共查询到20条相似文献,搜索用时 859 毫秒
1.
Dongya Wei Changming Mao Shuai Li Zhaobo Wang 《Journal of Macromolecular Science: Physics》2014,53(4):601-614
Thermoplastic vulcanizates (TPVs) based on nitrile butadiene rubber (NBR)/ acrylonitrile-butadiene-styrene (ABS) blends were prepared by dynamic vulcanization, and then compatibilized by styrene-butadiene-styrene block copolymer (SBS). The effects of SBS compatibilizer on mechanical properties, Mullins effect, and morphological properties of the TPVs were investigated systematically. Experimental results indicated that SBS had an excellent compatibilization effect on the dynamically vulcanized NBR/ABS TPVs. The tensile strength increased from 9.4 to 15.8 MPa and the elongation at break went through a maximum value when the dosage of SBS was only 1 phr. Mullins effect results showed that the compatibilized NBR/ABS TPV had relatively lower residual deformation and internal friction loss than the NBR/ABS TPV, indicating the improvement of elasticity. Morphology studies showed that the vulcanized NBR particles were dispersed evenly in the TPVs and the dimensions of NBR particles were decreased remarkably with the incorporation of SBS compatibilizer. 相似文献
2.
3.
We report on the morphological evolutions of iron films sputtering deposited on elastic polydimethylsiloxane (PDMS) substrates under uniaxial compression/tension. The experiment shows that the as-prepared film (no external strain) spontaneously forms cracks and wrinkles due to the residual thermal stresses stored up during/after the film deposition. The external uniaxial compression can generate delaminated buckles perpendicular to the loading direction (transverse direction) and new cracks in the loading direction (longitudinal direction). Subsequent reloading and further straining result in the formation of transverse cracks and longitudinal buckles. It is found that there exists a significant coupling effect between the cracking and buckling patterns during the compression/tension process. The morphological evolution behaviours and underlying physical mechanisms are discussed and analysed in depth in this paper. 相似文献
4.
Thermoplastic elastomers (TPEs) based on high-impact polystyrene (HIPS)/waste styrene–butadiene rubber powder (WSBRP) blends were prepared by melt-compounding; they were enhanced by incorporation of styrene–butadiene–styrene block copolymer (SBS) and aromatic oil (AO). The effects of SBS and AO dosage on the mechanical properties, Mullins effect and morphological properties of the blends were investigated. Experimental results showed that the incorporation of SBS and AO in the HIPS/WSBRP blends could improve the mechanical properties significantly. Compared with that of HIPS/WSBRP blends, the elongation at break had a maximum value with 9 phr SBS and 15 phr AO loading, being improved by about 220%. The Mullins effect results showed that a softening effect appeared obviously after the first loading–unloading cycle, while the residual deformation and internal friction loss of the HIPS/SBS/AO/WSBRP TPEs were much lower than those of the HIPS/WSBRP blends, indicating the improvement of elasticity. 相似文献
5.
The application of ultrasonics in metal forming applications has been shown to reduce the forming load significantly in many research studies. The load reduction has been related to the stress superposition effect, rise in temperature and change in the friction condition between the specimen and die interfaces. This paper reports an investigation into the effects of superimposed ultrasonic oscillation of the die in compression tests on aluminium specimens. In particular, a finite element model is developed to simulate uniaxial compression and to model the effects of a change in the friction boundary condition when ultrasonic excitation is applied to the lower platen. The model predictions of the stress-strain relationship can be compared with test data to provide some insights into the effects of the interfacial condition. The paper shows how the analysis of the test data, combined with finite element models of ultrasonic compression test simulations, allows some initial conclusions to be drawn regarding the influence of the interfacial friction during ultrasonic compression. 相似文献
6.
T.J. Holmquist J. Bradley A. Dwivedi D. Casem 《The European physical journal. Special topics》2016,225(2):343-354
This article presents the response of polymethyl methacrylate (PMMA) subjected to large strains, high strain rates, high pressures, a range in temperatures, and variations in the intermediate principal stress. Laboratory data from the literature, and new test data provided here, are used in the evaluation. The new data include uniaxial stress compression tests (at various strain rates and temperatures) and uniaxial stress tension tests (at low strain rates and ambient temperatures). The compression tests include experiments at ?ε= 13,000 s?1, significantly extending the range of known strain rate data. The observed behavior of PMMA includes the following: it is brittle in compression at high rates, and brittle in tension at all rates; strength is dependent on the pressure, strain, strain rate, temperature, and the intermediate principal stress; the shear modulus increases as the pressure increases; and it is highly compressible. Also presented are novel, high velocity impact tests (using high-speed imaging) that provide insight into the initiation and evolution of damage. Lastly, computational constitutive models for pressure, strength, and failure are presented that provide responses that are in good agreement with the laboratory data. The models are used to compute several ballistic impact events for which experimental data are available. 相似文献
7.
FAN ZhenJun ZHENG ZhiYuan & JIAO ZengBao School of Materials Sciences Technology China University of Geosciences Beijing China 《中国科学:物理学 力学 天文学(英文版)》2010,(5)
The compressive fracture characteristics of Zr-based bulk metallic glass under uniaxial compression tests are studied.The zigzag rheological behavior is observed in the compression stress-strain curves of amorphous alloys.At room temperature the uniaxial compression fracture takes place along the plane which is at a 45-degree angle to the direction of the compressive stress.The microstructure of a typical fracture pattern is the vein network.A unique,finger-like vein pattern is found to exist at the fractur... 相似文献
8.
V. N. Kravchenko N. YA. Minina A. M. Savin I. V. Berman O. P. Hansen C. B. Sorensen 《高压研究》2013,33(2):305-308
Anisotropy of the piezoresistance relaxations has been observed in p -(0 0 1)GaAs/Al 0.5 Ga 0.5 As heterostructures. The character of relaxation process depends on the direction of the applied uniaxial compression: after loading along [1 m 1 0] direction the specimen resistance relaxes down to the lower magnitude while after loading along [1 1 0] direction it relaxes up to the higher magnitude. Shubnikov-de Haas oscillations and Hall effect measurements indicate that variation of the carrier concentration j N in the quantum well during relaxation processes has different signs for uniaxial compression along [1 m 1 0] and [1 1 0] directions and correlates with the corresponding change of the resistance. The piezoelectric field that in GaAs can reach the magnitude E =1.152 2 10 6 V/m at uniaxial stress P =1 kbar along d 1 1 0 ¢ directions is supposed to be responsible for the metastable state after loading (unloading) and redistribution of carriers during the relaxation process. 相似文献
9.
T. Suzuki S. Onari H. Ito Y. Tanaka 《Physica C: Superconductivity and its Applications》2009,469(15-20):979-981
In order to clarify the mechanism of organic superconductor β-(BDA-TTP) salts. We study the superconductivity under uniaxial compression with non-dimerized two-band Hubbard model. We have calculated the uniaxial compression dependence of Tc by solving the Eliashberg’s equation using the fluctuation exchange (FLEX) approximation. The transfer integral under the uniaxial compression was estimated by the extended Huckel method.We have found that non-monotonic behaviors of Tc in experimental results under uniaxial compression are understood taking the spin frustration and spin fluctuation into account. 相似文献
10.
A. M. Savin N. Ya. Minina A. V. Polyanskiy C. B. Sorensen O. P. Hansen I. V. Berman 《高压研究》2013,33(2):267-270
Transport properties of two-dimensional electron and hole gas at (0 0 1) GaAs/Al x Ga 1 m x As heterointerface in [1 1 0] and [1 m 1 0] directions have been investigated for the first time under in plane uniaxial compression up to 5 kbar. Resistivity, Shubnikov-de Haas oscillations and Hall effect were measured and carrier densities and mobilities were determined. The in-plane uniaxial compression significantly modifies the energy spectrum of p-GaAs/Al x Ga 1 m x As that leads to strong anisotropy of hole mobility under compression. In the case of the n-type heterostructure uniaxial compression causes only change of the carrier concentration and the corresponding small change of the initial mobility anisotropy, determined by anisotropic surface roughness scattering. 相似文献
11.
V. S. Kuksenko B. Ts. Manzhikov K. Tilegenov Zh. K. Shatemirov B. É. Émil’bekov 《Physics of the Solid State》2003,45(12):2287-2291
The effect of weak low-frequency vibrations on the process of microfailure was studied. Cylindrical rock samples were subjected to uniaxial compression, during which low-frequency vibrations were periodically applied. The vibrations were weak as compared to the compressive load. Acoustic emission was monitored. The acoustic-emission signal was found to increase sharply after a delay when vibrations were applied for a short time (100–200 s). This effect was explained using the concentration criterion for the formation and development of a site of failure. 相似文献
12.
13.
Using transmission electron microscopy and electron diffraction, we
have investigated the microstructure of a
Zr55Al10Ni5Cu30 bulk metallic glass under a
uniaxial compression until a failure occurs at room temperature. It
is shown that the amorphous structure has changed locally in the
vicinity of the failure plane after the plastic deformation. An
increase in free volume is observed within the localized areas due to
the concentration of plastic flow, suggesting that the increasing of
local free volume dominates the deformation mechanism of the metallic
glass. The effect of free volume on the `serrated flow' behaviour in
the stress--strain curves during the uniaxial compression is
discussed. 相似文献
14.
用分子动力学方法模拟了沿〈001〉晶向应变加载和卸载情况下单晶铁中体心立方(bcc)与六方密排(hcp)结构的相互转变,分析了相变的可逆性和微结构演化特征.微观应力的变化显示样品具有超弹性性质,而温度变化表明在相变和逆相变过程中均出现放热现象.相变起始于爆发式均匀形核,晶核由块状颗粒迅速生长为沿{011}晶面的片状分层结构; 而卸载逆相变则从形核开始就呈现片状形态,且相界面晶面指数与加载相变完全一致,表现出形态记忆效应.在两hcp晶核生长的交界面易形成面心立方(fcc)堆垛层错. fcc通过在hcp晶粒内 相似文献
15.
The ability to achieve uniform stress in uniaxial compression tests of polycrystalline alumina is of significance for the calibration of piezospectroscopic coefficients as well as strength studies in ceramics. In this study high‐energy X‐rays were used to capture powder diffraction profiles over a half‐section of a polycrystalline alumina parallelepiped sample under an increasing uniaxial compressive load. The data were converted to strain and results were used for stress mapping of the sample. Stress maps from the study quantify the higher stresses at the sample–platen contact interface and reveal the evolution of the stress distribution in these specimens with load. For the geometry of the samples used, at the center section of the specimen the overall magnitudes of the compressive stresses were found to be 20% higher compared with the average expected theoretical stress based on the applied load and cross‐sectional area. The observed compressive stresses at the corners of the parallelepiped specimen were 62% higher and shear stresses were observed at the specimen interface to the load mechanism. The effects, seen at the interface, can lead to premature failure at these locations and can affect the accuracy of calibration of spectral peaks with stress as well as compression strength measurements. The results provide important information that can be used to establish guidelines on material and geometry considerations in developing compression tests on high‐strength ceramics. 相似文献
16.
本文采用第一性原理方法对清洁Cu∑5晶界与有B掺杂 到间隙位的Cu∑5晶界进 行了拉伸和压缩的模拟研究. 结果分析表明, Cu∑ 5晶界结合因B的掺入得到加强. 清洁Cu∑5晶界处因有较大空隙而存在电子密度低的区域, 晶界结合相对较弱, 在拉伸过程中晶界从其界面处开始断裂. 有B掺杂在间隙位的Cu∑5晶界电子由Cu向Cu-B间积聚, 晶界结合相对较强, 拉伸时晶界从其近邻原子层开始断裂. 在形变小于20%的压缩过程中, B的掺入未对晶界产生明显影响.
关键词:
第一性原理
Cu晶界
B掺杂
拉伸压缩 相似文献
17.
Mutasem A. Shehadeh 《哲学杂志》2013,93(10):1173-1197
Multiscale dislocation dynamics plasticity (MDDP) was used to investigate shock-induced deformation in monocrystalline copper. In order to enhance the numerical simulations, a periodic boundary condition was implemented in the continuum finite element (FE) scale so that the uniaxial compression of shocks could be attained. Additionally, lattice rotation was accounted for by modifying the dislocation dynamics (DD) code to update the dislocations’ slip systems. The dislocation microstructures were examined in detail and a mechanism of microband formation is proposed for single- and multiple-slip deformation. The simulation results show that lattice rotation enhances microband formation in single slip by locally reorienting the slip plane. It is also illustrated that both confined and periodic boundary conditions can be used to achieve uniaxial compression; however, a periodic boundary condition yields a disturbed wave profile due to edge effects. Moreover, the boundary conditions and the loading rise time show no significant effects on shock–dislocations interaction and the resulting microstructures. MDDP results of high strain rate calculations are also compared with the predictions of the Armstrong–Zerilli model of dislocation generation and movement. This work confirms that the effect of resident dislocations on the strain rate can be neglected when a homogeneous nucleation mechanism is included. 相似文献
18.
金刚石压砧的几何结构使得在高压下封垫内的样品通常处于单轴应力场中:压砧轴向加载应力最大,径向应力最小.由于金刚石压砧内非静水压单轴应力场的影响,用传统的高压原位X射线衍射方法测得的物质压缩曲线一般位于理想静水压压缩曲线之上.利用金刚石压砧径向X射线衍射技术以及晶格应变理论,结合最近的钨、金刚石和硼六氧样品的高压原位同步辐射径向X射线衍射实验结果,从宏观差应力、样品强度、标压物质和待测物质强度的关系三个方面分析讨论了金刚石压砧内单轴应力场对物质状态方程测量的影响及解决方案.
关键词:
金刚石压砧
单轴应力场
高压原位X射线衍射
状态方程 相似文献
19.
Yu. G. Nosov 《Physics of the Solid State》2011,53(12):2490-2491
A problem of variation in the refractive indices of the optically uniaxial crystal during its elastic deformation has been
considered. The stress has been applied along the optical axis of the crystal. It has been shown that, under uniaxial compression
of corundum and quartz, refractive indices of the ordinary and extraordinary rays converge but cannot be equal to each other. 相似文献
20.
Svirid A. E. Lukyanov A. V. Pushin V. G. Kuranova N. N. Makarov V. V. Pushin A. V. Uksusnikov A. N. 《Technical Physics》2020,65(7):1044-1050
Technical Physics - Cu–14 wt% Al–4 wt% Ni alloy demonstrating the shape memory effect has been subjected to plastic deformation by means of uniaxial compression (upset). The process has... 相似文献