Contribution to the Modelling of the Tribological Surface Transformations

Abstract

When solids are subjected to tribological loads, structural changes can occur both at the surface and in depth, immediately below the loaded area; in the case of some materials, especially metals, these changes are known as solid-solid phase transformations or Tribological Surface Transformations (TSTs). A thermomechanical model is presented in the present study in order to describe these TSTs. The ability of the model to take account TSTs is assessed with a 2D finite element analysis.

Assessment of Thermomechanical Couplings in Tribological Surface Transformations: Application to the Irreversible Near-Surface Solid-Solid Phase Transformations

“…Note that the thermodynamic consistency of this thermomechanical model was checked in our previous study [6].…”

“…In this Section, it is proposed to assess the effects of the "source" terms on the evolution of the temperature on the emergence and development of TSTs. In our previous study [6], the source terms corresponding to the thermoelasticity, the classical (visco-)plasticity, and the irreversible solid-solid phase transformations were omitted in the first approximation, and in the second approximation, we dealt only with the steady case of the heat equation, that is, Δ .…”

“…Although these source terms (Φ te , Φ pc and Φ pz ) were obtained from a temperature field (see [6]) resulting from the resolution of the heat equation in the steady case, the results obtained in the previous study [6] can be used to assess, in a first approach, the heat sources at any time, as defined by the term on the right-hand side of (3). Note that the physical interpretations associated with each parameter of (3), including their chosen set value, are discussed in [7].…”

“…In this section, the constitutive equations involved in the thermomechanical model for irreversible solid-solid phase transformations [6] are recalled: …”

“…In order to account for the emergence and development of TSTs, it was suggested in a previous study [6] that TSTs result from repeated normal and stress loads, combined with highly localized thermal effects caused by friction between the wheels and rails. It is proposed here to test this assumption, namely that the thermomechanical coupling processes may generate TSTs near the surface of the rails.…”