常幅载荷下结构元件断裂可靠度估算的应力强度因子模型

Analytic model based on stress intensity factor for estimating the reliability of structural components under constant amplitude loading

给出了一个估算结构元件疲劳可靠度的应力强度因子模型,系统阐述了元件在常幅载荷下疲劳可靠性的分析方法。该模型研究了常幅载荷作用下材料瞬时裂纹长度和应力强度因子的分布形式,建立了应力强度因子与断裂韧性之间的干涉关系。对7075-T7351铝合金中心裂纹试件试验数据分析的结果表明:裂纹的瞬时扩展长度和可靠度的预测结果均与试验结果符合很好,本文给出的基于应力强度因子的可靠性分析模型是合理的。

This paper presents a reliability model of structural components under constant amplitude, which is based on the distribution of stress intensity factor （SIF）. Considering the stochastic nature of the environmental influences and the geometrical and mechanical properties of structural materials, the fracture toughness and the instantaneous length of fatigue crack are random variables and assumed to follow logarithmic normal distribution approximately. Consequently, this paper deduces that the SIF of components under constant amplitude loading also follows logarithmic normal distribution and the distribution parameters can be obtained from the expectation and variance of fatigue crack length. We give the steps of parameter computation of the Paris-Erdogan＇s crack propagation equation, and based on that, present methods for calculating the expectation and variance of the crack length at a given time. Then, a SIF-based reliability model is set up and the experimental data of the center crack testpieces of 7075-T7351 aluminum alloy are employed to demonstrate it. The results show that this model is in a good agreement with the experimental results.