most suitable for cracks of relatively small dimensions. The method was verified
by calculating SIFs for isotropic material and comparing the results with readily
available formulas given in Tada et al. [26], which resulted in excellent agreement.
Sun et al. [27] used the boundary element method (BEM) to analyze cracked
anisotropic bodies under anti-plane shear. The new boundary formulation used
dislocation density as an unknown on the crack surface, and K111 was determined
near the crack tip. The equation and method could be directly used for anti-plane
problems with cracks of any geometric shapes. It did not give a complete solution
under mixed-mode loading conditions, but it did give an idea about the behavior of
K111 under anti-plane shear loading.
Shih et al. [24] have calculated SIFs for 2-D isotropic materials using quarter
point element nodal displacements at the crack tip based on Finite Element
Method (FEM). The Modes I, II and III have been decoupled because of the
isotropic nature of the material. Sih et al. [28] defined SIFs as a function of
stress at the crack tip. Following the work of Shih et al., Ingraffea and Manu
[29] showed how to compute SIF from 3-D quarter point nodal displacement, for
cracked isotropic elastic bodies for all three modes. They used a quarter point
isoparametric element, which has been accurate in computing SIF [30]. Saouma
and Sikiotis [31] introduced anisotropy in the above model [29] and proposed a
method to calculate SIF for 3-D anisotropic elastic material based on the model
of Shih et al. The computed SIFs, when compared with 2-D anisotropic bodies
with known exact solutions yielded an error of 6-1'-. for K, and K11. However the
orientation of the elastic constants was not incorporated. The expression of K111
was not correct as it resulted in almost zero value, irrespective of the geometry,
orientation and the load applied to an anisotropic component.
Dhondt [32] analyzed two methods, interaction integral method (IINT) and
the quarter point element stress method (QPES), to calculate SIF for single edge