Accurate finite element simulation of ductile fracture under large deformations: A damage concept with effective element size

• A hybrid strategy is proposed for simulating ductile fracture under large deformation. • An effective element size concept is proposed to account for element distortion. • Fracture strain is reformulated using stress triaxiality and effective element size. • Arcan tests confirm improved accuracy for crack growth under large deformation. • The model offers a consistent and stable framework for ductile fracture analysis. While strain-based damage models have been widely used to simulate ductile fracture, their predictive accuracy substantially decreases when applied to crack growth accompanied by large deformation. This study systematically identifies the underlying cause of this degradation and proposes a hybrid experimental–numerical strategy incorporating the effective element size concept to overcome it. Through comparative analyses of experiments and finite element simulations, it is demonstrated that the loss of reproducibility originates from significant element distortion near the crack front in high-ductility materials. To address this issue, the effective element size is defined based on the evolving geometry of each element, and the fracture strain is reformulated as a function of both stress triaxiality and effective element size. The proposed strategy enables efficient and robust identification of the required material parameters based on two standard experiments: a tensile test and a crack growth test. Validation using Arcan crack growth experiments confirms that the proposed approach markedly improves predictive accuracy under large deformation conditions, achieving close agreement with experiments even for high-ductility materials. The effective element size concept therefore provides a physically consistent and computationally stable framework for extending strain-based damage models to simulate large-deformation ductile fracture with high fidelity