NONCONTACTULTRASONIC · Non-contact ultrasonics: new methods for large and small scale measurements

Ultrasonic measurements have a wide range of applications, from non-destructive testing (NDT) on bridges, pipeline and railway track, to measurements of elastic constants of single crystals, whose properties are key to the development of new magnetoelastic devices. Traditional techniques require the transducers to be in physical contact with the sample, and non-contact ultrasonics (NCU) is attracting more interest. Improvements to NDT through the use of NCU are leading to new applications in hostile environments, such as measurements at high temperatures or of moving samples, helped by the lack of need for couplant. This proposal covers applications of great importance which could benefit from the use of NCU. The problem of partially closed cracking in metals will first be investigated. Stress corrosion cracking can cause catastrophic damage to pipeline, and there is no current technique which can reliably detect and characterise it. The physical phenomena associated with transmission of the ultrasound will be probed to develop new methods of detecting defects using laser ultrasonics and electromagnetic acoustic transducers. The project will investigate and explain the behaviour of the ultrasonic interactions with defects in the vicinity of cracks, including non-linear behaviour around a partially closed crack. Later work will use ultrasound for elastic and magneto-elastic measurements of single crystals. These measurements are able to quickly and inexpensively identify interesting and important new systems, saving the time and resources which may have been used to investigate samples using neutron studies. New NCU techniques will be developed, capable of detecting magnetic phase changes through variations in the coupling efficiency. The benefits of combining the results from standard measurements with those from novel electromagnetic NCU techniques will be studied. The research will facilitate collaboration with groups within the Department and internationally.