Experimental investigation into the bending energy absorption of hybrid aluminum/high strength and mild steel thin-walled sections joined by clinching

The employment of hybrid material thin-walled sections in the vehicle body structure is an emerging approach adopted towards manufacturing of lightweight energy-absorbing components in the automotive industry. Utilizing multi-materials such as aluminum-steel in the automotive industry poses some manufacturing challenges in terms of joining technologies of dissimilar materials. Clinching is a cold forming process that includes severe local plastic deformation of the sheets leading to permanent mechanical interlock. This study undertakes the experimental investigation of bending energy absorption of the clinched top-hat thin-walled beams by means of a series of quasi-static three-point bending tests. Different types of clinched beams including homogeneous as well as hybrid material beams, with aluminum alloy Al5052/SPCC mild steel and Al5052/SPFC 390 high strength steel combinations, are studied. The bending behavior of such beams under two different loading conditions is investigated and compared in terms of crashworthiness indices such as specific energy absorption (SEA), initial peak force (F-ip) and crash force efficiency (CFE). It is found that although the hybrid clinched beams show higher SEA as well as lower F-ip than their steel counterparts, their CFE values are lower than the steel beams. Furthermore, the sheets arrangement change with respect to the punch and the die is shown to influence the energy absorbing capability of the hybrid clinched beams. Moreover, it is revealed that while the clinched beams show reduced F-ip under the load applied to their hat-shaped part, they exhibit lower CFE values compared to when the load is applied to their plate part. Finally, considering SEA, F-ip, and CFE as three criteria, TOPSIS as a multi-criteria decision-making method is employed to select the best compromise design solution.