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

Lead Research Organisation: Imperial College London
Department Name: Dept of Mechanical Engineering


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.

Planned Impact

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.


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Elliott JB (2019) Sizing Subwavelength Defects With Ultrasonic Imagery: An Assessment of Super-Resolution Imaging on Simulated Rough Defects. in IEEE transactions on ultrasonics, ferroelectrics, and frequency control

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Zhang C (2018) The Application of the Factorization Method to the Subsurface Imaging of Surface-Breaking Cracks. in IEEE transactions on ultrasonics, ferroelectrics, and frequency control

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Zhang C (2018) Eliminating backwall effects in the phased array imaging of near backwall defects. in The Journal of the Acoustical Society of America

Description Leading candidate algorithms for high resolution imaging of small surface-breaking cracks have been evaluated. This has led to new understanding and capabilities for the best approach for ultrasound array imaging of small defects at or near a remote surface of a component.
Exploitation Route Deployment for inspection in industry. Academic development of ultrasound imaging methods.
Sectors Aerospace, Defence and Marine,Agriculture, Food and Drink,Energy,Manufacturing, including Industrial Biotechology,Transport

Description The methodology and algorithms arising from this project have been disseminated to the two industrial partners. An EngD student at Rolls-Royce worked in parallel to implement these capabilities for their industrial use. The EngD student was employed afterwards by Rolls-Royce, based on the progress of this research. The imaging capability arising from this work have provided the basis for a significant improvement in the resolution of ultrasound imaging of small defects in safety-critical pressure-containing components, including nuclear pressure vessels and piping; a particular value has been for defects with rough surfaces; this is now deployed in the industrial inspection of nuclear power components. The methodology is quite generic, so it will impact broadly on ultrasound imaging for inspection of engineering components and infrastructure.
First Year Of Impact 2018
Sector Aerospace, Defence and Marine,Energy,Manufacturing, including Industrial Biotechology
Impact Types Economic

Description Amec FW ultrasound NDE 
Organisation AMEC
Country United Kingdom 
Sector Private 
PI Contribution Ultrasound capabilities for NDE
Collaborator Contribution Cash, samples, steering
Impact publicactions, technology transfer
Start Year 2011
Description R-R ultrasound NDE 
Organisation Rolls Royce Group Plc
Country United Kingdom 
Sector Private 
PI Contribution Develop ultrasound NDE methods for use by R-R for inspections of nuclear power plant components
Collaborator Contribution Cash, steering meetings, deployment of outcomes within the company
Impact Technology transfer to partners, publications
Start Year 2010