Identification of post-necking stress–strain curve for sheet metals by inverse method

• A method for extrapolating the flow curves of sheet metals is presented.
• The flow curves of mild steel, HSLA steel and aluminum alloy are identified.
• The original Hockett–Sherby function is modified by adding a linear term.
• Various functions are evaluated for approximating the flow curves.

Simulation of sheet metal forming requires the flow curve (i.e. the true stress–strain relation) over large strains. This paper presents a method for obtaining the flow curve of sheet metals over a large range of strain through the combination of simple tensile test and finite element analyses. The appropriate finite element model for accurate simulation of the anisotropic plastic deformation during diffuse necking was determined. Different hardening functions were evaluated for their capabilities in approximating the entire flow stress curves up to localized necking. A modified Hockett–Sherby function was proposed and its performance was demonstrated.

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