Wheel-Rail Contact Modelling for Locomotive Traction Control System Studies

Recent locomotive traction studies have been extensively focused on the development of wheel-rail contact models for application inside multibody software products to compute results which can be further used in the prediction of track damage indexes. These models are quite sufficient, but they have a significant disadvantage of slow computational speed. In order to use the same locomotive models for traction studies, a new concept of the model was studied. The main difference from existing models is the developed normal task approach that provides a transition from non-Hertzian to Hertzian contact patches and this innovation was validated against the results obtained in a parallel computation test implemented inside of the wheel-rail coupling based on the Extended Contact library. The test was performed with a multibody locomotive model running on tangent track. The first implementation of the developed wheel rail-coupling has been tested in a parallel mode with the Extended Contact library on a full mechatronic model of a locomotive and the results compared against each other. Discussion on the further development is provided.

Contact modelling of highly heterogeneous friction material for braking applications

Friction brakes are increasingly undergoing considerable development to improve their durability, efficiency, maintenance costs and environmental impact. Nevertheless, to achieve this, it is necessary to understand the different mechanisms involved in contact that are multi-scale and multi-physical in nature. On the multi-scale aspect, it is well known experimentally that heterogeneities have a pre-weighted role on performance without being able to explain it. Thus, modelling seems to be a good way to better understand the influence of these heterogeneities, provided that we have a multi-scale method to consider them. The objective of this article is therefore to propose a methodology for simulating contact in the presence of heterogeneous materials. The strategy consists in enriching the contact rigidity in terms of behaviour by a method of numerical homogenization. The significant advance of this article lies in the consideration of contact within the technique of numerical homogenization of a heterogeneous material. The strategy is then validated by comparing the mechanical fields between the proposed method and an explicitly meshed case. One of the main contributions of this work is the reduction in computing time compared to the traditional FEM method.

General directions in contact modelling development

This paper presents a survey of works, selected from the period of the last twenty years, on deformations in the contact between rough surfaces. All the selected works use FEM. They deal with the modelling of individual contact asperities or the use of experiment to verify contact models. First, research directions connected with the modelling of single asperities, whose shape is usually approximated with that of a hemisphere or a half cylinder, are presented. Section 3 discusses research directions concerning models which include the layer under asperities, and models for small contact surfaces (about 1 mm2). Section 4 reviews directions in contact modelling which takes into account neighbouring asperities and laterally loaded asperities. Section 5 discusses directions in the development of models and experiments used or suitable for verifying models. Finally, conclusions concerning accurate contact deformation modelling are presented.