Topology Optimization-Based Design Roadmap and Fatigue Life Evaluation of a 4 × 4 Independent Suspension Special-Purpose Electric Scooter Stub Axle

This study presents a topology optimization-based design methodology for a fail-safe stub axle of a lightweight 4 × 4 electric scooter with independent suspension, with the objective of developing a structural design roadmap. Topology optimization was performed under five critical load conditions: vertical, longitudinal, and lateral impacts, as well as braking and cornering under braking, representing standard driving scenarios defined in the literature. The final geometry was built by combining the topology optimization results from each load case, and it was evaluated using finite-element analysis, showing that it is safe under all critical loading conditions with respect to yield strength. The fatigue life assessment was performed using the Goodman–Haigh approach, based on load-condition pairs recommended in the literature, and it was found that the stresses in critical regions remain within the infinite fatigue life region. In addition, based on literature data, the proposed lightweight design approach indicates potential benefits in terms of both energy consumption and manufacturing cost. Overall, the findings suggest that the presented methodology can serve as a fail-safe design roadmap for the development of electric vehicle components.