不同晶向取向的裂纹扩展演化模拟

Simulation Study of Crack Propagation and Evolution in Different Crystal Orientations

关键词:  微裂纹  晶向取向  位错发射  晶体相场

Key words:  micro cracks  crystal orientation  dislocation emission  phase-field-crystal

摘要:

[目的]研究具有不同初始晶向倾角的样品在单轴拉应变作用下的纳观尺度裂纹扩展行为,了解裂纹的生长特征和扩展规律,揭示纳米级裂纹扩展机理及其对材料断裂的影响。[方法]采用晶体相场法观察不同晶向倾角下裂纹的扩展演化图及对应的应力分布图。[结果]当拉应变作用达到临界值时,无预应变的样品裂口开始起裂,并伴随着位错出现。在晶向倾角为0°、5°时,裂口在起裂时,缺口两端裂纹和裂口相连接,裂纹主要是解理脆性断裂模式扩展;在晶向倾角为10°时,裂口向左右两边各发射一个位错,位错在滑移过程中留下一系列空位,空位连通形成裂纹再与主裂口相连,裂纹主要是韧性断裂模式扩展。[结论]不同晶向取向对裂纹的扩展演化有重要影响。

Abstract:

[Objective] The samples with different initial crystal orientations and the crack propagation behavior of nano scale under uniaxial tensile strain are studied,to understand the growth characteristics and propagation law of crack,and to reveal the mechanism of nano scale crack propagation and its effect on material fracture.[Methods] The crack propagation evolution and the corresponding stress distribution of different crystal orientations are observed by means of the phase-field-crystal method.[Results] The tensile strain is applied onto the samples without pre-deformation,and the crack begins to propagation with dislocations when the strain reaches the critical value.For the sample with crystal orientation at 0° and 5°,the crack begins to propagation and connects to the notch,and the crack propagation is of cleavage brittle fracture mode;For the sample with crystal orientation at 10°,a dislocation is emitted from the left and right sides of the crack,and the dislocation in the process of slipping leaves a series of vacancies,which grow up and form cracks,and then connect to the main crack.The crack is of ductile fracture mode propagation.[Conclusion] Different crystal orientation has an important influence on the crack propagation and evolution.