Modelling the effects of friction modifiers on rail corrugation in cornering

A proposed solution to the problem of rail corrugation on curves of urban lines is the use of friction modifiers. Recent experimental research indicates this approach can be effective. This paper makes use of two theoretical models to study the effects of friction modifiers on corrugation in cornering. The first one is a nonlinear time-domain model that predicts corrugation growth from a series of simulated passes of a bogie. The second one is a frequency domain model of wheel-rail interaction, linearised about a steady cornering state, estimated from the nonlinear model. Both models predict reduction of growth of corrugation due to the use of friction modifiers. Friction modifiers can alter the steady cornering state to one with somewhat lower creeps and much lower tractions. Major reductions in corrugation growth rate have been shown to occur if a wheel can be prevented from reaching a state of full sliding when subject to oscillating creeps caused by existing rail corrugation.