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研究了不同方式超载,包括拉伸、压缩、拉伸-压缩和压缩-拉伸超载,对LY12铝合金疲劳裂纹扩展过程的影响。通过对不同超载前后裂纹尖端显微形貌及其附近塑性区尺寸与应变分布变化的研究和断口分析,指出:不同方式超载对裂纹扩展过程产生迥然不同的影响;拉伸超载引起的裂纹扩展速率递减延缓过程,是以闭合应力和残余压缩应力为主的多因素复合作用在裂纹尖端及其附近区域的结果。提出了拉伸超载对疲劳裂纹扩展过程影响的一般机制。
The effects of different modes of overloading, including tensile, compressive, tensile-compressive and compressive-tensile overload on the fatigue crack growth of LY12 aluminum alloy were studied. Through the study of the microstructure of the crack tip before and after different overloads and the change of the size and strain distribution of the plastic zone around it and the fracture analysis, it is pointed out that different modes of overloading have different effects on the crack propagation. The crack propagation rate The process of decreasing and delaying is the result of the multi-factor compound action of the closing stress and the residual compressive stress on the crack tip and its vicinity. The general mechanism of the influence of tensile overload on fatigue crack propagation is proposed.