Integrated Ultrasonic Imaging for Inspection of Near-Surface Defects in Safety-Critical Components

The project aims to bring a step change improvement to the sensitivity of ultrasonic array imaging for Non Destructive Evaluation (NDE) to address the needs of the power generation industry. This will be based on the processing of the Full Matrix Capture (FMC) set of signals between all pairs of transducer elements, as is already established for state-of-the-art Beam-Forming (BF) imaging, but the approach for treating the signals will be entirely different. Instead of calculating a direct image from the FMC measurements, an inverse scattering approach will be pursued: this will involve iterations of unknowns in an integrated forward model of the array configuration, material properties and geometry, to find a best match to the measured signals. This approach has been shown to overcome conventional BF limitations in the context of the imaging of biological tissues, achieving intensified sensitivity and sub-wavelength resolution. This project will develop the concept for NDE, employing a specific, but commonly encountered, critical inspection task as a realistic example to focus the work.

The proposal is being submitted within the UK Research Centre in NDE (RCNDE) to its targeted research programme. The proposal has been reviewed internally by the RCNDE, approved by the RCNDE board, and supported financially by two RCNDE industrial members.

Ultrasonic imaging is a vital part of Non Destructive Evaluation (NDE), and its deployment in industry is growing rapidly. It is being driven by the much-reduced cost of computing together with strong growth in the manufacture of high quality transducer arrays and controller hardware. This opportunity has been exploited by research in leading groups in the UK and internationally in developing powerful new algorithms. The net result is that ultrasound imaging in NDE is delivering big improvements in capabilities for detection and characterisation of defects and this is translating into use in industry. Thus, not surprisingly, the consortium of the industrial members of the UK Research Centre in NDE (RCNDE) has identified imaging in the majority of the objectives of its 5-10-20 year vision.

There is a particularly pressing need for the detection and characterisation of small defects in thick-section components in power generation plant. The current capabilities, based on Beam-Forming, cannot achieve the required NDE performance for this need. This project aims to deliver that performance, by the proposed new approach. It is also expected that the new capability arising from this work will be of value to improve imaging in many other high-value safety-critical applications.

This proposal is being submitted within the RCNDE research programme, which defines it as research that is accepted by the RCNDE board as having strong relevance to industrial need. The RCNDE includes a wide spectrum of industries in the UK and abroad. The research idea has been considered by all the industrial members since the early stages of the proposal development, thus allowing for the industrial perspective to be fully integrated in the proposal. In particular, the proposal was assessed by the RCNDE board at both outline and full proposal stage. It was formally voted on at the January 2014 board meeting and in a secret ballot of the RCNDE academic and industrial members received outstanding scores of over 85% on both technical quality and industrial relevance.