Keywords: railway, train-structure interaction, wheel-rail contact, contact forces, creepages.

The running safety analysis of railway vehicles during earthquakes is one of the major concerns in railway engineering. Hence, in order to evaluate such safety, it is necessary to develop a suitable model which takes into account the wheel-rail contact and enables the contact force computation in all directions. This type of contact contains some specifications, especially arising from the particular geometry of the wheel and the rail, and arising from the rolling friction contact between these two bodies which, unlike the sliding friction Coulomb model, permits the existence of a contact area with both adhesion and slip. This type of rolling contact has been extensively studied, but it was Kalker [1] who first developed an exact theory to solve this type of problem.

In the present research, a wheel-rail contact point search algorithm is presented for the construction of a lookup table to be later used on a railroad dynamic code. Such a procedure is important to make the dynamic analysis less demanding in terms of computation time, since the contact characteristics are pre-calculated offline and linearly interpolated during the analysis. Several authors [2,3] proved the efficiency of this procedure, concluding that an offline search of the contact points could be ten times faster than an online calculation.

The proposed algorithm allows for not only the identification of the location of the contact point, but also all the geometric characteristics of both wheel and rail in that same point, namely the curvatures of both bodies and instantaneous rolling radius of the wheel, among others, necessary for the creepage computation during the dynamic analysis. The proposed algorithm is valid for two and three dimensional calculations, making it suitable not only for straight tracks, but also for situations where the wheelset yaw angle can have a significant influence in the final results. All the results were properly validated using specialized commercial software tested on a benchmark that took place in the Manchester Metropolitan University [4,5].

The present investigation also accounts for the implementation of two well-known rolling contact algorithms, FASTSIM [6] and USETAB [7]. The results obtained with such algorithms were validated with the commercial software Contact which solves the rolling contact problem using Kalker's exact theory. Although the results were satisfactory, one of the routines, the Usetab, was modified in order to improve its accuracy.

1

J.J. Kalker, "The computation of three-dimensional rolling contact with dry friction", International Journal for Numerical Methods in Engineering, 14(9), 1293-1307, 1979. doi:10.1002/nme.1620140904

2

M. Bozzone, E. Pennestri, P. Salvini, "A compliance based method for wheel-rail contact analysis", in "8th International Conference on Contact Mechanics and Wear of Rail/Wheel Systems", Firenze, Italy, September 15-18, 2009.

3

J. Santamaria, E.G. Vadillo, J. Gómez, "A comprehensive method for the elastic calculation of the two-point wheel-rail contact", Vehicle System Dynamics, 44(1), 240-250, 2006. doi:10.1080/00423110600870337

4

P. Shackleton, S. Iwnicki, "Wheel-Rail Contact Benchmark Report", Version 3.0, Manchester Metropolitan University, Manchester, U.K., 2006.

5

P. Shackleton, S. Iwnicki, "Comparison of wheel-rail contact codes for railway vehicle simulation: an introduction to the Manchester Contact Benchmark and initial results", Vehicle System Dynamics, 46(1), 129-149, 2008. doi:10.1080/00423110701790749

6

J.J. Kalker, "A fast algorithm for the simplified theory of rolling contact", Vehicle System Dynamics, 11(1), 1-13, 1982. doi:10.1080/00423118208968684

7

J.J. Kalker, "Book of tables for the Hertzian creep-force law", in I. Zobory, (Editor), "Proceedings of the 2nd Mini Conference on Contact Mechanics and Wear of Wheel/Rail Systems", Budapest, Hungary, 1996.

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £110 +P&P)