基于傅里叶变换及损伤力学方法的随机载荷谱处理

A Random Load Spectrum Processing Based on Fourier Transform and Damage Mechanics Method

摘要: 本文首先利用离散傅里叶变换方法将随机载荷谱从时域转换到频域；进而结合信号频谱和功率谱的分布特点确定截止频率，将高频小幅值的信号截去；将滤波后的频域信号通过傅里叶反变换转换回时域，再根据损伤力学等损伤原则进行载荷谱的规范化处理，得到用于结构疲劳分析的规范化载荷谱。本文将载荷信号的频谱与功率谱对比参照，选取适当的截止频率，有效的防止了过度滤波，为滤波的截止频率选取提供了有效实用的工程方法；本文以损伤力学为基础，实现了随机载荷谱的规范化编制，并能保留原有载荷作用顺序，为提高结构在随机载荷作用下疲劳寿命预估的可靠性奠定了基础。

Abstract: Firstly, the random load spectrum is transformed from the time domain to the frequency domain by using the method of discrete Fourier transform. Secondly, according to the scattered characteristic of the frequency domain signal, the high frequency signals with small amplitudes are wiped off as the ineffective loadings. Further, the remaining frequency domain signals are converted back into the time domain by using inverse Fourier transform, obtaining the filtered load spectrum. Thirdly, based on the damage mechanics method, the principle of equivalent damage is adopted to standardize the load spectrum, and get a normalized load spectrum for the structural fatigue analysis. The determination of the cut-off frequency and the corresponding filtering effects are also discussed. The method proposed in this paper can be effectively used for normalizing the random load spectrum with retaining the original loading sequence, which provides an improved tool for the fatigue life prediction of structures under random loads.