DETERMINATION OF THE THRESHOLD . STRESS INTENSITY FACTOR (K_(Iscc)) OF 4340 STEEL USING SMALL CIRCUMFERENTIAL NOTCHED TENSILE (CNT) SPECIMENS

摘要

A novel fracture mechanics technique has been employed for the determination of threshold stress intensity factor (K_(Iscc)) for stress corrosion cracking (SCC) using small circumferential notch tensile (CNT) specimens. The technique was applied successfully for testing SCC susceptibility of heat treated 4340 steel in 3.5% sodium chloride solutions at room temperature. The K_(Iscc) has been determined to be 15 MPa.m~(1/0), which is very close to K_(Iscc) values obtained by others using standard specimens. The fracture surfaces have been examined by scanning electron microscopy (SEM) in order to identify the evidence of chloride stress corrosion cracks.