SUB-MHZ ULTRASONIC INSPECTION

This proposal is associated with the targeted research programme of the UK Research Centre for NDE (RCNDE), an EPSRC-supported research centre. It is clear from discussions held with both academics and industrial members within RCNDE that the ultrasonic inspection of highly scattering/attenuating materials is still a large problem that needs to be addressed. The particular materials in question - such as thermal insulation materials, refractory linings, rubbers and thick sections of glass fibre reinforced polymer composites - are industrially very important. In many cases, there are not many alternatives for inspection, in particular if portability and non-radiological methods are required.

The research will investigate new ways in which ultrasonic frequencies below 1 MHz can be applied to this problem. This will require research into various aspects of the measurement. Firstly, new transducer designs will be needed, that can generate signals with the required bandwidth. It is planned to try micro fibre composite (MFC) devices for this, teamed up with more conventional PZT elements. These will then be used with various forms of coded waveform, so that cross-correlation can enhance the measurement in terms of detectability and reduced signal to noise levels. In addition, scattering from interfaces and non-defect objects casue clutter in the signal. It is planned to investigate ways of reducing these effects, byusing other ideas such as (a) using a collimation system, and (b) using polarised shear waves. Finally, a system will be dseigned which uses some or all of these elements, and which can tuned to operate at different frequency ranges, depending on the application.

The work will be performed in collaboration with three industrial sectors: marine vessel manufacture, the oil and gas industries, and metal forming. All have particular problems with methods of inspecting acoustically attenuating and scattering material. These include coatings and thick composites; thermal insulation layers, corrosion under insulation, and risers; refractory materials, and others. As part of the work, the research will be used to design a portable system that can be used in these industries. This will be tested in the laboratory, before field tests are performed in each case.

The proposal is linked with the UK Research Centre for Nondestructive Evaluation (RCNDE), which has been identified by EPSRC as a strategic area in which to provide funding. Associated with this Centre are 15 industrial members, each of which pays an annual membership fee as a full member. There are another 25 industrial Associate Members, where the industrial partners range from large multinationals to small SMEs. RCNDE thus provides direct input into major research themes within the EPSRC portfolio. These include Energy, and Manufacturing the Future. NDE plays a vital role in these areas. The present proposal forms part of the Targeted Research programme, and is sponsored by a number of industrial members. Targeted research is focused on the medium-to-long term NDE requirements of member companies, as well as fulfilling RCNDE's strategic objectives. The choice of projects depends on the interests of the members. It will be evident from the above that the RCNDE has established some very effective Pathways to Impact, via its structure, and the interactive way in which the industry co-funds this research. This means that, at all times, the research performed as part of this Centre already has an identifiable impact directly into the various industrial sectors of interest. The impact is greater because of the feedback to industry via membership of RCNDE Board meetings, where future research projects are discussed, and in the dissemination events where summaries of annual activities are provided to members and guests. The proposal also fits within the RCNDE strategic vision exercise, where the vision of the RCNDE was formulated in consultation with industrial members. The present proposal fits well within the strategic objectives of improved NDE quantification and the closer integration of NDE and structural integrity, by allowing an important class of highly attenuating and/or scattering material to be inspected. It also adds to the objective of improved performance, by giving improved signal to noise.

The proposal has been generated with the support of industrial members of RCNDE from both the Manufacturing sector, and from the oil and gas industry. Both of these map onto two of the strategic theme areas within the EPSRC portfolio (Energy and Manufacturing the Future). There is thus likely to be direct Impact within these areas. The companies involved, and their areas of interest, can be summarised as follows:

1 .BAE Systems: The manufacture of marine vessels, including nuclear-powered submarines;
2. Tenaris: Metallic tubing supply, with a particlular interest in refractory materials for furnaces;.
3. Shell and BP: oil companies, with an interest in NDE for the inspection of thermally-insulated pipelines and pipework.

It will be evident that there is likely to be a high level of impact directly into these important areas, which will all impact on aspects of energy, and how to manufacture the future. There will also be direct links to the environmental impact of these activities.