Investigation of the reduction in area and twist angle effects on the strain distribution, damage and process load of vortex extrusion die

Vortex extrusion (VE) is a new severe plastic deformation method that simultaneous reduction in area and twisting around the longitudinal axis of the workpiece, within the fixed convergent die, leads to the accumulation of high amounts of strain on the sample. Due to the many capabilities of this process such as creating high strain in a pass, simplicity and no need for complex equipment and homogeneity of strain distribution, in this paper, the simultaneous effect of reduction in area, twist angle and curvature of slip lines on the mean effective strain, maximum damage factor and the steady state load of the process were investigated. The results showed that the mean effective strain value increased with increasing reduction in area and twist angle and there is a significant interaction between mentioned factors. The maximum damage factor was observed at the surface of work piece, which according to the values of positive mean stress in these points it can be said that the possible initiated cracks propagate under tensile state of stress. Reduction in area and twist angle are the effective factors on steady state load of process but the curvature of the slip lines does not have much effect on it. Maximum of damage factor was determined for VE die with curved streamlines, reduction in area equal to 30% and twist angle of 30 degree.