Perpustakaan Digital ITB

The Modultrax is an electric utility motorcycle developed at Institut Teknologi Bandung, whose frame must carry the rider, battery pack, motor, and modular cargo while remaining light, stiff, and safe. Because the chassis had not been evaluated structurally and comparable studies typically rely on generic handbook data, omit mesh-convergence verification, and restrict loading to simple longitudinal cases, this research determined the von Mises stress and total deformation of the chassis under maximum acceleration, maximum braking, and rear bumping, evaluated the resulting safety factors against a yield-based criterion, and verified mesh independence. A quasi-static finite element analysis was performed in Ansys Mechanical 2025 R1. The geometry was simplified in SolidWorks 2022, the welded tubes were modeled as a single Boolean-merged solid, and the model was meshed with quadratic tetrahedral elements. A yield strength of 215 MPa, taken from the tube manufacturer's published specification for STKM 11A, was adopted as a conservative basis for the safety-factor evaluation, together with a handbook elastic modulus of 200 GPa. ASTM A370 tensile testing confirmed an ultimate tensile strength consistent with the STKM 11A grade but did not yield a reliable measured yield strength or elastic modulus, because the transverse curvature of the strip specimens extracted from the tube wall corrupted the elastic slope on which both quantities depend. Mesh independence was established on a cantilever-pipe benchmark verified against the Euler–Bernoulli deflection and Mc/I stress solutions, giving a 2 mm element size. A finite fillet radius at the welded junctions converted the singular re-entrant corners into bounded, mesh-convergent stress concentrations, so that each safety factor could be read directly from the converged peak stress. The chassis remained below yield under all three load cases, with minimum safety factors of approximately 5.55 (maximum braking), 1.29 (maximum acceleration), and 1.24 (rear bumping); the peak equivalent stress reached 173.39 MPa and the largest total deformation 4.88 mm. Rear bumping was the governing case, at a safety factor marginally below the adopted design threshold of 1.25 on a deliberately conservative material basis, with maximum acceleration a close second.These results identify the rear junction as the structurally critical location of the Modultrax chassis rather than a predicted failure site, since the 215 MPa floor and the suddenly-applied-load amplification place the assessment on a deliberately conservative footing under which the true margin is greater than the nominal factor suggests. The analysis therefore establishes a verified structural baseline for a chassis that previously had none, and localizes where subsequent experimental validation and transient dynamic assessment should be concentrated.