A Novel Framework for Evaluating the Intrinsic Mechanical Properties of Sheet Metals Using Two-dimensional Digital Image Correlation

In this study, we propose a novel method for deriving an extensive true stress-strain curve from uniaxial tensile tests by applying a two-dimensional digital image correlation (DIC) technique. The gauge section of the specimen deforms uniformly within the uniform elongation regime, but in the post-necking non-uniform elongation regime, stress and strain become localized exclusively within the necked section due to plastic instability. Based on the volume constancy condition of plastic deformation, the transverse, axial, and thickness strain components are estimated, enabling the visualization of the evolving cross-sectional area. True stress and true strain over a wide strain range are evaluated by developing a method that encompasses the stress and strain concentrated in the necked section. As a result, the true stress-strain curve over the wide strain range accurately describes the nonlinear hardening behavior over higher strain levels compared to the conventional gauge length method. The accuracy of the proposed approach is validated using finite element method (FEM) simulation. This method offers a straightforward and precise means of obtaining wide range true stress-strain curves through uniaxial tensile tests and two-dimensional DIC equipment, without requiring separate FEM simulations, correction factors, or constitutive equations.

Graphical Abstract