Abstract
A bumper beam plays the important role of absorbing the bulk of impact energy, so it is extremely important to determine the bumper beam section during the initial stage of car development process. This paper presents a new method for the 5mph vehicle’s bumper section shape optimization. The design variables were set as the length and thickness making up the section shape of the bumper beam. In addition, the objective function was defined as the sectional area of the bumper beam, and the constraints, the maximum allowable deflection. In this optimization process, Intermediate Response Surface Modeling (IRSM) technique is newly introduced to approximate the nonlinear force-deflection curve. By using the surrogate model in developing the force-deflection curve, the process was further simplified by reducing the number of degrees of the IRSM function using intermediates rather than directly using the shape variables of the bumper section. To verify the effectiveness of IRSM, the results for 5mph impacts with arbitrary section shapes were compared with those of the 3D nonlinear FEM. The accuracy of the IRSM models was verified with an error rate of not more than 3%. This method can avoid the excessive 3D nonlinear FEM analysis during the optimization process. From these results of actual analysis, the feasibility of the proposed optimization strategy was validated. And a graphic user interface is developed for design engineers to evaluate the baseline design and to create an optimized cross section design. Finally it is shown that the proposed approach is effective to design the 5mph vehicle bumper section.
Keywords: Bumper Section, Shape Optimization, IRSM (Intermediate Response Surface Modeling)