Finite element study on diameter and material effects of the torsional stiffness and modal characteristics of a solid anti-roll bar

Anti-roll bars (ARBs) play a critical role in vehicle roll stability by providing torsional resistance against relative wheel displacements during cornering and uneven road excitation. While torsional behavior is often evaluated using idealized straight geometries based on classical torsion theory, production anti-roll bars exhibit complex formed shapes and elastic mounting conditions that influence their mechanical response. In this study, the torsional stiffness and modal characteristics of a solid anti-roll bar representative of C-segment passenger vehicles are investigated using the finite element method. The bar diameter is varied parametrically from 19 mm to 28 mm, and three materials (26MnB5 steel, Ti-6Al-4V titanium alloy, and Al7075-T6 aluminum alloy) are considered to evaluate the influence of shear modulus. Polyurethane bushings are included in the torsional analysis using a hyperelastic material model to capture realistic compliance effects. Modal behavior is evaluated using an equivalent linearized representation of the bushings. The results show that torsional stiffness increases with both the diameter and the material shear modulus, consistent with theoretical expectations. At the same time, the absolute values are affected by geometry and bushing compliance. The findings provide practical insight for anti-roll bar design and highlight the limitations of simplified analytical models.