Study On Hydroforming And Crashworthiness Of Free Inversion Bumper Stay

The free-inversion bumper stay produced by hydroforming has good performance in energy absorption. The crashworthiness of vehicle bumper can be improved considerably by using free-inversion bumper stay. And this can improve the crashworthiness of vehicle and reduce the repairing cost.The object of study is the free-inversion bumper stay. The process of free-inversion energy absorption and hydroforming of the bumper stay have been analyzed in theory. And the structure and manufacture design methods of free-inversion bumper stay are summarized.Based on the domestic and overseas research production, the effects of structure parameters and technological parameters of hydroforming is studied by using finite element program ABAQUS. The analysis results show that the diameter of the bulging region and the axial feed on the stadge of transitional region forming have great effects on the form of energy absorption of the free-inversion bumper stay. And the diamater and thickness of tube have significant impact on the deformation force of the free-inversion bumper stay.Base on the above study, two kinds of free-inversion bumper stays are designed separately to improve the energy absorption characteristic of the vehicle bumper and to reduce the mass of the vehicle bumper. The energy absorption characteristics of the vehicle bumper with the two kinds of free-inversion bumper stays are analyzed by using finite element program LS-DYNA. The results show that the value of energy absorption can improve 28.6% with the mass of the bumper stays decreasing 9.5% by using one kind of free-inversion bumper stay. And the mass of the bumper stays can decrease 34.3% without decreasing the value of energy absorption of the vehicle bumper by using the other kind of bumper stay.