Finite Fracture Mechanics: a deeper investigation on negative T-stress effects

Abstract

In the present work, the coupled stress and energy criterion of Finite Fracture Mechanics (FFM) is applied to investigate negative T-stress effects related to mixed-mode brittle fracture of cracked elements. Only two material parameters are involved in the analysis, the tensile strength and the fracture toughness, which are independent of the mode-mixity. Below a critical T-value, the shear contribution to the strain energy release rate (ERR) starts to prevail in the mode II-dominated zone. This affects FFM results in terms of: (1) the fracture loci, with the critical mode II-stress intensity factor (SIF) never exceeding the fracture toughness; (2) the critical kinking angle and the actual crack advance (which results to be a structural parameter), both decreasing to infinitesimal quantities as mode II-loading conditions are approached. These predictions can be revised by considering a large amount of energy dissipated under mode II loading conditions and by assuming a mode-mixity dependent ERR. A discussion on experimental data for brittle and quasi-brittle materials available in the literature is included.