Browsing by Author "Tonnellier, Xavier"
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Item Open Access Application of probabilistic modelling for the uncertainty evaluation of alignment measurements of large accelerator magnets assemblies(IOP, 2018-03-15) Doytchinov, Iordan; Tonnellier, Xavier; Shore, Paul; Nicquevert, Bertrand; Modena, Michele; Mainaud-Durand, HélèneMicrometric assembly and alignment requirements for future particle accelerators, and especially large assemblies, create the need for accurate uncertainty budgeting of alignment measurements. Measurements and uncertainties have to be accurately stated and traceable, to international standards, for metre-long sized assemblies, in the range of tens of µm. Indeed, these hundreds of assemblies will be produced and measured by several suppliers around the world, and will have to be integrated into a single machine. As part of the PACMAN project at CERN, we proposed and studied a practical application of probabilistic modelling of task-specific alignment uncertainty by applying a simulation by constraints calibration method. Using this method, we calibrated our measurement model using available data from ISO standardised tests (10360 series) for the metrology equipment. We combined this model with reference measurements and analysis of the measured data to quantify the actual specific uncertainty of each alignment measurement procedure. Our methodology was successfully validated against a calibrated and traceable 3D artefact as part of an international inter-laboratory study. The validated models were used to study the expected alignment uncertainty and important sensitivity factors in measuring the shortest and longest of the compact linear collider study assemblies, 0.54 m and 2.1 m respectively. In both cases, the laboratory alignment uncertainty was within the targeted uncertainty budget of 12 µm (68% confidence level). It was found that the remaining uncertainty budget for any additional alignment error compensations, such as the thermal drift error due to variation in machine operation heat load conditions, must be within 8.9 µm and 9.8 µm (68% confidence level) respectively.Item Open Access Commercial development of bio-combustible fuels from hydrothermal liquefaction of waste using solar collectors(American Institute of Physics, 2018-11-08) Pearce, Matthew; Tonnellier, Xavier; Namrata, Sengar; Samson, ChrisCurrent methods to improve the viability of microalgae based biofuel production depend on improved microalgae strains, biorefinery concepts and identification of higher value applications such as cosmetics and nutraceuticals. Despite such efforts, the energy inputs into the microalgae conversion process remain high. The technical approach presented is to design, deploy and field test an integrated set-up of Concentrated Solar Power and Hydrothermal Liquefaction systems to produce bio-oil and evaluate the production and conversion processes. Phycofeeds’ approach is to integrate CSP and HTL technologies into the conversion process to improve the energy efficiency and the economic case for scaling microalgae based biofuel production. Further sustainability enhancements are achieved by integrating wastewater feedstock and market integration of output by-products for the aquaculture feed industry. This paper presents the microalgae harvesting and HTL bio-oil formation analysis procedures on a pre-pilot field scale. Solar concentrating captors are described and theoretical values obtained prior to experimental work that will be carried out in India.Item Open Access The design and modification of a parabolic trough system for the hydrothermal liquefaction of waste(AIP Publishing, 2019-07-26) Almond, Heather; Tonnellier, Xavier; Sansom, Christopher L.; Pearce, Matt; Sengar, NamrataWe describe the design of a small-scale parabolic trough with a high-pressure absorber bundle to convert microalgae into bio-oil. The “proof-of-concept” system uses an existing Global CSP solar captor, with its reflectance enhanced by the addition of Skyfuel® ReflecTech Plus polymer film and has its original receiver tube replaced by a novel high-pressure multi-tube absorber and reactor. Initial results obtained at Kota University in Rajasthan, India demonstrated that temperatures up to 320°C are possible, and a bio-oil, similar to palm oil, was extracted from the reactor.Item Open Access Effects of solid lubricants on wire and arc additive manufactured structures(Professional Engineering Publishing, 2014-04-01T00:00:00Z) Adebayo, Yinka; Mehnen, Jorn; Tonnellier, XavierThis paper reports a systematic study which examines the use of solid lubricants in the sequential deposition and machining of wire and arc additive manufactured parts and characterises the effects of solid lubricants on the microstrucure. This paper also describes the microstructure developed and the effect on micro hardness by manual cleaning of deposited layers with acetone. Mild steel wire consumable electrode G3Si1 with the diameter of 0.8mm was used. The use of graphite and molybdenum disulphide as solid lubricant in machining was also studied and a scanning electron microscope was used in detecting any form of lubricants contamination. A systematic study shows that a significant amount of solid lubricant contamination can be found in the deposited material. Furthermore, the results indicate that even cleaning of the wire and arc additive manufactured surfaces with acetone prior to the weld deposition can affect the microstructure of the deposited material.Item Open Access Grinding metre scale mirror segments for the E-ELT ground based telescope(Technische Rundschau, Hallwag Publishers; 1999, 2011-04-21T00:00:00Z) Comley, Paul; Morantz, Paul; Shore, Paul; Tonnellier, XavierThe next generation of ground based telescopes require many hundreds of metre scale off-axis mirrors. In this paper the grinding of a 1.45m scale Zerodur® mirror segment for the European Extremely Large Telescope (E-ELT) is introduced. Employing an R-theta grinding mode with a multi stage grinding process material removal rates of up to 187.5mm3/s are achieved, whilst typically removing up to 1mm depth of material in total. Results show a RMS form error of <1μm, with subsurface damage <10μm, and a production cycle time under 2Item Open Access Light source selection for a solar simulator for thermal applications: A review(Elsevier, 2018-04-24) Tawfik, Mohamed M.; Tonnellier, Xavier; Sansom, Christopher L.Solar simulators are used to test components and systems under controlled and repeatable conditions, often in locations with unsuitable insolation for outdoor testing. The growth in renewable energy generation has led to an increased need to develop, manufacture and test components and subsystems for solar thermal, photovoltaic (PV), and concentrating optics for both thermal and electrical solar applications. At the heart of any solar simulator is the light source itself. This paper reviews the light sources available for both low and high-flux solar simulators used for thermal applications. Criteria considered include a comparison of the lamp wavelength spectrum with the solar spectrum, lamp intensity, cost, stability, durability, and any hazards associated with use. Four main lamp types are discussed in detail, namely argon arc, the metal halide, tungsten halogen lamp, and xenon arc lamps. In addition to describing the characteristics of each lamp type, the popularity of usage of each type over time is also indicated. This is followed by guidelines for selecting a suitable lamp, depending on the requirements of the user and the criteria applied for selection. The appropriate international standards are also addressed and discussed. The review shows that metal halide and xenon arc lamps predominate, since both provide a good spectral match to the solar output. The xenon lamp provides a more intense and stable output, but has the disadvantages of being a high-pressure component, requiring infrared filtering, and the need of a more complex and expensive power supply. As a result, many new solar simulators prefer metal halide lamps.Item Open Access Limiting travel speed in additive layer manufacturing(2013-04-16T00:00:00Z) Adebayo, Adeyinka; Mehnen, Jorn; Tonnellier, Xavier; DeRoy, R.; David, S. A.; Koseki, T.; Basdeshia, H.Wire and Arc Additive Manufacture (WAAM) is new approache to modern manufacturing. This technology has been gaining the interest of the research community due to its high deposition rate and efficiency. In Wire and Arc Additive Manufacture an increase in productivity can be achieved through the use of high weld travel speeds. However, this can be overshadowed by the so called humping effect. Humping is a defect in welding which expresses itself by the formation of humps and valleys that prevent further welding deposition operation. The generation of these defects is studied by critically examining the various weld travel speeds from different weld parameters. From the study the actual weld travel speed in which humping formation starts to appear is 0.6m/min. The effects of wire feed speed and travel speed on bead geometries are also been discussed.Item Open Access A method for assessing measurement precision and stability of optical probes(European Society for Precision Engineering and Nanotechnology, 2016-06-30) Norman, James; Tonnellier, Xavier; Morantz, PaulThe current strategy for measuring non-specular metre-scale surfaces – for instance segmented freeform optics post-grinding – in the mid- frequency bandwidths (S-filter), involves the use of contact probe based systems where measurement precision is a limiting factor. Equivalent non-contact optical probes claim accuracies up to an order of magnitude higher and could therefore improve current measurement systems. Chromatic confocal probes measure the distance to a surface using the principle of axial chromatic dispersion. The stability of a CHRocodile SE 300 μm probe was shown to be 200 ± 20 nm over an eight hour measurement period. A probe holder should be designed with a low thermal expansion material in order to thermally insulate the probe measurement for further investigation. The accuracy of the probe was assessed at the extremes of its measurement range. The maximum deviation over a 5 μm displacement was measured to be 85 nm. The entire measuring range should be investigated.Item Open Access Precision Engineering behind European Astronomy Programmes(2011-03-14T00:00:00Z) Tonnellier, Xavier; Shore, PaulThe fields of astronomy science have presented significant precision engineering challenges. Numerous solutions for these fields of science have achieved unprecedented levels of accuracy, sensitivity and sheer scale. Notwithstanding of their importance to science understanding, many of these precision engineering developments have become key enabling technologies for wealth generation and other human well-being issues. This paper provides a brief historical overview of astronomy instruments. Later, details of critical precision engineering developments that supported the establishment of leading European astronomical instruments are illustrated. Finally, significant precision engineering demands to enable future sciences programmes are introduced.Item Open Access Precision grinding for rapid fabrication of segments for extremely large telescopes using the Cranfield BoX(International Society for Optical Engineering; 1999, 2012-07-11) Tonnellier, Xavier; Morantz, Paul; Shore, Paul; Comley, Paul; Eli, Atad-Ettedgui; Dietrich, LemkeAn ultra precision large optics grinding machine, BoX®, was developed and produced at Cranfield University. BoX® offers a rapid and economic solution for grinding large off-axis aspherical and free-form optical components. Grinding high accuracy surfaces with low subsurface damage reduces subsequent polishing time. This efficient grinding process provides the capacity to grind 1.5 m parts. This paper presents an analysis of Astrositall® optical ground parts: a hexagonal 84 m radius of curvature mirror of 1 m across corners and an off-axis 350 mm diameter mirror. The 1 m hexagonal part is representative of segments under study for making extremely large telescope (ELT) segmented mirrors. The second part was machined off-axis to demonstrate free-form fabrication capability. These operations demonstrate the scalability of the rapid grinding process developed for large free-form optics. The use of an error compensation procedure improved an initial ground form accuracy to +/- 1 μm p-v over 1 metre surface. The results highlighted the effect of grinding parameters and machine dynamics on form accuracy and fabrication tItem Open Access Precision Grinding for Rapid Manufacturing of Large Optics(Cranfield University, 2009-05) Tonnellier, Xavier; Shore, Paul; Stephenson, David J.Large scale nuclear fusion and astronomy scientific programmes have increased the demand for large freeform mirrors and lenses. Thousands of one metre class, high quality aspherical optical components are required within the next five to ten years. Current manufacturing process chains production time need to be reduced from hundred hours to ten hours. As part of a new process chain for making large optics, an efficient low damage precision grinding process has been proposed. This grinding process aims to shorten the subsequent manufacturing operations. The BoX R grinding machine, built by Cranfield University, provides a rapid and economic solution for grinding large off-axis aspherical and free-form optical components. This thesis reports the development of a precision grinding process for rapid manufacturing of large optics using this grinding mode. Grinding process targets were; form accuracy of 1 m over 1 metre, surface roughness 150 nm (Ra) and subsurface damage below 5 m. Process time target aims to remove 1 mm thickness of material over a metre in ten hours. Grinding experiments were conducted on a 5 axes Edgetek high speed grinding machine and BoX R grinding machine. The surface characteristics obtained on optical materials (ULE, SiC and Zerodur) are investigated. Grinding machine influence on surface roughness, surface profile, subsurface damage, grinding forces and grinding power are discussed. This precision grinding process was validated on large spherical parts, 400 mm ULE and SiC parts and a 1 m Zerodur hexagonal part. A process time of ten hours was achieved using maximum removal rate of 187.5 mm 3 /s on ULE and Zerodur and 112.5 mm 3 /s on SiC. The subsurface damage distribution is shown to be "process" related and "machine dynamics" related. The research proves that a stiffer grinding machine, BoX, induces low subsurface damage depth in glass and glass ceramic.Item Open Access Sub-surface damage issues for effective fabrication of large optics(2008-07-14T00:00:00Z) Tonnellier, Xavier; Shore, Paul; Morantz, Paul; Baldwin, A.; Walker, D.; Yu, G.; Evans, R.A new ultra precision large optics grinding machine, BoX®has been developed at Cranfield University. BoX®islocated at the UK's Ultra Precision Surfaces laboratory at the OpTIC Technium. This machine offers a rapidand economic solution for grinding large off-axis aspherical and free-form optical components.This paper presents an analysis of subsurface damage assessments of optical ground materials produced usingdiamond resin bonded grinding wheels. The specific materials used, Zerodur®and ULE®are currently understudy for making extremely large telescope (ELT) segmented mirrors such as in the E-ELT project.The grinding experiments have been conducted on the BoX®grinding machine using wheels with grits sizes of76 μm, 46 μm and 25 μm. Grinding process data was collected using a Kistler dynamometer platform. Thehighest material removal rate (187.5 mm3/s) used ensures that a 1 metre diameter optic can be ground in lessthan 10 hours. The surface roughness and surface profile were measured using a Form Talysurf. The subsurfacedamage was revealed using a sub aperture polishing process in combination with an etching technique.These results are compared with the targeted form accuracy of 1 μm p-v over a 1 metre part, surface roughnessof 50-150 nm RMS and subsurface damage in the range of 2-5 μm. This process stage was validated on a 400mm ULE®blank and a 1 metre hexagonal ZeItem Open Access Subsurface damage in precision ground ULE® and Zerodur® surfaces(Optical Society of America (OSA), 2007-09-17T00:00:00Z) Tonnellier, Xavier; Morantz, Paul; Shore, Paul; Baldwin, A.; Evans, R.; Walker, D. D.The total process cycle time for large ULE®and Zerodur®optics can be improved using a precise and rapid grinding process, with low levels of surface waviness and subsurface damage. In this paper, the amounts of defects beneath ULE®and Zerodur®surfaces ground using a selected grinding mode were compared. The grinding response was characterised by measuring: surface roughness, surface profile and subsurface damage. The observed subsurface damage can be separated into two distinct depth zones, which are: ‘process’ and ‘machine dynamicsItem Open Access Surface quality of a 1m Zerodur part using an effective grinding mode(2012-07-11) Tonnellier, Xavier; Shore, Paul; Morantz, Paul; Orton, D.; Roland, GeylA new ultra precision large optics grinding machine, BoX(R), has been developed at Cranfield University. This machine is located at the UK's Ultra Precision Surfaces laboratory at the OpTIC Technium, North Wales. This machine offers a rapid and economic solution for grinding large off-axis aspherical and free-form optical components. This paper presents an analysis of surface and subsurface damage assessments of Zerodur(R) ground using diamond resin bonded grinding wheels. Zerodur(R)was tested as it is one of the materials currently under study for making extremely large telescope (ELT) segmented mirrors such as in the E- ELT project. The grinding experiments have been conducted on the BoX(R) grinding machine using wheels with grit sizes of 76 μm, 46 m and 25 μm. The highest material removal rate (187.5 mm3/s) used ensures that a 1 metre diameter optic can be ground in less than 10 hours. The surface roughness and surface profile were measured using a Form Talysurf. The subsurface damage was revealed using a sub aperture polishing process in combination with an etching technique on small parts. These results are compared with the targeted form accuracy of 1 μm p- v over a 1 metre part, surface roughness of 50-150 nm RMS and subsurface damage in the range of 2-5 μm. This process stage was validated on a 1 metre hexagonal Zerodur(R)pItem Open Access Theoretical and experimental analysis of an innovative dual-axis tracking linear Fresnel lenses concentrated solar thermal collector(Elsevier, 2017-06-21) Perini, Simoni; Tonnellier, Xavier; King, Peter; Sansom, Christopher L.Linear concentrating solar thermal systems offer a promising method for harvesting solar energy. In this paper, a model for a novel linear Fresnel lens collector with dual-axis tracking capability is presented. The main objective is to determine the performance curve of this technology by means of both experiment and theoretical analysis. A mathematical model including the optical model of the concentrator and the heat transfer model of the receiver pipe was developed. This tool was validated with experimental data collected using a proof of concept prototype installed in Bourne, UK. The performance curve of the collector was derived for temperatures between 40 °C and 90 °C. The results show that the global efficiency of the collector is limited to less than 20%. The energy losses have been analysed. The optical losses in the lens system accounts for 47% of the total energy dissipated. These are due to absorption, reflection and diffraction in the Fresnel lenses. Furthermore manufacturing error in the lens fabrication has to be considered. One third of the solar radiation collected is lost due to the low solar absorptance of the receiver pipe. Thermal radiation and convection accounts for 6% of the total as relatively low temperatures (up to 90 °C) are involved. In order to increase the performance of the system, it is recommended to install an evacuated receiver and to insulate the recirculation system. Considering data from manufacturers, these improvements could increase the global efficiency up to 55%. Utilising the results from this work, there is the intention of building an improved version of this prototype and to conduct further tests.Item Open Access Thermal effects compensation and associated uncertainty for large magnet assembly precision alignment(Elsevier, 2019-06-12) Doytchinov, Iordan; Shore, Paul; Nicquevert, Bertrand; Tonnellier, Xavier; Heather, A.; Modena, MicheleBig science and ambitious industrial projects continually push technical requirements forward beyond the grasp of conventional engineering techniques. An example of these are the extremely tight micrometric assembly and alignment tolerances required in the field of celestial telescopes, particle accelerators, and the aerospace industry. Achieving such extreme requirements for large assemblies is limited, largely by the capability of the metrology used, namely, its uncertainty in relation to the alignment tolerance required. The current work described here was done as part of Maria Curie European research project held at CERN, Geneva. This related to future accelerators requiring the spatial alignment of several thousand, metre-plus large assemblies to a common datum within a targeted combined standard uncertainty (uctg(y)) of 12 μm. The current work has found several gaps in knowledge limiting such a capability. Among these was the lack of uncertainty statements for the thermal error compensation applied to correct for the assembly's dimensional instability, post metrology and during assembly and alignment. A novel methodology was developed by which a mixture of probabilistic modelling and high precision traceable reference measurements were used to quantify the uncertainty of the various thermal expansion models used namely: Empirical, Finite Element Method (FEM) models and FEM metamodels. Results have shown that the suggested methodology can accurately predict the uncertainty of the thermal deformation predictions made and thus compensations. The analysis of the results further showed how using this method a ‘digital twin’ of the engineering structure can be calibrated with known uncertainty of the thermal deformation behaviour predictions in the micrometric range. Namely, the Empirical, FEM and FEM metamodels combined standard uncertainties ( uc(y) ) of prediction were validated to be of maximum: 8.7 μm, 11.28 μm and 12.24 μm for the studied magnet assemblies.Item Open Access Towards the development of the supply chain of concentrated solar power(International Federation of Logistics and SCM Systems, 2016-07-29) Tjahjono, Benny; Martinez-Conde Moreno, Javier; Tonnellier, Xavier; Schaeffer, Roberto; Portugal-Pereira, JoanaThis work focuses on the investigation into the planning of renewable energy power plants in Brazil using the Concentrated Solar Power (CSP) technology. The main aim of the paper is to present an analysis of the planning process that can be used as a basis of the development of a method to assess the Brazilian’s local manufacturing and supply chain capabilities in supporting the deployment of the CSP technology. The paper identifies areas in which the concerted efforts should be emphasized. For this, the paper will first discuss the key components of the chosen CSP technology (in this case the parabolic through). The manufacturing processes of these components will subsequently be analyzed and the key enabling technologies will be determined. The demands of electricity will be estimated using the System Advisory Model®, a modelling tool developed by the National Renewable Energy Laboratory (NREL). An assessment method will finally be proposed to identify the potentials of the local Brazilian supply chain, through the readiness evaluation of the key enabling technologies and manufacturing processes.