Fatigue behavior of dissimilar spot friction welds in lap-shear and cross-tension specimens of aluminum and steel sheets

• Published in: International journal of fatigue Vol. 32; no. 7; pp. 1167 - 1179
• Main Authors: Tran, V.-X., Pan, J.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.07.2010; Elsevier
• Subjects: Aluminum; Aluminum base alloys; Applied sciences; Binary systems; Dissimilar Al/Fe weld; Exact sciences and technology; Fatigue; Fatigue (materials); Fatigue behavior; Fatigue failure; Fracture mechanics; Friction; Friction stir spot weld; Interface crack; Joining, thermal cutting: metallurgical aspects; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Sheet metal; Spot friction weld; Welded joints; Welding; Dissimilar Al/Fe weld; Spot friction weld; Interface crack; Fatigue behavior; Friction stir spot weld; Shear; Mechanical properties; Fatigue; Steel; Welded joint; Friction; Sheet metal; Spot welding; Friction welding; Interface; Dissimilar metals
• ISSN: 0142-1123; 1879-3452
• DOI: 10.1016/j.ijfatigue.2009.12.011

Fatigue behavior of dissimilar friction stir spot welds or spot friction welds in lap-shear and cross-tension specimens of aluminum 6000 series alloy and coated steel sheets is investigated based on experiments and three-dimensional finite element analyses. The Al/Fe spot friction welds in both types of specimens were tested under quasi-static and cyclic loading conditions. Optical micrographs of the welds after failure under quasi-static and cyclic loading conditions show that the Al/Fe welds in both types of specimens mainly fail along the interfacial surface between the aluminum and steel sheets. Three-dimensional finite element analyses based on the micrograph of the weld before testing were conducted to obtain stress intensity factor and J integral solutions for the crack fronts along the nugget circumferences of the welds in both types of specimens. The computational results suggest that the J integral and in-plane effective stress intensity factor solutions at the critical locations of the welds obtained from three-dimensional finite element analyses may be used as fracture mechanics parameters to correlate the experimental fatigue data for the Al/Fe spot friction welds in both types of specimens. Finally, the computational results are used to explain the experimental observations of the fatigue crack growth patterns of the welds.