TWI Industrial Member Report Summary 255/1984
By R H Leggatt
The second phase of an investigation of the effects of test panel restraint on critical crack tip opening displacement (CTOD) values has been completed. The parent plate was 40mm thick BS 4360 Grade 50D. The weld preparation was a symmetrical double-V with 60° included angle. The welds were made using AWS 7018 electrodes, and the root pass was not removed. The panels were restrained either by strongbacks, end bars, or by a massive external rig. The normal sequence of welding was to complete one side before filling the second side, but one panel was welded using a balanced sequence of passes on opposite sides of the joint. Measurements were made of transverse shrinkage and weld distortion in all panels. Most CTOD and Charpy specimens were tested at -1O°C, but CTOD specimens from one panel were tested at -20°C and Charpy specimens from the same panel were used to provide impact energy temperature transition curves. As in the first phase, CTOD values in each panel were scattered; this scatter was reduced at -20°C. The heavy restraint provided by the external rig did not significantly affect the CTOD values. The lowest critical CTOD values were found in the panel welded using a balanced welding sequence. There was evidence of reduced critical CTOD values in the vicinity of tack welds in the root. A standard configuration for test panel restraint fixtures is proposed.