Mixed mode stress intensity factors for elliptical subsurface cracks in an elastic half-space subjected to a uniform normal loading

摘要

An elliptical subsurface crack under normal loading may experience mixed fracture modes due to the non-symmetrical geometry. This paper investigates the coupling of the modes of elliptical subsurface cracks subjected to a uniform normal loading. First, a three-dimensional finite element model of a crack in an infinite space has been developed and validated. Then, by moving the crack close to surface, mixed mode SIFs have been calculated for a wide range of elliptical subsurface cracks under uniform normal loading. Cracks with aspect ratios of 0.2-1.0 and ratios of crack depth to crack length from 0.05 to infinity have been investigated through 50 finite element analyses. In this range, K_(Ⅱ)/K_Ⅰ and K_(Ⅲ)/K_I ratios increase up to 68.9% and 9.4%, respectively. Three equations for mode Ⅰ, Ⅱ and Ⅲ SIFs have been obtained by fitting to the finite element results. These equations can be used efficiently as reference SIFs for extracting the weight functions.