Determination of the Equivalent Stress-Equivalent Plastic Strain Curve of ECAP-Processed Copper

An axisymmetric tensile specimen was prepared using copper produced through the equal channel angular pressing (ECAP) process, which is a type of severe plastic deformation process. By intentionally reducing the center diameter of the specimen to be slightly smaller than the diameter of other gauge portions, necking was consistently induced at the specimen center in both experiments and finite element analyses (FEA). When the force-elongation curve simulated through the iterative FEA reasonably coincided with the experimental counterpart, the equivalent stress- equivalent plastic strain (EP SS) curve inputted into the FEA was extracted as the physical property of the specimen. During the iteration process, the curve mentioned was directly corrected using a stress correction equation (without assuming a constitutive equation) before each FEA. The EP SS curve extracted as the physical property differs significantly from the true stress-true plastic strain curve obtained through the conventional method. This finding highlights the significance and rewards of accurately measuring the properties of a material manufactured through a severe plastic deformation process, like an ECAP process, using a meticulous procedure, as demonstrated here.