圆形缺口裂纹扩展的晶体相场模拟

Phase Filed Crystal Simulation of Extension of Crack at Notch with Circle

关键词:  圆形缺口  发射位错  晶体相场  裂纹扩展

Key words:  notch with circle  emission dislocation  phase filed crystal  extension of crack

摘要:

[目的]研究初始缺口为圆形的样品在纵轴拉伸应力作用下起裂，并在样品裂纹扩展方向确定后，再加上横轴压力下裂纹的扩展情况。观察横轴压力对其扩展方向的影响，从而得出施加压力修复正在扩展的裂纹样品的模拟结果。[方法]使用晶体相场法（PFC）进行模拟，获得裂纹扩展的演变图。[结果]在纵轴拉应力条件下，应变在达到一定数值后圆形缺口开始发射位错和空位，位错向前运动；之后柏氏矢量相反的位错相遇并相互湮灭，没有湮灭的位错组合成位错对并产生裂纹；最后微裂纹之间、微裂纹与原始缺口之间相互合并。裂纹稳定地朝着横轴方向扩展，在此基础上施加横轴的压应力，发现左侧裂纹扩展方向发生两次改变，并往裂纹扩展方向发射位错。同时初始设置的圆形缺口也有形状变化，并往纵轴发射位错。[结论]晶体相场法能有效模拟晶体裂纹扩展的微观现象。

Abstract:

[Objective] The sample with a circular initial gap was cracked under the tensile stress of the longitudinal axis, and the crack propagation under the transverse axis pressure was added after the crack propagation direction of the sample was determined. The effect of the transverse axis pressure on its direction of expansion was observed to derive the simulation results of applying a pressure to repair the crack sample that was expanding.[Methods] Phase field crystal method (PFC) was used for simulation to obtain an evolution map of crack propagation.[Results] Under the tensile stress condition of the longitudinal axis, after the strain reaches a certain value, the circular notch starts to emit dislocations and vacancies, and the dislocations move forward. Then, the opposite dislocations of the Berth's vector meet and annihilate each other, and the dislocations without annihilation are combined into dislocation pairs and cracks are formed. Finally, the micro-cracks, micro-cracks and original gaps merge with each other. The crack spreads stably toward the horizontal axis, and the compressive stress of the transverse axis is applied on the basis of this, and it is found that the direction of the crack propagation on the left side changes twice, and dislocations are emitted in the direction of crack propagation. At the same time, the initially set circular notch also has a shape change and emits dislocations to the vertical axis.[Conclusion] The crystal phase field method can effectively simulate the microscopic phenomenon of crystal crack propagation.