随机疲劳可靠度预测的状态分析方法研究

State Analysis Approach of Random Fatigue Reliability Prediction

两级载荷下的疲劳剩余寿命试验结果显示,在没有疲劳失效的情况下,若先施加低应力,则在后续的高应力下剩余寿命的标准差与该高应力下原始寿命的标准差相比变大;若先施加高应力,则在后续的低应力下剩余寿命的标准差与该低应力下原始寿命的标准差相比变小。根据两级循环载荷作用下剩余疲劳寿命分布规律的实验规律,以描述剩余寿命分布变化的数学模型为基础,提出了一个根据载荷历程作用下结构/零件状态变化预测随机载荷下疲劳可靠度的方法。使用该方法,可以根据已知的材料或零件的原始P S N曲线,借助剩余寿命分布和载荷循环数—疲劳寿命干涉分析计算随机载荷作用下的疲劳可靠度。

Firstly, the residual fatigue life distribution is experimentally studied under two-level cyclic loading. It is shown that, in the situation of no fatigue failure, the residual life standard deviation under the high-level load becomes larger after low-level cyclic load acting, or vice versa. According to the two-level cyclic stress experiment result, equations are developed to simulate the residual fatigue life distribution parameters. Then, an approach is developed to calculate the fatigue reliability under random loading by means of damage state analysis. With such an approach, the fatigue reliability under random loading can be calculated as long as the original P-S-N curve of the material (or part) is available.