铸造奥氏体不锈钢的疲劳裂纹扩展

用紧凑拉伸试样研究了载荷比、单峰过载和两步高-低幅加载对Z3CN20-09M铸造奥氏体不锈钢疲劳裂纹扩展速率的影响。当应力强度因子范围相同时，疲劳裂纹扩展速率随载荷比的增大而增大。单峰过载使裂纹扩展速率先有短暂的增加后长距离的减速扩展，出现裂纹扩展迟滞现象。两步高-低幅加载时，若两步的最大载荷不同，第二步裂纹扩展也会出现迟滞现象。用两参数模型和Wheeler模型能够预测恒幅载荷和变幅载荷下的疲劳裂纹扩展行为。

Fatigue crack growth of cast austenitic stainless steels

The influences of stress ratio, single overload and high-low loading sequence on the fatigue crack growth of Z3CN20-09M cast austenitic stainless steels were studied with compact tension specimens. When the stress intensity factor range is identical, the fatigue crack growth rate increases with the increase of stress ratio. During single overload, the fatigue crack growth rate shows a short period of acceleration followed by a significant decrease, leading to subsequent crack growth retardation. Similarly, high-low loading sequence with the maximum load in the second step lower than that in the first loading step results in significant crack growth retardation in the second loading step. A two-parameter model and Wheeler’ s model are found to predict well the crack growth behav-ior under constant-amplitude loading and variable-amplitude loading, respectively.