Vibrations between the workpiece and the cutting tools in machining processes can deteriorate machining accuracy and surface quality. However controlled small amplitude (several microns) high frequency (tens of kHz) vibrations can facilitate machining processes. This is called vibration assisted machining (VAM). VAM combines precision machining with small amplitude vibration between tool and workpiece, and for appropriate machining and vibration parameter sets, the tool can periodically loses contact with the chip, which changes the cutting kinematics and mechanics, and can improve machining performance. Reported benefits include: reductions in machining forces; improved surface finish and form accuracy; suppression of burr formation; reduction of tool wear and extension of tool life; etc. In turning process, the vibration assistance is relatively easy to implement as the tool is stationary. Both 1D vibration assisted system, i.e. linear vibration assistance in the cutting direction, and 2D vibration assisted system, i.e. elliptical vibration motion in the plane of cutting direction and depth of cut direction have been applied in turning processes with success. Due to the complexity of kinematics and dynamics of the milling process, application of vibration assistance to milling has received little attention. Currently efforts on vibration assisted milling are purely empirical and lack accurate kinematic and dynamic models to design an optimal VAM system, and all 2D vibration assisted milling studies have been limited to low frequencies which are not applicable to micro milling operations. In addition, to obtain complex shape geometry, the milling process requires a feed vector in arbitrary direction in space, i.e. both a vertical and horizontal components of feed vector are necessary for 3D end milling. However, currently no 3D VAM systems have been reported. To overcome these limitations on the state-of-the-art and make use of the advantages of vibration assistance, this project will develop a novel compact 3D vibration assisted machining system for micro milling of free-form surfaces on hard-to-machine materials, and evaluate its performance through machining experiments. Fabrication of precision micro products from hard-to-machine materials, such as semiconductor materials, piezoelectric materials, glasses, is increasingly in demand in various applications such as bio-engineering, MEMS, optics, etc. Success of the project would open new industrial avenues for processing such materials at a more cost-effective manner. However, to achieve this in practice, development of a 3D vibration assisted machining system and its associated design and modelling methodology are urgently needed.

This proposal is for a joint project between internationally-leading, UK heat transfer research groups at the Universities of Edinburgh, Brunel and Queen Mary, London in collaboration with four industrial partners (Thermacore, Oxford Nanosystems, Super Radiator Coils and Rainford Precision) in the areas of micro-fabrication and thermal management. Advances in manufacturing processes and subsequent use of smaller scale electronic devices operating at increased power densities have resulted in a critical demand for thermal management systems to provide intensive localised cooling. To prevent failure of electronic components, the temperature at which all parts of any electronic device operates must be carefully controlled. This can lead to heat removal rate requirements averaging at least 2 MW/m2 across the complete device, with peak rates of up to 10-15 MW/m2 at local 'hot spots'. Direct air cooling is limited to about 0.5 MW/m2 and liquid cooling systems are only capable of 0.7 MW/m2. Other techniques have not yet achieved heat fluxes above 1 MW/m2. Boiling in microchannels offers the best prospect of achieving such high heat fluxes with uniform surface temperature. In a closed system an equally compact and effective condenser is required for heat rejection to the environment. At high heat flux, evaporator dry-out poses a serious problem, leading to localised overheating of the surface and hence potentially to burn out of electronic components reliant on this evaporative cooling. Use of novel mixtures, termed 'self-rewetting fluids', whose surface tension properties lend themselves to improved wetting on hot surfaces, potentially offers scope for enhanced cooling technologies. In this project, two different aqueous alcohol solutions (one of which is self-rewetting) will be studied to ascertain whether they can provide the necessary evaporative and condensation characteristics required for a closed-loop cooling system capable of more than 2 MW/m2. Researchers at the University of Edinburgh will study the fundamentals of wetting and evaporation/condensation of the mixtures to establish the optimum mixture concentrations and heat transfer surface coating for both evaporation and condensation, using advanced imaging techniques. At Brunel University London, applications of the fluids in metallic single and multi microchannel evaporators will be investigated. Researchers at Queen Mary University London will carry out experimental and theoretical work on condensation of the mixtures in compact exchangers. The combined results will feed into the design of a complete microscale closed-loop evaporative cooling system. Thermacore will provide micro-scale heat exchangers and Oxford Nanosystems will provide structured surface coatings. Sustainable Engine Systems, Super Radiator Coils and will provide advice and represent additional ways of taking developments originating from this research to the market. Rainford Precision will provide Brunel University micro tools and support on their use in micromachining.

Current developments and future trends in small-scale devices used in a variety of industries such as electronic equipment and micro-process and refrigeration systems, place an increasing demand for removing higher thermal loads from small areas. In some cases further developments are simply not possible unless the problem of providing adequate cooling is resolved. The progression from air to liquid and specifically flow boiling to transfer the high heat fluxes generated is thus the only possible way forward. Evaporative cooling can, not only transfer these loads but also offer greater temperature uniformity since the working fluid can be (in a carefully designed system) at a constant saturation temperature. The consideration of microchannel flow boiling processes has been made possible by developments in microfabrication techniques both in metals and substances such as silicon. However, there still remain fundamental fluid flow and heat transfer related questions that need to be addressed before a wider use of these micro heat exchangers is possible in industry. The specific challenges that will be researched - both fundamental and practical in nature - include flow instabilities and mal-distribution which are the result of interaction between the system manifolds and the external circuit. These can lead to flow reversal and dry-out in the heat exchanger with subsequent drastic reduction in heat transfer rates. The understanding of the fundamental physical phenomena and their relevance to industrial designs is one of the focal points and constitutes one of the major challenges of the proposed research. The effect of other parameters such as inlet sub-cooling, which again relates not only to the micro-heat exchanger itself but also to the overall design, will be addressed along with material/surface characteristics through the use of both metallic and silicon microchannels. The work proposed will include carefully contacted detailed experiments measuring relevant parameters such as local heat flux, temperature and pressure combined with flow visualization through industrially available and purposely developed and manufactured sensors. The research teams will not only develop or adapt advanced instruments for accurate measurements at these small scales but also develop new three-dimensional numerical tools capable of capturing the extremely complex physical phenomena at, for example the triple-line (vapour-liquid-solid). These techniques will not only help elucidate the current phenomena but can find wide application in similar research, both in thermal and biomedical flows. The proposal brings together two teams of academics working both in microfabrication/sensors and two-phase flow supported by industry (Thermacore, Selex Galileo, Sustainable Engine Systems and Rainford Precision) to tackle some of the key fundamental challenges that will enable a wider adoption of this cooling method hence meeting current and future needs in the industry. The proposed research will also have a wider impact on energy conservation and environmental footprint trough, for example, more efficient thermal management of data/supercomputing centres around the world that can lead to a reduction in energy consumption and reuse of heat that would otherwise be rejected.

NIMRC's research portfolio is at the heart of the national manufacturing agenda and is active in the generation of patents and the construction of full scale demonstrators to enhance technology transfer. The Centre has strong links with industry in a range of sectors including aerospace, automotive, instrumentation, power engineering, steel, textiles and clothing, and consumer product sectors. With the exception of a small number of blue-skies projects, all projects are driven by industrial need. During the past 3 years, the Nottingham Innovative Manufacturing Research Centre (NIMRC) has continued to succeed in its stated objectives. By exploiting synergies between themes and research strands within the Centre and with other academic groups and industry outside the Centre, NIMRC has continued to expand its world-leading research portfolio and develop new directions. From a start of 8 principal investigators in the IMRC, this year we have an additional 15 investigators participating in current projects within the portfolio, complemented by 22 researchers and 29 research students. In the past 3 years, 9 students have been been awarded a PhD and another 7 are currently submitting their dissertations.The quality, timeliness and novelty of NIMRC's research is highlighted by its publication record. Since the Centre began, staff have published widely in peer review journals and presented at prestigious international conferences.The IMRC status has attracted a wider research community both in the University and without. The NIMRC continues to develop strategic partnerships with research groups outside the University and include many internationally recognised centre's of manufacturing excellence. The Centre also has strong links with other IMRCs. Already, NIMRC has collaborative research projects with Warwick, Bath, Cranfield and Loughborough IMRCs. NIMRC is also participating in the Grand Challenge 3D Mintigration related to the economic Manufacture of 3D Miniaturised Devices . NIMRC has made excellent progress during the last 3 years towards its stated objectives. It believes that the future research strategy it has developed will continue to address both the immediate and longer term needs of the manufacturing industry and it looks forward to providing the enabling research needed to improve the competitiveness of UK plc. The importance of NIMRC's world-class research is demonstrated in the composition of the Industrial Advisory Board which includes 20 senior industrialists from well established UK manufacturing sectors. The Board is impressed with the work of the Centre and the rapport with the Board of PIs. Board members have their own examples of how their company has benefited from the work of the NIMRC. In summary, Rolls-Royce and the Industrial Advisory Board fully support the activities of the NIMRC and will continue to do so. Chair of NIMRC Industrial Advisory Board, Mr Stephen Burgess, Manufacturing Process and Technology Director, Rolls-Royce Plc.