Structural Analysis of a Formula Student Spaceframe Using a Suspension-Integrated Torsional Model, Equivalent-Static Loading, and Modal Characterization

Abstract

Selecting an appropriate torsional stiffness requirement is essential for balancing structural rigidity and mass efficiency in Formula Student spaceframe chassis design. This study presents a suspension-informed framework for establishing a vehicle-specific torsional stiffness target and evaluating the structural performance of an AISI 4130 steel spaceframe using finite element analysis (FEA). A simplified equivalent-compliance model was developed using prescribed front and rear suspension roll stiffnesses of 133.07 and 221.37 Nm/deg, respectively. A parametric assessment of the equivalent chassis–suspension system established a nominal torsional stiffness target of 1600 Nm/deg based on diminishing returns, corresponding to 95.06% relative stiffness. An ANSYS Mechanical 2024 R1 beam-element model was employed to investigate torsional response, equivalent-static frontal, rear, and lateral loading, and free– free modal characteristics. A six-level mesh-convergence assessment yielded a torsional stiffness of 1651 Nm/deg at the selected 1 mm element size, exceeding the target by 3.2% and achieving a relative stiffness of 95.21%, with less than 1% variation upon further refinement. Under calculated frontal and rear loading conditions, maximum deformations of 21.906 and 8.191 mm were obtained, with reported minimum nominal factors of safety of 1.299 and 1.987, respectively. The lateral assessment produced a maximum deformation of 5.575 mm and a minimum nominal factor of safety of 1.837. Free–free modal analysis identified a first flexible natural frequency of 33.271 Hz. The results demonstrate the applicability of suspension-informed stiffness selection integrated with numerical structural assessment, while emphasizing the need for experimental validation and careful interpretation of equivalent-static loading assumptions.