RESIDUAL-STRESS AND ITS CONSEQUENCES ON BOTH SIDES OF THE WHEEL-RAIL INTERFACE

The contact pressures from service loads gradually change the residual stresses in the heads of rails and the rims of wheels from their init ial (as manufactured) distributions as permanent plastic deformation a ccumulates. The resultant state has a near-surface compressive compone nt, aligned with the major live stress, which protects the contact sur face against fatigue propagation of shallow surface cracks unit wear r emoves them. If the contact pressures are high enough, internal residu al tension may develop and promote subsurface fatigue cracking. The fa tigue environment can also be exacerbated by high traction/braking she ar loads or by local heating and thermal stress if the interface is su bjected to high power dissipation. The Federal Railroad Administration sponsors research on problems involving rail and wheel cracks in orde r to foster safer railroad operations, The goal is to establish ration al criteria for load or life limits. The research program development history and major findings are summarized.