纳米级缺口起裂临界条件的晶体相场模拟

【目的】研究初始缺口大小对裂纹起裂的影响。【方法】采用晶体相场(phase-field-crystal,PFC)模型研究单轴拉伸应力作用下,材料裂纹起裂的动态演化过程,并结合自由能分析裂纹起裂与扩展过程中,不同缺口尺寸对裂纹起裂的影响。【结果】沿x方向施加恒应变,初始缺口y方向尺寸较小时,改变缺口x方向尺寸,缺口并不起裂;当y方向尺寸达到一定值时,初始缺口会起裂。当y方向尺寸接近起裂临界值时,x方向尺寸的增大会延缓缺口的起裂。当x方向尺寸改变量较小时,裂纹并不起裂,当增大到x方向尺寸临界值时,缺口开始起裂并扩展。【结论】在应力大小一定的情况下,缺口起裂与应力作用方向垂直的缺口尺寸密切相关,只有与应变作用方向垂直的尺寸达到临界值,缺口才会发生起裂。

Phase-field-crystal Simulation of Critical Conditions for the Crack Initiation of Nanoscale Notch

Objective]To study the effect of initial crack size on crack initiation.Methods]The dynamic of process crack propagation under the uni-axial tension deformation in single crystals is simulated by the phase-field-crystal (PFC)model.The free energy is used to analyze the in-fluence of different initial crack size on the crack initiation in the process of crack initiation and crack propagation.Results]When the initial crack of y direction size is smaller,there is no initi-ation of crack under the uniaxial tension in the x axis,although the notch size in x direction changes.when the y direction size reaches a certain value,the initial cracks will expand.The time of crack initiation is delayed with the increase of x direction size.When the initial crack of x direction size changes less,there is no initiation of crack,and the initial cracks will expand when the x direction size reaches a certain value.Conclusion]The initiation of crack is closely related to the crack size of vertical stress direction.The crack extension occurs,if only the size of notch reaches a certain value.