A Shear‐Deformable Extended Quasi‐Bond Method With Dual‐Mechanism Fracture Criterion for Brittle and Quasi‐Brittle Materials

Although the quasi‐bond method (QBM) provides a promising numerical tool for handling continuous‐discontinuous problems in solid mechanics, it faces inherent limitations including fixed Poisson's ratios and inadequate modeling of mixed‐mode fracture in quasi‐brittle materials due to neglected shear‐softening effects. To overcome these shortcomings, this study proposes an extended quasi‐bond method (EQBM) that integrates bond rotation‐induced shear deformation as an independent kinematic mechanism and introduces a novel dual‐mechanism fracture criterion: (1) a tensile‐shear coupling formulation for brittle materials via an elliptical failure envelope and (2) the explicit shear softening coupled with cohesive zone models at the bond level for quasi‐brittle materials. Computational efficiency is further enhanced through a hybrid FEM/EQBM coupling strategy. Validation across diverse benchmarks confirms EQBM's accuracy in predicting elastic deformation and complex fracture behavior, including mixed‐mode fracture and snap‐back behavior. The results demonstrate the effectiveness of the dual‐mechanism fracture criterion and EQBM's improvements over conventional approaches.