A Multi-Stage Topology Optimization Approach for Lightweight Automotive Upright Design

Lightweight structural design is a critical objective in automotive engineering, particularly for suspension components that directly influence unsprung mass and vehicle dynamics. Although topology optimization is widely used to achieve high stiffness-to-weight ratios, conventional approaches are often limited by single-objective formulations or by a lack of geometric interpretability in multi-objective solutions. This study proposes a multi-stage topology optimization framework for the conceptual design of an automotive suspension upright. The methodology decouples stiffness-driven and stress-driven optimization processes and introduces a parametric synthesis stage in which key structural features from both solutions are systematically integrated into a geometrically interpretable design. The framework is evaluated on a Formula SAE front upright under representative braking and cornering load conditions. The resulting hybrid configuration achieves a 29.44% reduction in mass (from 616.9 g to 435.3 g) while maintaining structural performance, with a maximum von Mises stress of 220.0 MPa, a safety factor of 2.28, and a maximum deformation of 0.88 mm. The results demonstrate that the proposed approach enables a balanced integration of stiffness and stress criteria through feature-based design synthesis. Beyond numerical performance, the methodology provides a reproducible and interpretable workflow that bridges topology optimization and practical engineering design.