Irwin's solution; anisotropic; crack

Hi everyone,

      We know that crack or wedge problems are discussed in the porlar coordinate system which centered at the crack tip. Analytical solution (Irwin's) in an expanding form with unkown constants exist for crack or wedges with any open angle in isoptropic materials. The analytical solutions are always employed as enrichments in FEM, MM, XFEM. When the problem moves to anisotropic materials, does the analytcial solution exist?