Large elastoplastic deformation of a sample under compression and torsion in a rotational diamond anvil cell under megabar pressures
Large elastoplastic deformation of a sample under compression and torsion in a rotational diamond anvil cell under megabar pressures
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DOI：
10.1016/j.ijplas.2017.03.002
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发表时间：
2017-05
影响因子：
9.8
通讯作者：
B. Feng;V. Levitas
中科院分区：
文献类型：
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作者：
B. Feng;V. Levitas
高压和大塑性剪切下的材料行为通常在旋转金刚石对顶砧单元（旋转DAC，或RDAC）中进行研究。第一个模拟结果的三维塑性流动和演化的应力-应变状态下的RDAC压缩和扭曲的兆巴压力下的一个可拆卸的样品。利用弹塑性大变形理论。除了关于应力-应变场演化的定量信息之外，还获得了以下意想不到的结果。在初始压缩过程中，随后在固定轴向力下进行扭转，对于斜面砧，样品厚度减少了90倍。压力以及压力梯度在中心部分急剧增长，这种新现象被称为压力自聚焦效应。这种效应允许在相同的力下，RDAC中达到比DAC中高得多的最大压力。分析了金刚石和样品形状、屈服强度及其与压力的关系、摩擦系数和施加力对压力分布的影响。所得结果为提高最大可达压力开辟了新的途径，并为兆巴压力下的力学响应提供了新的直观认识，这将有利于实验中几何和加载条件的优化设计。
Material behavior under high pressure and large plastic shear is usually studied in a rotational diamond anvil cell (rotational DAC, or RDAC). The first modeling results for three-dimensional plastic flow and evolution of the stress-strain state for a rhenium sample compressed and twisted in RDAC under megabar pressures are presented. Large elastic and plastic deformation theory is utilized. In addition to quantitative information about evolution of the stress-strain fields, the following unexpected results are obtained. During initial compression followed by torsion under a fixed axial force and for beveled anvils, the sample thickness reduces by a factor of ninety. Pressure, as well as the pressure gradient, grow drastically at the central part, and this new phenomenon is called the pressure self-focusing effect. This effect allows a much higher maximum pressure to be reached in a RDAC than in a DAC under the same force. The effects of diamond and sample shape, yield strength and its pressure dependence, the friction coefficient, and applied force on the pressure distribution are analyzed. The obtained results open new ways to increase maximum achievable pressure and develop new intuition in mechanical responses at megabar pressures which will be beneficial to the optimum design of geometry and loading conditions in the experiment.