Experimental study of the Effect of Mechanical Joining on Energy Absorption of Bilayer Tubes Produced by flow Forming Process

Thin walled tubes are the most efficient energy absorption systems due to their lightness, high energy absorption capacity, and large crushing distance. In this process, a primary tube can be gradually deformed in to the desired thickness and length using simple roller. In this study, mechanical joining of aluminum and steel tubes is investigated to manufacture the bilayer tubes. Mechanical locking through the plastic deformation between two layers has been investigated under specified process conditions. To create a mechanical locking, the two layers were threaded with coarse and fine threads, and then using the warm flow forming the bonding between them was enhanced. It was concluded from the shearing test that the strong bond between the two layers can be created using the flow forming process. Also crushing test of bilayer tubes prepared by pressing and flow forming, have been investigated and it was found that the pressed sample with annealed Al layer has better energy absorption. The flow formed tubes with fine threads have better crushing energy absorption.