmingly no the crystal structure of the material and on the deformation history. The changes, particularly for a complex deformations, are not amenable to simple analytical forms. To handle this problem, the material model described here includes a texture code, or micromechanical calculation, coupled to a continuum code. The texture code updates grain orientations as a function of tensor plastic <span class="hlt">strain</span>, and calculates the yield strength in different directions. A yield function is fitted to these yield points. For each computational cell in the continuum simulation, the texture code tracks a particular set of grain orientations. The orientations will change due to the tensor <span class="hlt">strain</span> history, and the yield function will change accordingly. Hence, the continuum code supplies a tensor <span class="hlt">strain</span> to the texture code, and the texture code supplies an updated yield function to the continuum code. Since significant texture changes require relatively large <span class="hlt">strains</span>--typically, a few percent or more--the texture code is not called very often, and the increase in computer time is not excessive. The model was implemented, using a finite-element continuum code and a texture code specialized for hexagonal-close-packed crystal structures. The results for several uniaxial stress problems and an explosive-forming problem are shown.</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>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://adsabs.harvard.edu/abs/2016EPJST.225..283C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EPJST.225..283C"><span>Compressive behaviour of dam concrete at higher <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>Caverzan, A.; Peroni, M.; Solomos, G.</p> <p>2016-05-01</p> <p>The mechanical behaviour of concrete when subjected to impact or blast has still many aspects requiring further study. Dam concrete is characterized by large coarse aggregates, hence large specimen sizes are needed in order to study a representative volume of the material. Exploiting an innovative equipment, based on Hopkinson bar techniques, the dynamic behaviour of concrete of 64 mm maximum aggregate size has been investigated. Direct dynamic compression tests have been performed on medium and large size cylindrical samples. Full stress-<span class="hlt">strain</span> curves have been obtained, which have allowed the estimation of fracturing energies and of the relevant dynamic increase factor. The experimental campaign has also included a reference standard concrete in order to highlight the peculiarity of the dam concrete at high <span class="hlt">strain</span> <span class="hlt">rates</span> and to validate the transition of this type of testing to very large specimens.</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>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>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://www.osti.gov/scitech/servlets/purl/244530','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/244530"><span>Premixed flame response to unsteady <span class="hlt">strain-rate</span> and curvature</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Najm, H.N.; Wyckoff, P.S.</p> <p>1996-05-01</p> <p>The interaction of a premixed stoichiometric methane-air flame with a counter-rotating vortex-pair is studied using a skeletal C{sub 1} chemical description of the reaction process. The focus is on the modification to flame structure and dynamics due to unsteady <span class="hlt">strain-rate</span> and curvature. The detailed description of flame structure and dynamics in response to unsteady flow is necessary to establish relevant extinction criteria in unsteady multi-dimensional flow, which, based on recent experimental evidence, may be significantly different from those of steady one-dimensional counterflow stagnation flames. Present results suggest that the increasing unsteady tangential <span class="hlt">strain-rate</span> causes modification of flame structure that leads to reduced reaction <span class="hlt">rates</span> of key chain-branching reactions which are active on the products side of the flame. This causes a reduction in the concentrations of active radicals, such as H, OH, and O, which are necessary for the breakdown of hydrocarbons on the reactants side of the flame.</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>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. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.</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>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><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://www.osti.gov/scitech/servlets/purl/903272','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/903272"><span>STATUS OF IN-REACTOR TENSILE <span class="hlt">STRAINING</span> OF PURE COPPER AT A CONSTANT <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>Edwards, Danny J.; Singh, Bachu N.; Tahtinen, S.; Moilanen, P.; Jacquet, P.; Dekeyser, J.</p> <p>2003-09-03</p> <p>Annealed tensile samples of pure copper were irradiated in the fission reactor BR-2 in Mol, Belgium at 90 degrees C with a damage <span class="hlt">rate</span> of 0.00000006 dpa/sec. The tensile specimens were a sheet-type specimen with a 3-mm gage width and a gage length of 7 mm. The first experiment involved two specimens, one of which was irradiated with no load to provide a comparative specimen to the other specimen, which was loaded at a constant <span class="hlt">strain</span> <span class="hlt">rate</span> of 0.00000013 1/s. The uniaxial tensile load was applied 4 hrs after the irradiation rig was inserted into the reactor core. This corresponded to a total displacement damage of 0.00086 dpa accumulated before the tensile test was started. The tensile test was considered complete once the load began rapidly falling and reached 100 MPa, at which level the test was stopped and the load quickly reduced to zero to leave the specimen intact. For these test conditions the specimen reached a total plastic <span class="hlt">strain</span> of approximately 13 percent when the test was stopped, considerably less than that of unirradiated pure copper tested under the same <span class="hlt">strain</span> <span class="hlt">rate</span>, which was on the order of 50 percent total elongation. The second experiment involved two samples irradiated under identical irradiation and test conditions, but in this case the tensile load was not applied until a total dose of 0.01 dpa (approximately 50 hours after insertion into the reactor core) was reached. Once the load was applied, the stress immediately climbed to approximately 150 MPa with little plastic <span class="hlt">strain</span>, followed by a small yield drop and work hardening up to a maximum stress of approximately 200 MPa. As in the first experiment, the tensile test was stopped when the load began decreasing and reached a level of 100 MPa.</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>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('https://www.ncbi.nlm.nih.gov/pubmed/20143127','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20143127"><span>Mortality <span class="hlt">rates</span> differ among amphibian populations exposed to three <span class="hlt">strains</span> of a lethal ranavirus.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schock, Danna M; Bollinger, Trent K; Collins, James P</p> <p>2009-09-01</p> <p>Infectious diseases are a growing threat to biodiversity, in many cases because of synergistic <span class="hlt">effects</span> with habitat loss, environmental contamination, and climate change. Emergence of pathogens as new threats to host populations can also arise when novel combinations of hosts and pathogens are unintentionally brought together, for example, via commercial trade or wildlife relocations and reintroductions. Chytrid fungus (Batrachochytrium dendrobatidis) and amphibian ranaviruses (family Iridoviridae) are pathogens implicated in global amphibian declines. The emergence of disease associated with these pathogens appears to be at least partly related to recent translocations over large geographic distances. We experimentally examined the outcomes of novel combinations of host populations and pathogen <span class="hlt">strains</span> using the amphibian ranavirus Ambystoma tigrinum virus (ATV) and barred tiger salamanders (Ambystoma mavortium, formerly considered part of the Ambystoma tigrinum complex). One salamander population was highly resistant to lethal infections by all ATV <span class="hlt">strains</span>, including its own <span class="hlt">strain</span>, and mortality <span class="hlt">rates</span> differed among ATV <span class="hlt">strains</span> according to salamander population. Mortality <span class="hlt">rates</span> in novel pairings of salamander population and ATV <span class="hlt">strain</span> were not predictable based on knowledge of mortality <span class="hlt">rates</span> when salamander populations were exposed to their own ATV <span class="hlt">strain</span>. The underlying cause(s) for the differences in mortality <span class="hlt">rates</span> are unknown, but local selection pressures on salamanders, viruses, or both, across the range of this widespread host-pathogen system are a plausible hypothesis. Our study highlights the need to minimize translocations of amphibian ranaviruses, even among conspecifc host populations, and the importance of considering intraspecific variation in endeavors to manage wildlife diseases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5102476','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5102476"><span>Atrial <span class="hlt">Strain</span> and <span class="hlt">Strain</span> <span class="hlt">Rate</span>: A Novel Method for the Evaluation of Atrial Stunning</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ozkan, Hakan; Binici, Suleyman; Tenekecioglu, Erhan; Ari, Hasan; Bozat, Tahsin</p> <p>2016-01-01</p> <p>Background Atrial fibrillation (AF) is the most common arrhythmia seen in adults. Atrial stunning is defined as the temporary mechanical dysfunction of the atrial appendage developing after AF has returned to sinus rhythm (SR). Objectives We aimed to evaluate atrial contractile functions by <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> in patients with AF, following pharmacological and electrical cardioversion and to compare it with conventional methods. Methods This study included 41 patients with persistent AF and 35 age-matched control cases with SR. All the AF patients included in the study had transthoracic and transesophageal echocardiography performed before and after. Septum (SEPsSR), left atrium (LAsSR) and right atrium peak systolic <span class="hlt">strain</span> <span class="hlt">rate</span> (RAsSR) were defined as the maximum negative value during atrial contraction and septum (SEPε), left atrium (LAε) and right atrium peak systolic <span class="hlt">strain</span> (RAε) was defined as the percentage of change. Parameters of two groups were compared. Results In the AF group, 1st hour and 24th hour LAε, RAε, SEPε, LAsSR, RAsSR, SEPsSR found to be significantly lower than in the control group (LAε: 2.61%±0.13, 3.06%±0.19 vs 6.45%±0.27, p<0.0001; RAε: 4.03%±0.38, 4.50%±0.47 vs 10.12%±0.64, p<0.0001; SEPε: 3.0%±0.22, 3.19%±0.15 vs 6.23%±0.49, p<0.0001; LAsSR: 0.61±0.04s-1, 0.75±0.04s-1 vs 1.35±0.04s-1, p<0.0001; RAsSR: 1.13±0.06s-1, 1.23±0.07s-1 vs 2.10±0.08s- 1, p<0.0001; SEPsSR: 0.76±0.04s- 1, 0.78±0.04s- 1 vs 1.42±0.06 s- 1, p<0.0001). Conclusion Atrial <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> parameters are superior to conventional echocardiographic parameters for the evaluation of atrial stunning in AF cases where SR has been achieved. PMID:27627221</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27627221','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27627221"><span>Atrial <span class="hlt">Strain</span> and <span class="hlt">Strain</span> <span class="hlt">Rate</span>: A Novel Method for the Evaluation of Atrial Stunning.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ozkan, Hakan; Binici, Suleyman; Tenekecioglu, Erhan; Ari, Hasan; Bozat, Tahsin</p> <p>2016-10-01</p> <p>Atrial fibrillation (AF) is the most common arrhythmia seen in adults. Atrial stunning is defined as the temporary mechanical dysfunction of the atrial appendage developing after AF has returned to sinus rhythm (SR). We aimed to evaluate atrial contractile functions by <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> in patients with AF, following pharmacological and electrical cardioversion and to compare it with conventional methods. This study included 41 patients with persistent AF and 35 age-matched control cases with SR. All the AF patients included in the study had transthoracic and transesophageal echocardiography performed before and after. Septum (SEPsSR), left atrium (LAsSR) and right atrium peak systolic <span class="hlt">strain</span> <span class="hlt">rate</span> (RAsSR) were defined as the maximum negative value during atrial contraction and septum (SEPε), left atrium (LAε) and right atrium peak systolic <span class="hlt">strain</span> (RAε) was defined as the percentage of change. Parameters of two groups were compared. In the AF group, 1st hour and 24th hour LAε, RAε, SEPε, LAsSR, RAsSR, SEPsSR found to be significantly lower than in the control group (LAε: 2.61%±0.13, 3.06%±0.19 vs 6.45%±0.27, p<0.0001; RAε: 4.03%±0.38, 4.50%±0.47 vs 10.12%±0.64, p<0.0001; SEPε: 3.0%±0.22, 3.19%±0.15 vs 6.23%±0.49, p<0.0001; LAsSR: 0.61±0.04s-1, 0.75±0.04s- 1 vs 1.35±0.04s-1, p<0.0001; RAsSR: 1.13±0.06s-1, 1.23±0.07s-1 vs 2.10±0.08s- 1, p<0.0001; SEPsSR: 0.76±0.04s- 1, 0.78±0.04s- 1 vs 1.42±0.06 s- 1, p<0.0001). Atrial <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> parameters are superior to conventional echocardiographic parameters for the evaluation of atrial stunning in AF cases where SR has been achieved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19970020562&hterms=diffusion+rate&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Ddiffusion%2Brate','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19970020562&hterms=diffusion+rate&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Ddiffusion%2Brate"><span><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('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><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://adsabs.harvard.edu/abs/2013EGUGA..15.7786R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.7786R"><span><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> </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('https://www.ncbi.nlm.nih.gov/pubmed/19412170','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19412170"><span>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/791440','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/791440"><span>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('http://adsabs.harvard.edu/abs/2017MMTA...48..126Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MMTA...48..126Z"><span>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> <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>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/2015EPJWC..9401019L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9401019L"><span>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><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://www.osti.gov/scitech/servlets/purl/46570','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/46570"><span>Influence of <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature on the mechanical behavior of iron aluminide-based alloys</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gray, G.T.</p> <p>1995-04-01</p> <p>Iron aluminides are receiving increasing attention as potential high temperature structural materials due to their excellent oxidation and sulfidation resistance. Although the influence of <span class="hlt">strain</span> <span class="hlt">rate</span> on the microstructure/property relationships of pure iron and a variety of iron alloys and steels 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 iron aluminides remains poorly understood. In this paper the influence of <span class="hlt">strain</span> <span class="hlt">rate</span>, varied between 0.001 and 10{sup 4} s{sup {minus}1}, and temperature, between 77 & 1073{degree}K, on the mechanical behavior of Fe-40Al-0.1B and Fe-16.12Al-5.44Cr-0.11Zr-0.13C-1.07Mo-006Y, called FAP-Y, (both in at.%) is presented. The <span class="hlt">rate</span> sensitivity and work hardening of Fe-40Al and the disordered alloy based on Fe-16% Al are discussed as a function of <span class="hlt">strain</span> <span class="hlt">rate</span> and temperature.</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>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('http://adsabs.harvard.edu/abs/2014JMPSo..63..113N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JMPSo..63..113N"><span>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/18786670','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18786670"><span>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/25041719','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25041719"><span>Theoretical elucidation of the origins of substituent and <span class="hlt">strain</span> <span class="hlt">effects</span> on the <span class="hlt">rates</span> of Diels-Alder reactions of 1,2,4,5-tetrazines.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liu, Fang; Liang, Yong; Houk, K N</p> <p>2014-08-13</p> <p>The Diels-Alder reactions of seven 1,2,4,5-tetrazines with unstrained and <span class="hlt">strained</span> alkenes and alkynes were studied with quantum mechanical calculations (M06-2X density functional theory) and analyzed with the distortion/interaction model. The higher reactivities of alkenes compared to alkynes in the Diels-Alder reactions with tetrazines arise from the differences in both interaction and distortion energies. Alkenes have HOMO energies higher than those of alkynes and therefore stronger interaction energies in inverse-electron-demand Diels-Alder reactions with tetrazines. We have also found that the energies to distort alkenes into the Diels-Alder transition-state geometries are smaller than for alkynes in these reactions. The <span class="hlt">strained</span> dienophiles, trans-cyclooctene and cyclooctyne, are much more reactive than unstrained trans-2-butene and 2-butyne, because they are predistorted toward the Diels-Alder transition structures. The reactivities of substituted tetrazines correlate with the electron-withdrawing abilities of the substituents. Electron-withdrawing groups lower the LUMO+1 of tetrazines, resulting in stronger interactions with the HOMO of dienophiles. Moreover, electron-withdrawing substituents destabilize the tetrazines, and this leads to smaller distortion energies in the Diels-Alder transition states.</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><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><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('http://adsabs.harvard.edu/abs/2006JPhy4.134..325R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006JPhy4.134..325R"><span>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('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><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('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><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><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://ntrs.nasa.gov/search.jsp?R=20040141548&hterms=greenberg&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dgreenberg','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040141548&hterms=greenberg&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dgreenberg"><span>Potential pitfalls of <span class="hlt">strain</span> <span class="hlt">rate</span> imaging: angle dependency</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Castro, P. L.; Greenberg, N. L.; Drinko, J.; Garcia, M. J.; Thomas, J. D.</p> <p>2000-01-01</p> <p><span class="hlt">Strain</span> <span class="hlt">Rate</span> Imaging (SRI) is a new echocardiographic technique that allows for the real-time determination of myocardial SR, which may be used for the early and accurate detection of coronary artery disease. We sought to study whether SR is affected by scan line alignment in a computer simulation and an in vivo experiment. Through the computer simulation and the in vivo experiment we generated and validated safe scanning sectors within the ultrasound scan sector and showed that while SRI will be an extremely valuable tool in detecting coronary artery disease there are potential pitfalls for the unwary clinician. Only after accounting for these affects due to angle dependency, can clinicians utilize SRI's potential as a valuable tool in detecting coronary artery disease.</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>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>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> </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('https://www.ncbi.nlm.nih.gov/pubmed/26291674','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26291674"><span><span class="hlt">Strain-rate</span>-dependent non-linear tensile properties of the superficial zone of articular cartilage.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ahsanizadeh, Sahand; Li, LePing</p> <p>2015-11-01</p> <p>The tensile properties of articular cartilage play an important role in the compressive behavior and integrity of the tissue. The stress-<span class="hlt">strain</span> relationship of cartilage in compression was observed previously to depend on the <span class="hlt">strain-rate</span>. This <span class="hlt">strain-rate</span> dependence has been thought to originate mainly from fluid pressurization. However, it was not clear to what extent the tensile properties of cartilage contribute to the <span class="hlt">strain-rate</span> dependence in compressive behavior of cartilage. The aim of the present study was to quantify the <span class="hlt">strain-rate</span> dependent stress-<span class="hlt">strain</span> relationship and hysteresis of articular cartilage in tension. Uniaxial tensile tests were performed to examine the <span class="hlt">strain-rate</span> dependent non-linear tensile properties of the superficial zone of bovine knee cartilage. Tensile specimens were oriented in the fiber direction indicated by the India ink method. Seven <span class="hlt">strain-rates</span> were used in the measurement ranging from 0.1 to 80%/s, which corresponded to nearly static to impact joint loadings. The experimental data showed substantial <span class="hlt">strain-rate</span> and <span class="hlt">strain</span>-magnitude dependent load response: for a given <span class="hlt">strain</span>-magnitude, the tensile stress could vary by a factor of 1.95 while the modulus by a factor of 1.58 with <span class="hlt">strain-rate</span>; for a given <span class="hlt">strain-rate</span>, the modulus at 15% <span class="hlt">strain</span> could be over four times the initial modulus at no <span class="hlt">strain</span>. The energy loss in cartilage tension upon unloading exhibited a complex variation with the <span class="hlt">strain-rate</span>. The <span class="hlt">strain-rate</span> dependence of cartilage in tension observed from the present study is relatively weaker than that in compression observed previously, but is considerable to contribute to the <span class="hlt">strain-rate</span> dependent load response in compression.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014Nanos...614863M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014Nanos...614863M"><span><span class="hlt">Strain-rate</span> stiffening of cortical bone: observations and implications from nanoindentation experiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maruyama, Noriko; Shibata, Yo; Wurihan, Affb; Swain, Michael V.; Kataoka, Yu; Takiguchi, Yuichi; Yamada, Atsushi; Maki, Koutaro; Miyazaki, Takashi</p> <p>2014-11-01</p> <p>While bone mineralization is considered to be responsible for its stiffness, bone durability partially associated with the time-dependent viscoelasticity of matrix proteins is still poorly elucidated. Here we demonstrate a novel mechanism of highly mineralized bone durability almost independent of inherent viscoelastic behaviour along with a protocol for measuring the mechanical properties of mineralized tissues. <span class="hlt">Strain-rate</span> nanoindentation tests showed substantial stiffening of the highly mineralized calvarial bone, whereas large creep or stress relaxation was observed during constant load or displacement tests, respectively. Based on the lower viscoelasticity of the highly mineralized structure, such large time-dependent response appears to be associated with nanoscale dimensional recovery, rather than viscoelastic behaviour, implying the inverse namely <span class="hlt">strain-rate</span> dependent dilatant behaviour. This dilatant expansion increased the indenter penetration resistance into the surface, enhancing instantaneous stiffness. The associated stiffening and higher <span class="hlt">effective</span> elastic modulus were highly <span class="hlt">strain-rate</span> dependent and more readily observed in more highly mineralized tissues such as the calvarial bone. Such <span class="hlt">strain-rate</span> stiffening and consequent dimensional recovery may be vital responses of bone tissues against excessive deformation to maintain tissue integrity.While bone mineralization is considered to be responsible for its stiffness, bone durability partially associated with the time-dependent viscoelasticity of matrix proteins is still poorly elucidated. Here we demonstrate a novel mechanism of highly mineralized bone durability almost independent of inherent viscoelastic behaviour along with a protocol for measuring the mechanical properties of mineralized tissues. <span class="hlt">Strain-rate</span> nanoindentation tests showed substantial stiffening of the highly mineralized calvarial bone, whereas large creep or stress relaxation was observed during constant load or displacement</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26093345','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26093345"><span>Microscale consolidation analysis of relaxation behavior of single living chondrocytes subjected to varying <span class="hlt">strain-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>Nguyen, Trung Dung; Oloyede, Adekunle; Singh, Sanjleena; Gu, YuanTong</p> <p>2015-09-01</p> <p>Besides the elastic stiffness, the relaxation behavior of single living cells is also of interest of various researchers when studying cell mechanics. It is hypothesized that the relaxation response of the cells is governed by both intrinsic viscoelasticity of the solid phase and fluid-solid interactions mechanisms. There are a number of mechanical models have been developed to investigate the relaxation behavior of single cells. However, there is lack of model enable to accurately capture both of the mechanisms. Therefore, in this study, the porohyperelastic (PHE) model, which is an extension of the consolidation theory, combined with inverse Finite Element Analysis (FEA) technique was used at the first time to investigate the relaxation response of living chondrocytes. This model was also utilized to study the dependence of relaxation behavior of the cells on <span class="hlt">strain-rates</span>. The stress-relaxation experiments under the various <span class="hlt">strain-rates</span> were conducted with the Atomic Force Microscopy (AFM). The results have demonstrated that the PHE model could <span class="hlt">effectively</span> capture the stress-relaxation behavior of the living chondrocytes, especially at intermediate to high <span class="hlt">strain-rates</span>. Although this model gave some errors at lower <span class="hlt">strain-rates</span>, its performance was acceptable. Therefore, the PHE model is properly a promising model for single cell mechanics studies. Moreover, it has been found that the hydraulic permeability of living chondrocytes reduced with decreasing of <span class="hlt">strain-rates</span>. It might be due to the intracellular fluid volume fraction and the fluid pore pressure gradients of chondrocytes were higher when higher <span class="hlt">strain-rates</span> applied. Copyright © 2015 Elsevier Ltd. All rights reserved.</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><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('http://adsabs.harvard.edu/abs/2016JPhCS.734c2140V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.734c2140V"><span><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>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/2015RuMet2015..840T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015RuMet2015..840T"><span>Influence of the tensile <span class="hlt">strain</span> <span class="hlt">rate</span> on the mechanical properties and phase composition of VNS 9-Sh TRIP steel</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Terent'ev, V. F.; Slizov, A. K.; Prosvirnin, D. V.; Sirotinkin, V. P.; Ashmarin, A. A.; Gol'dberg, M. A.</p> <p>2015-10-01</p> <p>The influence of the <span class="hlt">strain</span> <span class="hlt">rate</span> on the mechanical properties and the phase composition of a sheet VNS 9-Sh (23Kh15N5AM3-Sh) TRIP steel is studied during static tension. The <span class="hlt">strain</span> <span class="hlt">rate</span> is changed in the range from 8.3 × 10-5 to 25 × 10-3 s-1. The dependence of the mechanical properties on the <span class="hlt">strain</span> <span class="hlt">rate</span> is found to be nonlinear. The TRIP <span class="hlt">effect</span> is most pronounced at a <span class="hlt">strain</span> <span class="hlt">rate</span> of (8.3-17) × 10-5 s-1. In this <span class="hlt">strain</span> <span class="hlt">rate</span>, the deformation martensite content increases significantly, from 50 to 87%, as is detected by X-ray diffraction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..SHK.M1067K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..SHK.M1067K"><span>Comparison of epoxy-based encapsulating materials over temperature and <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>Khan, Amnah; Proud, William</p> <p>2015-06-01</p> <p>The <span class="hlt">effects</span> of varying <span class="hlt">strain</span> <span class="hlt">rates</span> and temperatures on the compressive response of an epoxy resin with and without alumina filler have been investigated. The samples are studied in the range of temperatures from - 20° C to + 80° C over a range of <span class="hlt">strain</span> <span class="hlt">rates</span> (10-4 s-1 to 10+3 s-1). Three loading devices were used to access this range: an Instron, drop weight and a Split Hopkinson Pressure Bar. Stress-<span class="hlt">strain</span> data was obtained, along with high-speed images. The response of the materials is compared and discussed in relation to their use as encapsulants of piezoelectric systems. The Institute of Shock Physics acknowledges the support of AWE, Aldermaston, UK and Imperial College London.</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>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://adsabs.harvard.edu/abs/2012EPJST.206....3E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EPJST.206....3E"><span><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/2013AGUFM.S13C..03B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.S13C..03B"><span>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/2015EPJWC..9401047Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EPJWC..9401047Y"><span>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>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/2006MTDM...10...83L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006MTDM...10...83L"><span>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>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>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.osti.gov/scitech/biblio/7045489','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/7045489"><span>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>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('https://www.ncbi.nlm.nih.gov/pubmed/7270427','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/7270427"><span><span class="hlt">Effective</span> heat <span class="hlt">strain</span> index using pocket computer.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kamon, E; Ryan, C</p> <p>1981-08-01</p> <p>An <span class="hlt">effective</span> heat <span class="hlt">strain</span> index (EHSI) using a hand calculator with memory is suggested for on-site evaluation of prevailing hot ambient conditions. The inputs to the programmed calculator include dry-bulb, wet-bulb and globe temperatures, and estimates of metabolism and air movements. The index is based on a program for calculation of the total heat balance and on the efficiency of sweating. The display of information on the ambient conditions EHSI display is one of following: no <span class="hlt">strain</span>; low <span class="hlt">strain</span>; high <span class="hlt">strain</span>; or time limits of exposure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1398378-strain-rate-dependence-ramp-wave-evolution-strength-tantalum','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1398378-strain-rate-dependence-ramp-wave-evolution-strength-tantalum"><span><span class="hlt">Strain-rate</span> dependence of ramp-wave evolution and strength in tantalum</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Lane, J. Matthew D.; Foiles, Stephen M.; Lim, Hojun; ...</p> <p>2016-08-25</p> <p>We have conducted molecular dynamics (MD) simulations of quasi-isentropic ramp-wave compression to very high pressures over a range of <span class="hlt">strain</span> <span class="hlt">rates</span> from 1011 down to 108 1/s. Using scaling methods, we collapse wave profiles from various <span class="hlt">strain</span> <span class="hlt">rates</span> to a master profile curve, which shows deviations when material response is <span class="hlt">strain-rate</span> dependent. Thus, we can show with precision where, and how, <span class="hlt">strain-rate</span> dependence affects the ramp wave. We find that <span class="hlt">strain</span> <span class="hlt">rate</span> affects the stress-<span class="hlt">strain</span> material response most dramatically at <span class="hlt">strains</span> below 20%, and that above 30% <span class="hlt">strain</span> the material response is largely independent of <span class="hlt">strain</span> <span class="hlt">rate</span>. We show goodmore » overall agreement with experimental stress-<span class="hlt">strain</span> curves up to approximately 30% <span class="hlt">strain</span>, above which simulated response is somewhat too stiff. We postulate that this could be due to our interatomic potential or to differences in grain structure and/or size between simulation and experiment. Strength is directly measured from per-atom stress tensor and shows significantly enhanced elastic response at the highest <span class="hlt">strain</span> <span class="hlt">rates</span>. As a result, this enhanced elastic response is less pronounced at higher pressures and at lower <span class="hlt">strain</span> <span class="hlt">rates</span>.« less</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://www.osti.gov/scitech/servlets/purl/1398378','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1398378"><span><span class="hlt">Strain-rate</span> dependence of ramp-wave evolution and strength in tantalum</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lane, J. Matthew D.; Foiles, Stephen M.; Lim, Hojun; Brown, Justin L.</p> <p>2016-08-25</p> <p>We have conducted molecular dynamics (MD) simulations of quasi-isentropic ramp-wave compression to very high pressures over a range of <span class="hlt">strain</span> <span class="hlt">rates</span> from 10<sup>11</sup> down to 10<sup>8</sup> 1/s. Using scaling methods, we collapse wave profiles from various <span class="hlt">strain</span> <span class="hlt">rates</span> to a master profile curve, which shows deviations when material response is <span class="hlt">strain-rate</span> dependent. Thus, we can show with precision where, and how, <span class="hlt">strain-rate</span> dependence affects the ramp wave. We find that <span class="hlt">strain</span> <span class="hlt">rate</span> affects the stress-<span class="hlt">strain</span> material response most dramatically at <span class="hlt">strains</span> below 20%, and that above 30% <span class="hlt">strain</span> the material response is largely independent of <span class="hlt">strain</span> <span class="hlt">rate</span>. We show good overall agreement with experimental stress-<span class="hlt">strain</span> curves up to approximately 30% <span class="hlt">strain</span>, above which simulated response is somewhat too stiff. We postulate that this could be due to our interatomic potential or to differences in grain structure and/or size between simulation and experiment. Strength is directly measured from per-atom stress tensor and shows significantly enhanced elastic response at the highest <span class="hlt">strain</span> <span class="hlt">rates</span>. As a result, this enhanced elastic response is less pronounced at higher pressures and at lower <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/21903290','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21903290"><span><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://www.osti.gov/scitech/servlets/purl/875626','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/875626"><span>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('http://hdl.handle.net/2060/20100002839','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100002839"><span>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://hdl.handle.net/2060/20050041969','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050041969"><span>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('http://adsabs.harvard.edu/abs/2016SMaS...25h5002P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SMaS...25h5002P"><span>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.osti.gov/scitech/biblio/271734','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/271734"><span>Activation energy for superplastic flow in aluminum matrix composites exhibiting high-<span class="hlt">strain-rate</span> superplasticity</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mabuchi, M.; Higashi, K.</p> <p>1996-06-15</p> <p>It is recognized that the activation energy for superplastic flow in metals is in agreement with the activation energy for lattice self-diffusion or for grain boundary diffusion. Moreover, Mishra et al. showed that the activation energy for superplastic flow in a high <span class="hlt">strain</span> <span class="hlt">rate</span> superplastic SiC{sub w}/2124Al composite was 313 KJ/mol and they noted that the activation energy was higher than the activation energy for lattice self-diffusion of aluminum (=142 KJ/mol). Very recently, Higashi et al. revealed that an apparent value of the activation energy for superplastic flow was increased by the presence of a liquid phase for mechanically-alloyed materials exhibiting high-<span class="hlt">strain-rate</span> superplasticity. The same trend was reported in the high-<span class="hlt">strain-rate</span> superplastic Si{sub 3}N{sub 4w}/Al-Zn-Mg composite. However, there are a few works describing the activation energy for superplastic flow in metal matrix composites from the viewpoint of <span class="hlt">effects</span> of a liquid phase. In this paper, the activation energies for superplastic flow in a variety of high-<span class="hlt">strain-rate</span> superplastic Al-Mg(5052), Al-Mg-Si(6061), Al-Zn-Mg(7064) and Al-Cu-Mg(2124) alloy matrix composites have been analyzed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011APS..DPPNO8007R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011APS..DPPNO8007R"><span>High pressure, high <span class="hlt">strain</span> <span class="hlt">rate</span> material strength studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Remington, B. A.; Arsenlis, A.; Barton, N.; Belof, J.; Cavallo, R.; Maddox, B.; Park, H.-S.; Prisbrey, S.; Rudd, R.; Comley, A.; Meyers, M.; Wark, J.</p> <p>2011-10-01</p> <p>Constitutive models for material strength are currently being tested at high pressures by comparing 2D simulations with experiments measuring the Rayleigh-Taylor (RT) instability evolution in solid-state samples of vanadium (V), tantalum (Ta), and iron (Fe). The multiscale strength models being tested combine molecular dynamics, dislocation dynamics, and continuum simulations. Our analysis for the V experiments suggests that the material deformation at these conditions falls into the phonon drag regime, whereas for Ta, the deformation resides mainly in the thermal activation regime. Recent Fe-RT experiments suggest perturbation growth about the alpha-epsilon (bcc-hcp) phase transition threshold has been observed. Using the LLNL multiscale models, we decompose the strength as a function of <span class="hlt">strain</span> <span class="hlt">rate</span> into its dominant components of thermal activation, phonon drag, and work hardening. We have also developed a dynamic diffraction diagnostic technique to measure strength directly from shock compressed single crystal samples. Finally, recovery experiments allow a comparison of residual dislocation density with predictions from the multiscale model. This work performed under the auspices of the U.S. DoE by LLNL Security, LLC under Contract DE-AC52-07NA27344.</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>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('http://adsabs.harvard.edu/abs/1994AIPC..309..721E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1994AIPC..309..721E"><span>High <span class="hlt">strain</span> <span class="hlt">rate</span> modeling of ceramics and ceramic composites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Espinosa, H. D.</p> <p>1994-07-01</p> <p>The high <span class="hlt">strain</span> <span class="hlt">rate</span> response of an AlN/AlN/Al composite manufactured by Lanxide Armor Products, Inc., has been studied through normal and pressure-shear plate impact experiments. Differences in the measured shear resistance, as a function of the impact configuration, motivated the examination of the material response by means of a microcracking multiple-plane model and a continuum elasto-viscoplastic constitutive model. Numerical simulations of the normal impact experiments do not support microcracking as the dominant inelastic mechanism. By contrast, an elasto-viscoplastic description of the material behavior predicts the main features of the normal stress history and the thickness dependence of the Hugoniot elastic limit. Nonetheless, the elasto-viscoplastic model cannot reproduce both the normal and pressure-shear experiments with a single set of model parameters. The inadequacy of the continuum elasto-viscoplastic model seems to result from the isotropic assumption embodied in its formulation. The shear resistance measured in the pressure-shear experiments is adequately predicted by a microcracking multiple-plane model. The agreement seems to hinge in the continuous shearing of the material on a micro-localized fashion, i.e. only one orientation becomes dominant and controls the inelastic shear deformation <span class="hlt">rate</span>. This event does not occur in the normal impact configuration, in which the amount of inelasticity is primarily controlled by the elastic compressibility of the material. These findings explain the higher sensitivity to damage and microplasticity observed in the pressure-shear configuration, as well as the softer material response recorded in this configuration.</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>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('https://ntrs.nasa.gov/search.jsp?R=19820025870&hterms=Stress+test&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DStress%2Btest','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820025870&hterms=Stress+test&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DStress%2Btest"><span>Interaction of heat production, <span class="hlt">strain</span> <span class="hlt">rate</span> and stress power in a plastically deforming body under tensile test</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Paglietti, A.</p> <p>1982-01-01</p> <p>At high <span class="hlt">strain</span> <span class="hlt">rates</span> the heat produced by plastic deformation can give rise to a <span class="hlt">rate</span> dependent response even if the material has <span class="hlt">rate</span> independent constitutive equations. This <span class="hlt">effect</span> has to be evaluated when interpreting a material test, or else it could erroneously be ascribed to viscosity. A general thermodynamic theory of tensile testing of elastic-plastic materials is given in this paper; it is valid for large <span class="hlt">strain</span> at finite <span class="hlt">strain</span> <span class="hlt">rates</span>. It enables discovery of the parameters governing the thermodynamic <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effect</span>, provides a method for proper interpretation of the results of the tests of dynamic plasticity, and suggests a way of planning experiments in order to detect the real contribution of viscosity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820025870&hterms=Tensile+test&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DTensile%2Btest','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820025870&hterms=Tensile+test&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DTensile%2Btest"><span>Interaction of heat production, <span class="hlt">strain</span> <span class="hlt">rate</span> and stress power in a plastically deforming body under tensile test</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Paglietti, A.</p> <p>1982-01-01</p> <p>At high <span class="hlt">strain</span> <span class="hlt">rates</span> the heat produced by plastic deformation can give rise to a <span class="hlt">rate</span> dependent response even if the material has <span class="hlt">rate</span> independent constitutive equations. This <span class="hlt">effect</span> has to be evaluated when interpreting a material test, or else it could erroneously be ascribed to viscosity. A general thermodynamic theory of tensile testing of elastic-plastic materials is given in this paper; it is valid for large <span class="hlt">strain</span> at finite <span class="hlt">strain</span> <span class="hlt">rates</span>. It enables discovery of the parameters governing the thermodynamic <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effect</span>, provides a method for proper interpretation of the results of the tests of dynamic plasticity, and suggests a way of planning experiments in order to detect the real contribution of viscosity.</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>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('https://www.ncbi.nlm.nih.gov/pubmed/21539600','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21539600"><span>Coronary flow reserve, <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> imaging during pharmacological stress before and after percutaneous coronary intervention: comparison and correlation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ojaghi-Haghighi, Zahra; Abtahi, Firoozeh; Fazlolah, Safi; Moladoust, Hassan; Maleki, Majid; Gholami, Saeid</p> <p>2011-05-01</p> <p>Coronary flow reserve (CFR) could apply reliable information about the coronary circulation, and <span class="hlt">strain</span> (S) and <span class="hlt">strain</span> <span class="hlt">rate</span> imaging (SRI) are able to quantify the left ventricular myocardial performance. The aim of this study was to assess myocardial performance in relation to the function of the coronary circulation before and after successful percutaneous coronary intervention (PCI) of the left anterior descending artery. Fourteen patients (10 men, 4 women, mean age 53.2 ± 11.4 years) with severe left anterior descending stenosis who had a successful selective PCI were recruited into this study. CFR and myocardial deformity indices (S and SR) were recorded before and after percutaneous intervention, both at rest and during stress echo test. CFR, S, and SR increased after intervention significantly. There was significant correlation between CFR ratio and poststress systolic <span class="hlt">strain</span> (SS) ratio and early diastolic <span class="hlt">strain</span> <span class="hlt">rate</span> (ESR) ratio (P < 0.05 and r > 0.6). Also CFR improvement had significant relationship with changes of poststress Systolic SR and poststress Systolic S (P < 0.05 and r > 0.6). Based on regression analysis the amount of change in CFR was independently associated with change in SS during stress and systolic SR. PCI improves CFR (a marker of coronary perfusion), <span class="hlt">strain</span>, and <span class="hlt">strain</span> <span class="hlt">rate</span> (markers of regional cardiac wall deformation). The independent association between CFR improvement and poststress systolic <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> means that SRI parameters can independently predict CFR changes after PCI. © 2011, Wiley Periodicals, Inc.</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>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://adsabs.harvard.edu/abs/2010JNuM..405...83E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JNuM..405...83E"><span>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('http://adsabs.harvard.edu/abs/2016PhRvB..93u4108A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvB..93u4108A"><span>Kinetics of the iron α -ɛ phase transition at high-<span class="hlt">strain</span> <span class="hlt">rates</span>: Experiment and model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Amadou, N.; de Resseguier, T.; Brambrink, E.; Vinci, T.; Benuzzi-Mounaix, A.; Huser, G.; Morard, G.; Guyot, F.; Miyanishi, K.; Ozaki, N.; Kodama, R.; Koenig, M.</p> <p>2016-06-01</p> <p>In this article, we investigate the kinetics of the iron α -ɛ transition under laser-driven ramp compression for deformation <span class="hlt">rates</span> ranging from 3 to 9 ×107s-1 . As in previous work, we observe a plateau in the rear surface velocity profile at the transition. With increasing deformation <span class="hlt">rate</span> the transition onset pressure raises from 11 to 25 GPa, while the plateau duration decreases. These kinetic <span class="hlt">effects</span> are well reproduced by an Avrami-type kinetics model of nucleation and growth with a constant, nanosecond scale completion time, which suggests an isokinetic regime over the explored range 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/376399','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/376399"><span>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.dtic.mil/docs/citations/ADA041560','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA041560"><span>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="http://www.dtic.mil/">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> </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/2017PhyE...94..100Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhyE...94..100Z"><span>High <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity of hardness in quinary Ti-Zr-Hf-Cu-Ni high entropy metallic glass thin films</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhao, Shaofan; Wang, Haibin; Xiao, Lin; Guo, Nan; Zhao, Delin; Yao, Kefu; Chen, Na</p> <p>2017-10-01</p> <p>Quinary Ti-Zr-Hf-Cu-Ni high-entropy metallic glass thin films were produced by magnetron sputter deposition. Nanoindentation tests indicate that the deposited film exhibits a relatively large hardness of 10.4±0.6 GPa and a high elastic modulus of 131±11 GPa under the <span class="hlt">strain</span> <span class="hlt">rate</span> of 0.5 s-1. Specifically, the <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity of hardness measured for the thin film is 0.05, the highest value reported for metallic glasses so far. Such high <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity of hardness is likely due to the high-entropy <span class="hlt">effect</span> which stabilizes the amorphous structure with enhanced homogeneity.</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>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('https://www.ncbi.nlm.nih.gov/pubmed/23973615','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23973615"><span>Mechanical characterization of brain tissue in simple shear at dynamic <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>Rashid, Badar; Destrade, Michel; Gilchrist, Michael D</p> <p>2013-12-01</p> <p>During severe impact conditions, brain tissue experiences a rapid and complex deformation, which can be seen as a mixture of compression, tension and shear. Diffuse axonal injury (DAI) occurs in animals and humans when both the <span class="hlt">strains</span> and <span class="hlt">strain</span> <span class="hlt">rates</span> exceed 10% and 10/s, respectively. Knowing the mechanical properties of brain tissue in shear at these <span class="hlt">strains</span> and <span class="hlt">strain</span> <span class="hlt">rates</span> is thus of particular importance, as they can be used in finite element simulations to predict the occurrence of brain injuries under different impact conditions. However, very few studies in the literature provide this information. In this research, an experimental setup was developed to perform simple shear tests on porcine brain tissue at <span class="hlt">strain</span> <span class="hlt">rates</span> ≤120/s. The maximum measured shear stress at <span class="hlt">strain</span> <span class="hlt">rates</span> of 30, 60, 90 and 120/s was 1.15±0.25kPa, 1.34±0.19kPa, 2.19±0.225kPa and 2.52±0.27kPa, (mean±SD), respectively at the maximum amount of shear, K=1. Good agreement of experimental, theoretical (Ogden and Mooney-Rivlin models) and numerical shear stresses was achieved (p=0.7866-0.9935). Specimen thickness <span class="hlt">effects</span> (2.0-10.0mm thick specimens) were also analyzed numerically and we found that there is no significant difference (p=0.9954) in the shear stress magnitudes, indicating a homogeneous deformation of the specimens during simple shear tests. Stress relaxation tests in simple shear were also conducted at different <span class="hlt">strain</span> magnitudes (10-60% <span class="hlt">strain</span>) with the average rise time of 14ms. This allowed us to estimate elastic and viscoelastic parameters (initial shear modulus, μ=4942.0Pa, and Prony parameters: g1=0.520, g2=0.3057, τ1=0.0264s, and τ2=0.011s) that can be used in FE software to analyze the non-linear viscoelastic behavior of brain tissue. This study provides new insight into the behavior in finite shear of brain tissue under dynamic impact conditions, which will assist in developing <span class="hlt">effective</span> brain injury criteria and adopting efficient countermeasures against</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>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://www.osti.gov/scitech/servlets/purl/936455','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/936455"><span>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://adsabs.harvard.edu/abs/2007SMaS...16..191R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007SMaS...16..191R"><span>A one-dimensional <span class="hlt">strain-rate</span>-dependent constitutive model for superelastic shape memory alloys</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ren, Wenjie; Li, Hongnan; Song, Gangbing</p> <p>2007-02-01</p> <p>Recently, there is increasing interest in using superelastic shape memory alloys (SMAs) in civil, mechanical and aerospace engineering, attributed to their large recoverable <span class="hlt">strain</span> range (up to 6-8%), high damping capacity, and excellent fatigue property. In this research, an improved Graesser's model is proposed to model the <span class="hlt">strain-rate</span>-dependent hysteretic behavior of superelastic SMA wires. Cyclic loading tests of superelastic SMA wires are first performed to determine their hysteresis properties. The <span class="hlt">effects</span> of the <span class="hlt">strain</span> amplitude and the loading <span class="hlt">rate</span> on the mechanical properties are studied and formulated using the least-square method. Based on Graesser's model, an improved model is developed. The improved model divides the full loop into three parts: the loading branch, the unloading branch before the completion of the reverse transformation and the elastic unloading branch after the completion of reverse transformation, where each part adopts its respective parameters. Numerical simulations are conducted using both the original and the improved Graesser's models. Comparisons indicate that the improved Graesser's model accurately reflects the hysteresis characteristics and provides a better prediction of the SMAs' actual hysteresis behavior than the original Graesser's model at varying levels of <span class="hlt">strain</span> and loading <span class="hlt">rate</span>.</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>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('https://www.ncbi.nlm.nih.gov/pubmed/20481894','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20481894"><span>Viscous Rayleigh-Taylor instability experiments at high pressure and <span class="hlt">strain</span> <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>Park, Hye-Sook; Lorenz, K T; Cavallo, R M; Pollaine, S M; Prisbrey, S T; Rudd, R E; Becker, R C; Bernier, J V; Remington, B A</p> <p>2010-04-02</p> <p>Experimental results showing significant reductions from classical in the Rayleigh-Taylor instability growth <span class="hlt">rate</span> due to high pressure <span class="hlt">effective</span> lattice viscosity are presented. Using a laser created ramped drive, vanadium samples are compressed and accelerated quasi-isentropically at approximately 1 Mbar peak pressures, while maintaining the sample in the solid state. Comparisons with simulations and theory indicate that the high pressure, high <span class="hlt">strain</span> <span class="hlt">rate</span> conditions trigger a phonon drag mechanism, resulting in the observed high <span class="hlt">effective</span> lattice viscosity and strong stabilization of the Rayleigh-Taylor instability.</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>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.dtic.mil/docs/citations/ADA305387','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA305387"><span>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="http://www.dtic.mil/">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('http://adsabs.harvard.edu/abs/2013APS..SHK.W4006R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013APS..SHK.W4006R"><span>Plasticity mechanisms in nanovoided b.c.c. metals 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>Ruestes, Carlos; Bringa, Eduardo; Stukowski, Alexander; Rodríguez Nieva, Joaquin; Bertolino, Graciela; Tang, Yizhe; Meyers, Marc</p> <p>2013-06-01</p> <p>Atomistic-scale simulations provide unique insights to plasticity mechanisms arising under extreme conditions where its relative nanoscopic length and time scales render experiments almost impossible. Our studies 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 for a Ta single crystal with a collection of spherical nanovoids, with a radius of 3-4 nm, providing an initial porosity of 5%-20%. We examine <span class="hlt">strain</span> <span class="hlt">rate</span> <span class="hlt">effects</span>, from 107/s to 1010/s, in the dislocation density and dislocation-induced heating. The resulting dislocation densities are in good agreement with experimental results for shock-recovered samples. This research was funded by the ANPCyT project PICT2008-1325, PICT2009-0092, PRH and 06/M035 from SecTyP-U.N.Cuyo and UC Research Labs.</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>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('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>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.osti.gov/scitech/biblio/364023','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/364023"><span>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/26275487','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26275487"><span>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. Copyright © 2015 Elsevier Ltd. All rights reserved.</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>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://adsabs.harvard.edu/abs/2017PhRvB..95q4517L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhRvB..95q4517L"><span>Fractional Josephson <span class="hlt">effect</span> in nonuniformly <span class="hlt">strained</span> graphene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Shu-Ping; Nandi, Debaleena; Marsiglio, Frank; Maciejko, Joseph</p> <p>2017-05-01</p> <p>Nonuniform <span class="hlt">strain</span> distributions in a graphene lattice can give rise to uniform pseudomagnetic fields and associated pseudo-Landau levels without breaking time-reversal symmetry. We demonstrate that by inducing superconductivity in a nonuniformly <span class="hlt">strained</span> graphene sheet, the lowest pseudo-Landau levels split by a pairing gap can be inverted by changing the sign of the pairing potential. As a consequence of this inversion, we predict that a Josephson π junction deposited on top of a <span class="hlt">strained</span> graphene sheet exhibits one-dimensional gapless modes propagating along the junction. These gapless modes mediate single electron tunneling across the junction, giving rise to the 4 π -periodic fractional Josephson <span class="hlt">effect</span>.</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>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://adsabs.harvard.edu/abs/2001SPIE.4317..106B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001SPIE.4317..106B"><span>High-<span class="hlt">strain-rate</span> characterization of TPOs and graphite/epoxy and graphite/peek composites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brar, N. S.; Simha, H.; Pratap, A.</p> <p>2001-06-01</p> <p>Tensile and compressive stress-<span class="hlt">strain</span> response of two types of TPOs and graphite-epoxy composites are investigated at <span class="hlt">strain</span> <span class="hlt">rates</span> in the range 0.001/s-1000/s. Specimen <span class="hlt">strain</span> in the low <span class="hlt">strain</span> <span class="hlt">rate</span> regime 0.001-100/s was determined using an optical extensometer in conjunction with standard MTS machine. Tensile test at high <span class="hlt">strain</span> <span class="hlt">rate</span> were performed on newly developed tensile version of All- Polymeric Split Hopkinson Bar. Tensile TPO specimens in the dog-bone configuration are placed in specially designed grips fabricated from nylatron. Compression response of TPO specimens at high <span class="hlt">strain</span> <span class="hlt">rate</span> is determined using 25.4-mm diameter aluminum bars. Peak compressive stress increases from 10 MPa at a <span class="hlt">strain</span> <span class="hlt">rate</span> of 100/s to 35 MPa at a <span class="hlt">strain</span> <span class="hlt">rate</span> of 1000/s. Preliminary data on high <span class="hlt">strain</span> <span class="hlt">rate</span> tensile response of graphite-epoxy and graphite-peek composites are presented. These data are intended to develop a material model incorporating <span class="hlt">strain</span> <span class="hlt">rate</span> sensitivity for TPOs and to be used in car crash simulations.</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>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> </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('https://www.ncbi.nlm.nih.gov/pubmed/21994062','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21994062"><span>Maximum principal <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> associated with concussion diagnosis correlates with changes in corpus callosum white matter indices.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>McAllister, Thomas W; Ford, James C; Ji, Songbai; Beckwith, Jonathan G; Flashman, Laura A; Paulsen, Keith; Greenwald, Richard M</p> <p>2012-01-01</p> <p>On-field monitoring of head impacts, combined with finite element (FE) biomechanical simulation, allow for predictions of regional <span class="hlt">strain</span> associated with a diagnosed concussion. However, attempts to correlate these predictions with in vivo measures of brain injury have not been published. This article reports an approach to and preliminary results from the correlation of subject-specific FE model-predicted regions of high <span class="hlt">strain</span> associated with diagnosed concussion and diffusion tensor imaging to assess changes in white matter integrity in the corpus callosum (CC). Ten football and ice hockey players who wore instrumented helmets to record head impacts sustained during play completed high field magnetic resonance imaging preseason and within 10 days of a diagnosed concussion. The Dartmouth Subject-Specific FE Head model was used to generate regional predictions of <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> following each impact associated with concussion. Maps of change in fractional anisotropy (FA) and median diffusivity (MD) were generated for the CC of each athlete to correlate <span class="hlt">strain</span> with change in FA and MD. Mean and maximum <span class="hlt">strain</span> <span class="hlt">rate</span> correlated with change in FA (Spearman ρ = 0.77, p = 0.01; 0.70, p = 0.031), and there was a similar trend for mean and maximum <span class="hlt">strain</span> (0.56, p = 0.10; 0.6, p = 0.07), as well as for maximum <span class="hlt">strain</span> with change in MD (-0.63, p = 0.07). Change in MD correlated with injury-to-imaging interval (ρ = -0.80, p = 0.006) but change in FA did not (ρ = 0.18, p = 0.62). These results provide preliminary confirmation that model-predicted <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> in the CC correlate with changes in indices of white matter integrity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4388259','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4388259"><span>Maximum Principal <span class="hlt">Strain</span> and <span class="hlt">Strain</span> <span class="hlt">Rate</span> Associated with Concussion Diagnosis Correlates with Changes in Corpus Callosum White Matter Indices</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>MCALLISTER, THOMAS W.; FORD, JAMES C.; JI, SONGBAI; BECKWITH, JONATHAN G.; FLASHMAN, LAURA A.; PAULSEN, KEITH; GREENWALD, RICHARD M.</p> <p>2014-01-01</p> <p>On-field monitoring of head impacts, combined with finite element (FE) biomechanical simulation, allow for predictions of regional <span class="hlt">strain</span> associated with a diagnosed concussion. However, attempts to correlate these predictions with in vivo measures of brain injury have not been published. This article reports an approach to and preliminary results from the correlation of subject-specific FE model-predicted regions of high <span class="hlt">strain</span> associated with diagnosed concussion and diffusion tensor imaging to assess changes in white matter integrity in the corpus callosum (CC). Ten football and ice hockey players who wore instrumented helmets to record head impacts sustained during play completed high field magnetic resonance imaging preseason and within 10 days of a diagnosed concussion. The Dartmouth Subject-Specific FE Head model was used to generate regional predictions of <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> following each impact associated with concussion. Maps of change in fractional anisotropy (FA) and median diffusivity (MD) were generated for the CC of each athlete to correlate <span class="hlt">strain</span> with change in FA and MD. Mean and maximum <span class="hlt">strain</span> <span class="hlt">rate</span> correlated with change in FA (Spearman ρ = 0.77, p = 0.01; 0.70, p = 0.031), and there was a similar trend for mean and maximum <span class="hlt">strain</span> (0.56, p = 0.10; 0.6, p = 0.07), as well as for maximum <span class="hlt">strain</span> with change in MD (−0.63, p = 0.07). Change in MD correlated with injury-to-imaging interval (ρ = −0.80, p = 0.006) but change in FA did not (ρ = 0.18, p = 0.62). These results provide preliminary confirmation that model-predicted <span class="hlt">strain</span> and <span class="hlt">strain</span> <span class="hlt">rate</span> in the CC correlate with changes in indices of white matter integrity. PMID:21994062</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>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="http://www.dtic.mil/">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('https://www.osti.gov/scitech/biblio/175397','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/175397"><span>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('https://www.ncbi.nlm.nih.gov/pubmed/22846301','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22846301"><span>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/2017TDM.....4b4007Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017TDM.....4b4007Z"><span>Valley Hall <span class="hlt">effect</span> and nonlocal transport in <span class="hlt">strained</span> graphene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Xian-Peng; Huang, Chunli; Cazalilla, Miguel A.</p> <p>2017-06-01</p> <p>Graphene subject to high levels of shear <span class="hlt">strain</span> leads to strong pseudo-magnetic fields resulting in the emergence of pseudo-Landau levels. Here we show that, with modest levels of <span class="hlt">strain</span>, graphene can also sustain a classical valley Hall <span class="hlt">effect</span> (VHE) that can be detected in nonlocal transport measurements. We provide a theory of the <span class="hlt">strain</span>-induced VHE starting from the quantum Boltzmann equation. This allows us to show that, averaging over short-range impurity configurations destroys quantum coherence between valleys, leaving the elastic scattering time and inter-valley scattering <span class="hlt">rate</span> as the only parameters characterizing the transport theory. Using the theory, we compute the nonlocal resistance of a Hall bar device in the diffusive regime. Our theory is also relevant for the study of moderate <span class="hlt">strain</span> <span class="hlt">effects</span> in the (nonlocal) transport properties of other two-dimensional materials and van der Walls heterostructures.</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>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.osti.gov/scitech/biblio/1345315','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1345315"><span>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('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>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('http://adsabs.harvard.edu/abs/2013RMRE...46..373H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013RMRE...46..373H"><span>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> <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>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://adsabs.harvard.edu/abs/2016E%26PSL.442...51K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26PSL.442...51K"><span>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>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://www.osti.gov/scitech/servlets/purl/956645','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/956645"><span>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><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>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.ncbi.nlm.nih.gov/pubmed/23408592','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23408592"><span>Comparison of hamstring <span class="hlt">strain</span> injury <span class="hlt">rates</span> between male and female intercollegiate soccer athletes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cross, Kevin M; Gurka, Kelly K; Saliba, Susan; Conaway, Mark; Hertel, Jay</p> <p>2013-04-01</p> <p>Hamstring <span class="hlt">strains</span> are common among soccer athletes, and they have a high incidence of recurrence. Among American collegiate soccer players, men have an overall higher incidence <span class="hlt">rate</span> of hamstring <span class="hlt">strains</span> than women. This research compares the hamstring <span class="hlt">strain</span> injury <span class="hlt">rates</span> in event and athlete characteristics between male and female college soccer athletes. Descriptive epidemiology study. Data describing partial and complete hamstring <span class="hlt">strains</span> were obtained from the National Collegiate Athletic Association (NCAA) Injury Surveillance System (ISS) for men's and women's soccer from 2004 to 2009. Incidence <span class="hlt">rate</span> ratios (IRRs) comparing the incidence of hamstring <span class="hlt">strains</span> between the sexes as well as during games versus practices and the preseason versus the in-season were calculated. χ(2) tests were used to compare the occurrence of hamstring <span class="hlt">strains</span> across different event and athlete characteristics. Men were 64% more likely than women to sustain a hamstring <span class="hlt">strain</span> (IRR, 1.64; 95% CI, 1.37-1.96). Men had significantly higher <span class="hlt">rates</span> of hamstring <span class="hlt">strains</span> than women during both games (IRR, 2.42; 95% CI, 1.82-3.23) and practices (IRR, 1.34; 95% CI, 1.06-1.68). There were no differences between men and women in injury <span class="hlt">rates</span> during the preseason, but men were significantly more likely to sustain a hamstring <span class="hlt">strain</span> during the in-season (IRR, 1.98; 95% CI, 1.56-2.52). Men had a significantly higher proportion of recurrent hamstring <span class="hlt">strains</span> compared with women (men, 22%; women, 12%; P = .003). There were no significant differences in the distribution of <span class="hlt">strains</span> in event or athlete characteristics between men and women for first-time or recurrent hamstring <span class="hlt">strains</span>. In collegiate soccer, men have significantly higher <span class="hlt">rates</span> of hamstring <span class="hlt">strains</span> than women, and regardless of the recurrence status, the event and athlete characteristics were similar for both sexes. Identifying common characteristics may assist in the targeted development of preventive and rehabilitative programs as well</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>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('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>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>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> </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('http://hdl.handle.net/2060/20020052425','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020052425"><span>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('http://adsabs.harvard.edu/abs/2001APS..SHK.L3004B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001APS..SHK.L3004B"><span>Modeling Anisotropic Plasticity: 3D Eulerian Hydrocode Simulations of High <span class="hlt">Strain</span> <span class="hlt">Rate</span> Deformation Processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burkett, Michael; Clancy, Sean; Maudlin, Paul; Holian, Kathleen</p> <p>2001-06-01</p> <p>: Previously developed constitutive models and solution algorithms for anisotropic elastoplastic material strength has been implemented in the three-dimensional CONEJO hydrodynamics code. CONEJO is an explicit, Eulerian continuum mechanics code that is utilized to predict formation processes associated with material deformation at elevated <span class="hlt">strain-rates</span> and is a code development project under the Accelerated Strategic Computing Initiative (ASCI) program. Some special features of CONEJO include a high-order advection algorithm, a material interface tracking scheme, and van Leer monotonic advection-limiting. The anisotropic constitutive modeling is posed in an unrotated material frame using the theorem of polar decomposition to describe rigid body rotation. An Euler-Rodrigues description is used to quantify the rigid body rotations. Continu