喷丸残余应力对裂纹闭合效应影响的数值仿真

基于裂纹闭合效应,利用ABAQUS软件建立用于预测残余应力场中疲劳裂纹扩展特性的弹塑性有限元模型。考虑塑性和残余应力场对裂纹闭合的作用,分析残余应力、应力比和裂尖单元尺寸对裂纹闭合效应的影响。研究结果表明:未喷丸试样的裂纹闭合类型为塑性诱导裂纹闭合,喷丸残余应力场中的裂纹闭合为塑性和残余压应力共同作用,且裂纹张开力的大小与残余应力的分布相对应;正应力比越大,裂纹闭合效应越不明显,疲劳裂纹扩展速率越快;裂尖单元尺寸小于塑性区范围时可以真实反映裂尖的闭合状态;喷丸残余压应力通过提高裂纹闭合力,增强裂纹闭合效应,抑制疲劳裂纹扩展。

Numerical Simulation for Residual Stress Fields of Shot-peening on Crack Closure Effects

Based on the crack closure effects, the elasticplastic finite element model was established to predict the fatigue crack propagation characteristics of the residual stress field by ABAQUS. Considering the plasticity and the residual stress field, the influences of the residual stress, stress ratio and element size at the crack tip on the crack closure effects were studied. The results show that the crack closure without shotpeening is the plastic induced crack closure, whereas the crack closure of shotpeening is a combined effect of plasticity and residual stress, and the crack opening force corresponds to the distributions of the residual stress. With the increase of the stress ratio, the crack closure effects are slight and the fatigue crack propagation rates are accelerated. The element sizes at crack tip, which are smaller than the plastic zone, can reflect the closure state of the crack tip. The compressive residual stress of shotpeening can enhance the crack closure forces and the crack closure effects, thus, the propagation of fatigue crack is suppressed.