| With the rapid development of economy and society, railway transport system in China has presented a trend of high-speed passenger service and the heavy cargo service. The factors of higher speed, heavier transportation volume and axle-weight will lead a more complex wheel-rail contact relations. The thermal damage generated by wheel-rail sliding contact can cause fatigue and wear, such as corrugation, spalling and crazing. Drastic vibrations and noises occur with the fatigue and wear, which will directly endanger the train safety and severely degrade the riding comfort. Therefore, it is meaningful and valuable in theory and engineering application to study the thermo-mechanically coupled effect of wheel-rail sliding contact for further understanding the mechanism of wheel-rail thermal damage, wheel-rail material selecting, rail designing and maintenance. Therefore, the contact characteristic of wheel and 60kg/m rail is studied in detail. According to the characteristic of wheel-rail interaction, based on the theory of friction, elastic-plastic mechanics, contact mechanics, and heat transfer theory, the fields of the contact stress, temperature and stress in wheel and rail are numerically analyzed by using finite element software ABAQUS.1) The main contants of the thesis are summarized as below:The thermo-mechanically coupled cyclic constitutive model was improved based on the finite deformation theory. Considering the temperature-dependent evolution laws of isotropic and kinematic hardening and thermal balance equation, the plastic dissipated heat, and the interaction between temperature and stress field, user subroutine of ABAQUS was used to implement the model. The improved model was proved to be reasonable by comparing with the existed experiments.2) The 2D contact finite element model was created by ABAQUS based on the Hertz elastic contact theory. The influence of axle-weight on the contact pressure in the rail’s surface was investigated by applying a static load to the 2D model. The theory resolution and finite-element solution of temperature rise in the rail’s surface was obtained and the influence of peak load, plastic dissipation heat, heat transfer on the contact pressure was revealed based on the thermo-mechanically coupled elastic contact. The solution and finite element analysis results show that:Hertz contact theory is accurate to calculate the contact pressure on the elastic condition. With the increase of the axle-weight, the maximum value of contact pressure increases and the semi-axis length of the contact spot elongates on the conditions of the elastic wheel-rail bearing static load and the elastic-plastic sliding contact of wheel-rail considering thermal-stress coupled effect. The coefficients of plastic dissipation heat and heat transfer are negligibly small in the condition of the elastic contact subjecting to a static load and the elastic-plastic sliding contact considering thermo-mechanically coupled effect.3) The stress and temperature field of wheel and rail with different conditions of sliding contact are numerically investigated. Based on the simulations, the influences of axle-weight, train speed, friction coefficient, sliding distance, dissipation coefficient, convection coefficient and radiation coefficient on the stress and temperature field were discussed. The results show that the maximum value of temperature rise is located at the rail surface in all conditions. Axle-weight and friction coefficient are two factors affecting the temperature rise in the rail surface most, train speed and radiation coefficient are the second most influence factors, and the factors of sliding distance, dissipation coefficient and convection coefficient can be negligible. With the increase of the axle-weight and friction coefficient, the temperature rise in the rail surface increases. The maximum value of von Mises equivalent stress locates the subsurface of the rail in all conditions, which moves from the subsurface to the surface with the increasing friction coefficient. |
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