Research On Fast Prediction Method Of Wheel-rail Rolling Contact Fatigue Based On Shakedown Map And Potential Function

Due to the increase of train axle load and the acceleration of operation speed,the problem of wheel-rail rolling contact fatigue damage occurred during the operation of the train,and the rail fatigue cracks occurred frequently on the service rails,resulting in frequent replacement of a large number of rails,which brought huge economic losses to the country.Therefore,it is necessary to carry out theoretical and simulation research on the fatigue damage of service rails.The shakedown map proposed by Professor Johnson can intuitively and quickly compare the safety of wheel and rail under different operating conditions,and qualitatively analyze the occurrence mechanism and possibility of wheel-rail rolling contact fatigue damage.Aiming at the shortcomings of the existing shakedown map,this paper proposes a shakedown map that is more suitable for the actual operation of the railway track system,and establishes a fast prediction method for wheel-rail rolling contact fatigue life based on shakedown map and potential function.The main research contents and conclusions are as follows:(1)The research status of wheel-rail rolling contact fatigue at home and abroad is introduced in detail,and the fatigue life prediction method and model are described in detail from the two aspects of engineering application and scientific research,and the significance of studying wheel-rail rolling contact fatigue damage is also clarified.The author chooses the fatigue life prediction model and method required in this paper.(2)The theoretical method of wheel-rail contact and the numerical model established in this paper are introduced,including the method for solving the mechanical behavior of rolling contact at the wheel-rail interface,the method for solving the stress-strain field in the wheelrail contact body,and the establishment of a two-dimensional rail local finite element model and the material cycle constitutive model used.(3)Based on the shortcomings of the existing shakedown map,a shakedown map that is more suitable for the actual situation of the railway track system is proposed.The concept of saturation is introduced to consider any creep state,and the shakedown map with friction coefficients f = 0.2 and f = 0.4 are made.The stress-strain analysis is carried out on the calculation results of the working conditions from the three aspects of friction coefficient,maximum contact pressure and saturation,which is found that the local material response of the rail will significantly affect changes in the residual stress,the residual strain and surface displacement.The maximum contact pressure has a significant effect on the residual strain of the thin-layer material on the rail surface.The saturation will affect the generation position of the maximum residual stress and the maximum residual strain,the residual strain of the thinlayer material on the rail surface,and the longitudinal displacement change of the rail surface.(4)A fast prediction method of wheel-rail rolling contact fatigue life based on shakedown map and potential function is proposed.The local material response of the rail is determined by the shakedown map,and then the corresponding fatigue life prediction model is determined.The stress-strain field solution method based on the potential function is used to calculate the stress and strain in the rail body under the condition of wheel-rail contact,and combined with the critical plane method,the maximum fatigue damage parameters and the fatigue life prediction value are obtained.The fatigue life prediction results of the proposed prediction method and the finite element method are compared and analyzed in terms of accuracy and prediction time.The local material response of the rail will significantly affect the maximum value of the wheel-rail contact fatigue damage parameter and the predicted value of fatigue life.Because of the influence of friction coefficient,the maximum contact pressure and saturation,the prediction results of fatigue life of the two methods are quite consistent,and the error rate is within 15%.In the comparison of prediction time consumption,the proposed prediction method takes less time,which is 3-4 orders of magnitude different from the finite element method,which reduces the calculation cost from hours to seconds,and greatly improves the calculation efficiency.