Modelling of Ultrasonic Response from Rough Defects

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

Abstract

This proposal seeks funding for a three year research programme into the back-scattering of ultrasound from rough surfaces, with specific application to the Non-Destructive Evaluation (NDE) of rough cracks. This addresses an important industrial goal: to be able to predict with confidence the reflection of ultrasound from a rough defect, at any chosen angle and frequency, which could then be used to make the case for a desired plan for inspection. The research will extend knowledge in two complementary areas: the creation of an envelope approach to predict the minimum back-scatter to be expected with confidence from a statistical description of the roughness, and the development of Finite Element modelling procedures to guarantee accurate, but efficient, modelling of the scattering from detailed representations of specific rough defects. The work will be undertaken jointly by a mathematical and an engineering team, both at Imperial College. The proposal is being submitted within the UK Research Centre in NDE (RCNDE) to the targeted research programme, the funding for which is earmarked by EPSRC for industrially driven research.

Planned Impact

Modelling of the reflection of ultrasound from complex defects is a topic of very great current interest in both academia and industry. In academia the availability of faster cheaper computing power is enabling rapid development of numerical modelling capability, now making possible for the first time the accurate simulation of ultrasound scattering from realistic defects. In industry, the possibility of doing this is providing a strong pull to get these new capabilities into use. The present generation of modelling software in use in industry, based on ray models, is well developed for the planning of inspection setups and for training inspectors, but it is conspicuous that there is a serious weakness in the ability of these tools to make reliable predictions of the reflection of the ultrasound from realistic defects. As a result, modelling is not yet achieving its potential to be used as a predictive tool to demonstrate the safety of specific inspection plans. If this could be achieved then huge cost savings would be enabled by replacing experimental technical justifications by modelling ones. Furthermore, the improved capability would reduce conservatism in the assessment of inspection results, so saving further large sums. The particular modelling topic of this proposal, reflections from rough cracks, has been identified to be of great value to the companies which have to make technical justifications for inspections of safety-critical nuclear power plant, hence the two particular companies, British Energy and Rolls-Royce, which are collaborating in the work. An indication of the importance of this particular topic is that it has been identified as a specific research goal in the UK HSE Nuclear Research Index. However, the capability will also be of value to other sectors where safety-critical cases have to be made, significantly including fossil fuel power plant for which the next generation of designs will use the high performance high temperature materials currently associated with nuclear plant. The primary route to communication of the results of the project to industry will be to the two collaborating companies. Both of these companies have backgrounds in developing modelling and experimental methods for the qualification of inspections for nuclear plant components. They are thus well set up to bring the findings into use. They will be engaged in the project programme throughout, including provision of information and participating in the review meetings, and so will take on the understanding during the project as well as the formal deliverables at the end. Additionally, the other industrial members of the UK Research Centre in NDE (RCNDE) will be informed of the principal steps of progress, via the RCNDE annual review, and so will be able to take early advantage of the new capabilities. The NDE group at Imperial College has an outstanding record in technology transfer, via licensing, close working with partner industrial companies, and spinning out new companies, and are strongly focused on delivering the benefits of research to industry. They are thus well positioned to judge the appropriate transfer routes and maximise the the transfer of useful findings to industry.

Publications

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Antonakakis T (2014) An asymptotic theory for waves guided by diffraction gratings or along microstructured surfaces. in Proceedings. Mathematical, physical, and engineering sciences

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Antonakakis T (2014) Homogenisation for elastic photonic crystals and dynamic anisotropy in Journal of the Mechanics and Physics of Solids

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Antonakakis T (2013) Asymptotics for metamaterials and photonic crystals. in Proceedings. Mathematical, physical, and engineering sciences

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Choi W (2016) A generic hybrid model for the simulation of three-dimensional bulk elastodynamics for use in non-destructive evaluation. in IEEE transactions on ultrasonics, ferroelectrics, and frequency control

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Colombi A (2016) A seismic metamaterial: The resonant metawedge. in Scientific reports

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Colquitt D (2015) High frequency homogenisation for elastic lattices in The Quarterly Journal of Mechanics and Applied Mathematics

 
Description The key output of the research is improved methodology for the ultrasonic inspection (NDT) of defects with rough surfaces. This is important for safety-critical components, eg in aerospace and power generation. The roughness causes a reduction of the ultrasonic reflectivity from the defects, and this has led to the use of very conservative factors of safety. Our work enables these safety factors to be reduced substantially while also improving the confidence of the inspections.
Exploitation Route Direct use in industry by the industrial partners, in collaboration with us to achieve this. Use by other industry via public domain disseminations. Use in academia to inform further research in modelling of scattering from defects.
Sectors Aerospace, Defence and Marine,Energy,Manufacturing, including Industrial Biotechology

 
Description At completion of the project we have prepared a package of modelling tools and a final report for the industrial partners. This provides the basis for the partners to deploy the findings for their own industrial use. Additionally, direct support has been provided to two of the partners to get the tools into use in their offices/laboratories. The new tools will be particularly useful for the qualification of inspections of safety-critical components in new-build electricity generating plant. The scientific basis for calculating ultrasound response of stochastic scattering problems inspired ideas to improve the NDT of rough cracks for cases in which the NDT technique uses measurements of the diffraction from the tips of the cracks. This has led to a 3 year £0.6M EPSRC project (EP/P01951X/1) which started in April 2017.
First Year Of Impact 2015
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 EDF ultrasound NDE 
Organisation EDF Energy
Country United Kingdom 
Sector Private 
PI Contribution Ultrasound NDE methods for power plant components
Collaborator Contribution cash, steering meetings
Impact technology transfer, publications
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