Abstract
This paper proposes a new way of considering wheel–rail contact in multibody systems simulation that goes beyond the traditional planar constraint and elastic approaches. In this approach, wheel–rail interaction is modelled as a force element with pressures and shear stresses distributed over a contact area that may be curved, supporting conformal contact situations. This by-passes the selection of the contact reference location and reference angle, which are delicate aspects of planar contact approaches.The idea is worked out introducing the curved reference surface as the new backbone for the computations, instead of the tangent plane used previously in planar contact approaches. The steps are described by which the curved reference is constructed in CONTACT, using generic facilities for markers, grids, and coordinate transformations, by which generic wheel/rail configurations can be analyzed in a fully automated way.Numerical results show the capabilities of the new method for measured, worn profiles, suppressing discontinuities in the forces when multiple contact patches split or merge. A further application concerns the evaluation of strategies used in planar contact approaches. There we find that the tangent plane’s inclination is of the biggest importance. This should be defined in an averaged way to achieve maximum correspondence to the more detailed curved contact approach.
Highlights
The development of efficient, stable, and accurate models that account for wheel–rail contact is of great interest for vehicle developers in the industry, for vehicle operators and infrastructure managers and for researchers
In a separate paper [26], we presented the analysis of contact geometry using the planar contact approach
This paper addressed the role of the tangent plane in the planar contact approach –defining the normal and tangential directions needed for the undeformed distance, creepage, pressures, and slip– and discussed the complications in its definition, prior to the calculations, and using a single inclination to approximate the entire contact
Summary
The development of efficient, stable, and accurate models that account for wheel–rail contact is of great interest for vehicle developers in the industry, for vehicle operators and infrastructure managers and for researchers. In the implementation of a force element for multibody system dynamics, the wheel–rail contact problem is generally divided into three consecutive stages [2, 8,9,10,11,12]: (1) the contact geometry stage, identifying the contact location and corresponding tangent plane; (2) the kinematic stage, determining the undeformed distance and the creepages, i.e. the relative motion of wheel and rail surfaces, at the contact position; and (3) the contact mechanics stage, computing the resultant normal and tangential forces. Acknowledging that contact arises on a contact area with finite extensions, a distributed force element may be considered for the solution of the contact problem This lets us account for the local, distributed kinematics of the problem rather than using approximate values obtained from a single contact location, and defines the actions on the wheel and rail by the contact stresses, as shown in Fig. 2 (c), rather than using the contact forces as the central concept.
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