Residual Stresses in Passenger Car Wheels

Abstract

Knowledge of the residual stress state in wheels resulting from manufacturing and subsequent service loading is useful for several practical reasons. The ability to estimate residual stress levels permits the tuning of manufacturing processes to control the magnitude and distribution of these stresses in new wheels in order to achieve safe performance in service. Similarly, understanding the redistribution of residual stresses following application of service loads (wheel/rail contact and thermal stresses) is crucial to avoid operating conditions which may lead to premature wheel failure.Axisymmetric (2-dimensional) analyses are typically performed in order to conduct manufacturing process simulations since these processes affect the entire wheel in a circumferentially uniform sense.Generally, analyses involving service loading have sought to identify the "shakedown state" at which the residual stress distribution stabilizes after some number of loading cycles. In order to properly account for service loads, 3-dimensional models are required since contact and brake shoe thermal loading are not axisymmetric. Since the as-manufactured residual stress distribution must be considered in a service loading simulation, 3-dimensional modeling of this process is required. This paper presents a preliminary comparison of 2-and 3-dimensional modeling of the wheel heat treatment process. Except for the increased computational time required for the 3-dimensional analysis, the results agree favorably. The 3-dimensional model is used to simulate service loads involving wheel-rail contact loading representative of a typical passenger car. The model is exercised with a variety of material models for comparison with previous work. Results are presented for multiple loading scenarios and shakedown stress states are established for a range of applied loads. INTRODUCTIONResidual stresses are important to understand in order to avoid operating conditions which may lead to development of adverse stresses which can cause premature wheel failure. Residual stresses in wheels originate during the manufacturing process and are subsequently modified when wheels are placed in service and subjected to repeated wheel/rail contact and thermal loading during on-tread friction braking. The manufacturing process generally leaves the wheel rim in a state of residual compression. This compression helps to resist wheel tread crack formation. Thermal loading from ontread friction braking has been demonstrated to cause rim stress reversal from compression to tension, leading to the development of wheel tread thermal cracking.Early attempts to estimate residual stresses in wheels considered a combination analysis. Standard finite element techniques were applied to estimate the residual stresses due to the quenching and annealing portions of the manufacturing process [1,2]. These stresses were then used as an initial condition for subsequent consideration of mechanical (wheel/rail contact) and thermal (from friction braking) stresses that were ana...

Development of a Standard for New Passenger Car Wheel Designs

“…In the immediate vicinity of the point of application of the load, stresses are extremely large. This is due primarily to the fact that the loads are applied at a single node and not distributed over a contact patch as illustrated in [9]. More importantly, there are no regions of stress concentration anywhere else in the crosssection.…”

“…More realistic wheel-rail contact characterization is considered in a companion paper in this conference [9]. AAR Standard S-660 specifies locations on the wheel tread at which vertical and lateral loads are applied simulating wheel-rail contact.…”