Influence of precracked specimen configuration and starting stress intensity on the stress corrosion cracking of 4340 steel

Experimental results are presented from a study of the effects of precracked specimen configuration and initial starting stress intensity on crack growth rate and threshold stress intensity, for both onset of cracking and crack arrest. Attention is given to AISI 4340 steel in a 3.5-percent NaCl solution, for configurations of a single edge-cracked specimen tested in cantilever bending under constant load, and a modified compact specimen bolt loaded to a constant deflection. The threshold stress intensity value determined was independent of specimen configuration, if the stress intensity value associated with the compact specimen is taken where the discontinuous break occurs in the velocity-stress intensity curve.