75kg/m Heavy Rail Straightening Deformation Mechanism And Residual Stress Control

The railway is one of the foundations of the national economy,and the steel rail is the basis for the safe and reliable operation of the railway.Heavy-duty and high-speed are the main development direction of China's future railway transportation.Therefore,higher requirements have been given to the straightness and residual stress of high-speed railway rails.There are many factors that affect the straightness and residual stress of the rail.As the last finishing process in the rail production process,straightening has a key impact on the residual stress and straightness of the rail after straightening.In this paper,through the analysis of the law of stress changes in the process of rail straightening,the research is focused on reducing residual stress and improving straightness.Based on the elastoplastic theory and the principle of straightening,this article uses Soildworks 3D modeling software to establish a 75 kg / m rail nine-roller straightening model,and uses the Explicit display dynamics solution module in ABAQUS to simulate and analyze the straightening process.Model,firstly,through the numerical simulation calculation of the two material models of the material's isotropic strengthening model and the following strengthening model under the same initial conditions and straightening rules,the longitudinal residual stress changes and straightening during the straightening process are analyzed.Differences in the distribution of post-longitudinal residual stress;Secondly,the numerical simulation calculation of rails in different initial states under the same straightening procedure was carried out,and the post-straightening residual stress and straightness of the rail in different initial bending directions and with or without initial stress were analyzed.The effect of the impact on the elastic core of each straightening deformation zone is analyzed by the simulation calculation of the rails in the same initial state using different straightening procedures,and the size of the elastic core on the residual stress and straightness after straightening is studied.Relationship.Through numerical simulation calculations,it can be concluded that the maximum longitudinal tensile and compressive stress of the isotropic strengthening model in each straightening deformation zone is greater than the follow-up strengthening model.The isotropic strengthening model is closer to the experimentally measured residual stress of the rail.The addition of the initial longitudinal stress increases the longitudinal residual stress of the rail head and the bottom of the rail after straightening by 126 MPa and 42 MPa,and increases the longitudinal residual stress of the rail head and bottom of the rail after bending by 47 MPa and 52 MPa.The addition of initial longitudinal stress also improves the straightness of the rail after straightening.The analysis of the calculation results of the reduction of different straightening procedures shows that the 2 # procedure(22-12-9-7)is the optimal straightening procedure,and the reason for this is the reduction of the second reduction roller R4 It plays an important role in the amount of longitudinal residual stress on the bottom of the rail after straightening.The idea of optimizing the straightening procedure should be that it is only possible to reduce the amount of reduction under the condition of ensuring straightness of R4 reduction.The research results of this paper can provide theoretical basis and reference opinions for the optimization of rail straightening regulations.