非高斯随机应力载荷频域疲劳寿命估计方法

SPECTRAL FATIGUIE LIFE ESTIMATE UNDER NON-GAUSSIAN RANDOM STRESS

对于工程中大量存在的非高斯随机应力载荷的疲劳寿命估计问题,传统频域疲劳方法由于基于高斯性假设, 故仅能采用高斯分布近似或经验性修正来简化处理,缺乏理论基础且存在较大误差。基于随机应力载荷的频域疲劳基本理论,利用非高斯概率密度函数的Hermite多项式渐近展开,利用其三维联合高阶统计特征,推导得到了非高斯随机应力载荷下疲劳寿命估计公式,并针对高斯、亚高斯和超高斯随机应力载荷进行了验证。该方法普遍适用于窄带、宽带、高斯和非高斯应力载荷作用下的疲劳寿命估计问题,具有重要的理论意义和工程价值。

Non-Gaussian random stresses exist in engineering stuctures widely, but the former spectral fatigue life estimate methods cannot be efficiently applied to this kind of stresses due to basing on Gaussian assumption. Based on spectral fatigue life estimate theory and Hermite polynomial extension of non-Gaussian Possibility density function and three dimensions high order statistic, a new method is theoretically deduced to estimate fatigue life under non-Gaussian random stresses, and is demonstrated with numerical examples under Gaussian stress, sub-Gaussian stress and super-Gaussian random stresses. The method is applicable to fatigue estimate under stresses whether it is Gaussian or non-Gaussian, and whether its spectral bandwidth is narrow or wide.