Comparison of numerical and computational aspects between two constraint-based contact methods in the description of wheel/rail contacts

Xinxin Yu,José L. Escalona,Pasi Korkealaakso,Marko K. Matikainen,Dezhi Jiang,Asko Rouvinen,Javier F. Aceituno,Emil Kurvinen,Aki Mikkola

doi:10.1007/s11044-022-09811-6

Abstract

The numerical and computation aspects of the Knife-edge Equivalent Contact (KEC) constraint and lookup table (LUT) methods are compared in this paper. The LUT method implementation uses a penetration-based elastic contact model for the flange and a constraint-based formulation at the wheel tread. For the KEC method, where an infinitely narrow rail contacts an equivalent wheel, regularization of the tread-flange transition is adopted to simultaneously account for tread and flange contacts using constraints. A comparison between the two methods is carried out using well-known numerical integrators to show the applicability and limitations of both methods.Two fixed-step-size integrators, the explicit Runge–Kutta (RK4) and the predictor–corrector Adam–Bashforth–Moulton (ABM) methods, and two variable-step-size Matlab built-in function integrators, the explicit ode45 and implicit ode15s, were applied to get the numerical solutions to the dynamic problems and study the relative numerical performance of the two contact description methods. To complete the railway vehicle model, both contact methods were implemented for the multibody model of a benchmark railway vehicle (the Manchester wagon 1). Numerical results were obtained for different railway tracks with and without irregularities. Profiles of the S1002 wheel and LB-140-Area rail, which demonstrate the two-point contact phenomenon, were considered. Both methods were implemented in Matlab and validated against commercial simulation software. The kinematic results for both approaches show good agreement, but the KEC method was up to 20% more efficient than the LUT method regardless of integrator used.

Highlights

A railway vehicle is a complex mechanical system that consists of a large number of bodies, wheel/rail contacts, and complicated suspension elements
The differences between each approach can be summarized as follows: 1. Contact detection for the LUT method is based on an offline approach where the contact points are determined by interpolating a predefined lookup table
The Knife-edge Equivalent Contact (KEC) method is an online contact detection approach where the exact position of the contact points can be determined from the online solution of the KEC constraints

Summary

Introduction

A railway vehicle is a complex mechanical system that consists of a large number of bodies, wheel/rail contacts, and complicated suspension elements. A number of formalisms have been introduced to analyze wheel/rail contact. The first is the elastic approach [5,6,7], where interpenetration between wheel/rail surfaces is allowed, and normal contact forces are computed based on interpenetration and Hertzian parameters. In [8], Liu and Bruni compared Hertzian and non-Hertzian wheel/rail contact models for multibody simulation. In [6], the Hertzian and non-Hertzian models are studied and compared to give the insight of proper selection of the parameters for better computational accuracy and efficiency. The second approach is the constraint method, which is called Lagrange multiplier method In this approach, the contact between wheel and rail is described with a set of kinematic constraint equations [9]

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