Influence of strength matching and crack depth on fracture toughness of welded joints

In the present paper, fracture toughness for the specimen of welded joints with different strength matching and crack depth is investigated by finite element computer simulation and a fracture mechanics test. This investigation focuses especially on the effects of strength matching and crack depth on the triaxial stress state at a crack tip, crack tip opening displacement (CTOD), and J-integral fracture toughness. The results show that there exists the fracture toughness peak (FTP) in the curve of fracture toughness vs crack depth. The location of the fracture toughness peak is influenced by the yield strength for a homogeneous material, and it is also influenced by the strength matching for welded joint. The increase in the strength of weld metal could be of benefit to the fracture-resistant property of the weld metal, if the toughness of the weld metal is similar to the parent metal.