Rail friction modification benefits assessed by vehicle dynamic simulation

Previous field studies of wheel rail noise, wear and top of rail lubrication practice have been conducted using instrumented rails and selected rollingstock, often with hand applied friction modification compounds to test alternative operations. Such studies are limited to selected test curves and selected vehicle bogie types that are of primary concern. Even if train operations allow sufficient track and vehicle possession time, testing is limited by the time required to apply the friction modifiers. Using vehicle simulation it is possible to test a wide variety of curvatures, curve designs and bogie types, as well as variable wheel rail profiles and friction conditions providing curving performance measures such as wear indices and lateral rail head forces. This paper reviews the paper from CORE 2004 ‘Control of Wheel/Rail Noise and Forces Through Friction Modification’ with studies conducted by the CRE (Centre for Railway Engineering) using vehicle dynamics software VAMPIRE®. The study was conducted by CRE on behalf of QR as a part of the Train Dynamics Management Program. The results agree with field measurements that rail head friction modification produces considerable benefits in wear reduction on very tight curvatures. The further simulations on medium and gentle curves, however, show the benefits from top-of-rail friction modification are small for medium and gentle curves, and the benefits are dependent on the passive steering features of the bogie and the wheel-rail profile and flange friction conditions. The paper presents the results of several different conditions of curvature, and wheel rail profile conicity. These results are discussed in view of developing guidelines for effective placement of friction modifier compounds.