金属基复合材料的高应变速率超塑性

综述并评论了金属基复合材料的高应变速率超塑变形机制，描述了金属基复合材料在高应变速率超塑变形中的一些理化现象，说明了变形过程中的各种影响因素，总结了具有高应变速率超塑性能的金属基复合材料及其性能，并指出了在金属基复合材料的高应变速率超塑性研究方面的不足。     

较高应变速率下结构钢屈服强度的估计

本文给出了一种考虑应变速率效应时材料屈服强度近似求法，它依据两组低应变速率的拉伸试验数据，对其它应变速率下的屈服强度进行估计，并具有良好的精度。     

SiC颗粒增强6061Al基复合材料的动态拉伸性能Ⅱ应变速率效应

用拉伸split Hopkinson bar实验装置进行了SiCp/6061Al得合材料及基体合金的动态拉伸实验，研究了材料的应变速率敏感性。结果表明，SiCp/6061Al复合材料及其基体合金均具有明显的应变速率效应，且复合材料的应变速率敏感性高于基体合金的应变速率敏感性，根据位错机制对此进行了解释。     

拉伸试验的速率探讨

采用夹头分离速率控制方式对：行屈服现象和无屈服现象的试样进行拉伸试验，探讨了试验过程中试样应变速率和应力速率的变化情况。试验结果表明：在不同的变形阶段试样的应变速率是不同的，弹性阶段的应变速率比设定值低很多，屈服阶段会略高，塑性变形阶段与设定值较接近。并确定在该试验条件下可将试验速率设定在1～7mm／min。     

速率相关混凝土模型中一个值得商榷的问题

本文对一种广泛应用于钢筋混凝土结构动力分析的速率相关的混凝土模型进行讨论，该模型的基本特征是粘性参数与应变速率有关。为了比较和验证该模型的正确性，本文严格按照弹粘塑性理论并结合过应力概念，提出了一种应变速率相关模型。文中给出了在常应变速率、应力松弛和蠕变等加载情况下二种模型的分析解。理论和数值计算结果都表明，先前提出的应变速率相关模型不仅理论上有缺陷，而且在稳态响应阶段段值计算存在较大误差。     

Ti2AlNb合金应变速率敏感指数和应变硬化指数与变形参数和晶粒尺寸关系研究

以Ti₂AlNb合金板材为研究对象，基于变形温度为1 273～1 423 K、应变速率为0.001～10 s^-1范围内的等温恒应变速率热压缩实验，深入分析了变形参数和微观组织对应变速率敏感指数m和应变硬化指数n的影响。结果表明：Ti₂AlNb合金的流动应力随变形温度的升高和应变速率的降低而减小；Ti₂AlNb合金等温压缩过程中的峰值m为0.61，出现在1 323 K/0.001 s^-1；当变形温度为1 273～1 323 K时，m随应变速率的增大而减小，当变形温度为1 373～1 423 K时，m随应变速率的增大而增大；当应变速率为0.001 s^-1时，n随应变的增大呈现先减小后增大的趋势，而当应变速率为0.01～10 s^-1时，n却呈现先增大后减小的变化趋势；Ti₂AlNb合金应变硬化指数n值和应变速率敏感指数m值均随着晶粒尺寸的增大而减小；Ti₂AlNb合金板材较优的加工区间为1 273...     

Zn-5Al超塑合金的恒载荷拉伸实验研究

研究表明，Zn-5Al超塑性合金的应变速率敏感指数m和超塑性变形激活能Q值和超塑性流动粘滞系数η可采用恒载荷蠕变法进行测定，在恒载荷变形条件下，应变速率敏感指数m随应变速率的增加而增大，超塑性流动的粘滞系数η随应变速率的增加而减小，超塑拉伸前对轧态试样进行保温处理时，由于通过回复和再结晶释放了合金中的储能，降低了超塑变形的动力，导致变形抗力增加而延伸率下降。     

热变形参数对Ti-6554合金流动软化行为的影响

目的 研究不同热变形参数下Ti-6554合金对应变速率敏感指数m、应变硬化指数n的影响。方法 采用Gleeble-3500热模拟实验机，在变形温度为810~930 ℃、应变速率为0.001~10 s⁻¹条件下，对Ti-6554合金进行等温恒应变速率热压缩实验。结果 应变速率敏感指数m随应变速率的升高和变形温度的降低而减小，当真应变为0.9时，m在变形温度为930 ℃、应变速率为0.001 s⁻¹的条件下达到峰值，为0.43。应变硬化指数n随应变速率的升高呈先升高后降低的趋势，在高温区间(870~930 ℃)的软化程度较大。结论 Ti-6554合金对变形温度、应变速率等热变形参数十分敏感，该合金的流动应力随着应变速率的升高和变形温度的降低而增大。分析微观组织可知，从应变速率敏感指数m角度考虑，该合金发生软化行为的最佳区域是变形温度为870~930 ℃、应变速率为0.001 s⁻¹。从应变硬化指数n的角度考虑，在变形温度为870~930 ℃条件下，Ti-6554合金在低应变速率区间(0.001~0.01 s⁻¹)的软化行为以动态再结晶(DRX)为主，在高应变速率区间(0.1~10 s⁻¹)的软化行为以动态回复(DRV)为主。     

Ti－17合金的热压缩变形行为研究

通过热模拟压缩试验，测试了Ｔｉ－１７合金在温度Ｔ＝８０５～９４５℃，应变速率ε＝１０（－３）～８０ｓ（－１）、变形程度ε＝５０％范围内的真应力－应变曲线，研究了不同温度、不同应变速率下的流动应力及组织变化规律。发现，在（α＋β）两相区降低温度或提高应变速率，流动应力σ变化较大，动态再结晶易于进行；在β区通常只发生动态回复，流动应力σ随温度和应变速率变化较小，高温、低应变时发生连续再结晶。试验还用Ｚｅｎｅｒ－Ｈｏｌｌｏｍｏｎ因子确定了该台金发生连续再结晶的临界因子Ｚｃ的数值，ｌｏｇＺＣ＝４１．２。     

Ti─17合金高温变形机理研究EI

用热模拟压缩试验研究了Ｔｉ－１７合金高温变形特点，通过金相组织和ＴＥＭ观察发现，β区变形是以扩散回复型变形机制占主导地位；高应变速率下只发生动态回复；低应变速率下发生连续再结晶。（α＋β）区变形是界面滑移，高应变速率下易发生动态再结晶。试验还确定了变形激活能Ｑ和应变速率敏感因子ｍ值，β和（α＋β）区中分别为１６１ｋＪ／ｍｏｌ、４３７ｋＪ／ｍｏｌ和０．３２、０．２５。     

高强高模聚乙烯纤维力学性能的应变率和温度效应

利用MTS810材料试验机、旋转盘式杆-杆型冲击拉伸装置和温度控制箱,在温度20℃~110℃、应变率为0.001/s~700/s范围内,对高强高模聚乙烯纤维束进行了准静态和高应变率冲击拉伸实验,得到了不同温度、不同应变率时纤维束的应力-应变曲线。结果表明:高强高模聚乙烯纤维束的初始弹性模量具有应变率和温度相关的特性,随应变率提高而增加,随温度提高而下降;在常温下,破坏应力从准静态到动态,具有明显的应变率相关性,随应变率提高而增加,但在20℃~110℃范围内、高应变率下,对应变率变化不敏感;失稳应变也具有应变率和温度相关的特性,随应变率提高而减小,随温度提高而增大。在高应变率下,断裂应变能密度主要由初始弹性模量和失稳应变共同决定,受温度效应和应变率效应的综合影响。     

Effect of Strain Rate on Compression Behavior of Vinyl Ester Resin Casting

Vinylesterresin(VE)isoflowdensityandcor rosionresistant,andtheprocessperformanceiswell.Becauseunsaturateddoublecrossbondslieonthe twoendingofmolecularchain,thewholemolecular chainwillelongateandabsorbmechanicalenergyun derforcing,andthenpossessesgoodabilityofimpact andcrackresistant.Thehydroxylsinthemolecular chainmakeVEinfiltrateglassfiber,aramidfiberand UHMPEfiberetc.verywell[1],soVEisanother wildlyusedandstudiedresinfollowedepoxyresin.Intherecentyears,ithasbeenreportedthattheVE resinha…     

Strain Rate Dependence of Tensile Properties of Extruded Mg–9Y–3Zn–1Mn Alloy

Tensile mechanical properties of an extruded Mg–9Y–3Zn–1Mn alloy are investigated at a wide range of strain rates. It is demonstrated that the tensile ductility of the alloy exhibits a pronounced strain rate dependence, while its tensile strength is less sensitive to strain rate. As strain rate decreases from to , the yield and ultimate tensile strengths of the alloy only decrease by 13% and 7% (from 237 and 320 MPa to 206 and 295 MPa), while its uniform and total elongations increase by 173% and 176% (from 10.12% and 11.53% to 27.62% and 29.32%), respectively. The results of the above tensile tests are analyzed by the characterizations of microstructure and morphologies of deformation surface and the measurements of strain hardening rate and strain rate sensitivity. It reveals that the less sensitive strain rate dependence of the tensile strengths arises from the reversed contributions of the precipitation strengthening role and the softening role caused by the grain boundary (GB) deformation; the pronounced strain rate dependence of the tensile ductility is attributed to the enhanced stress relaxation role of the GB deformation and the high deformation accomodation capability caused by the long period stacking ordered (LPSO) phase and stacking faults (SFs).

     

高抗冲聚苯乙烯的应变率敏感性及粘塑性本构关系

对高抗冲聚苯乙烯（HIPS）在应变跨越10^-4-10^1量级的范围内的拉伸力学性能作了实验研究，实验结果显示HPIS是一种应变率敏感的材料，其拉伸力学性能对应率敏感程度可分为高中低三个区域，在此基础上讨论了这类材料的粘塑性本构关系。     

Strain rate concentration and dynamic stress concentration for double‐edge‐notched specimens subjected to high‐speed tensile loads

Engineering plastics provide superior performance to ordinary plastics for wide range of the use. For polymer materials, dynamic stress and strain rate may be major factors to be considered when the strength is evaluated. Recently, high‐speed tensile test is being recognized as a standard testing method to confirm the strength under dynamic loads. In this study, therefore, high‐speed tensile test is analysed by the finite element method; then, the maximum dynamic stress and strain rate are discussed with varying the tensile speed and maximum forced displacement. The maximum strain rate increases with increasing the tensile speed u/t, but the strain rate concentration factor is found to be constant independent of tensile speed, which is defined as the maximum strain rate appearing at the notch root over the average nominal strain rate at the minimum section . It is found that the strain rate at the notch root depends on the dynamic stress rate at the notch root and independent of the notch root radius ρ. It is found that the difference between the static and dynamic maximum stress concentration (σ_yA,max ? σ_yA,st) at the notch root is proportional to the tensile speed when u/t = 5000 mm/s. Strain rate concentration factors are also discussed with varying the notch depth and specimen length. Based on the elastic strain rate concentration factor, the master curve is obtained useful for understanding the impact fracture of polycarbonate for the wide range of temperature and impact speed.     

纤维束的冲击拉伸实验研究

本文所述实验采用岛津DT-5000型万能实验机和自行研制的摆锤式杆-杆型冲击拉伸试验装置对玻璃纤维,Kevlar49及碳纤维束做了应变率从10-4到 102 s-1量级之间的冲击拉伸实验。首次得到纤维束在高应变率下的拉伸应力应变曲线。结果表明:玻璃纤维的强度,极限应变以及临界应变能密度对应变率非常敏感,弹性模量也随应变率的升高而增加。Kevlar49纤维对应变率不太敏感,而碳纤维的性能则对应变率不敏感。     

UHMWPE交织双轴向纬编复合材料高应变率压缩性能研究

利用SHPB装置对UHMWPE交织双轴向纬编针织物/乙烯基酯树脂复合材料进行了高应变率压缩实验,研究了该材料的应变率效应和能量吸收.结果表明:等离子体处理后,复合材料的高应变率压缩性能有了较大的提高,放电功率100W是一个较为合适的处理条件.UHMWPE交织双轴向纬编复合材料呈现出一定的应变率敏感性:随着应变率的增加,最大应力、压缩模量、断裂应变能密度相应增大.由于交织双轴向纬编结构中的针织线圈及经纬纱交织作用,其具有较好的抗冲击性能.     

Influence of strain rate on ultimate tensile stress of coarse-grained and ultrafine-grained copper

In the present paper OFHC (oxygen free high conductivity) copper was tested by static and dynamic tensile tests at room temperature owing to strain rate investigation. Because of coarse-grained (CG) and ultrafine-grained (UFG) microstructure observation the copper was subjected to drawing and ECAP processes. The investigation of strain rate and microstructure was focused on the ultimate tensile stress (UTS) after the tensile tests. Following this study, it was found that strain rate is an important characteristic influencing the mechanical properties of copper. The ultimate tensile stress grew with strain rate increasing and this effect is more visible at high strain rates ( ~ 10² s⁻¹). Moreover, it was revealed that strain rate hasn't got any influence on the failure mechanism of the copper on the other hand it has an influence on the values of dimple size. While strain rate increases the dimple size decreases.     

Dynamic response for porous epoxy resin matrix composites filled with iron powder at different strain rates and constitutive relationships

The porous epoxy resin matrix composites filled with iron powder referenced in this work consist of both ferromagnetic base materials and porous materials, which have properties of electromagnetic shielding and impact energy absorbing. Aimed at the dynamic compressive properties of the composites at different high strain rates, two materials were studied: the first is Fe/ER-17 with 40% porosity and 17% mass fraction of iron powder; the other is Fe/ER-90 with 10% porosity and 90% mass fraction of iron powder. The investigation results showed: (1) the quasi-static compressive failure strengths of the two composites are much lower than their dynamic compressive failure strengths; (2) Fe/ER-17 exhibits obvious characteristics of a porous material at high strain rates (≥3000/s), whereas FE/ER-90 exhibits a visco-elastic response at all strain rates; (3) Fe/ER-17 and Fe/ER-90 show a strain rate hardening effect on dynamic yield strengths. The dynamic yield strengths of Fe/ER-17 change from 19.23 MPa at a strain rate of 850/s to 30.97 MPa at a strain rate of 6000/s, and dynamic yield strengths of Fe/ER-90 change from 114.93 MPa at a strain rate of 700/s to 136.95 MPa at a strain rate of 3600/s. The hardening effect of dynamic yield strengths is linear with the strain rate, and their linear strain rate hardening factors are very small (10 × 10^?4 and 0.6 × 10^?4, respectively). A constitutive model of series form for a porous material and a modified ZWT constitutive model for a visco-elastic material were adopted for Fe/ER-17 and Fe/ER-90, respectively. The constitutive relationships developed captured the dynamic compressive characteristics of the two materials.