LIGHTWEIGHT-FOCUSED STRUCTURAL OPTIMIZATION OF A TROLLEYBUS MOTOR MOUNTING BRACKET USING A TAGUCHIFEM APPROACH

Abstract

The increasing use of electric buses and trolleybuses in urban transportation requires the redesign of local structural components to achieve both lightweight performance and structural durability. In this context, the present study investigates the structural behavior and sheet-thickness optimization of a motor mounting bracket for a 12-m trolleybus using a combination of the Taguchi L9 orthogonal design method and finite element simulations. The analyses were conducted under quasi-static loading conditions assuming linear elastic material behavior, and boundary conditions representing the reaction forces transmitted from the traction motor to the chassis. Three geometric design parameters base sheet thickness, side sheet thickness, and stiffener sheet thickness were examined at three levels. Equivalent stress, displacement, safety factor, and mass were evaluated as response parameters, and the S/N ratio and ANOVA techniques were used to quantify parameter sensitivity and contribution to the variance of the mass response. The results indicate that the base sheet thickness is the dominant parameter governing the lightweighting performance of the bracket, while the side and stiffener sheets have comparatively lower influence. The optimum thickness configuration was identified as 5–4–5 mm, yielding a 15.5% mass reduction with respect to the 6–6–5 mm reference design while maintaining a safety factor above 3.18. The findings demonstrate that the Taguchi–ANOVA–FEM approach provides an effective decision-support framework for early-stage design of bracket-type structural components in electric bus traction systems. Moreover, the methodology is compatible with manufacturable design constraints and can be extended to multi-objective formulations including durability and fatigue performance in future studies.