An extended shear-modified GTN model based on the void failure mechanism of localized shear band

Abstract

Most existing shear-modified Gurson-Tvergaard-Needleman (GTN) models are primarily based on phenomenological observations or empirical assumptions, rather than fundamental failure mechanisms. Consequently, they exhibit limited accuracy in predicting ductile fracture under complicated tensile and shear stress state. To address this limitation, this study presents an extended shear-modified GTN (ESMGTN) model, which incorporates the void evolution mechanism within localized shear bands. The ESMGTN model is formulated through theoretical derivation and implemented numerically for integration into finite element software. A user-defined material (UMAT) subroutine is developed using the backward Euler integration algorithm and a consistent tangent modulus. The role of void failure mechanisms in localized shear bands is investigated by analyzing the variation of a correction coefficient derived from a unit cell model. To validate the model’s predictive capability, experiments are conducted on Q960 high-strength steel specimens subjected to various stress states. Monotonic loading tests are performed on notched flat-plate specimens, rectangular notch specimens, and shear specimens. The numerical results closely match the experimental data, yielding a mean absolute error of 5% in fracture prediction. Finally, the effectiveness of the ESMGTN model is further demonstrated through comparisons with existing models and external experimental results.