基于数值模拟的孔构件挤压强化疲劳寿命预测

Prediction of Fatigue Life of Hole Components Cold Expansion Strengthening Based on Numerical Simulation

为研究飞机机身7050铝合金孔构件挤压强化后的疲劳增益,采用数值模拟与试验研究相结合的方法,对孔构件的挤压强化过程、疲劳加载过程、疲劳裂纹萌生和裂纹扩展过程进行研究。通过数值模拟探究了孔构件在不同状态下危险截面的应力分布和对应的疲劳行为,分析了残余应力场对疲劳性能的影响,探讨了残余应力与疲劳裂纹萌生和裂纹扩展的内在联系,建立了孔构件挤压强化疲劳寿命数值预测模型。结果表明:孔挤压强化引入的残余压应力可以减小孔构件在受载时孔壁最大拉应力,改变疲劳裂纹的萌生位置,抑制疲劳裂纹萌生和裂纹扩展,提高7050铝合金孔构件疲劳寿命近2倍,疲劳寿命数值预测模型误差在12%以内。

In order to study the fatigue gain of cold expansion⁃strengthening 7050 aluminum alloy hole components of aircraft fuselage,a combination of numerical simulation and experimental study is used to investigate the cold expansion strengthening process,fatigue loading process,fatigue crack initiation and crack propagation process of hole components.The stress distribution and corresponding fatigue behavior of hole components at different states of the dangerous cross⁃section are investigated by numerical simulation,the influence of the residual stress field on the fatigue performance is analyzed,the intrinsic connection between residual stress and fatigue crack initiation and crack propagation is explored,and a numerical prediction model of the fatigue life of cold expansion⁃strengthening hole components is established.The results show that the residual compressive stress introduced by hole cold expansion strengthening can reduce the maximum tensile stress in the hole wall when hole components are loaded,change the location of fatigue crack emergence,inhibit fatigue crack emergence and crack propagation,and improve the fatigue life of 7050 aluminum alloy hole components by nearly 2 times.And the error of the fatigue life numerical prediction model is within 12%.