残余应力集中及其对疲劳极限和短裂纹扩展的影响

RESIDUAL STRESS CONCENTRATION AND ITS EFFECTS ON FATIGUE LIMIT AND SHORT CRACK GROWTH

缺口根部的残余应力存在应力集中效应,应力集中值不仅取决于缺口几何形状而且和材料的屈服强度有关。残余应力集中系数是一个分布值,其数值甚至可超过理论应力集中系数。软试样喷丸后缺口处的残余应力易于松弛及喷丸时的表面损伤使其对疲劳极限的贡献小。残余压应力使缺口处裂纹闭合力增大甚至可出现非扩展裂纹。

Residual stress concentration at a notch depends on both notch geometry and yield strength of the material. It varies through the depth, and its magnitude may be higher than the theoretical one. Compressive residual stress concentration at the notch of shot-peened specimen of soft material is easy to be relaxed, with the surface damage during shot-peening results in a minor contribution to the fatigue limit. Compressive residual stress increases the crack closure effect at the notch and may lead to a non-propagating crack.