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

Final Report Summary - NONCONTACTULTRASONIC (Non-contact ultrasonics: new methods for large and small scale measurements)

NonContactUltrasonic covered two applications of non-contact methods of ultrasonic generation and detection, using them to bring advances to the areas of non-destructive testing (NDT, project 1) and materials characterisation (project 2).

The NDT research focussed on the problem of surface-breaking defects in metal components in industry, in particular rolling contact fatigue on rails and stress corrosion cracking in pipework. If left undetected and untreated, these defects can lead to breakage of the component and potential disaster. Current methods are limited in terms of speed, sensitivity, and even the ability to detect some of the defects, and hence this project has direct industrial focus. We investigated the interaction of ultrasonic surface waves with typical defect geometries, understanding the physics behind the interactions, and using this to build a scanning system to both detect and characterise cracking. The system was then demonstrated on a set of samples removed from industry which exhibited cracking, with successful defect imaging.

Two separate areas of materials characterisation were then investigated. Contact and non-contact ultrasonic methods were used to measure the elastic properties of single crystals, with a new measurement probe containing novel electromagnetic acoustic transducers combined with new data analysis techniques for characterisation. We studied magnetic phase transitions in rare-earth alloys, understanding the phases at different temperatures and applied magnetic fields. Following this, thin membranes of materials such as Ge were investigated using laser ultrasonic detection mechanisms, with a new method developed for characterising stress within the membrane and finding its robustness to shock.

The original objectives of the grant have all been met, with the membrane characterisation system offering an added bonus. Development of the defect characterisation technique into an industrial prototype, and building of collaborations for exploiting the materials characterisation research, are now ongoing.