结构声疲劳寿命估算的功率谱密度法

THE POWER SPECTRAL DENSITY METHOD FOR THE ESTIMATION OF THE SONIC FATIGUE LIFE

通过对现行传统声疲劳分析方法的回顾，以及对声疲劳学科所涉及的理论领域的深入研究，提出了进行声疲劳分析的功率谱密度法。它能够解决或部分解决传统声疲劳分析存在的问题，能够考虑多模态复杂结构的噪声响应，完成让许多科技工作者感到困扰的频域到时域的转换。同时，疲劳寿命计算中常规Ｓ—Ｎ曲线的应用将有助于改善随机疲劳试验曲线缺乏和等效随机疲劳曲线应用限制条件多的现状。算例结果表明，功率谱密度法作为一种声疲劳分析方法不但可行，而且限制条件更少、计算结果更好。

There are two main apparent shortcomings in traditional analysis methods for sonic fatigue problems. One of them is that the response analysis of isolated plate is based on its few natural modes,the other is theneed of a large amount of random S-N curves used in fatigue estimation. The purpose of the PSD method proposed in this paper is to overcome or partly overcome the shortcomings above. Based on the random vibration theory for linear system with multiple degree of freedom and the Finite Element Method,the wide band response ofcomplex airplane structures under acoustic load can be worked out. Then,based on the theory of Monte Carlo simulation on stationary ergodic process and its application,the frequency power spectrum of structure response can beconverted to time domain histories. Under the consideration of large deflection caused by high density noise and bythe usage of both rainflow cycle counting method and conventional S-N curves,the fatigue life of the structurecan be estimated.The analytical results by PSD method agree well with those of experiment. It shows that the PSD method isnot only available,but a way with less limitation and better results as well in sonic fatigue analysis.