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Abstract
Turnout frog section often causes significant wheel impacts that are primarily attributed to both the frog profile geometry, which includes a gap (i.e., flangeway), as well as the variation in vertical track stiffness along the turnout, mainly caused by the presence of a stiffer section like the frog. Building on the optimized #20 rail-bound manganese (RBM) frog geometry from the literature which achieved a 46 % reduction in wheel impacts, this study aims to further reduce wheel impacts and minimize track stiffness variations by optimizing turnout elasticity. A full turnout multibody simulation (MBS) model was developed using the commercial software VI-Rail, and three rail pad stiffness levels with four UTP properties were investigated under five representative revenue service wheel profiles. The results demonstrated that for wheel profiles transitioning smoothly without dropping onto the frog point, the adoption of soft rail pads reduced wheel impact. Conversely, for worn wheel profiles with hollow tread wear, the behavior was reversed. The soft rail pads caused more accelerated vertical trajectory drops and an earlier transition, resulting in a steeper dip angle in the vertical wheel trajectory, which increased wheel impact. The effect of various UTP properties on track performance was also investigated and showed minimal influence on wheel impact magnitude maximum variation of less than 1 %. However, the forces transferred from the crosstie to the ballast was reduced by 29 % with the use of soft UTPs compared to the scenario without UTPs. Additionally, the appropriate configurations of rail pad and UTP properties resulted in consistent track stiffness along the turnout, with displacement and corresponding stiffness variations limited to 2.3 % and 6.9 % for switch and frog sections, respectively. The findings of this study can provide valuable insights into optimizing turnout elasticity, thereby reducing wear and damage leading to longer life cycles and fewer maintenance interventions.