1984 Volume 2 Issue 3 Pages 447-454
Fracture toughness of welds has been usually evaluated, based on COD tests developed for homogeneous material. However, since mechanical heterogeneity caused inevitably in welds considerably influences crack opening behaviour, critical COD calculated according to the conventional method does not necessarily represent an appropriate fracture toughness parameter of material in the vicinity of crack tip.
In the present study, at first, "Local COD criterion" has been proposed newly as an appropriate fracture criterion of welds with mechanical heterogeneity. In order to clarify the availability of the new criterion, bending COD tests and tensile tests of notched-welded plate have been conducted, using specimens extracted from undermatched and evenmatched weld joints of HT80 steel. FEM analyses have been also conducted in order to characterize the deformation behaviours of these specimens.
From the experiments and analyses, in the welded joints with notch existing along fusion line, Local COD δL defined newly in our study is proved to control strains in the vicinity of crack tip, and :applicability of Local COD δL as an appropriate fracture characteristic parameter is clarified. Moreover, it is suggested that fracture performance of welded joints with mechanical heterogeneity should be evaluated, based on Local COD criterion proposed in the presnnt study.