A continuum dislocation-based model of wedge microindentation of single crystals
A continuum dislocation-based model of wedge microindentation of single crystals
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DOI：
10.1016/j.ijplas.2018.10.008
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发表时间：
2019-03
影响因子：
9.8
通讯作者：
G. Po;Yue Huang;N. Ghoniem
中科院分区：
文献类型：
--
作者：
G. Po;Yue Huang;N. Ghoniem
最近的电子背散射衍射（EBSD）实验揭示了fcc晶体中在楔形压头下形成的非均匀位错微观结构的出现，其中微米位错模式挑战了传统塑性模型的预测。为了解释这些特征的形成，并建立力-位移曲线与位错子结构之间的关系，我们提出了基于位错连续介质理论的楔形压痕模型。该模型通过变形梯度张量的乘法分裂来解释大变形运动学，其中变形的不相容塑性分量是由不同滑移系统上的位错通量和相互作用产生的。由耗散变分原理确定位错通量的本构方程。结果表明，每个位错密度都满足一个具有对流扩散特征的初边值问题，该问题与控制变形过程的宏观应力场和位移场耦合。用有限元法求解了自洽连续介质方程。计算机模拟模拟了Kysar等人（2010a）对Ni单晶进行楔形微压痕实验的实验条件。总体位错密度分布与宏观力学响应的对比表明，在位错模式和晶格旋转的详细特征以及宏观力-位移响应方面，与实验结果总体上吻合较好。
Recent Electron Backscatter Diffraction (EBSD) experiments have revealed the emergence of heterogeneous dislocation microstructures forming under a wedge indenter in fcc crystals, where micro-meter dislocation patterns challenge the predictions of traditional models of plasticity. In order to explain the formation of these features and develop a relationship between the force-displacement curve and the dislocation substructure, we present here a model of wedge indentation based on the continuum theory of dislocations. The model accounts for large deformation kinematics through the multiplicative split of the deformation gradient tensor, where the incompatible plastic component of deformation results from the flux of dislocations on different and interacting slips systems. Constitutive equations for dislocation fluxes are determined from a dissipative variational principle. As a result, each dislocation density satisfies an initial-boundary value problem with convective-diffusive character, which is coupled to the macroscopic stress and displacement fields governing the deformation process. Solution to the self-consistent continuum formulation is found using the finite element method. Computer simulations mimic the experimental conditions of wedge micro-indentation experiments into Ni single-crystals used by Kysar et al. (2010a). A comparison of overall dislocation density distribution and macroscopic mechanical response shows good overall agreement with the experimental results in terms of the detailed features of dislocation patterns and lattice rotations as well as the macroscopic force-displacement response.