High pressure torsion testing of the wheel/rail interface

The traction characteristics between wheel and rail have a significant effect on the behaviour of a railway vehicle; as a result it is important to be able to incorporate a representative traction model in vehicle multibody dynamics (MBD) simulations. Initially MBD software packages used a single value to represent traction in the interface; more recently, Kalker's FASTSIM has introduced a simple creep curve into simulations. FASTSIM, attempts to describe the traction curve up to a saturation point, treating traction as constant beyond saturation. VIRTUAL VEHICLE Research Centre has developed an Extended Creep Force (ECF) model to better represent traction forces under a wider range of conditions. Frictional properties of the third body layer between wheel and rail are required inputs into the ECF model, previously the model has been developed using preliminary data from another source with limited success; at the University of Sheffield a new test rig is under development to provide reliable data to input into the ECF model. Commissioning tests have been run to validate the design of the rig, the test procedure and assess the repeatability of results. So far the commissioning process has highlighted and resolved issues with the specimen design, the progression method used, and the assumptions used to calculate the creep stress throughout the test. A run-in procedure has also been developed to improve the consistency of results produced.