The Numerical Simulation Of Micro Shaft’s Cross Wedge Rolling And Study Of Workpiece’s Internal Damage

Cross wedge rolling is a new kind of axle parts forming technology in recent years,this technology has played more and more important role in the forging industry becauseof high efficiency, economizing material, without cutting the fibers, long service life of thedie and easy to implement mechanization, etc. Currently, China has hundreds of crosswedge rolling production lines and hundreds of cross wedge rolling products.Among themost cross wedge rolling products, mainly related to ordinary solid shafts, hollow shaftsand large shafts and so on. Nowadays, we have meet the situation of which used the crosswedge rolling technology to produce micro shafts rarely. Therefore, it is necessary for usto discuss cross wedge rolling of the micro shafts in this paper, and it will lay a foundationfor the practical application.At the begin of this paper,the material model, the friction model and numericalsimulation model of the micro shaft’s cross wedge rolling has been established. By usingDeform-3D FEM (finite element method) software, the three-dimensional thermalcoupling deformation process in micro shaft’s CWR has been dynamic simulated.Through tracking the point of the micro shafts to observe the changes of theirs internaldisplacement and velocity field, and to grasp the material flowing law completely in thedeformation process of the micro shaft’s CWR.Secondly, by analyzing the deformation mechanism of the micro shaft’s CWR, thefeasibility of using the cross wedge rolling technology to produce micro shafts has beenexplored. The cloud of equivalent strain and equivalent stress, the stress-strain curve of themicro shaft’s internal characteristic points, the trait of the strain rate field and the changeof the temperature field has been analyzed. Prediction of mold’s rolling force, andsimulated micro shaft’s cross wedge rolling process at the normal temperature, and make acomparative with the situation of800°C, come to the conclusion that800°C rolling issuperior to normal temperature rolling. And then studied the internal force of micro shaft’salternating times and analyzed the impact generated by its interior defects.Finally, basing on analysis of the existing ductile damage criteria, combined with the CWR’s deformation trait, acting force state, dominant factors of the interior defects, a newcriteria on the interior defects in CWR process has been selected to describe thedevelopment of the interior defects and predict the fracture initiation location. Use theOyane criteria to simulate the cross wedge rolling process is superior to Normalized C&Lcriteria and better to reflect the position of the interior defects, especially suitable forthree-roll cross wedge rolling. In order to determine a reasonable simulation parameters,the influence of the deforming conditions and the process parameters on interior defectshas been analyzed, the methods of technics parameters selection to avoid the interiordefects has been defined.