基于雨流计数变程的疲劳可靠性仿真研究

为评估单个构件在随机载荷作用下的疲劳可靠性,基于应力时间历程的雨流计数变程利用应力-强度干涉理论和Dirlik雨流计数变程的概率密度表达式,假设疲劳极限服从正态分布,得出结构具有无限寿命的可靠度.利用Miner损伤累积理论,假设疲劳寿命服从对数正态分布,考虑Dirlik表达式的参数和损伤累积临界失效值的分散性,假设其服从正态分布,使用Monte-Carlo模拟法获得结构有限寿命下的可靠度.结果显示,虽然应力时间历程的最大范围值大于结构的疲劳极限,但是当其大部分应力小于疲劳极限时,结构仍具有较高的无限寿命可靠度;而有限寿命下的可靠度显示,尽管单个应力时间历程下结构具有较高的无限寿命可靠度,但是经过多次循环后其不发生疲劳失效的可靠度将逐渐降低.

Research on fatigue reliability based on rainflow cycle range

In order to evaluate fatigue reliability of single structure under random load,based on stress range in stress-time history by rainflow counting,infinite life reliability of structure is obtained by means of stress-strength interference theory and Dirlik＇s probability density function of rainflow counting stress range and by assuming that fatigue limit accord with normal distribution. Also by using Miner＇s damage accumulation theory,assuming that fatigue life accord with lognormal distribution,and taking into account dispersion of Dirlik＇s function parameter and critical failure value of damage accumulation,finite life reliability of structure is obtained by means of Monte-Carlo simulation method. The results show that when a majority of stress in stress-time history is less than fatigue limit,structure has high infinite life reliability although maximum range in stress-time history is greater than fatigue limit. The results of finite life reliability indicate that although structure has high infinite life reliability under single stress-time history,reliability of structure experiencing many cycle gradually decrease.