PSI - Issue 41

Irina Goryacheva et al. / Procedia Structural Integrity 41 (2022) 220–231 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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process consists of the following stages: the calculation of contact and internal stresses, analysis of the accumulated damage in the surface layer of the material based on the appropriate dependence of the damage function on the internal stress distribution, the calculation of the thickness of the detached fragment, taking into account the chosen material failure criterion, the calculation of accumulated damage at the next step, etc. (Goryacheva, 1998; Goryacheva and Chekina, 1999). At each step of wear modelling, the history of the process is taken into account, i.e. accumulated damage in previous stages. As the main parameters affecting the wear rate, there are contact conditions, macro and microgeometry of the surfaces of contacting bodies, strength properties of materials, residual stresses, etc. Due to the fact that at the dominant number of cases, the contact fatigue is the main cause of the rail failure, the accumulation of contact fatigue damage in wheel/rail contacts is considered in many studies. The review of rolling contact fatigue defects in wheel/rail systems and the mechanisms of their formation is presented in (Magel, 2011). The experimental studies of the influence of relative slippage on the contact fatigue damage accumulation and wear in rolling contact of wheel and rail are described in (Guo et al. , 2016; Pal et al. , 2012; Zhang et al. , 2022; Zhou et al. , 2016). The results of these studies show that the increase of the relative slippage leads to the evolution of the wear mechanism from oxidation wear and local delamination to abrasive wear. In the tests carried out in (Hu et al. , 2020), in addition to the relative slippage, the influence of the ratio of the hardnesses of the wheel and rail materials on the damage accumulation and wear was studied. A method of construction of the contact fatigue damage function accumulated in the material for given loading conditions based on the two-disc testing results was developed in (Hiensch and Burgelman, 2019). The rolling contact problem taking into account the relative slippage was solved there using the FASTSIM (Kalker, 1982) and CONTACT (Kalker, 1990) algorithms. The twin disc tests were conducted in (Santa et al. , 2019) to study the fatigue wear in rails. As a result, the dependences of the wear rate on the relative slippage for wheel and rail were obtained, and several wear regimes were identified depending on the contact conditions. The method for calculation of the accumulated damage in a rail was developed in (Bernal et al. , 2022), taking into account the change in contact characteristics depending on the relative slippage and mechanical properties of the materials of the wheel and rail, measured in the experiments. The results of experiments and field tests, combined with the results of simulation of contact fatigue damage accumulation, can be used for the rail life predictions. The modelling of fatigue damage accumulation in material in rolling with friction of a cylinder over an elastic half space (contact problem in a plane formulation) was carried out in (Goryacheva and Torskaya, 2019), where the effect of the relative slippage, the sliding friction coefficient, and residual stresses on the stress state of the subsurface layers of the contacting bodies was studied. The results of the study show that the presence of residual stresses that occur, for example, in the materials of a rail due to heat treatment of the rail surface, leads to an increase of the principal shear stresses and a decrease of their amplitude values. The results of wear modelling in wheel/rail system in rolling with slippage using the Archard model are presented in (Sakalo et al. , 2019), where the Dang Wang function (Dang Van et al. , 1989), the equivalent Mises stresses and principal shear stresses amplitudes were used in criteria of the material failure. Numerical calculations using the finite element method make it possible to compare the results of wear simulation for different material failure criteria, taking into account the shape of the contact region and the distributions of contact pressure and shear stress. The multiscale finite element model is proposed in (Daves et al. , 2016) to predict the initiation of contact fatigue cracks and the formation of wear particles in the wheel/rail contact under sliding and rolling conditions, taking into account the surface roughness. A review of empirical and analytical approaches for modelling the fatigue damage in rolling bearings is given in (Sadeghi et al. , 2009). In this study, based on a single mechanism for the fatigue damage accumulation in the subsurface layers of materials of interacting bodies, the surface wear and the detachment of material fragments of finite thickness (delamination) of elastic bodies under the conditions of their cyclic interaction with a sliding or rolling ball are modelled. The influence of the sliding friction coefficient (under conditions of full sliding), as well as the sliding friction coefficient and relative slippage (under rolling conditions) on the stress state of subsurface layers of elastic bodies, the accumulation of fatigue damage there, and the kinetics of surface (wear) and subsurface (delamination) fracture in the materials of contacting bodies are studied.