Crushing performance of cost-effective tubular components of AA 5083-O fabricated through friction stir welding process for automotive application

Tubular components of aluminium alloys find application in body-in-white to achieve weight reduction owing to growing demand of fuel efficiency in new age vehicles. However, fabrication of tubes through conventional extrusion route are restricted by tube size, cost and expensive dies. Therefore, tubular structures of AA 5083 (length to diameter ratio 2.5) were successfully fabricated cost-effectively adopting friction stir welding (FSW) process by designing an indigenous setup and a concave shoulder tool. Subsequently, the effect of weld zone (WZ) on crushing characteristics of welded tubes were assessed by compressing these tubes in axial and lateral directions between two flat platens. It was detected that the welded tubes underwent concertina mode of deformation during axial crushing, showing that the WZ had negligible impact on the collapse pattern. However, in lateral crushing formation of plastic hinge started from the WZ due to its thinning during welding. It is noteworthy that the WZ could withstand severe plastic deformation under non-linear strain path without any failure because of increase in its strength by approximately 87% as compared to base material (AA 5083), and less inhomogeneity amongst various zones. The specific energy absorption of tubes was found to be approximately 30 and 1.6 kJ/Kg during axial and lateral crushing, respectively. These values were found to be comparable with that of extruded tubes crushed under the above loading conditions reported in existing literature. The findings of the present work will encourage automotive industries to implement FSWed tubes as thin-walled energy absorbers to sustain different loadings during an event of crash.