Abstract
Keywords
Bumper Beam, Hybrid Technology, High Strength Steel, Plastics, Crash
Abstract
The increasing demand for vehicle safety leads to higher car weight. This conflicts with further demands for low fuel consumption necessitating additional measures for weight reduction. Therefore, the mission of the bumper beam is to reach car crash performances (low speed impact, 15 km/h offset barrier or reparability impact test (Danner), high speed test and recently pedestrian test). And more precisely, it is necessary to avoid plastic deformation of the vehicle body frame during low speed impacts (up to 16 km/h). In the same time, the bumper beam must not undergo plastic deformation for low speed impacts (up to 4km/h), rupture for a 15 km/h velocity impact6, 56-64 km/h crash. This paper deals with experimental and numerical studies on a complete bumper system, including crash boxes and hybrid bumper comparing it with an existing aluminium bumper system. Metal Plastic Hybrid is used for bumper beam due to its mechanical characteristics: strength to weight ratio. An opened section profile with optimal inertia is used wherein crash boxes are positioned: each crash box has additional working volume. Real test results correlated by simulation work on both systems provide evidence of the high performance ability and efficiency of the hybrid solution and regarding all crash specifications. It presents the application of the hybrid technology as a bumper material aiming at the improvement of the global response regarding specifications. With reference to a medium size car and an existing aluminium bumper beam, hybrid bumper, made from polyamide overmolded high strength steel, is described. Then, a complete bumper validation plan including corrosion, static and dynamic tests is explained as well as correlation work: results, possibilities (improvement and integration advantages) and advantages. Finally, extensive simulation work based on experience plan aiming at the development of a designing tool and helping in the choice of steel grade and thickness according to different car segment is presented.