THE INFLUENCE OF WELD STRENGTH MISMATCH ON CRACK-TIP CONSTRAINT IN SINGLE-EDGE NOTCH BEND SPECIMENS

Previous work by Dodds and Anderson provides a framework to quantify f inite size and crack depth-effects on cleavage fracture toughness when failure occurs at deformation levels where J no longer uniquely descr ibes the state of stresses and strains in the vicinity of the crack ti p. Size effects on cleavage fracture are quantified by defining a valu e termed J(SSY) : the J to which an infinite body must be loaded to ac hieve the same likelihood of cleavage fracture as in a finite body. In weld metal fracture toughness testing, mismatch between weld metal an d baseplate strength can alter deformation patterns, which complicate size and crack depth effects on cleavage fracture toughness. This stud y demonstrates that there is virtually no effect of +/-20 percent mism atch on J(SSY) if the distance from the crack tip to the weld/plate in terface (L(min)) exceeds 5 mm. At higher levels of overmatch (50 to 10 0%), it is no longer possible to parameterize the departure of J(SSY) for a weldment from that for a homogeneous SE(B) based on L(min) alone . Weld geometry significantly influences the accuracy with which J(SSY ) for a welded SE(B) can be approximated by J(SSY) for a homogeneous s pecimen at these extreme overmatch levels.