Numerical Simulation of Thermal-Structural and Stress States in the Process of Hardening Railway Rails

The manufacture of high-strength railroad rails is an extremely important issue. It necessitates the development of such methods for numerical analysis of thermal-structural and stress states of rails in the process of hardening that can be used to rationalize rail manufacturing processes. A mathematical model is created that can describe temperature fields, distribution patterns and thermal stresses in a rail during the entire hardening process. The finite element method is used as the basis for solving the nonlinear nonstationary problem of heat conduction and thermo-elastic-plasticity. Boundary conditions of the third kind are used to describe the heat transfer. Modelling of the transformation of austenite into ferrite-carbide in isothermal conditions is carried out using the Avrami equation.  The transition from the isothermal kinetics of austenite decomposition to the non-isothermal conditions is described by the theory of isokinetic reactions applying the additivity rule. The calculation results of the temperatures, structures and stresses in a railway rail at different stages of hardening are presented. It is shown that the head of the R65 rail after hardening has the structure of lamellar ferrite-carbide. When quenched in oil, martensite is present only in the structure of the neck and near the rail foot blade. The software developed by the authors can be used to predict the strength of the rail during operation.

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