PSI - Issue 82

Kübra Polat et al. / Procedia Structural Integrity 82 (2026) 267–273 K. Polat, M. M. Topaç/ Structural Integrity Procedia 00 (2026) 000–000

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4. Results and discussion 4.1. Identification of the Critical Driving Case

Critical regions were identified by examining the stress distribution using FEA results. The results show that, as expected, the lowest stress concentrations occur at the neutral axis and the highest stress concentrations occur at regions far from the neutral axis The stress at the neutral axis was used as a reference to normalize stresses in other regions. These high stress regions are named CP 1 and CP 2 . Tensile stress is known to have a high failure tendency (Eryürek, 1993) and therefore, the CP 2 region under tensile stress was defined as a critical area. The section and stress distribution taken from the axle beam are shown in Fig. 4a. Thirteen points (P 1 –P 13 ) were selected from the CP 2 region to determine the critical load case. Equivalent stresses at these points were compared under sixteen loading cases, with the lowest stress at Load Case 13 taken as a reference. The other loading cases’ stress values were then normalized according to this reference. Fig. 4b shows the selected points on the axle beam and the corresponding stress values at these points. The highest stresses occurred under the Vertical Impact (3G) condition, defined as Load Case 2, which was selected as the critical loading case. This case was then used in topology optimization to identify regions suitable for mass reduction on the front axle. 4.2. Topology Optimization-Based Mass Reduction Topology optimization was performed in ANSYS® Workbench. The regions aimed for mass reduction were defined as design areas, while the preserved regions were designated as exclusion areas. From the FEA results, low stress regions were selected as suitable design areas for material removal. These regions and the resulting topology optimized model are shown in Fig. 4c. ! ! !

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Fig. 4. (a) Von Mises stress distribution and stress behavior of the cross-section regions; (b) Selected points on the axle beam and the stress values obtained at these points; (c) Design and exclusion regions defined for topology optimization.

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Holes for weight reduction reduce the axle mass, but they can also affect vehicle behavior by altering structural stability, so their design is very important. Topology optimization results were used to determine the most suitable hole form for the axle beam by applying hole geometries from the literature (Yan et al., 2022). Within this scope, four axle beam designs were built, and their maximum stress values under critical loading case (Case 2) were investigated. Fig. 5 shows different hole forms and the axle beam designs built using these forms. Models 1, 2, 3, and 4 represent the race-track hole, circular hole, elliptical hole, and four-arc hole forms, respectively. In all axle beam models, the H distance (from the beam centre to the top of the hole) and hole length L are kept constant. According to topology optimization, the holes in Hole 1 and Hole 3 are designed with length L, while Hole 2 is designed with length 1.25 L to maintain the cross-sectional thickness of the spring seat area. This prevents excessive vertical deformation and possible changes in the camber angle. Analysis results for different hole shapes are shown in Fig. 6.