Geometry-Based Topology Optimization - Improving Head Impact Performance of an Engine Hood

The actual paper introduces the integration of LS-DYNA and CATIA V5 into automatic geometry- based topology optimization of an engine hood regarding pedestrian head impact. In current design processes, such Computer Aided Engineering (CAE) tools, along with structural optimization, have become essential elements to provide efficient and reliable structures. However, the required iterative process of adjusting steps between simulation and design engineers is still a time-consuming task. In recent years therefore, automatic multi-criteria and multi-disciplinary optimization simultaneously considering different simulation disciplines have drawn increasing attention. For structure creation or topology variation, FE-based concepts have been developed working on a discretized design space, whereas geometry-based parameter variation on CAD models has been mainly used for shape and size variation. Although being a first step toward design process automation, both concepts are a trade-off between accuracy and creativity. The final goal would therefore be to combine the topology variation ability of the FE-based method with the ready-to-use solution of the parameter concept. Hence, extending the idea of parameter variation with the addition and removal of entire geometrical features, automatic topology variation on CAD structures is introduced. However, applying such geometry variation implies further considerations regarding a fully automated optimization loop such as accurate CAD build-up, update-stability, high quality batch meshing and a rapidly increasing number of free parameters. The project this work is based on aims at full automation of a geometry-based optimization loop for optimum structure generation using CATIA V5 and LS-DYNA. The concept is applied to pedestrian safety considerations, analyzing different engine hood topologies regarding their head impact performance. In a first step, parameter studies and simplified impactor load cases are run using the automatic CAD- FE loop as a pre-stage to a full multi-criteria optimization. The paper's focus is set on the concept's applicability to industrial processes. Hence, solutions regarding automated CAD-FE transition for evaluation are discussed as well as general limitations of CAD-based topology optimization. In particular the demanding task of batch meshing for varying topologies and sensitivity analyses to reduce the number of free parameters are addressed.