CRACK-GROWTH RESISTANCE IN BIMETALLIC WELDMENT

Two types of welded specimens were used in an experiment relating to crack growth behavior near to and in a welding bead, One was cut from a weldment of two A533B steel plates (A533B welded specimen) and the other cut from a weldment of A533B steel with high strength steel HT80 plate (A533B-HT80 welded specimen). In the experiments, the crack growth resistance curves were measured using compact tension specimens. In all of the welded specimens an initial fatigue crack was introduced perpendicularly to the welding bead. In the A533B welded specimen the crack growth resistance curves were measured for the five cases where an initial crack tip was at a position 1 . 5 mm distant from the fusion line; in a heat affected zone (HAZ); at the fusion line; in the weld metal; and in the base metal, Depending on where the crack tip was located, resistance evaluated by J-integral varied in respect to the base metal, the weld metal, the HAZ, and the fusion line. The resistance values for these crack tip locations, however, spread only over a narrow range. This can be explained by the fact that the mechanical properties of the base metal, the weld metal and the HAZ are only slightly different from each other. On the other hand, in the A533B-HT80 specimens, the crack growth resistance was strongly affected by the relative positions of the steels in the specimen and the width ratio of each steel to the specimen, The experimental results are discussed in terms of the stress analysis results obtained by finite elements method (FEM).