高应变率下多尺寸聚丙烯纤维混凝土动态压缩力学性能研究

采用Φ74mm的分离式霍普金森压杆(Split Hopkinson pressure bar,SHPB)试验装置,对两种尺寸聚丙烯细纤维和一种尺寸聚丙烯粗纤维单掺及混掺的混凝土试件进行冲击压缩试验,对比分析粗、细纤维及不同纤维掺量比的多尺寸纤维混凝土试件在五种不同应变率下的动态压缩强度、动态压缩变形、动态压缩韧性和破坏特征,研究聚丙烯纤维混凝土的动态压缩力学性能。结果表明:随应变率的增加,素混凝土及纤维混凝土的动态压缩强度、动态压缩变形和动态压缩韧性表现出显著的应变率效应;在试验应变率范围内,粗聚丙烯纤维混凝土的动态抗压强度最高,相对素混凝土增幅为132.36%~213.85%;多尺寸聚丙烯纤维混凝土的动态强度增长因子与素混凝土基本一致;掺入多尺寸聚丙烯纤维可有效增大混凝土在不同应变率下的动态峰值应变和动态极限应变;多尺寸聚丙烯纤维混凝土的动态极限韧性较高,其中细聚丙烯纤维含量为1.2kg/m~3时混凝土动态极限韧性最高,增幅为121.11%。     

冲击载荷作用下应变率对砂岩力学性能的影响

借助于ANSYA/LS-DYNA数值分析软件对SHPB试验进行数值模拟,就不同应变率对砂岩力学性能的影响进行了研究,探讨了不同应变率对砂岩峰值应力、弹性模量、软化模量的影响规律,系统地分析了砂岩在不同应变率作用下的破坏规律。结果表明:随着应变率的增加,峰值应力显著增加,表现出较强的应变率相关性;应变率增大,弹性模量随之增大,但增长速率逐渐减小;应变率越大,软化模量反而降低。应变率ε从632.4 s-1变化到752.5 s-1时,软化模量由-2.98降到-4.18,降低了28.71%;当应变率ε大于752.5 s-1为1757.9时,软化模量仅降低了5%,说明应变率较大时变化趋势较为缓慢。高应变率下砂岩试件的动态压缩破坏主要呈现为轴向劈裂破坏。     

高应变速率作用下ZK60 镁合金的变形行为

对不同状态(热变形态、热变形+T5态和热变形+T6态)ZK60镁合金靶板进行了弹丸高速冲击(500 m/s)变形实验研究。结果表明,高速弹击实验后,在靶材弹孔背面出现了白亮的剪切唇,说明ZK60合金靶材具有较好的塑性,在高速弹击情况下,吸能性较好,具有较好的抗弹性。热变形+T5态ZK60镁合金靶板抗弹性较好,弹坑周围几乎不出现裂纹;通过线性回归分析,建立了弹坑深度与靶板材料力学性能之间的关系式,说明了当ZK60镁合金综合力学性能都较高时,材料就可获得优异的抗弹性。     

High Strain Rate Response of Sandwich Composites with Nanophased Cores

Polyurethane foam materials have been used as core materials in a sandwich construction with S2-Glass/SC-15 facings. The foam material has been manufactured from liquid polymer precursors of polyurethane. The precursors are made of two components; part-A (diphenylmethane diisocyanate) and part-B (polyol). In one set of experiments, part-A was mixed with part-B to manufacture the foam. In another set, TiO₂ nanoparticles have been dispersed in part-A through ultrasonic cavitation technique. The loading of nanoparticles was 3% by weight of the total polymer precursor. The TiO₂ nanoparticles were spherical in shape, and were about 29 nm in diameter. Sonic cavitation was carried out with a vibrasound liquid processor at 20 kHz frequency with a power intensity of about 100 kW/m². The two categories of foams manufactured in this manner were termed as neat and nanophased. Sandwich composites were then fabricated using these two categories of core materials using a co-injection resin transfer molding (CIRTM) technique. Test samples extracted from the panel were subjected to quasi-static as well as high strain rate loadings. Rate of loading varied from 0.002 s^–1 to around 1300 s^–1. It has been observed that infusion of nanoparticles had a direct correlation with the cell geometry. The cell dimensions increased by about 46% with particle infusion suggesting that nanoparticles might have worked as catalysts during the foaming process. Correspondingly, enhancement in thermal properties was also noticed especially in the TGA experiments. There was also a significant improvement in mechanical properties due to nanoparticle infusion. Average increase in sandwich strength and energy absorption with nanophased cores was between 40–60% over their neat counterparts. Details of manufacturing and analyses of thermal and mechanical tests are presented in this paper.     

High Strain Rate Compressive Tests on Woven Graphite Epoxy Composites

The behavior of composite materials may be different when they are subjected to high strain rate load. Penetrating split Hopkinson pressure bar (P-SHPB) is a method to impose high strain rate on specimen in the laboratory experiments. This research work studied the response of the thin circular shape specimens, made out of woven graphite epoxy composites, to high strain rate impact load. The stress-strain relationships and behavior of the specimens were investigated during the compressive dynamic tests for strain rates as high as 3200 s⁻¹. One dimensional analysis was deployed for analytical calculations since the experiments fulfilled the ratio of diameter to length of bars condition in impact load experiments. The mechanics of dynamic failure was studied and the results showed the factors which govern the failure mode in high strain deformation via absorbed energy by the specimen. In this paper, the relation of particle velocity with perforation depth was discussed for woven graphite epoxy specimens.     

镁合金在大变形和高应变率下塑性变形研究进展

介绍了强应变塑性大变形下镁合金研究现状.重点综述了在较高应变率及冲击载荷作用下关于镁合金变形的研究情况,同时也比较详细地综述了在不同温度、不同载荷作用下镁合金塑性变形特征及其物理机制.最后简要介绍了几个描述材料在较高应变率和冲击载荷作用下变形行为的数学表示式,并就镁合金作为结构材料的研究说明了作者的一些看法.     

应变率对泡沫铝压缩性能的影响

泡沫铝作为抗冲击及减震材料,很多场合都要经受冲压变形.目前,关于泡沫铝在压缩过程中表现出的应变率效应说法不一.概述了应变率对泡沫铝压缩性能的影响,结果表明,由于泡孔的变形特性使泡沫铝具有明显的应变率效应,泡孔在变形过程中的局部化、微观惯性和致密化是其对应变率敏感的根本原因.在高应变率下,滞留气体对闭孔泡沫铝的压缩有一定影响,开孔泡沫铝对应变率的敏感度还未有统一结论.     

PC/ABS在高应变率下的压缩大变形

目的对PC/ABS在高应变率下的压缩大变形行为进行实验研究与模拟。方法在应变率为1600~5000 s~(-1),温度为293~353 K的范围内,选用霍普金森压杆获取其在高应变率、高温下的大变形行为;选用DSGZ本构模型,模拟PC/ABS在高应变率下的大变形。结果 PC/ABS大变形行为强烈依赖于应变率和温度,屈服应力随应变率增加或温度降低而升高,大变形行为包括弹性、屈服、应变软化和应变硬化。结论DSGZ本构可准确模拟PC/ABS在高应变率、高温下的大变形行为。     

密度和应变率对聚苯乙烯泡沫(EPS)准静态压缩力学行为的影响

分别研究了聚苯乙烯泡沫(Expanded polystyrene,简称EPS)在三种不同密度和三种不同加载速率下的无侧限单轴准静态压缩力学行为.结果表明:EPS的压缩与一般多孔材料的压缩特征相似,其应力-应变曲线也分为三阶段(弹性段、塑性屈服平台段及致密段).并验证了聚苯乙烯泡沫(EPS)在线弹性阶段的弹性模量与其密度近似符合二次函数关系;通过对实验结果的拟合得出了EPS的密度与其屈服强度呈线性关系并给出了关系表达式.同时表明:同一密度的EPS在不同加载速率下其线弹性模量基本不变而屈服强度随加载速率的增加而显著增加,其应变率敏感度m值较大且变化显著,EPS表现出明显的应变率效应.     

温轧态2618A铝合金高应变速率超塑性的研究

对温轧态２６１８Ａ铝合金在不同温度（４７０～５５０℃）和应变速率为１０￣（－３）～１０￣（０）ｓ￣（－１）范围内的超塑性进行了研究，确定了最佳超塑性变形规范：在５００～５３０℃温度范围内，应变速率为２．８×１０￣（－１）ｓ￣（－１）的条件下，可获得大于２３０％的延伸率，表明该合金具有高应变速率超塑性的特性。     

高应变率下阻尼铝合金的动态力学性能研究

针对航空用高阻尼铝合金在高应变率载荷下的服役特征,研究了两种高阻尼铝合金在高应变率下的动态力学性能.采用分离式霍布金森(Hopkinson)压杆对高阻尼铝合金进行了动态压缩实验,获得了应变率(140,275,500s-1)对材料应力-应变曲线的影响规律,并同普通铸造铝合金ZL101A的动态压缩力学性能进行比较分析.结果表明:高阻尼铝合金在高应变率下的力学性能明显优于普通铸造铝合金;第一种高性能阻尼铝合金的动态压缩力学性能优异.第二种高性能阻尼铝合金随着应变率的提高,材料的弹性模量和应力均有所下降,但是形变强化效果显著.     

高应变速率下稀土镁合金的动态压缩性能研究

采用准静态试验机和分离式霍普金森杆（SHPB）对稀土镁合金进行压缩实验,并利用金相显微镜和扫描电镜进行显微分析,研究动态压缩下的力学性能,并探讨塑性变形和断裂的机制。结果表明：稀土镁合金的动态压缩应力-应变曲线对应变速率有一定的敏感性,塑性变形方式为滑移和孪生共同作用,断裂机制表现出对应变速率的敏感性。     

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…     

冲击速度对20Cr和40Cr钢应变速率、动态屈服强度作用的研究

研究了不同热处理状态的２０Ｃｒ和４０Ｃｒ钢在不同冲击速度（ｖ）下，应变速率（ε）和动态屈服强度（σα）的变化规律，研究表明：σα＝σ０ｅｘｐ（Ａｌｎε），ε＝ε０ｅｘｐ（Ｂｖ），σα＝σ０ｅｘｐ（Ｃｖ）．其中只有两个是独立的，并用粘塑性本构理论分析了微观作用机制。     

Strength of Metals at High Strain Rates

Results of metal testing in impact tension–compression and indentation are analyzed. As the analysis of these data demonstrates, the strength of metals increases greatly with strain rates and at moderate indentation rates. At high indentation rates, a decrease in the specific energy (per unit volume of a displaced material) necessary for the formation of a conical cavity was observed. The account of the effects of viscosity, temperature increase upon plastic deformation and its localization can be used to explain the above phenomena.     

高应变率下金属塑性损伤的形核机理

本文介绍了高应变率下金属塑性损伤形核模型的研究现状，并对现有的几种形核模型作了评述。     

轧制AZ31镁合金板材(4mm)动态压缩性能与失效行为

为了研究轧制AZ31镁合金板材(4mm)在高应变速率下的动态力学性能和失效行为,采用分离式霍普金森压杆装置(SHPB)在室温下应变速率为500～2600s-1范围内对其进行了动态压缩实验,并利用金相显微镜(OM)和扫描电镜(SM)对冲击后的试样进行了显微分析.探讨了轧制AZ31镁合金板材沿轧制方向(RD)、横向(TD)和法向(ND)的动态压缩性能和失效行为.结果表明:轧制AZ31镁合金4mm板材动态压缩性能存在各向异性.沿RD和TD方向压缩的动态性能相同,沿ND方向压缩的动态断裂强度最大.AZ31镁合金4mm板材的动态压缩断裂机制为解理断裂.变形机制为沿RD和TD方向高速压缩时,{101-2}<112-0>拉伸孪晶参与变形;沿ND方向高速压缩时,{101-1}<112-0>压缩孪晶参与变形.     

Effect of the Strain Rate on the Yield Strength of Steels of Different Strength

We present results of testing soft and high-strength steels for impact compression and show that the dependences of the compression resistance of tested metals on the level of strains are qualitatively similar. It is also shown that, as the strain rate increases, the compression resistance of the metals first strongly increases and then attains the zone of saturation in which the difference between the levels of compression resistance of these metals decreases. We also consider some specific features of the processes of deformation and fracture in the analyzed metals on the microstructural level.