Digital Twin Framework for Characterizing Postnecking Strain Localization in Copper Using DIC-FEM

Accurate prediction of strain localization and postnecking behavior is critical for understanding failure in ductile metals such as copper. Traditional tensile testing methods based on engineering stress–strain curves and extensometer readings often fail to capture localized deformation phenomena, especially beyond the onset of necking. In this study, digital image correlation (DIC) and finite element modeling (FEM) are used to investigate the deformation and damage behavior of pure copper dogbone specimens under quasi-static uniaxial tension. Full-field strain measurements obtained via two-dimensional digital image correlation (2D-DIC) enable detailed visualization of the strain localization process. The finite element (FE) simulations are used to qualitatively and quantitatively validate the experimental results. The FEM framework incorporates isotropic plasticity and a ductile damage model with fracture energy–based regularization to ensure mesh objectivity. We assess the model’s predictive capabilities by comparing force–displacement curves, axial strain fields, and localization zone morphology with the experimental observations. The effect of mesh refinement is examined using multiple element sizes (2, 1, and 0.5 mm), demonstrating convergence in both global and local metrics. Strain map comparisons between DIC and FEM reveal good agreement in the necking position and shape, although peak axial strain values differ due to differences in strain definitions and spatial resolution. This coupled DIC-FEM approach provides an experimentally validated framework for modeling postnecking behavior in copper, with implications for ductile damage calibration and microelectronic reliability applications. The results also serve as a reference dataset for future multiscale and inverse identification efforts in strain-localized regimes.