Identification of Post-necking Tensile Stress-Strain Behavior of Steel Sheet: An Experimental Investigation Using Digital Image Correlation Technique

The stress-strain behavior of sheet metal is commonly evaluated by tensile test. However, the true stress-strain curve is restricted up to uniform elongation of the material. Usually, after the uniform elongation of the material the true stress-strain is obtained by extrapolation. The present work demonstrates a procedure to find out the true tensile stress-strain curve of the steel sheet after necking using digital image correlation (DIC) technique. Hill's normal anisotropic yield criteria and local strains measured by DIC technique are used to correct the local stress and strain states at the diffuse necked area. The proposed procedure is shown to successfully determine the true tensile stress-strain curve of ferritic and dual-phase steel sheets after necking/uniform elongation.