Mechanical Analysis And Ellipticity Control Research On The Cross Wedge Rolling Process Of Rail Vehicle Axles

With the vigorous development of China’s rail transportation industry,axles are the key components of trains,and their demand is increasing day by day.Cross wedge rolling is a new process and new technology of axle forming,compared with the traditional parts forming process,cross wedge rolling process has the advantages of high production efficiency,high material utilization,low production cost,easy to realize automation,etc.,and is widely used in the manufacture of shaft parts.In this paper,the RE2 B axle formed by cross wedge rolling is taken as the research object,and the constitutive equation of the rolling material is established by the strain compensation method.Improve the level of mold design by means of parametric modeling,rolling theory and mold emptying;The force energy parameters of the rolling process were solved by finite element simulation and theoretical calculation methods.Based on the process optimization system platform,the prediction model of ovality after rolling was established,and the influence factor of dimensionless influence factor on ovality was analyzed.The research results provide theoretical support for reducing the force and energy parameters of the rolling process,improving the roundness quality of the axle after rolling,and realizing the safe production and automatic control of the cross wedge rolling process.The main research contents of this paper are as follows:(1)Under different deformation conditions,the hot compression experiment of the axle material can obtain the engineering stress-strain data of Q345,and the real stress-strain data can be obtained through data processing.The parameters of Q345 carbon steel at strain 0.9 are solved,and the constitutive equation based on this strain is established.Considering the influence of the strain term,the constitutive equation for strain compensation is established by combining the Zparameter and the Arrhenius type equation.The mean square correlation coefficient and mean relative error of the predicted value and experimental value of the constitutive model are 0.98826 and 5.092%,respectively,which effectively verify that the Arrhenius type equation has high accuracy.The research results lay the foundation for the theoretical calculation of subsequent force energy parameters.(2)Take the RE2 B axle as the research object,and design a reasonable mold according to its engineering drawings.Following the requirements of different mold wedge stages in the mold design process,a parametric model based on RE2 B axle mold is established by means of parametric design,which avoids the repetitive work of designing the same type of mold.On the basis of the parametric design mold,in view of the problem of spiral steps during axle rolling,the design of the transition section is completed by the principle of rolling.In view of the problem of poor stress state during axle rolling,the mold was reasonably designed by emptying.(3)Under the condition of emptying and non-emptying,the numerical analysis of the cross wedge rolling process is carried out by the finite element method,and the value and change trend of the force energy parameters are obtained,and the mold emptying is conducive to reducing the value of the force energy parameters in the case of small section shrinkage.The theoretical calculation method is used to calculate the numerical calculation of the stable rolling broadening stage under the emptying of the cross wedge rolling die,and the mathematical unified expression between the rolling process parameters and the force energy parameters is obtained.The relative error of the calculation results of the stable rolling broadening section of the simulation calculation method and the theoretical calculation method are within a reasonable range,which effectively verifies the consistency of the calculation results of the two.(4)In order to improve the quality of the ellipcicity of the axle after rolling and realize the control of the ovality of the rolled parts,a process optimization system based on the simulation platform is proposed.The reasons for the ovality of the rolled parts are analyzed,and the cross-section corresponding to the wedge area of the rolled parts is used as the research object.Based on the rolling process optimization system platform,finite element calculation was carried out,a large amount of rolling data was collected,the ellipcicity after rolling of the axle was taken as the goal,the rolling process parameters were used as variables,the prediction model of the ovality after rolling was established,and the influence factor of dimensionless influence factor on ovality was analyzed,and the research results provided a basis for improving the quality of ovality after rolling.