| With the rapid development trend of manufacturing, the cross wedge rolling process, which is a main technology to produce step-shaft forgings, is becoming much more importunately and used widely. The research focuses on the key problems in CWR(cross wedge rolling) at presents, aims to the further understanding on the interior hollow defects and pushing the forward application in practice.By using Deform-3D FEM(finite element method) software, the deformation process in CWR has been simulated, and the material flowing law, strain and stress distribution, temperature field, tools load and the trait of the deformed area has been studied. The analysis of the results between the numerical simulation and photoplastic experiments testifies that FEM simulation is an available method to study CWR process.The influences of temperature, strain rate and stress-strain state on the material plastic in CWR deformation process have been studied. The stress state on the workpiece centre is of two tension stress and one compress stress, while the strain state is of two tension strain and one compress strain. The deformation traits and the comprehensive acting force in the inner workpiece cause the interior defects, but the change of the temperature and strain rate is too little to influence the deformability and to cause the central fracture.Basing on analysis of the existing ductile damage criteria, combined with deformation trait, acting force state, dominant factors of the interior defects, a criteria on the interior defects in CWR process has been selected to describe the development of the interior defects and predict the fracture initiation location With this criteria, the influence of the deforming conditions and the process parameters on inner defects has been simulated, the methods of technics parameters selection and deformation distribution to avoid the center defects have been defined. By using such research results, some problems in practice have been solved well.
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