【摘要】 本文利用断裂力学、疲劳及可靠性分析方法,讨论了剩余强度的概率分布。假定裂纹萌生阶段已结束,在裂纹扩展阶段,剩余强度R与裂纹长度α满足R=αK_ca^-1/2,裂纹扩展速率可用Paris公式da/dN=c（△K）ⁿ描述,在以上两个公式的基础上,我们推导出了疲劳载荷过程中剩余强度、循环应力、疲劳寿命及失效概率间的关系。 选用变速箱齿轮12Cr2Ni4钢制成的试样,我们在Amsler HFP5100高频疲劳试验机上,两级循环应力水平下进行了9组试验,得出了12Cr2Ni4钢的P-R-S-N曲线。利用该曲线估算了12Cr2Ni4钢多级载荷下的疲劳寿命,同Mine准则计算的结果相比更接近真实值,本文的方法具有较强的工程实用性,对承受疲劳载荷零构件的选材及设计具有重要的参考价值。更多还原

【Abstract】 The reliability of fatigue problems were discussed on the basis of fracture mechanics,fatigue and reliability analysis. The stage of crack initiation to the finish was assumed. In the stage of crack growth,the residual strength R and crack length a have the relation: R =aKca-1/2 . The crack growth rate of material can be described by Paris formula:da/dA= c(ΔK)n. On the basis of these two formulas, the relationsof failure probability,residual strength,fatigue stress and lifetime in cycle were obtained.Specimens made of wear material, 12Cr2Ni4 steel, were used to prepare nine series of experiments. The experiments were conducted on Amsler HFP5100 Fatigue testing machine under two stress levels. By means of these experiments, the P-R-S-N curves of 12Cr2Ni4 steel have been obtained. By the curve, the reliable fatigue life under multistage load is estimated. This results conclude that the calculation of this method is more approach to the true value than that of Mine criteria. The analytical method is valuable reference to other machine component.更多还原