涡轮盘低循环疲劳寿命的概率分析

疲劳寿命呈现异方差特性,其标准差随弹性应变幅和塑性应变幅的减小而增大,因此在Man-son-Coffin公式中引入标准正态变量μ和线性标准差σ_e,σ_p,将ε-N曲线参数表示为标准正态变量μ的函数,建立了低循环疲劳寿命的概率模型.针对某涡轮盘材料,在低循环疲劳试验数据的基础上应用异方差回归分析方法获得了概率模型的参数,应用该模型对涡轮盘销钉孔的低循环疲劳寿命进行了Monte-Carlo数值模拟,获到了寿命的概率分布.得到可靠度0.998 7的概率寿命与轮盘技术寿命相一致,相对误差仅为4%.该模型参数均来自疲劳试验数据的统计分析,寿命预测精度高,具有较好的工程应用前景. 

Probability analysis for the low cycle fatigue life of a turbine disk

The standard deviation of fatigue life increases with reduction of elasticity and plasticity strain components.A standard normal random variable μ and linear standard deviations σ_e and σ_p were introduced into Manson-Coffin equation,so the probabilistic model of fatigue life was established,in which four parameters were expressed as the functions of μ.The parameters of the probabilistic model were obtained by the heteroscedastic regression analysis method based on the low cycle fatigue(LCF) test data,the fatigue life probability analysis for the pinhole of a disk was achieved by this model,and the distribution of the fatigue life of the pinhole was obtained.The results show that the life with the reliability of 0.9987 is well consistent with the technical life of the disk based on test evaluation.This model is suitable for engineering application with its good precision.