Fracture toughness evaluation of 316LN stainless steel and weld using acoustic emission technique

Fracture toughness behaviors of 316LN stainless steel (SS) base metal and weld were investigated using Acoustic emission (AE) technique. Four point direct current potential drop (DCPD) method has been used to measure the crack initiation and extension, aiming at generating evidence for determination of the point of crack initiation by AE methods. Fracture toughness Q values were estimated using AE characteristics with simultaneous ASTM standard E1820. The results in this investigation showed that 316LN SS weld exhibited lower fracture toughness than that of base metal. The points of crack initiation in 316LN SS base metal and weld could be characterized by the first peak of cumulative energy rate, the sudden increase of AE cumulative energy, counts or amplitude coupled with peak amplitude signals. The fracture toughness values of 316LN SS base metal and weld estimated using AE technique were lower than those obtained by ASTM procedure.