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This paper presents the results of fatigue tests conducted on tailor-welded aluminum blanks consisting of 1.66 mm thick and 1.06 mm thick AA 5754-O sheets. The method of joining the sheets was friction-stir welding. The primary purpose of this study was to determine the effect of tensile pre-strains on the fatigue performance of the welded joint. The welded specimens as well as unwelded 1.06-mm thick specimens were subjected to tensile pre-strains of 60 and 80% of their respective uniform strains before the fatigue tests. Fatigue S-N data of all these specimens were compared with similar data for unstrained specimens. Microscopic examinations were conducted to understand the failure modes.

An experimental study was conducted to investigate the potential of spot joining aluminum with nylon using frictional heat. The process utilizes the heat generated by friction between a rotating tool surface and the aluminum sheet surface to melt nylon locally in the joining area and create a mechanical interlock between the aluminum and nylon sheets. Lap shear joint specimens were prepared using this process to investigate the effect of several parameters such as tool geometry, tool RPM, tool hold time, tool plunge depth and tool feed rate. Tensile tests were conducted to evaluate the joint strength and to investigate the failure mechanisms of the joint. Furthermore, the effects of cleaning the aluminum surface and baking of the nylon on the joint strength were also studied in this paper. Finally, friction heat generated joints were compared with adhesively bonded joints between aluminum and nylon.