“…where A is the pre-exponential factor, and a reects the sensitivity of dc/dN to the change of G. 3 Furthermore, Persson and Brener have pointed out that the energy dissipation around the crack G(v) consists of two parts: 4 GðvÞ ¼ G 0 ½1 þ f ðv; TÞ ¼ G 0 þ G 0 f ðv; TÞ ¼ G 0 þ G 0 f ða T vÞ (3) As shown in Fig. 1, G 0 occurs in the innermost area of the crack tip, and it is a highly non-linear process, which includes forming of cavities, breaking of chemical bonds, pulling out of molecular chains and stringing; G 0 f(v, T) is the bulk dissipation of linear viscoelastic region in front of the crack tip, which makes the major contribution to G(v), where f(v, T) is a function of crack growth rate v and temperature T. And according to the time-temperature equivalence principle, T could be replaced by the Williams-Landel-Ferry (WLF) coefficient a T , 5 so that G(v) could be presented as the function of time (frequency) without temperature:…”