Coupled elastoplasticity and plastic strain-induced phase transformation under high pressure and large strains: Formulation and application to BN sample compressed in a diamond anvil cell
Coupled elastoplasticity and plastic strain-induced phase transformation under high pressure and large strains: Formulation and application to BN sample compressed in a diamond anvil cell
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高压和大应变下耦合弹塑性和塑性应变诱导的相变：在金刚石砧室中压缩的 BN 样品的配方和应用
DOI：
10.1016/j.ijplas.2017.05.002
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发表时间：
2017-09-01
影响因子：
9.8
通讯作者：
Levitas, Valery I.
中科院分区：
文献类型：
--
作者：
Feng, Biao;Levitas, Valery I.
为了研究高压相变（PT），通过在金刚石压砧单元（DAC）中的高强度垫圈内压缩薄样品来产生高静压。然而，由于PT发生在塑性流动期间，因此在此将其分类并作为塑性应变诱导PT处理。结合塑性流动和塑性应变引起的PT的方程组的一个一致的系统，制定大的弹性，塑性和转换应变。Murnaghan弹性定律，压力相关的J（2）塑性（都依赖于高压相的浓度），和塑性应变诱导和压力相关的PT动力学。提出了一种有限元计算算法，并在有限元程序ABAQUS的用户材料子程序（UMAT）中实现。结合塑性流动和应变诱导PT从高度无序的六方氮化硼（hBN）样品的超硬wBN内模拟压力高达50 GPa的密封垫。的应力和塑性应变，以及在样品中的相的浓度的字段的演变得到并详细讨论。给出了垫片和金刚石的应力应变场。发现了一个意外的形状的变形样品与几乎完整的PT在外部的样品，穿透垫片的部分。获得的结果表明，材料和系统的行为之间的差异，这是经常混淆的实验学家。因此，虽然塑性应变诱导的PT可能在塑性应变略高于6.7 GPa时开始（和结束），但在低于12 GPa时不可见。它在21 GPa下变得可检测，并且即使在50 GPa的最大压力下也不会在样品中的任何地方完成。由于强密封垫的存在，压力梯度远小于塑性应变梯度，因此高压相的分布主要由塑性应变场而不是压力场决定。可能的误解的实验数据和表征的PT进行了讨论。所开发的模型将允许计算设计的高压相合成实验。(C)2017爱思唯尔有限公司版权所有
In order to study high-pressure phase transformations (PTs), high static pressure is produced by compressing a thin sample within a high strength gasket in a diamond anvil cell (DAC). However, since a PT occurs during plastic flow, it is classified and treated here as a plastic strain-induced PT. A thermodynamically consistent system of equations for combined plastic flow and plastic strain-induced PTs is formulated for large elastic, plastic, and transformation strains. The Murnaghan elasticity law, pressure-dependent J(2) plasticity (both dependent of the concentration of a high-pressure phase), and plastic strain-induced and pressure-dependent PT kinetics are utilized. A computational algorithm within finite element method (FEM) is presented and implemented in a user material subroutine (UMAT) in the FEM code ABAQUS. Combined plastic flow and strain-induced PT from the highly disordered hexagonal boron nitride (hBN) sample to a superhard wurtzitic wBN is simulated within the rhenium gasket for pressures up to 50 GPa. The evolution of the fields of stresses and plastic strains, as well as the concentration of phases in a sample is obtained and discussed in detail. Stress-strain fields in a gasket and diamond are presented as well. An unexpected shape of the deformed sample with almost complete PT in the external part of the sample that penetrated the gasket was found. Obtained results demonstrated the difference between material and system behavior which are often confused by experimentalists. Thus, while plastic strain-induced PT may start (and end) at plastic straining slightly above 6.7 GPa, it is not visible below 12 GPa. It becomes detectable at 21 GPa and is not completed everywhere in a sample even at a maximum pressure of 50 GPa. Due to a strong gasket the gradient of pressure is much smaller than the gradient of plastic strain, and therefore the distribution of the high pressure phase is mostly determined by the plastic strain field instead of the pressure field. Possible misinterpretation of the experimental data and characterization of the PT is discussed. The developed model will allow computational design of experiments for synthesis of high-pressure phases. (C) 2017 Elsevier Ltd. All rights reserved.