Research Of EMU Wheel’s Fatigue Performance Simulation And Assessment Method

High speed railway can significantly shorten the travel time, so the traffic is veryconvenient for passengers. China already has the capacity of independent R&D andindustrialization production for high-speed railway train, however, EMU wheel, which is thetrain’s key walking component, is currently dependent on imports. The domestic level ofhigh-speed railway train is affected by EMU wheel’s problem in our country. It is of greatsignificance to optimize the allocation of resources, reduction the procurement andmaintenance cost for the research of EMU wheel with our own intellectual property rights.Wheel’s comprehensive performance is concern of wheel material properties, heattreatment process, wheel-rail matching, tread wear, tread damage and other factors. So it’s thekey link of EMU wheel’s independent innovation for fatigue performance simulation andassessment method. The research content includes fatigue strength, wheel heat treatmentresidual stress, wheel-rail contact strength, rim crack propagation life, wheel-rail matchingand so on. The factors that influence the wheel performance need to be analyzed.Combined with the physical properties of the crack initiation and characteristics of web’sstress, the Principal Stress Method and the amendatory Crossland Method which aredescribed the wheel’s strength state with the bending fatigue limit of full scale wheel arepresented here. A new assessment method is formed by combining the Principal StressMethod with the amendatory Crossland Method. The S-N curve and ε-N curve of wheel webare obtained based on testing the wheel’s mechanical properties. Applicability analysis hasbeen contrasted with stress criterion, strain criterion and energy criterion by appling fourtypical EMU wheels.The measurements of key parameters such as forced convection coefficient and latent heatof phase change are given by theoretical analysis and test. Numerical simulation model ofstress field and temperature field has been established for the whole process of heat treatmentof EMU wheel of CRH5. The simulation model’s correctness and reliability have beenverified by comparison with the measured data of temperature and residual stress. Therelationship between heat treatment residual stress and tread lathing amount is first put forward here. The influence of residual stress and tread lathing amount on the web’s fatiguestrength is also analyzed. By analysis, it is been found that heat treatment residual stress canimprove the fatigue life of wheel-rail contact. Taking wheel of CRH5-XP55as an example,the contact fatigue life can increased more than3times under the action of heat treatmentresidual stress.The FE models of fatigue analysis and elastoplastic wheel-rail contact have beenestablished on the basis of measuring the true stress-strain curve and material’s fatigueproperties. The simulation calculation has finsihed by using such FE models. Research showsthat the tread which has a good relationship of wheel-rail contact geometry general also hasgood distribution of wheel-rail contact stress and satisfied contact fatigue performance. LMAtread has the best comprehensive performance through comparing factors such as wheel-railcontact geometry, equivalent conicity, and weak point of contact strength.Wheel web’s shapealso has certain influence on fatigue life of wheel-rail contact, and wheel with low radialstiffness can improve the contact strength to a certain extent.A kind of plastic correction method of stress intensity factor which has been applied toanalysis the rim’s crack damage tolerance is presented here. A calculation method of stressintensity factor basing on analytical solution is put forward here. Arbitrary3D crackpropagation simulation model has been established for the burial type crack in the rim bycombing with the finite element submodel and adaptive meshing technique. Research showsthat the circular patch crack will not grow if its diameter is less than1mm because the stressintensity factor is less than the crack propagation threshold. When the burial type crack isclose to tread surface, the shape of coupling surfaces of crack comes into contact with thecircle. Howerver, when the burial type crack is away from tread surface, their shape comesinto contact with the ellipse and taken long axis as running direction. In the range of EMUaxle load, as the burial type crack grows to a certain size, the effect of tread depth on fatiguecrack growth rate is not significant.