Robust Design of an Automobile Front Bumper Using Design of Experiments

Abstract

Bumpers are structural components installed to reduce physical damage to the front and rear ends of a passenger motor vehicle from low-speed collisions. Damage and protection assessments are the commonly used design criteria in bumper design. For damage assessment, the relative displacements representing stiffness performance are defined and examined. At the protodesign stage for a new car, finite element (FE) analysis is often utilized to predict the stiffness of a bumper. However, conventional bumper analysis through FEM outputs a constant stiffness even though the stiffness has some distribution due to uncertainties. In this research, the uncertainties are assumed to be the tolerances of thicknesses. Under this uncertain condition, the displacements representing stiffness are calculated by approximate statistics and by worst-case analysis. Then, a robust design is determined by design of experiments (DOE) using the orthogonal array strategy to find the design having a minimum weight of bumper within the stiffness constraints. In this research, the thicknesses of the inner beam, outer beam, and stay are treated as design variables. The robust design procedure for a bumper, considering the uncertain thicknesses, is presented.