Thermosonics is a novel non-destructive evaluation (NDE) technique that employs an infrared camera to image defects, typically cracks or delaminations, by detecting the heating caused by friction at the surfaces of defects when a part under inspection is vibrated. Typically, a pulse of high power ultrasound in the 20-100 kHz range is applied at one point on the test-piece to generate a high frequency vibration field in the structure. The method is considerably quicker than conventional ultrasonic or eddy current inspection techniques that require point by point scanning. The method is also particularly well suited to the detection of closed cracks that can cause problems with other techniques. Whilst impressive results have been achieved in a number of laboratories worldwide, the system, particularly the excitation, needs engineering. The reliability of the system needs to be improved - there is concern that defects in some locations are missed; this is almost certainly a function of the vibration field that is generated by the exciter. The amplitude of vibration required needs to be defined and assurance that this will not propagate the defects is required. To date a high power ultrasound horn, of the type produced commercially to weld plastics has been used to excite vibrations. The high power horn has the major disadvantage that it is bulky and is very difficult to couple reproducibly to the structure. This proposal follows an earlier research programme in which the applicants have established a quantitative understanding of the excitation requirements for a successful thermosonic inspection. This programme has shown that for a number of industrially important applications, successful thermosonic inspections can be completed using significantly lower amplitude vibrations than those associated with high power ultrasonic welding horns. An objective of this proposal is to design and produce ultrasonic exciters that are engineered for specific demonstrator applications. These demonstrators will be selected from applications that have been found to be particularly suitable (ie requiring low excitation power) for thermosonic inspection in consultation with the industrial partners who are supporting the project. The lower power requirement and tailored design should make the exciter significantly smaller and lighter than the bulky ultrasonic welding horns in current use. The other part of a thermosonic system is an infrared camera that was, until recently, also a bulky heavy component. However, very small microbolomer array infrared cameras are now available for use in NDE systems. The intention is to produce a compact portable, possibly hand held, thermosonic inspection system incorporating a small microbolometer array camera and a custom engineered vibration exciter. A full vibration analysis of the demonstrator parts will be completed to determine the optimum mode to excitation to ensure the reliability of the inspection. The system will also include a means of monitoring the vibrations to enable the user to check that adequate vibration amplitude is produced in a part to reliably complete a test. The inspection system will be field tested on a selection of demonstrator parts. The overall aim of the project is to take thermosonics, a very promising new NDE technique, out of the laboratory and to introduce it successfully into industry.In addition to producing a prototype testing system, the project will advance scientific understanding of the performance of ultrasonic exciters, and in particular the influence of the coupling between the exciter and the structure. Novel means of non-contacting measurement of the vibration field produced by the exciter will be investigated and these are likely to have other scientific and industrial applications.

Rapid and transformative advances in power electronic systems are currently taking place following technological breakthroughs in wide-bandgap (WBG) power semiconductor devices. The enhancements in switching speed and operating temperature, and reduction in losses offered by these devices will impact all sectors of low-carbon industry, leading to a new generation of robust, compact, highly efficient and intelligent power conversion solutions. WBG devices are becoming the device of choice in a growing number of power electronic converters used to interface with and control electrical machines in a range of applications including transportation systems (aerospace, automotive, railway and marine propulsion) and renewable energy (e.g. wind power generators). However, the use of WBG devices produces fast-fronted voltage transients with voltage rise-time (dv/dt) in excess of 10~30kV/us which are at least an order of magnitude greater than those seen in conventional Silicon based converters. These voltage transients are expected to significantly reduce the lifetime of the insulation of the connected machines, and hence their reliability or availability. This, in turn, will have serious economic and safety impacts on WBG converter-fed electrical drives in all applications, including safety critical transportation systems. The project aims to advance our scientific understanding of the impact of WBG devices on machine insulation systems and to make recommendations that will support the design and test of machines with an optimised power density and lifetime when used with a WBG converter. This will be achieved by quantifying the negative impact of fast voltage transients when applied to machine insulation systems, by identifying mitigating strategies that are assessed at the device and systems level and by demonstrating solutions that can support the insulation health monitoring of the WBG converter-fed machine, with support from a range of industrial partners in automotive, aerospace, renewable energy and industrial drives sectors.

To build new research capability in order to address nationally strategic objectives for the support of health of discipline in priority areass such as electrical power engineering and energy. Such new capacity would be intended to undertake research and support the growth of UK industry innovation. This is a project that requires major investments to provide adequate breadth and depth in order to increase prospective research impacts, therefore consortium partners (apart from EPSRC) include Rolls-Royce, ScottishPower, National Grid and Strathclyde University. The proposed investment acknowledges that there has been a serious reduction of academic staff specialising in electrical power engineering in UK-HEIs. It is also recognised that, in order to retain and develop electrical power research capability, there is a need to take a joint HEI, industry & government approach to investment and commitment in this area. The support of research centres with the necessary critical mass to undertake basic, strategic and applied research is seen as a strategic imperative. UK industry and society will benefit greatly from a sustainable, active, internationally leading research base in electrical power engineering and energy systems. In addition to the erosion of the electrical power research base, there is a serious reduction in the undergraduate and postgraduate populations that new, active academic staff could help to address (c.f. recent IEE review and subsequent establishment of the Power Academy). It is important to note that these principles are also entirely consistent with subsequent objectives that have emerged in the EPSRC Science and Innovation Awards scheme. As such, the proposed programme, incorporating major industrial funding, provides additional value and scope to complement the first round EPSRC Science and Innovation Awards. The funding commitment from each of the industrial partners along with direct Strathclyde commitments will provide significant added value to the proposed EPSRC Star investments in terms of research scope, scale and critical mass.

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