铝合金点焊拉剪接头疲劳性能及寿命分析

摘要

Fatigue performance of spot welds of aluminum alloy AA5754 was investigated experi-mentally herein .Fatigue failure mode of spot welded tensile shear specimen was discussed and fatigue crack growth path was also explored .Theoretical crack growth angle was determined for tensile shear specimen ,which was under mix mode I/II loading ,and results were verified by measured angles of failed specimens .Local stress intensity factor at nugget circumference was derived ,modified by actual fatigue crack length in sheet thickness and treated as a fatigue parameter K(i) in fatigue data correla-tion .The proposed fatigue delete parameter is proven efficient in correlating fatigue data and can be used for fatigue life prediction of aluminum resistance spot welds .%研究了铝合金A A 5754点焊拉剪接头的疲劳性能，获得了不同厚度试件的载荷寿命曲线。研究了铝合金焊点的疲劳失效模式，讨论了焊点疲劳裂纹的扩展形式，并测量了裂纹扩展路径与点焊熔核界面之间的角度。分析了点焊拉剪试件在同时承受I型和II型载荷时，疲劳裂纹的扩展方向，并与测量值进行了比较。利用疲劳破坏后沿铝板厚度方向的实际裂纹长度修正了裂纹尖端的局部应力强度因子，提出了评价焊点寿命的疲劳参量 K （i），并对试验数据进行了分析比较。结果证明 K （i）可以有效关联试件尺寸效应和焊点疲劳寿命，能够用于预测焊点疲劳寿命。