随机变幅加载下疲劳强度可靠性分析

Reliability Analysis of Fatigue Strength under Random Variable Amplitude Cyclic Loading

目前的疲劳强度及其概率分布是根据等幅Ｐ－Ｓ－Ｎ曲线族求得的，只能用于等幅加载，不能用于变幅及随机加载．而等效应力法又是根据常规ＭＩＮＥＲ准则进行转换的，无法用于可靠性分析．本文首次明确提出等幅疲劳强度、变幅疲劳强度及随机加载疲劳强度的概念，并且运用二维概率ＭＩＮＥＲ法则，通过建立变幅及随机加载的Ｐ－Ｓａ－Ｓｍ－Ｎｖ曲面族方程，提出了变幅及随机加载下疲劳强度可靠性分析的一套系统方法，具有重要的工程应用价值．

Fatigue strength and its probability function have been establised only from the constant amplitude P-S-N curve families, and therefore cannot be used in conditions of random or variable amplitude cyclic loading. The equivient stress is caculated with the conventional MINER' S rule, and therefore cannot be used in reliabity analysis, either. In this paper, the concepts of constant amplitude fatigue strength, variable amplitude fatigue strength and random cyclic loading fatigue strength are proposed for the first time. Using Two-di mensional Probabilstic MINER' S Rule (TPMINER), random variable amplitude P-Sa-Sm--Nv surface families are established, and a systematic method for reliability analysis of fatigue strength under random or variable amplitude cyclic loading is presented, which is of importance in engineering application..