缺口根部塑性区和拉应力场对循环压缩疲劳裂纹止裂长度的影响

Influence of Plastic Zone and Tensile Stress Field Ahead of The Notch on The Arrest Crack Length Under Cyclic Compressive Fatigue

本文采用激光显微像面全息和散斑照像分离技术检测了双缺口试件在不同压缩应力条件下缺口根部塑性区的形状及大小,并采用有限元分析法计算了相同应力下的塑性区和裂端应力场.结果表明:用显微像面全息法测量塑性区的大小及形状简单易行,且有比较满意的工程精度. 对在不同压缩循环加载条件下测得的瘦劳裂纹止裂长度与所测压缩塑性区相比较表明:疲劳裂纹止裂长度和塑性区大小之间不存在简单的对应关系.止裂长度主要由缺口根部在循环压缩卸载过程中所产生的拉伸应力区控制.

The shape and size of plastic zone ahead of double edge-notched specimens under different compressive load have been measured with micro-image-plane holography and speckle photography separating method(MIHSS). The plastic zone and the stress field ahead of the notch have also been calculated by finite element method. The results obtained show that the measurment is easy and accurate enough in engineering. Comparing the arresed crack length under cyclic compressive fatigue with the size of the compressive plastic zone shows that there is no simple correspondance between them and the arresed carck length is mainly controlled by the tensile stress field ahead of the notch produced during unloading in the compressive cycle.