THE RELATIONSHIP BETWEEN CTOD, J AND MICROSTRUCTURE INHOMOGENEITY

The fracture behavior of two types of welds with microstructural inhom ogeneity is discussed using the concept of the specific energy gamma(p k). The relationship between the macroscopic fracture parameters, e.g. CTOD and J-integral, and the microstructural inhomogeneity is obtaine d. It is found that the crack growth resistance in welds depends mainl y on the degree of the microstructural inhomogeneity including the siz e and distribution of the various zones. When the local brittle zone ( LBZ) in welds exists at the crack front, the crack initiation toughnes s and the crack growth resistance are greatly reduced. The larger the thickness of this zone or the more brittle the LBZ is, the lower the f racture toughness of the whole weld. Experimental results show that th e specific energy method can be used to evaluate the fracture behaviou r of the weld metal under dynamic loading.