Weight Reduction of an OEM Suspension Control Arm via Reverse Engineering and Topology-Based Structural Optimization: A Comparative Finite Element Approach for GGG60–GGG70 Cast Irons

Abstract

Reducing the weight of control arms used in automotive suspension systems is a critical R&D topic in terms of fuel consumption, emissions, and raw-material cost reduction. In this study, a control arm currently produced through a combined casting and forging process has been redesigned through a methodology consisting of reverse engineering, 3D (GOM) optical scanning, CAD remodeling, finite element method (FEM) and topology-based structural optimization, with the goal of switching to a single-step casting process. Stress distribution of the reference design was analyzed under an initial load of 6,751 N at a 25° angle with a stepwise load increase to identify critical regions. Connection interfaces (ball-joint and bushing) were kept fixed; central hole and body wall thicknesses were optimized considering manufacturability constraints (mold suitability, flow). Two spheroidal-graphite cast iron alternatives, GGG60 and GGG70, were compared under fatigue test scenarios. In the optimized design, part weight was reduced from 7.036 kg to 5.414 kg (−23.06%; −1.622 kg per part), maximum stress decreased from 356 MPa to 284 MPa (−20.2%), and the critical region was relocated near the ball-joint. Both material alternatives satisfied the 1,000,000-cycle dynamic test criterion. Based on annual volumes and raw material costs, a significant cost advantage is achieved through material substitution alone. Furthermore, replacing multi-stage processes with a single casting method streamlines the production flow. The synergy between raw material savings and process optimization creates a sustainable net financial improvement. The methodology is scalable to the company's other OEM control arm families, providing an innovative design framework beyond the conventional copy-and-produce approach.