常幅和过载下CT试件的低周疲劳裂纹扩展实验研究

摘要

Engineering structural components are often subjected to variable amplitude loads, and the applied tensile overload has a significant effect on the fatigue crack propagation.The crack propagation rate of AH32 standard compact tensile specimen under constant amplitude and tensile overload is studied by adopting the crack opening displacement as the basic parameter.The patterns of crack length and crack opening displacement with crack propagation under single tensile overload, double tension overload and others are discussed.The experimental results show that the crack open displacement can well explain the regular pattern of low cycle fatigue crack propagation.The compressive residual stress due to the overload in the crack tip and crack tail-trail region is found to be the important reason causing the retardation of crack propagation.%实际工程构件经常受到变幅载荷作用,施加的拉伸过载对构件上的疲劳裂纹的扩展有明显影响.以裂纹张开位移为基本测量参量,开展了AH32标准紧凑拉伸试样(CT试样)在常幅和拉伸过载下裂纹扩展速率的变化规律的研究.阐述了在基本循环中插入单个拉伸过载、双次拉伸过载等情况下裂纹长度及裂纹张开位移随裂纹扩展的规律.实验结果表明,裂纹张开位移能很好的诠释低周疲劳裂纹扩展规律;过载在裂尖前方和裂纹尾迹区引起的压缩残余应力是导致裂纹扩展迟滞的重要原因.