Practical Optimization for Automotive Sheet Metal Components

Forming simulation has now reached an acceptable level of accuracy. It is possible to predict the hardening, the thinning and required forces for sheet metal stamped parts and it is also possible to predict the geometrical defects such as springback, wrinkling and surface appearance problems. Sheet metal forming can therefore be used in a closed loop to help design of parts and required tools in order to achieve a pre-defined geometry and mechanical performance. The paper presents a practical optimization methodology applied to automotive sheet metal stamped parts. The goal is to automatically optimize tool geometry in order to achieve an optimal part. An optimal part is regarded as a part free of defects. The defects are classified in two categories: material and geometrical. Material defects prevent the forming of the parts which can be in the form of a premature failure or an excessive wrinkling. The geometrical defects prevent the formed part from being assembled to the body structure and are generally referred as “springback”. In order to establish this optimization methodology, available tools for optimization and automatic geometry modification were coupled to LS-DYNA [1]. A special attention was paid to the definition of the optimization problem: appropriate selection of design variables, definition of the response functions in order to characterize the possible part defects (material or geometrical) and specification of the required physical constraints. The developed methodology will be demonstrated on actual automotive components