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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.
The effect of load ratio, unimodal overloading and two-step high-low amplitude loading on the fatigue crack growth rate of Z3CN20-09M cast austenitic stainless steel was investigated with compact tensile test specimens.When the stress intensity factors were in the same range, the fatigue crack growth rate With the increase of load ratio, the uniaxial overload causes the crack propagation rate to increase first and then the long-distance deceleration to expand, and the crack propagation hysteresis appears.When the two-step high-low amplitude is loaded, if the maximum load of two steps , The hysteresis also appears in the crack propagation in the second step.With the two-parameter model and Wheeler model, the fatigue crack growth behavior under constant amplitude and amplitude load can be predicted.