Evaluation of the crash energy absorption of hydroformed bumper stays

Because flanges provide the sole area of contact between a conventional bumper stay and a bumper beam, a substantial load concentrates on these flanges when an impact is applied to the bumper beam. It is difficult to distribute the load from such impacts, since the traditional bumper stay is not capable of absorbing a large amount of energy. In the present study, the crash energy absorption of bumper stays that were produced by a hydroforming process has been evaluated with static compression tests and impact tests. To hydroform a bumper stay, the tube specimen in the guide zone is fed into the expansion zone with a linear increase in pressure, while a compression load is applied to the folded region. Static compression tests were conducted to evaluate deformation behavior and the absorption energy of the bumper stays under various strain rates. The impact tests were conducted under conditions stated in the CMVSS215 specification. Results show that a hydroformed bumper stay exhibits good impact resistance, as compared to a traditionally formed bumper stay.