Hybrid Crack Elements for Three-Dimensional Solids and Plate Bending.

Abstract

Abstract : Special crack front elements have been developed and have been assembled into superelements for direct evaluation of stress intensity factors K(I), K(II), and K(III) of arbitrarily shaped three-dimensional cracks. The formulation is based on the assumed stress hybrid finite element model. The assumption of stresses and boundary displacements contains asymptotically exact terms. The stress-free condition over the crack surface and the displacement compatibility across interelement boundaries are completely satisfied. The superelements are compatible with most existing finite element computer programs. Numerical results for commonly used fracture test specimens (single edge crack specimen, center crack specimen, double edge crack specimen and compact tension specimen), an embedded penny-shaped crack, a semi-circular surface flaw, and a quarter-circular corner flaw are presented. A superelement has been developed directly for the analysis of bending and shearing stress intensity factors, K(B) and K(S), of thin plates with a through-the-thickness crack subjected to out of plane bending. The particular approach is also based on the hybrid element concept, for which the assumed stresses satisfy both equilibrium and compatibility conditions. Poisson-Kirchhoff's thin plate theory and the complex variable technique are used.