Fracture toughness of defective welded joints and acoustic emission

Abstract

The effects of welding defects on acoustic emission behavior and critical J integral of SS41 mild steel shielded metal-arc welded joint are studied. Three kinds of artifical welding defects of through-thickness crack-like defect, center machined notch and double edge machined notch are made in tensile specimen and the specimen is tested under plane stress condition. The through-thickness crack-like defects showed larger acoustic emission activity than the other machined notches. This may be caused by conjunction and rubbing of a intricate tip of the through-thickness crack-like defect. However the double edge notch showed acoustic emission events of higher energy compared to the other defects because of a significant stress elevation ahead of the notch in double edge notched specimens. Critical J integral was largely affected by shape and size of welding defects, especially through-thickness crack-like defect reduced the critical J integram markedly. Critical J integral calculated on a crack initiation point defined by acoustic emission is found to be lower than that calculated on a crack initiation point defined by multiple specimen interrupted loading methods.