A finite element simulation is presented for the prediction of residual stresses resulting from the heat treatment of railroad commuter car wheels during manufacture. The quenching and annealing segments of the wheel manufacturing process are simulated using a decoupled heat transfer and stress analysis. A set of baseline parameters which characterize geometry, material properties and quench characteristics is developed which are representative of current rim-quenching practice. Results indicate the formation of a layer of residual circumferential (hoop) compression to a depth of about 4 cm (1.5 inch) from the tread surface. Variations of these parameters which account for expected ranges in the manufacturing process are shown to have little influence on this finding. The as-manufactured net rim compressive residual stress may be reversed when subjected to service loading in railroad commuter operations. This situation is examined in a companion paper. Tensile stresses at the wheel tread create an environment conducive to the formation of surf ace cracks that may threaten the safety of train operations. The results of the studies presented in this paper are required to define the initial conditions for analyses of how service conditions may act to change the as-manufactured residual stress state.

Estimation of residual stresses in railroad commuter car wheels following manufacture

A study into crack growth in a railway wheel under thermal stop brake loading spectrum

Analyses of the effects of service conditions on the distribution of residual stresses in railroad commuter car wheels are presented. Novel software has been applied to estimate the effects of service conditions on the as-manufactured state of these wheels. Contact loads resulting from wheel and rail interaction and thermal loads from on-tread braking are considered. Results indicate that contact stresses acting alone result in increased net rim hoop compression. However, thermal stresses due to frictional heating reverse the as-manufactured residual compressive state. In particular, high-performance stop braking may result in large net hoop tension in the rim. When contact and thermal loads interact, the effects of braking dominate the process. The presence of tensile residual hoop stress at the wheel tread has been shown to favor the formation and growth of fatigue cracks, threatening the safety of train operations. The paper provides a description of the analytical methodology and results of its application to a representative class of commuter service. Comparisons of the predicted depth of rim stress reversal with the thermal cracking observed in the wheels of this fleet provides confidence in the ability of the technique to assess the likelihood of thermal crack development in other types of commuter operations and in railroad freight service.

Evaluation of service-induced residual stresses in railroad commuter car wheels

Effects of service conditions on the as-manufactured residual stress distribution in commuter car wheels

Effects of wear and service conditions on residual stresses in commuter car wheels

A finite element formulation for shakedown stress analysis of rail vehicle wheels is presented, based on a hypothesis that the shakedown state is axisymmetric. The method can be used to estimate shakedown stresses in wheels subjected to combined mechanical (wheel/rail contact) and thermal (temperature gradients and thermal stress due to braking) loads. The formulation includes provisions for initial manufacturing stress, shifting contact locations, and temperature-dependent material properties. Validation results and demonstration example analysis of an actual wheel design are presented.

E S Bobrov

Papers

Estimation of actual residual stresses due to braking and contact loading of rail vehicle wheels