Implementation of Friction Stir Welding in Car Bumper Assemblies

CFSP - Wichita State University - Advancements in weld tool designs for friction stir welding (FSW) have enabled the development of a prototype lightweight automotive bumper / crash box assembly. Assemblies fabricated with FSW and Gas Metal Arc Welding (GMAW) were subjected to crash sled and drop tower testing to provide a comparison in performance under dynamic loading conditions. The FSW development work included micro-structural examination and static mechanical testing. Results from coupon-level development were compared against results from component-level testing of prototype articles using micrographs and an advanced electronic (signal/frequency analysis) non-destructive evaluation (e-NDE) technique in order to detect weld anomalies primarily in the form of voids. Due to the geometry of the welded part joint, conventional mechanical testing methods (tensile and peel test) were not applicable. Therefore, a wedge test was devised to test the relative toughness of the FSW joint.

A drop tower test fixture was also fabricated using friction stir welding. Finite Element Analysis (FEA) was used to compare the predicted damage to the actual damage in FSW bumper and FSW test fixture joints. According to the bumper test results, friction-stir butt welds performed as well as or better those produced by GMAW.