A unified material model to predict ratcheting response in head-hardened rail steel due to non-uniform hardness distributions

The non-uniform hardness distribution, metallurgy and ratchetting behaviour of head-hardened Australian rail steel (AS60 HH) are studied. In a bid to extrapolate material properties across the rail head continuum, a unified material model of the rail head has been developed, in which only the hardness of the material is variable. This simplification is shown to enable the material model to reasonably describe ratchetting behaviour across the rail head for heat-treated pearlitic steels. Finally, homogeneous material ratchetting models are used to study the evolution of plastic strain deformation under realistic rail-wheel contact conditions. The results show that non-uniform material properties may compromise ratcheting response with wear progression, thus impacting lifetime of AS60 HH rail steel and re-railing frequency.