Combined elastoplastic finite element method and tensile test for flow characterization of representative cold forging materials and their flow patterns

A combined elastoplastic finite element method and tensile test (EP-CF&T) for flow characterization of a carbon steel at room temperature and large strains is presented. This novel method acquires the flow curve in the post-necking strain-hardening (PostSH) region from a cylindrical tensile test, accounting for springback during elastoplastic deformation in this region. A general scheme is proposed for obtaining the optimized EP-CF&T flow curve, starting from the initial flow curve obtained by combining the rigid-plastic finite element method (RP-FEM) and tensile test (RP-CF&T). In the dual flow characterization approach, the initial RP-CF&T flow curve is iteratively improved by the optimized elastic deformation correction function during the EP-CF&T. In enhancing this flow curve and evaluating the results, the necking point and the Considère condition are essential touchstones. An application example demonstrates that the EP-CF&T is a numerically robust and practical method for obtaining an accurate flow curve, which can accurately predict the tensile test using the elastoplastic finite element method (EP-FEM). The average fracture load error at the necking points of the seven materials is 0.21%. The usefulness of the presented EP-CF&T is verified by applying it to representative forgeable materials. The strain-hardening rate (SHR) is used to reveal the characteristics of the flow functions and classify flow patterns into six categories.