三角缺口与圆形缺口起裂和裂纹扩展的晶体相场模拟

Phase Filed Crystal Simulation of Nucleation and Extension of Crack at Notch with Circle or Triangle

关键词:  缺口  发射位错  晶体相场

Key words:  notch  emission dislocation  phase field crystal

摘要:

[目的]研究具有不同初始缺口的样品在单轴拉伸应变作用下裂纹起裂扩展的方式。[方法]采用晶体相场(PFC)法模拟不同缺口裂纹的扩展演化图及相应的应力分布。[结果]三角形裂口两侧裂纹起裂与扩展情况存在明显的差异,左侧裂口出现韧和脆两种类型的裂纹生长,而右侧的缺口是解理裂纹扩展;圆形裂口两侧的裂纹萌生,开始时表现为发射位错,然后形成空洞,随着裂纹进一步发展,逐渐转变为解理扩展。在应变施加初期,应变场强较弱,只在裂口附近有变化,形成二个环状的分布,在萌生裂纹的区域,出现应变集中。随着裂纹扩展,应变场环绕在裂纹周围,形成大的椭圆环状,在裂尖附近和位错区域,都存在应变集中。[结论]不同初始缺口对缺口起裂的时刻、方式和裂纹扩展有影响。

Abstract:

[Objective] The purpose of this study is to study the crack propagation pattern of samples with different initial notches under uniaxial tensile strain.[Methods] The phase field crystal method was used to simulate the evolution of different notched cracks and the corresponding stress distribution.[Results] There were obvious differences in crack initiation and expansion on both sides of the triangular crack, and there were two types of cracks in the left fracture,while the gap on the right was cleavage crack propagation. The initiation of cracks occurred on both sides of the circular crack,along with the emission dislocation and then formed voids. With the further development of the crack,it gradually transformed into cleavage expansion. In the early stage of strain application, the strain field strength was weak, only changed in the vicinity of the gap. The formation of two annular distributions in the initiation of the crack area, there was strain concentration. As the crack propagated, the strain field surrounded the crack and formed a large elliptical ring, there was strain concentration near the crack tip and in the dislocation region.[Conclusion] Different initial notches had an effect on the time and mode of crack nucleation and crack propagation.