A study on fatigue behavior of MIG-welded Al-Mg alloy with different filler-wire materials under mean stress

被引:55
作者
Gaur, Vidit [1 ]
Enoki, Manabu [1 ]
Okada, Toshiya [2 ]
Yomogida, Syohei [2 ]
机构
[1] Univ Tokyo, Dept Mat Engn, Bunkyo Ku, 7-3-1 Hongo, Tokyo 1138656, Japan
[2] UACJ Corp, Res & Dev Div, Minato Ku, 3-1-12 Chitose, Nagoya, Aichi 4558670, Japan
关键词
Fatigue; Aluminum; Porosity; Weld; Mean-stress; FRICTION STIR WELDS; CRACK CLOSURE; FRACTURE SURFACE; ALUMINUM-ALLOYS; CASTING DEFECTS; LIFE; STRENGTH; GROWTH; MICROSTRUCTURE; PROPAGATION;
D O I
10.1016/j.ijfatigue.2017.11.001
中图分类号
TH [机械、仪表工业];
学科分类号
0802 ;
摘要
Cylindrical specimens of phi 5 mm were cut from the weld bead of 50 mm thick MIG-welded Al-Mg alloy (Al-5083) plates with two different filler materials: Al-5183 (commonly used) and Al-5.8%Mg (special hardened new alloy). Load-controlled fatigue tests were done at different stress-ratios (R = -1,-0.5,0.1,0.5) using sinusoidal wave at 30 Hz and the performance of three popular finite-life empirical models: Gerber's parabola, Smith Watson-Topper's model and Walker's model, was studied using the experimental data. Fatigue lives and endurance limits of both materials did not differ significantly, but they got reduced when the R-ratio was increased and the endurance limit followed the Gerber's parabola. A non-monotonic trend in the slope of S-N curves was observed: first increases and then decreases. Fracture surface observations revealed majority of surface-initiated failures at lower R-ratios (-1,-0.5), while for higher R-ratios (0.1,03), defect-induced failures were predominant. This shift in crack initiation site was attributed to the local cyclic plasticity due to stress-concentration and demonstrated using elastic-plastic finite element (FE) simulations. The detrimental effect of mean-stress on fatigue lives was attributed to combined effects of reduction in crack-nucleation time: due to stress concentration at defects and the crack closure effects. The three fatigue life models predicted monotonic decrease in slopes of S-N curves and thus did not give best results. A new model, based on Walker's model, was proposed which was able to capture the observed non-monotonic trend of the slopes of S-N curves and predicted fatigue lives better than these models.
引用
收藏
页码:119 / 129
页数:11
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