随机应力谱下构件疲劳可靠性分析的Miner准则—寿命分布函数法

MINER'S RULE-LIFE DISTRIBUTION FUNCTION METHOD FOR FATIGUE RELIABILITY ANALYSIS OF COMPONENT UNDER RANDOM STRESSES SPECTRUM

基于随机应力谱下的Miner准则和寿命分布函数 ,提出了一种随机应力谱下构件疲劳可靠性分析模型———Miner准则—寿命分布模型。该模型首先考虑构件疲劳强度影响系数 ,对材料的p—S—N曲线进行修正 ,以得到构件的p—S—N曲线 ;然后利用Miner准则导出构件在随机应力谱下的疲劳可靠寿命表达式 ,由疲劳寿命的概率分布函数 ,并考虑构件疲劳强度影响系数的随机性 。

Three random factors are involved in the fatigue reliability analysis of components under random stresses spectrum, they are the randomicity of fatigue stresses of component, the randomicity of the fatigue characteristics of material and the randomicity of fatigue strength effect factors of component. In this paper,a new method of the fatigue reliability analysis of components under random stresses spectrum was presented based on probability Miner's rule and the p-S-N curves of material, considering the randomicity of the three random factors of component. Firstly, introducing probability meaning in conventional Miner'rule obtained expression of probability Miner's rule under random stresses spectrum, and the p-S-N curve equation of components was also obtained on the basis of the p-S-N curve equation of material and the fatigue strength effective factors of components (e.g. effective stress concentrate coefficient K f, measurement coefficient ε and surface machining coefficient β etc.). Then, the expression of components fatigue reliability life under the random stresses spectrum was obtained according to probability Miner's rule and the p-S-N curve equation of components. Finally, the fatigue life distribution function (failing probability) was obtained based on the hypothesis distribution (log-normal distribution or Weibull distribution) of fatigue life and the probability distribution of the fatigue strength effective coefficients of components. So, the fatigue reliability of components under random stresses spectrum can be calculated from the fatigue life distribution function (failing probability).