Process zone resolution by extended finite elements

A new numerical technique for the computational resolution of highly localized strains in narrow damage process zones of quasibrittle materials is proposed. Objective description of localization due to softening is provided by a nonlocal damage model. The extended finite element method is exploited for an adaptive enrichment of the standard displacement approximation by regularized Heaviside functions that are close to the exact localization mode. An accurate closed-form expression for the width of the enriched zone is derived by localization analysis under uniaxial stress. Numerical examples show that satisfactory results can be obtained even on coarse basic meshes with only a few added degrees of freedom.