Tribological Surface Transformations (TSTs), which are irreversible near-surface solid-solid phase transformations, tend to occur on railroads frequented by heavy freight trains. The present study is proposed to assess the contribution of thermomechanical coupling processes to the emergence and development of TSTs near the surface of the rails.

The irreversible quasi-surface solid-solid phase transformations known as Tribological Surface Transformations (TSTs), which occur near the surface of rails [

In this section, the constitutive equations involved in the thermomechanical model for irreversible solid-solid phase transformations [

Based on the assumption that TSTs are induced by “strong” thermomechanical coupling—the combined effects of the temperature and mechanical processes—the heat equation can be written as follows (see [

Note that the thermodynamic consistency of this thermomechanical model was checked in our previous study [

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 [

However, the orders of magnitude of these terms can be assessed, a posteriori, and compared. In the incremental form, the full heat equation (

Although these source terms (

Figure ^{3} (10 mm × 2.5 mm × 1 mm) in the immediate vicinity of the surface where the thermomechanical loading is applied, the power dissipation of the heat sources caused by the thermoelastic and classical (visco-)plastic processes and the irreversible solid-solid phase transformation coupling is approximately 425.10^{−3} W, whereas the power of the internal stresses is only of 145.10^{−3} W. On the other hand, the power dissipation of the heat source due the thermoelastic effects alone is approximately 402.10^{−3} W. It can be seen here that under the boundary conditions defined in [

Heat sources due to the thermoelastic and classical (visco-)plastic processes and the irreversible solid-solid phase transformations (unit: MPa·s^{−1} or mW·mm^{−3}) at time

Power of the internal stresses (unit: MPa·s^{−1} or mW·mm^{−3}) at time

Heat source due to the thermoelastic processes alone (unit: MPa·s^{−1} or mW·mm^{−3}) at time

In order to estimate the thermoelastic coupling effects, it is proposed to take a 1-D thermoelastic problem, that of a bar in steel (occupying a domain

Geometry (

Assuming

The local expression of First Principle of Thermodynamics (FPT) is:

Combining

Using (

The Heat Equation (

Assuming that both inertial and gravity effects are nonpresent, the local expression of quasi-static equilibrium can be reduced to:

Based on (

Thermomechanical loading applied (on the left end of the bar,

Figure

(a) Temperature distribution in the bar at time

The results obtained in this section show that the source term due to the thermoelasticity is responsible for a variably marked increase in the temperature increase near the end of the bar and throughout the bar, but that the thermomechanical loading conditions considered here (see Figure

This paper deals with the contribution of thermomechanical coupling processes to the emergence and development of irreversible near-surface solid-solid phase transformations. Based on the results obtained here, the thermoelastic effects can be said to predominate over the effects of the other thermomechanical heat source resulting from classical (visco-)plasticity and irreversible solid-solid transformations. Although these source terms cause the temperature to increase at the surface and in the depth of the structure, it emerges clearly from this study that the thermomechanical loads applied constitute the main driving force responsible for generating TSTs.

The author is indebted to Dr. Jessica Blanc for her help with this paper.