中文摘要：

将材料疲劳寿命的对数正态分布参数引入Miner疲劳损伤累积理论,推导出两级阶梯谱下的疲劳损伤概率密度函数;进而给出累积损伤分散带。使用航空工业常用的LY12CZ铝合金,进行一系列多轴两级阶梯谱试验。依据补充的和文献已有的试验,使用本文方法计算考虑材料分散性后不同阶梯谱下的损伤分散带。通过对比损伤分散带和Miner理论计算值,考察不同类型多轴阶梯谱下Miner理论的适用性。分析结果表明,对于恒路径变幅谱和变路径常幅谱,由于前后级载荷的幅值较为接近,Miner理论的适用性与载荷非比例度的变化情况有关,载荷非比例度变化越大,Miner理论的适用性越好;对于变路径变幅谱,由于幅值差别较大,载荷变化对损伤累积的影响大于材料分散性带来的不确定性,Miner理论不适用。

英文摘要：

Based on Miner＇s law and probability theory, the probability density function of damage sum under the 2-stage step loading spectrum is proposed, by taking the logarithm normal distribution of the fatigue life into account. The method to determine the scatter of the accumulative fatigue damage is further proposed. A series of experiments under multiaxial 2-stage step loading spectra are conducted on LY12CZ aluminum alloy, which is commonly used in aviation industry. Combined with the test results of the paper and the references, the applicability of Miner＇s law is investigated under multiaxial 2-stage step loading spectra, after considering the material dispersion. The result shows that, for the constant path variable amplitude spectra and variable path constant amplitude spectra, since the amplitudes of the two stages are similiar, the applicability of Miner＇s law is affected by the variation of the non-proportionality of the multiaxial loadings. Larger non-proportionality leads to better applicability. For the variable path variable amplitude spectra, since the amplitudes of the two stages are significantly different, Miner＇s law is not applicable.