A phenomenological modelling with thermo-mechanical coupling for Tribological Surface Transformations (TSTs)

On a New Kinetic Modelling Approach of the Irreversible Quasi-Surface Metallurgical Phase Transformations

“…(viii) In line with the first kinetic model (Section 2.2), the thermodynamic admissibility of the model developed here can also be confirmed [7,10,22] by simply checking whether the Clausius-Duhem inequality is satisfied [20,21].…”

“…It is worth pointing out that the temperature increase in a wheel/rail problem may range from few degrees to hundred degrees Celsius or even more (see [46][47][48][49] for more details). The nonlocal kinetic model presented here can therefore account for the high localized thermomechanical fields occurring near and in the immediate vicinity of the contact zone and thus predict more accurately than the previous model the irreversible solid/solid phase transformations occurring just under the rail surface [8,10].…”

“…The gradient model presented in (10) belongs to a class of rate-dependent models for the inelastic behavior of materials. The inelastic behaviour investigated here obeys a viscoplastic law of Perzyna type [40,41].…”

“…In line with [42], a linear coupling of the local and nonlocal terms associated with the metallurgical variable is introduced here (see (12)). During transformations of this kind, a hardening process occurs [7], which is simulated here by the term 1 where 1 denotes the linear isotropic hardening coefficient (which is a dimension of a stress) [8,10]. In the nonlocal term 2 ∇ , an intrinsic characteristic length parameter can be introduced into the gradient coefficient 2 so that 2 = 0 .…”

“…In metallurgical phase transformations of this kind, which often occur in the rails of straight railway sections [1,2] and those frequented by heavy freight trains, the ferrite/pearlite phase is directly transformed into a martensite phase [3]. To account for this process, it does not suffice to take only the thermal history of the material into account like in the standard metallurgical phase transformations [4][5][6], but both the thermal and the mechanical histories have to be taken into consideration when modelling these irreversible metallurgical transformations because high combined thermomechanical loads are engendered in the wheel-rail contact area, in the presence of strong normal and tangential stresses possibility in addition to a significant increase in the temperature due to the friction process occurring in the contact area [7][8][9][10]. In a previous study [11], a kinetic model was presented and discussed for predicting the onset and development of these irreversible quasi-surface solid/solid transformations in the materials subjected to high localized thermomechanical loads applied near the surface.…”