Numerical analysis of cross wedge rolling process for small cross-sectional shrinkage shaft Sun Guanghui, Xin Xuanrong，Chen Xuewen (College of Materials, Henan University of Science and Technology，Luoyang 471003, China)

Abstract: The cross wedge rolling process of small cross-sectional shrinkage shaft was simulated by software Deform, and the regulation of stress-strain was obtained. The result indicates that the main forming of the small cross-sectional shrinkage shaft occurs on the stretching section. The triaxial stress of the workpiece is compressive stress in contact with the die area, and the compressive stress value is large. However, the transversal stress of the workpiece is tensile stress in the central region of the workpiece, and its value is about 25 MPa. Furthermore, the axial stress is tensile stress and its value is about 35 MPa, and it is easy to produce shrinkage and cracks. Then, the ellipse appears in the small crosssectional shrinkage shaft, and its ellipticity is up to 2.28%. The deformation of shafts is found to produce mainly around the outer of shafts by the metal flow analysis. In different crosssections, the farther distance is the cross section from the symmetric cross section, the greater is the axial displacement. P1,P2,P3,P4 are selected in the end face of the workpiece, P4 axial displacement at the outer layer of the workpiece is large and P1 axial displacement at the heart of workpiece is small, which cause concave core in the workpiece easily. 
Key words: cross wedge rolling；elliptical；metal flow；concave core