Deformation Behavior Of Inclusions In Steel During Wheel Forming

Wheels play an important role in bearing and guiding during train operation,and are important components to ensure the safe operation of railway trains.The wheel is subjected to rolling contact load during service,and the inclusions on the surface or sub-surface of the wheel rim will induce crack initiation and propagation under the action of cyclic loads,and eventually lead to rim cracks or tread peeling of the wheels,which seriously threatens the running safety of the train.It is of great significance to study the shape and distribution of inclusions in the wheel forming process to improve the wheel forming process and flaw detection process.Due to the disparity in size between the inclusions and the wheel,this paper adopted the cross-scale finite element simulation method to study the deformation of the inclusions during the wheel forming process as a problem occurring between the macro-scale and the micro-scale.The finite element analysis software MSC/Super Form was used to establish the two-dimensional axisymmetric macroscopic model of the wheel preform and the three-dimensional microscopic model with inclusions,respectively,by simulating the inclusions at different positions,inclusions with different deformation resistance and inclusions in billets of different specifications,the parameters of inclusion migration path,deformation shape of inclusion and equivalent strain of inclusion and nearby matrix during wheel forming were studied.The main research contents and conclusions are as follows:(1)The wheel forming and inclusion deformation were modeled and analyzed by body cell method at macro and micro scales respectively,the key to connect the two scale models is to transfer the element node information of the macro model to the body cell model.The body cell method was applied to simulate the deformation behavior of a specific inclusions in wheel,the accuracy of simulation results was verified by comparing the results of inclusion simulation with those of inclusion evaluation by fatigue method.(2)The particle tracking method was used to study the metal flow paths at different positions of the billet,and the corresponding relationship between the inclusions distribution in the wheel and the inclusions in the billet was obtained.The micro-body cell model of inclusions at different positions was further established for calculation,and the deformation shape of inclusions at different positions and equivalent strain distribution law of inclusions and their surroundings were obtained.Inspection from the direction perpendicular to the largest dimension is helpful for the identification of the size of the inclusions.(3)Different relative deformation resistance ratiosλ(λ=σ_i/σ_m,whereσ_iis the flow stress of inclusion;σ_mis the flow stress of the matrix)was used to establish the inclusion model with different deformation resistance for calculation.It was found that the deformation degree of inclusions is negatively correlated with the relative deformation resistanceλ,the soft inclusions deform in coordination with the wheel matrix,while the deformation degree of the hard inclusions is very small.intense strain concentration occurs at the interface between the hard inclusions and the matrix,which is an important reason for the initiation of cracks.(4)ComparingΦ380 mm andΦ450 mm billet metal flow law and the distribution of inclusions after forming,further established two cell models of inclusions with different specifications,and obtained the deformed shape of inclusions in different specifications and the distribution law of equivalent strain of inclusions and their adjacent matrix,to study the effect of billet size on the wheel forming process.