紫外线辐照HDPE与尼龙－6相容性的研究

采用ＩＲ、ＳＥＭ、ＤＳＣ和拉伸应力－应变曲线研究了紫外线辐照ＨＤＰＥ／ＰＡ６的相容性，结果表明，随紫外线辐照时间的增长，ＨＤＰＥ分子链上引入Ｃ＝Ｏ－Ｃ－Ｏ－等极性基团明显增加；ＰＡ６的粒径减小，与基体间界面作用加强；两组分玻璃化温度差（Ｔ_（ｇ，ＰＡ６）－Ｔ_（ｇ，ＨＤＰＥ））减小；共混物拉伸应力－应变曲线上出现屈服点及拉伸冷流塑性形变。当辐照时间达１４４ｈ后，由于ＨＤＰＥ热稳定性明显变差，共混物韧性突降，拉伸应力－应变曲线上未出现屈服点。     

紫外线辐照HDPE与尼龙—6相容性的研究

采用ＩＲ，ＳＥＭ，ＤＳＣ和拉伸应力－应变曲线研究了紫外线辐照ＨＤＰＥ／ＰＡ６的相容性，结果表明，随紫外线辐照时间的增长，ＨＤＰＥ分子链上引入〉Ｃ＝Ｏ－Ｃ－Ｏ－等极基团明显增加；ＰＡ６的粒径减小，与基体间界面作用加强；两组分玻璃化温度差减小；共混物拉伸应力－应变曲线上出现屈服点及拉伸冷流塑性形变。     

冲击拉伸下Fe3Al力学性能的应变率相关性研究

利用自行研制的旋转盘式杆杆型冲击拉伸试验装置于Ｆｅ３Ａｌ实施了不同应变率的冲击拉伸试验，获得了不同应变率下的完整的应力应变曲线，结果表明在应变率从８０Ｓ＾－１至１２００Ｓ＾－１范围内，Ｆｅ３Ａｌ存在明显的动态韧性现象及应变率强化效应，其屈服应力，破坏应力以及破坏应变都随应变率的提高而增加，用最小二乘法拟合得到其屈服应力，破坏应力以及失稳应变与应变率的关系，并根据Ｂｏｎｄｎｅｒ－Ｐａｒｔｏｎ的理论建     

一种碳纤维织物增强复合材料的层间冲击拉伸力学性能实验研究

为获得一种碳纤维二维正交平纹机织布增强树脂基复合材料准静态和动态下的层间拉伸力学性能,对垂直于碳布平面方向 ( 横向),分别利用Instron试验机和SHTB实验技术,进行了准静态拉伸和动态拉伸实验。得到了从低应变率 (10-3/s) 到较高应变率 (约3×102/s) 下的拉伸应力-应变曲线和拉伸强度。通过分析发现,拉伸破坏总是发生在相邻铺层的层间界面处,层间拉伸模量和拉伸强度都具有一定的应变率强化效应,但是层间拉伸破坏应变几乎不存在应变率效应。      

铝合金LC4和LY24CZ在高应变率拉伸和压缩下的本构关系

对国产沉淀硬化铝合金（ＬＣ４和ＬＹ１２ＣＺ）进行静态和动态的拉伸与压缩试验研究。应变率范围为１０＾－４ｌ／ｓ－１０＾３ｌ／ｓ。结果表明，ＬＣ４和ＬＹ１２ＣＺ都是应变率不敏感材料，它们对变率的不敏感性可以用率相关位错理论来解释。试验还发现压缩应力－应变曲线高于拉伸应力－应变曲线，并用细观损伤的观点进行了初步探讨。     

α－钛／低碳钢爆炸复合界面结合层内的绝热剪切现象

本文利用光学显微镜和扫描电镜研究了α－钛／低碳钢爆炸复合界面结合层内α－钛侧产生的绝热剪切带（ＡＳＢ）的显微组织，表明ＡＳＢ内具有等轴晶组织特征，并且其内未发现微裂纹；显微硬度测量表明ＡＳＢ内的显微硬度比附近基体略高。并对ＡＳＢ这一现象从材料－力学－热学三方面进行了综合分析，认为，冲击载荷下绝热剪切是与速率相关的过程，应变率和应变都影响绝热剪切，材料本身的物理性能（定容比热Ｃ＿ｖ，密度ρ等），力学性能（如流变应力对应变率的敏感程度）和热性能（如热传导系数ｋ值）都影响ＡＳＢ的产生。     

熔体发泡法泡沫铝的力学性能研究

对采用熔体发泡法制造的不同密度泡沫铝进行了准静态压缩试验、拉伸试验和弯曲试验。结果表明,泡沫铝的压缩特性曲线包括线弹性变形区、平台区和密实化区。试样的高宽比H/D明显影响压缩应力-应变曲线。当H/D较小时,平台应力曲线较平滑;当H/D较大时,平台应力曲线剧烈波动,呈显著的锯齿状。且在试样中间部位出现与加载轴线呈25°—45°的剪切带。拉伸和弯曲过程中,泡沫铝应力快速增加,当达到应力峰值即屈服点后急剧减小,在最终破断失效前,没有明显的屈服变形带。压缩坪应力Rpl、拉伸屈服应力RUTS和冷弯屈服应力Rf随密度的增加而增加。     

铝合金LC4和LY12CZ在高应交率拉伸和压缩下的本构关系

对国产沉淀硬化铝合金（ＬＣ４和ＬＹ１２ＣＺ）进行了静态和动态的拉伸与压缩试验研究．应变率范围为１０－４ｌ／ｓ～１０３ｌ／ｓ．结果表明，ＬＣ４和ＬＹ１２ＣＺ都是应变率不敏感材料，它们对应变率的不敏感性可以用率相关位错理论来解释．试验还发现压缩应力－应变曲线高于拉伸应力－应变曲线，并用细观损伤的观点进行了初步探讨     

纤维束动态拉伸力学性能的实验研究

对Ｐｏｌｙｖｉｎｙ－ａｌｃｏｈｏｌ（ＰＶＡ），Ｅ－ｇｌａｓｓ和Ｋｅｖｌａｒ４９纤维束的应变率相关性和能量吸收能力进行了对比，冲击拉伸实验结果表明，除ＰＶＡ纤维束的初始弹性模量外，三种纤维束的力学性能均具有应变率相关性，其中ＰＶＡ和Ｅ－ｇｌａｓｓ的应变率敏感性较Ｋｅｖｌａｒ４９强烈；Ｋｅｖｌａｒ４９的能量吸收能力高于ＰＶＡ并且明显优于Ｅ－ｇｌａｓｓ。     

纳米二氧化硅改性超高韧性水泥基复合材料冲击压缩试验研究

该文采用Ф80 mm的分离式霍普金森压杆装置,研究了纳米改性后的UHTCC（ultra high toughness cementitious composites）在高速冲击压缩应力状态下的力学响应,并与常规UHTCC材料、钢纤维混凝土进行了对比。试验得到了各组材料在准静态和动态共计4组应变率（2.36×10-5 s-1、120 s-1、160 s-1、200 s-1）下的准静态压缩强度及冲击压缩应力-应变曲线,并计算了各组试件的耗能能力。为了进一步优化材料的抗冲击性能,该文还研究了纳米改性后的UHTCC基体中钢纤维和PVA纤维的混杂效果。试验结果表明:5组材料均具有应变率敏感性,峰值应力和耗能能力随着应变率的增大而上升;经过纳米改性后的UHTCC材料冲击压缩力学强度及耗能能力明显提高;在冲击荷载下,钢纤维和PVA纤维产生正混杂效应,提高钢纤维掺量可以强化UHTCC的抗冲击能力;应变率的大小和钢纤维的掺量之间的关系影响了动态峰值应力的提升。     

The effects of strain rate and CCVC interfacial layer on mechanical behaviours of CALL

In this paper, the loading and loading-unloading tests of CALL and CALL (CCVC) under tensile impact have been carried out by a self-designed Rotating Circular Disk Tensile impact Apparatus. The quasi-static tension and short beam bending tests are performed on the Shimadzu-5000 testing apparatus. Experiment results show that both CALL and CALL (CCVC) have positive hybrid effect. Under quasi-static tension, the two composites have no obvious yielding until fracture, but have an obvious yielding point on the dynamic tensile stress-strain curves. The dynamic unstable fracture strain is about three times the static unstable fracture strain. The interlaminar shear strength (ISS) of CALL (CCVC) is 10 more than that of CALL. At the same time, the tensile strength and unstable fracture strain of CALL (CCVC) are also higher than that of CALL. In this paper, some conclusions are also drawn from the SEM observation of the fracture specimen surfaces.     

Influence of stress state and strain rate on the behaviour of a rubber-particle reinforced polypropylene

This article presents an experimental investigation of a ductile rubber-modified polypropylene. The behaviour of the material is investigated by performing tension, shear and compression tests at quasi-static and dynamic strain rates. Subsequently, scanning electron microscopy is used to analyse the fracture surfaces of the tension test samples, and to relate the observed mechanical response to the evolution of the microstructure. The experimental study shows that the material is highly pressure and strain-rate sensitive. It also exhibits significant volume change, which is mainly ascribed to a cavitation process which appears during tensile deformation. Assuming matrix-particle debonding immediately after yielding, the rubber particles might play the role of initial cavities. It is further found that the flow stress level is highly dependent on the strain rate, and that the rate sensitivity seems to be slightly more pronounced in shear than in tension and compression. From the study of the fracture surfaces it appears that the fracture process is less ductile at high strain rates than under quasi-static conditions.     

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。     

An experimental study of stress wave transmission at a metallic-rock interface and dynamic tensile failure of sandstone, limestone, and granite

An experimental technique is described for determination of dynamic tensile fracture strength of brittle solids. This technique has been used to determine the dynamic tensile fracture strength of several types of rock. The rocks studied were granite, limestone, and sandstone; the specimens were cored perpendicular to the bedding plane for these rocks. The quasi-static fracture strengths of the same solids were also determined for comparison with the dynamic strengths. The dynamic strengths have been found to be several times the quasi-static strengths, thus showing a strong dependence of fracture strength on strain rate.     

金属钛拉伸的分子动力学研究

本文利用分子动力学的研究方法,采用了钛的嵌入式原子势,建立了沿[0001]晶向和[0110]方向拉伸模型,结果表明:两种方向的拉伸均包含弹性变形阶段、屈服阶段、颈缩阶段、断裂阶段.沿[0001]方向拉伸时,滑移系少,取向偏离软取向.变形时屈服强度为3.55GPa,屈服应变为0.063,断裂时的应变达到0.55.沿[01...     

高聚物纤维材料的高应变率响应行为研究

利用MTS和旋转盘式杆－杆型冲击拉伸试验装置，在高应变率、大应变率范围条件下（Aramid:0.01/s-1000/s;PVA:0.01/s-1500/s），研究了应变率对芳纶纤维和高强PVA纤维束力学性能的影响；同时，利用扫描电子显微镜考察了纤维材料在不同应变率下的微观断裂机理。     

Study on Dynamic Behavior and Tensile Strength of Concrete Using 1D Wave Propagation Characteristics

Concrete structures are usually fractured under dynamic loadings, so it is important to have a clear knowledge of their dynamic behavior and tensile strength. First, the principle of one-dimensional (1D) stress wave reflection and superposition at free surface is briefed, and the spalling test method based on the Hopkinson bar is presented. Then, the attenuation law of stress wave is explored and the dynamic tensile/compressive moduli of concrete are evaluated according to the wave propagation experiment. Lastly, the influences of strain rate on the spalling tensile strength and failure patterns of concrete are further analyzed. The testing results demonstrate that the attenuation of stress wave accords with an exponential law when propagating in the concrete bar. The difference between the dynamic elastic moduli of concrete in tension and in compression is minor. Spalling tensile strength is sensitive to strain rate, and there is an obvious linear correlation between dynamic increase factor (DIF) and strain rate in a log-log plot for strain rate above 1.0/s; a single fracture occurs at low strain rate, while multiple fractures are detected with increasing strain rate.     

Fatigue residual strength of circular laminate graphite–epoxy composite plates damaged by transverse load

The research dealt with the relation between damage and tension–tension fatigue residual strength (FRS) in a quasi-isotropic carbon fibre reinforced epoxy resin laminate. The work was organized in two phases: during the first one, composite laminates were damaged by means of an out-of-plane quasi-static load that was supposed to simulate a low velocity impact; in the second phase, fatigue tests were performed on damaged and undamaged specimens obtained from the original composite laminates. During the quasi-static transverse loading phase, damage progression was monitored by means of acoustic emission (AE) technique. The measurement of the strain energy accumulated in the specimens and of the acoustic energy released by fracture events made it possible to estimate the amount of induced damage and evaluate the quasi-static residual tensile strength of the specimens. A probabilistic failure analysis of the fatigue data, reduced by the relative residual strength values, made it possible to relate the FRS of damaged specimens with the fatigue strength of undamaged ones.     

Preparation of C200 green reactive powder concrete and its static–dynamic behaviors

In this paper, a new type of green reactive powder concrete (GRPC) with compressive strength of 200 MPa (C200 GRPC) is prepared by utilizing composite mineral admixtures, natural fine aggregates, short and fine steel fibers. The quasi-static mechanical properties (mechanical strength, fracture energy and fiber–matrix interfacial bonding strength) of GRPC specimens, cured in three different types of regimes (standard curing, steam curing and autoclave curing), are investigated. The experimental results show that the mechanical properties of the C200 GRPC made with the cementitious materials consisting of 40% of Portland cement, 25% of ultra fine slag, 25% of ultra fine fly ash and 10% of silica fume, 4% volume fraction of steel fiber are higher than the others. The corresponding compressive strength, flexural strength, fracture energy and fiber–matrix interfacial bonding strength are more than 200 MPa, 60 MPa, 30,000 J/m² and 14 MPa, respectively. The dynamic tensile behavior of the C200 GRPC is also investigated through the Split Hopkinson Pressure Bar (SHPB) according to the spalling phenomena. The dynamic testing results demonstrate that strain rate has an important effect on the dynamic tensile behavior of C200 GRPC. With an increase of strain rate, the peak stress rapidly increases in the dynamic tensile stress–time curves. The C200 GRPC exhibits an obvious strain rate stiffening effect in the case of high strain rate. Finally, the mechanism of excellent static and dynamic properties gains of C200 GRPC is also discussed.     

再生混凝土动态直接拉伸的试验研究

利用大直径(75 mm)分离式霍普金森拉杆(SHTB),对再生粗骨料取代率分别为0%、25%、50%、75%和100%的5组圆柱体再生混凝土试样进行应变率范围为100~102s-1的动态直接拉伸实验,研究再生混凝土的动态直接拉伸力学性能及其破坏形态。试验结果表明,再生混凝土的抗拉强度随平均应变率的增加而增大,而再生混凝土的破坏形态与平均应变率有关,这表明再生混凝土具有明显的率敏感性。在相同水灰比下,再生混凝土准静态拉伸强度比普通混凝土低1.3%~15.9%,动态拉伸强度比普通混凝土低1.7%~29%,此研究为再生混凝土的工程应用提供一定的理论依据。