Cost and Mass Optimization for Crashworthiness Design of Shell-Based Structure Using Hybrid Cellular Automata

Abstract

The hybrid cellular automaton (HCA) method has been successfully applied to nonlinear transient topology sizing optimization for crashworthiness design. This method utilizes the cellular automata (CA) computing paradigm and nonlinear transient nite element analyses (FEA). In earlier eorts, the HCA algorithm has been used to develop an ecien t methodology for synthesizing sheet metal structures with optimal material thickness distribution under a dynamic loading event using a thickness based topology sizing optimization. In thickness based topology optimization, the objective is to redistribute element thickness to meet the desired performance constraints. The objective in crashworthiness design is to generate energy absorbing structures which can be obtained by uniformly distributing internal energy density (IED). In this paper, the HCA algorithm is utilized to do simultaneous thickness and cost optimization for structures suitable to be manufactured by the tailor welded blank (TWB) technology for signican t mass savings. The sheet metal structure can have dieren t material parts, and the optimum distribution of the material and thickness is obtained to meet the desired performance using nonlinear transient analysis. This methodology is used to tackle complicated problems that involve dynamic events, such as impacts and collisions. The existing commercial thickness optimization tools utilize models under static loading conditions because of the complexities associated with dynamic/impact loading and they are not suitable for design with multiple material and thickness distribution simultaneously. The HCA based thickness optimization algorithm employs nonlinear transient analysis (via LS-Dyna) to capture material and geometric nonlinearities that occur during a dynamic crash event. Therefore by applying this method to impact problems, the resulting structure will account for all phenomena involved. The eectiv eness of the algorithm is demonstrated using a at plate and C-section rail example problem subjected to single or multiple dynamic impact loading. The structures synthesized by the HCA algorithm are able to meet the manufacturing as well as performance constraints.