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为了研究材料在高应变率拉伸加载下的动态响应,利用新型爆炸膨胀环实验技术开展了无氧铜试
样环的拉伸加载实验,采用激光干涉测试技术获得了试样环拉伸变形过程的径向速度历史。数值计算发现经
典JC模型不能较好地描述无氧铜试样环的膨胀过程,于是对JC模型进行了修改:增加了应变的指数硬化项
来描述拉伸变形的累积效应;增加了应变率的线性项描述拉伸加载时的应变率效应;利用实验数据拟合了修
改后的RJC模型参数,最终较好描述了无氧铜试样环的膨胀变形过程。 相似文献
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膨胀环实验技术主要包括爆炸膨胀环实验技术和电磁膨胀环实验技术,实验过程中膨胀环的加载应变率在达到峰值后会随着圆环的膨胀而迅速降低,给研究应变率敏感材料的拉伸碎裂带来极大的不便。在前期提出的液压膨胀环实验技术的基础上,发展了一种恒应变率加载技术。首先,从理论上获得了实现金属圆环恒应变率膨胀所需的液压加载曲线的近似表达式;然后,采用有限元流固耦合数值模拟了液压膨胀环装置中1060-O铝环的膨胀碎裂过程,在给定液压加载曲线下,膨胀环的环向应变率在应变率稳定阶段上下波动范围最大不超过20%;并进一步研究了加载曲线对碎裂过程中应变率的影响规律。在液压膨胀环实验装置上对1060-O铝环开展了膨胀环实验,验证了恒应变率加载技术的可行性。 相似文献
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考虑断面收缩率、局域断裂应变以及平均断裂应变,并基于电磁膨胀环、爆炸膨胀环(柱壳)实验平台,研究了高纯无氧铜(TU1)环及柱壳在高应变率载荷下的膨胀断裂行为。采用高速摄影技术拍摄柱壳外壁的膨胀断裂形貌演化过程,用于确定柱壳平均断裂应变;利用激光干涉测速技术获得样品径向膨胀速度历史,用于确定加载应变率;利用样品的全回收测量及微观表征,确定了无氧铜环、柱壳的局域断裂应变及断裂模式。实验表明,随着应变率的增加,TU1材料的平均断裂应变增加,断面的收缩程度加剧,并在应变率约为1.0×104 s-1附近会出现明显的断裂模式转变,断面收缩率出现量级上的跳跃,从100变化至约103,局域断裂应变呈现明显的分区现象。 相似文献
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一种新型爆炸膨胀环实验装置 总被引:1,自引:0,他引:1
传统爆炸膨胀环实验装置采用两端点起爆,爆轰波对碰后加载驱动器的方式,出现试样环加载后侧向翻转、实验重复性差等问题.本文改进传统爆炸膨胀环实验装置中的起爆方式,研制了一种新型爆炸膨胀环实验装置.新起爆方式采用轴心爆炸丝同步线起爆,在驱动器内形成理想的柱面冲击波,有效避免了试样环受冲击后发生侧向翻转,实现了金属试样环的稳定拉伸加载,实验效率得到大幅提高. 相似文献
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内爆炸加载条件下圆筒的膨胀、破裂规律研究 总被引:7,自引:0,他引:7
以经典热粘塑性本构关系 (John Cook本构关系和Powerlaw本构关系 )为基础 ,建立了更适当表征材料特征的新的、解耦的本构关系。采用SHPB(分离式霍普金森杆 )技术测定了常用弹箭材料 35CrMnSiA的不同应变率下的应力、应变关系 ,并采用拟合的方法确定了本构方程中的材料常数。与高速摄影技术测得的径向位移函数及圆筒材料的损伤演化方程相结合 ,建立了控制内爆炸加载圆筒膨胀 ,直至破裂的完备方程组 ,完成了内爆炸加载圆筒问题的数值模拟 ,计算结果与以往有关箭弹材料圆筒膨胀的实验结果符合较好。 相似文献
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采用Hopkinson装置和一种基于一级气体炮的高速冲击拉伸断裂装置,研究了无刻槽高导无氧铜
(OFHC)杆在一系列冲击拉伸速度下的断裂。当冲击拉伸速度大于40m/s时,断裂位置总在冲击拉伸端附
近,此速度被确定为OFHC的实验临界冲击拉伸速度。一种受单轴冲击拉伸荷载的、中心含椭球空穴的样本
体积单元被用于数值模拟所含空穴的增长与失稳的过程。OFHC的J-C与Z-A 本构关系用于描述基体材料
的动态响应。讨论了空穴失稳条件并提出以空穴形状演化为判据,比较了空穴失稳时的样本体积单元平均径
向应变与无刻槽杆的冲击断裂应变。也用这种样本体积单元模型分析了OFHC的实验临界冲击拉伸速度。 相似文献
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利用任意反射面位移干涉系统(DISAR)激光测速技术,成功地获得了滑移内爆加载和柱壳结构条件下无氧铜的内表面(自由面)速度剖面,并对其层裂特性进行了初步分析。结果表明:(1)在固定炸药和改变无氧铜圆管壁厚条件下,层裂片厚度随着圆管壁厚h的减小而增加;以圆管壁厚h为参照进行归一化,则相对层裂片厚度(/h)随相对装药厚度(he/h)的增大而增加,这种规律与以往对20钢的研究结果一致,但圆管发生层裂的临界条件,却显示出明显的材料相关性。(2)初步来看,无氧铜的层裂强度对结构的依赖性不明显,而与加载脉冲的幅值和宽度相关。(3)受无氧铜粘性和Taylor波衰减的影响,无氧铜的层裂强度随管壁厚度的增加而略有降低;同时,材料分散性也对此有一定影响。 相似文献
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Fragmentation of metal rings by electromagnetic loading 总被引:9,自引:0,他引:9
A method is described for performing fragmentation studies on rapidly expanding metal rings. A fast-discharge capacitor system
generates magnetic forces which accelerate the rings to maximum radial velocities of approximately 200 m/s corresponding to
circumferential-strain rates of approximately 104/s at fragmentation. Streak-camera techniques are used to record the time-resolved motion of the rings. Fracture-strain and
fragmentation experiments have been performed on samples of OFHC copper and 1100-0 aluminum. 相似文献
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To observe the plastic wave propagation, an experimental setup is designed with a SHPB facility and a high speed digital camera.
Two types of OFHC copper were selected as specimen materials: in the cold work condition and after total annealing, which
represent non strain hardening and strain hardening material respectively. The rise time of incident impulse in the SHPB test
is relevant to bar’s radius. A maximum allowable specimen length and a maximum allowable impact velocity (MAIV) of striker
are proposed for the SHPB test. The propagation of plastic waves is observed along specimen length at the beginning of specimen’s
plastic deformation in SHPB test. However, for both types of material, no plastic wave motion is caught along specimen length
for large plastic strain level. Side confinement effect of friction is found to be significant, even with lubricant in the
experiment. 相似文献
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利用一级气炮对高导无氧铜(OFHC)进行了圆柱以205 m/s速度冲击平板实验,并进行了数值模拟。用锰铜应力计测试了靶中应力随时间的变化,并进行了回收观测。采用Johnson-Cook(J-C)、Zerilli-Armstrong(Z-A)、Steinberg-Cochran-Guinan(S-C-G)3种本构模型对实验进行了数值模拟。实验结果与数值模拟结果比较表明:就峰值应力而言,采用J-C、Z-A及S-C-G本构模型的计算结果都比较接近实验;就圆柱变形而言,Z-A及S-C-G模型的计算较J-C模型结果更符合实验。然而,速度为500 m/s冲击实验的数值模拟结果表明:3种本构模型的计算结果差异明显。 相似文献
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The material properties of an oxygen-free high thermal conductivity (OFHC) film with a thickness of 0.1 mm were evaluated
at strain rates ranging from 10−3/s to 103/s using a high-speed material micro-testing machine (HSMMTM). The high strain-rate material properties of thin films are
important especially for an evaluation of the structural reliability of micro-formed parts and MEMS products. The high strain-rate
material testing methods of thin films, however, have yet to be established to the point that the testing methods of larger
specimens for electronics, auto-body, train, ship, and ocean structures are. For evaluation, a new type of HSMMTM was developed
to conduct high-speed tensile tests of thin films. This machine is capable of testing at a sufficiently high tensile speed
with an electromagnetic actuator, a novel gripping mechanism, and an accurate load measurement system. The OFHC copper film
shows high strain-rate sensitivity in terms of the flow stress, fracture elongation, and strain hardening. These measures
increase as the tensile strain rate increases. The rate-dependent material properties of an OFHC copper film are also compared
with those of a bulk OFHC copper sheet with a thickness of 1 mm. The flow stress of an OFHC copper film is relatively low
compared to that of a bulk OFHC copper sheet in the entire range of strain rates, while the fracture elongation of an OFHC
copper film is much larger than that of a bulk OFHC copper sheet. A quantitative comparison would provide material data at
high strain rates for the design and analysis of micro-appliances and different types of micro-equipment. 相似文献
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《International Journal of Plasticity》2000,16(5):525-540
An Eulerian hydrocode was used to simulate the dynamic void collapse in OFHC copper, modeled with the Johnson–Cook (Johnson, G.R., Cook, W.H., 1985. Engineering Fracture Mechanics 21(1), 31) material model and the Cruneisen equation of state, to study hot spot formation and jetting. The computational techniques were first validated by a comparison to a series of two-dimensional experiments. The effect of the planar and axisymmetric geometries on the hot spot temperature and jet velocity in circular voids is explored. In addition, the effect of the apex angle in triangular voids on jetting and hot spot formation is studied. An effective apex angle for the highly nonspherical voids formed in closely packed circular particles is calculated. 相似文献