Effect of localised cyclic heating on railway wheel steels - an investigation into the effects of tread braking

Abstract

The treads of a number of railway wheels which had seen service on passenger trains in Australia are examined. Four damage patterns are observed on these treads, with each being associated with a particular wheel/rail or wheel/brake interaction. Tread braking, which is associated with the formation of hot spots and crack arrays, appears most dangerous to wheel life. An experimental apparatus capable of simulating the thermal cycles experienced in tread braking is constructed. Crack growth occurs two orders of magnitude faster in simulation of hot-spot cycles compared to general tread cycles. Such acceleration of crack growth is only observed when repeated phase transformations occur during the hot-spot cycles. Other forms of damage associated with hot-spot simulations are detailed and the effect of cycle frequency on damage forms are investigated. The possibility that damage accumulation may be associated with transformational plasticity is discussed. Show more