Dynamic behavior analysis of the wheel-rail impact mitigation device for fixed frog gaps incorporating rubber's strain rate dependency

The wheel-rail interaction at the gap in the frog of fixed turnouts is characterized by discontinuous contact traces and nonlinear geometric profiles, which often induce transient impact vibrations with broad frequency ranges and significant amplitudes. This study develops a Wheel-Rail Impact Mitigation Device (WRIMD) through a combination of theoretical modeling and field testing. The aim is to address the discontinuity in contact traces and promote uniform distribution of wheel-rail forces. A transient rolling contact model for a 50 kg/m rail No. 9 turnout, integrating the bogie and frog, was constructed using the participating mass method, with computational efficiency enhanced through a hybrid Lagrangian-Eulerian approach. To address challenges in the definition of impact index parameters, this study introduced the concept of effective impact energy probability, providing a comprehensive framework for characterizing both global and instantaneous wheel-rail impact phenomena at the frog. The study identified the abrupt transition between single-point and multi-point wheel-rail contact at the gap as the primary driving mechanism for impact vibrations. The WRIMD has a dual-layer design, with an upper impact-resistant layer made of manganese steel and a lower damping layer made of rubber. Considering transient wheel-rail impact dynamics, a hyper-viscoelastic constitutive model for the rubber material was formulated by incorporating the relationship between impact velocity and strain rate. The optimal height of the damper was determined through a combined quasi-static and dynamic analysis. Simulation results indicated a 5.57 % reduction in the impact index and a 23.9 % decrease in total impact energy when the damper was implemented. Safety assessments under extreme operational conditions confirmed that the damper met all operational safety standards. Field installation of the damper, secured by bolting and adhesive bonding, demonstrated that it effectively reduced medium- and high-frequency vibrations above 100 Hz, with measured reductions of approximately 9 dB in frog vibration and 6 dB in sleeper vibration. This research further reveals vibration isolation in turnout substructures and presents an innovative solution for the management of transient wheel-rail impacts in fixed frogs.