Lawrence, Potter, Teo
Additional Information - Posters # 1998 Gothenburg
When butt welds fail in servicc it is normal to find that the initiation site of the fracture occurs at the point where the roll bead attaches to the main body of the pipe. The ratio of hoop stress to longitudinal stress for 'thin walled' pipe is approximately 2 : 1 and so it is more likely that these transverse service failures result from the combined effect of the service load and extraneous third party loading. Attempts to measure the behaviour of welds by using il~temal pressurisation are frustrated by this inherent load ratio, but still further by the fact that the weld bead provides additional circumferential reinforcement. If an attempt is made to accelerate the failure process by applying high internal pressurisation the saniple fails in the body of the pipe and not at the weld. This paper describes how dynamic loading has heen applied to both a pressurised and non-pressurised system to cause failure to occur at the weld beadlpipe wall interface in a way and with a fracture morphology analogous to that seen in service.
