一种估计结构多轴随机振动疲劳寿命的临界平面法

Critical plane method for evaluating the random vibration fatigue life of structures

为了估计结构在多轴随机振动状态下的疲劳寿命,提出了一种利用方向余弦确定危险平面,基于临界平面法的频域分析方法。该方法基于结构危险点的应力功率谱密度矩阵,将经过危险点且剪应力方差最大的平面作为结构的临界平面,然后将该平面上的正应力与剪应力进行线性组合得到等效应力功率谱密度函数,最后结合线性疲劳损伤累积理论与Tovo-Benasciutti法确定结构的寿命。对几种金属构件在多轴随机激励下的疲劳寿命进行了计算,并与实验结果进行了对比,结果表明误差在2.5倍以内,说明了该方法的可行性。

To evaluate random vibration fatigue life of structures,a new computationally-efficient frequency domain formulation of the critical plane method is proposed.The method is based on the power spectral density matrix(PSD)of the stress tensor.Then the PSD function of an equivalent normal stress is defined by considering a linear combination of the PSD functions of the normal stress and shear stress along the direction of critical plane,which is defined by maximizing the variance of shear stress.Such an equivalent PSD function allows us to apply the Tovo-Benasciutti method to estimate the fatigue life of structure.Moreover the estimated fatigue life prediction was compared with the test result,and the deviation is within 2.5 times,then the feasibility of the method is illustrated.