Crack initiation time determined by tapered round specimens

In order to ascertain the contribution of crack nucleation process in fracture, round tapered specimens of 304 stainless steel were used to determine the initiation time of stress corrosion cracking in boiling 42% MgCl₂ solution. The results showed that the relation of the time to nucleation of stress corrosion cracking (SCC) to the applied stress obeyed t_i=4310_exp(-0.0097δ); however, the relation of the time to fracture to the applied stress was t_f=6964_exp(-0.0095δ). It was indicated that the majority of fracture process consisted of crack initiation. The fracture surface was related to the applied stress. The transgranular SCC area decreased with the increase in applied stress.