含刮痕缺陷的7050-T7451铝合金板疲劳寿命预估

Fatigue life prediction for 7050-T7451 aluminum alloy plate with scratch defect

针对含刮痕缺陷的7050-T7451铝合金板的疲劳损伤问题进行了研究,通过考虑刮擦后残余应力、塑性损伤以及疲劳载荷的共同作用,预估了含刮痕铝合金板的疲劳寿命.对刮痕的产生进行非线性动力学有限元(FE)分析,得到了刮痕处的残余应力场与塑性应变场;根据塑性损伤方程,计算了在刮擦过程中刮痕处由于塑性变形产生的初始损伤场;基于多轴疲劳的损伤力学模型,建立了疲劳损伤分析的有限元数值解法,并对损伤演化方程中的材质参数进行了标定;综合考虑残余应力场、塑性初始损伤和疲劳损伤,对含刮痕的铝合金板进行了疲劳寿命预估,并与试样的疲劳试验结果进行了比较,理论估计和试验得到了相一致的疲劳寿命结果,验证了方法的可行性.本文研究为工程中含刮痕结构的疲劳寿命预估提供了一种本文方法和实用手段.

Fatigue damage of 7050-T7451 aluminum alloy plate with scratch was studied,and the fatigue life of aluminum alloy plate after scratching was predicted considering the common effects of the residual stress,plastic damage and fatigue load. The nonlinear dynamic finite element（ FE） analysis was conducted to simulate scratch generation,and the residual stress field and plastic strain field near scratch were obtained.According to the equation of plastic damage,the initial damage field near scratch caused by plastic deformation in the scratching process was calculated. Based on the multiaxial fatigue damage model,the finite element numerical method was established to analyze fatigue damage,and the calibration of material parameters in the damage evolution equation was conducted. This method was used to predict the fatigue life of scratched aluminum alloy plates with synthetically considering the residual stress field,the initial plastic damage and fatigue damage. The predicted results were compared with results from the fatigue test of specimens,and the theoretical prediction was in accordance with the test results of fatigue life. A new method and a practical means for fatigue life prediction of metal component with scratch defect were provided.