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Sample records for applied tensile strain

  1. Tensile-strength apparatus applies high strain-rate loading with minimum shock

    NASA Technical Reports Server (NTRS)

    Cotrill, H. E., Jr.; Mac Glashan, W. F., Jr.

    1966-01-01

    Tensile-strength testing apparatus employs a capillary bundle through which a noncompressible fluid is extruded and a quick-release valve system. This apparatus applies the test loads at relatively constant very high strain rates with minimal shock and vibration to the tensile specimen and apparatus.

  2. Development of a novel bioreactor to apply shear stress and tensile strain simultaneously to cell monolayers

    NASA Astrophysics Data System (ADS)

    Breen, Liam T.; McHugh, Peter E.; McCormack, Brendan A.; Muir, Gordon; Quinlan, Nathan J.; Heraty, Kevin B.; Murphy, Bruce P.

    2006-10-01

    To date many bioreactor experiments have investigated the cellular response to isolated in vitro forces. However, in vivo, wall shear stress (WSS) and tensile hoop strain (THS) coexist. This article describes the techniques used to build and validate a novel vascular tissue bioreactor, which is capable of applying simultaneous wall shear stress and tensile stretch to multiple cellular substrates. The bioreactor design presented here combines a cone and plate rheometer with flexible substrates. Using such a combination, the bioreactor is capable of applying a large range of pulsatile wall shear stress (-30to+30dyn/cm2) and tensile hoop strain (0%-12%). The WSS and THS applied to the cellular substrates were validated and calibrated. In particular, curves were produced that related the desired WSS to the bioreactor control parameters. The bioreactor was shown to be biocompatible and noncytotoxic and suitable for cellular mechanical loading studies in physiological condition, i.e., under simultaneous WSS and THS conditions.

  3. Change of the V I curve and critical current with applied tensile strain due to cracking of filaments in Bi2223 composite tape

    NASA Astrophysics Data System (ADS)

    Shin, J. K.; Ochiai, S.; Okuda, H.; Sugano, M.; Oh, S. S.

    2008-11-01

    The critical current at 77 K of multifilamentary Bi2223 composite tape was studied under applied tensile strain experimentally and analytically. Beyond the irreversible strain, the critical currents (IC) decreased significantly with increasing applied tensile strain (ɛc), due to the enhanced cracking of the Bi2223 filaments. The voltage generation in the voltage-current relation was calculated by the current share model in which the transport current is shared by the Bi2223 filament and Ag near the cracked portion. Then the critical current was estimated with a 1 µV cm-1 criterion. By the application of the current share model to the experimental result, the effective crack length responsible for the reduction in critical current was estimated, with which the change of critical current could be described satisfactorily as a function of applied strain.

  4. Advanced resistivity model for arbitrary magnetization orientation applied to a series of compressive- to tensile-strained (Ga,Mn)As layers

    NASA Astrophysics Data System (ADS)

    Limmer, W.; Daeubler, J.; Dreher, L.; Glunk, M.; Schoch, W.; Schwaiger, S.; Sauer, R.

    2008-05-01

    The longitudinal and transverse resistivities of differently strained (Ga,Mn)As layers are theoretically and experimentally studied as a function of the magnetization orientation. The strain in the series of (Ga,Mn)As layers is gradually varied from compressive to tensile using (In,Ga)As templates with different In concentrations. Analytical expressions for the resistivities are derived from a series expansion of the resistivity tensor with respect to the direction cosines of the magnetization. In order to quantitatively model the experimental data, terms up to the fourth order have to be included. The expressions derived are generally valid for any single-crystalline cubic and tetragonal ferromagnet and apply to arbitrary surface orientations and current directions. The model phenomenologically incorporates the longitudinal and transverse anisotropic magnetoresistance as well as the anomalous Hall effect. The resistivity parameters obtained from a comparison between experiment and theory are found to systematically vary with the strain in the layer.

  5. Cyclic tensile strain upregulates collagen synthesis in isolated tendon fascicles

    SciTech Connect

    Screen, Hazel R.C. . E-mail: H.R.C.Screen@qmul.ac.uk; Shelton, Julia C.; Bader, Dan L.; Lee, David A.

    2005-10-21

    Mechanical stimulation has been implicated as an important regulatory factor in tendon homeostasis. In this study, a custom-designed tensile loading system was used to apply controlled mechanical stimulation to isolated tendon fascicles, in order to examine the effects of 5% cyclic tensile strain at 1 Hz on cell proliferation and matrix synthesis. Sample viability and gross structural composition were maintained over a 24 h loading period. Data demonstrated no statistically significant differences in cell proliferation or glycosaminoglycan production, however, collagen synthesis was upregulated with the application of cyclic tensile strain over the 24 h period. Moreover, a greater proportion of the newly synthesised matrix was retained within the sample after loading. These data provide evidence of altered anabolic activity within tendon in response to mechanical stimuli, and suggest the importance of cyclic tensile loading for the maintenance of the collagen hierarchy within tendon.

  6. Tensile and Microindentation Stress-Strain Curves of Al-6061

    DOE Data Explorer

    Weaver, Jordan S [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Center for Integrated Nanotechnologies (CINT); Khosravani, Ali [Georgia Inst. of Technology, Atlanta, GA (United States); Castillo, Andrew [Georgia Inst. of Technology, Atlanta, GA (United States); Kalidind, Surya R [Georgia Inst. of Technology, Atlanta, GA (United States)

    2016-07-13

    Recent spherical microindentation stress-strain protocols were developed and validated on Al-6061 (DOI: 10.1186/s40192-016-0054-3). The scaling factor between the uniaxial yield strength and the indentation yield strength was determined to be about 1.9. The microindentation stress-strain protocols were then applied to a microstructurally graded sample in an effort to extract high throughput process-property relationships. The tensile and microindentation force-displacement and stress-strain data are presented in this data set.

  7. Maximizing Tensile Strain in Germanium Nanomembranes for Enhanced Optoelectronic Properties

    NASA Astrophysics Data System (ADS)

    Sanchez Perez, Jose Roberto

    Silicon, germanium, and their alloys, which provide the leading materials platform of microelectronics, are extremely inefficient light emitters because of their indirect fundamental energy band gap. This basic materials property has so far hindered the development of group-IV photonic-active devices, including light emitters and diode lasers, thereby significantly limiting our ability to integrate electronic and photonic functionalities at the chip level. Theoretical studies have predicted that tensile strain in Ge lowers the direct energy band gap relative to the indirect one, and that, with sufficient strain, Ge becomes direct-band gap, thus enabling facile interband light emission and the fabrication of Group IV lasers. It has, however, not been possible to impart sufficient strain to Ge to reach the direct-band gap goal, because bulk Ge fractures at much lower strains. Here it is shown that very thin sheets of Ge(001), called nanomembranes (NMs), can be used to overcome this materials limitation. Germanium nanomembranes (NMs) in the range of thicknesses from 20nm to 100nm were fabricated and then transferred and mounted to a flexible substrate [a polyimide (PI) sheet]. An apparatus was developed to stress the PI/NM combination and provide for in-situ Raman measurements of the strain as a function of applied stress. This arrangement allowed for the introduction of sufficient biaxial tensile strain (>1.7%) to transform Ge to a direct-band gap material, as determined by photoluminescence (PL) measurements and theory. Appropriate shifts in the emission spectrum and increases in PL intensities were observed. The advance in this work was nanomembrane fabrication technology; i.e., making thin enough Ge sheets to accept sufficiently high levels of strain without fracture. It was of interest to determine if the strain at which fracture ultimately does occur can be raised, by evaluating factors that initiate fracture. Attempts to assess the effect of free edges (enchant

  8. Electronic, mechanical and dielectric properties of silicane under tensile strain

    NASA Astrophysics Data System (ADS)

    Jamdagni, Pooja; Kumar, Ashok; Sharma, Munish; Thakur, Anil; Ahluwalia, P. K.

    2015-05-01

    The electronic, mechanical and dielectric properties of fully hydrogenated silicene i.e. silicane in stable configuration are studied by means of density functional theory based calculations. The band gap of silicane monolayer can be flexibly reduced to zero when subjected to bi-axial tensile strain, leading to semi-conducting to metallic transition, whereas the static dielectric constant for in-plane polarization increases monotonically with increasing strain. Also the EEL function show the red shift in resonance peak with tensile strain. Our results offer useful insight for the application of silicane monolayer in nano-optical and electronics devices.

  9. Electronic, mechanical and dielectric properties of silicane under tensile strain

    SciTech Connect

    Jamdagni, Pooja Sharma, Munish; Ahluwalia, P. K.; Kumar, Ashok; Thakur, Anil

    2015-05-15

    The electronic, mechanical and dielectric properties of fully hydrogenated silicene i.e. silicane in stable configuration are studied by means of density functional theory based calculations. The band gap of silicane monolayer can be flexibly reduced to zero when subjected to bi-axial tensile strain, leading to semi-conducting to metallic transition, whereas the static dielectric constant for in-plane polarization increases monotonically with increasing strain. Also the EEL function show the red shift in resonance peak with tensile strain. Our results offer useful insight for the application of silicane monolayer in nano-optical and electronics devices.

  10. Tensile strain mapping in flat germanium membranes

    SciTech Connect

    Rhead, S. D. Halpin, J. E.; Myronov, M.; Patchett, D. H.; Allred, P. S.; Wilson, N. R.; Leadley, D. R.; Shah, V. A.; Kachkanov, V.; Dolbnya, I. P.; Reparaz, J. S.; Sotomayor Torres, C. M.

    2014-04-28

    Scanning X-ray micro-diffraction has been used as a non-destructive probe of the local crystalline quality of a thin suspended germanium (Ge) membrane. A series of reciprocal space maps were obtained with ∼4 μm spatial resolution, from which detailed information on the strain distribution, thickness, and crystalline tilt of the membrane was obtained. We are able to detect a systematic strain variation across the membranes, but show that this is negligible in the context of using the membranes as platforms for further growth. In addition, we show evidence that the interface and surface quality is improved by suspending the Ge.

  11. Three-dimensional development of tensile pre-strained annulus fibrosus cells for tissue regeneration: An in-vitro study

    SciTech Connect

    Chuah, Yon Jin; Lee, Wu Chean; Wong, Hee Kit; Kang, Yuejun; Hee, Hwan Tak

    2015-02-01

    Prior research has investigated the immediate response after application of tensile strain on annulus fibrosus (AF) cells for the past decade. Although mechanical strain can produce either catabolic or anabolic consequences to the cell monolayer, little is known on how to translate these findings into further tissue engineering applications. Till to date, the application and effect of tensile pre-strained cells to construct a three-dimensional (3D) AF tissue remains unknown. This study aims to investigate the effect of tensile pre-strained exposure of 1 to 24 h on the development of AF pellet culture for 3 weeks. Equibiaxial cyclic tensile strain was applied on AF monolayer cells over a period of 24 h, which was subsequently developed into a cell pellet. Investigation on cellular proliferation, phenotypic gene expression, and histological changes revealed that tensile pre-strain for 24 h had significant and lasting effect on the AF tissue development, with enhanced cell proliferation, and up-regulation of collagen type I, II, and aggrecan expression. Our results demonstrated the regenerative ability of AF cell pellets subjected to 24 h tensile pre-straining. Knowledge on the effects of tensile pre-strain exposure is necessary to optimize AF development for tissue reconstruction. Moreover, the tensile pre-strained cells may further be utilized in either cell therapy to treat mild disc degeneration disease, or the development of a disc construct for total disc replacement. - Highlights: • Establishment of tensile pre-strained cell line population for annulus development. • Tensile strain limits collagen gene expression declination in monolayer culture. • Tensile pre-strained cells up-regulate their matrix protein in 3D pellet culture.

  12. Tensile stress-strain behavior of boron/aluminum laminates

    NASA Technical Reports Server (NTRS)

    Sova, J. A.; Poe, C. C., Jr.

    1978-01-01

    The tensile stress-strain behavior of five types of boron/aluminum laminates was investigated. Longitudinal and transverse stress-strain curves were obtained for monotonic loading to failure and for three cycles of loading to successively higher load levels. The laminate strengths predicted by assuming that the zero deg plies failed first correlated well with the experimental results. The stress-strain curves for all the boron/aluminum laminates were nonlinear except at very small strains. Within the small linear regions, elastic constants calculated from laminate theory corresponded to those obtained experimentally to within 10 to 20 percent. A limited amount of cyclic loading did not affect the ultimate strength and strain for the boron/aluminum laminates. The laminates, however, exhibited a permanent strain on unloading. The Ramberg-Osgood equation was fitted to the stress-strain curves to obtain average curves for the various laminates.

  13. Absence of rippling in graphene under biaxial tensile strain

    NASA Astrophysics Data System (ADS)

    Rakshit, Bipul; Mahadevan, Priya

    2010-10-01

    Recent experiments [C. H. Lui, L. Liu, K. F. Mak, G. W. Flynn, and T. F. Heinz, Nature (London) 462, 339 (2009)10.1038/nature08569] on graphene grown on ultraflat substrates have found no rippling in graphene when subject to temperature cycling. Unsupported/unstrained films of graphene as well as films grown on various substrates on the other hand have been found to show rippling effects. As graphene grown on a substrate is invariably strained, we examine the behavior of the out-of-plane acoustic-phonon mode with biaxial tensile strain. This mode is generally associated with the rippling of graphene. We find that it can be fit to a relation of the form w2=Ak4+Bk2 , where w and k are the frequency and wave vector, respectively. The coefficient A is found to show a weak dependence on strain while B is found to increase linearly with strain. The strain-induced hardening explains the absence of rippling in graphene subject to biaxial strain. In addition, we find that graphene when subject to a biaxial tensile strain is found to undergo a structural transition with the mode at K going soft at a strain percentage of 15%.

  14. Tensile stress-strain behavior of graphite/epoxy laminates

    NASA Technical Reports Server (NTRS)

    Garber, D. P.

    1982-01-01

    The tensile stress-strain behavior of a variety of graphite/epoxy laminates was examined. Longitudinal and transverse specimens from eleven different layups were monotonically loaded in tension to failure. Ultimate strength, ultimate strain, and strss-strain curves wee obtained from four replicate tests in each case. Polynominal equations were fitted by the method of least squares to the stress-strain data to determine average curves. Values of Young's modulus and Poisson's ratio, derived from polynomial coefficients, were compared with laminate analysis results. While the polynomials appeared to accurately fit the stress-strain data in most cases, the use of polynomial coefficients to calculate elastic moduli appeared to be of questionable value in cases involving sharp changes in the slope of the stress-strain data or extensive scatter.

  15. Mechanical Testing of TR-55 Rubber Thermally Aged Under Tensile Strain

    SciTech Connect

    Small IV, W; Alviso, C T; Wilson, T S; Chinn, S C; Maxwell, R S

    2009-03-10

    TR-55 rubber specimens were previously subjected to an aging process consisting of the application of a tensile strain of approximately 67%, 100%, 133%, or 167% elongation for 4, 8, 12, or 16 h at either 250 C or room temperature. Control specimens at the same temperatures/durations were not subjected to tensile strain. The specimens were allowed to recover at room temperature without external stimuli for over 100 days before tensile testing. A single dog bone was cut from each specimen and a stress-strain curve was obtained. The elastic modulus of each specimen was calculated. Specimens aged under tensile strain exhibited rubber-like behavior dependent on the aging elongation and duration. This behavior was not evident in the unstrained controls. For the unstrained controls, exposure to 250 C resulted in an increase in modulus relative to the unheated material independent of the heating duration. The tensile strain applied during the aging process caused a reduction in modulus relative to the controls; lower moduli were observed for the shorter aging durations. Slippage of the specimens in the grips prevented determination of ultimate strength, as all specimens either slipped completely out of the grip before failure or failed at the original grip edge after slipping.

  16. Optical strain measuring techniques for high temperature tensile testing

    NASA Technical Reports Server (NTRS)

    Gyekenyesi, John Z.; Hemann, John H.

    1987-01-01

    A number of optical techniques used for the analysis of in-plane displacements or strains are reviewed. The application would be for the high temperature, approximately 1430 C (2600 F), tensile testing of ceramic composites in an oxidizing atmosphere. General descriptions of the various techniques and specifics such as gauge lengths and sensitivities are noted. Also, possible problems with the use of each method in the given application are discussed.

  17. Tensile-strained germanium microdisks with circular Bragg reflectors

    NASA Astrophysics Data System (ADS)

    El Kurdi, M.; Prost, M.; Ghrib, A.; Elbaz, A.; Sauvage, S.; Checoury, X.; Beaudoin, G.; Sagnes, I.; Picardi, G.; Ossikovski, R.; Boeuf, F.; Boucaud, P.

    2016-02-01

    We demonstrate the combination of germanium microdisks tensily strained by silicon nitride layers and circular Bragg reflectors. The microdisks with suspended lateral Bragg reflectors form a cavity with quality factors up to 2000 around 2 μm. This represents a key feature to achieve a microlaser with a quasi-direct band gap germanium under a 1.6% biaxial tensile strain. We show that lowering the temperature significantly improves the quality factor of the quasi-radial modes. Linewidth narrowing is observed in a range of weak continuous wave excitation powers. We finally discuss the requirements to achieve lasing with these kind of structures.

  18. Tuning the Electro-optical Properties of Germanium Nanowires by Tensile Strain

    PubMed Central

    2012-01-01

    In this Letter we present the electrical and electro-optical characterization of single crystalline germanium nanowires (NWs) under tensile strain conditions. The measurements were performed on vapor–liquid–solid (VLS) grown germanium (Ge) NWs, monolithically integrated into a micromechanical 3-point strain module. Uniaxial stress is applied along the ⟨111⟩ growth direction of individual, 100 nm thick Ge NWs while at the same time performing electrical and optical characterization at room temperature. Compared to bulk germanium, an anomalously high and negative-signed piezoresistive coefficient has been found. Spectrally resolved photocurrent characterization on strained NWs gives experimental evidence on the strain-induced modifications of the band structure. Particularly we are revealing a rapid decrease in resistivity and a red-shift in photocurrent spectra under high strain conditions. For a tensile strain of 1.8%, resistivity decreased by a factor of 30, and the photocurrent spectra shifted by 88 meV. Individual stressed NWs are recognized as an ideal platform for the exploration of strain-related electronic and optical effects and may contribute significantly to the realization of novel optoelectronic devices, strain-enhanced field-effect transistors (FETs), or highly sensitive strain gauges. PMID:23146072

  19. High Strain Rate Tensile Testing of DOP-26 Iridium

    SciTech Connect

    Schneibel, Joachim H; Carmichael Jr, Cecil Albert; George, Easo P

    2007-11-01

    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 strain rates 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 strain rate. 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 strain rate. The reduction in area (RA), on the other hand, decreased with increasing strain rate. 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.

  20. Tensile strain-induced softening of iron at high temperature.

    PubMed

    Li, Xiaoqing; Schönecker, Stephan; Simon, Eszter; Bergqvist, Lars; Zhang, Hualei; Szunyogh, László; Zhao, Jijun; Johansson, Börje; Vitos, Levente

    2015-01-01

    In weakly ferromagnetic materials, already small changes in the atomic configuration triggered by temperature or chemistry can alter the magnetic interactions responsible for the non-random atomic-spin orientation. Different magnetic states, in turn, can give rise to substantially different macroscopic properties. A classical example is iron, which exhibits a great variety of properties as one gradually removes the magnetic long-range order by raising the temperature towards its Curie point of  TC°= 1043 K. Using first-principles theory, here we demonstrate that uniaxial tensile strain can also destabilise the magnetic order in iron and eventually lead to a ferromagnetic to paramagnetic transition at temperatures far below TC°. In consequence, the intrinsic strength of the ideal single-crystal body-centred cubic iron dramatically weakens above a critical temperature of ~500 K. The discovered strain-induced magneto-mechanical softening provides a plausible atomic-level mechanism behind the observed drop of the measured strength of Fe whiskers around 300-500 K. Alloying additions which have the capability to partially restore the magnetic order in the strained Fe lattice, push the critical temperature for the strength-softening scenario towards the magnetic transition temperature of the undeformed lattice. This can result in a surprisingly large alloying-driven strengthening effect at high temperature as illustrated here in the case of Fe-Co alloy. PMID:26556127

  1. Tensile strain-induced softening of iron at high temperature

    NASA Astrophysics Data System (ADS)

    Li, Xiaoqing; Schönecker, Stephan; Simon, Eszter; Bergqvist, Lars; Zhang, Hualei; Szunyogh, László; Zhao, Jijun; Johansson, Börje; Vitos, Levente

    2015-11-01

    In weakly ferromagnetic materials, already small changes in the atomic configuration triggered by temperature or chemistry can alter the magnetic interactions responsible for the non-random atomic-spin orientation. Different magnetic states, in turn, can give rise to substantially different macroscopic properties. A classical example is iron, which exhibits a great variety of properties as one gradually removes the magnetic long-range order by raising the temperature towards its Curie point of  = 1043 K. Using first-principles theory, here we demonstrate that uniaxial tensile strain can also destabilise the magnetic order in iron and eventually lead to a ferromagnetic to paramagnetic transition at temperatures far below . In consequence, the intrinsic strength of the ideal single-crystal body-centred cubic iron dramatically weakens above a critical temperature of ~500 K. The discovered strain-induced magneto-mechanical softening provides a plausible atomic-level mechanism behind the observed drop of the measured strength of Fe whiskers around 300-500 K. Alloying additions which have the capability to partially restore the magnetic order in the strained Fe lattice, push the critical temperature for the strength-softening scenario towards the magnetic transition temperature of the undeformed lattice. This can result in a surprisingly large alloying-driven strengthening effect at high temperature as illustrated here in the case of Fe-Co alloy.

  2. Tensile strain-induced softening of iron at high temperature

    PubMed Central

    Li, Xiaoqing; Schönecker, Stephan; Simon, Eszter; Bergqvist, Lars; Zhang, Hualei; Szunyogh, László; Zhao, Jijun; Johansson, Börje; Vitos, Levente

    2015-01-01

    In weakly ferromagnetic materials, already small changes in the atomic configuration triggered by temperature or chemistry can alter the magnetic interactions responsible for the non-random atomic-spin orientation. Different magnetic states, in turn, can give rise to substantially different macroscopic properties. A classical example is iron, which exhibits a great variety of properties as one gradually removes the magnetic long-range order by raising the temperature towards its Curie point of  = 1043 K. Using first-principles theory, here we demonstrate that uniaxial tensile strain can also destabilise the magnetic order in iron and eventually lead to a ferromagnetic to paramagnetic transition at temperatures far below . In consequence, the intrinsic strength of the ideal single-crystal body-centred cubic iron dramatically weakens above a critical temperature of ~500 K. The discovered strain-induced magneto-mechanical softening provides a plausible atomic-level mechanism behind the observed drop of the measured strength of Fe whiskers around 300–500 K. Alloying additions which have the capability to partially restore the magnetic order in the strained Fe lattice, push the critical temperature for the strength-softening scenario towards the magnetic transition temperature of the undeformed lattice. This can result in a surprisingly large alloying-driven strengthening effect at high temperature as illustrated here in the case of Fe-Co alloy. PMID:26556127

  3. Tensile strain engineering of germanium micro-disks on free-standing SiO2 beams

    NASA Astrophysics Data System (ADS)

    Al-Attili, Abdelrahman Z.; Kako, Satoshi; Husain, Muhammad K.; Gardes, Frederic Y.; Iwamoto, Satoshi; Arakawa, Yasuhiko; Saito, Shinichi

    2016-04-01

    Tensile strain is required to enhance light-emitting direct-gap recombinations in germanium (Ge), which is a promising group IV material for realizing a monolithic light source on Si. Ge micro-disks on free-standing SiO2 beams were fabricated using Ge-on-Insulator wafers for applying tensile strain to Ge in a structure compatible with an optical confinement. We have studied the nature of the strain by Raman spectroscopy in comparison with finite-element computer simulations. We show the impacts of the beam design on the corresponding strain value, orientation, and uniformity, which can be exploited for Ge light emission applications. It was found that the tensile strain values are larger if the length of the beam is smaller. We confirmed that both uniaxial and biaxial strain can be applied to Ge disks, and maximum strain values of 1.1 and 0.6% have been achieved, as confirmed by Raman spectroscopy. From the photoluminescence spectra of Ge micro-disks, we have also found a larger energy-splitting between the light-hole and the heavy-hole bands in shorter beams, indicating the impact of tensile strain.

  4. Polar semiconductor ZnO under inplane tensile strain

    NASA Astrophysics Data System (ADS)

    Alahmed, Zeyad; Fu, Huaxiang

    2008-01-01

    Zinc oxide under biaxial inplane tensile strains is studied theoretically by first-principles density functional calculations. Different material properties (including structural response of cell shape, chemical bonding, total-energy curvature, electrical polarization, Born effective charge, electronic band dispersion, optical interband transitions, and effective masses) are examined. We found that (1) the c/a ratio decreases in a rather linear fashion with the increasing tensile strain when the inplane lattice constant (denoted as a ) of ZnO is varied below a critical transition value of atr=1.067a0 ( a0 is the equilibrium inplane cell length). However, at a=atr , ZnO exhibits a pronounced structural discontinuity in c/a ratio, as well as in cell volume. (2) The structural discontinuity results from the existence of two energy minima (labeled as A and B), both being metastable. Minimum A is energetically favorable when a is below atr , while minimum B is more stable when a exceeds atr . (3) As the inplane lattice constant approaches atr from below, ZnO becomes markedly soft along the polar c axis, promising a large electromechanical response. (4) At a=atr , spontaneous polarization in ZnO collapses, leading to a polar-nonpolar phase transformation. (5) Despite that the spontaneous polarization vanishes when a=atr , Born effective charge of Zn atom nevertheless increases, demonstrating an interesting anticorrelation. (6) Above atr , covalent overlapping charge largely disappears between those polar Zn-O bonds collinear with the c axis, indicating that the bonds are predominantly ionic. (7) The polar-nonpolar structural transformation simultaneously gives rise to a direct-indirect band gap transition. When a is above atr , the valence band maximum is no longer at zone center Γ but at zone-edge H point. Occurrence of indirect band gap originates from the fact that the orbital energy of the top valence state at H shows a sensitive dependence on the inplane strain. (8

  5. Applying strain into graphene by SU-8 resist shrinkage

    NASA Astrophysics Data System (ADS)

    Takamura, Makoto; Hibino, Hiroki; Yamamoto, Hideki

    2016-07-01

    We investigated the use of the shrinkage of SU-8 resist caused by thermal annealing to apply strain into graphene grown by the chemical-vapor-deposition (CVD) method. We demonstrate that the shrinkage of resist deposited on top of graphene on a substrate induces a local tensile strain within a distance of 1–2 μm from the edge of the resist. The thermal shrinkage of SU-8 will allow us to design the local strain in graphene on substrates. We also show that the shrinkage induces a large tensile strain in graphene suspended between two bars of SU-8. We expect that a much larger strain can be induced by suppressing defects in CVD-grown graphene.

  6. Examination of a Rock Failure Criterion Based on Circumferential Tensile Strain

    NASA Astrophysics Data System (ADS)

    Fujii, , Y.; Kiyama, , T.; Ishijima, Y.; Kodama, J.

    Uniaxial compression, triaxial compression and Brazialian tests were conducted on several kinds of rock, with particular attention directed to the principal tensile strain. In this paper we aim to clarify the effects of the experimental environment-such as confining pressure, loading rate, water content and anisotropy-on the critical tensile strain, i.e., the measured principal tensile strain at peak load.It was determined that the chain-type extensometer is a most suitable method for measuring the critical tensile strain in uniaxial compression tests. It is also shown that the paper-based strain gage, whose effective length is less than or equal to a tenth of the specimen's diameter and glued on with a rubber-type adhesive, can be effectively used in the Brazilian tests.The effect of confining pressure PC on the critical tensile strain ɛTC in the brittle failure region was between -0.02 × 10-10 Pa-1 and 0.77 × 10-10 Pa-1. This pressure sensitivity is small compared to the critical tensile strain values of around -0.5 × 10-2. The strain rate sensitivities ∂ɛTC/∂{log(d|ɛ|/dt)} were observed in the same way as the strength constants in other failure criteria. They were found to be from -0.10 × 10-3 to -0.52 × 10-3 per order of magnitude in strain rate in the triaxial tests. The average magnitude of the critical tensile strain ɛTC increased due to the presence of water by 4% to 20% for some rocks, and decreased by 22% for sandstone. It can at least be said that the critical tensile strain is less sensitive to water content than the uniaxial compressive strength under the experimental conditions reported here. An obvious anisotropy was observed in the P-wave velocity and in the uniaxial compressive strength of Pombetsu sandstone. It was not observed, however, in the critical tensile strain, although the data do show some variation.A "tensile strain criterion" was proposed, based on the above experimental results. This criterion signifies that stress begins

  7. Multiscale Computer Simulation of Tensile and Compressive Strain in Polymer- Coated Silica Aerogels

    NASA Technical Reports Server (NTRS)

    Good, Brian

    2009-01-01

    While the low thermal conductivities of silica aerogels have made them of interest to the aerospace community as lightweight thermal insulation, the application of conformal polymer coatings to these gels increases their strength significantly, making them potentially useful as structural materials as well. In this work we perform multiscale computer simulations to investigate the tensile and compressive strain behavior of silica and polymer-coated silica aerogels. Aerogels are made up of clusters of interconnected particles of amorphous silica of less than bulk density. We simulate gel nanostructure using a Diffusion Limited Cluster Aggregation (DLCA) procedure, which produces aggregates that exhibit fractal dimensions similar to those observed in real aerogels. We have previously found that model gels obtained via DLCA exhibited stress-strain curves characteristic of the experimentally observed brittle failure. However, the strain energetics near the expected point of failure were not consistent with such failure. This shortcoming may be due to the fact that the DLCA process produces model gels that are lacking in closed-loop substructures, compared with real gels. Our model gels therefore contain an excess of dangling strands, which tend to unravel under tensile strain, producing non-brittle failure. To address this problem, we have incorporated a modification to the DLCA algorithm that specifically produces closed loops in the model gels. We obtain the strain energetics of interparticle connections via atomistic molecular statics, and abstract the collective energy of the atomic bonds into a Morse potential scaled to describe gel particle interactions. Polymer coatings are similarly described. We apply repeated small uniaxial strains to DLCA clusters, and allow relaxation of the center eighty percent of the cluster between strains. The simulations produce energetics and stress-strain curves for looped and nonlooped clusters, for a variety of densities and

  8. High-strain rate tensile characterization of graphite platelet reinforced vinyl ester based nanocomposites using split-Hopkinson pressure bar

    NASA Astrophysics Data System (ADS)

    Pramanik, Brahmananda

    The dynamic response of exfoliated graphite nanoplatelet (xGnP) reinforced and carboxyl terminated butadiene nitrile (CTBN) toughened vinyl ester based nanocomposites are characterized under both dynamic tensile and compressive loading. Dynamic direct tensile tests are performed applying the reverse impact Split Hopkinson Pressure Bar (SHPB) technique. The specimen geometry for tensile test is parametrically optimized by Finite Element Analysis (FEA) using ANSYS Mechanical APDLRTM. Uniform stress distribution within the specimen gage length has been verified using high-speed digital photography. The on-specimen strain gage installation is substituted by a non-contact Laser Occlusion Expansion Gage (LOEG) technique for infinitesimal dynamic tensile strain measurements. Due to very low transmitted pulse signal, an alternative approach based on incident pulse is applied for obtaining the stress-time history. Indirect tensile tests are also performed combining the conventional SHPB technique with Brazilian disk test method for evaluating cylindrical disk specimens. The cylindrical disk specimen is held snugly in between two concave end fixtures attached to the incident and transmission bars. Indirect tensile stress is estimated from the SHPB pulses, and diametrical transverse tensile strain is measured using LOEG. Failure diagnosis using high-speed digital photography validates the viability of utilizing this indirect test method for characterizing the tensile properties of the candidate vinyl ester based nanocomposite system. Also, quasi-static indirect tensile response agrees with previous investigations conducted using the traditional dog-bone specimen in quasi-static direct tensile tests. Investigation of both quasi-static and dynamic indirect tensile test responses show the strain rate effect on the tensile strength and energy absorbing capacity of the candidate materials. Finally, the conventional compressive SHPB tests are performed. It is observed that both

  9. 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.

  10. Analysis of optical gain threshold in n-doped and tensile-strained germanium heterostructure diodes

    NASA Astrophysics Data System (ADS)

    Prost, M.; El Kurdi, M.; Aniel, F.; Zerounian, N.; Sauvage, S.; Checoury, X.; BÅ`uf, F.; Boucaud, P.

    2015-09-01

    The optical emission of germanium-based luminescent and/or laser devices can be enhanced by tensile strain and n-type doping. In this work, we study by simulation the interplay between electrical transport and optical gain in highly n-doped and intrinsic germanium p-n heterostructure diodes under tensile strain. The effects of strain and doping on carrier mobilities and energy distribution are taken into account. Whereas the n-doping of Ge enhances the filling of the indirect L and Brillouin zone-center conduction band states, the n-doping also reduces the carrier injection efficiency, which is detrimental for the achievement of optical gain at reduced current densities. For applied biaxial strains larger than 1.25%, i.e., far before reaching the cross-over from indirect to direct band gap regime, undoped germanium exhibits a lower optical gain threshold as compared to doped germanium. We also show that the threshold current needed to reach transparency in germanium heterostructures has been significantly underestimated in the previous works.

  11. Effect of tensile strain on the negative differential resistance in the WTe2 armchair nanoribbon

    NASA Astrophysics Data System (ADS)

    Ghosh, Bahniman; Gupta, Abhishek; Bishnoi, Bhupesh

    2014-04-01

    In this work, we have studied the charge transport characteristics of WTe2 armchair nanoribbon and analyzed the variation in results by applying tensile strain to the nanoribbon. Tungsten ditelluride (WTe2) is a member of the transition metal dichalcogenides family. WTe2 is orthorhombic in structure with lattice parameters a = 0.6282 nm, b = 0.3496 nm, c = 1.407 nm. We have simulated the model using first-principle density functional tight binding theory and the non-equilibrium Green’s function method to study the effect of strain on the transport characteristics. The obtained results are compared with that of the perfectly relaxed nanoribbon. We have applied uniaxial (ɛ xx) and biaxial (ɛ xx = ɛ yy) tensile strain to the nanoribbon. We present the ID-VDS characteristics, transmission spectrum and conductance for different cases. Negative differential resistance (NDR) is observed in all the cases along with a change in peak-to-valley current ratio (PVCR) and negative differential resistance region (NDRR).

  12. Tensile Strength of Carbon Nanotubes Under Realistic Temperature and Strain Rate

    NASA Technical Reports Server (NTRS)

    Wei, Chen-Yu; Cho, Kyeong-Jae; Srivastava, Deepak; Biegel, Bryan (Technical Monitor)

    2002-01-01

    Strain rate and temperature dependence of the tensile strength of single-wall carbon nanotubes has been investigated with molecular dynamics simulations. The tensile failure or yield strain is found to be strongly dependent on the temperature and strain rate. A transition state theory based predictive model is developed for the tensile failure of nanotubes. Based on the parameters fitted from high-strain rate and temperature dependent molecular dynamics simulations, the model predicts that a defect free micrometer long single-wall nanotube at 300 K, stretched with a strain rate of 1%/hour, fails at about 9 plus or minus 1% tensile strain. This is in good agreement with recent experimental findings.

  13. Experimental and Numerical Study on Tensile Strength of Concrete under Different Strain Rates

    PubMed Central

    Min, Fanlu; Yao, Zhanhu; Jiang, Teng

    2014-01-01

    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 strain rates of 10−7 s−1 to 10−4 s−1 in an MTS material test machine. Results of tensile strength versus strain rate are presented and compared with compressive strength and existing models at similar strain rates. Dynamic increase factor versus strain rate 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 strain rate sensitive behavior, exhibiting dynamic tensile strength increasing with strain rate. In the quasistatic strain rate 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 effect of strain rates. PMID:24883355

  14. Experimental and numerical study on tensile strength of concrete under different strain rates.

    PubMed

    Min, Fanlu; Yao, Zhanhu; Jiang, Teng

    2014-01-01

    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 strain rates of 10(-7) s(-1) to 10(-4) s(-1) in an MTS material test machine. Results of tensile strength versus strain rate are presented and compared with compressive strength and existing models at similar strain rates. Dynamic increase factor versus strain rate 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 strain rate sensitive behavior, exhibiting dynamic tensile strength increasing with strain rate. In the quasistatic strain rate 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 effect of strain rates. PMID:24883355

  15. Effect of strain rate on formability in warm deep drawing of high tensile strength steel sheet

    NASA Astrophysics Data System (ADS)

    Yoshihara, Shoichiro; Iwamatsu, Go

    2014-10-01

    In tensile test of the high tensile strength steel, tensile strength isdrastically decreased as the temperature is raised. Then, the strain rate sensitivity exponent of high tensile strength steel (SUS631) in this study is high at 800 degrees especially. Also, elongation is increased as the temperature is raised. In deep drawing, the maximum punch load of the high tensile strength steel is examined on difference punch speed at 600 and 800 degrees. On the other hand, finite element (FE) simulation was used for the possibility to evaluate the forming load on difference punch speed in warm deep drawing. In FE simulation, we have considered both the strain hardening exponent and the strain rate sensitivity exponent (m-value) because we cannot neglect m-value 0.184 at 800 degrees. The tendency of the forming load in the experiments agrees the results in FE simulation.

  16. Effect of Strain-Induced Martensite on Tensile Properties and Hydrogen Embrittlement of 304 Stainless Steel

    NASA Astrophysics Data System (ADS)

    Kim, Young Suk; Bak, Sang Hwan; Kim, Sung Soo

    2016-01-01

    Room temperature tensile tests have been conducted at different strain rates ranging from 2 × 10-6 to 1 × 10-2/s on hydrogen-free and hydrogen-charged 304 stainless steel (SS). Using a ferritescope and neutron diffraction, the amount of strain-induced martensite (SIM) has been in situ measured at the center region of the gage section of the tensile specimens or ex situ measured on the fractured tensile specimens. The ductility, tensile stress, hardness, and the amount of SIM increase with decreasing strain rate in hydrogen-free 304 SS and decrease in hydrogen-charged one. Specifically, SIM that forms during tensile tests is beneficial in increasing the ductility, strain hardening, and tensile stress of 304 SS, irrespective of the presence of hydrogen. A correlation of the tensile properties of hydrogen-free and hydrogen-charged 304 SS and the amount of SIM shows that hydrogen suppresses the formation of SIM in hydrogen-charged 304 SS, leading to a ductility loss and localized brittle fracture. Consequently, we demonstrate that hydrogen embrittlement of 304 SS is related to hydrogen-suppressed formation of SIM, corresponding to the disordered phase, according to our proposition. Compelling evidence is provided by the observations of the increased lattice expansion of martensite with decreasing strain rate in hydrogen-free 304 SS and its lattice contraction in hydrogen-charged one.

  17. Highly tunable magnetism in silicene doped with Cr and Fe atoms under isotropic and uniaxial tensile strain

    SciTech Connect

    Zheng, Rui; Ni, Jun; Chen, Ying

    2015-12-28

    We have investigated the magnetic properties of silicene doped with Cr and Fe atoms under isotropic and uniaxial tensile strain by the first-principles calculations. We find that Cr and Fe doped silicenes show strain-tunable magnetism. (1) The magnetism of Cr and Fe doped silicenes exhibits sharp transitions from low spin states to high spin states by a small isotropic tensile strain. Specially for Fe doped silicene, a nearly nonmagnetic state changes to a high magnetic state by a small isotropic tensile strain. (2) The magnetic moments of Fe doped silicene also show a sharp jump to ∼2 μ{sub B} at a small threshold of the uniaxial strain, and the magnetic moments of Cr doped silicene increase gradually to ∼4 μ{sub B} with the increase of uniaxial strain. (3) The electronic and magnetic properties of Cr and Fe doped silicenes are sensitive to the magnitude and direction of the external strain. The highly tunable magnetism may be applied in the spintronic devices.

  18. Suspended germanium cross-shaped microstructures for enhancing biaxial tensile strain

    NASA Astrophysics Data System (ADS)

    Ishida, Satomi; Kako, Satoshi; Oda, Katsuya; Ido, Tatemi; Iwamoto, Satoshi; Arakawa, Yasuhiko

    2016-04-01

    We fabricate a suspended germanium cross-shaped microstructure to biaxially enhance residual tensile strain using a germanium epilayer directly grown on a silicon-on-insulator substrate. Such a suspended germanium system with enhanced biaxial tensile strain will be a promising platform for incorporating optical cavities toward the realization of germanium lasers. We demonstrate systematic control over biaxial tensile strain and photoluminescence peaks by changing structural geometry. The photoluminescence peaks corresponding to the direct recombination between the conduction Γ valley and two strain-induced separated valence bands have been clearly assigned. A maximum biaxial strain of 0.8% has been achieved, which is almost half of that required to transform germanium into a direct band-gap semiconductor.

  19. Effect of tensile strain on the electronic structure of Ge: A first-principles calculation

    SciTech Connect

    Liu, Li; Zhang, Miao; Di, Zengfeng E-mail: shijin.zhao@shu.edu.cn; Hu, Lijuan; Zhao, Shi-Jin E-mail: shijin.zhao@shu.edu.cn

    2014-09-21

    Taking the change of L-point conduction band valley degeneracy under strain into consideration, we investigate the effect of biaxially tensile strain (parallel to the (001), (110), and (111) planes) and uniaxially tensile strain (along the [001], [110], and [111] directions) on the electronic structure of Ge using density functional theory calculations. Our calculation shows that biaxial tension parallel to (001) is the most efficient way to transform Ge into a direct bandgap material among all tensile strains considered. [111]-tension is the best choice among all uniaxial approaches for an indirect- to direct-bandgap transition of Ge. The calculation results, which are further elaborated by bond-orbital approximation, provide a useful guidance on the optical applications of Ge through strain engineering.

  20. Enhanced electroluminescence from a free-standing tensilely strained germanium nanomembrane light-emitting diode

    NASA Astrophysics Data System (ADS)

    Jingming, Chen; Bin, Shu; Jibao, Wu; Linxi, Fan; Heming, Zhang; Huiyong, Hu; Rongxi, Xuan; Jianjun, Song

    2015-10-01

    Ge has become a promising material for Si-based optoelectronic integrated circuits (OEIC) due to its pseudo-direct bandgap. In this paper we achieved tensilely strained Ge free-standing nanomembrane (NM) light-emitting diode (LED), using silicon nitride thin film with high stress. The tensile stress in the Ge layer can be controlled by adjustable process parameters. An expected redshift of electroluminescence (EL) in Ge NM LED is observed at room temperature, which has been attributed to the shrinking of its direct bandgap relative to its indirect bandgap. An EL with dramatically increased intensity was observed around 1876 nm at a tensile strain of 1.92%, which demonstrates the direct-band recombination in tensilely strained Ge NM. Project supported by the Fundamental Research Funds for the Central University of China (No. 7214428001).

  1. Tuning quantum dot luminescence below the bulk band gap using tensile strain.

    PubMed

    Simmonds, Paul J; Yerino, Christopher D; Sun, Meng; Liang, Baolai; Huffaker, Diana L; Dorogan, Vitaliy G; Mazur, Yuriy; Salamo, Gregory; Lee, Minjoo Larry

    2013-06-25

    Self-assembled quantum dots (SAQDs) grown under biaxial tension could enable novel devices by taking advantage of the strong band gap reduction induced by tensile strain. Tensile SAQDs with low optical transition energies could find application in the technologically important area of mid-infrared optoelectronics. In the case of Ge, biaxial tension can even cause a highly desirable crossover from an indirect- to a direct-gap band structure. However, the inability to grow tensile SAQDs without dislocations has impeded progress in these directions. In this article, we demonstrate a method to grow dislocation-free, tensile SAQDs by employing the unique strain relief mechanisms of (110)-oriented surfaces. As a model system, we show that tensile GaAs SAQDs form spontaneously, controllably, and without dislocations on InAlAs(110) surfaces. The tensile strain reduces the band gap in GaAs SAQDs by ~40%, leading to robust type-I quantum confinement and photoluminescence at energies lower than that of bulk GaAs. This method can be extended to other zinc blende and diamond cubic materials to form novel optoelectronic devices based on tensile SAQDs. PMID:23701255

  2. Tensile strain-induced magnetism transition in multilayer graphene with excess electrons: Stability of the edge-quantum well

    SciTech Connect

    Yang, Lei; Diao, Dongfeng

    2015-12-15

    The stability of edge-quantum well-induced strong magnetism of multilayer armchair graphene nanoribbon (AGNR) with excess electrons was investigated under applied tensile strain by density functional theory (DFT) calculations. The results indicated that: (1) The strain along the armchair edge direction led to a transition of the multilayer AGNRs from ferromagnetic state to nonmagnetic state when the strain increased to a critical value; (2) The strain induced bond length changes reduced the stability of the edge-quantum well in terms of the reduction of the electrons capturing capacity; and (3) The spin splitting of the energy bands near the Fermi level reduced with the increase of the strain, resulting in the decrease of the spin moment. This finding suggests that the magnetic properties of graphene have strong dependence on its strain states, which is crucial to the design of graphene-based magnetic devices.

  3. Mechanical characterization of sub-100-nm-thick Au thin films by electrostatically actuated tensile testing with several strain rates

    NASA Astrophysics Data System (ADS)

    Oh, Hyun-Jin; Kawase, Shinya; Hanasaki, Itsuo; Isono, Yoshitada

    2014-02-01

    We have developed the tensile testing device based on MEMS technology and applied it to the Au thin films with thickness in the sub-100-nm regime. The specimen was fabricated by thermal deposition and sputtering processes in the course of device fabrication. This technique of device fabrication in combination with the specimen realizes the precise loading direction without preloading before tensile tests. The loads were applied electrostatically by the comb-drive actuator. The obtained Young’s modulus was 28 ± 3 GPa and was insensitive to the strain rate. The 0.2% yield strength was in the range from 192 to 519 MPa with a trend of decrease with decreasing strain rate in the range from 5 × 10-5 to 5 × 10-2 s-1.

  4. Measurement of lacunar bone strains and crack formation during tensile loading by digital volume correlation of second harmonic generation images.

    PubMed

    Wentzell, Scott; Nesbitt, Robert Sterling; Macione, James; Kotha, Shiva

    2016-07-01

    The maintenance of healthy bone tissue depends upon the ability of osteocytes to respond to mechanical cues on the cellular level. The combination of digital volume correlation and second harmonic generation microscopy offers the opportunity to investigate the mechanical microenvironment of intact bone on the scale of individual osteocytes. Adult human femurs were imaged under tensile loads of 5 and 15MPa and volumes of approximately 492×429×31μm(3) were analyzed, along with an image of a bone microcrack under the same loading conditions. Principal strains were significantly higher in three-dimensional digital volume correlation when compared to two-dimensional digital image correlation. The average maximum principal strain magnitude was 5.06-fold greater than the applied global strain, with peak strains of up to 23.14-fold over global strains measured at the borders of osteocyte lacunae. Finally, a microcrack that initiated at an osteocyte lacunae had its greatest tensile strain magnitudes at the crack expansion front in the direction of a second lacunae, but strain at the crack border was reduced to background strain magnitudes upon breaching the second lacunae. This serveed to demonstrate the role of lacunae in initiating, mediating and terminating microcrack growth. PMID:26807766

  5. Strain rate effects on tensile strength of iron green bodies

    NASA Astrophysics Data System (ADS)

    Nishida, Masahiro; Kuroyanagi, Yuki; Häggblad, Hans-Åke; Jonsén, Pär; Gustafsson, Gustaf

    2015-09-01

    Impact tensile strength of iron green bodies with densities of 7.2 and 7.4 g/cm3 was examined by Brazilian test using the split-Hopkinson pressure bar (Kolsky bar) method. The powder material used for the experiments was a press-ready premix containing Distaloy AE, graphite, and lubricant. During dynamic compression, the failure behavior of specimens was observed using a high-speed video camera. The failure stress and failure behavior of dynamic compressive tests were compared with those of static compressive tests.

  6. Tensile behaviour of geopolymer-based materials under medium and high strain rates

    NASA Astrophysics Data System (ADS)

    Menna, Costantino; Asprone, Domenico; Forni, Daniele; Roviello, Giuseppina; Ricciotti, Laura; Ferone, Claudio; Bozza, Anna; Prota, Andrea; Cadoni, Ezio

    2015-09-01

    Geopolymers are a promising class of inorganic materials typically obtained from an alluminosilicate source and an alkaline solution, and characterized by an amorphous 3-D framework structure. These materials are particularly attractive for the construction industry due to mechanical and environmental advantages they exhibit compared to conventional systems. Indeed, geopolymer-based concretes represent a challenge for the large scale uses of such a binder material and many research studies currently focus on this topic. However, the behaviour of geopolymers under high dynamic loads is rarely investigated, even though it is of a fundamental concern for the integrity/vulnerability assessment under extreme dynamic events. The present study aims to investigate the effect of high dynamic loading conditions on the tensile behaviour of different geopolymer formulations. The dynamic tests were performed under different strain rates by using a Hydro-pneumatic machine and a modified Hopkinson bar at the DynaMat laboratory of the University of Applied Sciences of Southern Switzerland. The results are processed in terms of stress-strain relationships and strength dynamic increase factor at different strain-rate levels. The dynamic increase factor was also compared with CEB recommendations. The experimental outcomes can be used to assess the constitutive laws of geopolymers under dynamic load conditions and implemented into analytical models.

  7. Dependence of electronic properties of germanium on the in-plane biaxial tensile strains

    NASA Astrophysics Data System (ADS)

    Yang, C. H.; Yu, Z. Y.; Liu, Y. M.; Lu, P. F.; Gao, T.; Li, M.; Manzoor, S.

    2013-10-01

    The hybrid HSE06 functional with the spin-orbit coupling effects is used to calculate the habituation of the electronic properties of Ge on the (0 0 1), (1 1 1), (1 0 1) in-plane biaxial tensile strains (IPBTSs). Our motivation is to explore the nature of electronic properties of tensile-strained Ge on different substrate orientations. The calculated results demonstrate that one of the most effective and practical approaches for transforming Ge into a direct transition semiconductor is to introduce (0 0 1) IPBTS to Ge. At 2.3% (0 0 1) IPBTS, Ge becomes a direct bandgap semiconductor with 0.53 eV band gap, in good agreement with the previous theoretical and experimental results. We find that the (1 1 1) and (1 0 1) IPBTSs are not efficient since the shear strain and inner displacement of atoms introduced by them quickly decrease the indirect gap of Ge. By investigating the dependence of valence band spin-orbit splitting on strain, we prove that the dependency relationship and the coupled ways between the valence-band states of tensile-strained Ge are closely related to the symmetry of strain tensor, i.e., the symmetry of the substrate orientation. The first- and second-order coefficients describing the dependence of indirect gap, direct gap, the valence band spin-orbit coupling splitting, and heavy-hole-light-hole splitting of Ge on IPBTSs have been obtained by the least squares polynomial fitting. These coefficients are significant to quantitatively modulate the electronic properties of Ge by tensile strain and design tensile-strained Ge devices by semiconductor epitaxial technique.

  8. Impurity effects on high-temperature tensile ductility of iridium alloys at high strain rate

    SciTech Connect

    McKamey, C.G.; George, E.P.; Lee, E.H.; Ohriner, E.K.; Heatherly, L.; Cohron, J.W.

    1999-12-17

    The current study was undertaken to determine what effects, if any, larger amounts of certain impurities (Al,Cr,Fe,Ni, and Si) might have on the physical metallurgy and mechanical properties of the DOP-26 iridium alloy. This report summarizes the effects of these impurities on grain growth behavior and high-temperature high-strain-rate tensile ductility. Comparisons are made to the grain growth behavior and high-strain-rate tensile properties of the DOP-26 alloy without intentional impurity additions.

  9. Tensile-strained InxGa1-xP membranes for cavity optomechanics

    NASA Astrophysics Data System (ADS)

    Cole, Garrett D.; Yu, Pen-Li; Gärtner, Claus; Siquans, Karoline; Moghadas Nia, Ramon; Schmöle, Jonas; Hoelscher-Obermaier, Jason; Purdy, Thomas P.; Wieczorek, Witlef; Regal, Cindy A.; Aspelmeyer, Markus

    2014-05-01

    We investigate the optomechanical properties of tensile-strained ternary InxGa1-xP nanomembranes grown on GaAs. This material system combines the benefits of highly strained membranes, similar to those based on stoichiometric silicon nitride, with the unique properties of thin-film semiconductor single crystals, as previously demonstrated with suspended GaAs. Here, we employ lattice mismatch in epitaxial growth to impart an intrinsic tensile strain to a monocrystalline thin film (approximately 30 nm thick). These structures exhibit mechanical quality factors of 2 × 106 or beyond at room temperature and 17 K for eigenfrequencies up to 1 MHz, yielding Q × f products of 2 × 1012 Hz for a tensile stress of ˜170 MPa. Incorporating such membranes in a high-finesse Fabry-Perot cavity, we extract an upper limit to the total optical loss (including both absorption and scatter) of 40 ppm at 1064 nm and room temperature. Further reductions of the In content of this alloy will enable tensile stress levels of 1 GPa, with the potential for a significant increase in the Q × f product, assuming no deterioration in the mechanical loss at this composition and strain level. This materials system is a promising candidate for the integration of strained semiconductor membrane structures with low-loss semiconductor mirrors and for realizing stacks of membranes for enhanced optomechanical coupling.

  10. 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.

  11. 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.

  12. Unusual Enhancement in Intrinsic Thermal Conductivity of Multilayer Graphene by Tensile Strains

    SciTech Connect

    Kuang, Youdi; Lindsay, Lucas R.; Huang, Baoling

    2015-01-01

    High basal plane thermal conductivity k of multi-layer graphene makes it promising for thermal management applications. Here we examine the effects of tensile strain on thermal transport in this system. Using a first principles Boltzmann-Peierls equation for phonon transport approach, we calculate the room-temperature in-plane lattice k of multi-layer graphene (up to four layers) and graphite under different isotropic tensile strains. The calculated in-plane k of graphite, finite mono-layer graphene and 3-layer graphene agree well with previous experiments. The dimensional transitions of the intrinsic k and the extent of the diffusive transport regime from mono-layer graphene to graphite are presented. We find a peak enhancement of intrinsic k for multi-layer graphene and graphite with increasing strain and the largest enhancement amplitude is about 40%. In contrast the calculated intrinsic k with tensile strain decreases for diamond and diverges for graphene, we show that the competition between the decreased mode heat capacities and the increased lifetimes of flexural phonons with increasing strain contribute to this k behavior. Similar k behavior is observed for 2-layer hexagonal boron nitride systems, suggesting that it is an inherent thermal transport property in multi-layer systems assembled of purely two dimensional atomic layers. This study provides insights into engineering k of multi-layer graphene and boron nitride by strain and into the nature of thermal transport in quasi-two-dimensional and highly anisotropic systems.

  13. Tensile strains give rise to strong size effects for thermal conductivities of silicene, germanene and stanene

    NASA Astrophysics Data System (ADS)

    Kuang, Y. D.; Lindsay, L.; Shi, S. Q.; Zheng, G. P.

    2016-02-01

    Based on first principles calculations and self-consistent solution of the linearized Boltzmann-Peierls equation for phonon transport approach within a three-phonon scattering framework, we characterize lattice thermal conductivities k of freestanding silicene, germanene and stanene under different isotropic tensile strains and temperatures. We find a strong size dependence of k for silicene with tensile strain, i.e., divergent k with increasing system size; however, the intrinsic room temperature k for unstrained silicene converges with system size to 19.34 W m-1 K-1 at 178 nm. The room temperature k of strained silicene becomes as large as that of bulk silicon at 84 μm, indicating the possibility of using strain in silicene to manipulate k for thermal management. The relative contribution to the intrinsic k from out-of-plane acoustic modes is largest for unstrained silicene, ~39% at room temperature. The single mode relaxation time approximation, which works reasonably well for bulk silicon, fails to appropriately describe phonon thermal transport in silicene, germanene and stanene within the temperature range considered. For large samples of silicene, k increases with tensile strain, peaks at ~7% strain and then decreases with further strain. In germanene and stanene, increasing strain hardens and stabilizes long wavelength out-of-plane acoustic phonons, and leads to similar k behaviors to those of silicene. These findings further our understanding of phonon dynamics in group-IV buckled monolayers and may guide transfer and fabrication techniques for these freestanding samples and engineering of k by size and strain for applications of thermal management and thermoelectricity.Based on first principles calculations and self-consistent solution of the linearized Boltzmann-Peierls equation for phonon transport approach within a three-phonon scattering framework, we characterize lattice thermal conductivities k of freestanding silicene, germanene and stanene under

  14. Localized strain measurements of the intervertebral disc annulus during biaxial tensile testing.

    PubMed

    Karakolis, Thomas; Callaghan, Jack P

    2015-01-01

    Both inter-lamellar and intra-lamellar failures of the annulus have been described as potential modes of disc herniation. Attempts to characterize initial lamellar failure of the annulus have involved tensile testing of small tissue samples. The purpose of this study was to evaluate a method of measuring local surface strains through image analysis of a tensile test conducted on an isolated sample of annular tissue in order to enhance future studies of intervertebral disc failure. An annulus tissue sample was biaxial strained to 10%. High-resolution images captured the tissue surface throughout testing. Three test conditions were evaluated: submerged, non-submerged and marker. Surface strains were calculated for the two non-marker conditions based on motion of virtual tracking points. Tracking algorithm parameters (grid resolution and template size) were varied to determine the effect on estimated strains. Accuracy of point tracking was assessed through a comparison of the non-marker conditions to a condition involving markers placed on tissue surface. Grid resolution had a larger effect on local strain than template size. Average local strain error ranged from 3% to 9.25% and 0.1% to 2.0%, for the non-submerged and submerged conditions, respectively. Local strain estimation has a relatively high potential for error. Submerging the tissue provided superior strain estimates. PMID:25145810

  15. Strain Rate Sensitivity of Epoxy Resin in Tensile and Shear Loading

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    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 strain rates 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. Strain rate has a significant effect on the response of both resins. In shear both resins show a ductile response with maximum stress that is increasing with strain rate. In tension a ductile response is observed at low strain rate (approx. 5x10(exp 5) /s), and brittle response is observed at the medium and high strain rates (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 effect of the hydrostatic component of the stress on the deformation.

  16. Dynamic tensile fracture of mortar at ultra-high strain-rates

    NASA Astrophysics Data System (ADS)

    Erzar, B.; Buzaud, E.; Chanal, P.-Y.

    2013-12-01

    During the lifetime of a structure, concrete and mortar may be exposed to highly dynamic loadings, such as impact or explosion. The dynamic fracture at high loading rates needs to be well understood to allow an accurate modeling of this kind of event. In this work, a pulsed-power generator has been employed to conduct spalling tests on mortar samples at strain-rates ranging from 2 × 104 to 4 × 104 s-1. The ramp loading allowed identifying the strain-rate anytime during the test. A power law has been proposed to fit properly the rate-sensitivity of tensile strength of this cementitious material over a wide range of strain-rate. Moreover, a specimen has been recovered damaged but unbroken. Micro-computed tomography has been employed to study the characteristics of the damage pattern provoked by the dynamic tensile loading.

  17. Dynamic tensile fracture of mortar at ultra-high strain-rates

    SciTech Connect

    Erzar, B. Buzaud, E.; Chanal, P.-Y.

    2013-12-28

    During the lifetime of a structure, concrete and mortar may be exposed to highly dynamic loadings, such as impact or explosion. The dynamic fracture at high loading rates needs to be well understood to allow an accurate modeling of this kind of event. In this work, a pulsed-power generator has been employed to conduct spalling tests on mortar samples at strain-rates ranging from 2 × 10{sup 4} to 4 × 10{sup 4} s{sup −1}. The ramp loading allowed identifying the strain-rate anytime during the test. A power law has been proposed to fit properly the rate-sensitivity of tensile strength of this cementitious material over a wide range of strain-rate. Moreover, a specimen has been recovered damaged but unbroken. Micro-computed tomography has been employed to study the characteristics of the damage pattern provoked by the dynamic tensile loading.

  18. Radiative and non-radiative recombinations in tensile strained Ge microstrips: Photoluminescence experiments and modeling

    SciTech Connect

    Virgilio, M.; Schroeder, T.; Yamamoto, Y.; Capellini, G.

    2015-12-21

    Tensile germanium microstrips are candidate as gain material in Si-based light emitting devices due to the beneficial effect of the strain field on the radiative recombination rate. In this work, we thoroughly investigate their radiative recombination spectra by means of micro-photoluminescence experiments at different temperatures and excitation powers carried out on samples featuring different tensile strain values. For sake of comparison, bulk Ge(001) photoluminescence is also discussed. The experimental findings are interpreted in light of a numerical modeling based on a multi-valley effective mass approach, taking in to account the depth dependence of the photo-induced carrier density and of the self-absorption effect. The theoretical modeling allowed us to quantitatively describe the observed increase of the photoluminescence intensity for increasing values of strain, excitation power, and temperature. The temperature dependence of the non-radiative recombination time in this material has been inferred thanks to the model calibration procedure.

  19. Cyclic Tensile Strain Induces Tenogenic Differentiation of Tendon-Derived Stem Cells in Bioreactor Culture.

    PubMed

    Xu, Yuan; Wang, Qiang; Li, Yudong; Gan, Yibo; Li, Pei; Li, Songtao; Zhou, Yue; Zhou, Qiang

    2015-01-01

    Different loading regimens of cyclic tensile strain impose different effects on cell proliferation and tenogenic differentiation of TDSCs in three-dimensional (3D) culture in vitro, which has been little reported in previous literatures. In this study we assessed the efficacy of TDSCs in a poly(L-lactide-co-ε-caprolactone)/collagen (P(LLA-CL)/Col) scaffold under mechanical stimulation in the custom-designed 3D tensile bioreactor, which revealed that cyclic tensile strain with different frequencies (0.3 Hz, 0.5 Hz, and 1.0 Hz) and amplitudes (2%, 4%, and 8%) had no influence on TDSC viability, while it had different effects on the proliferation and the expression of type I collagen, tenascin-C, tenomodulin, and scleraxis of TDSCs, which was most obvious at 0.5 Hz frequency with the same amplitude and at 4% amplitude with the same frequency. Moreover, signaling pathway from microarray analysis revealed that reduced extracellular matrix (ECM) receptor interaction signaling initiated the tendon genius switch. Cyclic tensile strain highly upregulated genes encoding regulators of NPM1 and COPS5 transcriptional activities as well as MYC related transcriptional factors, which contributed to cell proliferation and differentiation. In particular, the transcriptome analysis provided certain new insights on the molecular and signaling networks for TDSCs loaded in these conditions. PMID:26229962

  20. Tensile strains give rise to strong size effects for thermal conductivities of silicene, germanene and stanene

    DOE PAGESBeta

    Kuang, Youdi D.; Lindsay, Lucas R.; Shi, Sanqiang Q.; Zhen, Guangping P.

    2016-01-11

    Based on first principles calculations and self-consistent solution of linearized Boltzmann-Peierls equation for phonon transport approach within a three-phonon scattering framework, we characterize lattice thermal conductivities k of freestanding silicene, germanene and stanene under different isotropic tensile strains and temperatures. We find a strong size dependence of k for silicene with tensile strain, i.e., divergent k with increasing system size, in contrast, the intrinsic room temperature k for unstrained silicene converges with system size to 19.34 W/m–1 K–1 by 178 nm. The room temperature k of strained silicene becomes as large as that of bulk silicon by 84 m, indicatingmore » the possibility of using strain in silicene to manipulate k for thermal management. The relative contribution to the intrinsic k from out-of-plane acoustic modes is largest for unstrained silicene, –39% at room temperature. The single mode relaxation time approximation, which works reasonably well for bulk silicon, fails to appropriately describe phonon thermal transport in silicene, germanene and stanene within the temperature range considered. For large samples of silicene, k increases with tensile strain, peaks at –7% strain and then decreases with further strain. In germanene and stanene increasing strain hardens and stabilizes long wavelength out-of-plane acoustic phonons, and leads to similar k behaviors to those of silicene. As a result, these findings further our understanding of phonon dynamics in group-IV buckled monolayers and may guide transfer and fabrication techniques of these freestanding samples and engineering k by size and strain for applications of thermal management and thermoelectricity.« less

  1. Tensile strains give rise to strong size effects for thermal conductivities of silicene, germanene and stanene.

    PubMed

    Kuang, Y D; Lindsay, L; Shi, S Q; Zheng, G P

    2016-02-14

    Based on first principles calculations and self-consistent solution of the linearized Boltzmann-Peierls equation for phonon transport approach within a three-phonon scattering framework, we characterize lattice thermal conductivities k of freestanding silicene, germanene and stanene under different isotropic tensile strains and temperatures. We find a strong size dependence of k for silicene with tensile strain, i.e., divergent k with increasing system size; however, the intrinsic room temperature k for unstrained silicene converges with system size to 19.34 W m(-1) K(-1) at 178 nm. The room temperature k of strained silicene becomes as large as that of bulk silicon at 84 μm, indicating the possibility of using strain in silicene to manipulate k for thermal management. The relative contribution to the intrinsic k from out-of-plane acoustic modes is largest for unstrained silicene, ∼39% at room temperature. The single mode relaxation time approximation, which works reasonably well for bulk silicon, fails to appropriately describe phonon thermal transport in silicene, germanene and stanene within the temperature range considered. For large samples of silicene, k increases with tensile strain, peaks at ∼7% strain and then decreases with further strain. In germanene and stanene, increasing strain hardens and stabilizes long wavelength out-of-plane acoustic phonons, and leads to similar k behaviors to those of silicene. These findings further our understanding of phonon dynamics in group-IV buckled monolayers and may guide transfer and fabrication techniques for these freestanding samples and engineering of k by size and strain for applications of thermal management and thermoelectricity. PMID:26815838

  2. Investigation of high elastoplastic straining of shells of revolution under complex tensile and torque loading

    NASA Astrophysics Data System (ADS)

    Artem'eva, A. A.; Bazhenov, V. G.; Zhegalov, D. V.; Kazakov, D. A.; Nagornykh, E. V.

    2015-11-01

    A method of the numerical solution of nonlinear unsteady problems of axisymmetric elastoplastic straining of shells of revolution with allowance for torque loading at high strains is proposed. The method is based on the geometrically nonlinear theory of the Timoshenko shells and the plasticity theory with due allowance for combined isotropic and kinematic hardening. The problem is solved with the use of the variational difference method. Results of numerical and experimental investigations of elastoplastic straining of cylindrical shells under proportional and sequential kinematic tensile and torque loading are reported.

  3. Characterization of Optical Fiber Strength Under Applied Tensile Stress and Bending Stress

    SciTech Connect

    P.E. Klingsporn

    2011-08-01

    Various types of tensile testing and bend radius tests were conducted on silica core/silica cladding optical fiber of different diameters with different protective buffer coatings, fabricated by different fiber manufacturers. The tensile tests were conducted to determine not only the average fiber strengths at failure, but also the distribution in fracture strengths, as well as the influence of buffer coating on fracture strength. The times-to-failure of fiber subjected to constant applied bending stresses of various magnitudes were measured to provide a database from which failure times of 20 years or more, and the corresponding minimum bend radius, could be extrapolated in a statistically meaningful way. The overall study was done to provide an understanding of optical fiber strength in tensile loading and in applied bending stress as related to applications of optical fiber in various potential coizfgurations for weapons and enhanced surveillance campaigns.

  4. Bulk metallic glass composite with good tensile ductility, high strength and large elastic strain limit

    PubMed Central

    Wu, Fu-Fa; Chan, K. C.; Jiang, Song-Shan; Chen, Shun-Hua; Wang, Gang

    2014-01-01

    Bulk metallic glasses exhibit high strength and large elastic strain limit but have no tensile ductility. However, bulk metallic glass composites reinforced by in-situ dendrites possess significantly improved toughness but at the expense of high strength and large elastic strain limit. Here, we report a bulk metallic glass composite with strong strain-hardening capability and large elastic strain limit. It was found that, by plastic predeformation, the bulk metallic glass composite can exhibit both a large elastic strain limit and high strength under tension. These unique elastic mechanical properties are attributed to the reversible B2↔B19′ phase transformation and the plastic-predeformation-induced complicated stress state in the metallic glass matrix and the second phase. These findings are significant for the design and application of bulk metallic glass composites with excellent mechanical properties. PMID:24931632

  5. Intergranular Strain Evolution in Titanium During Tensile Loading: Neutron Diffraction and Polycrystalline Model

    NASA Astrophysics Data System (ADS)

    Gloaguen, David; Oum, Guy; Legrand, Vincent; Fajoui, Jamal; Moya, Marie-José; Pirling, Thilo; Kockelmann, Winfried

    2015-11-01

    Intergranular strains due to tensile plastic deformation were investigated in a commercially pure Ti. Neutron diffraction has been used to characterize the evolution of residual elastic strain in grains with different crystallographic orientations. Experimental data have been obtained for the macroscopic stress-strain curve and the intergranular strain evolution in the longitudinal and transverse direction relative to the uniaxial loading axis. The elasto-plastic self-consistent (EPSC) approach was used to model the deformation behavior of the studied material. Comparison between the neutron measurements and the model predictions shows that in most cases the EPSC approach can predict the lattice strain evolution and capture the plastic anisotropy observed in the experiments.

  6. Computational Simulation of the High Strain Rate Tensile Response of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.

    2002-01-01

    A research program is underway to develop strain rate dependent deformation and failure models for the analysis of polymer matrix composites subject to high strain rate impact loads. Under these types of loading conditions, the material response can be highly strain rate 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 effective mechanical and thermal response of the composite. To verify the analytical model, tensile stress-strain curves are predicted for a representative composite over strain rates 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. Effective elastic and thermal constants are predicted for another composite, and compared to finite element results.

  7. Experimental Study on Tensile Behavior of Carbon Fiber and Carbon Fiber Reinforced Aluminum at Different Strain Rate

    NASA Astrophysics Data System (ADS)

    Zhou, Yuanxin; Wang, Ying; Jeelani, Shaik; Xia, Yuanming

    2007-01-01

    In this study, dynamic and quasi-static tensile behaviors of carbon fiber and unidirectional carbon fiber reinforced aluminum composite have been investigated. The complete stress strain curves of fiber bundles and the composite at different strain rates were obtained. The experimental results show that carbon fiber is a strain rate insensitive material, but the tensile strength and critical strain of the Cf/Al composite increased with increasing of strain rate because of the strain rate strengthening effect of aluminum matrix. Based on experimental results, a fiber bundles model has been combined with Weibull strength distribution function to establish a one-dimensional damage constitutive equation for the Cf/Al composite.

  8. Direct-bandgap light-emitting germanium in tensilely strained nanomembranes

    PubMed Central

    Sánchez-Pérez, Jose R.; Boztug, Cicek; Chen, Feng; Sudradjat, Faisal F.; Paskiewicz, Deborah M.; Jacobson, RB; Lagally, Max G.; Paiella, Roberto

    2011-01-01

    Silicon, germanium, and related alloys, which provide the leading materials platform of electronics, are extremely inefficient light emitters because of the indirect nature of their fundamental energy bandgap. This basic materials property has so far hindered the development of group-IV photonic active devices, including diode lasers, thereby significantly limiting our ability to integrate electronic and photonic functionalities at the chip level. Here we show that Ge nanomembranes (i.e., single-crystal sheets no more than a few tens of nanometers thick) can be used to overcome this materials limitation. Theoretical studies have predicted that tensile strain in Ge lowers the direct energy bandgap relative to the indirect one. We demonstrate that mechanically stressed nanomembranes allow for the introduction of sufficient biaxial tensile strain to transform Ge into a direct-bandgap material with strongly enhanced light-emission efficiency, capable of supporting population inversion as required for providing optical gain. PMID:22084063

  9. Smooth-particle applied mechanics: Conservation of angular momentum with tensile stability and velocity averaging.

    PubMed

    Hoover, Wm G; Hoover, Carol G; Merritt, Elizabeth C

    2004-01-01

    Smooth-particle applied mechanics (SPAM) provides several approaches to approximate solutions of the continuum equations for both fluids and solids. Though many of the usual formulations conserve mass, (linear) momentum, and energy, the angular momentum is typically not conserved by SPAM. A second difficulty with the usual formulations is that tensile stress states often exhibit an exponentially fast high-frequency short-wavelength instability, "tensile instability." We discuss these twin defects of SPAM and illustrate them for a rotating elastic body. We formulate ways to conserve angular momentum while at the same time delaying the symptoms of tensile instability for many sound-traversal times. These ideas should prove useful in more general situations. PMID:14995750

  10. Unusual Enhancement in Intrinsic Thermal Conductivity of Multilayer Graphene by Tensile Strains

    DOE PAGESBeta

    Kuang, Youdi; Lindsay, Lucas R.; Huang, Baoling

    2015-01-01

    High basal plane thermal conductivity k of multi-layer graphene makes it promising for thermal management applications. Here we examine the effects of tensile strain on thermal transport in this system. Using a first principles Boltzmann-Peierls equation for phonon transport approach, we calculate the room-temperature in-plane lattice k of multi-layer graphene (up to four layers) and graphite under different isotropic tensile strains. The calculated in-plane k of graphite, finite mono-layer graphene and 3-layer graphene agree well with previous experiments. The dimensional transitions of the intrinsic k and the extent of the diffusive transport regime from mono-layer graphene to graphite are presented.more » We find a peak enhancement of intrinsic k for multi-layer graphene and graphite with increasing strain and the largest enhancement amplitude is about 40%. In contrast the calculated intrinsic k with tensile strain decreases for diamond and diverges for graphene, we show that the competition between the decreased mode heat capacities and the increased lifetimes of flexural phonons with increasing strain contribute to this k behavior. Similar k behavior is observed for 2-layer hexagonal boron nitride systems, suggesting that it is an inherent thermal transport property in multi-layer systems assembled of purely two dimensional atomic layers. This study provides insights into engineering k of multi-layer graphene and boron nitride by strain and into the nature of thermal transport in quasi-two-dimensional and highly anisotropic systems.« less

  11. Regulation of matrix metalloproteinase expression by dynamic tensile strain in rat fibrochondrocytes

    PubMed Central

    Deschner, J.; Rath-Deschner, B.; Agarwal, S.

    2016-01-01

    Summary Objective We sought to determine the molecular basis for the anticatabolic effects of mechanical signals on fibrocartilage cells by studying the expression of a variety of matrix metalloproteinases (MMPs). Furthermore, we examined whether the effects of biomechanical strain on MMP gene expression are sustained. Methods Fibrochondrocytes from temporomandibular joint (TMJ) discs were exposed to dynamic tensile strain for various time intervals in the presence of interleukin (IL)-1β. The regulation of the messenger RNA (mRNA) expression and synthesis of MMPs and tissue inhibitors of MMPs (TIMPs) were examined by end-point and real-time reverse transcriptase-polymerase chain reaction (RT-PCR) as well as Western blot analysis. Results Fibrochondrocytes expressed mRNA for MMP-2, -3, -7, -8, -9, -11, -13, -14, -16, -17, and -19 as well as TIMP-1, -2, and -3, IL-1β induced a significant (P <0.05) upregulation of mRNA for MMP-3, -7, -8, -9, -13, -16, -17, and -19. The IL-1β-stimulated upregulation of these MMPs was significantly (P <0.05) abrogated by dynamic tensile strain. However, MMP-2, -11, -14, and TIMPs were not affected by either IL-1β or tensile strain. Biomechanical strain also inhibited the IL-1β-stimulated protein synthesis of MMP-3, -7, -8, -9, -13, -16, and -17. Application of mechanical strain for various time intervals during a 24-h incubation with IL-1β showed that the suppressive effects of mechanical signals are sustained. Conclusions The data provide evidence that biomechanical signals can downregulate the catabolic activity of fibrocartilage cells in an inflammatory environment by inhibiting the expression of a variety of MMPs. Furthermore, the matrix-protective effects of biomechanical signals are sustained even in an inflammatory environment. PMID:16290189

  12. Flexible nanomembrane photonic-crystal cavities for tensilely strained-germanium light emission

    NASA Astrophysics Data System (ADS)

    Yin, Jian; Cui, Xiaorui; Wang, Xiaowei; Sookchoo, Pornsatit; Lagally, Max G.; Paiella, Roberto

    2016-06-01

    Flexible photonic-crystal cavities in the form of Si-column arrays embedded in polymeric films are developed on Ge nanomembranes using direct membrane assembly. The resulting devices can sustain large biaxial tensile strain under mechanical stress, as a way to enhance the Ge radiative efficiency. Pronounced emission peaks associated with photonic-crystal cavity resonances are observed in photoluminescence measurements. These results show that ultrathin nanomembrane active layers can be effectively coupled to an optical cavity, while still preserving their mechanical flexibility. Thus, they are promising for the development of strain-enabled Ge lasers, and more generally uniquely flexible optoelectronic devices.

  13. Strain localization during tensile Hopkinson bar testing of commercially pure titanium and Ti6Al4V titanium alloy

    NASA Astrophysics Data System (ADS)

    Moćko, Wojciech; Kruszka, Leopold; Brodecki, Adam

    2015-09-01

    The goal of the analysis was to determine the strain localization for various specimen shapes (type A and type B according to PN-EN ISO 26203-1 standard) and different loading conditions, i.e. quasi- static and dynamic. Commercially pure titanium (Grade 2) and titanium alloy Ti6Al4V (Grade 5) were selected for the tests. Tensile loadings were applied out using servo-hydraulic testing machine and tensile Hopkinson bar with pre-tension. The results were recorded using ARAMIS system cameras and fast camera Phantom V1210, respectively at quasi-static and dynamic loading conditions. Further, specimens outline was determined on the basis of video data using TEMA MOTION software. The strain distribution on the specimen surface was estimated using digital image correlation method. The larger radius present in the specimen of type B in comparison to specimen of type A, results in slight increase of the elongation for commercially pure titanium at both quasi-static and dynamic loading conditions. However this effect disappears for Ti6Al4V alloy. The increase of the elongation corresponds to the stronger necking effect. Material softening due to increase of temperature induced by plastic work was observed at dynamic loading conditions. Moreover lower elongation at fracture point was found at high strain rates for both materials.

  14. Nonvolatile Three-Step Ferroelectric Switching in Tensile Strained BiFeO3 Thin Films

    NASA Astrophysics Data System (ADS)

    Lee, Jin Hong; Chu, Kanghyun; Kim, Kwang-Eun; Yang, Chan-Ho

    2014-03-01

    Misfit strain has been one of key control parameters to improve the magnetoelectric coupling between ferroelectricity and magnetism in multiferroic epitaxial thin films. Lately, it was discovered that a bulk-like phase of multiferroic bismuth ferrite (BiFeO3) , through compressive or tensile misfit strain, can be transformed into a highly-elongated tetragonal-like phase or an orthorhombic phase, respectively, thereby offering new chances into magnetoelectric applications. Although the heteroepitaxial misfit strains via (001) interfaces have been intensively studied, strain effects arising from the other directional interfaces such as (110) have not been studied much. In this talk, we present the uniaxial-tensile-strain effects on the (110) oriented BiFeO3 thin films. Our detailed piezoresponse force microscopy analysis, X-ray reciprocal space mapping, and Landau free energy modeling give strong evidences of electrically switchable, non-volatile, three out-of-plane polarization states. These findings provide useful implications for a new type of magnetoelectric devices based on phase competition.

  15. Influence of the tensile strain on CH4 dissociation on Cu(1 0 0) surface: A theoretical study

    NASA Astrophysics Data System (ADS)

    He, Feng; Li, Kai; Xie, Guangyou; Wang, Ying; Jiao, Menggai; Tang, Hao; Wu, Zhijian

    2016-01-01

    Tensile strain is widespread on the catalyst surface due to the lattice mismatch between the catalyst and substrate, such as Cu/MgO in this work. Thus, it is important to investigate the influence of tensile strain on the catalytic properties. In this study, we have investigated the CH4 dissociation on Cu(1 0 0) surface by considering the tensile strain. Our results showed that compared with the unstrained Cu(1 0 0) surface, the most stable sites for dissociation species CHx (x = 0-3) and H adsorption on strained surface remain unchanged. The surface strain strengthens CHx (x = 0-3) adsorption, while weakens H adsorption. The elementary reaction for CH4 dissociation with the largest electronic energy barrier changes from CH → C + H on the unstrained surface to CH4 → CH3 + H on the strained surface (for strain equal to and larger than 3%), in agreement with the experimental observation that CH4 dissociation into CH3 and H is the most difficult reaction. The tensile strain accelerates C migration while has no obvious influence for C polymerization. Both DFT calculations and microkinetic model demonstrated that the strain hinders the CH4 dissociation process on Cu(1 0 0) surface. CH4 dissociation rate depends sensitively on the magnitude of the surface tensile strain.

  16. Tensile and compressive stress-strain behavior of heat treated boron-aluminum

    NASA Technical Reports Server (NTRS)

    Kennedy, J. M.; Tenney, D. R.; Herakovich, C. T.

    1978-01-01

    An experimental study was conducted to assess the effects of heat treatment and cyclic mechanical loading on the tensile and compressive stress-strain behavior of six boron-aluminum composites having different laminate orientations and being subjected to different heat treatments. The heat treatments were as-fabricated, T6, and T6N consisting of T6 treatment followed by cryogenic quench in liquid nitrogen prior to testing. All laminates were tested in monotonic and cyclic compression, while the tensile-test data are taken from the literature for comparison purposes. It is shown that the linear elastic range of the T6- and T6N-condition specimens is larger than that of the as-fabricated specimens, and that cyclic loading in tension or compression strain hardens the specimens and extends the linear elastic range. For laminates containing 0-deg plies, the stress-strain behavior upon unloading is found to be nonlinear, whereas the other laminates exhibit a linear behavior upon unloading. Specimens in the T6 and T6N conditions show higher strain hardening than the as-fabricated specimens.

  17. Electro-mechanical Properties of Carbon Nanotubes: Effect of Small Tensile and Torsional Strains

    NASA Technical Reports Server (NTRS)

    Anantram, M. P.; Yang, Liu; Han, Jie; Liu, J. P.; Saini, Subhash (Technical Monitor)

    1999-01-01

    We present a simple picture to calculate the bandgap ($E_g$) of carbon nanotubes (CNT) in the presence of uniform torsional and tensile strain ($\\sigma$). We find that under tensile strain, $ absolute value of dE_g/d\\sigma$ of zig-zag tubes is approximately equal to $3t_0$, where $t_0$ is the hopping parameter. Further, $ absolute value of dE_g/d\\sigma$ decreases as the chirality changes to armchair, where it takes the value zero. The sign of $dE_g/d\\sigma$ follows the $(N_x-N_y) *mod 3$(equal to - 1, 0 and +1) rule. In contrast to the above, we show that under torsional strain, $absolute value of dE_g/d\\sigma$ of armchair tubes is approximately equal to $3t_0$ and continually decreases as the chirality changes to zig-zag, where is takes a small value. The sign of $dE_g/d\\sigma$ again follows the $(N_x-N_y)*mod 3$ rule. Finally, we predict a change in the sign of $dE_g/d\\sigma$ as function of strain, corresponding to a change in the value of $q$ that corresponds to the bandgap minimum.

  18. Tensile Strain Switched Ferromagnetism in Layered NbS2 and NbSe2

    SciTech Connect

    Zhou, Yungang; Wang, Zhiguo; Yang, Ping; Zu, Xiaotao; Yang, Li; Sun, Xin; Gao, Fei

    2012-11-01

    Developing approaches to effectively induce and control the magnetic states is critical to the use of magnetic nanostructures in quantum information devices but is still challenging. Here we have demonstrated, by employing the density functional theory calculations, an existence of infinite magnetic sheets with structural integrity and magnetic homogeneity. Examination from a series of transition metal dichalcogenides shows that the biaxial tensile strained NbS2 and NbSe2 structures can be magnetized with a ferromagnetic character due to the competitive effects of through-bond interaction and through-space interaction. The estimated Curie temperatures (387 and 542 K under the 10% strain for NbS2 and NbSe2 structures, respectively) suggest that the unique ferromagnetic character can be achieved above room temperature. The self-exchange of population between 4d orbitals of Nb atom that leads to the exchange splitting is the mechanism behind the transition of the spin moment. The induced magnetic moments can be significantly enhanced by the tensile strain, even giving rise to half-metallic character with the strong spin polarization around the Fermi level. Given the recent progress that the desired strain can be achieved on two-dimensional nanostructures, such as graphene and BN layer in a controlled way, we believe that our calculated results are suitable for experimental verification and implementation opening a new path to explore the spintronics in pristine two-dimensional nanostructures.

  19. Influence of strain rate on the quasi-static tensile strength of Kevlar 29 narrow fabrics

    SciTech Connect

    Ericksen, R.H.

    1981-01-01

    Increasing the strain rate from 3 x 10/sup -4/ min/sup -1/ to 1.4 min/sup -1/ resulted in a 20% increase in fabric strength. Similar changes in strength with strain rate were obtained for warp yarns removed from the fabrics. Static and sliding loop yarn tests, and tests in which yarn was interwoven through wires, were used to determine effect of abrasion, bending and lateral compression as a function of strain rate. Results eliminated yarn damage by abrasion and demonstrated that unwoven yarn strength, in presence of bending or lateral compression, was dependent on strain rate. Yarn and fiber pullout tests showed that increasing strain rate caused a transition from stick-slip to smooth curves. Results suggested a mechanism whereby strain-rate dependent frictional behavior of Kevlar influences woven fabric strength. It appears that friction restrains highly loaded fibers in a fabric from adjusting their position to relieve stress concentrations. Yarn tensile strength is influenced by strain rate when the fiber arrangement has been altered by weaving or when bending or lateral compressive forces are also present.

  20. Electrothermal fracturing of tensile specimens

    NASA Technical Reports Server (NTRS)

    Blinn, H. O.; Hanks, J. G.; Perkins, H. P.

    1970-01-01

    Pulling device consisting of structural tube, connecting rod, spring-loaded nuts, loading rod, heating element, and three bulkheads fractures tensile specimens. Alternate heating and cooling increases tensile loading by increments until fracturing occurs. Load cell or strain gage, applied to pulling rod, determines forces applied.

  1. 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. PMID:19725697

  2. Heterogeneously-Grown Tunable Tensile Strained Germanium on Silicon for Photonic Devices.

    PubMed

    Clavel, Michael; Saladukha, Dzianis; Goley, Patrick S; Ochalski, Tomasz J; Murphy-Armando, Felipe; Bodnar, Robert J; Hudait, Mantu K

    2015-12-01

    The growth, structural and optical properties, and energy band alignments of tensile-strained germanium (ε-Ge) epilayers heterogeneously integrated on silicon (Si) were demonstrated for the first time. The tunable ε-Ge thin films were achieved using a composite linearly graded InxGa1-xAs/GaAs buffer architecture grown via solid source molecular beam epitaxy. High-resolution X-ray diffraction and micro-Raman spectroscopic analysis confirmed a pseudomorphic ε-Ge epitaxy whereby the degree of strain varied as a function of the In(x)Ga(1-x)As buffer indium alloy composition. Sharp heterointerfaces between each ε-Ge epilayer and the respective In(x)Ga(1-x)As strain template were confirmed by detailed strain analysis using cross-sectional transmission electron microscopy. Low-temperature microphotoluminescence measurements confirmed both direct and indirect bandgap radiative recombination between the Γ and L valleys of Ge to the light-hole valence band, with L-lh bandgaps of 0.68 and 0.65 eV demonstrated for the 0.82 ± 0.06% and 1.11 ± 0.03% strained Ge on Si, respectively. Type-I band alignments and valence band offsets of 0.27 and 0.29 eV for the ε-Ge/In(0.11)Ga(0.89)As (0.82%) and ε-Ge/In(0.17)Ga(0.83)As (1.11%) heterointerfaces, respectively, show promise for ε-Ge carrier confinement in future nanoscale optoelectronic devices. Therefore, the successful heterogeneous integration of tunable tensile-strained Ge on Si paves the way for the design and implementation of novel Ge-based photonic devices on the Si technology platform. PMID:26561963

  3. Effects of temperature and strain rate on the tensile behaviors of SIMP steel in static lead bismuth eutectic

    NASA Astrophysics Data System (ADS)

    Liu, Jian; Yan, Wei; Sha, Wei; Wang, Wei; Shan, Yiyin; Yang, Ke

    2016-05-01

    In order to assess the susceptibility of candidate structural materials to liquid metal embrittlement, this work investigated the tensile behaviors of ferritic-martensitic steel in static lead bismuth eutectic (LBE). The tensile tests were carried out in static lead bismuth eutectic under different temperatures and strain rates. Pronounced liquid metal embrittlement phenomenon is observed between 200 °C and 450 °C. Total elongation is reduced greatly due to the liquid metal embrittlement in LBE environment. The range of ductility trough is larger under slow strain rate tensile (SSRT) test.

  4. A modified Weibull model for tensile strength distribution of carbon nanotube fibers with strain rate and size effects

    NASA Astrophysics Data System (ADS)

    Sun, Gengzhi; Pang, John H. L.; Zhou, Jinyuan; Zhang, Yani; Zhan, Zhaoyao; Zheng, Lianxi

    2012-09-01

    Fundamental studies on the effects of strain rate and size on the distribution of tensile strength of carbon nanotube (CNT) fibers are reported in this paper. Experimental data show that the mechanical strength of CNT fibers increases from 0.2 to 0.8 GPa as the strain rate increases from 0.00001 to 0.1 (1/s). In addition, the influence of fiber diameter at low and high strain rate conditions was investigated further with statistical analysis. A modified Weibull distribution model for characterizing the tensile strength distribution of CNT fibers taking into account the effect of strain rate and fiber diameter is proposed.

  5. The effect of tensile hysteresis and contact resistance on the performance of strain-resistant elastic-conductive webbing.

    PubMed

    Shyr, Tien-Wei; Shie, Jing-Wen; Jhuang, Yan-Er

    2011-01-01

    To use e-textiles as a strain-resistance sensor they need to be both elastic and conductive. Three kinds of elastic-conductive webbings, including flat, tubular, and belt webbings, made of Lycra fiber and carbon coated polyamide fiber, were used in this study. The strain-resistance properties of the webbings were evaluated in stretch-recovery tests and measured within 30% strain. It was found that tensile hysteresis and contact resistance significantly influence the tensile elasticity and the resistance sensitivity of the webbings. The results showed that the webbing structure definitely contributes to the tensile hysteresis and contact resistance. The smaller the friction is among the yarns in the belt webbing, the smaller the tensile hysteresis loss. However the close proximity of the conductive yarns in flat and tubular webbings results in a lower contact resistance. PMID:22319376

  6. The Effect of Tensile Hysteresis and Contact Resistance on the Performance of Strain-Resistant Elastic-Conductive Webbing

    PubMed Central

    Shyr, Tien-Wei; Shie, Jing-Wen; Jhuang, Yan-Er

    2011-01-01

    To use e-textiles as a strain-resistance sensor they need to be both elastic and conductive. Three kinds of elastic-conductive webbings, including flat, tubular, and belt webbings, made of Lycra fiber and carbon coated polyamide fiber, were used in this study. The strain-resistance properties of the webbings were evaluated in stretch-recovery tests and measured within 30% strain. It was found that tensile hysteresis and contact resistance significantly influence the tensile elasticity and the resistance sensitivity of the webbings. The results showed that the webbing structure definitely contributes to the tensile hysteresis and contact resistance. The smaller the friction is among the yarns in the belt webbing, the smaller the tensile hysteresis loss. However the close proximity of the conductive yarns in flat and tubular webbings results in a lower contact resistance. PMID:22319376

  7. Transformation strain dependence on applied stress in equiatomic nickel-titanium alloys of powder-metallurgical origin

    SciTech Connect

    Ramon, P.

    1983-06-01

    The strain-temperature behavior of Ni-Ti samples upon martensitic phase transformation was investigated as a function of applied uniaxial tensile and compressive stresses. The samples were cycled in temperature when they were held in grips, which permitted a deadweight axial stress to be applied. It was found in the absence of an applied stress that the strains upon transformation were nearly isotropic. By contrast, as the uniaxial tensile stress was increased, the axial and circumferential strains became increasingly different, i.e., the axial strain corresponded to an expansion upon transformation on cooling and the circumferential strain to a contraction. The magnitudes of these strains increased progressively with increasing stress. Similar results were obtained for uniaxial compressive stresses, except that the axial strain corresponded to a contraction and the circumferential strain to an expansion upon transformation on cooling. The observation that the transformation strain increases with increasing applied stress is explained on the basis of a preferred activation model (PAM). The phenomenological theory of Wechsler-Lieberman and Read (WLR) is applied, and the semiaxes of the total distortion ellipsoid calculated. The calculated total distortions predict the saturation limit of phase transformation strains with increasing applied uniaxial tensile stress.

  8. The in vitro passive elastic response of chicken pectoralis muscle to applied tensile and compressive deformation.

    PubMed

    Mohammadkhah, Melika; Murphy, Paula; Simms, Ciaran K

    2016-09-01

    The mechanics of passive skeletal muscle are important in impact biomechanics, surgical simulation, and rehabilitation engineering. Existing data from porcine tissue has shown a significant tension/compression asymmetry, which is not captured by current constitutive modelling approaches using a single set of material parameters, and an adequate explanation for this effect remains elusive. In this paper, the passive elastic deformation properties of chicken pectoralis muscle are assessed for the first time, to provide deformation data on a skeletal muscle which is very different to porcine tissue. Uniaxial, quasi-static compression and tensile tests were performed on fresh chicken pectoralis muscle in the fibre and cross-fibre directions, and at 45° to the fibre direction. Results show that chicken muscle elastic behaviour is nonlinear and anisotropic. The tensile stress-stretch response is two orders of magnitude larger than in compression for all directions tested, which reflects the tension/compression asymmetry previously observed in porcine tissue. In compression the tissue is stiffest in the cross-fibre direction. However, tensile deformation applied at 45° gives the stiffest response, and this is different to previous findings relating to porcine tissue. Chicken muscle tissue is most compliant in the fibre direction for both tensile and compressive applied deformation. Generally, a small percentage of fluid exudation was observed in the compressive samples. In the future these data will be combined with microstructural analysis to assess the architectural basis for the tension/compression asymmetry now observed in two different species of skeletal muscle. PMID:27281164

  9. Stretching molecules under extreme tensile strain: density functional theory versus multireference methods

    NASA Astrophysics Data System (ADS)

    Kedziora, Gary; Barr, Stephen; Berry, Rajiv; Moller, James; Breitzman, Timothy

    A more refined understanding of how molecules behave under extreme tensile strain is desirable for modeling fracture initiation in polymers and other mecho-chemical studies. We investigated several quantum mechanical methods for use in multiscale models of highly strained polymers where bond breaking occurs. A small set of molecules and a protocol for stretching them were used as model test systems. The results from these tests using several functionals were compared with complete active space self-consistent field results. These test systems provide unique challenges for quantum mechanical models. Quantum mechanics is required for accurate bond breaking prediction because the results are dependent on the conformation and secondary electronic structure effects such as hyperconjugation. GGA methods with unrestricted solutions to the Kohn-Sham equations provide adequate results for our purposes even though there are some minor flaws based on the spin symmetry breaking.

  10. Grating-coupled mid-infrared light emission from tensilely strained germanium nanomembranes

    SciTech Connect

    Boztug, Cicek; Yin, Jian; Paiella, Roberto; Sánchez-Pérez, José R.; Lagally, Max G.

    2013-11-11

    Mechanically stressed nanomembranes are used to demonstrate mid-infrared interband light emission from Ge within the 2.1–2.5 μm atmospheric transmission window. Large biaxial tensile strain is introduced in these samples to convert Ge into a (near-) direct-bandgap semiconductor and to red-shift its luminescence. A diffractive array of Ge pillars is used to outcouple the long-wavelength interband radiation, which is otherwise primarily emitted in the sample plane. An order-of-magnitude strain-induced enhancement in radiative efficiency is also reported, together with the observation of luminescence signatures associated with photonic-crystal cavity modes. These results are promising for the development of silicon-compatible lasers for mid-infrared optoelectronics applications.

  11. Wideband model of a reflective tensile-strained bulk semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Connelly, M. J.

    2014-05-01

    Reflective semiconductor optical amplifiers (RSOAs) have shown promise for applications in WDM optical networks and in fiber ring mode-locked lasers. Polarization insensitive SOAs can be fabricated using tensile-strained bulk material and a rectangular cross section waveguide. The introduction of tensile strain can be used to compensate for the different confinement factors experienced by the waveguide TE and TM modes. There is a need for models that can be used to predict RSOA static characteristics such as the dependency of the signal gain on bias current and input optical power, the amplified spontaneous emission spectrum and noise figure. In this paper we extend our prior work on non-reflective SOAs to develop a static model that includes facet reflections. The model uses a detailed band structure description, which is used to determine the wavelength and carrier density dependency of the material gain and additive spontaneous emission. The model and includes a full geometrical description of the amplifier waveguide, including the input taper and the position dependency of the TE/TM confinement factors. The amplified signal and spontaneous emission are described by detailed travelling-wave equations and numerically solved in conjunction with a carrier density rate equation. The model uses material and geometric parameters for a commercially available RSOA. The versatility of the model is shown by several simulations that are used to predict the SOA operational characteristics as well as internal variables such as the amplified spontaneous emission and signal and the carrier density.

  12. Magnetism and Raman Spectroscopy of Pristine and Hydrogenated TaSe2 Monolayer tuned by Tensile and Pure Shear Strain

    NASA Astrophysics Data System (ADS)

    Chowdhury, Sugata; Simpson, Jeffrey; Einstein, T. L.; Walker, Angela R. Hight

    2D-materials with controllable optical, electronic and magnetic properties are desirable for novel nanodevices. Here we studied these properties for both pristine and hydrogenated TaSe2 (TaSe2-H) monolayer (ML) in the framework of DFT using the PAW method. We considered uniaxial and biaxial tensile strain, as well as shear strain along the basal planes in the range between 1% and 16%. Previous theoretical works (e.g.) considered only symmetrical biaxial tensile. Pristine ML is ferromagnetic for uniaxial tensile strain along ◯ or ŷ. For tensile strain in ŷ, the calculated magnetic moments of the Ta atoms are twice those for the same strain in ◯. Under pure shear strain (expansion along ŷ and compression along ◯), a pristine ML is ferromagnetic, but becomes non-magnetic when the strain directions are interchanged. Due to carrier-mediated double-exchange, the pristine ML is ferromagnetic when the Se-Ta-Se bond angle is < 82° and the ML thickness is < 3.25Å. We find that all Raman-active phonon modes show obvious red-shifting due to bond elongation and the E2 modes degeneracy is lifted as strain increases. For a TaSe2-H ML, the same trends were observed. Results show the ability to tune the properties of 2D-materials.

  13. Unusual Enhancement in Intrinsic Thermal Conductivity of Multilayer Graphene by Tensile Strains.

    PubMed

    Kuang, Youdi; Lindsay, Lucas; Huang, Baoling

    2015-09-01

    Using the Boltzmann-Peierls equation for phonon transport approach with the inputs of interatomic force constants from the self-consistent charge density functional tight binding method, we calculate the room-temperature in-plane lattice thermal conductivities k of multilayer graphene (up to four layers) and graphite under different isotropic tensile strains. The calculated in-plane k of graphite, finite monolayer graphene and 3-layer graphene agree well with previous experiments. For unstrained graphene systems, both the intrinsic k and the extent of the diffusive transport regime present a drastic dimensional transition in going from monolayer to 2-layer graphene and thereafter a gradual transition to the graphite limit. We find a peak enhancement of intrinsic k for multilayer graphene and graphite with increasing strain with the largest enhancement amplitude ∼40%. Competition between the decreased mode heat capacities and the increased lifetimes of flexural phonons with increasing strain contribute to this k behavior. Similar k behavior is observed for 2-layer hexagonal boron nitride systems. This study provides insights into engineering k of multilayer graphene and boron nitride by strain and into the nature of thermal transport in quasi-two-dimensional and highly anisotropic systems. PMID:26241731

  14. Cyclic Equibiaxial Tensile Strain Alters Gene Expression of Chondrocytes via Histone Deacetylase 4 Shuttling

    PubMed Central

    Chen, Chongwei; Wei, Xiaochun; Lv, Zhi; Sun, Xiaojuan; Wang, Shaowei; Zhang, Yang; Jiao, Qiang; Wang, Xiaohu; Li, Yongping; Wei, Lei

    2016-01-01

    Objectives This paper aims to investigate whether equibiaxial tensile strain alters chondrocyte gene expression via controlling subcellular localization of histone deacetylase 4 (HDAC4). Materials and Methods Murine chondrocytes transfected with GFP-HDAC4 were subjected to 3 h cyclic equibiaxial tensile strain (CTS, 6% strain at 0.25 Hz) by a Flexcell® FX-5000™ Tension System. Fluorescence microscope and western blot were used to observe subcellular location of HDAC4. The gene expression was analyzed by real-time RT-PCR. The concentration of Glycosaminoglycans in culture medium was quantified by bimethylmethylene blue dye; Collagen II protein was evaluated by western blot. Cells phenotype was identified by immunohistochemistry. Cell viability was evaluated by live-dead cell detect kit. Okadaic acid, an inhibitor of HDAC4 nuclear relocation, was used to further validate whether HDAC4 nuclear relocation plays a role in gene expression in response to tension stimulation. Results 87.5% of HDAC4 was located in the cytoplasm in chondrocytes under no loading condition, but it was relocated to the nucleus after CTS. RT-PCR analysis showed that levels of mRNA for aggrecan, collagen II, LK1 and SOX9 were all increased in chondrocytes subjected to CTS as compared to no loading control chondrocytes; in contrast, the levels of type X collagen, MMP-13, IHH and Runx2 gene expression were decreased in the chondrocytes subjected to CTS as compared to control chondrocytes. Meanwhile, CTS contributed to elevation of glycosaminoglycans and collagen II protein, but did not change collagen I production. When Okadaic acid blocked HDAC4 relocation from the cytoplasm to nucleus, the changes of the chondrocytes induced by CTS were abrogated. There was no chondrocyte dead detected in this study in response to CTS. Conclusions CTS is able to induce HDAC4 relocation from cytoplasm to nucleus. Thus, CTS alters chondrocytes gene expression in association with the relocation of HDAC4 induced

  15. Dynamic tensile stress-strain characteristics of carbon/epoxy laminated composites in through-thickness direction

    NASA Astrophysics Data System (ADS)

    Nakai, Kenji; Yokoyama, Takashi

    2015-09-01

    The effect of strain rate up to approximately ɛ˙ = 102/s on the tensile stress-strain properties of unidirectional and cross-ply carbon/epoxy laminated composites in the through-thickness direction is investigated. Waisted cylindrical specimens machined out of the laminated composites in the through-thickness direction are used in both static and dynamic tests. The dynamic tensile stress-strain curves up to fracture are determined using the split Hopkinson bar (SHB). The low and intermediate strain-rate tensile stress-strain relations up to fracture are measured on an Instron 5500R testing machine. It is demonstrated that the ultimate tensile strength and absorbed energy up to fracture increase significantly, while the fracture strain decreases slightly with increasing strain rate. Macro- and micro-scopic examinations reveal a marked difference in the fracture surfaces between the static and dynamic tension specimens.

  16. Biaxial Tensile Test of Cold Rolled IF Steel Sheet for Large Plastic Strain Range

    NASA Astrophysics Data System (ADS)

    Enatsu, Ryotaro; Kuwabara, Toshihiko

    2011-08-01

    Deformation behavior of cold rolled IF steel sheet (SPCE) under biaxial tension has been investigated for large plastic strain range over 15%. The test material was bent and TIG welded to form a tubular specimen with an outer diameter of 46.2 mm and wall thickness of 0.8 mm. The tubular specimens have been subjected to linear stress paths in the first quadrant of stress space with the use of a servo-controlled tension-internal pressure testing machine developed by one of the authors [T. Kuwabara, K. Yoshida, K. Narihara, S. Takahashi, Anisotropic plastic deformation of extruded aluminum alloy tube under axial forces and internal pressure, Int. J. Plasticity 21, 101-117 (2005)]. Moreover, biaxial tensile tests using a cruciform specimen have also been carried out to more precisely measure the deformation behavior for a small strain range following initial yielding. True stress-true plastic strain curves, contours of plastic work in stress space and the directions of plastic strain rates have been measured and compared with those calculated using selected yield functions: the von Mises, Hill's quadratic and Yld2000-2d [Barlat, F., Brem, J.C., Yoon, J.W., Chung, K., Dick, R.E., Lege, D.J., Pourboghrat, F., Choi, S.H., Chu, E., Plane stress yield function for aluminum alloy sheets—Part 1: Theory. Int. J. Plasticity 19, 1297-1319 (2003)]. The plastic deformation behavior up to a work equivalent plastic strain of ɛ0p = 0.19 has been successfully measured. It is found that the test material exhibits differential hardening and that the Yld2000-2d yield function with an exponent of six most closely predicts the contours of plastic work and the directions of plastic strain rates.

  17. In-situ observation of strain evolution in CP-Ti during uniaxial tensile loading

    NASA Astrophysics Data System (ADS)

    Bettles, C. J.; Gibson, M. A.; Stevenson, A. W.; Tomus, D.; Lynch, P. A.

    2010-07-01

    First results are presented for in-situ tensile loading experiments performed on the Powder Diffraction beamline at the Australian Synchrotron facility. For direct measurement of strain evolution, the beamline was fitted with a uniaxial tensile stage and a high-resolution CCD detector. Precise calibration of the experimental diffraction geometry, taking into account slight misalignment of the detector (pitch, roll, yaw), was achieved by simulation of the ring patterns recorded from the standard reference material LaB 6 (660). The material examined was a commercially pure titanium strip, which from prior electron microscopy studies, was found to have an average grain size of ˜20-30 μm. Tensile specimens conformed to ASTM E8, with a gauge length of 25 mm. To probe the bulk material properties all experiments were performed at 20 keV. In these preliminary experiments, measurement of the relative change in the interplanar lattice spacing was used to monitor the elastic response in seven crystallographic orientations during the loading cycle. To overcome problems encountered with grain size and associated discontinuous Debye-Scherrer ring patterns, two strategies were implemented to measure the Bragg peak (2 θB) positions. In cases where the radial integration routine provided inconsistent results for peak determination, a new approach based on determining the averaged sum of 2 θB positions from individual spots making up the ring pattern was utilised. Results obtained for the diffraction elastic modulus were found to be in agreement with predictions based on the single-crystal and Neerfield-Hill crystal coupling models.

  18. Tensile Stress-Strain Results for 304L and 316L Stainless-Steel Plate at Temperature

    SciTech Connect

    R. K. Blandford; D. K. Morton; S. D. Snow; T. E. Rahl

    2007-07-01

    The Idaho National Laboratory (INL) is conducting moderate strain rate (10 to 200 per second) research on stainless steel materials in support of the Department of Energy’s (DOE) National Spent Nuclear Fuel Program (NSNFP). For this research, strain rate effects are characterized by comparison to quasi-static tensile test results. Considerable tensile testing has been conducted resulting in the generation of a large amount of basic material data expressed as engineering and true stress-strain curves. The purpose of this paper is to present the results of quasi-static tensile testing of 304/304L and 316/316L stainless steels in order to add to the existing data pool for these materials and make the data more readily available to other researchers, engineers, and interested parties. Standard tensile testing of round specimens in accordance with ASTM procedure A 370-03a were conducted on 304L and 316L stainless-steel plate materials at temperatures ranging from -20 °F to 600 °F. Two plate thicknesses, eight material heats, and both base and weld metal were tested. Material yield strength, Young’s modulus, ultimate strength, ultimate strain, failure strength and failure strain were determined, engineering and true stress-strain curves to failure were developed, and comparisons to ASME Code minimums were made. The procedures used during testing and the typical results obtained are described in this paper.

  19. Modifications of system for elevated temperature tensile testing and stress-strain measurement of metal matrix composites

    SciTech Connect

    Diaz, J.O.

    1994-09-01

    Composites consisting of tungsten alloy wires in superalloy matrices are being studied because they offer the potential for increased strength compared to current materials used at temperatures up to a least 1093{degrees}C (2000{degrees}F). Previous research at the NASA Lewis Research Center and at other laboratories in the U.S., Europe, and Japan has demonstrated laboratory feasibility for fiber reinforced superalloys (FRS). The data for the mechanical and physical properties used to evaluate candidate materials is limited and a need exists for a more detailed and complete data base. The focus of this work was to develop a test procedure to provide a more complete FRS data base to quantitatively evaluate the composite`s potential for component applications. This paper will describe and discuss the equipment and procedures under development to obtain elevated temperature tensile stress-strain, strength and modulus data for the first generation of tungsten reinforced superalloy composite (TFRS) materials. Tensile stress-strain tests were conducted using a constant crosshead speed tensile testing machine and a modified load-strain measuring apparatus. Elevated temperature tensile tests were performed using a resistance wound commercial furnace capable of heating tests specimens up to 1093{degrees}C (2000{degrees}F). Tensile stress-strain data were obtained for hollow tubular stainless steel specimens serving as a prototype for future composite specimens.

  20. Modifications of system for elevated temperature tensile testing and stress-strain measurement of metal matrix composites

    NASA Technical Reports Server (NTRS)

    Diaz, J. O.

    1985-01-01

    Composites consisting of tungsten alloy wires in superalloy matrices are being studied because they offer the potential for increased strength compared to current materials used at temperatures up to at least 1093 C (2000F). Previous research at the NASA Lewis Research Center and at other laboratories in the U.S., Europe, and Japan has demonstrated laboratory feasibility for fiber reinforced superalloys (FRS). The data for the mechanical and physical properties used to evaluate candidate materials is limited and a need exists for a more detailed and complete data base. The focus of this work is to develop a test procedure to provide a more complete FRS data base to quantitatively evaluate the composite's potential for component applications. This paper will describe and discuss the equipment and procedures under development to obtain elevated temperature tensile stress-strain, strength and modulus data for the first generation of tungsten fiber reinforced superalloy composite (TFRS) materials. Tensile stress-strain tests are conducted using a constant crosshead speed tensile testing machine and a modified load-strain measuring apparatus. Elevated temperature tensile tests are performed using a resistance wound commercial furnace capable of heating test specimens up to 1093 C (2000 F). Tensile stress-strain data are obtained for hollow tubular stainless steel specimens serving as a prototype for future composite specimens.

  1. Tensile Stress Strain Behavior of Polypropylene Toughened with Bi-Modal Sebs

    NASA Astrophysics Data System (ADS)

    Mae, Hiroyuki; Omiya, Masaki; Kishimoto, Kikuo

    The objective is to characterize the effect of the bimodal distribution of rubber particles and its blend ratio on the mechanical properties of the thermoplastic polypropylene blended with two different styrene-ethylene-butadiene-styrene tri-block copolymer (SEBS) at the intermediate and high strain rates. Tensile tests are conducted at the nominal strain rates from 10-1 to 102 (1/sec). Phase morphology is investigated to estimate the bi-modal rubber particle size distribution. In addition, the in-situ observation is conducted during uniaxially stretching within transmission electron microscopy (TEM) step by step to investigate the deformation events depending on the elongation of samples. The elastic modulus increased gradually as the blend ratio of large rubber particle increased. An increase in the rupture strain was found for the bimodal rubber-particle distributed blend system where the blend ratios of small rubber particle and large rubber particle were the same. This is because the smaller particles dominant blend systems show the band-like craze deformation while the localized plastic deformation is taken place in the larger particles dominated blend systems. The synergistic effect of these rubber particles gives rise to a strong increase in the ductility of these bimodal rubber-particle distributed polypropylene systems.

  2. Correlation Between Microstructures and Tensile Properties of Strain-Based API X60 Pipeline Steels

    NASA Astrophysics Data System (ADS)

    Sung, Hyo Kyung; Lee, Dong Ho; Lee, Sunghak; Kim, Hyoung Seop; Ro, Yunjo; Lee, Chang Sun; Hwang, Byoungchul; Shin, Sang Yong

    2016-03-01

    The correlation between the microstructures and tensile properties of strain-based American Petroleum Institute (API) X60 pipeline steels was investigated. Eight types of strain-based API X60 pipeline steels were fabricated by varying the chemical compositions, such as C, Ni, Cr, and Mo, and the finish cooling temperatures, such as single-phase and dual-phase regions. In the 4N and 5C steels, the volume fractions of bainitic ferrite (BF) and the secondary phases increased with the increasing C and adding Cr instead of Ni. In the 5C and 6NC steels, the volume fractions of acicular ferrite (AF) and BF decreased with increasing C and adding Ni, whereas the volume fractions of polygonal ferrite (PF) and the secondary phases increased. In the 6NC and 6NM steels, the volume fraction of BF was increased by adding Mo instead of Cr, whereas the volume fractions of PF and the secondary phases decreased. In the steels rolled in the single-phase region, the volume fraction of polygonal ferrite ranged from 40 to 60 pct and the volume fraction of AF ranged from 20 to 40 pct. In the steels rolled in the dual-phase region, however, the volume fraction of PF was more than 70 pct and the volume fraction of AF was below 20 pct. The strength of the steels with a high volume fraction of AF was higher than those of the steels with a high volume fraction of PF, whereas the yield point elongation and the strain hardening exponent were opposite. The uniform elongation after the thermal aging process decreased with increasing volume fraction of PF, whereas the uniform elongation increased with increasing volume fraction of AF. The strain hardening exponent increased with increasing volume fraction of PF, but decreased with increasing volume fraction of AF and effective grain size.

  3. Correlation Between Microstructures and Tensile Properties of Strain-Based API X60 Pipeline Steels

    NASA Astrophysics Data System (ADS)

    Sung, Hyo Kyung; Lee, Dong Ho; Lee, Sunghak; Kim, Hyoung Seop; Ro, Yunjo; Lee, Chang Sun; Hwang, Byoungchul; Shin, Sang Yong

    2016-06-01

    The correlation between the microstructures and tensile properties of strain-based American Petroleum Institute (API) X60 pipeline steels was investigated. Eight types of strain-based API X60 pipeline steels were fabricated by varying the chemical compositions, such as C, Ni, Cr, and Mo, and the finish cooling temperatures, such as single-phase and dual-phase regions. In the 4N and 5C steels, the volume fractions of bainitic ferrite (BF) and the secondary phases increased with the increasing C and adding Cr instead of Ni. In the 5C and 6NC steels, the volume fractions of acicular ferrite (AF) and BF decreased with increasing C and adding Ni, whereas the volume fractions of polygonal ferrite (PF) and the secondary phases increased. In the 6NC and 6NM steels, the volume fraction of BF was increased by adding Mo instead of Cr, whereas the volume fractions of PF and the secondary phases decreased. In the steels rolled in the single-phase region, the volume fraction of polygonal ferrite ranged from 40 to 60 pct and the volume fraction of AF ranged from 20 to 40 pct. In the steels rolled in the dual-phase region, however, the volume fraction of PF was more than 70 pct and the volume fraction of AF was below 20 pct. The strength of the steels with a high volume fraction of AF was higher than those of the steels with a high volume fraction of PF, whereas the yield point elongation and the strain hardening exponent were opposite. The uniform elongation after the thermal aging process decreased with increasing volume fraction of PF, whereas the uniform elongation increased with increasing volume fraction of AF. The strain hardening exponent increased with increasing volume fraction of PF, but decreased with increasing volume fraction of AF and effective grain size.

  4. The Tensile Mechanical Properties of Thermomechanically Consolidated Titanium at Different Strain Rates

    NASA Astrophysics Data System (ADS)

    Liang, Cun; Ma, Mingxing; Jia, Mingtu; Raynova, Stiliana; Yan, Jianqiang; Zhang, Deliang

    2015-11-01

    The microstructures, tensile mechanical properties, and fracture behavior of a commercially pure (CP) titanium disk (called PF/Ti disk) and a CP titanium bar (called PE/Ti bar) made by powder compact forging (PCF) and powder compact extrusion (PCE) respectively have been studied. With increasing the strain rate from 10-4 to 10-1 s-1, the yield strength of the PF/Ti disk and PE/Ti bar increased from 708 to 811 MPa and from 672 to 764 MPa, respectively; their UTS increased from 824 to 1009 MPa and from 809 to 926 MPa, respectively, and their elongation to fracture decreased from 21 to 8 pct and from 25 to 17.8 pct, respectively. With a low strain rate of 10-4 s-1, the PF/Ti disk did not show any cavities at unbonded or weakly bonded interparticle boundaries, but the PE/Ti bar showed a small number of cavities with sizes of around 1 μm. With a high strain rate of 10-2 s-1, the PF/Ti disk showed a small number of cavities with sizes in the range of 0.1 to 0.5 μm, while for the PE/Ti bar, the cavities grew into microcracks of up to 20 μm long. The findings suggest that close to 100 pct of consolidation is rapidly achieved by PCF at 1573 K (1300 °C) and PCE at 1523 K (1250 °C), respectively, possibly due to the dissolution of the particle oxide surface films during heating and rapid diffusion bonding between the fresh particle surfaces during PCF and PCE.

  5. Induction of tenascin-C by cyclic tensile strain versus growth factors: distinct contributions by Rho/ROCK and MAPK signaling pathways.

    PubMed

    Chiquet, Matthias; Sarasa-Renedo, Ana; Tunç-Civelek, Vildan

    2004-09-17

    Expression of the extracellular matrix (ECM) protein tenascin-C is induced in fibroblasts by growth factors as well as by tensile strain. Mechanical stress can act on gene regulation directly, or indirectly via the paracrine release of soluble factors by the stimulated cells. To distinguish between these possibilities for tenascin-C, we asked whether cyclic tensile strain and soluble factors, respectively, induced its mRNA via related or separate mechanisms. When cyclic strain was applied to chick embryo fibroblasts cultured on silicone membranes, tenascin-C mRNA and protein levels were increased twofold within 6 h compared to the resting control. Medium conditioned by strained cells did not stimulate tenascin-C mRNA in resting cells. Tenascin-C mRNA in resting cells was increased by serum; however, cyclic strain still caused an additional induction. Likewise, the effect of TGF-beta1 or PDGF-BB was additive to that of cyclic strain, whereas IL-4 or H2O2 (a reactive oxygen species, ROS) did not change tenascin-C mRNA levels. Antagonists for distinct mitogen-activated protein kinases (MAPK) inhibited tenascin-C induction by TGF-beta1 and PDGF-BB, but not by cyclic strain. Conversely, a specific inhibitor of Rho-dependent kinase strongly attenuated the response of tenascin-C mRNA to cyclic strain, but had limited effect on induction by growth factors. The data suggest that regulation of tenascin-C in fibroblasts by cyclic strain occurs independently from soluble mediators and MAPK pathways; however, it requires Rho/ROCK signaling. PMID:15363633

  6. Differential analysis of band-edge photoluminescence spectra of germanium single crystals with different orientations under biaxial tensile strains

    NASA Astrophysics Data System (ADS)

    Emel'yanov, A. M.

    2016-06-01

    The previously published photoluminescence spectra of bulk germanium single crystals with orientations (100), (110), and (111) under different biaxial tensile strains have been investigated using the differential method proposed by the author for the analysis of luminescence spectra of semiconductors. An increase in the strain for all these orientations of the single crystals leads to a shift in the maxima of the differential spectra in the region of direct radiative transitions toward lower photon energies due to the narrowing of the germanium direct band gap. At the same time, the positions of the maxima of the differential spectra in the region of indirect radiative transitions remain almost unchanged. This indicates that the germanium indirect band gap does not depend on the tensile strains, at least for their values of ˜0.2-0.3%.

  7. Slow Strain Rate Tensile Testing to Assess the Ability of Superalloys to Resist Environment-Assisted Intergranular Cracking

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Telesman, Jack; Banik, Anthony; McDevitt, Erin

    2014-01-01

    Intergranular fatigue crack initiation and growth due to environmental degradation, especially at notched features, can often limit the fatigue life of disk superalloys at high temperatures. For clear comparisons, the effects of alloy composition on cracking in air needs to be understood and compared separately from variables associated with notches and cracks such as effective stress concentration, plastic flow, stress relaxation, and stress redistribution. The objective of this study was to attempt using simple tensile tests of specimens with uniform gage sections to compare the effects of varied alloy composition on environment-assisted cracking of several powder metal and cast and wrought superalloys including ME3, LSHR, Udimet 720, ATI 718Plus alloy, Haynes 282, and Inconel 740. Slow and fast strain-rate tensile tests were found to be a useful tool to compare propensities for intergranular surface crack initiation and growth. The effects of composition and heat treatment on tensile fracture strain and associated failure modes were compared. Environment interactions were determined to often limit ductility, by promoting intergranular surface cracking. The response of various superalloys and heat treatments to slow strain rate tensile testing varied substantially, showing that composition and microstructure can significantly influence environmental resistance to cracking.

  8. Silicon doping of HVPE GaN bulk-crystals avoiding tensile strain generation

    NASA Astrophysics Data System (ADS)

    Hofmann, Patrick; Röder, Christian; Habel, Frank; Leibiger, Gunnar; Beyer, Franziska C.; Gärtner, Günter; Eichler, Stefan; Mikolajick, Thomas

    2016-02-01

    Doped GaN:Si crystals were grown in a commercially available vertical HVPE reactor. The templates used for the HVPE heteroepitaxy were so-called FACELO seeds, with a starting GaN layer thickness of 3-4 μm. The FWHM of the 0002 and the 30\\bar{3}2 reflection of the HVPE-grown GaN:Si crystals with a thickness of 3 mm are {{31}\\prime\\prime} and {{78}\\prime\\prime} , respectively, indicating excellent crystal quality. Hall measurements resulted in a charge carrier concentration of 1.5× {{10}18} cm-3, while exhibiting a mobility of 250 cm-2V-1 s-1. These values coincide with the values extracted from FTIR measurements and the lineshape fitting of the A1(LO)/plasmon coupled phonon mode of the confocal Raman measurements. SIMS investigations yielded a silicon atom concentration of 1.8× {{10}18} cm-3. This indicates an activation of the dopant atoms of approximately 90%. The TDD determined by CL dark spot counting was 2× {{10}6} cm-2. Within the measurement accuracy, the confocal Raman measurements did not show a tensile strain generation due to the silicon doping with resulting charge carrier concentrations of 1.5× {{10}18} cm-3.

  9. Thickness-dependent electronic structure in ultrathin LaNiO3 films under tensile strain

    NASA Astrophysics Data System (ADS)

    Yoo, Hyang Keun; Hyun, Seung Ill; Chang, Young Jun; Moreschini, Luca; Sohn, Chang Hee; Kim, Hyeong-Do; Bostwick, Aaron; Rotenberg, Eli; Shim, Ji Hoon; Noh, Tae Won

    2016-01-01

    We investigated electronic-structure changes of tensile-strained ultrathin LaNi O3 (LNO) films from ten to one unit cells (UCs) using angle-resolved photoemission spectroscopy (ARPES). We found that there is a critical thickness tc between four and three UCs below which Ni eg electrons are confined in two-dimensional space. Furthermore, the Fermi surfaces (FSs) of LNO films below tc consist of two orthogonal pairs of one-dimensional (1D) straight parallel lines. Such a feature is not accidental as observed in constant-energy surfaces at all binding energies, which is not explained by first-principles calculations or the dynamical mean-field theory. The ARPES spectra also show anomalous spectral behaviors, such as no quasiparticle peak at the Fermi momentum but fast band dispersion comparable to the bare-band one, which is typical in a 1D system. As its possible origin, we propose 1D FS nesting, which also accounts for FS superstructures observed in ARPES.

  10. High-k gate stacks on low bandgap tensile strained Ge and GeSn alloys for field-effect transistors.

    PubMed

    Wirths, Stephan; Stange, Daniela; Pampillón, Maria-Angela; Tiedemann, Andreas T; Mussler, Gregor; Fox, Alfred; Breuer, Uwe; Baert, Bruno; San Andrés, Enrique; Nguyen, Ngoc D; Hartmann, Jean-Michel; Ikonic, Zoran; Mantl, Siegfried; Buca, Dan

    2015-01-14

    We present the epitaxial growth of Ge and Ge0.94Sn0.06 layers with 1.4% and 0.4% tensile strain, respectively, by reduced pressure chemical vapor deposition on relaxed GeSn buffers and the formation of high-k/metal gate stacks thereon. Annealing experiments reveal that process temperatures are limited to 350 °C to avoid Sn diffusion. Particular emphasis is placed on the electrical characterization of various high-k dielectrics, as 5 nm Al2O3, 5 nm HfO2, or 1 nmAl2O3/4 nm HfO2, on strained Ge and strained Ge0.94Sn0.06. Experimental capacitance-voltage characteristics are presented and the effect of the small bandgap, like strong response of minority carriers at applied field, are discussed via simulations. PMID:25531887

  11. A combined fracture-micromechanics model for tensile strain-softening in brittle materials, based on propagation of interacting microcracks

    NASA Astrophysics Data System (ADS)

    Pichler, Bernhard; Hellmich, Christian; Mang, Herbert A.

    2007-02-01

    Strain-softening is the decline in stress at increasing strain. Although microcracking is a commonly accepted reason for strain-softening, the majority of theoretical developments involve macroscopic damage evolution laws. To improve this situation, we propose a micromechanics-based damage evolution law by combining (i) the propagation criterion for a single penny-shaped crack embedded in an infinite matrix subjected to remote stresses (taken from linear-elastic fracture mechanics) and (ii) stiffness estimates for representative material volumes comprising interacting microcracks (taken from continuum micromechanics). This combination allows for modelling tensile strain-softening as a result of propagation of interacting microcracks, i.e. as a microstructural effect. The initial degree of damage, i.e. the initial microcrack size and the number of microcracks per unit volume, implies two different types of model-predicted tensile strain-softening behaviour under strain control: (i) continuous strain-softening, which occurs in case of initial damage above a critical value, and (ii) an instantaneous stress drop at the peak load (snap-back), which occurs in case of initial damage below a critical value. Copyright

  12. Theoretical investigation of tensile strained GeSn waveguide with Si₃N₄ liner stressor for mid-infrared detector and modulator applications.

    PubMed

    Zhang, Qingfang; Liu, Yan; Yan, Jing; Zhang, Chunfu; Hao, Yue; Han, Genquan

    2015-03-23

    We theoretically investigate a tensile strained GeSn waveguide integrated with Si₃N₄ liner stressor for the applications in mid-infrared (MIR) detector and modulator. A substantial tensile strain is induced in a 1 × 1 μm² GeSn waveguide by the expansion of 500 nm Si₃N₄ liner stressor and the contour plots of strain are simulated by the finite element simulation. Under the tensile strain, the direct bandgap E(G,Γ) of GeSn is significantly reduced by lowering the Γ conduction valley in energy and lifting of degeneracy of valence bands. Absorption coefficients of tensile strained GeSn waveguides with different Sn compositions are calculated. As the Si₃N₄ liner stressor expands by 1%, the cut-off wavelengths of tensile strained Ge(0.97)Sn(0.03), Ge(0.95)Sn(0.05), and Ge(0.90)Sn(0.10) waveguide photodetectors are extended to 2.32, 2.69, and 4.06 μm, respectively. Tensile strained Ge(0.90)Sn(0.10) waveguide electro-absorption modulator based on Franz-Keldysh (FK) effect is demonstrated in theory. External electric field dependence of cut-off wavelength and propagation loss of tensile strained Ge(0.90)Sn(0.10) waveguide is observed, due to the FK effect. PMID:25837129

  13. Hydrogen gettering and strain-induced platelet nucleation in tensilely strained Si0.4Ge0.6/Ge for layer exfoliation applications

    NASA Astrophysics Data System (ADS)

    Pitera, Arthur J.; Fitzgerald, E. A.

    2005-05-01

    We show that tensilely strained epitaxial layers getter interstitially dissolved hydrogen and accelerate the nucleation of platelets. Both of these result in subsurface crack propagation leading to surface blistering and eventual exfoliation of a H+-implanted semiconductor surface. In this work, a strained Si0.4Ge0.6 layer was used to enhance the exfoliation kinetics of relaxed Ge/Si1-xGex/Si virtual substrates by gettering hydrogen and providing a preferential nucleation site for platelets. Using platelet morphology and strain relaxation data, a nucleation and growth model was formulated accounting for both chemical and strain energy contributions to the free energy of platelet formation, revealing two kinetically limited growth regimes for platelets in tensilely strained Si0.4Ge0.6 films. Low-temperature (<200°C) annealing nucleates 1011-cm-2 platelets which grow in the strain-limited regime with minimal loss of hydrogen to surface effusion. At 250 °C, platelet growth is diffusion limited, requiring transport of H2 molecules to the strained layer. Subsequent annealing of strained Si0.4Ge0.6/Ge gettering structures at a temperature exceeding 300 °C results in significantly improved surface blistering kinetics over samples which do not contain a gettering layer. Incorporation of tensilely strained layers has the potential of reducing the implantation dose and annealing temperature necessary for layer transfer. Combined with virtual substrate bonding, they provide a promising solution for economical integration of high-performance semiconductors with silicon.

  14. Strain gradient plasticity theory applied to machining

    SciTech Connect

    Royer, Raphael; Laheurte, Raynald; Darnis, Philippe; Gerard, Alain; Cahuc, Olivier

    2011-05-04

    Machining is the most common manufacturing process. A good behaviour law is necessary in the simulation of machining processes (analytical and finite element modeling). Usually, commonly used behaviour laws such as Jonhson-Cook can bring unsatisfactory results especially for high strain and large deformation processes. Significant differences can appear between experimental and simulation results. The aim of this paper is to present the choices made regarding the behaviour law in this context. This study develops a large deformation strain-gradient theoretical framework with hypothesis linked to metal cutting processes. The theoretical framework has the potential of expressing moments at the tool tip as they were observed in experiments. It will be shown that the theory has the capability of interpreting the complex phenomena found in machining and more particularly in high speed machining.

  15. Strain gradient plasticity theory applied to machining

    NASA Astrophysics Data System (ADS)

    Royer, Raphaël; Laheurte, Raynald; Darnis, Philippe; Gérard, Alain; Cahuc, Olivier

    2011-05-01

    Machining is the most common manufacturing process. A good behaviour law is necessary in the simulation of machining processes (analytical and finite element modeling). Usually, commonly used behaviour laws such as Jonhson-Cook can bring unsatisfactory results especially for high strain and large deformation processes. Significant differences can appear between experimental and simulation results. The aim of this paper is to present the choices made regarding the behaviour law in this context. This study develops a large deformation strain-gradient theoretical framework with hypothesis linked to metal cutting processes. The theoretical framework has the potential of expressing moments at the tool tip as they were observed in experiments. It will be shown that the theory has the capability of interpreting the complex phenomena found in machining and more particularly in high speed machining.

  16. Osteogenic differentiation of human mesenchymal stem cells in collagen matrices: effect of uniaxial cyclic tensile strain on bone morphogenetic protein (BMP-2) mRNA expression.

    PubMed

    Sumanasinghe, Ruwan D; Bernacki, Susan H; Loboa, Elizabeth G

    2006-12-01

    Human mesenchymal stem cells (hMSCs) differentiate down an osteogenic pathway with appropriate mechanical and/or chemical stimuli. This study describes the successful culture of hMSCs in 3D collagen matrices under mechanical strain. Bone marrow-derived hMSCs were seeded in linear 3D type I collagen matrices and subjected to 0%, 10%, or 12% uniaxial cyclic tensile strain at 1 Hz for 4 h/day for 7 or 14 days. Cell viability studies indicated that hMSCs remained viable throughout the culture period irrespective of the applied strain level. Real-time RT-PCR studies indicated a significant increase in BMP-2 mRNA expression levels in hMSCs strained at 10% compared to the same day unstrained controls after both 7 and 14 days. An increase in BMP-2 was also observed in hMSCs subjected to 12% strain, but the increase was significant only in the 14-day sample. This is the first report of the culture of bone marrow-derived hMSCs in 3D collagen matrices under cyclic strain, and the first demonstration that strain alone can induce osteogenic differentiation without the addition of osteogenic supplements. Induction of bone differentiation in 3D culture is a critical step in the creation of bioengineered bone constructs. PMID:17518682

  17. Charge transport in NdNiO3 thin films: Effects of mn-doping versus tensile strain

    NASA Astrophysics Data System (ADS)

    Chandra, Mahesh; Aziz, Fozia; Rana, Rakesh; Late, Ravikiran; Rana, D. S.; Mavani, K. R.

    2014-04-01

    We have performed a comparative study of total three films, two films of NdNiO3 deposited on SrTiO3 (STO) and NdGaO3 (NGO) single-crystals and one 10% Mn-doped thin film of NdNi0.9Mn0.1O3 deposited on NGO. We find that both, the enhanced tensile strain and the Mn-doping drive the system to an insulating state from a metallic state at high temperatures. NdNiO3/NGO film shows a metal-insulator transition, which disappears in the other two films due to opening of charge-transfer gap. These results reveal that the effect of tensile strain on the resistivity of NdNiO3 is profound at low temperatures, whereas Mn-doping clearly dominates at high temperatures.

  18. Effects of surface cracks and strain rate on the tensile behavior of Balmoral Red granite

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    This paper presents an experimental procedure for studying the effects of surface cracks on the mechanical behavior of Balmoral Red granite under dynamic and quasi-static loading. Three different thermal shocks were applied on the surface of the Brazilian Disc test samples by keeping a flame torch at a fixed distance from the sample surface for 10, 30, and 60 seconds. Microscopy clearly shows that the number of the surface cracks increases with the duration of the thermal shock. After the thermal shock, the Brazilian Disc tests were performed using a servohydraulic materials testing machine and a compression Split Hopkinson Pressure Bar (SHPB) device. The results show that the tensile strength of the rock decreases and the rate sensitivity of the rock increases as more cracks are introduced to the structure. The DIC analysis of the Brazilian disc tests shows that the fracture of the sample initiates at the center of the samples or slightly closer to the incident bar contact point. This is followed by crushing of the samples at both contact points with the stress bars.

  19. Effects of Finish Cooling Temperature on Tensile Properties After Thermal Aging of Strain-Based API X60 Linepipe Steels

    NASA Astrophysics Data System (ADS)

    Sung, Hyo Kyung; Lee, Dong Ho; Shin, Sang Yong; Lee, Sunghak; Ro, Yunjo; Lee, Chang Sun; Hwang, Byoungchul

    2015-09-01

    Two types of strain-based American Petroleum Institute (API) X60 linepipe steels were fabricated at two finish cooling temperatures, 673 K and 723 K (400 °C and 450 °C), and the effects of the finish cooling temperatures on the tensile properties after thermal aging were investigated. The strain-based API X60 linepipe steels consisted mainly of polygonal ferrite (PF) or quasi-polygonal ferrite and the volume fraction of acicular ferrite increased with the increasing finish cooling temperature. In contrast, the volume fractions of bainitic ferrite (BF) and secondary phases decreased. The tensile properties before and after thermal aging at 473 K and 523 K (200 °C and 250 °C) were measured. The yield strength, ultimate tensile strength, and yield ratio increased with the increasing thermal aging temperature. The strain hardening rate in the steel fabricated at the higher finish cooling temperature decreased rapidly after thermal aging, probably due to the Cottrell atmosphere, whereas the strain hardening rate in the steel fabricated at the lower finish cooling temperature changed slightly after thermal aging. The uniform elongation and total elongation decreased with increasing thermal aging temperature, probably due to the interactions between carbon atoms and dislocations. The uniform elongation decreased rapidly with the decreasing volume fractions of BF and martensite and secondary phases. The yield ratio increased with the increasing thermal aging temperature, whereas the strain hardening exponent decreased. The strain hardening exponent of PL steel decreased rapidly after thermal aging because of the large number of mobile dislocations between PF and BF or martensite or secondary phases.

  20. Microstructure- and Strain Rate-Dependent Tensile Behavior of Fiber Laser-Welded DP980 Steel Joint

    NASA Astrophysics Data System (ADS)

    Jia, Qiang; Guo, Wei; Peng, Peng; Li, Minggao; Zhu, Ying; Zou, Guisheng

    2016-02-01

    DP980 steels were butt-welded by fiber laser welding. The microstructures, microhardness distribution, and tensile behavior of the joint were investigated. The results showed that the fusion zone (FZ) consisted of fully martensite with higher hardness compared to the base metal (BM). A softened zone (20 HV0.2 drop) was produced in heat-affected zone due to martensite tempering during the laser welding. The ultimate tensile strength (UTS) and yield strength (YS) of the laser-welded joint were not degraded compared to BM with the existence of softened zone. The UTS and YS of the welded joint increased with the increase of tensile strain rate. The work hardening exponents of the BM and welded joint showed weak positive strain rate dependence. The deformation of softened zone was restrained by the hardened FZ during loading, resulting in a higher work hardening rate of softened zone than that of BM. The failure of welded joint occurred in the BM instead of softened zone. The fracture surfaces of the joint exhibited typical ductile fracture over strain rate from 0.0001 to 0.1 s-1.

  1. Non-destructive and three-dimensional measurement of local strain development during tensile deformation in an aluminium alloy

    NASA Astrophysics Data System (ADS)

    Kobayashi, M.; Miura, H.; Toda, H.

    2015-08-01

    Anisotropy of mechanical responses depending on crystallographic orientation causes inhomogeneous deformation on the mesoscopic scale (grain size scale). Investigation of the local plastic strain development is important for discussing recrystallization mechanisms, because the sites with higher local plastic strain may act as potential nucleation sites for recrystallization. Recently, high-resolution X-ray tomography, which is non-destructive inspection method, has been utilized for observation of the materials structure. In synchrotron radiation X-ray tomography, more than 10,000 microstructural features, like precipitates, dispersions, compounds and hydrogen pores, can be observed in aluminium alloys. We have proposed employing these microstructural features as marker gauges to measure local strains, and then have developed a method to calculate the three-dimensional strain distribution by tracking the microstructural features. In this study, we report the development of local plastic strain as a function of the grain microstructure in an aluminium alloy by means of this three-dimensional strain measurement technique. Strongly heterogeneous strain development was observed during tensile loading to 30%. In other words, some parts of the sample deform little whereas another deforms a lot. However, strain in the whole specimen was keeping harmony. Comparing the microstructure with the strain concentration that is obtained by this method has a potential to reveal potential nucleation sites of recrystallization.

  2. Interaction of heat production, strain rate and stress power in a plastically deforming body under tensile test

    NASA Technical Reports Server (NTRS)

    Paglietti, A.

    1982-01-01

    At high strain rates the heat produced by plastic deformation can give rise to a rate dependent response even if the material has rate independent constitutive equations. This effect 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 strain at finite strain rates. It enables discovery of the parameters governing the thermodynamic strain rate effect, 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.

  3. Measurement of the extent of strain relief in InGaAs layers grown under tensile strain on InP(100) substrates

    NASA Astrophysics Data System (ADS)

    Maigné, P.; Gendry, M.; Venet, T.; Tahri, Y.; Hollinger, G.

    1996-07-01

    High resolution x-ray diffraction has been used to investigate the structural properties of InxGa1-xAs epitaxial layers grown under tension on InP(100) substrates. The nominal indium composition (x=0.42) corresponds to a small lattice mismatch and a two dimensional growth mode. We have also included for comparison two samples grown under compression covering the mostly strained and the mostly relaxed regimes. Our results show that the residual strain and the asymmetry in strain relaxation along <011> directions are always larger for layers under tension. This can be explained by the difference in dislocation glide velocity induced by a different indium content, by the dissociation of perfect dislocations and partially by the difference in thermal expansion coefficients between substrate and epilayer. The larger asymmetry in strain relaxation for tensile strain layers is interpreted by the existence of microcracks aligned in the [011] direction.

  4. Tensile strained Ge tunnel field-effect transistors: k · p material modeling and numerical device simulation

    SciTech Connect

    Kao, Kuo-Hsing; De Meyer, Kristin; Verhulst, Anne S.; Van de Put, Maarten; Soree, Bart; Magnus, Wim; Vandenberghe, William G.

    2014-01-28

    Group IV based tunnel field-effect transistors generally show lower on-current than III-V based devices because of the weaker phonon-assisted tunneling transitions in the group IV indirect bandgap materials. Direct tunneling in Ge, however, can be enhanced by strain engineering. In this work, we use a 30-band k · p method to calculate the band structure of biaxial tensile strained Ge and then extract the bandgaps and effective masses at Γ and L symmetry points in k-space, from which the parameters for the direct and indirect band-to-band tunneling (BTBT) models are determined. While transitions from the heavy and light hole valence bands to the conduction band edge at the L point are always bridged by phonon scattering, we highlight a new finding that only the light-hole-like valence band is strongly coupling to the conduction band at the Γ point even in the presence of strain based on the 30-band k · p analysis. By utilizing a Technology Computer Aided Design simulator equipped with the calculated band-to-band tunneling BTBT models, the electrical characteristics of tensile strained Ge point and line tunneling devices are self-consistently computed considering multiple dynamic nonlocal tunnel paths. The influence of field-induced quantum confinement on the tunneling onset is included. Our simulation predicts that an on-current up to 160 (260) μA/μm can be achieved along with on/off ratio > 10{sup 6} for V{sub DD} = 0.5 V by the n-type (p-type) line tunneling device made of 2.5% biaxial tensile strained Ge.

  5. Cyclic Tensile Strain Suppresses Catabolic Effects of Interleukin-1β in Fibrochondrocytes From the Temporomandibular Joint

    PubMed Central

    Agarwal, Sudha; Long, Ping; Gassner, Robert; Piesco, Nicholas P.; Buckley, Michael J.

    2016-01-01

    Objective To discern the effects of continuous passive motion on inflamed temporomandibular joints (TMJ). Methods The effects of continuous passive motion on TMJ were simulated by exposing primary cultures of rabbit TMJ fibrochondrocyte monolayers to cyclic tensile strain (CTS) in the presence of recombinant human interleukin-1β (rHuIL-1β) in vitro. The messenger RNA (mRNA) induction of rHuIL-1β response elements was examined by semiquantitative reverse transcriptase–polymerase chain reaction. The synthesis of nitric oxide was examined by Griess reaction, and the synthesis of prostaglandin E2 (PGE2) was examined by radioimmunoassay. The synthesis of proteins was examined by Western blot analysis of the cell extracts, and synthesis of proteoglycans via incorporation of 35S-sodium sulfate in the culture medium. Results Exposure of TMJ fibrochondrocytes to rHuIL-1β resulted in the induction of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2), which were paralleled by NO and PGE2 production. Additionally, IL-1β induced significant levels of collagenase (matrix metalloproteinase 1 [MMP-1]) within 4 hours, and this was sustained over a period of 48 hours. Concomitant application of CTS abrogated the catabolic effects of IL-1β on TMJ chondrocytes by inhibiting iNOS, COX-2, and MMP-1 mRNA production and NO, PGE2, and MMP-1 synthesis. CTS also counteracted cartilage degradation by augmenting expression of mRNA for tissue inhibitor of metalloproteinases 2 that is inhibited by rHuIL-1β. In parallel, CTS also counteracted rHuIL-1β–induced suppression of proteoglycan synthesis. Nevertheless, the presence of an inflammatory signal was a prerequisite for the observed CTS actions, because fibrochondrocytes, when exposed to CTS alone, did not exhibit any of the effects described above. Conclusion CTS acts as an effective antagonist of rHuIL-1β by potentially diminishing its catabolic actions on TMJ fibrochondrocytes. Furthermore, CTS actions appear

  6. Resistance fail strain gage technology as applied to composite materials

    NASA Technical Reports Server (NTRS)

    Tuttle, M. E.; Brinson, H. F.

    1985-01-01

    Existing strain gage technologies as applied to orthotropic composite materials are reviewed. The bonding procedures, transverse sensitivity effects, errors due to gage misalignment, and temperature compensation methods are addressed. Numerical examples are included where appropriate. It is shown that the orthotropic behavior of composites can result in experimental error which would not be expected based on practical experience with isotropic materials. In certain cases, the transverse sensitivity of strain gages and/or slight gage misalignment can result in strain measurement errors.

  7. High strain rate and quasi-static tensile behaviour of Ti-6Al-4V after cyclic damage

    NASA Astrophysics Data System (ADS)

    Galán López, J.; Verleysen, P.; Degrieck, J.

    2012-08-01

    It is common that energy absorbing structural elements are subjected to a number of loading cycles before a crash event. Several studies have shown that previous fatigue can significantly influence the tensile properties of some materials, and hence the behaviour of structural elements made of them. However, when the capacity of absorbing energy of engineering materials is determined, fresh material without any fatigue damage is most often used. This study investigates the effect of fatigue damage on the dynamic tensile properties of Ti-6Al-4V in thin-sheet form. Results are completed with tests at quasi-static strain rates and observations of the fracture surfaces, and compared with results obtained from other alloys and steel grades. The experiments show that the dynamic properties of Ti-6Al-4V are not affected by a number of fatigue loading cycles high enough to significantly reduce the energy absorbing capabilities of EDM machined samples.

  8. Tensile strain-rate sensitivity of tungsten/niobium composites at 1300 to 1600 K

    NASA Technical Reports Server (NTRS)

    Yun, H. M.; Titran, R. H.

    1992-01-01

    The tensile behavior of continuous tungsten fiber reinforced niobium composites (W/Nb), fabricated by an arc-spray process, was studied in the 1300 to 1600 K temperature range. The tensile properties of the fiber and matrix components as well as of the composites were measured and were compared to rule of mixtures (ROM) predictions. The deviation from the ROM was found to depend upon the chemistry of the tungsten alloy fibers, with positive deviations for ST300/Nb (i.e., stronger composite strength than the ROM) and negative or zero deviations for 218/Nb.

  9. Growth and characterization of highly tensile strained Ge1-xSnx formed on relaxed InyGa1-yP buffer layers

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Loke, Wan Khai; Yin, Tingting; Zhang, Zheng; D'Costa, Vijay Richard; Dong, Yuan; Liang, Gengchiau; Pan, Jisheng; Shen, Zexiang; Yoon, Soon Fatt; Tok, Eng Soon; Yeo, Yee-Chia

    2016-03-01

    Ge0.94Sn0.06 films with high tensile strain were grown on strain-relaxed InyGa1-yP virtual substrates using solid-source molecular beam epitaxy. The in-plane tensile strain in the Ge0.94Sn0.06 film was varied by changing the In mole fraction in InxGa1-xP buffer layer. The tensile strained Ge0.94Sn0.06 films were investigated by transmission electron microscopy, x-ray diffraction, and Raman spectroscopy. An in-plane tensile strain of up to 1% in the Ge0.94Sn0.06 was measured, which is much higher than that achieved using other buffer systems. Controlled thermal anneal experiment demonstrated that the strain was not relaxed for temperatures up to 500 °C. The band alignment of the tensile strained Ge0.94Sn0.06 on In0.77Ga0.23P was obtained by high resolution x-ray photoelectron spectroscopy. The Ge0.94Sn0.06/In0.77Ga0.23P interface was found to be of the type I band alignment, with a valence band offset of 0.31 ± 0.12 eV and a conduction band offset of 0.74 ± 0.12 eV.

  10. Development of a Plane Strain Tensile Geometry to Assess Shear Fracture in Dual Phase Steels

    NASA Astrophysics Data System (ADS)

    Taylor, M. D.; Matlock, D. K.; De Moor, E.; Speer, J. G.

    2014-10-01

    A geometrically modified sample capable of generating a triaxial stress state when tested on a standard uniaxial tensile frame was developed to replicate shear fractures observed during stretch bend tests and industrial sheet stamping operations. Seven commercially produced dual phase (DP) steels were tested using the geometrically modified sample, and the modified sample successfully produced shear fractures on a unique shear plane for all steels. For each steel, void densities were determined, based on metallographic analyses, as a function of imposed displacement. Microstructural properties of ferrite and martensite grain size, martensite volume fraction (MVF), retained austenite content, Vickers hardness, average nanoindentation hardness, average ferrite and martensite constituent hardness, and tensile properties were obtained in order to evaluate potential correlations with void data. A linear correlation was observed between Vickers hardness and the average nanoindentation hardness, verifying the ability of nanoindentation to produce data consistent with more traditional hardness measurement techniques. A linear relationship was observed between the number of voids present at 90% failure displacement and the martensite/ferrite hardness ratio, indicating that a decrease in relative hardness difference in a microstructure can suppress void formation, and potentially extend formability limits. The void population appeared independent of MVF, grain size, and tensile properties suggesting that constituent hardness may be a dominant parameter when considering suppression of void nucleation in DP steels.

  11. Conduction band structure and electron mobility in uniaxially strained Si via externally applied strain in nanomembranes

    NASA Astrophysics Data System (ADS)

    Chen, Feng; Euaruksakul, Chanan; Liu, Zheng; Himpsel, F. J.; Liu, Feng; Lagally, Max G.

    2011-08-01

    Strain changes the band structure of semiconductors. We use x-ray absorption spectroscopy to study the change in the density of conduction band (CB) states when silicon is uniaxially strained along the [1 0 0] and [1 1 0] directions. High stress can be applied to silicon nanomembranes, because their thinness allows high levels of strain without fracture. Strain-induced changes in both the sixfold degenerate Δ valleys and the eightfold degenerate L valleys are determined quantitatively. The uniaxial deformation potentials of both Δ and L valleys are directly extracted using a strain tensor appropriate to the boundary conditions, i.e., confinement in the plane in the direction orthogonal to the straining direction, which correspond to those of strained CMOS in commercial applications. The experimentally determined deformation potentials match the theoretical predictions well. We predict electron mobility enhancement created by strain-induced CB modifications.

  12. Micromechanical poroelastic finite element and shear-lag models of tendon predict large strain dependent Poisson's ratios and fluid expulsion under tensile loading.

    PubMed

    Ahmadzadeh, Hossein; Freedman, Benjamin R; Connizzo, Brianne K; Soslowsky, Louis J; Shenoy, Vivek B

    2015-08-01

    As tendons are loaded, they reduce in volume and exude fluid to the surrounding medium. Experimental studies have shown that tendon stretching results in a Poisson's ratio greater than 0.5, with a maximum value at small strains followed by a nonlinear decay. Here we present a computational model that attributes this macroscopic observation to the microscopic mechanism of the load transfer between fibrils under stretch. We develop a finite element model based on the mechanical role of the interfibrillar-linking elements, such as thin fibrils that bridge the aligned fibrils or macromolecules such as glycosaminoglycans (GAGs) in the interfibrillar sliding and verify it with a theoretical shear-lag model. We showed the existence of a previously unappreciated structure-function mechanism whereby the Poisson's ratio in tendon is affected by the strain applied and interfibrillar-linker properties, and together these features predict tendon volume shrinkage under tensile loading. During loading, the interfibrillar-linkers pulled fibrils toward each other and squeezed the matrix, leading to the Poisson's ratio larger than 0.5 and fluid expulsion. In addition, the rotation of the interfibrillar-linkers with respect to the fibrils at large strains caused a reduction in the volume shrinkage and eventual nonlinear decay in Poisson's ratio at large strains. Our model also predicts a fluid flow that has a radial pattern toward the surrounding medium, with the larger fluid velocities in proportion to the interfibrillar sliding. PMID:25934322

  13. Effect of strain rate on the tensile properties of unirradiated and irradiated V-4Cr-4Ti

    NASA Astrophysics Data System (ADS)

    Rowcliffe, A. F.; Zinkle, S. J.; Hoelzer, D. T.

    2000-12-01

    Tensile tests were carried out on an annealed, unirradiated V-4Cr-4Ti alloy from RT to 850°C at strain rates ranging from 10-1 to 10-5 s-1. Below 300°C, where interstitial solutes are relatively immobile, deformation is homogeneous, and the strain rate sensitivity (SRS) of the yield and flow stress is positive. Between 300°C and 700°C, the formation of solute atmospheres at locked dislocations results in dynamic strain-aging (DSA), deformation becomes heterogeneous, and the SRS of the flow stress is negative; in this regime the lower yield stress is independent of strain rate. Above 700°C, substitutional solutes are also mobile, DSA declines, and the material enters a power law creep regime in which the SRS becomes positive again. Following neutron irradiation to 0.5 dpa at temperatures ⩽400°C, severe flow localization occurs due to the high number density of <1 1 0> and <1 1 1> loops. However, above 400°C, strain hardening capacity returns but without the Lüders extension. At 500°C, after several percent plastic deformation, DSA occurs as interstitial solutes are released from the defect structure.

  14. Tunable electronic and optical properties of monolayer silicane under tensile strain: A many-body study

    SciTech Connect

    Shu, Huabing; Wang, Shudong; Li, Yunhai; Wang, Jinlan; Yip, Joanne

    2014-08-14

    The electronic structure and optical response of silicane to strain are investigated by employing first-principles calculations based on many-body perturbation theory. The bandgap can be efficiently engineered in a broad range and an indirect to direct bandgap transition is observed under a strain of 2.74%; the semiconducting silicane can even be turned into a metal under a very large strain. The transitions derive from the persistent downward shift of the lowest conduction band at the Γ-point upon an increasing strain. The quasi-particle bandgaps of silicane are sizable due to the weak dielectric screening and the low dimension; they are rapidly reduced as strain increases while the exciton bound energy is not that sensitive. Moreover, the optical absorption edge of the strained silicane significantly shifts towards a low photon energy region and falls into the visible light range, which might serve as a promising candidate for optoelectronic devices.

  15. Studies on tensile properties and fracture behavior of Al-6Si-0.5Mg (-Cu or/and Ni) alloys at various strain rates

    NASA Astrophysics Data System (ADS)

    Hossain, A.; Gulshan, F.; Kurny, A. S. W.

    2016-07-01

    The aim of this paper is to evaluate the effects of various strain rates on the tensile properties of Al-6Si-0.5Mg cast alloys with Cu or/and Ni additions and to establish data on the stress-strain behavior of the alloys with applications in automotive engineering. Experimental alloys of the following composition were prepared by melt processing technique. Both microstructure and the mechanical properties were investigated. The uniaxial tension test was carried out at strain rates ranging from 10-4s-1 to 10-2s-1. Tensile strengths were found to increase with ageing temperature and the maximum being attained at peak age condition (1hr at 225°C). The additions of Cu or/and Ni resulted in an increase in tensile strength and 2wt% Cu content alloy (Al-6Si-0.5Mg-2Cu) showed maximum strength. Evaluation of tensile properties at three strain rates (10-4, 10-3 and 10-2s-1) showed that strain rates affected the tensile properties significantly. At higher strain rates the strength was better but ductility was poor.

  16. Semiconductor-topological insulator transition of two-dimensional SbAs induced by biaxial tensile strain

    NASA Astrophysics Data System (ADS)

    Zhang, Shengli; Xie, Meiqiu; Cai, Bo; Zhang, Haijun; Ma, Yandong; Chen, Zhongfang; Zhu, Zhen; Hu, Ziyu; Zeng, Haibo

    2016-06-01

    A stibarsen [derived from Latin stibium (antimony) and arsenic] or allemontite, is a natural form of arsenic antimonide (SbAs) with the same layered structure as arsenic and antimony. Thus, exploring the two-dimensional SbAs nanosheets is of great importance to gain insights into the properties of group V-V compounds at the atomic scale. Here, we propose a class of two-dimensional V-V honeycomb binary compounds, SbAs monolayers, which can be tuned from semiconductor to topological insulator. By ab initio density functional theory, both α-SbAs and γ-SbAs display a significant direct band gap, while others are indirect semiconductors. Interestingly, in an atomically thin β-SbAs polymorph, spin-orbital coupling is significant, which reduces its band gap by 200 meV. Especially under biaxial tensile strain, the gap of β-SbAs can be closed and reopened with concomitant change of band shapes, which is reminiscent of band inversion known in many topological insulators. In addition, we find that the Z2 topological invariant is 1 for β-SbAs under the tensile strain of 12%, and the nontrivial topological feature of β-SbAs is also confirmed by the gapless edge states which cross linearly at the Γ point. These ultrathin group-V-V semiconductors with outstanding properties are highly favorable for applications in alternative optoelectronic and quantum spin Hall devices.

  17. Grain growth behavior and high-temperature high-strain-rate tensile ductility of iridium alloy DOP-26

    SciTech Connect

    McKamey, C.G.; Gubbi, A.N.; Lin, Y.; Cohron, J.W.; Lee, E.H.; George, E.P.

    1998-04-01

    This report summarizes results of studies conducted to date under the Iridium Alloy Characterization and Development subtask of the Radioisotope Power System Materials Production and Technology Program to characterize the properties of the new-process iridium-based DOP-26 alloy used for the Cassini space mission. This alloy was developed at Oak Ridge National Laboratory (ORNL) in the early 1980`s and is currently used by NASA for cladding and post-impact containment of the radioactive fuel in radioisotope thermoelectric generator (RTG) heat sources which provide electric power for interplanetary spacecraft. Included within this report are data generated on grain growth in vacuum or low-pressure oxygen environments; a comparison of grain growth in vacuum of the clad vent set cup material with sheet material; effect of grain size, test temperature, and oxygen exposure on high-temperature high-strain-rate tensile ductility; and grain growth in vacuum and high-temperature high-strain-rate tensile ductility of welded DOP-26. The data for the new-process material is compared to available old-process data.

  18. Inherently-Forced Tensile Strain in Nanodiamond-Derived Onion-like Carbon: Consequences in Defect-Induced Electrochemical Activation

    PubMed Central

    Ko, Young-Jin; Cho, Jung-Min; Kim, Inho; Jeong, Doo Seok; Lee, Kyeong-Seok; Park, Jong-Keuk; Baik, Young-Joon; Choi, Heon-Jin; Lee, Seung-Cheol; Lee, Wook-Seong

    2016-01-01

    We analyzed the nanodiamond-derived onion-like carbon (OLC) as function of synthesis temperature (1000~1400 °C), by high-resolution electron microscopy, electron energy loss spectroscopy, visible-Raman spectroscopy, ultraviolet photoemission spectroscopy, impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry. The temperature dependences of the obtained properties (averaged particle size, tensile strain, defect density, density of states, electron transfer kinetics, and electrochemical oxidation current) unanimously coincided: they initially increased and saturated at 1200 °C. It was attributed to the inherent tensile strains arising from (1) the volume expansion associated with the layer-wise diamond-to-graphite transformation of the core, which caused forced dilation of the outer shells during their thermal synthesis; (2) the extreme curvature of the shells. The former origin was dominant over the latter at the outermost shell, of which the relevant evolution in defect density, DOS and electron transfer kinetics determined the electrochemical performances. In detection of dopamine (DA), uric acid (UA) and ascorbic acid (AA) using the OLC as electrode, their oxidation peak currents were enhanced by factors of 15~60 with annealing temperature. Their limit of detection and the linear range of detection, in the post-treatment-free condition, were as excellent as those of the nano-carbon electrodes post-treated by Pt-decoration, N-doping, plasma, or polymer. PMID:27032957

  19. CO oxidation by MoS2-supported Au19 nanoparticles: effects of vacancy formation and tensile strain.

    PubMed

    Kwon, Soonho; Shin, Kihyun; Bang, Kihoon; Kim, Hyun You; Lee, Hyuck Mo

    2016-05-21

    The mechanism of the catalytic oxidation of CO activated by MoS2-supported Au19 nanoparticles (NPs) was studied using density functional theory calculations. Of particular interest were the effects of the physical/chemical modification of a MoS2 support on the CO oxidation pathway and the activation of specific reactive centers, i.e., the Au atoms of Au19 or the Au-MoS2 perimeter sites. We systematically modified MoS2 by introducing an S vacancy or 5% tensile strain and studied the shift of each reaction step and the overall change in the reaction pathway and activity. Despite the lack of direct involvement of the Au-MoS2 perimeter in the reaction, the combination of an S vacancy and the tensile strain in the MoS2 support was found to improve the stability and catalytic activity of Au NPs for CO oxidation. The results show that support modification can provide information for new pathways for the rational design of Au-based catalysts. PMID:27118269

  20. Inherently-Forced Tensile Strain in Nanodiamond-Derived Onion-like Carbon: Consequences in Defect-Induced Electrochemical Activation.

    PubMed

    Ko, Young-Jin; Cho, Jung-Min; Kim, Inho; Jeong, Doo Seok; Lee, Kyeong-Seok; Park, Jong-Keuk; Baik, Young-Joon; Choi, Heon-Jin; Lee, Seung-Cheol; Lee, Wook-Seong

    2016-01-01

    We analyzed the nanodiamond-derived onion-like carbon (OLC) as function of synthesis temperature (1000~1400 °C), by high-resolution electron microscopy, electron energy loss spectroscopy, visible-Raman spectroscopy, ultraviolet photoemission spectroscopy, impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry. The temperature dependences of the obtained properties (averaged particle size, tensile strain, defect density, density of states, electron transfer kinetics, and electrochemical oxidation current) unanimously coincided: they initially increased and saturated at 1200 °C. It was attributed to the inherent tensile strains arising from (1) the volume expansion associated with the layer-wise diamond-to-graphite transformation of the core, which caused forced dilation of the outer shells during their thermal synthesis; (2) the extreme curvature of the shells. The former origin was dominant over the latter at the outermost shell, of which the relevant evolution in defect density, DOS and electron transfer kinetics determined the electrochemical performances. In detection of dopamine (DA), uric acid (UA) and ascorbic acid (AA) using the OLC as electrode, their oxidation peak currents were enhanced by factors of 15~60 with annealing temperature. Their limit of detection and the linear range of detection, in the post-treatment-free condition, were as excellent as those of the nano-carbon electrodes post-treated by Pt-decoration, N-doping, plasma, or polymer. PMID:27032957

  1. Inherently-Forced Tensile Strain in Nanodiamond-Derived Onion-like Carbon: Consequences in Defect-Induced Electrochemical Activation

    NASA Astrophysics Data System (ADS)

    Ko, Young-Jin; Cho, Jung-Min; Kim, Inho; Jeong, Doo Seok; Lee, Kyeong-Seok; Park, Jong-Keuk; Baik, Young-Joon; Choi, Heon-Jin; Lee, Seung-Cheol; Lee, Wook-Seong

    2016-04-01

    We analyzed the nanodiamond-derived onion-like carbon (OLC) as function of synthesis temperature (1000~1400 °C), by high-resolution electron microscopy, electron energy loss spectroscopy, visible-Raman spectroscopy, ultraviolet photoemission spectroscopy, impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry. The temperature dependences of the obtained properties (averaged particle size, tensile strain, defect density, density of states, electron transfer kinetics, and electrochemical oxidation current) unanimously coincided: they initially increased and saturated at 1200 °C. It was attributed to the inherent tensile strains arising from (1) the volume expansion associated with the layer-wise diamond-to-graphite transformation of the core, which caused forced dilation of the outer shells during their thermal synthesis; (2) the extreme curvature of the shells. The former origin was dominant over the latter at the outermost shell, of which the relevant evolution in defect density, DOS and electron transfer kinetics determined the electrochemical performances. In detection of dopamine (DA), uric acid (UA) and ascorbic acid (AA) using the OLC as electrode, their oxidation peak currents were enhanced by factors of 15~60 with annealing temperature. Their limit of detection and the linear range of detection, in the post-treatment-free condition, were as excellent as those of the nano-carbon electrodes post-treated by Pt-decoration, N-doping, plasma, or polymer.

  2. Tensile-strain effect of inducing the indirect-to-direct band-gap transition and reducing the band-gap energy of Ge

    SciTech Connect

    Inaoka, Takeshi Furukawa, Takuro; Toma, Ryo; Yanagisawa, Susumu

    2015-09-14

    By means of a hybrid density-functional method, we investigate the tensile-strain effect of inducing the indirect-to-direct band-gap transition and reducing the band-gap energy of Ge. We consider [001], [111], and [110] uniaxial tensility and (001), (111), and (110) biaxial tensility. Under the condition of no normal stress, we determine both normal compression and internal strain, namely, relative displacement of two atoms in the primitive unit cell, by minimizing the total energy. We identify those strain types which can induce the band-gap transition, and evaluate the critical strain coefficient where the gap transition occurs. Either normal compression or internal strain operates unfavorably to induce the gap transition, which raises the critical strain coefficient or even blocks the transition. We also examine how each type of tensile strain decreases the band-gap energy, depending on its orientation. Our analysis clearly shows that synergistic operation of strain orientation and band anisotropy has a great influence on the gap transition and the gap energy.

  3. Role of RhoA/ROCK-dependent actin contractility in the induction of tenascin-C by cyclic tensile strain.

    PubMed

    Sarasa-Renedo, Ana; Tunç-Civelek, Vildan; Chiquet, Matthias

    2006-05-01

    In chick embryo fibroblasts, the mRNA for extracellular matrix protein tenascin-C is induced 2-fold by cyclic strain (10%, 0.3 Hz, 6 h). This response is attenuated by inhibiting Rho-dependent kinase (ROCK). The RhoA/ROCK signaling pathway is primarily involved in actin dynamics. Here, we demonstrate its crucial importance in regulating tenascin-C expression. Cyclic strain stimulated RhoA activation and induced fibroblast contraction. Chemical activators of RhoA synergistically enhanced the effects of cyclic strain on cell contractility. Interestingly, tenascin-C mRNA levels perfectly matched the extent of RhoA/ROCK-mediated actin contraction. First, RhoA activation by thrombin, lysophosphatidic acid, or colchicine induced tenascin-C mRNA to a similar extent as strain. Second, RhoA activating drugs in combination with cyclic strain caused a super-induction (4- to 5-fold) of tenascin-C mRNA, which was again suppressed by ROCK inhibition. Third, disruption of the actin cytoskeleton with latrunculin A abolished induction of tenascin-C mRNA by chemical RhoA activators in combination with cyclic strain. Lastly, we found that myosin II activity is required for tenascin-C induction by cyclic strain. We conclude that RhoA/ROCK-controlled actin contractility has a mechanosensory function in fibroblasts that correlates directly with tenascin-C gene expression. Previous RhoA/ROCK activation, either by chemical or mechanical signals, might render fibroblasts more sensitive to external tensile stress, e.g., during wound healing. PMID:16448650

  4. Dynamic-tensile-extrusion response of fluoropolymers

    SciTech Connect

    Brown, Eric N; Trujillo, Carl P; Gray, George T

    2009-01-01

    The current work applies the recently developed Dynamic-Tensile-Extrusion (Dyn-Ten-Ext) technique to polytetrafluoroethylene (PTFE) and polychlorotrifluoroethylene (PCTFE). Similar to the Taylor Impact Rod, Dynamic-Tensile-Extrusion is a strongly integrated test, probing a wide range of strain rates and stress states. However, the stress state is primarily tensile enabling investigation of dynamic tensile failure modes. Here we investigate the influence of this propensity to neck or not between PCTFE and PTFE on their response under dynamic tensile extrusion loading. The results of the Dyn-Ten-Ext technique are compared with two classic techniques. Both polymers have been investigated using Tensile Split Hopkinson Pressure Bar. The quasistatic and dynamic responses of both fluoro-polymers have been extensively characterized. The two polymers exhibit significantly different failure behavior under tensile loading at moderate strain rates. Polytetrafluoroethylene resists formation of a neck and exhibits significant strain hardening. Independent of temperature or strain rate, PTFE sustains true strains to failure of approximately 1.5. Polychlorotrifluoroethylene, on the other hand, consistently necks at true strains of approximately 0.05.

  5. Characterization of Tensile Properties, Limiting Strains, and Deep Drawing Behavior of AA5754-H22 Sheet at Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Panicker, Sudhy S.; Singh, Har Govind; Panda, Sushanta Kumar; Dashwood, Richard

    2015-11-01

    Automotive industries are very much interested in characterization of formability improvement of aluminum alloys at elevated temperatures before designing tools, heating systems, and processing sequences for fabrication of auto-body panels by warm forming technology. In this study, tensile tests of AA5754-H22 aluminum alloy were carried out at five different temperatures and three different strain rates to investigate the deformation behavior correlating with Cowper-Symonds constitutive equation. Laboratory scale warm forming facilities were designed and fabricated to perform limiting dome height and deep drawing tests to evaluate forming limit strains and drawability of sheet metal at different tool temperatures. The forming limit strain and dome height improved significantly when both the die and punch were heated to 200 °C. Remarkable improvement in deep drawn cup depth was observed when die and punch temperatures were maintained at 200 and 30 °C, respectively, producing a non-isothermal temperature gradient of approximately 93 °C across the blank from flange to center. The forming behavior at different isothermal and non-isothermal conditions were predicted successfully using a thermo-mechanical FE model incorporating temperature-dependent properties in Barlat-89 yield criterion coupled with Cowper-Symonds hardening model, and the thinning/failure location in deformed cups were validated implementing the experimental limiting strains as damage model.

  6. The molecular kink paradigm for rubber elasticity: Numerical simulations of explicit polyisoprene networks at low to moderate tensile strains

    NASA Astrophysics Data System (ADS)

    Hanson, David E.

    2011-08-01

    Based on recent molecular dynamics and ab initio simulations of small isoprene molecules, we propose a new ansatz for rubber elasticity. We envision a network chain as a series of independent molecular kinks, each comprised of a small number of backbone units, and the strain as being imposed along the contour of the chain. We treat chain extension in three distinct force regimes: (Ia) near zero strain, where we assume that the chain is extended within a well defined tube, with all of the kinks participating simultaneously as entropic elastic springs, (II) when the chain becomes sensibly straight, giving rise to a purely enthalpic stretching force (until bond rupture occurs) and, (Ib) a linear entropic regime, between regimes Ia and II, in which a force limit is imposed by tube deformation. In this intermediate regime, the molecular kinks are assumed to be gradually straightened until the chain becomes a series of straight segments between entanglements. We assume that there exists a tube deformation tension limit that is inversely proportional to the chain path tortuosity. Here we report the results of numerical simulations of explicit three-dimensional, periodic, polyisoprene networks, using these extension-only force models. At low strain, crosslink nodes are moved affinely, up to an arbitrary node force limit. Above this limit, non-affine motion of the nodes is allowed to relax unbalanced chain forces. Our simulation results are in good agreement with tensile stress vs. strain experiments.

  7. Tensile strain / transverse compressive stress effects in Nb{sub 3}Sn multifilamentary wires with CuNb reinforcing stabilizer

    SciTech Connect

    Katagiri, K.; Shoji, Y.; Noto, K.

    1997-06-01

    In order to improve the strain/stress characteristics of the critical current I{sub c}, the use of external CuNb reinforcing stabilizer, instead of the conventional Cu stabilizer, with bronze processed Nb{sub 3}Sn multifilamentary superconducting wires was examined up to the magnetic field of 14T and at a temperature of 4.2K. Although the axial tensile strain sensitivity of I{sub c} was not changed, the strain for peak I{sub c} as well as the reversible strain limit increased by 0.14% when the Cu stabilizer was replaced by the CuNb reinforcing stabilizer. On the other hand, the transverse compressive stress sensitivity of I{sub c} decreased and the reversible stress limit increased. An increase in both a bronze to Nb ratio and Sn content in bronze matrix resulted in a higher stress tolerance and, as a consequence, the contribution of the CuNb reinforcement became relatively small.

  8. Effect of test temperature and strain rate on the tensile properties of high-strength, high-conductivity copper alloys

    SciTech Connect

    Zinkle, S.J.; Eatherly, W.S.

    1997-04-01

    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 strain rates 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 strain rate at room temperature, but the strain rate 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 strain rate 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.

  9. Tensile stress-strain and work hardening behaviour of P9 steel for wrapper application in sodium cooled fast reactors

    NASA Astrophysics Data System (ADS)

    Christopher, J.; Choudhary, B. K.; Isaac Samuel, E.; Mathew, M. D.; Jayakumar, T.

    2012-01-01

    Tensile flow behaviour of P9 steel with different silicon content has been examined in the framework of Hollomon, Ludwik, Swift, Ludwigson and Voce relationships for a wide temperature range (300-873 K) at a strain rate of 1.3 × 10 -3 s -1. Ludwigson equation described true stress ( σ)-true plastic strain ( ɛ) data most accurately in the range 300-723 K. At high temperatures (773-873 K), Ludwigson equation reduces to Hollomon equation. The variations of instantaneous work hardening rate ( θ = dσ/ dɛ) and θσ with stress indicated two-stage work hardening behaviour. True stress-true plastic strain, flow parameters, θ vs. σ and θσ vs. σ with respect to temperature exhibited three distinct temperature regimes and displayed anomalous behaviour due to dynamic strain ageing at intermediate temperatures. Rapid decrease in flow stress and flow parameters, and rapid shift in θ- σ and θσ- σ towards lower stresses with increase in temperature indicated dominance of dynamic recovery at high temperatures.

  10. Control of Sn Precipitation and Strain Relaxation in Compositionally Step-Graded Ge1-xSnx Buffer Layers for Tensile-Strained Ge Layers

    NASA Astrophysics Data System (ADS)

    Shimura, Yosuke; Tsutsui, Norimasa; Nakatsuka, Osamu; Sakai, Akira; Zaima, Shigeaki

    2009-04-01

    We investigated the relationship between Sn precipitation and strain relaxation in Ge1-xSnx buffer layers grown by the compositionally step-graded (CSG) method on a virtual Ge substrate. We found that the strain in the upper Ge1-xSnx layers is reduced by Sn precipitation rather than the lateral propagation of misfit dislocations at the interfaces of upper Ge1-xSnx layers in the CSG method. The critical misfit strain was increased to 5.8 ×10-3 compared with that in our previous work by lowering the temperature of the postdeposition annealing, and a Sn content of 6.3% in the Ge1-xSnx buffer layer was achieved with a large degree of strain relaxation using only two stacked layers of the CSG structure. An in-plane tensile strain of 0.62% in a 30-nm-thick Ge layer fabricated on these Ge1-xSnx buffer layers was achieved.

  11. Numerical simulations of rubber networks at moderate to high tensile strains using a purely enthalpic force extension curve for individual chains

    NASA Astrophysics Data System (ADS)

    Hanson, David E.

    2009-12-01

    We report the results of numerical simulations of random, three-dimensional, periodic, tetrafunctional networks in response to a volume-preserving tensile strain. For the intranode force, we use a polynomial fit to a purely enthalpic ab initio force extension curve for extended polyisoprene. The simulation includes a relaxation procedure to minimize the node forces and enforces chain rupture when the extension of a network chain reaches the ab initio rupture strain. For the reasonable assumption that the distribution of network chain lengths is Gaussian, we find that the calculated snap-back velocity, temperature increase due to chain ruptures and predicted tensile stress versus strain curve are consistent with experimental data in the moderate to high extension regime. Our results show that a perfect tetrafunctional polyisoprene network is extremely robust, capable of supporting tensile stresses at least a factor of 10 greater than what is observed experimentally.

  12. Numerical simulations of rubber networks at moderate to high tensile strains using a purely enthalpic force extension curve for individual chains

    SciTech Connect

    Hanson, David Edward

    2009-01-01

    We report the results of numerical simulations of random, three-dimensional, periodic, tetrafunctional networks in response to a volume-preserving tensile strain. For the intranode force, we use a polynomial fit to a purely enthalpic ab initio force extension curve for extended polyisoprene. The simulation includes a relaxation procedure to minimize the node forces and enforces chain rupture when the extension of a network chain reaches the ab initio rupture strain. For the reasonable assumption that the distribution of network chain lengths is Gaussian, we find that the calculated snap-back velocity, temperature increase due to chain ruptures and predicted tensile stress versus strain curve are consistent with experimental data in the moderate to high extension regime. Our results show that a perfect tetrafunctional polyisoprene network is extremely robust, capable of supporting tensile stresses at least a factor of 10 greater than what is observed experimentally.

  13. Tensile-Strained GeSn Metal-Oxide-Semiconductor Field-Effect Transistor Devices on Si(111) Using Solid Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Lieten, Ruben R.; Maeda, Tatsuro; Jevasuwan, Wipakorn; Hattori, Hiroyuki; Uchida, Noriyuki; Miura, Shu; Tanaka, Masatoshi; Locquet, Jean-Pierre

    2013-10-01

    We demonstrate tensile-strained GeSn metal-oxide-semiconductor field-effect transistor (MOSFET) devices on Si(111) substrates using solid phase epitaxy of amorphous GeSn layers. Amorphous GeSn layers are obtained by limiting the adatom surface mobility during deposition. Subsequent annealing transforms the amorphous layer into single-crystalline GeSn by solid phase epitaxy. Single-crystalline GeSn layers with 4.5% Sn and 0.33% tensile strain are fabricated on Si(111) substrates. To verify the structural quality of thin-film GeSn as a channel material, we fabricate ultrathin GeSn p-channel MOSFETs (pMOSFETs) on Si(111). We demonstrate junctionless depletion-mode operation of tensile-strained GeSn(111) pMOSFETs on Si substrates.

  14. Tuning the energy gap of bilayer α-graphyne by applying strain and electric field

    NASA Astrophysics Data System (ADS)

    Yang, Hang; Wu, Wen-Zhi; Jin, Yu; Wan-Lin, Guo

    2016-02-01

    Our density functional theory calculations show that the energy gap of bilayer α-graphyne can be modulated by a vertically applied electric field and interlayer strain. Like bilayer graphene, the bilayer α-graphyne has electronic properties that are hardly changed under purely mechanical strain, while an external electric field can open the gap up to 120 meV. It is of special interest that compressive strain can further enlarge the field induced gap up to 160 meV, while tensile strain reduces the gap. We attribute the gap variation to the novel interlayer charge redistribution between bilayer α-graphynes. These findings shed light on the modulation of Dirac cone structures and potential applications of graphyne in mechanical-electric devices. Project supported by the National Key Basic Research Program of China (Grant Nos. 2013CB932604 and 2012CB933403), the National Natural Science Foundation of China (Grant Nos. 51472117 and 51535005), the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures, China (Grant No. 0414K01), the Nanjing University of Aeronautics and Astronautics (NUAA) Fundamental Research Funds, China (Grant No. NP2015203), and the Priority Academic Program Development of Jiangsu Higher Education Institutions.

  15. Tensile Lattice Strain Accelerates Oxygen Surface Exchange and Diffusion in La1–xSrxCoO3−δ Thin Films

    PubMed Central

    2013-01-01

    The influence of lattice strain on the oxygen exchange kinetics and diffusion in oxides was investigated on (100) epitaxial La1–xSrxCoO3−δ (LSC) thin films grown by pulsed laser deposition. Planar tensile and compressively strained LSC films were obtained on single-crystalline SrTiO3 and LaAlO3. 18O isotope exchange depth profiling with ToF-SIMS was employed to simultaneously measure the tracer surface exchange coefficient k* and the tracer diffusion coefficient D* in the temperature range 280–475 °C. In accordance with recent theoretical findings, much faster surface exchange (∼4 times) and diffusion (∼10 times) were observed for the tensile strained films compared to the compressively strained films in the entire temperature range. The same strain effect—tensile strain leading to higher k* and D*—was found for different LSC compositions (x = 0.2 and x = 0.4) and for surface-etched films. The temperature dependence of k* and D* is discussed with respect to the contributions of strain states, formation enthalpy of oxygen vacancies, and vacancy mobility at different temperatures. Our findings point toward the control of oxygen surface exchange and diffusion kinetics by means of lattice strain in existing mixed conducting oxides for energy conversion applications. PMID:23527691

  16. Mechanical strains and electric fields applied to topologically imprinted elastomers

    NASA Astrophysics Data System (ADS)

    Burridge, D. J.; Mao, Y.; Warner, M.

    2006-08-01

    We analyze and predict the behavior of a chirally imprinted elastomer under a mechanical strain and an electric field, applied along the helical axis. As the strain and/or field increases, the system is deformed from a conical or transverse imprinted state towards an ultimately nematic one. At a critical strain and/or field there is a first-order transition to a low imprinting efficiency state. This transition is accompanied by a discontinuous global rotation of the director toward the axis of the imprinted helix, measured by the cone angle, θ . We show that the threshold electric field required for switching this transition can be conveniently low, provided an appropriate prestrain is imposed. We suggest that these properties may give rise to a “chiral pump.”

  17. Neutron Bragg-edge-imaging for strain mapping under in situ tensile loading

    SciTech Connect

    Woracek, R.; Penumadu, D.; Kardjilov, N.; Hilger, A.; Strobl, M.; Wimpory, R. C.; Manke, I.; Banhart, J.

    2011-05-01

    Wavelength selective neutron radiography at a cold neutron reactor source was used to measure strain and determine (residual) stresses in a steel sample under plane stress conditions. We present a new technique that uses an energy-resolved neutron imaging system based on a double crystal monochromator and is equipped with a specially developed (in situ) biaxial load frame to perform Bragg edge based transmission imaging. The neutron imaging technique provides a viewing area of 7 cm by 7 cm with a spatial resolution on the order of {approx} 100 {mu}m. The stress-induced shifts of the Bragg edge corresponding to the (110) lattice plane were resolved spatially for a ferritic steel alloy A36 (ASTM international) sample. Furthermore it is demonstrated that results agree with comparative data obtained using neutron diffraction and resistance based strain-gauge rosettes.

  18. Influence of phosphorus on the tensile stress strain curves in copper

    NASA Astrophysics Data System (ADS)

    Sandström, Rolf

    2016-03-01

    Copper canisters are planned to be used for final disposal of spent nuclear fuel in Sweden. The canisters will be exposed to slow plastic straining over extensive periods of time. To be able to predict the mechanical properties a range of basic models have previously been developed for copper with and without phosphorus (Cu-OFP, Cu-OF). Already with the small amount of phosphorus added in the canisters (60 wt. ppm) dramatic improvements in the measured creep strength and the creep ductility are found. The basic models are further developed in the present paper. The influence of phosphorus on slow strain rate tests is analysed. It is shown that the main effect of phosphorus is that it prevents brittle rupture, which is modelled by taking creep cavitation into account.

  19. Measurement of compressive and tensile strain in the railway structures with FBG sensor packages

    NASA Astrophysics Data System (ADS)

    Kim, Ki-Soo; Kim, Young-Jin; Nam, Soon-Sung; Kwon, Hyung-seok

    2009-03-01

    For monitoring of railway structures, optical fiber sensors are very convenient. The fiber sensors are very small and do not disturb the structural properties. They also have several merits such as electro-magnetic immunity, long signal transmission, good accuracy and multiplicity of one sensor line. Strain measurement technologies with fiber optic sensors have been investigated as a part of smart structure. In this paper, we investigated the possibilities of fiber optic sensor application to the monitoring of railway structures. We expect that the fiber optic sensors have much less noises than electrical strain gauges because of electro-magnetic immunity while railways operate electric power of 22000 volts. Fiber optic sensors showed good durability and long term stability for continuous monitoring of the railway structures as well as good response to the structural behaviors during construction.

  20. Quantitative strain and slope evaluation on a double lap joint tensile test using ESPSI

    NASA Astrophysics Data System (ADS)

    Molimard, J.; Bounda, D.; Vautrin, A.

    2006-08-01

    The present study is based on the use of electronical speckle pattern shearing interferometry (ESPSI) on a double lap joint, the joined parts being two steel blocks and two composite plates. ESPSI is used to investigate de strain maps close to the end of the bonding in the center part of the specimen. The ESPSI set-up allows to get the full field strain and slope maps of a given surface. Its architecture is based on optical fibres which gives a portable assembly that can be used in a civil/mechanical engineering laboratory. This presentation emphases the advantages of such a method and its performances. Last some results are given and compared to an analytical approach.

  1. The relationship between the n-value and applied strain

    NASA Astrophysics Data System (ADS)

    Calzolaio, Ciro; Bruzzone, Pierluigi; Roth, Felix

    2013-07-01

    The most popular fit for describing the volt-ampere characteristic of a superconducting material is a power law with exponent n. Usually for a Nb3Sn wire the n-index is parametrized as a function of the sole critical current (Ic). An experiment to determine whether the n-index also shows an explicit dependence on the strain (ɛ) has been performed for an ITER (International Thermonuclear Experimental Reactor) wire. From the same wire, three pairs of samples were prepared. The three pairs were mounted on two Ti-ITER barrels, on two 316L stainless steel barrels and on two INCONEL™ alloy C-276 barrels, and heat treated. The critical current was then measured in the field range of 9-15 T. From the Ic measurements it was possible to derive three n versus Ic curves. Each curve corresponds to a different applied strain, as the three barrel materials have different thermal contraction coefficients. By analysing the three curves, the explicit dependence of the n-index on the strain is evaluated. In the strain range covered by the measurements (up to ≈-0.65% intrinsic strain), the n-value scales with the sole critical current Ic.

  2. Measurement of stress and strain applied to electrochemically aligned collagen fibres by second-harmonic generation microscopy

    NASA Astrophysics Data System (ADS)

    Goami, Nobutaka; Yoshiki, Keisuke; Namazu, Takahiro; Inoue, Shozo

    2011-10-01

    In this study, we developed a novel strain measurement technique for electrochemically aligned collagen (ELAC) fibres using second harmonic generation (SHG) microscopy. The ELAC fibres were prepared by a typical electrochemical method and were subjected to cross-linking. For comparison with natural collagen fibres, polarization dependency of the prepared ELAC fibres and that of a human Achilles' tendon were evaluated. The results showed that, because of crosslinking, the ELAC fibres exhibit polarization dependency similar to that of the tendon but only in a region close to the tendon. The relationship between SHG and the applied strain was determined by a combination of SHG microscopy and tensile tests. The SHG from the ELAC fibres changed in the high strain region because of the applied stress.

  3. Strain rate dependence of the tensile properties of V-(4--5%)Cr-(4--5%)Ti irradiated in EBR-II and HFBR

    SciTech Connect

    Zinkle, S.J.; Snead, L.L.; Robertson, J.P.; Rowcliffe, A.F.

    1998-03-01

    Elevated temperature tensile tests performed on V-(405)Cr-(4-5)Ti indicate that the yield stress increases with increasing strain rate for irradiation and test temperatures near 200 C, and decreases with increasing strain rate for irradiation and test temperatures near 400 C. This observation is in qualitative agreement with the temperature-dependent strain rate effects observed on unirradiated specimens, and implies that some interstitial solute remains free to migrate in irradiated specimens. Additional strain rate data at different temperatures are needed.

  4. The theoretical strength of rubber: numerical simulations of polyisoprene networks at high tensile strains evidence the role of average chain tortuosity

    NASA Astrophysics Data System (ADS)

    Hanson, David E.; Barber, John L.

    2013-10-01

    The ultimate stress and strain of polyisoprene rubber were studied by numerical simulations of three-dimensional random networks, subjected to tensile strains high enough to cause chain rupture. Previously published molecular chain force extension models and a numerical network construction procedure were used to perform the simulations for network crosslink densities between 2 × 1019 and 1 × 1020 cm-3, corresponding to experimental dicumyl-peroxide concentrations of 1-5 parts per hundred. At tensile failure (defined as the point of maximum stress), we find that the fraction of network chains ruptured is between 0.1% and 1%, depending on the crosslink density. The fraction of network chains that are taut, i.e. their end-to-end distance is greater than their unstretched contour length, ranges between 10% and 15% at failure. Our model predicts that the theoretical (defect-free) failure stress should be about twice the highest experimental value reported. For extensions approaching failure, tensile stress is dominated by the network morphology and purely enthalpic bond distortion forces and, in this regime, the model has essentially no free parameters. The average initial chain tortuosity (τ) appears to be an important statistical property of rubber networks; if the stress is scaled by τ and the tensile strain is scaled by τ-1, we obtain a master curve for stress versus strain, valid for all crosslink densities. We derive an analytic expression for the average tortuosity, which is in agreement with values calculated in the simulations.

  5. A novel culture morphology resulting from applied mechanical strain

    NASA Technical Reports Server (NTRS)

    Grymes, R. A.; Sawyer, C.

    1997-01-01

    To demonstrate that cells both perceive and respond to external force, a strain/relaxation regimen was applied to normal human fetal and aged dermal fibroblasts cultured as monolayers on flexible membranes. The precisely controlled protocol of stretch (20% elongation of the culture membrane) at 6.67 cycles/min caused a progressive change in the monolayers, such that the original randomly distributed pattern of cells became a symmetric, radial distribution as the cell bodies aligned parallel to the applied force. High cell density interfered with the success of re-alignment in the fetal cell cultures observed, which may reflect a preference in this cell strain for cell-cell over cell-matrix contacts. The chronologically aged cells observed did not demonstrate this feature, aligning efficiently at all seeding densities examined. The role of microfilaments in force perception and transmission was investigated through the addition of cytochalasin D in graded doses. Both intercellular interactions and cytoskeletal integrity mediate the morphological response to mechanical strain.

  6. The influence of deformation-induced residual stresses on the post-forming tensile stress/strain behavior of dual-phase steels

    NASA Astrophysics Data System (ADS)

    Hance, Brandon Michael

    It was hypothesized that, in dual-phase (DP) steels, strain partitioning between ferrite (alpha) and martensite (alpha') during deformation results in a distribution of post-deformation residual stresses that, in turn, affects the subsequent strength, work hardening behavior and formability when the strain path is changed. The post-forming deformation-induced residual stress state was expected to depend upon the microstructure, the amount of strain and the prestrain path. The primary objective of this research program was to understand the influence of deformation-induced residual stresses on the post-forming tensile stress/strain behavior of DP steels. Three commercially produced sheet steels were considered in this analysis: (1) a DP steel with approximately 15 vol. % martensite, (2) a conventional high-strength, low-alloy (HSLA) steel, and (3) a conventional, ultra-low-carbon interstitial-free (IF) steel. Samples of each steel were subjected to various prestrain levels in various plane-stress forming modes, including uniaxial tension, plane strain and balanced biaxial stretching. Neutron diffraction experiments confirmed the presence of large post-forming deformation-induced residual stresses in the ferrite phase of the DP steel. The deformation-alphainduced residual stress state varied systematically with the prestrain mode, where the principal residual stress components are proportional to the principal strain components of the prestrain mode, but opposite in sign. For the first time, and by direct experimental correlation, it was shown that deformation-induced residual stresses greatly affect the post-forming tensile stress/strain behavior of DP steels. As previously reported in the literature, the formability (residual tensile ductility) of the IF steel and the HSLA steel was adversely affected by strain path changes. The DP steel presents a formability advantage over the conventional IF and HSLA steels, and is expected to be particularly well suited for

  7. Modulating the electronic properties of germanium nanowires via applied strain and surface passivation.

    PubMed

    Sk, Mahasin Alam; Ng, Man-Fai; Huang, Lin; Lim, Kok Hwa

    2013-04-28

    We report a systematic study on the surface passivation and strain effects on the electronic properties of hydrogenated germanium nanowires (H-GeNWs) with different growth orientations and diameters using density functional theory calculations. We show that increasing the coverage percentage of halogen passivations--fluorine (F) and chlorine (Cl) in particular--reduces the band gap of the GeNWs drastically but not linearly, depending on the chemical environment of the passivation sites. Moreover, we find that in general, applying strain--either compression or tensile--can only induce a decreased band gap in GeNWs but exception is found in <110> GeNWs: an increased band gap can be induced which is determined to be related to their surface structures. The current work reveals that electronic response upon structural changes caused by external factors is more sensitive in <110> GeNWs than in <100> GeNWs, suggesting that GeNWs with selected growth orientation can be applied in specialized applications that require different degrees of sensitivity or robustness. PMID:23493789

  8. Use of Slow Strain Rate Tensile Testing to Assess the Ability of Several Superalloys to Resist Environmentally-Assisted Intergranular Cracking

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Telesman, Jack; Banik, Anthony; McDevitt, Erin

    2014-01-01

    Intergranular fatigue crack initiation and growth due to environmental degradation, especially at notched features, can often limit the fatigue life of disk superalloys at high temperatures. For clear comparisons, the effects of alloy composition on cracking in air needs to be understood and compared separately from variables associated with notches and cracks such as effective stress concentration, plastic flow, stress relaxation, and stress redistribution. The objective of this study was to attempt using simple tensile tests of specimens with uniform gage sections to compare the effects of varied alloy composition on environment-assisted cracking of several powder metal and cast and wrought superalloys including ME3, LSHR, Udimet 720(TradeMark) ATI 718Plus(Registered TradeMark) alloy, Haynes 282(Trademark), and Inconel 740(TradeMark) Slow and fast strain-rate tensile tests were found to be a useful tool to compare propensities for intergranular surface crack initiation and growth. The effects of composition and heat treatment on tensile fracture strain and associated failure modes were compared. Environment interactions were determined to often limit ductility, by promoting intergranular surface cracking. The response of various superalloys and heat treatments to slow strain rate tensile testing varied substantially, showing that composition and microstructure can significantly influence environmental resistance to cracking.

  9. Simulation investigation of tensile strained GeSn fin photodetector with Si(3)N(4) liner stressor for extension of absorption wavelength.

    PubMed

    Zhang, Qingfang; Liu, Yan; Yan, Jing; Zhang, Chunfu; Hao, Yue; Han, Genquan

    2015-01-26

    In this paper, we design a biaxial tensile strained GeSn photodetector with fin structure wrapped in Si(3)N(4) liner stressor. A large biaxial tensile strain is induced in GeSn fins by the expansion of Si(3)N(4) liner stressor. The distribution of tensile strain in GeSn fins was calculated by a finite element simulation. It is observed that magnitude of the strain increases with the reduction of fin thickness T(fin). Under the biaxial tensile strain, the direct band gap E(G,Γ) of GeSn fin photodetector is significantly reduced by lowering Γ conduction valley in energy and lifting of degeneracy of valence bands. As the 30 nm Si(3)N(4) liner stressor expanses by 1%, a E(G,Γ) reduction of ~0.14 eV is achieved in Ge(0.92)Sn(0.08) fins with a T(fin) of 100 nm. The cut-off wavelengths of strained Ge(0.96)Sn(0.04), Ge(0.92)Sn(0.08) and Ge(0.90)Sn(0.10) fin photodetectors with a T(fin) of 100 nm are extended to 2.4, 3.3, and 4 μm, respectively. GeSn fin photodetector integrated with Si(3)N(4) liner stressor provides an effective technique for extending the absorption edge of GeSn with Sn composition less than 10% to mid-infrared wavelength. PMID:25835833

  10. Temperature increase of Zircaloy-4 cladding tubes due to plastic heat dissipation during tensile tests at 0.1-10 s-1 strain rates

    NASA Astrophysics Data System (ADS)

    Hellouin de Menibus, Arthur; Auzoux, Quentin; Besson, Jacques; Crépin, Jérôme

    2014-11-01

    This study is focused on the impact of rapid Reactivity Initiated Accident (RIA) representative strain rates (about 1 s-1 NEA, 2010) on the behavior and fracture of unirradiated cold work stress relieved Zircaloy-4 cladding tubes. Uniaxial ring tests (HT) and plane strain ring tensile tests (PST) were performed in the 0.1-10 s-1 strain rate range, at 25 °C. The local temperature increase due to plastic dissipation was measured with a high-speed infrared camera. Limited temperature increases were measured at 0.1 s-1 strain rate. Limited but not strongly localized temperature increases were measured at 1 s-1. Large temperature increase were measured at 5 and 10 s-1 (142 °C at 5 s-1 strain rate in HT tests). The local temperature increase induced heterogeneous temperature fields, which enhanced strain localization and resulted in a reduction of the plastic elongation at fracture.

  11. Effect of tensile strain on grain connectivity and flux pinning in Bi2Sr2Ca2Cu3Ox tapes

    NASA Astrophysics Data System (ADS)

    van der Laan, D. C.; Ekin, J. W.; van Eck, H. J. N.; Dhallé, M.; ten Haken, B.; Davidson, M. W.; Schwartz, J.

    2006-01-01

    The grain-to-grain connectivity in Bi2Sr2Ca2Cu3Ox tapes is still poorly understood, even though they have been commercially available in long lengths for several years. This letter explains the effects of tensile strain on the grain-to-grain connectivity in Bi2Sr2Ca2Cu3Ox tapes. The different length scales at which damage to the grain structure occurs are studied with magneto-optical imaging, scanning-electron microscopy, and transport current. These data show that the initial degradation in critical current when strain exceeds the irreversible strain limit is caused by microcracks (˜100-500nm in width) that form mainly at high-angle grain boundaries. Filament-wide cracks (˜5-10μm in width) form at locations of lower grain density in the filaments at strains far exceeding the irreversible strain limit. However, in contrast to previous reports, a careful analysis of the pinning force as a function of tensile strain, taking into account current sharing with the normal matrix by using the offset criterion, shows that intragranular flux pinning is not affected by strain in any significant way.

  12. Mass Detection in Viscous Fluid Utilizing Vibrating Micro- and Nanomechanical Mass Sensors under Applied Axial Tensile Force.

    PubMed

    Stachiv, Ivo; Fang, Te-Hua; Jeng, Yeau-Ren

    2015-01-01

    Vibrating micro- and nanomechanical mass sensors are capable of quantitatively determining attached mass from only the first three (two) measured cantilever (suspended) resonant frequencies. However, in aqueous solutions that are relevant to most biological systems, the mass determination is challenging because the quality factor (Q-factor) due to fluid damping decreases and, as a result, usually just the fundamental resonant frequencies can be correctly identified. Moreover, for higher modes the resonance coupling, noise, and internal damping have been proven to strongly affect the measured resonances and, correspondingly, the accuracy of estimated masses. In this work, a technique capable of determining the mass for the cantilever and also the position of nanobeads attached on the vibrating micro-/nanomechanical beam under intentionally applied axial tensile force from the measured fundamental flexural resonant frequencies is proposed. The axial force can be created and controlled through an external electrostatic or magnetostatic field. Practicality of the proposed technique is confirmed on the suspended multi-walled carbon nanotube and the rectangular silicon cantilever-based mass sensors. We show that typically achievable force resolution has a negligibly small impact on the accuracy of mass measurement. PMID:26287190

  13. Mass Detection in Viscous Fluid Utilizing Vibrating Micro- and Nanomechanical Mass Sensors under Applied Axial Tensile Force

    PubMed Central

    Stachiv, Ivo; Fang, Te-Hua; Jeng, Yeau-Ren

    2015-01-01

    Vibrating micro- and nanomechanical mass sensors are capable of quantitatively determining attached mass from only the first three (two) measured cantilever (suspended) resonant frequencies. However, in aqueous solutions that are relevant to most biological systems, the mass determination is challenging because the quality factor (Q-factor) due to fluid damping decreases and, as a result, usually just the fundamental resonant frequencies can be correctly identified. Moreover, for higher modes the resonance coupling, noise, and internal damping have been proven to strongly affect the measured resonances and, correspondingly, the accuracy of estimated masses. In this work, a technique capable of determining the mass for the cantilever and also the position of nanobeads attached on the vibrating micro-/nanomechanical beam under intentionally applied axial tensile force from the measured fundamental flexural resonant frequencies is proposed. The axial force can be created and controlled through an external electrostatic or magnetostatic field. Practicality of the proposed technique is confirmed on the suspended multi-walled carbon nanotube and the rectangular silicon cantilever-based mass sensors. We show that typically achievable force resolution has a negligibly small impact on the accuracy of mass measurement. PMID:26287190

  14. Anterior cruciate ligament strain and tensile forces for weight-bearing and non-weight-bearing exercises: a guide to exercise selection.

    PubMed

    Escamilla, Rafael F; Macleod, Toran D; Wilk, Kevin E; Paulos, Lonnie; Andrews, James R

    2012-03-01

    There is a growing body of evidence documenting loads applied to the anterior cruciate ligament (ACL) for weight-bearing and non-weight-bearing exercises. ACL loading has been quantified by inverse dynamics techniques that measure anterior shear force at the tibiofemoral joint (net force primarily restrained by the ACL), ACL strain (defined as change in ACL length with respect to original length and expressed as a percentage) measured directly in vivo, and ACL tensile force estimated through mathematical modeling and computer optimization techniques. A review of the biomechanical literature indicates the following: ACL loading is generally greater with non-weight-bearing compared to weight-bearing exercises; with both types of exercises, the ACL is loaded to a greater extent between 10° to 50° of knee flexion (generally peaking between 10° and 30°) compared to 50° to 100° of knee flexion; and loads on the ACL change according to exercise technique (such as trunk position). Squatting with excessive forward movement of the knees beyond the toes and with the heels off the ground tends to increase ACL loading. Squatting and lunging with a forward trunk tilt tend to decrease ACL loading, likely due to increased hamstrings activity. During seated knee extension, ACL force decreases when the resistance pad is positioned more proximal on the anterior aspect of the lower leg, away from the ankle. The evidence reviewed as part of this manuscript provides objective data by which to rank exercises based on loading applied to the ACL. The biggest challenge in exercise selection post-ACL reconstruction is the limited knowledge of the optimal amount of stress that should be applied to the ACL graft as it goes through its initial incorporation and eventual maturation process. Clinicians may utilize this review as a guide to exercise selection and rehabilitation progression for patients post-ACL reconstruction. PMID:22387600

  15. Tensile Strain Effects on the Magneto-transport in Calcium Manganese Oxide Thin Films: Comparison with its Hole-doped Counterpart

    NASA Astrophysics Data System (ADS)

    Lawson, Bridget; Neubauer, Samuel; Chaudhry, Adeel; Hart, Cacie; Ferrone, Natalie; Houston, David; Yong, Grace; Kolagani, Rajeswari

    Magnetoresistance properties of the epitaxial thin films of doped rare earth manganites are known to be influenced by the effect of bi-axial strain induced by lattice mismatch with the substrate. In hole-doped manganites, the effect of both compressive and tensile strain is qualitatively consistent with the expected changes in unit cell symmetry from cubic to tetragonal, leading to Jahn-Teller strain fields that affect the energy levels of Mn3 + energy levels. Recent work in our laboratory on CaMnO3 thin films has pointed out that tetragonal distortions introduced by tensile lattice mismatch strain may also have the effect of modulating the oxygen content of the films in agreement with theoretical models that propose such coupling between strain and oxygen content. Our research focuses on comparing the magneto-transport properties of hole-doped manganite LaCaMnO3 thin films with that of its electron doped counter parts, in an effort to delineate the effects of oxygen stoichiometry changes on magneto-transport from the effects of Jahn-Teller type strain. Towson University Office of Undergraduate Research, Fisher Endowment Grant and Undergraduate Research Grant from the Fisher College of Science and Mathematics, Seed Funding Grant from the School of Emerging technologies and the NSF Grant ECCS 112856.

  16. The Effect of Gradations in Mineral Content, Matrix Alignment, and Applied Strain on Human Mesenchymal Stem Cell Morphology within Collagen Biomaterials.

    PubMed

    Mozdzen, Laura C; Thorpe, Stephen D; Screen, Hazel R C; Harley, Brendan A C

    2016-07-01

    The tendon-bone junction is a unique, mechanically dynamic, structurally graded anatomical zone, which transmits tensile loads between tendon and bone. Current surgical repair techniques rely on mechanical fixation and can result in high re-failure rates. A new class of collagen biomaterial that contains discrete mineralized and structurally aligned regions linked by a continuous interface to mimic the graded osteotendinous insertion has been recently described. Here the combined influence of graded biomaterial environment and increasing levels of applied strain (0%-20%) on mesenchymal stem cell (MSC) orientation and alignment have been reported. In osteotendinous scaffolds, which contain opposing gradients of mineral content and structural alignment characteristic of the native osteotendinous interface, MSC nuclear, and actin alignment is initially dictated by the local pore architecture, while applied tensile strain enhances cell alignment in the direction of strain. Comparatively, in layered scaffolds that do not contain any structural alignment cues, MSCs are randomly oriented in the unstrained condition, then become oriented in a direction perpendicular to applied strain. These findings provide an initial understanding of how scaffold architecture can provide significant, potentially competitive, feedback influencing MSC orientation under applied strain, and form the basis for future tissue engineering efforts to regenerate the osteotendinous enthesis. PMID:27245787

  17. Characterization of Damage in Triaxial Braid Composites Under Tensile Loading

    NASA Technical Reports Server (NTRS)

    Littell, Justin D.; Binienda, Wieslaw K.; Roberts, Gary D.; Goldberg, Robert K.

    2009-01-01

    Carbon fiber composites utilizing flattened, large tow yarns in woven or braided forms are being used in many aerospace applications. Their complex fiber architecture and large unit cell size present challenges in both understanding deformation processes and measuring reliable material properties. This report examines composites made using flattened 12k and 24k standard modulus carbon fiber yarns in a 0 /+60 /-60 triaxial braid architecture. Standard straight-sided tensile coupons are tested with the 0 axial braid fibers either parallel with or perpendicular to the applied tensile load (axial or transverse tensile test, respectively). Nonuniform surface strain resulting from the triaxial braid architecture is examined using photogrammetry. Local regions of high strain concentration are examined to identify where failure initiates and to determine the local strain at the time of initiation. Splitting within fiber bundles is the first failure mode observed at low to intermediate strains. For axial tensile tests splitting is primarily in the 60 bias fibers, which were oriented 60 to the applied load. At higher strains, out-of-plane deformation associated with localized delamination between fiber bundles or damage within fiber bundles is observed. For transverse tensile tests, the splitting is primarily in the 0 axial fibers, which were oriented transverse to the applied load. The initiation and accumulation of local damage causes the global transverse stress-strain curves to become nonlinear and causes failure to occur at a reduced ultimate strain. Extensive delamination at the specimen edges is also observed.

  18. Observation of heavy- and light-hole split direct bandgap photoluminescence from tensile-strained GeSn (0.03% Sn)

    NASA Astrophysics Data System (ADS)

    Harris, Thomas R.; Yeo, Yung Kee; Ryu, Mee-Yi; Beeler, Richard T.; Kouvetakis, John

    2014-09-01

    Temperature- (T-) and laser power-dependent photoluminescence (PL) measurements have been made for the tensile-strained, undoped GeSn (0.03% Sn) film grown on Si substrate. The PL results show not only clear strain-split direct bandgap transitions to the light-hole (LH) and heavy-hole (HH) bands at energies of 0.827 and 0.851 eV at 10 K, respectively, but also clearly show both strong direct and indirect bandgap related PL emissions at almost all temperatures, which are rarely observed. This split of PL emissions can be directly observed only at low T and moderate laser power, and the two PL peaks merge into one broad PL peak at room temperature, which is mainly due to the HH PL emission rather than LH transition. The evolution of T-dependent PL results also clearly show the competitive nature between the direct and indirect bandgap related PL transitions as T changes. The PL analysis also indicates that the energy gap reduction in Γ valley could be larger, whereas the bandgap reduction in L valley could be smaller than the theory predicted. As a result, the separation energy between Γ and L valleys (˜86 meV at 300 K) is smaller than theory predicted (125 meV) for this Ge-like sample, which is mainly due to the tensile strain. This finding strongly suggests that the indirect-to-direct bandgap transition of Ge1-ySny could be achieved at much lower Sn concentration than originally anticipated if one utilizes the tensile strain properly. Thus, Ge1-ySny alloys could be attractive materials for the fabrication of direct bandgap Si-based light emitting devices.

  19. Elevated temperature tensile properties of irradiated 20/25/Nb stainless steel fuel pin cladding at low and high strain rates

    NASA Astrophysics Data System (ADS)

    Gravenor, J. G.; Douglas, J.

    1988-09-01

    Tensile specimens were prepared from 20/25/Nb stainless steel fuel pin cladding irradiated in a Commercial Advanced Gas-cooled Reactor (CAGR) at temperatures in the range 622-866 K and integrated fast neutron doses up to 16 × 10 24n/ m2. The tests were performed in air at temperatures in the range 298-873 K at strain rates from 2 × 10 -5s-1 to 7.2 s -1. The tensile properties varied with irradiation temperature, test temperature and strain rate. At lower irradiation temperature, strengthening produced by fast neutron damage was accompanied by reduced elongation. Strengthening was also observed at higher irradiation temperatures, possibly due to precipitation phenomena. The maximum irradiation embrittlement was observed in tests at 873 K at low strain rates between 2 × 10 -4s-1 and 2 × 10 -5s-1. The failure mode of embrittled specimens irradiated at higher temperatures was characterized by prematurely ruptured ductile fibres, rather than by intergranular cracking.

  20. Increased molecular mobility in humid silk fibers under tensile stress

    NASA Astrophysics Data System (ADS)

    Seydel, Tilo; Knoll, Wiebke; Greving, Imke; Dicko, Cedric; Koza, Michael M.; Krasnov, Igor; Müller, Martin

    2011-01-01

    Silk fibers are semicrystalline nanocomposite protein fibers with an extraordinary mechanical toughness that changes with humidity. Diffusive or overdamped motion on a molecular level is absent in dry silkworm silk, but present in humid silk at ambient temperature. This microscopic diffusion distinctly depends on the externally applied macroscopic tensile force. Quasielastic and inelastic neutron-scattering data as a function of humidity and of tensile strain on humid silk fibers support the model that both the adsorbed water and parts of the amorphous polymers participate in diffusive motion and are affected by the tensile force. It is notable that the quasielastic linewidth of humid silk at 100% relative humidity increases significantly with the applied force. The effect of the tensile force is discussed in terms of an increasing alignment of the polymer chains in the amorphous fraction with increasing tensile stress which changes the geometrical restrictions of the diffusive motions.

  1. High-speed tensile test instrument

    NASA Astrophysics Data System (ADS)

    Mott, P. H.; Twigg, J. N.; Roland, D. F.; Schrader, H. S.; Pathak, J. A.; Roland, C. M.

    2007-04-01

    A novel high-speed tensile test instrument is described, capable of measuring the mechanical response of elastomers at strain rates ranging from 10 to 1600 s-1 for strains through failure. The device employs a drop weight that engages levers to stretch a sample on a horizontal track. To improve dynamic equilibrium, a common problem in high speed testing, equal and opposite loading was applied to each end of the sample. Demonstrative results are reported for two elastomers at strain rates to 588 s-1 with maximum strains of 4.3. At the higher strain rates, there is a substantial inertial contribution to the measured force, an effect unaccounted for in prior works using the drop weight technique. The strain rates were essentially constant over most of the strain range and fill a three-decade gap in the data from existing methods.

  2. Microcracking damage and the fracture process in relation to strain rate in human cortical bone tensile failure.

    PubMed

    Zioupos, Peter; Hansen, Ulrich; Currey, John D

    2008-10-20

    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 effect of strain rate 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 strain rates (epsilon ) ranging from low (0.08s(-1)) to high (18s(-1)). Across this strain rate range the modulus of elasticity generally increased, stress at yield and failure and strain at failure decreased for rates higher than 1s(-1), while strain at yield was invariant for most strain rates and only decreased at rates higher than 10s(-1). The results showed that strain rate has a stronger effect on post-yield deformation than on initiation of macroscopic yielding. In general, specimens loaded at high strain rates were brittle, while those loaded at low strain rates were much tougher. Here, a post-test examination of the microcracking damage reveals that microcracking was inversely related to the strain rate. Specimens loaded at low strain rates showed considerable post-yield strain and also much more microcracking. Partial correlation and regression analysis suggested that the development of post-yield strain was a function of the amount of microcracking incurred (the cause), rather than being a direct result of the strain rate (the excitation). Presumably low strain rates 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

  3. 1.55 µm spot-size converter integrated polarization-insensitive quantum-well semiconductor optical amplifier with tensile-strained barriers

    NASA Astrophysics Data System (ADS)

    Ma, Hong; Chen, Sihai; Yi, Xinjian; Zhu, Guangxi

    2004-07-01

    A 1.55 µm polarization-insensitive lateral tapered spot-size converter integrated semiconductor optical amplifier (SSC-SOA) with tensile-strained barriers was investigated. The optical amplifier structure used a conventional ridge guide for the active layers and a second larger ridge for the passive waveguide. Low beam divergence of 12° × 15° results in about 3.1 dB coupling losses with -1 dB positional tolerances of ±2.3 µm and ±1.6 µm in horizontal and vertical directions using an anti-reflection coated flat-ended single-mode fibre. The active layer of SSC-SOA consisted of a tensile-strained barrier multiple-quantum-well structure. The SSC-SOA exhibited a signal gain of 25.5 dB and a saturation output power of 11.2 dB m with excellent polarization insensitivity (less than 0.5 dB) at 200 mA.

  4. Effects of tensile strain on the peculiarities of PEO penetration into the nanoporous structure of PET deformed via the crazing mechanism.

    PubMed

    Rukhlya, E G; Yarysheva, L M; Volynskii, A L; Bakeev, N F

    2016-04-14

    Solvent crazing involves the development of a highly dispersed fibrillar-porous structure with dimensions of pores and craze fibrils of about 2-20 nm, and crazing by itself can be treated as a universal method for the development of nanoscale porosity. The penetration and release of poly(ethylene oxide) macromolecules into and from the crazes during the development of the nanoporous structure of poly(ethylene terephthalate) have been studied. In particular, PET has been deformed in dilute or semidilute (unentangled as well as entangled) solutions of PEO (a Mw of 4 and 40 kDa) via the mechanism of solvent crazing. Hydrodynamic coil radii Rh, blob sizes ξ, and concentration ranges (crossover and entanglement concentrations) have been determined for the PEO solutions. The evolution of the craze structure (change in porosity W and pore diameters d) has been described as a function of the tensile strain of PET during its drawing in an adsorption-active medium and in the PEO solutions. PEO has been shown to penetrate into the nanoporous structure of the crazes under the conditions corresponding to Rh≤d and ξ < d. It has been shown that coagulation processes in the structure of crazed PET, PEO adsorption at the highly developed surface of PET, and the mechanism of PEO transport in the nanopores are equally important factors affecting the direction of the macromolecule mass transfer in the nanopores (penetration or release) and PEO content variation as a function of PET tensile strain. PMID:26979240

  5. Influence of the tensile strain rate on the mechanical properties and phase composition of VNS 9-Sh TRIP steel

    NASA Astrophysics Data System (ADS)

    Terent'ev, V. F.; Slizov, A. K.; Prosvirnin, D. V.; Sirotinkin, V. P.; Ashmarin, A. A.; Gol'dberg, M. A.

    2015-10-01

    The influence of the strain rate on the mechanical properties and the phase composition of a sheet VNS 9-Sh (23Kh15N5AM3-Sh) TRIP steel is studied during static tension. The strain rate is changed in the range from 8.3 × 10-5 to 25 × 10-3 s-1. The dependence of the mechanical properties on the strain rate is found to be nonlinear. The TRIP effect is most pronounced at a strain rate of (8.3-17) × 10-5 s-1. In this strain rate, the deformation martensite content increases significantly, from 50 to 87%, as is detected by X-ray diffraction.

  6. Controlled rippling of graphene via irradiation and applied strain modify its mechanical properties: a nanoindentation simulation study.

    PubMed

    Martinez-Asencio, J; Ruestes, C J; Bringa, E M; Caturla, M J

    2016-05-18

    Ripples present in free standing graphene have an important influence on the mechanical behavior of this two-dimensional material. In this study, we show through nanoindentation simulations, how out-of-plane displacements can be modified by strain, resulting in softening of the membrane under compression and stiffening under tension. Irradiation also induces changes in the mechanical properties of graphene. Interestingly, compressed samples, irradiated at low doses are stiffened by the irradiation, whereas the samples under tensile strain do not show significant changes in their mechanical properties. These simulations indicate that vacancies produced by the energetic ions cannot be the ones directly responsible for this behavior. However, changes in roughness induced by the momentum transferred from the energetic ions to the membrane, can explain these differences. These results provide an alternative explanation to recent experimental observations of the stiffening of graphene under low dose irradiation, as well as the paths to tailor the mechanical properties of this material via applied strain and irradiation. PMID:27145734

  7. Lattice strain and damage evolution of 9-12/%Cr ferritic/martensitic steel during in situ tensile test by x-ray diffraction and small angle scattering.

    SciTech Connect

    Pan, X.; Wu, X.; Mo, K.; Chen, X,; Almer, J. D.; Ilavsky, J.; Haeffner, D. R.; Stubbins, J. F.; X-Ray Science Division; Univ. of Illinois

    2010-01-01

    In situ X-ray diffraction and small angle scattering measurements during tensile tests were performed on 9-12% Cr ferritic/martensitic steels. The lattice strains in both particle and matrix phases, along two principal directions, were directly measured. The load transfer between particle and matrix was calculated based on matrix/particle elastic mismatch, matrix plasticity and interface decohesion. In addition, the void or damage evolution during the test was measured using small angle X-ray scattering. By combining stress and void evolution during deformation, the critical interfacial strength for void nucleation was determined, and compared with pre-existing void nucleation criteria. These comparisons show that models overestimate the measured critical strength, and require a larger particle size than measured to match the X-ray observations.

  8. Enhancement of photoluminescence from n-type tensile-strained GeSn wires on an insulator fabricated by lateral liquid-phase epitaxy

    NASA Astrophysics Data System (ADS)

    Shimura, Takayoshi; Matsue, Masahiro; Tominaga, Kohei; Kajimura, Keiko; Amamoto, Takashi; Hosoi, Takuji; Watanabe, Heiji

    2015-11-01

    We investigated the optical properties of undoped and n-type GeSn wires fabricated by a lateral liquid-phase epitaxial method. The Sn concentration was approximately 0.5% in the region from the seed to near the wire end. Moreover, the Sn concentration increased to 6% at the wire end, whereas Si diffusion from the seed was enhanced and extended to 200 μm from the seed. Tensile strain gradually decreased from 0.5% close the seed to 0.25% at the wire end. The photoluminescence (PL) peak was red-shifted by Sn incorporation into the Ge wires, and a PL peak at 0.66 eV was observed from the wire end. Upon n-type doping, the PL intensity of the GeSn layers was significantly enhanced to approximately 10 times higher than that of the undoped GeSn wires.

  9. Release of Tensile Strain on Engineered Human Tendon Tissue Disturbs Cell Adhesions, Changes Matrix Architecture, and Induces an Inflammatory Phenotype

    PubMed Central

    Bayer, Monika L.; Schjerling, Peter; Herchenhan, Andreas; Zeltz, Cedric; Heinemeier, Katja M.; Christensen, Lise; Krogsgaard, Michael; Gullberg, Donald; Kjaer, Michael

    2014-01-01

    Mechanical loading of tendon cells results in an upregulation of mechanotransduction signaling pathways, cell-matrix adhesion and collagen synthesis, but whether unloading removes these responses is unclear. We investigated the response to tension release, with regard to matrix proteins, pro-inflammatory mediators and tendon phenotypic specific molecules, in an in vitro model where tendon-like tissue was engineered from human tendon cells. Tissue sampling was performed 1, 2, 4 and 6 days after surgical de-tensioning of the tendon construct. When tensile stimulus was removed, integrin type collagen receptors showed a contrasting response with a clear drop in integrin subunit α11 mRNA and protein expression, and an increase in α2 integrin mRNA and protein levels. Further, specific markers for tendon cell differentiation declined and normal tendon architecture was disturbed, whereas pro-inflammatory molecules were upregulated. Stimulation with the cytokine TGF-β1 had distinct effects on some tendon-related genes in both tensioned and de-tensioned tissue. These findings indicate an important role of mechanical loading for cellular and matrix responses in tendon, including that loss of tension leads to a decrease in phenotypical markers for tendon, while expression of pro-inflammatory mediators is induced. PMID:24465881

  10. The tensile deformation behavior of nuclear-grade isotropic graphite posterior to hydrostatic loading

    NASA Astrophysics Data System (ADS)

    Yoda, S.; Eto, M.

    1983-10-01

    The effects of prehydrostatic loading on microstructural changes and tensile deformation behavior of nuclear-grade isotropic graphite have been examined. Scanning electron micrographs show that formation of microcracks associated with delamination between basal planes occurs under hydrostatic loading. Hydrostatic loading on specimens results in the decrease in tensile strength and increase in residual strain generated by the applied tensile stress at various levels, indicating that the graphite material is weakened by hydrostatic loading. A relationship between residual strain and applied tensile stress for graphite hydrostatically-loaded at several pressure levels can be approximately expressed as ɛ = ( AP + B) σn over a wide range hydrostatic pressure, where ɛ, P and σ denote residual strain, hydrostatic pressure and applied tensile stress, respectively; A, B and n are constants. The effects of prehydrostatic loading on the tensile stress-strain behavior of the graphite were examined in more detail. The ratio of stress after hydrostatic loading to that before hydrostatic loading on the stress-strain relationship remains almost unchanged irrespective of strain.

  11. Tuning magnetism of monolayer MoS{sub 2} by doping vacancy and applying strain

    SciTech Connect

    Zheng, Huiling; Yang, Baishun; Han, Ruilin; Du, Xiaobo; Yan, Yu; Wang, Dingdi

    2014-03-31

    In view of important role of inducing and manipulating the magnetism in two-dimensional materials for the development of low-dimensional spintronic devices, the influences of strain on electronic structure and magnetic properties of commonly observed vacancies doped monolayer MoS{sub 2} are investigated using first-principles calculations. It is shown that unstrained V{sub S}, V{sub S2}, and V{sub MoS3} doped monolayer MoS{sub 2} systems are nonmagnetic, while the ground state of unstrained V{sub MoS6} doped system is magnetic and the magnetic moment is contributed mainly by six Mo atoms around V{sub MoS6}. In particular, tensile strain can induce magnetic moments in V{sub S}, V{sub S2}, and V{sub MoS3} doped monolayer MoS{sub 2} due to the breaking of Mo–Mo metallic bonds around the vacancies, while the magnetization induced by V{sub MoS6} can be effectively manipulated by equibiaxial strain due to the change of Mo–Mo metallic bonds around V{sub MoS6} under strains.

  12. Coexistent compressive and tensile strain in Ag thin films on Si(1 1 1)-(7×7) surfaces

    NASA Astrophysics Data System (ADS)

    Goswami, D. K.; Bhattacharjee, K.; Satpati, B.; Roy, S.; Kuri, G.; Satyam, P. V.; Dev, B. N.

    2007-09-01

    Growth and strain behavior of thin Ag films on Si substrates have been investigated by scanning tunneling microscopy, cross-sectional transmission electron microscopy and high resolution X-ray diffraction studies. Ag islands formed on Si at room temperature growth show strongly preferred heights and flat top. At low coverage [ ≳1 monolayer (ML)], Ag islands with (1 1 1) orientation containing two atomic layers of Ag are overwhelmingly formed [D.K. Goswami, K. Bhattacharjee, B. Satpati, S. Roy, P.V. Satyam, B.N. Dev, Surf. Sci. 601 (2007) 603]. A thicker (40 ML) annealed film shows two closely spaced Ag(1 1 1) diffraction peaks—one weak and broad and the other narrow and more intense. The broad peak corresponds to an average expansion (0.21%) and the narrow intense peak corresponds to a contraction (0.17%) of the Ag(1 1 1) planar spacing compared to the bulk value. This coexistence of compressive and tensile strain can be explained in terms of changes in the Ag lattice during the heating-cooling cycle due to thermal expansion coefficient mismatch between Ag and Si.

  13. Effect of Biaxial Stretching at Temperatures and Strain Histories Comparable to Injection Stretch Blow Moulding on Tensile Modulus for Polyethylene Terephthalate (PET)

    NASA Astrophysics Data System (ADS)

    Tan, C. W.; Menary, G. H.; Harkin-Jones, E. M. A.; Armstrong, C. G.; Martin, P. J.

    2007-04-01

    This study is particularly relevant to the injection stretch blow moulding (ISBM) process where PET material is typically biaxially stretched to form bottles for the water and carbonated soft drinks industry. The aim of this paper is to investigate the effect of biaxial stretching on the mechanical properties of Polyethylene Terephthalate (PET) using a custom built biaxial testing machine. An initially amorphous PET sample was prepared via injection moulding to form a square sample (76mm × 76mm) suitable for stretching on the machine. This sample was then subjected to a series of biaxial tests (simultaneous and sequential) within a temperature range between 85°C and 110 °C, strain rates in the range of 1s-1 to 32s-1 and stretch ratios in the range of 1.5 to 3. Specimens were subsequently cut from the biaxial stretched sheets and used to measure the tensile modulus. Results showed that there is almost no effect found for strain rate and temperature on modulus development whilst stretch ratio and mode of deformation played the most important role on modulus development on PET under biaxial deformation.

  14. Resistance-foil strain-gage technology as applied to composite materials

    NASA Technical Reports Server (NTRS)

    Tuttle, M. E.; Brinson, H. F.

    1984-01-01

    A general review of existing strain-gage technologies as applied to orthotropic-composite materials is given. The specific topics addressed are gage-bonding procedures, transverse-sensitivity effects, errors due to gage misalignment, and temperature-compensation methods. The discussion is supplemented by numerical examples where appropriate. It is shown that the orthotropic behavior of composites can result in experimental error which would not be expected based on practical experience with isotropic materials. In certain cases, the transverse sensitivity of strain gages and/or slight gage misalignment can result in strain-measurement errors exceeding 50 percent.

  15. Stress reduction in an isotropic plate with a hole by applied induced strains

    NASA Technical Reports Server (NTRS)

    Sensharma, Pradeep K.; Palantera, Markku J.; Haftka, Raphael T.

    1992-01-01

    Recently there has been much interest in adaptive structures that can respond to a varying environment by changing their properties. Shape memory alloys and piezoelectric materials can be used as induced strain actuators to reduce stresses in the regions of stress concentration. The objective of the work was to find the maximum possible reduction in the stress concentration factor in an isotropic plate with a hole by applying induced strains in a small area near the hole. Induced strains were simulated by thermal expansion.

  16. Tumor Necrosis Factor α–Dependent Proinflammatory Gene Induction Is Inhibited by Cyclic Tensile Strain in Articular Chondrocytes In Vitro

    PubMed Central

    Long, Ping; Gassner, Robert; Agarwal, Sudha

    2016-01-01

    Objective To understand the intracellular mechanisms of the action of mechanical strain on articular chondrocytes during inflammation. Methods One of the major mediators responsible for cartilage destruction in inflamed articular joints is tumor necrosis factor α (TNFα). Therefore, in this study we examined the intracellular mechanisms of actions of cyclic tensile strain (CTS) on the recombinant human TNFα (rHuTNFα)–induced proinflammatory pathways in primary cultures of chondrocytes. The expression of messenger RNA (mRNA) for TNFα-dependent proinflammatory proteins was examined by semiquantitative reverse transcriptase–polymerase chain reaction. The synthesis of proinflammatory proteins was examined by Western blot analysis in cell extracts, followed by semiquantitative measurement of bands using densitometric analysis. Nitric oxide production was measured by Griess reaction, and prostaglandin E2 production was assessed by radioimmunoassays. The proteoglycan synthesis in chondrocytes was assessed by incorporation of Na235SO4 in chondroitin sulfate proteoglycans. Results By exposing chondrocytes to CTS in the presence of TNFα in vitro, we showed that CTS is an effective antagonist of TNFα actions and acts as both an antiinflammatory signal and a reparative signal. CTS of low magnitude suppresses TNFα-induced mRNA expression of multiple proinflammatory proteins involved in catabolic responses, such as inducible nitric oxide synthase, cyclooxygenase 2, and collagenase. CTS also counteracts cartilage degradation by augmenting induction of tissue inhibitor of metalloproteinase 2. Additionally, CTS augments the reparative process via abrogation of TNFα-induced suppression of proteoglycan synthesis. Nonetheless, CTS acts on chondrocytes in a TNFα-dependent manner, since exposure of chondrocytes to CTS alone had no effect on these parameters. Conclusion CTS of low magnitude acts as an effective antagonist of TNFα not only by inhibiting the TNF

  17. Tensile Fracture of Ductile Materials. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Pai, D. M.

    1984-01-01

    For brittle materials, circular voids play an important role relative to fracture, intensifing both tensile and compressive stresses. A maximum intensified tensile stress failure criterion applies quite well to brittle materials. An attempt was made to explore the possibility of extending the approach to the tensile fracture of ductile materials. The three dimensional voids that exist in reality are modelled by circular holes in sheet metal. Mathematical relationships are sought between the shape and size of the hole, after the material is plastically deformed, and the amount of deformation induced. Then, the effect of hole shape, size and orientation on the mechanical properties is considered experimentally. The presence of the voids does not affect the ultimate tensile strength of the ductile materials because plastic flow wipes out the stress intensification caused by them. However, the shape and orientation of the defect is found to play an important role in affecting the strain at fracture.

  18. Elastic-plastic strain acceptance criterion for structures subject to rapidly applied transient dynamic loading

    SciTech Connect

    Solonick, W.

    1996-11-01

    Rapidly applied transient dynamic loads produce stresses and deflections in structures that typically exceed those from static loading conditions. Previous acceptance criteria for structures designed for rapidly applied transient dynamic loading limited stresses to those determined from elastic analysis. Different stress limits were established for different grades of structure depending upon the amount of permanent set considered acceptable. Structure allowed to sustain very limited permanent set is designed to stress limits not significantly greater than yield stress. Greater permanent set in structure under rapidly applied transient dynamic loading conditions is permitted by establishing stress limits that are significantly greater than yield stress but still provide adequate safety margin (with respect to failure). This paper presents a strain-based elastic-plastic (i.e., inelastic) analysis criterion developed as an alternative to the more conservative stress-based elastic analysis stress criterion for structures subjected to rapidly applied transient dynamic loading. The strain limits established are based on a fraction of the strain at ultimate stress obtained from an engineering stress/strain curve of the material. Strains limits are categorized by type as membrane or surface and by region as general, local, or concentrated. The application of the elastic-plastic criterion provides a more accurate, less conservative design/analysis basis for structures than that used in elastic stress-based analysis criteria, while still providing adequate safety margins.

  19. Elastic-Plastic Strain Acceptance Criteria for Structures Subject to Rapidly Applied Transient Dynamic Loading

    SciTech Connect

    W.R. Solonick

    2003-04-01

    Rapidly applied transient dynamic loads produce stresses and deflections in structures that typically exceed those from static loading conditions. Previous acceptance criteria for structures designed for rapidly applied transient dynamic loading limited stresses to those determined from elastic analysis. Different stress limits were established for different grades of structure depending upon the amount of permanent set considered acceptable. Structure allowed to sustain very limited permanent set is designed to stress limits not significantly greater than yield stress. Greater permanent set in structure under rapidly applied transient dynamic loading conditions is permitted by establishing stress limits that are significantly greater than yield stress but still provide adequate safety margin (with respect to failure). This paper presents a strain-based elastic-plastic (i.e., inelastic) analysis criterion developed as an alternative to the more conservative stress-based elastic analysis stress criterion for structures subjected to rapidly applied transient dynamic loading. The strain limits established are based on material ductility considerations only and are set as a fraction of the strain at ultimate stress obtained from an engineering stress/strain curve of the material. Strains limits are categorized by type as membrane or surface and by region as general, local , or concentrated. The application of the elastic-plastic criterion provides a more accurate, less conservative design/analysis basis for structures than that used in elastic stress-based analysis criteria, while still providing adequate safety margins.

  20. Reflectance difference laser measurements applied to the study of the stress/strain state in materials

    NASA Astrophysics Data System (ADS)

    Saucedo-Zárate, Carlos H.; López-López, Maximo; Sánchez-López, Carlos; Correa-Figueroa, Jose Luis; Huerta-Ruelas, Jorge A.

    2009-09-01

    Development of experimental setup to study strain/stress state in materials emerges from a need to evaluate by a nondestructive and non-invasive technique the performance in new materials like semiconductor heterostructures, composite materials and alloys. The system was designed and built to be used as a multi-functional experimental setup. The main purpose is to characterize materials in elastic and plastic regime by reflectance difference laser measurements and strain gages. This system allows the generalization of results obtained from a theoretical model based in Finite Element Model and experimental measurements taken in finite specific points with strain gages. A NI™ platform is used for signal conditioning and processing. System built is described which includes an optical setup to measure reflectance difference laser (RDL), and a flexor which applies deformation in a link, with a micrometer. A correlation bigger than 0.95 was found between optical signal, strain gage signal, and finite element modeling.

  1. Effect of uniaxial tensile stress on the isomer shift of 57Fe in fcc stainless steels

    NASA Astrophysics Data System (ADS)

    Ratner, E.; Ron, M.

    1982-05-01

    The electron wave-function response to uniaxial tensile stress in fcc steels (SS310 and SS316) was investigated through the isomer shift of the Mössbauer effect. Stresses up to 12 kbar (the ultimate tensile stress is approximately 14 kbar) were applied at room temperature. The isomer shift changes linearly in these circumstances. It is concluded that, as in the case of hydrostatic pressure, the paramount factor here is the volume strain of the wave functions of 4S electrons.

  2. A new approach for structural health monitoring by applying anomaly detection on strain sensor data

    NASA Astrophysics Data System (ADS)

    Trichias, Konstantinos; Pijpers, Richard; Meeuwissen, Erik

    2014-03-01

    Structural Health Monitoring (SHM) systems help to monitor critical infrastructures (bridges, tunnels, etc.) remotely and provide up-to-date information about their physical condition. In addition, it helps to predict the structure's life and required maintenance in a cost-efficient way. Typically, inspection data gives insight in the structural health. The global structural behavior, and predominantly the structural loading, is generally measured with vibration and strain sensors. Acoustic emission sensors are more and more used for measuring global crack activity near critical locations. In this paper, we present a procedure for local structural health monitoring by applying Anomaly Detection (AD) on strain sensor data for sensors that are applied in expected crack path. Sensor data is analyzed by automatic anomaly detection in order to find crack activity at an early stage. This approach targets the monitoring of critical structural locations, such as welds, near which strain sensors can be applied during construction and/or locations with limited inspection possibilities during structural operation. We investigate several anomaly detection techniques to detect changes in statistical properties, indicating structural degradation. The most effective one is a novel polynomial fitting technique, which tracks slow changes in sensor data. Our approach has been tested on a representative test structure (bridge deck) in a lab environment, under constant and variable amplitude fatigue loading. In both cases, the evolving cracks at the monitored locations were successfully detected, autonomously, by our AD monitoring tool.

  3. Mechanical strain applied to human fibroblasts differentially regulates skeletal myoblast differentiation.

    PubMed

    Hicks, Michael R; Cao, Thanh V; Campbell, David H; Standley, Paul R

    2012-08-01

    Cyclic short-duration stretches (CSDS) such as those resulting from repetitive motion strain increase the risk of musculoskeletal injury. Myofascial release is a common technique used by clinicians that applies an acyclic long-duration stretch (ALDS) to muscle fascia to repair injury. When subjected to mechanical strain, fibroblasts within muscle fascia secrete IL-6, which has been shown to induce myoblast differentiation, essential for muscle repair. We hypothesize that fibroblasts subjected to ALDS following CSDS induce myoblast differentiation through IL-6. Fibroblast conditioned media and fibroblast-myoblast cocultures were used to test fibroblasts' ability to induce myoblast differentiation. The coculture system applies strain to fibroblasts only but still allows for diffusion of potential differentiation mediators to unstrained myoblasts on coverslips. To determine the role of IL-6, we utilized myoblast unicultures ± IL-6 (0-100 ng/ml) and cocultures ± α-IL-6 (0-200 μg/ml). Untreated uniculture myoblasts served as a negative control. After 96 h, coverslips (n = 6-21) were microscopically analyzed and quantified by blinded observer for differentiation endpoints: myotubes per square millimeter (>3 nuclei/cell), nuclei/myotube, and fusion efficiency (%nuclei within myotubes). The presence of fibroblasts and fibroblast conditioned media significantly enhanced myotube number (P < 0.05). However, in coculture, CSDS applied to fibroblasts did not reproduce this effect. ALDS following CSDS increased myotube number by 78% and fusion efficiency by 96% vs. CSDS alone (P < 0.05). Fibroblasts in coculture increase IL-6 secretion; however, IL-6 secretion did not correlate with enhanced differentiation among strain groups. Exogenous IL-6 in myoblast uniculture failed to induce differentiation. However, α-IL-6 attenuated differentiation in all coculture groups (P < 0.05). Fibroblasts secrete soluble mediators that have profound effects on several measures of myoblast

  4. Mechanical strain applied to human fibroblasts differentially regulates skeletal myoblast differentiation

    PubMed Central

    Hicks, Michael R.; Cao, Thanh V.; Campbell, David H.

    2012-01-01

    Cyclic short-duration stretches (CSDS) such as those resulting from repetitive motion strain increase the risk of musculoskeletal injury. Myofascial release is a common technique used by clinicians that applies an acyclic long-duration stretch (ALDS) to muscle fascia to repair injury. When subjected to mechanical strain, fibroblasts within muscle fascia secrete IL-6, which has been shown to induce myoblast differentiation, essential for muscle repair. We hypothesize that fibroblasts subjected to ALDS following CSDS induce myoblast differentiation through IL-6. Fibroblast conditioned media and fibroblast-myoblast cocultures were used to test fibroblasts' ability to induce myoblast differentiation. The coculture system applies strain to fibroblasts only but still allows for diffusion of potential differentiation mediators to unstrained myoblasts on coverslips. To determine the role of IL-6, we utilized myoblast unicultures ± IL-6 (0–100 ng/ml) and cocultures ± α-IL-6 (0–200 μg/ml). Untreated uniculture myoblasts served as a negative control. After 96 h, coverslips (n = 6–21) were microscopically analyzed and quantified by blinded observer for differentiation endpoints: myotubes per square millimeter (>3 nuclei/cell), nuclei/myotube, and fusion efficiency (%nuclei within myotubes). The presence of fibroblasts and fibroblast conditioned media significantly enhanced myotube number (P < 0.05). However, in coculture, CSDS applied to fibroblasts did not reproduce this effect. ALDS following CSDS increased myotube number by 78% and fusion efficiency by 96% vs. CSDS alone (P < 0.05). Fibroblasts in coculture increase IL-6 secretion; however, IL-6 secretion did not correlate with enhanced differentiation among strain groups. Exogenous IL-6 in myoblast uniculture failed to induce differentiation. However, α-IL-6 attenuated differentiation in all coculture groups (P < 0.05). Fibroblasts secrete soluble mediators that have profound effects on several measures of

  5. Static and dynamic tensile behaviour of aluminium processed by high pressure torsion

    NASA Astrophysics Data System (ADS)

    Verleysen, Patricia; Oelbrandt, Wouter; Naghdy, Soroosh; Kestens, Leo

    2015-09-01

    High pressure torsion (HPT) is a severe plastic deformation technique in which a small, disk-like sample is subjected to a torsional deformation under a high hydrostatic pressure. In present study, the static and dynamic tensile behaviour of commercially pure aluminium (99.6 wt%) processed by HPT is studied. The high strain rate tensile behaviour is characterized using a purpose-developed miniature split Hopkinson tensile bar setup by which strain rates up to 5 × 103 s-1 can be reached. During the tests, the deformation of a speckle pattern applied to the samples is recorded, by which local information on the strain is obtained using a digital image correlation technique. Electron back scatter diffraction images are used to investigate the microstructural evolution, more specifically the grain refinement obtained by HPT. The fracture surfaces of the tensile samples are studied by scanning electron microscopy. Results show that the imposed severe plastic deformation significantly increases the tensile strength, however, at the expense of ductility. The strain rate only has a minor influence on the materials tensile behaviour.

  6. Approaches for Tensile Testing of Braided Composites

    NASA Technical Reports Server (NTRS)

    Roberts, Gary D.; Salem, Jonathan A.; Bail, Justin L.; Kohlman, Lee W.; Binienda, Wieslaw K.; Martin, Richard E.

    2011-01-01

    For angleply composites, lamina tension and compression strengths are commonly determined by applying classical lamination theory to test data obtained from testing of angleply composite specimens. For textile composites such as 2D triaxial braids, analysis is more complex and standard test methods do not always yield reliable strength measurements. This paper describes recent research focused on development of more reliable tensile test methods for braided composites and presents preliminary data for various approaches. The materials investigated in this work have 0deg+/-60 2D triaxial braid architecture with nearly equal fiber volume fraction in each of the three fiber directions. Flat composite panels are fabricated by resin transfer molding (RTM) using six layers of the braided preform aligned along the 0deg fiber direction. Various epoxy resins are used as matrix materials. Single layer panels are also fabricated in order to examine local variations in deformation related to the braid architecture. Specimens are cut from these panels in the shape of standard straight-sided coupons, an alternative bowtie geometry, and an alternative notched geometry. Axial tensile properties are measured using specimens loaded along the 0deg fiber direction. Transverse tensile properties are measured using specimens loaded perpendicular to the 0deg fibers. Composite tubes are also fabricated by RTM. These tubes are tested by internal pressurization using a soft rubbery material sealed between the inside diameter of the tube and the load fixtures. The ends of the tube are unconstrained, so the primary load is in the hoop direction. Tubes are fabricated with the 0deg fibers aligned along the tube axis by overbraiding the preform on a mandrel. Since the loading is in the hoop direction, testing of the overbraided tube provides a measure of transverse tensile strength. Previous work has indicated that straight-sided coupons yield a transverse tensile strength that is much lower

  7. Validation and qualification of surface-applied fibre optic strain sensors using application-independent optical techniques

    NASA Astrophysics Data System (ADS)

    Schukar, Vivien G.; Kadoke, Daniel; Kusche, Nadine; Münzenberger, Sven; Gründer, Klaus-Peter; Habel, Wolfgang R.

    2012-08-01

    Surface-applied fibre optic strain sensors were investigated using a unique validation facility equipped with application-independent optical reference systems. First, different adhesives for the sensor's application were analysed regarding their material properties. Measurements resulting from conventional measurement techniques, such as thermo-mechanical analysis and dynamic mechanical analysis, were compared with measurements resulting from digital image correlation, which has the advantage of being a non-contact technique. Second, fibre optic strain sensors were applied to test specimens with the selected adhesives. Their strain-transfer mechanism was analysed in comparison with conventional strain gauges. Relative movements between the applied sensor and the test specimen were visualized easily using optical reference methods, digital image correlation and electronic speckle pattern interferometry. Conventional strain gauges showed limited opportunities for an objective strain-transfer analysis because they are also affected by application conditions.

  8. Tensile properties of amorphous diamond films

    SciTech Connect

    Lavan, D.A.; Hohlfelder, R.J.; Sullivan, J.P.; Friedmann, T.A.; Mitchell, M.A.; Ashby, C.I.

    1999-12-02

    The strength and modulus of amorphous diamond, a new material for surface micromachined MEMS and sensors, was tested in uniaxial tension by pulling laterally with a flat tipped diamond in a nanoindenter. Several sample designs were attempted. Of those, only the single layer specimen with a 1 by 2 {micro}m gage cross section and a fixed end rigidly attached to the substrate was successful. Tensile load was calculated by resolving the measured lateral and normal forces into the applied tensile force and frictional losses. Displacement was corrected for machine compliance using the differential stiffness method. Post-mortem examination of the samples was performed to document the failure mode. The load-displacement data from those samples that failed in the gage section was converted to stress-strain curves using carefully measured gage cross section dimensions. Mean fracture strength was found to be 8.5 {+-} 1.4 GPa and the modulus was 831 {+-} 94 GPa. Tensile results are compared to hardness and modulus measurements made using a nanoindenter.

  9. Experimental validation of applied strain sensors: importance, methods and still unsolved challenges

    NASA Astrophysics Data System (ADS)

    Habel, Wolfgang R.; Schukar, Vivien G.; Mewis, Franziska; Kohlhoff, Harald

    2013-09-01

    Fiber-optic strain sensors are increasingly used in very different technical fields. Sensors are provided with specifications defined by the manufacturer or ascertained by the interested user. If deformation sensors are to be used to evaluate the long-term behavior of safety-relevant structures or to monitor critical structure components, their performance and signal stability must be of high quality to enable reliable data recording. The measurement system must therefore be validated according to established technical rules and standards before its application and after. In some cases, not all details of the complex characteristic and performance of applied fiber-optic sensors are sufficiently understood, or can be validated because of a lack of knowledge and methods to check the sensors' behavior. This contribution focusses therefore on the importance of serious validation in avoiding a decrease or even deterioration of the sensors' function. Methods for validation of applied sensors are discussed and should reveal weaknesses in validation of embedded or integrated fiber-optic deformation and/or strain sensors. An outlook to some research work that has to be carried out to ensure a well-accepted practical use of fiber-optic sensors is given.

  10. Dynamic tensile response of a carbon-fiber-reinforced LCP composite and its temperature sensitivity

    NASA Astrophysics Data System (ADS)

    Shim, Victor P. W.; Yuan, J.; Lim, C. T.

    2001-06-01

    The tensile mechanical behavior of a short carbon fiber filled liquid crystalline polymer (LCP) composite, Vectra A230, was examined under static extension and dynamic loading at three temperatures. Dynamic tension was applied using a pendulum-type tensile spilt Hopkinson bar device. Specimens fabricated according to both the mould flow and transverse directions were tested. The stress-strain curves at various strain rates and temperatures were determined and found to be sensitive to strain rate as well as temperature for both types of specimens. With reference to the properties of pure LCP, mechanical anisotropy and fiber reinforcement effects were characterized and are discussed. Failed specimens were observed suing an optical microscope. Deformation and failure mechanisms in the microstructure of the LCP composite were studied to understand the effects of strain rate and temperature on material strength and failure strain.

  11. Elongation Transducer For Tensile Tests

    NASA Technical Reports Server (NTRS)

    Roberts, Paul W.; Stokes, Thomas R.

    1994-01-01

    Extensometer transducer measures elongation of tensile-test specimen with negligible distortion of test results. Used in stress-versus-strain tests of small specimens of composite materials. Clamping stress distributed more evenly. Specimen clamped gently between jaw and facing surface of housing. Friction force of load points on conical tips onto specimen depends on compression of spring, adjusted by turning cover on housing. Limp, light nylon-insulated electrical leads impose minimal extraneous loads on measuring elements.

  12. Deformation and failure of cartilage in the tensile mode

    PubMed Central

    Sasazaki, Yoshihiro; Shore, Roger; Seedhom, Bahaa B

    2006-01-01

    The aim of this study was to visualize, at the ultrastructural level, the deformation and failure mechanism of cartilage matrix in the tensile mode. Full-thickness dumbbell-shaped specimens were prepared from adult bovines. There were two specimen groups; in the ‘parallel’ group the specimen axis was parallel to the split lines defining the preferential orientation of the collagen in the articular surface, and in the ‘perpendicular’ group the specimen axis was perpendicular to the split lines. Specimens were placed with the articular surface uppermost and subjected to a graded series of strain within individual mini-tension devices, while observed with stereomicroscopy and confocal laser scanning microscopy. Thereafter, the changes in the ultrastructure were observed with both scanning and transmission electron microscopy. The mechanism of cartilage failure in the tensile mode comprised the following stages, whether the strain was applied parallel or perpendicular to the split line. (1) At 0% strain a fibrillar meshwork within the articular surface was predominantly orientated in the direction of the split line. (2) As strain increased, the fibrillar meshwork became more orientated in the parallel group and reorientated in the perpendicular group in the direction of the applied strain. (3) After complete reorientation of the fibrillar meshwork in the direction of the applied strain, the initial sign of failure was rupture of the fibrillar meshwork within the articular surface. (4) Subsequently, the rupture rapidly propagated into the deeper layers. Greater strains were required for fibrillar reorientation and complete rupture in the ‘perpendicular group’ than in the parallel group. PMID:16761971

  13. Effect of High Tensile Strain Rate on the Evolution of Microstructure in Fe-Mn-C-Al Twinning-Induced Plasticity (TWIP) Steel

    NASA Astrophysics Data System (ADS)

    Das, Tuhin; Saha, Rajib; Bera, Supriya; Dahmen, Kirsten; Ghosh, Mainak; Haldar, Arunansu; Bleck, Wolfgang; Chowdhury, Sandip Ghosh

    2015-01-01

    Fe-17.8Mn-0.52C-0.5Al TWIP steel has been investigated under high-strain rate conditions. Twinning along with stacking faults and high dislocation densities in the austenite matrix has been evaluated by X-ray diffraction line profile analysis and transmission electron microscopy. The samples strained at 100 s-1 show a gradient in the evolution of the dislocation density along the gage length except the fracture end where the density shows a decrease. In case of the samples strained at 1 s-1, the evolution of density shows attainment of a near-saturation stage. Electron backscatter diffraction analysis shows that the decrease in the dislocation density as well as near-saturation stage is due to dynamic recovery as well as dynamic recrystallization at region near the fracture end. The dynamically recrystallized grains are related to the deformed matrix through twin relationship.

  14. An improved tensile deformation model for in-situ dendrite/metallic glass matrix composites

    PubMed Central

    Sun, X. H.; Qiao, J. W.; Jiao, Z. M.; Wang, Z. H.; Yang, H. J.; Xu, B. S.

    2015-01-01

    With regard to previous tensile deformation models simulating the tensile behavior of in-situ dendrite-reinforced metallic glass matrix composites (MGMCs) [Qiao et al., Acta Mater. 59 (2011) 4126; Sci. Rep. 3 (2013) 2816], some parameters, such as yielding strength of the dendrites and glass matrix, and the strain-hardening exponent of the dendrites, are estimated based on literatures. Here, Ti48Zr18V12Cu5Be17 MGMCs are investigated in order to improve the tensile deformation model and reveal the tensile deformation mechanisms. The tensile behavior of dendrites is obtained experimentally combining nano-indentation measurements and finite-element-method analysis for the first time, and those of the glass matrix and composites are obtained by tension. Besides, the tensile behavior of the MGMCs is divided into four stages: (1) elastic-elastic, (2) elastic-plastic, (3) plastic-plastic (work-hardening), and (4) plastic-plastic (softening). The respective constitutive relationships at different deformation stages are quantified. The calculated results coincide well with the experimental results. Thus, the improved model can be applied to clarify and predict the tensile behavior of the MGMCs. PMID:26354724

  15. An improved tensile deformation model for in-situ dendrite/metallic glass matrix composites

    NASA Astrophysics Data System (ADS)

    Sun, X. H.; Qiao, J. W.; Jiao, Z. M.; Wang, Z. H.; Yang, H. J.; Xu, B. S.

    2015-09-01

    With regard to previous tensile deformation models simulating the tensile behavior of in-situ dendrite-reinforced metallic glass matrix composites (MGMCs) [Qiao et al., Acta Mater. 59 (2011) 4126; Sci. Rep. 3 (2013) 2816], some parameters, such as yielding strength of the dendrites and glass matrix, and the strain-hardening exponent of the dendrites, are estimated based on literatures. Here, Ti48Zr18V12Cu5Be17 MGMCs are investigated in order to improve the tensile deformation model and reveal the tensile deformation mechanisms. The tensile behavior of dendrites is obtained experimentally combining nano-indentation measurements and finite-element-method analysis for the first time, and those of the glass matrix and composites are obtained by tension. Besides, the tensile behavior of the MGMCs is divided into four stages: (1) elastic-elastic, (2) elastic-plastic, (3) plastic-plastic (work-hardening), and (4) plastic-plastic (softening). The respective constitutive relationships at different deformation stages are quantified. The calculated results coincide well with the experimental results. Thus, the improved model can be applied to clarify and predict the tensile behavior of the MGMCs.

  16. Surfactant effects on soil aggregate tensile strength

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Little is known regarding a soil aggregate's tensile strength response to surfactants that may be applied to alleviate soil water repellency. Two laboratory investigations were performed to determine surfactant effects on the tensile strength of 1) Ap horizons of nine wettable, agricultural soils co...

  17. Electronic and optical properties of silicene under uni-axial and bi-axial mechanical strains: A first principle study

    NASA Astrophysics Data System (ADS)

    Mohan, Brij; Kumar, Ashok; Ahluwalia, P. K.

    2014-07-01

    The uni-axial and bi-axial mechanical strain mediated electronic band structures and dielectric properties of silicene have been investigated. It is found that on applying uni- and bi-axial strains, the band gap opens for smaller strain in silicene. However, on further increase of strain beyond 8% silicene changed into metal. The ultimate tensile strength estimated is 3.4 GPa. Imaginary part of dielectric function shows that the inter-band transitions are red-shifted for uni- and bi-axial tensile strains and are blue shifted for uni- and bi-axial compressive strains. Electron energy loss (EEL) function shows that the π+σ plasmon energies are red-shifted for uni- and bi-axial strains and blue-shifted for compressive strains. The π plasmons disappears for tensile and asymmetric strains. Bi-axial asymmetric strain is found to have no influence on inter-band transitions and π+σ plasmon energies.

  18. High temperature tensile testing of ceramic composites

    NASA Technical Reports Server (NTRS)

    Gyekenyesi, John Z.; Hemann, John H.

    1988-01-01

    The various components of a high temperature tensile testing system are evaluated. The objective is the high temperature tensile testing of SiC fiber reinforced reaction bonded Si3N4 specimens at test temperatures up to 1650 C (3000 F). Testing is to be conducted in inert gases and air. Gripping fixtures, specimen configurations, furnaces, optical strain measuring systems, and temperature measurement techniques are reviewed. Advantages and disadvantages of the various techniques are also noted.

  19. Impact Tensile Testing of Stainless Steels at Various Temperatures

    SciTech Connect

    D. K. Morton

    2008-03-01

    Stainless steels are used for the construction of numerous spent nuclear fuel or radioactive material containers that may be subjected to high strains and moderate strain rates during accidental drop events. Mechanical characteristics of these base materials and their welds under dynamic loads in the strain rate range of concern (1 to 300 per second) are not well documented. However, research is being performed at the Idaho National Laboratory to quantify these characteristics. The work presented herein discusses tensile impact testing of dual-marked 304/304L and 316/316L stainless steel material specimens. Both base material and welded material specimens were tested at -20 oF, room temperature, 300 oF, and 600 oF conditions. Utilizing a drop weight impact test machine and 1/4-inch and 1/2-inch thick dog bone-shaped test specimens, a strain rate range of approximately 4 to 40 per second (depending on initial temperature conditions) was achieved. Factors were determined that reflect the amount of increased strain energy the material can absorb due to strain rate effects. Using the factors, elevated true stress-strain curves for these materials at various strain rates and temperatures were generated. By incorporating the strain rate elevated true stress-strain material curves into an inelastic finite element computer program as the defined material input, significant improvement in the accuracy of the computer analyses was attained. However, additional impact testing is necessary to achieve higher strain rates (up to 300 per second) before complete definition of strain rate effects can be made for accidental drop events and other similar energy-limited impulsive loads. This research approach, using impact testing and a total energy analysis methodology to quantify strain rate effects, can be applied to many other materials used in government and industry.

  20. Image Correlation Applied to Single Crystal Plasticity Experiments and Comparison to Strain Gage Data

    SciTech Connect

    LeBlanc, M M; Florando, J N; Lassila, D H; Schmidt, T; Tyson II, J

    2005-06-29

    Full-field optical techniques are becoming increasingly popular for measuring the deformation of materials, especially in materials that exhibit non-uniform behavior. While there are many full-field techniques available (e.g. moire interferometry, electronic speckle pattern interferometry (ESPI), holography, and image correlation [1]), for our study of the deformation of single crystals, the image correlation technique was chosen for its insensitivity to vibrations and ability to measure large strains. While the theory and development of the algorithms for image correlation have been presented elsewhere [2,3] a comparative study to a conventional strain measurement device, such as a strain gage rosette, is desired to test the robustness and accuracy of the technique. The 6 Degrees of Freedom (6DOF) experiment, which was specifically designed to validate dislocation dynamics (DD) simulations [4], is ideally suited to compare the two methods. This experiment is different from previous experiments on single crystals in that it allows the crystal to deform essentially unconstrained, in both the elastic and plastic regimes, by allowing the bottom of the sample to move as the sample is being compressed. This unconstrained motion prevents the internal crystal planes from rotating during the deformation as typically seen in the pioneering work of Schmid [5] and Taylor [6]. In the early development of the 6DOF apparatus, stacked strain gage rosettes were used to provide the strain data [7]. While very accurate at small strains, strain gages provide an averaged measurement over a small area and cannot be used to measure the inhomogeneous plastic strains that typically occur during the 6DOF experiment. An image correlation technique can measure the full-field in-plane and out-of-plane deformation that occurs in single crystals, and a comparison to the strain gage data at small strains can test the accuracy of the method.

  1. A Shearing-Stretching Device That Can Apply Physiological Fluid Shear Stress and Cyclic Stretch Concurrently to Endothelial Cells.

    PubMed

    Meza, Daphne; Abejar, Louie; Rubenstein, David A; Yin, Wei

    2016-03-01

    Endothelial cell (EC) morphology and functions can be highly impacted by the mechanical stresses that the cells experience in vivo. In most areas in the vasculature, ECs are continuously exposed to unsteady blood flow-induced shear stress and vasodilation-contraction-induced tensile stress/strain simultaneously. Investigations on how ECs respond to combined shear stress and tensile strain will help us to better understand how an altered mechanical environment affects EC mechanotransduction, dysfunction, and associated cardiovascular disease development. In the present study, a programmable shearing and stretching device that can apply dynamic fluid shear stress and cyclic tensile strain simultaneously to cultured ECs was developed. Flow and stress/strain conditions in the device were simulated using a fluid structure interaction (FSI) model. To characterize the performance of this device and the effect of combined shear stress-tensile strain on EC morphology, human coronary artery ECs (HCAECs) were exposed to concurrent shear stress and cyclic tensile strain in the device. Changes in EC morphology were evaluated through cell elongation, cell alignment, and cell junctional actin accumulation. Results obtained from the numerical simulation indicated that in the "in-plane" area of the device, both fluid shear stress and biaxial tensile strain were uniform. Results obtained from the in vitro experiments demonstrated that shear stress, alone or combined with cyclic tensile strain, induced significant cell elongation. While biaxial tensile strain alone did not induce any appreciable change in EC elongation. Fluid shear stress and cyclic tensile strain had different effects on EC actin filament alignment and accumulation. By combining various fluid shear stress and cyclic tensile strain conditions, this device can provide a physiologically relevant mechanical environment to study EC responses to physiological and pathological mechanical stimulation. PMID:26810848

  2. Lifetime and failure strain prediction for material subjected to non-stationary tensile loading conditions: applications to Zircaloy - 4. [Monkman-Grant relationship

    SciTech Connect

    Bocek, M.

    1982-01-01

    The life fraction rule (LFR) is used to calculate the lifetime of materials subjected to stress and temperature ramp loading. The solutions for the individual nonstationary temperature and stress loading conditions can be applied to predict also the lifetime of structures loaded by superimposed ramps solely on the basis of normal 'iso'-stress rupture data. The concept is applied to tensional stress and temperature cycling as well. As compared with the peculiarities of the problem, the agreement between experiments and calculations is encouraging. 16 refs.

  3. Micro-/nanosized cantilever beams and mass sensors under applied axial tensile/compressive force vibrating in vacuum and viscous fluid

    NASA Astrophysics Data System (ADS)

    Stachiv, Ivo; Fang, Te-Hua; Chen, Tao-Hsing

    2015-11-01

    Vibrating micro-/nanosized cantilever beams under an applied axial force are the key components of various devices used in nanotechnology. In this study, we perform a complete theoretical investigation of the cantilever beams under an arbitrary value of the axial force vibrating in a specific environment such as vacuum, air or viscous fluid. Based on the results easy accessible expressions enabling one the fast and highly accurate estimations of changes in the Q-factor and resonant frequencies of beam oscillating in viscous fluid caused by the applied axial force are derived and analyzed. It has been also shown that for beam-to-string and string vibrational regimes the mode shape starts to significantly deviate from the one known for a beam without axial force. Moreover, a linear dependency of the vibrational amplitude in resonance on the dimensionless tension parameter has been found. We revealed that only a large axial force, i.e. the string vibrational regime, significantly improves the Q-factor of beams submerged in fluid, while an increase of the axial force in beam and beam-to-string transition regimes has a negligibly small impact on the Q-factor enhancement. Experiments carried out on the carbon nanotubes and nanowires are in a good agreement with present theoretical predictions.

  4. Micro-/nanosized cantilever beams and mass sensors under applied axial tensile/compressive force vibrating in vacuum and viscous fluid

    SciTech Connect

    Stachiv, Ivo; Fang, Te-Hua; Chen, Tao-Hsing

    2015-11-15

    Vibrating micro-/nanosized cantilever beams under an applied axial force are the key components of various devices used in nanotechnology. In this study, we perform a complete theoretical investigation of the cantilever beams under an arbitrary value of the axial force vibrating in a specific environment such as vacuum, air or viscous fluid. Based on the results easy accessible expressions enabling one the fast and highly accurate estimations of changes in the Q-factor and resonant frequencies of beam oscillating in viscous fluid caused by the applied axial force are derived and analyzed. It has been also shown that for beam-to-string and string vibrational regimes the mode shape starts to significantly deviate from the one known for a beam without axial force. Moreover, a linear dependency of the vibrational amplitude in resonance on the dimensionless tension parameter has been found. We revealed that only a large axial force, i.e. the string vibrational regime, significantly improves the Q-factor of beams submerged in fluid, while an increase of the axial force in beam and beam-to-string transition regimes has a negligibly small impact on the Q-factor enhancement. Experiments carried out on the carbon nanotubes and nanowires are in a good agreement with present theoretical predictions.

  5. Simultaneous 2D Strain Sensing Using Polymer Planar Bragg Gratings

    PubMed Central

    Rosenberger, Manuel; Eisenbeil, Waltraud; Schmauss, Bernhard; Hellmann, Ralf

    2015-01-01

    We demonstrate the application of polymer planar Bragg gratings for multi-axial strain sensing and particularly highlight simultaneous 2D strain measurement. A polymer planar Bragg grating (PPBG) fabricated with a single writing step in bulk polymethylmethacrylate is used for measuring both tensile and compressive strain at various angles. It is shown that the sensitivity of the PPBG strongly depends on the angle between the optical waveguide into which the grating is inscribed and the direction along which the mechanical load is applied. Additionally, a 2D PPBG fabricated by writing two Bragg gratings angularly displaced from each other into a single polymer platelet is bonded to a stainless steel plate. The two reflected wavelengths exhibit different sensitivities while tested toward tensile and compressive strain. These characteristics make 2D PPBG suitable for measuring multi-axial tensile and compressive strain. PMID:25686313

  6. Simultaneous 2D strain sensing using polymer planar Bragg gratings.

    PubMed

    Rosenberger, Manuel; Eisenbeil, Waltraud; Schmauss, Bernhard; Hellmann, Ralf

    2015-01-01

    We demonstrate the application of polymer planar Bragg gratings for multi-axial strain sensing and particularly highlight simultaneous 2D strain measurement. A polymer planar Bragg grating (PPBG) fabricated with a single writing step in bulk polymethylmethacrylate is used for measuring both tensile and compressive strain at various angles. It is shown that the sensitivity of the PPBG strongly depends on the angle between the optical waveguide into which the grating is inscribed and the direction along which the mechanical load is applied. Additionally, a 2D PPBG fabricated by writing two Bragg gratings angularly displaced from each other into a single polymer platelet is bonded to a stainless steel plate. The two reflected wavelengths exhibit different sensitivities while tested toward tensile and compressive strain. These characteristics make 2D PPBG suitable for measuring multi-axial tensile and compressive strain. PMID:25686313

  7. Characterization and modeling of tensile behavior of ceramic woven fabric composites

    NASA Technical Reports Server (NTRS)

    Kuo, Wen-Shyong; Chen, Wennei Y.; Parvizi-Majidi, Azar; Chou, Tsu-Wei

    1991-01-01

    This paper examines the tensile behavior of SiC/SiC fabric composites. In the characterization effort, the stress-strain relation and damage evolution are studied with a series of loading and unloading tensile test experiments. The stress-strain relation is linear in response to the initial loading and becomes nonlinear when loading exceeds the proportional limit. Transverse cracking has been observed to be a dominant damage mode governing the nonlinear deformation. The damage is initiated at the inter-tow pores where fiber yarns cross over each other. In the modeling work, the analysis is based upon a fiber bundle model, in which fiber undulation in the warp and fill directions and gaps among fiber yarns have been taken into account. Two limiting cases of fabric stacking arrangements are studied. Closed form solutions are obtained for the composite stiffness and Poisson's ratio. Transverse cracking in the composite is discussed by applying a constant failure strain criterion.

  8. Identification of a keratinase-producing bacterial strain and enzymatic study for its improvement on shrink resistance and tensile strength of wool- and polyester-blended fabric.

    PubMed

    Cai, Shao-Bo; Huang, Zheng-Hua; Zhang, Xing-Qun; Cao, Zhang-Jun; Zhou, Mei-Hua; Hong, Feng

    2011-01-01

    A wool-degrading bacterium was isolated from decomposition wool fabrics in China. The strain, named 3096-4, showed excellent capability of removing cuticle layer of wool fibers, as demonstrated by removing cuticle layer completely within 48 h. According to the phenotypic characteristics and 16S rRNA profile, the isolate was classified as Pseudomonas. Bacteria growth and keratinase activity of the isolate were determined during cultivation on raw wool at different temperatures, initial pH, and rotation speed using orthogonal matrix method. Maximum growth and keratinase activity of the bacterium were observed under the condition including 30 °C, initial pH 7.6, and rotational speeds 160 rpm. The keratinase-containing crude enzyme prepared from 3096-4 was evaluated in the treatment of wool fabrics. The optimal condition of our enzymatic improvement of shrink resistance was the combination of 30 °C, initial pH 7.6, and rotation speeds 160 rpm. After the optimized treatment, the wool fabrics felting shrink was 4.1% at 6 h, and textile strength was not lost. PMID:20607444

  9. Comparative Study of Various E. coli Strains for Biohydrogen Production Applying Response Surface Methodology

    PubMed Central

    Bakonyi, Péter; Nemestóthy, Nándor; Bélafi-Bakó, Katalin

    2012-01-01

    The proper strategy to establish efficient hydrogen-producing biosystems is the biochemical, physiological characterization of hydrogen-producing microbes followed by metabolic engineering in order to give extraordinary properties to the strains and, finally, bioprocess optimization to realize enhanced hydrogen fermentation capability. In present paper, it was aimed to show the utility both of strain engineering and process optimization through a comparative study of wild-type and genetically modified E. coli strains, where the effect of two major operational factors (substrate concentration and pH) on bioH2 production was investigated by experimental design and response surface methodology (RSM) was used to determine the suitable conditions in order to obtain maximum yields. The results revealed that by employing the genetically engineered E. coli (DJT 135) strain under optimized conditions (pH: 6.5; Formate conc.: 1.25 g/L), 0.63 mol H2/mol formate could be attained, which was 1.5 times higher compared to the wild-type E. coli (XL1-BLUE) that produced 0.42 mol H2/mol formate (pH: 6.4; Formate conc.: 1.3 g/L). PMID:22666156

  10. Voltage generation from individual BaTiO(3) nanowires under periodic tensile mechanical load.

    PubMed

    Wang, Zhaoyu; Hu, Jie; Suryavanshi, Abhijit P; Yum, Kyungsuk; Yu, Min-Feng

    2007-10-01

    Direct tensile mechanical loading of an individual single-crystal BaTiO(3) nanowire was realized to reveal the direct piezoelectric effect in the nanowire. Periodic voltage generation from the nanowire was produced by a periodically varying tensile mechanical strain applied with a precision mechanical testing stage. The measured voltage generation from the nanowire was found to be directly proportional to the applied strain rate and was successfully modeled through the consideration of an equivalent circuit for a piezoelectric nanowire under low-frequency operation. The study, besides demonstrating a controlled experimental method for the study of direct piezoelectric effect in nanostructures, implies also the use of such perovskite piezoelectric nanowires for efficient energy-harvesting applications. PMID:17894515

  11. In situ tensile and creep testing of lithiated silicon nanowires

    SciTech Connect

    Boles, Steven T.; Kraft, Oliver; Thompson, Carl V.; Mönig, Reiner

    2013-12-23

    We present experimental results for uniaxial tensile and creep testing of fully lithiated silicon nanowires. A reduction in the elastic modulus is observed when silicon nanowires are alloyed with lithium and plastic deformation becomes possible when the wires are saturated with lithium. Creep testing was performed at fixed force levels above and below the tensile strength of the material. A linear dependence of the strain-rate on the applied stress was evident below the yield stress of the alloy, indicating viscous deformation behavior. The observed inverse exponential relationship between wire radius and strain rate below the yield stress indicates that material transport was controlled by diffusion. At stress levels approaching the yield strength of fully lithiated silicon, power-law creep appears to govern the strain-rate dependence on stress. These results have direct implications on the cycling conditions, rate-capabilities, and charge capacity of silicon and should prove useful for the design and construction of future silicon-based electrodes.

  12. Effects on diversity of soil fungal community and fate of an artificially applied Beauveria bassiana strain assessed through 454 pyrosequencing.

    PubMed

    Hirsch, Jacqueline; Galidevara, Sandhya; Strohmeier, Stephan; Devi, K Uma; Reineke, Annette

    2013-10-01

    The entomopathogenic fungus Beauveria bassiana is widely used as a biological control agent (BCA) for insect pest control, with fungal propagules being either incorporated into the potting media or soil or sprayed directly onto the foliage or soil. To gain a better understanding of entomopathogenic fungal ecology when applied as a BCA to the soil environment, a case study using tag-encoded 454 pyrosequencing of fungal ITS sequences was performed to assess the fate and potential effect of an artificially applied B. bassiana strain on the diversity of soil fungal communities in an agricultural field in India. Results show that the overall fungal diversity was not influenced by application of B. bassiana during the 7 weeks of investigation. Strain-specific microsatellite markers indicated both an establishment of the applied B. bassiana strain in the treated plot and its spread to the neighboring nontreated control plot. These results might be important for proper risk assessment of entomopathogenic fungi-based BCAs. PMID:23736813

  13. Tuning the Schottky contacts in the phosphorene and graphene heterostructure by applying strain.

    PubMed

    Liu, Biao; Wu, Li-Juan; Zhao, Yu-Qing; Wang, Lin-Zhi; Caii, Meng-Qiu

    2016-07-20

    The structures and electronic properties of the phosphorene and graphene heterostructure are investigated by density functional calculations using the hybrid Heyd-Scuseria-Ernzerhof (HSE) functional. The results show that the intrinsic properties of phosphorene and graphene are preserved due to the weak van der Waals contact. But the electronic properties of the Schottky contacts in the phosphorene and graphene heterostructure can be tuned from p-type to n-type by the in-plane compressive strains from -2% to -4%. After analyzing the total band structure and density of states of P atom orbitals, we find that the Schottky barrier height (SBH) is determined by the P-pz orbitals. What is more, the variation of the work function of the phosphorene monolayer and the graphene electrode and the Fermi level shift are the nature of the transition of Schottky barrier from n-type Schottky contact to p-type Schottky contact in the phosphorene and graphene heterostructure under different in-plane strains. We speculate that these are general results of tuning of the electronic properties of the Schottky contacts in the phosphorene and graphene heterostructure by controlling the in-plane compressive strains to obtain a promising method to design and fabricate a phosphorene-graphene based field effect transistor. PMID:27398801

  14. Impacts of additive uniaxial strain on hole mobility in bulk Si and strained-Si p-MOSFETs

    NASA Astrophysics Data System (ADS)

    Shuo, Zhao; Lei, Guo; Jing, Wang; Jun, Xu; Zhihong, Liu

    2009-10-01

    Hole mobility changes under uniaxial and combinational stress in different directions are characterized and analyzed by applying additive mechanical uniaxial stress to bulk Si and SiGe-virtual-substrate-induced strained-Si (s-Si) p-MOSFETs (metal-oxide-semiconductor field-effect transistors) along (110) and (100) channel directions. In bulk Si, a mobility enhancement peak is found under uniaxial compressive strain in the low vertical field. The combination of (100) direction uniaxial tensile strain and substrate-induced biaxial tensile strain provides a higher mobility relative to the (110) direction, opposite to the situation in bulk Si. But the combinational strain experiences a gain loss at high field, which means that uniaxial compressive strain may still be a better choice. The mobility enhancement of SiGe-induced strained p-MOSFETs along the (110) direction under additive uniaxial tension is explained by the competition between biaxial and shear stress.

  15. Effect of the strain-induced melt activation (SIMA) process on the tensile properties of a new developed super high strength aluminum alloy modified by Al-5Ti-1B grain refiner

    SciTech Connect

    Haghparast, Amin; Nourimotlagh, Masoud; Alipour, Mohammad

    2012-09-15

    In this study, the effect of Al-5Ti-1B grain refiners and modified strain-induced melt activation process on an Al-Zn-Mg-Cu alloy was studied. The optimum level of Ti was found to be 0.1 wt.%. The specimens subjected to deformation ratio of 40% (at 300 Degree-Sign C) and various heat treatment times (10-40 min) and temperature (550-600 Degree-Sign C) regimes were characterized in this study. Reheating condition to obtain a fine globular microstructure was optimized. Microstructural examinations were conducted by optical and scanning electron microscopy coupled with an energy dispersive spectrometry. The optimum temperature and time in strain-induced melt activation process are 575 Degree-Sign C and 20 min, respectively. T6 heat treatment including quenching to room temperature and aging at 120 Degree-Sign C for 24 h was employed to reach to the maximum strength. Significant improvements in mechanical properties were obtained with the addition of grain refiner combined with T6 heat treatment. After the T6 heat treatment, the average tensile strength increased from 283 MPa to 587 and 332 MPa to 617 for samples refined with 2 wt.% Al-5Ti-1B before and after strain-induced melt activation process and extrusion process, respectively. Ultimate strength of Ti-refined specimens without SIMA process has a lower value than globular microstructure specimens after SIMA and extrusion process. - Highlights: Black-Right-Pointing-Pointer The effect of Al-5Ti-1B on the aluminum alloy produced by SIMA process was studied. Black-Right-Pointing-Pointer Al-5Ti-1B is an effective in reducing the grain and reagent fine microstructure. Black-Right-Pointing-Pointer Reheating condition to obtain a fine globular microstructure was optimized. Black-Right-Pointing-Pointer The optimum temperature and time in SIMA process are 575 Degree-Sign C and 20 min respectively. Black-Right-Pointing-Pointer UTS of globular structure specimens have a more value than Ti-refined specimens.

  16. Band gap engineering in polymers through chemical doping and applied mechanical strain

    NASA Astrophysics Data System (ADS)

    Lanzillo, Nicholas A.; Breneman, Curt M.

    2016-08-01

    We report simulations based on density functional theory and many-body perturbation theory exploring the band gaps of common crystalline polymers including polyethylene, polypropylene and polystyrene. Our reported band gaps of 8.6 eV for single-chain polyethylene and 9.1 eV for bulk crystalline polyethylene are in excellent agreement with experiment. The effects of chemical doping along the polymer backbone and side-groups are explored, and the use mechanical strain as a means to modify the band gaps of these polymers over a range of several eV while leaving the dielectric constant unchanged is discussed. This work highlights some of the opportunities available to engineer the electronic properties of polymers with wide-reaching implications for polymeric dielectric materials used for capacitive energy storage.

  17. Band gap engineering in polymers through chemical doping and applied mechanical strain.

    PubMed

    Lanzillo, Nicholas A; Breneman, Curt M

    2016-08-17

    We report simulations based on density functional theory and many-body perturbation theory exploring the band gaps of common crystalline polymers including polyethylene, polypropylene and polystyrene. Our reported band gaps of 8.6 eV for single-chain polyethylene and 9.1 eV for bulk crystalline polyethylene are in excellent agreement with experiment. The effects of chemical doping along the polymer backbone and side-groups are explored, and the use mechanical strain as a means to modify the band gaps of these polymers over a range of several eV while leaving the dielectric constant unchanged is discussed. This work highlights some of the opportunities available to engineer the electronic properties of polymers with wide-reaching implications for polymeric dielectric materials used for capacitive energy storage. PMID:27324304

  18. Range-resolved signal processing for fibre segment interferometry applied to dynamic long-gauge length strain sensing

    NASA Astrophysics Data System (ADS)

    Kissinger, Thomas; Correia, Ricardo; Charrett, Thomas O. H.; James, Stephen W.; Tatam, Ralph P.

    2015-09-01

    A range-resolved interferometric signal processing technique using sinusoidal optical frequency modulation is applied to fibre segment interferometry. Here, six optical fibre segments of gauge length 12.5 cm are used as interferometric strain sensors and are formed between seven weak, broadband fibre Bragg gratings, acting as in-fibre partial reflectors. In a very simple and cost-effective optical setup using injection current modulation of a laser diode source, interferometric measurement of acoustic wave propagation in a metal rod is used to demonstrate the capabilities of the technique.

  19. Tensile Deformation of Polyethylenes: Crystallinity Effects

    NASA Astrophysics Data System (ADS)

    Crist, Buckley; Metaxas, Costas

    2004-03-01

    The crystalline fraction of polyethylene can be reduced by increasing the cooling rate, the molecular weight or the fraction of comonomer. All three methods have been used in this study of tensile deformation which shows that true stress - true strain behavior depends systematically on morphology. The dependence of uniaxial yield stress on crystal thickness is well understood in terms of dislocation nucleation. Post yield flow is dominated by the strain hardening rate that is larger in polyethylenes of lower crystallinity. Noncrystalline polymer evidently reduces the plastic compliance while providing for elastic (reversible) strains. These observations are examined in terms of old and new theories for deformation of semicrystalline polymers.

  20. Incipient and Progressive Damage in Polyethylene Under Extreme Tensile Conditions

    SciTech Connect

    Furmanski, Jevan; Brown, Eric; Trujillo, Carl P.; Martinez, Daniel Tito; Gray, George T. III

    2012-06-07

    The Dynamic-Tensile-Extrusion (Dyn-Ten-Ext) test was developed at LANL by Gray and coworkers to probe the tensile response of materials at large strains (>1) and high strain-rates (>1000/s) by firing projectiles through a conical die at 300-700 m/s. This technique has recently been applied to various polymers, such as the fluoropolymers PTFE (Teflon) and the chemically similar PCTFE, which respectively exhibited catastrophic fragmentation and distributed dynamic necking. This work details investigations of the Dyn-Ten-Ext response of high density polyethylene, both to failure and sub-critical conditions. At large extrusion ratios ({approx}7.4) and high velocities, such as those previously employed, HDPE catastrophically fragmented in a craze-like manner in the extruded jet. At more modest extrusion ratios and high velocities the specimen extruded a stable jet that ruptured cleanly, and at lower velocities was recovered intact after sustaining substantial internal damage. Thermomechanical finite element simulations showed that the damage corresponded to a locus of shear stress in the presence of hydrostatic tension. X-ray computed tomography corroborated the prediction of a shear damage mechanism by finding the region of partially damaged material to consist of macroscopic shear-mode cracks nearly aligned with the extrusion axis, originating from the location of damage inception.

  1. Tensile-property characterization of thermally aged cast stainless steels.

    SciTech Connect

    Michaud, W. F.; Toben, P. T.; Soppet, W. K.; Chopra, O. K.; Energy Technology

    1994-03-03

    The effect of thermal aging on tensile properties of cast stainless steels during service in light water reactors has been evaluated. Tensile data for several experimental and commercial heats of cast stainless steels are presented. Thermal aging increases the tensile strength of these steels. The high-C Mo-bearing CF-8M steels are more susceptible to thermal aging than the Mo-free CF-3 or CF-8 steels. A procedure and correlations are presented for predicting the change in tensile flow and yield stresses and engineering stress-vs.-strain curve of cast stainless steel as a function of time and temperature of service. The tensile properties of aged cast stainless steel are estimated from known material information, i.e., chemical composition and the initial tensile strength of the steel. The correlations described in this report may be used for assessing thermal embrittlement of cast stainless steel components.

  2. Tensile-property characterization of thermally aged cast stainless steels

    SciTech Connect

    Michaud, W.F.; Toben, P.T.; Soppet, W.K.; Chopra, O.K.

    1994-02-01

    The effect of thermal aging on tensile properties of cast stainless steels during service in light water reactors has been evaluated. Tensile data for several experimental and commercial heats of cast stainless steels are presented. Thermal aging increases the tensile strength of these steels. The high-C Mo-bearing CF-8M steels are more susceptible to thermal aging than the Mo-free CF-3 or CF-8 steels. A procedure and correlations are presented for predicting the change in tensile flow and yield stresses and engineering stress-vs.-strain curve of cast stainless steel as a function of time and temperature of service. The tensile properties of aged cast stainless steel are estimated from known material information, i.e., chemical composition and the initial tensile strength of the steel. The correlations described in this report may be used for assessing thermal embrittlement of cast stainless steel components.

  3. In Situ Radiography During Tensile Tests

    NASA Technical Reports Server (NTRS)

    Baaklini, George Y.; Bhatt, Ramakrishna T.

    1994-01-01

    Laboratory system for testing specimens of metal-, ceramic-, and intermetallic-matrix composite materials incorporates both electromechanical tensile-testing subsystem and either of two imaging subsystems that take x-ray photographs of specimens before, during, and after tensile tests. Used to test specimens of reaction-bonded silicon nitride reinforced with silicon carbide fibers (SiC/RBSN) considered for high-temperature service in advanced aircraft turbine engines. Provides data on effects of preexisting flaws (e.g., high-density impurities and local variations of density) on fracture behavior. Accumulated internal damage monitored during loading. X-ray source illuminates specimen in load frame while specimen is pulled. X-ray images on film correlated with stress-vs.-strain data from tensile test.

  4. Pressure reversal study through tensile tests

    SciTech Connect

    Swinson, W.F.; Battiste, R.L.; Wright, A.L.; Yahr, G.T.; Robertson, J.P.

    1997-12-31

    This paper is a summary of the results from a study of the variables related to pressure reversal and was sponsored by the US Department of Transportation, Office of Pipeline Safety. The circumferential pipe stress, which is the most significant variable in pressure reversal, was examined by using tensile specimens and then relating the results to pressurized pipe. A model is proposed that gives some insight into how pressure reversal can be minimized when a section of pipe is being hydrotested. Twenty tensile specimens from X-42 electric resistance welded (ERW) pipe and twenty specimens from X-52 ERW pipe were tested. Each specimen had a machined flaw. The flaw regions were monitored using strain gages and photoelasticity. These tensile tests represent the first phase of a research effort to examine and understand the variables related to pressure reversal. The second phase of this effort will be with pipe specimens and presently is in progress.

  5. Dynamic tensile characterization of pig skin

    NASA Astrophysics Data System (ADS)

    Khatam, H.; Liu, Q.; Ravi-Chandar, K.

    2014-04-01

    The strain-rate dependent response of porcine skin oriented in the fiber direction is explored under tensile loading. Quasi-static response was obtained at strain rates in the range of 10-3 s-1 to 25 s-1. Characterization of the response at even greater strain rates is accomplished by measuring the spatio-temporal evolution of the particle velocity and strain in a thin strip subjected to high speed impact loading that generates uniaxial stress conditions. These experiments indicate the formation of shock waves; the shock Hugoniot that relates particle velocity to the shock velocity and the dynamic stress to dynamic strain is obtained directly through experimental measurements, without any assumptions regarding the constitutive properties of the material. [Figure not available: see fulltext.

  6. Influence of strain on water adsorption and dissociation on rutile TiO2(110) surface.

    PubMed

    Yang, Long; Shu, Da-Jun; Li, Shao-Chun; Wang, Mu

    2016-06-01

    The influence of externally applied strain on water adsorption and dissociation on a defect-free rutile TiO2(110) surface is studied by using first-principles calculations. We found that while compressive strain makes water adsorption and dissociation less favorable, tensile strain increases the energy gain of water adsorption, and decreases the energy cost of water dissociation. Specifically, dissociative water becomes more stable than molecular water when an 8% tensile in-plane strain is applied. Moreover, the dissociation barrier decreases with increasing strain more rapidly for more isolated water. The rate of decrease of this barrier for nearly isolated water is 0.017 eV per 1% biaxial strain. This demonstrates that applying strain is a possible way to engineer the surface adsorption and dissociation of water on a TiO2(110) surface, and therefore engineer the relevant surface reactivity. PMID:27138099

  7. Dynamic behavior of nano-voids in magnesium under hydrostatic tensile stress

    NASA Astrophysics Data System (ADS)

    Ponga, Mauricio; Ramabathiran, Amuthan A.; Bhattacharya, Kaushik; Ortiz, Michael

    2016-08-01

    We investigate the mechanisms responsible for nano-void growth in single crystal magnesium under dynamic hydrostatic tensile stress. A key conclusion derived from our study is that there is no secondary strain hardening near the nano-void. This behavior, which is in remarkable contrast to face-centered cubic and body-centered cubic materials, greatly limits the peak stress and explains the relatively lower spall strength of magnesium. The lack of secondary strain hardening is due to the fact that pyramidal dislocations do not interact with basal or prismatic dislocations. Our analysis also shows that for loads applied at moderate strain rates (\\overset{\\centerdot}{ε} ≤slant {{10}6} s‑1) the peak stress, dislocation velocity and temperature distribution converge asymptotically. However at very high strain rates (\\overset{\\centerdot}{ε} ≥slant {{10}8} s‑1), there is a sharp transition in these quantities.

  8. Role of mechanical loads in inducing in-cycle tensile stress in thermally grown oxide

    SciTech Connect

    Diaz, R.; Jansz, M.; Mossaddad, M.; Raghavan, S.; Okasinski, J.S.; Almer, J.D.; Perez, H.P.; Imbrie, P.

    2012-01-01

    Experimental in situ synchrotron x-ray diffraction results tracking the strain behavior of the various layers during a cycle, under thermo-mechanical conditions are presented in this work. The quantitative strain measurements here show that the thermally grown oxide briefly experiences in-plane tensile stress ({sigma}{sub 22} = +36.4 MPa) with increased mechanical loading during ramp-up in the thermal cycle. These findings are the first in situ experimental observations of these strains under thermo-mechanical conditions, envisaged to serve as a catalyst for crack initiation. The depth resolved measurements of strain taken during applied thermal and mechanical load in this work are a significant step towards achieving realistic testing conditions.

  9. Numerical Simulation of Damage using an Elastic-Viscoplastic Model with Directional Tensile Failure

    SciTech Connect

    Lomov, I

    2003-03-17

    A new continuum model for directional tensile failure has been developed that can simulate weakening and void formation due to directional tensile failure. The model is developed within the context of a properly invariant nonlinear thermomechanical theory. A second order damage tensor is introduced which allows simulation of weakening to tension applied in one direction, without weakening to subsequent tension applied in perpendicular directions. This damage tensor can be advected using standard methods in computer codes. Porosity is used as an isotropic measure of volumetric void strain and its evolution is influenced by tensile failure. The rate of dissipation due to directional tensile failure takes a particularly simple form, which can be analyzed easily. Specifically, the model can be combined with general constitutive equations for porous compaction and dilation, as well as viscoplasticity. A robust non-iterative numerical scheme for integrating these evolution equations is proposed. This constitutive model has been implemented into an Eulerian shock wave code with adaptive mesh refinement. A number of simulations of complicated shock loading of different materials have been performed including problems of fracture of rock. These simulations show that directionality of damage can play a significant role in material failure.

  10. In-situ lattice-strain analysis of a ferroelectric thin film under an applied pulse electric field

    SciTech Connect

    Sakata, O.; Yasui, S.; Yamada, T.; Funakubo, H.; Yabashi, M.

    2010-06-23

    We developed an in-situ measurement system for characterizing the relationship between ferroelectricity and lattice distortion of a ferroelectric thin film at BL13XU, SPring-8. The dielectric polarization obtained and the lattice strain evaluated provide us with the electrostrictive coefficient of the film. The system for the method consists of a refractive lens for two dimensional micron focusing, ferroelectric characterization system, high-precision four-circle diffractometer, and time-resolved photon counting system. It enables in-situ measurements of the electric polarization of the film and an electric-field-induced strain using nano-second order time-resolved synchrotron diffraction. We applied the method to determining the lattice constant distorted by the electric field and the polarization value of a 410 nm-thick BiFeO{sub 3} thin film. The piezoelectric constant d{sub 33} evaluated was about 28 pm/V. The polarization observed allowed us to evaluate an electrostrictive coefficient Q of 1{center_dot}4x10{sup -2} m{sup 4}/C{sup 2}.