Abstract: Structural lightweighting is an important initiative in the automotive field due to regulatory fuel economy and emission requirements. For this purpose, a selectively reinforced aluminum hat section was designed and tested. The reinforcement shape and thickness were determined through topology optimization and the reinforcement was applied to the aluminum blank via Ultrasonic Additive Manufacturing (UAM). This study focuses on the bending properties and specific energy absorption of the structure for an automotive application. To understand the performance of the reinforced hat section, a multi-step model was developed to simulate the three-point bending behavior of the structure, as well as the forming and unloading processes. The model was used to calculate hardening from the plastic strain, and to map the residual stress in the reinforced hat section. To facilitate sheet metal forming analysis efficiency, a simple constitutive law was selected from among various forming analysis theories. The selected numerical model utilized shell elements and material properties defined by isotropic hardening and ductile damage models. The unloading process emulated the actual process after stamping and showed a significant influence on the residual stress in the structure. Numerical analysis was carried out using explicit FEA method and verified by experiments.
Authors: Hyunchul Ahn, M. Bryant Gingerich, Ryan Hahnlen, and Farhang Pourboghrat
Keywords: aluminum hat section, finite element method, sheet metal forming