FEM simulation of large deformation of copper in the quasi-constrain high-pressure-torsion setup
FEM simulation of large deformation of copper in the quasi-constrain high-pressure-torsion setup
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DOI：
10.1016/j.msea.2017.08.078
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发表时间：
2017-09-29
期刊：
影响因子：
6.4
通讯作者：
Feng, Biao
中科院分区：
文献类型：
--
作者：
Kamrani, Mehdi;Levitas, Valery I.;Feng, Biao
高压扭转(HPT)技术被广泛应用于引入大塑性变形，以获得性能更好的超细晶材料或促进相变，从而导致新相的出现。用有限元方法研究了准约束位形下铜试件在压力和扭转作用下的行为。给出了一套完整的弹性小变形和大塑性变形和转动方程。接触摩擦条件包括库仑滑动和塑性滑动。研究了应力张量分量场、静水压力场和等效塑性应变场的演化规律。研究了应变硬化饱和的临界应变m和不同摩擦条件的影响。塑性应变沿试件半径和厚度方向均表现出很强的非均质性，这不能用已知的近似公式很好地描述。样品的扭矩-旋转角响应对m值不敏感，但强烈依赖于砧座与飞边之间的摩擦系数。主要结论是，文献中从HPT得到的m值(从4.8到20)被高估了，应该使用均匀压缩试验中得到的m=1.57。
High pressure-torsion (HPT) technique is widely used to introduce severe plastic deformation in order to obtain ultrafine-grained materials with improved properties or to enhance the phase transformation which may result in an appearance of new phases. The behavior of the copper sample under pressure and torsion in a quasi constraint configuration is studied using finite element method (FEM). A complete system of equations for small elastic and large plastic deformations and rotations is presented. Contact friction conditions include combined Coulomb and plastic sliding. The evolution of the distribution of fields of components of the stress tensor, hydrostatic pressure, and equivalent plastic strain are studied. The effects of the critical strain for saturation of strain hardening, m, and different friction conditions are investigated. Strong heterogeneity of the plastic strain both along the radius and thickness of the sample is found, which is not well described by known approximate expressions. Torque-rotation angle response of the sample is not sensitive to the value of m but strongly depends on the friction coefficient between anvil and flash. The main conclusion is that the value of m obtained in literature from HPT (from 4.8 to 20) is highly overestimated and m = 1.57 obtained in a homogeneous compression test should be used.