By maintaining the positioning of micro-crack with respect to semi-infinite crack and varying the orientation of this micro-crack around itself, Figures 13-16 represents the effect of the micro-crack on the strain energy and the propagation of semi-infinite crack. Table 2, groups the zones of amplification and reduction of semi-infinite crack Table 2 Amplification and reduction zones of propagation of semi-infinite crack according to the orientation of micro-crack around itself