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为构建三维应力状态复材结构疲劳寿命模型,提出由刚性元和弹簧元来模拟层间作用,结合二维板元构建三维有限元模型。借助典型应力比下的疲劳试验结果和损伤模型,结合等寿命曲线转化理论,发展一种任意应力比下的疲劳寿命分析方法。引入复合累积损伤建立多轴循环应力下的疲劳寿命模型。借助应力分析、静强度和疲劳累积损伤失效分析及材料性能退化模型,模拟面内和层间损伤产生、发展直至整体破坏过程,得到疲劳寿命。通过层合板疲劳寿命预测值和试验结果对比,验证所建模型的正确性。考虑设计变量空间复杂性,采用二级优化方法:系统级布局优化和子系统级尺寸优化。采用自适应遗传算法,以质量最小为目标函数,以疲劳寿命要求为约束条件,对复材舱体进行优化。建立基于多轴应力疲劳寿命的复材结构优化框架,为复材结构优化设计提供参考。
In order to construct the fatigue life model of three-dimensional stress state composite structure, a rigid element and a spring element are proposed to simulate the interaction between layers and a three-dimensional finite element model is constructed by combining the two-dimensional plate element. Based on the fatigue test results and damage models under typical stress ratio, the fatigue life analysis method under arbitrary stress ratio is developed based on the theory of isokinetic curve transformation. The composite fatigue damage is introduced to establish the fatigue life model under multi-axial cyclic stress. With the help of stress analysis, static strength and fatigue cumulative damage failure analysis and material property degradation model, the in-plane and inter-layer damage are simulated and developed until the whole failure process and the fatigue life is obtained. The correctness of the built model was verified by comparing the prediction results of the fatigue life of the laminate and the test results. Considering the space complexity of design variables, two-level optimization methods are adopted: system-level layout optimization and subsystem-level size optimization. Using adaptive genetic algorithm to minimize the mass as the objective function, fatigue life requirements as a constraint, the complex material capsule optimization. The optimization framework of the complex structure based on the multi-axial stress fatigue life is established, which provides a reference for the optimization design of the complex structure.