Ultrasonic inspection is the primary technique for the detection of planar flaws within
the nuclear industry. Current inspections are typically limited to the application of
rigid wedge, single element transducers to components with regular surface geometry.
This thesis addresses some of the limitations of this approach and develops new
methods and techniques that are suitable for application in an industrial environment.
Inspection modelling is a cost effective technique for inspection design and
qualification; it can be used to aid understanding of the inspection process, and
provides valuable insight into inspection data interpretation. In this work semianalytical
and numerical modelling tools have been used to accurately and efficiently
simulate the ultrasonic inspection of large complex components.
Modelling tools have also been applied to aid in the design of a membrane coupled
conformable phased array device. The membrane coupled array is a low-cost, robust
device that uses a conventional phased array coupled to the outer surface of the
component under test via a water path encapsulated by low-loss membrane. Early
design of this device was performed by Long and Cawley at Imperial College,
London. The work reviewed in this thesis discussed the further development of this
membrane coupled device and its application for the inspection of a specific target
application component.
The target application is a safety critical, thick-walled stainless steel section of pipework
that contains an austenitic weld. The current inspection of this component is
carried out by first removing the component weld cap and then mechanically raster
scanning a large number of rigid wedge single element transducers. Weld cap
removal is an expensive time consuming task that can lead to excessive wall thinning
and the exposure of small surface breaking defects. The motivation for this work is to
provide complete inspection of the weld and heat affected zone with the weld cap in
place. It is also designed to improve inspection speed and accuracy, and to reduce the
amount of user intervention required to complete the inspection in a hostile
environment
Inspection results from the 2nd and 3rd generation membrane coupled device on
multiple test-pieces representative of the target application are presented. These
results demonstrate that the membrane coupled device can be used to detect defects in
locations that cannot be inspected using conventional techniques. The amount of
scanning required can be significantly reduced, simplifying the inspection and helping
to improve inspection speed by over 60% in comparison to the single element
approach.