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单一过载使得疲劳裂纹扩展速率减缓,可以提高疲劳寿命,但对于多个过载作用下疲劳裂纹扩展仍未明确,有待于进一步研究。针对Q345R标准紧凑拉伸试样,在常幅循环加载条件下引入多个拉伸过载,研究多个过载作用对疲劳裂纹扩展行为的影响。研究结果表明:在保持应力比、过载位置和过载比不变的情况下,随着过载间距增加,迟滞效应先增加后减小;过载间距循环数是单一过载迟滞循环数的一半时,da/dN_(min)达到最小,迟滞效应最明显。采用含有过载交互作用参数Φ_I的修正Wheeler模型对不同的过载间距疲劳裂纹扩展行为试验结果进行预测,预测的结果与试验结果能够很好的吻合。
Single overload makes the fatigue crack growth rate slow, can improve the fatigue life, but the fatigue crack propagation under multiple overload is still not clear, pending further study. Aiming at the Q345R standard compact tensile specimen, several tensile overloads were introduced under cyclic loads, and the effect of several overloads on the fatigue crack growth behavior was studied. The results show that the hysteresis effect first increases and then decreases with the increase of the overload distance under the condition of keeping the stress ratio, the overload position and the overload ratio. The cycle of overload interval is half of the single overload hysteresis cycle, dN_ (min) reached the minimum, hysteresis effect most obvious. The modified Wheeler model with overload interaction parameter Φ_I is used to predict the fatigue crack propagation behavior at different overload distances. The predicted results are in good agreement with the experimental results.