Advances in ultrasonic flaw detection

Ultrasonic flaw detection enables the detection of all the defects inside metallic components, and also estimates their dimensions. The length of the pulse, injected by an ultrasonic transducer is so short, that even defects close together can be resolved (a resolution of one mm requires a pulse length below 5 cycles at a frequency of 4 MHz). The paper reviews recent research on ultrasonic testing at the CEGB Non-Destructive Testing Applications Center. Attention is given to probe characteristics, details of the test method, and limitations to sensitivity and accuracy. Two applications are mentioned: an 'in-service' inspection technique for austenitic welds, previously thought inaccessible to ultrasonic testing, and the automation of routine weld inspection on a larger scale in connection with the Dinorwic Pumped-Storage Scheme. Future developments will rely on digital data recording, promising more sophisticated forms of analysis.