轨道车辆非平稳振动载荷等效谱组构造方法研究

Generation Method for Equivalent Spectrum Group of Non-stationary Vibration Load of Railway Vehicles

基于频域法的轨道车辆非平稳振动载荷下结构件疲劳分析,通常是从功率角度构造一个与非平稳振动载荷等效的功率谱密度(PSD)作为输入,但单个PSD无法表征其峭度信息,导致分析结果与实际存在较大误差。为此,提出构造一组PSD(等效谱组)等效于非平稳振动载荷方法。推导出非平稳振动载荷统计量的频域分布表达式;构造以功率与峭度的频域分布特性为约束条件的方程组,其最优解即为等效谱组;对比分析轨道车辆实测非平稳振动载荷与其等效谱组的差异。结果表明:非平稳振动载荷与其等效谱组的功率、峭度、频域分布特性以及概率密度函数中高幅值区域处具有较好一致性,同时两者具有等损伤能力;当等效谱组中PSD个数不少于8时,提出方法可以有效地适用于轨道车辆不同类型非平稳振动载荷。

For the fatigue analysis of railway vehicle structure subjected to non-stationary vibration load with the frequency domain method,an equivalent power spectral density(PSD)is generally constructed,which is regarded as the excitation.However,a PSD alone cannot represent the kurtosis of the non-stationary vibration load,resulting in a large error between the analysis results and reality.To this end,a method of constructing a set of PSDs(equivalent spectrum group)equivalent to non-stationary vibration load was proposed.First,the expression of the frequency domain distribution for statistics of non-stationary load was derived.Then,a system of equations was constructed with characteristics in the frequency domain of power and kurtosis as constraints,and with its optimal solution as the equivalent spectrum group.Finally,the differences between the measured non-stationary vibration load and its equivalent spectrum group were analyzed.The results show that the average power,kurtosis,frequency domain distribution characteristics and the high amplitude region in the probability density function of the non-stationary vibration load were consistent with those of the equivalent spectrum group.Meanwhile,both have equivalent damage potential.In the case of the number of PSDs in the equivalent spectrum group being not less than 8,the proposed method can be effectively applied to different types of non-stationary vibration loads of railway vehicles.