Computational analysis of effect of route on strain uniformity in equal channel angular extrusion

The effect of route method (A, BC, BA, C) on strain uniformity after multi-pressing by ECAP (equal channel angular pressing) to the same workpiece (up to four passes) was examined in 3D using a commercial FVM code capable of dealing with very large plastic deformation. Strain uniformity could be evaluated by using particle tracking method and measuring strain distribution on the cross sectional and longitudinal planes of the workpieces. Average of total strain accumulated up to four passes was independent of the route method but strain uniformity largely depended on the route method. By using BA and A routes, strain uniformity could not be achieved anywhere in the workpiece, whereas it could be obtained to the reasonable level in the steady strain region near the center of the workpiece after every four passes in BC route and after every two passes in C route. Among the four routes investigated, the route C yields the best result in strain uniformity. Effect of route method on the strain distribution on the cross sectional area could be explained based on the result of particle tracking mode. The maximum strains measured near the sharp die corner in route A and BA after four passes are very close to the values predicted by the theoretical analysis based on ideal shear deformation, while those measured at other positions and in other routes (BC and C) is less than the theoretical value.