The sizes of planar defects in the butt welded joints of a high tensile steel were measured by ultrasonic testing with a point focussed angle probe, and the results were related to the fatigue and corrosion fatigue life predictions for the joints containing those defects. Surface and buried lack of penetration, and pear-shaped bead hot crack were artificially made in the welded joints by the control of gas metal arc welding conditions. The fatigue and corrosion fatigue life curves for the defective specimens were predicted by fracture mechanics technique using the fatigue crack growth data of weld metal measured in air and those of base metal in saltwater reported previously. Reasonably close agreement between the predicted and observed values was obtained for both the cases in fatigue and corrosion fatigue, and hence it was concluded that sufficiently accurate fatigue and corrosion fatigue life predictions would be possible provided the defect shape was detected with the accuracy of about ±1 mm as was done in this study.
