Development and implementation of a membrane-coupled conformable array transducer for use in the nuclear industry

Rolls-Royce, in collaboration with Imperial College, London, has developed a membrane-coupled phased array device and full matrix capture (FMC) inspection capability. Together, these tools can be used to deliver improved ultrasonic inspections on components with irregular surface geometries. This paper will provide details of the membrane-coupled device design and its usage as part of an automated inspection capability. Details of the FMC data processing software are provided in another paper: 'Ultrasonic phased array inspection using full matrix capture'([1]). The membrane-coupled device utilises inexpensive, off-the-shelf array technology. Ultrasonic energy from the array is coupled into the component under test via a water path, which is encapsulated in a low-loss polyurethane membrane. The membrane material is acoustically matched to water and is sufficiently robust and flexible for scanning welded components with undressed convex weld caps, typical of those found in the nuclear industry. The membrane-coupled device concept is very versatile; linear and twin-crystal devices have now been developed and are reported here. The performance of the membrane-coupled device's inspection capability is demonstrated through the detection of a range of challenging defects within a welded stainless steel component. The results demonstrate that all of the reported defects within the component are readily detected using the membrane-coupled device, but that the inspection performance using conventional ultrasonic techniques with the weld cap in place is severely degraded. The completion of phased array inspection utilising FMC data also provides significant improvements in inspection speed, versatility and accuracy that cannot be achieved using conventional techniques.