Correction of the stress-strain curve in the strained specimens after necking is one of the most practical issues in mechanical engineering. The corrected curve strain-stress is needed to per-form plastic or post-necking analysis in issues related to metals' large deformation. During the specimen's necking, the stress becomes triaxle and includes tangential, radial, and circum-ferential stress components. In the necking area, the stress distribution is ununiformed, and the actual stress is not obtained by dividing the force by the initial section surface. Instead, it is obtained by two different equations before and after necking. In this research, the surface strain method is used on a copper specimen. In the surface strain method, by specifying sev-eral points on the copper rod specimen, the surface strain is obtained at any moment by measuring the distance between these points during the strain test using image-processing analysis. After computing the surface and radial strain, we can calculate the correction factor using the equations, which will give us the corrected actual stress values. The results are veri-fied with the well-known results in the literature as presented by Davidenkov and Bridgham. Meanwhile, the finite element method is employed to perform numerical analysis. The com-mercial software ABAQUS is used to verify the results from image process analysis (IPA). The results show that determining the material model constants using the surface strain meth-od does not require measurement of the necking radius at each moment during testing. Thus, it has relatively more straightforward equations than the Bridgman method and other methods and requires less computation time. Additionally, the experimental and numerical are employed to present the corrected post-necking stress-strain (PNSS) curve.
