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Wear, rolling contact fatigue, and plastic deformation are the major failure modes of railway wheels and rails. Proper analyses of the failure mechanisms as well as improvement in design and maintenance require an accurate evaluation of the stress and strain states. Solution of frictional rolling contact between wheel and rail in elasto-plasticity seems, however, still to lack in the literature. This paper presents a model for such a solution. A 3D finite element model is built up to simulate the rolling contact. The focus is on the tangential problem, namely the distributions of surface shear stress and micro-slip as well as the distinction of areas of adhesion and slip in the contact patch. With the presented model the assumptions of half space, linear elasticity and quasi-static or steady state, which are often employed in existing solution of rolling contact, are dropped. A bilinear elasto-plastic material with isotropic hardening is employed to examine the effects of plasticity on frictional rolling. It is found that when plastic flow occurs, the contact patch in the rail top changes from an ellipse into an egg shape; the cross influence between the normal and tangential contact problems become stronger: the normal solution is not independent of the tangential solution any more, and the tangential solution is greatly affected by the normal solution. The model can be applied to investigation of the relationships between material properties, plastic deformation, frictional work, wear, and crack initiation. Such relationships may help in better understanding the occurrence of corrugation, head checks, and squats, and may further be used for design of fatigue resistant materials and profiles of wheel and rail.

A validated three-dimensional (3D) transient finite element model is used to evaluate the wheel-rail impact at singular rail surface defects and the resulted high-frequency dynamic forces at the discrete supports of the rail. A typical ballasted railway track is modeled, in which the supports of the rail are composed of the fastenings, the sleepers, and the ballast. The primary suspension of the vehicle is considered. To include all the important eigen characteristics of the vehicle-track system, the wheel set, the rail, and the sleepers are all meshed using 3D solid elements. The transient wheel-rail rolling contact is solved using a surface-to-surface contact algorithm in the time domain. By simulating the steady-state rolling of a wheel set on a smooth rail, the vertical force distribution at the discrete supports is first compared with Zimmermann solution. Afterward, rail surface defects are applied to calculate the resulted dynamic forces at the wheel-rail interface and at the discrete supports of the rail under different rolling speeds. The obtained dynamic responses confirm the necessity of using such a detailed model for the investigations.

A 3-D explicit finite element model is developed to investigate the transient wheel-rail rolling contact in the presence of rail contamination or short low adhesion zones (LAZs). A transient analysis is required because the wheel passes by a short LAZ very quickly, especially at high speeds. A surface-to-surface contact algorithm (by the penalty method) is employed to solve the frictional rolling contact between the wheel and the rail meshed by solid elements. The LAZ is simulated by a varying coefficient of friction along the rail. Different traction efforts and action of the traction control system triggered by the LAZ are simulated by applying a time-dependent driving torque to the wheel axle. Structural flexibilities of the vehicle-track system are considered properly. Analysis focuses on the contact forces, creepage, contact stresses and the derived frictional work and plastic deformation. It is found that the longitudinal contact force and the maximum surface shear stress in the contact patch become obviously lower in the LAZ and much higher as the wheel re-enters the dry rail section. Consequently, a higher wear rate and larger plastic flow are expected at the location where the dry contact starts to be rebuilt. In other words, contact surface damages such as wheel flats and rail burns may come into being because of the LAZ. Length of the LAZ, the traction level, etc. are varied. The results also show that local contact surface damages may still occur as the traction control system acts.

With up to 12 spring-damper groups distributed in the actual area of a rail pad, different fastening models are developed in this paper to include the nonuniform pressure distribution within a fastening system and model the constraints at the rail bottom more realistically for the purpose of high frequency dynamics between vehicle and track. Applied to a 3D transient FE model of the vehicle-track interaction, influence of the fastening modeling on the high frequency dynamic contact forces at singular rail surface defects (SRSDs) is examined. Two defect models, one is relatively large and the other is small, are employed. Such a work is of practical significance because squats, as a kind of SRSD, have become a wide spread problem. Results show that the fastening modeling plays an important role in the high frequency dynamic contact forces at SRSDs. Supports in the middle of the rail bottom, modeled as spring-damper groups located under rail web, are found to be most important. The less the rail bottom is constrained or supported, the more isolated the sleepers and substructure are from the wheel-rail interaction, and the more kinetic energy is kept in the rail after impact at a SRSD. Rolling speed is also varied to take into account its influence. Finally, based on the results of this work, influence of the service states of the fastening system on growth of relatively small SRSDs is discussed.