铝合金缺口件载荷谱小载荷删除与试验验证

摘要

The small load omitting approach is a branch of accelerated fatigue test technology.The existing methods hardly ever consider the randomness of the fatigue property of the structure.In this paper, the fatigue life is regarded as a continuous random variable,and the difference of fatigue life distribution before and after small-load-omitting is quantitatively described by probabilistic distance.The standard, in which the distribution of the fatigue life of the omitted spectra is the same with that of the original spectra,is used.The dispersion of fatigue property of structure is considered in this approach.According to the distribution density function of stress amplitude and the p-S-N curves of the component,the omission level can be calculated.Fatigue tests with notched specimens made of LC4CS aluminum alloy are conducted to verify this approach.Five different spectra are obtained by removing small cycles of which amplitudes are less than the specified omission level,and the number of load cycles is about 8.4％of the original spectra.It is found that experimental results agree well with theoretical solutions.%小载荷删除方法是加速疲劳试验技术中的一种,现有的删除方法往往忽略了结构疲劳性能的随机性.本文将疲劳寿命看作连续的随机变量,采用概率距离定量描述小载荷删除前后疲劳寿命分布的差异程度,以删除谱与原始谱的疲劳寿命同分布为标准作为小载荷删除的方法.该方法考虑了结构疲劳性能的分散性,可根据结构的p-S-N曲线和载荷谱的应力分布函数计算相应的小载荷删除水平.对LC4CS铝合金缺口件在5种载荷谱下进行疲劳试验,结果表明,计算得到的删除谱与原始谱的疲劳寿命同分布,载荷循环数为原始谱的8.4％,节省了试验时间.