Nonlinear ultrasonic imaging for material and defect characterisation

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More accurate characterisation of materials and defects in engineering structures leads to improved predictions of remaining life and hence increased safety and reliability. Recent research suggests that nonlinear ultrasonics provides highly sensitive information on the nature of materials and defects. This project aims to use this nonlinear information, alongside other traditional techniques, to provide more accurate characterisation. In particular, nonlinear imaging techniques have the potential to pinpoint features such as closed crack tips and regions of plasticity that have, to date, proved impossible to detect. This project will investigate, understand and quantify the new information provided by nonlinear imaging techniques from a range of material degradation and defect morphologies. The core approach taken will be numerical modelling. The objectives will be to understand a) how the nonlinear signals are created, b) how they spread out and interact with the test structure and c) how measurements can be optimised to best characterise the damage. Alongside this modelling will be the requirement to ensure that the models are validated with suitable experiments. This project will also explore how this nonlinear information can be best combined with traditional phased array imaging, to provide the most accurate and comprehensive characterisation results.