某机翼结构细节抗疲劳优化设计

针对某型飞机在使用过程中中外翼下壁板产生的裂纹故障，根据故障产生的原因，运用优化设计方法，建立以该部位疲劳寿命和结构增加重量为优化目标的数学模型；改进机翼下壁板故障部位的结构设计；对比分析优化前后结构的寿命。使该部位结构的改进设计在重量增加较少的条件下，疲劳寿命较长，满足飞机的实际使用。

OPTIMUM DESIGN FOR THE WING-SKIN PANEL UNDER CYCLIC LOADING

A crack occurred in the wing skin panel during the service of a kind of aircraft. When the failure was detected, a crack is 70?mm long in one aircraft and 180?mm long in the other. Both of the cracks occurred at the same spot and had the same characteristics. The causes of the failure were analyzed. To improve its fatigue strength, a two target optimum model was set up on the basis of fatigue life and additive weight of the structure. A curve about the relationship between stress and design variables is fitted using finite element method (FEM). By assigning different weights to the target functions, the multi target optimum model was simplified to a single target one. Because this function is implicative, an initial value of strain was given. The model was solved using sequential unconstrained minimization technique (SUMT), which is based on the Powell's method. Then the value of strain was replaced and solved until the value was satisfied. A good design is worked out for improving the fatigue strength of the failure part. The improved structure will have longer fatigue life and less weight comparing to the original. This kind of design method can provide guidance in practical design.