A tool to estimate the wheel/rail contact and temperature rising under dry, wet and oily conditions

Abstract

In this paper, finite element method (FEM) has been applied to evaluate the wheel/rail contact stress under different contact conditions. The elastic-plastic model coded in ANSYS/LS-DYNA includes a whole wheel, 680 mm of the canted rail, and sub-components of the track (railpads, sleepers, and ballast). The three values of friction coefficient 0.4, 0.2 and 0.07 have been chosen to model the dry, wet and oily environmental contacts, respectively. The high mechanical stresses exerted at the contact area will cause the temperature rise, which results in decreasing of the yield strength of the wheel/rail. The growth of temperature is a major source of the various microstructure changes that occurs on the rail surface, especially the formation of White Etching Layer (WEL). Therefore, a theoretical calculation of heat generation has also been implemented in the current research. The output data from the FEM models have been considered as the input for the theoretical thermal model to examine temperature rising on and beneath the rail surface. The combination of finite element method for contact stress and theoretical thermal method for temperature variation would provide a better understanding about wheel/rail contact under a variety of contact conditions (dry, wet, and oily). Various scenarios of damage mechanisms of rail have been considered in the paper.The obtained results from the model have revealed that the influence of environmental conditions on normal contact stress, pressure and contact area is negligible. In contrast, the magnitude of the Von-Mises stress and lateral and longitudinal stresses components can be significantly varied depending on the friction conditions. Moreover, the environmental condition has shown a major effect on the temperature rising at the contact zone.

The influence of high temperature due to high adhesion condition on rail damage

“…For instance, the temperature in case 1 (1st axle) and case 2 (3rd axle) was 522 1C and 342 1C, respectively. This tendency was consistent with the results calculated by the analytical method in [43]. In comparison: Between AC locomotives, the temperature produced by the loco C44ACi was higher than that by the loco GT46C ACe.…”

“…The verification of the 3D FE model was carried out by comparing the results to the existing data from the theoretical investigations [3,43,52]. It was found that the 3D-FE temperature was lower than that obtained by the 2D-analytical temperature.…”

“…The size and shape of the heat source are assumed to be an ellipsoidal energy deposition profile centred at the heat source, and decay exponentially with distance in this model. As the shape of the wheel-rail contact area is also elliptical [5,43], Goldak's model therefore is suitable to apply in this study. The mathematical expression of Goldak's model is described as follows [44]:…”

“…On the running surface, the model was finely meshed with the 1 Â 1 mm 2 elements. Since heat penetrates a very thin layer of the contact surface, for instance, 0.113 mm in [43], a much finer mesh of 0.05 mm was generated to capture the change of temperature in the vertical direction, resulting in a total of 56,060 eight-node solid elements and 62,398 nodes. The elastic-plastic-thermal and thermal-isotropic material models [47] were applied to simulate the mechanical and thermal properties of the rail, respectively.…”

Real-Time Measurement of Dynamic Wheel-Rail Contacts Using Ultrasonic Reflectometry

“…Numerical methods have been proposed [3,4] for wheel/rail contact prediction following Kalker's work [5,6]. With the development of computing software, finite element methods (FEMs) have been more and more utilized to simulate static and dynamic wheel/rail contacts in various conditions [7,8]. However, the difficulties in simulating real surfaces with surface roughness and wear evolution put forward doubts as to whether FEM results are accurate.…”