本文通过初始切口有较大变化范围的LY12R板材疲劳扩展试验,分析了影响形成疲劳裂纹寿命N_i的因素,得到了N_i的关系式lnN_i=a+b△K_c。对LY12R及三种钢和一种钛合金的实验数据进行了分析,分析表明,在所研究的范围内,疲劳裂纹的形状变化规律对材料、试件尺寸、载荷大小不敏感,且上述平板构件中表面裂纹的深度a均可用同一经验关系式△a=f(△c)来估计,估计值与实测值符合很好。分析还表明,直至σ_(N,max)/σ_y=0.9时,表面裂纹的扩展仍为应力强度因子幅值△K所控制。
The effect of fatigue crack initial life, N., on the shape of initial notch and stress ratio under the tensile loading for LY12R sheet specimens has been studied. A relation predicting fatigue life, in N_i=a+b△K_c has been obtained. The crack growth behavior for LY12R, three steels and a titanium alloy have also been analysed. The results show that the crack growth behavior is not sensitive for materials, dimension of specimens and loading condition so that the surface crack depth may be predicted by the empirical expresion, △a=f(△c). It was also found that the surface crack extension is controlled by. stress strength. factor when σ_(Nmax)/σ_y=0.9.
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