notch specimen (SEN) and a slant crack in a 3 point bending (3PB) specimen
for isotropic material. For the regular mesh in the SEN specimen both methods
yielded similar results. For the irregular mesh in the 3PB specimen the QPES
methods seemed to be more robust and accurate. Later Guido [33] presented a
method to calculate SIF for anisotropic material using the finite difference method
along an arbitrary crack. Although the model was more robust to irregular meshes
in comparison to interaction integral method, this method was limited to single
edge specimen and corner crack specimen.
Tweed et al. [34] used the specific case of an edge crack of an anisotropic
elastic half space under generalized plane strain conditions to determine the stress
intensity factors using integral transform techniques. Pan and Yuan [35] used single
domain BEM to calculated mixed mode SIFs for both bounded and unbounded 3-D
anisotropic cracked solids. Denda [36] used BEM to determine mixed mode SIFs
(KI, K11 and K111) of 3-D anisotropic material with multiple cracks. It addressed
the issue of coupling effect of the three modes of fracture controlled by Mode I, II
and III SIFs. Though very accurate, these formulations were based on the plane
strain assumption.
Although a substantial body of literature describes computation of SIF, a
generalized numerical solution to calculate SIF for 3-D anisotropic material is
unavailable. The objective of the present work is to model a 3-D orthotropic
specimen having a through crack and to calculate the SIFs for all three modes
assuming linear elastic properties at the crack tip. A mathematical model has been
developed to calculate mixed mode SIF for FCC single crystal orthotropic material
for different orientations, which is also applicable to generalized anisotropic
material. Looking at the crack tip nodal displacements it is possible to calculate
stress intensity factor for any crystallographic orientation of the material. It
was observed that the material orthotropy results in coupled crack tip (x, y,