Characterization of crack tip stress fields In test specimens using mode mixity parameters

摘要

The aim of this study is to represent the combined effect of mode mixity, specimen geometry and relative crack length on the T-stress, elastic-plastic stress fields, integration constant I_n, angle of initial crack extension, and the plastic stress intensity factor. The analytical and numerical results are obtained for the complete range of mixed modes of loading between mode I and mode II. For comparison purposes, the reference fields for plane mixed-mode problems governing the asymptotic behavior of the stresses and strains at the crack tip are developed in a power law elastic-plastic material. For the common experimental fracture mechanics specimen geometries considered, the numerical constant of the plastic stress field I_n and the T-stress distributions are obtained as a function of the dimensionless crack length and mode mixity. A method is also suggested for calculating the plastic stress intensity factor for any mixed-mode I/II loading based on the T-stress and power law solutions. It is further demonstrated that in both plane stress and the plane strain, the plastic stress intensity factor can be used to characterize the crack tip stress fields for a variety of specimen geometries and different mixed-mode loading. The applicability of the plastic stress intensity factor to analysis of the in-plane and out-of-plane constraint effect is also discussed.