مهدی شبان غازانی

Equal channel angular pressing is the most effective and promising severe plastic deformation technique and has the ability to produce ultrafine grained and nanostructured materials. Different parameters has an influence the homogeneity of the plastic strain distribution in processed sample which in turn affects the mechanical properties of the sample. In the present investigation the effect of double curvatures, made in the inner and outer regions of the intersecting area of channels, on the plastic deformation distribution in sample, has been investigated using two dimensional finite element analysis. The curvature radiuses are considered in the range of 0-10 mm. It was concluded that the strain distribution is affected by the curvature radius. Based on the strain variations across the sample three regions were identified. It was demonstrated that the extent of upper and lower non-uniform regions is increased with the increase of curvature radius. But for the uniform plastic region the inverse trend was identified. The homogeneity of plastic strain distribution decreased with the increase of the curvature radius. The damage factor distribution inside deformed sample indicated that the cracks may be initiated from the inner regions of sample as the Craft-Latham damage factor is higher at these regions compared with the near surface area. It was also demonstrated that the magnitude of damage factor decreases with increasing the curvature radius in the inner regions. This is in contrast with the variation of the maximum damage factor with curvature radius when it is appeared in the bottom side of the sample. The strain rate patter was used to determine the shape of deforming zone. It was concluded that the defaming zone is more localized when the curvature radius is small. Increasing the curvature radius makes the deforming zone to be separated into two adjacent regions. This was demonstrated by analyzing the variations of equivalent plastic strain and strain rate wi