Fatigue Life Prediction of Aluminum Alloy FSW Lap Joints with Tunneling Defects
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摘要: 本文对含隧道缺陷的铝合金搅拌摩擦焊(FSW)搭接试件进行恒幅疲劳测试,并对接头断裂位置进行了观测,分析隧道缺陷对于铝合金FSW搭接接头疲劳强度的影响。分别采用缺口应力法和线弹性断裂力学法建立了相应有限元模型,分析了模型应力集中区域的应力变化,利用有限元应力分析结果数据预测接头疲劳寿命。结果表明,两种方法都可以用来预测含隧道缺陷铝合金FSW焊件的疲劳寿命,缺口应力法预测结果与实验结果较为接近,线弹性断裂力学法预测结果较为保守。实验结果及有限元分析结果表明,在本试验中隧道缺陷对疲劳强度影响较小,钩状缺陷对疲劳强度影响较大。Abstract: Constant amplitude fatigue experiments were carried out for aluminum alloy friction stir welding (FSW) lap joints with tunneling defects, and the fracture positionsin the jointsare observed, and the influence of the tunneling defects on the fatigue strength of aluminum alloy FSW lap jointsis furtherly studied. The notch stress method and linear elastic fracture mechanics method were used to establish the corresponding finite element models, and the stress changes in the stress concentration area of the model were observed, then the finite element analysis stress result were used to predict the fatigue life of the joints. The results showed that both methods can be used to predict the fatigue life. The prediction results of notch stress method are much closer to the experimental results, while the prediction results of linear elastic fracture mechanics method are relatively conservative. The experimental results and finite element analysis results showed that the tunneling defects have the slight effect on the fatigue strength, in while hook defects have greater effect.
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表 1 6061-T6铝合金化学成分
% ω( Al) ω(Si) ω(Fe) ω(Cu) ω(Mg) ω(Mn) ω(Ti) ω(Zn) ω(Cr) Bal 0.65 0.4 0.21 0.84 0.11 0.06 0.04 0.15 表 2 6061-T6铝合金力学性能
YS/MPa TS/MPa EL/% 281 328 14.0 表 3 加载方案一
试件号 最大载荷Fmax/N 最小载荷Fmin/N 载荷比R S001 900 90 0.1 S002 1000 100 0.1 S003 1200 120 0.1 S004 1400 140 0.1 S005 1540 154 0.1 S006 1700 170 0.1 S007 2000 200 0.1 S008 2700 270 0.1 S009 3400 340 0.1 表 4 加载方案二
试件号 载荷幅Fmax/N 平均载荷Fmin/N 载荷比R F001 1400 1800 0.13 F002 1300 1800 0.16 F003 1100 1800 0.24 F004 1000 1800 0.29 F005 900 1800 0.33 F006 700 1800 0.44 F007 690 1800 0.45 F008 600 1800 0.5 F009 500 1800 0.57 F010 450 1800 0.6 F011 400 1800 0.64 F012 300 1800 0.71 -
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