Issue 35

S. El Kabir et alii, Frattura ed Integrità Strutturale, 35 (2016) 64-73; DOI: 10.3221/IGF-ESIS.35.08 71 Tab. 1 shows the stable crack growth zones for various new size parameters. The lengths are proportional to size parameter and greater for G 1 than for G 2 . Figure 8 : Normalized elastic energy release rate G 1 and G 2 versus mixed mode ratio for various thickness parameters 3 1 1 1 3 1 1 1; ; and (a), for and (b), for and (c) 4 2 2 2 4 2 2 b a a b a b             . Comparison between G 1 and G 2 shows that the opening mode needs 10 times more energy than the shear mode. Thickness parameter b Stable zone G1 (mm) Stable zone G2 (mm) 1 [27:41] [46.5:57] 0.75 [27:41] [46.5:57] 0.5 [27:41] [46.5:57] 0.25 [27:41] [46.5:57] Table 2 : Stable crack growth zone for different size parameter and 1 2 a  .