Delayed Fracture Mechanism in High Strength Steels by Acoustic Emission Source Wave Analysis

Abstract

Acoustic emission(AE) source characterization was carried out to examine the mechanism of delayed fracture in high strength steels. In static load delayed fracture test, incubation time for crack initiation was observed. Crack initiates at the region of maximum triaxial-stress state. After crack initiation, cracks propagated discontinuously. The diffusible hydrogen content demanded for first intergranular crack initiation was more than that demanded for crack propagation. The AE source characterization showed that the inter-granular crack diameter were 40 to 80μm and crack evolution rata were 30 to 40m/s.