An experimental study based on the acoustic emission technique was carried out to examine how the axiallity of the stress slate, as first produced by Troiano, influenced the hydrogen cracking kinetics, in terms of delayed hydride cracking (DHC) propagation using constant K specimens machined from Zr- 2.5wt% Nb pressure tube alloy, of’2 mm, 4 mm and 8 mm thickness. By changing the stress slate from plane strain to plane slress at a constant applied stress intensity of 15 MPavm and a hydrogen level of 50 ppm, the DHC Velocity was reduced, in keeping with Troiano’s hypothesis. An explanation of how the observations made on these specimens an be related to other hydrogen cracking mechanisms, is presented.
Keywords: Troiano, hydrogen cracking kinetics. axiallity of stress state, delayed hydride cracking.