EFFECTS OF CRACK SIZE AND WELD METAL MISMATCH ON THE HAZ CLEAVAGE TOUGHNESS OF WIDE PLATES

The heat affect zone (HAZ) is in many cases considered to be the most critical part of a weldment. In this paper, the effect of crack size a nd weld metal mismatch on the HAZ cleavage toughness of wide plate spe cimens with X-groove has been investigated by the J-Q-M theories and a simple micromechanism for cleavage fracture. Two crack sizes have bee n studied (a/w = 0.1 and 0.3). In the analyses, the HAZ yield strength is assumed to be higher than the base metal. For each crack size, wel d metal local overmatch and local evenmatch with respect to the HAZ ar e considered. For a given global strain, the results indicate that wel d metal overmatch and evenmatch yield the same crack tip loading in te rms of J-integral for a/w = 0.3. For a/w = 0.1, overmatch gives lower crack tip loading than evenmatch. For a given crack tip loading, weld metal local evenmatch in general results in less effective crack tip l oading than the overmatch. Overmatch is detrimental to HAZ toughness, but this detrimental effect becomes less significant when the crack si ze decreases. (C) 1997 Elsevier Science Ltd.