加筋板在复杂载荷下的振动疲劳寿命分析

目的研究航空工程结构部件——加筋板在准静态载荷和随机动载荷联合加载下的振动疲劳寿命预估问题。方法针对某铣制铝合金缺口加筋板,建立有限元模型,并采用时域法进行静动联合加载下的疲劳寿命分析。首先将准静态载荷分解为静力与正弦激励,以静力结果作为平均应力修正S-N曲线,再采用随机响应分析计算动载荷单独作用下结构危险点的应力PSD函数,通过逆傅里叶变换法,提取随机加载过程中的时域信号后,应用Von Mises等效准则,将其与正弦激励时域样本进行叠加,得到疲劳分析应力谱,再结合Miner线性累积理论和雨流循环计数法,计算得加筋板结构静动联合加载下的疲劳寿命。结果通过有限元仿真分析计算,得到加筋板在静动载荷共同作用下的疲劳寿命,对比试验寿命,误差基本在两倍界以内。结论由仿真与试验的结果对比说明,该方法可以有效预估试验件在静动载荷联合加载下的疲劳寿命,并能进一步推广到类似载荷下的疲劳寿命预估问题。

Vibration Fatigue Life Analysis of Stiffened Plates under Complex Loads

This paper aims to study the vibration fatigue life prediction of aeronautical engineering structural component-stiffened plate under the combined loading of quasi-static load and random dynamic load. A finite element model is established for a milled aluminum alloy notched reinforced plate, and the fatigue life analysis under combined static and dynamic loading is carried out by using the time domain method. Firstly, the quasi-static load is decomposed into static force and sinusoidal excitation, and the static force result is used as the average stress to correct the S-N curve, and then the random response analysis is used to calculate the stress PSD function of the dangerous point of the structure under the action of dynamic load alone. After the time domain signal in the random loading process is extracted by the inverse Fourier transform method, the Von Mises equivalent criterion is applied to superimpose it with the sinusoidal excitation time domain sample to obtain the fatigue analysis stress spectrum. Combined with Miner''s linear accumulation theory and the rain flow cycle counting method, the fatigue life of stiffened plate structure under combined static and dynamic loading is calculated. Through finite element simulation analysis and calculation, the vibration fatigue life of the stiffened plate under the combined action of static and dynamic loads is obtained, and the life error of the comparative test is basically within twice the bounds. The comparison between the calculation and the experimental results shows that the method can effectively predict the fatigue life of the test specimen under the combined static and dynamic load, and can be further extended to the fatigue life prediction problem under similar loads.