Investigation of Effective Plastic Strain Heterogeneity and the Effect of Using Interface Sheet in Constrained Groove Pressing of Copper Sheet

The constrained groove pressing process is one of the most effective methods of severe plastic deformation to produce very fine-grained sheet metal. Numerical simulation is performed in several steps by finite element software in such a way that the output result of each step, which is strain-hardened, is used as the input of the next step. The finite element results of the obtained plastic effective strain distribution show that the strain changes along the longitudinal direction of the sample are oscillating. The relevant results also show that in the direction of thickness, the amount of strain in the middle of the sample is maximum and as it moves away from the center of the sample, the amount of strain decreases. In addition, the results of strain heterogeneity show that the strain heterogeneity factor in the longitudinal direction is 2.8 times the corresponding value in the thickness direction whereas the average plastic strain in the two directions differs only about 13.4%. Then, to improve the strain uniformity, steel sheets are placed at the top and bottom of the sample as interface sheets, and then the constrained groove pressing is applied. Using this method, it is observed that the degree of strain homogeneity in the first stage is improved compared to the conventional method of the constrained groove pressing process. By using this method, it can be seen that the amount of strain heterogeneity factor is reduced from 6.85 to 2 in the first stage.