%0 Journal Article
%T Assessment of Thermomechanical Couplings in Tribological Surface Transformations: Application to the Irreversible Near-Surface Solid-Solid Phase Transformations
%A Gr¨¦gory Antoni
%J ISRN Tribology
%D 2013
%R 10.5402/2013/525708
%X 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. 1. Introduction The irreversible quasi-surface solid-solid phase transformations known as Tribological Surface Transformations (TSTs), which occur near the surface of rails [1¨C3], are induced by contact fatigue processes [4, 5], occurring after the passing of several trains on the rail tread. 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. 2. A Thermodynamic Framework for Modelling Irreversible Near-Surface Solid-Solid Phase Transformations In this section, the constitutive equations involved in the thermomechanical model for irreversible solid-solid phase transformations [6] are recalled: where is the absolute temperature, is the small-strain tensor, is the elastic strain tensor, (where = ) are the thermoelastic, classical (visco-)plastic and TRIP-like strain tensors, respectively, denotes the metric tensor, denotes the isotropic hardening variable associated with classical (visco-)plasticity,£¿£¿ and are the Lam¨¦ constants, is the thermal expansion coefficient, is the mass fraction of the daughter phase (where is partial mass density of the daughter phase, is total mass density, and is partial mass density of the parent phase (i.e., the ferrite phase)), is a material parameter characterizing the change in the density occurring during phase transformations, is the solid-solid phase transformation temperature when the pressure is zero, is a material parameter characterizing a ¡°sensitive pressure¡± level, is a material parameter characterizing the linear isotropic hardening associated with classical plasticity, is a material parameter associated with the latent heat of the phase transformation (see [7]), is the Cauchy stress tensor, and are the spherical and deviatoric parts of the Cauchy stress tensor, respectively, is the Von Mises equivalent stress, is the classical yield strength, and are the characteristic time of the viscous effects associated with TRIP-like and
%U http://www.hindawi.com/journals/isrn.tribology/2013/525708/