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L. Marsavina et alii, Frattura ed Integrità Strutturale, 34 (2015) 387-396; DOI: 10.3221/IGF-ESIS.34.43 389 with  the shear modulus,  for plane strain,   for plane stress, and  is the Poisson's ratio. Based on SED criterion the crack initiation angle and the relation between K I , K II and K Ic are presented in Tab. 3. Condition Mathematical formulation Crack initiation angle                              2 2 2 sin 2cos 1 2 cos (2cos 1) 2sin sin 6cos 1 0 I I II II K K K K (6)   , , I II Ic F K K K                                            2 2 2 1 1 cos cos 2sin 2cos 1 2 1 1 1 cos 1 cos 3cos 1 c c I c c I II c c c II Ic K K K K K (7) Table 2 : The SED criterion. Table 3 : The Gmax criterion. Condition Mathematical formulation Crack initiation angle                                                                                                          2 2 2 2 2 2 2 2 2 2 3 2 1 6 sin cos 8 cos sin 10 sin cos 1 cos 3 1 4 sin cos (3cos 1) 8 sin cos 9 5cos 1 cos 3 1 1 ln 1 1 I I II II I I II II K K K K K K K K                                                                                                                      1 2 2 2 2 2 2 2 1 1 1 1 1 1 3cos 1 8 sin cos 9 5cos 0 cos 3 I I II II K K K K (9)   , , I II Ic F K K K                                            2 2 2 2 2 2 2 1 1 4 3 cos 1 1 3cos 8 sin cos 9 5cos c c c c c I I II c c c II Ic K K K K K (10)