Topology and Free Size Optimization With Manufacturing Constraints for Light Weight Die Cast Automotive Backrest Frame

Abstract

Finite element analysis, together with topology and free-size optimization is used to design a lightweight die cast automotive front seat backrest frame when subjected to loads prescribed by ECE R17 European government regulations and additional loads which are predicted in an event of crash. In particular, an effort is made here to study the characteristics of a die cast automotive front seat backrest frame and develop a method for predicting the optimized material and support rib distribution which provides a lightweight seat which satisfies both strength and deflection requirements in a design space which includes the action of multiple load cases. An existing commercially available die cast backrest frame serves as the reference design space. Both 3D surface and solid models are created for representation as shell and solid finite element models for analysis. The objective function for topology optimization of the 3D solid model is to minimize mass of the component subject to stress and deflection constraints and is used as a guide in determining optimal geometric distribution of stiffening ribs. When the shell model of the reference seat is subjected to free-size optimization with this same constraint and objective given, an optimized material distribution measured by shell element thicknesses is obtained. For the topology optimization, manufacturing constraints of preferred draw direction and symmetry are applied in order to obtain an optimized material distribution which can be manufactured in the die-cast process. The procedure followed in this work generated an optimal material distribution and stiffening ribs in a lightweight die cast automotive seat backrest frame when subjected to multiple load cases. An overall reduction in weight of 13% is achieved over a reference commercially available die cast backrest frame component.