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本文给出了两种考虑缺口尺寸效应的疲劳裂纹形成寿命的预测方法。一种是用高应变区体积考虑尺寸效应,通过缺口的△W-N;数据建立起经验公式。另一种是用疲劳缺口系数K_f代替理论应力集中系数K_8以考虑尺寸效应,通过用K_1修正后的△代替△J得到寿命预测公式。两种方法前者精度较高,后者更为简便。 文章还给出了一种用断裂力学确定疲劳缺口系数K_1值的方法。并指出用缺口循环J积分预测疲劳裂纹形成寿命比用Neuber公式计算缺口最大形变功密度范围来预测疲劳裂纹形成寿命更接近实验结果。
In this paper, two prediction methods of fatigue crack formation life considering the notch size effect are given. One is to consider the size effect with the volume of the high strain zone and establish the empirical formula through the notch △ W-N; The other is to use the fatigue notch coefficient K_f instead of the theoretical stress concentration factor K_8 to consider the size effect. The life prediction formula can be obtained by replacing the △ J with the △ after K_1 correction. The former two methods have higher precision and the latter is more convenient. The article also gives a method to determine the fatigue gap coefficient K_1 by fracture mechanics. It is pointed out that the prediction of the fatigue crack initiation life is more similar to the experimental result by using notch integral J integral to predict fatigue crack growth life than calculating the maximum deformation work gap density by Neuber’s formula.