Browsing by Author "Tonnellier, Xavier P."

Now showing 1 - 6 of 6
  • Thumbnail Image
    ItemOpen Access
    Alignment measurements uncertainties for large assemblies using probabilistic analysis techniques.
    (2017-12) Doytchinov, Iordan; Tonnellier, Xavier P.; Almond, Heather
    Big science and ambitious industrial projects continually push forward with technical requirements beyond the grasp of conventional engineering techniques. Example of those are ultra-high precision requirements in the field of celestial telescopes, particle accelerators and aerospace industry. Such extreme requirements are limited largely by the capability of the metrology used, namely, it’s uncertainty in relation to the alignment tolerance required. The current work was initiated as part of Maria Curie European research project held at CERN, Geneva aiming to answer those challenges as related to future accelerators requiring alignment of 2 m large assemblies to tolerances in the 10 µm range. The thesis has found several gaps in current knowledge limiting such capability. Among those was the lack of application of state of the art uncertainty propagation methods in alignment measurements metrology. Another major limiting factor found was the lack of uncertainty statements in the thermal errors compensations applied to assembly’s alignment metrology. A novel methodology was developed by which mixture of probabilistic modelling and high precision traceable reference measurements were used to quantify both measurement and thermal models compensation uncertainty accurately. Results have shown that the suggested methodology can accurately predict CMM specific measurement uncertainty as well as thermal drift compensation made by empirical, FEM and FEM metamodels. The CMM task-specific measurement uncertainties made at metrology laboratory were validated to be of maximum 7.96 µm (1σ) for the largest 2 m assemblies. The analysis of the results further showed how using this method a ‘virtual twins’ of the engineering structures can be calibrated with the known uncertainty of thermal drift prediction behaviour in the micrometric range. Namely, the Empirical, FEM and FEM Metamodels uncertainties of predictions were validated to be of maximum: 8.7 µm (1σ), 11.28 µm (1σ) and 12.24 µm (1σ).
  • Thumbnail Image
    ItemOpen Access
    Characterisation of integrated WAAM and machining processes
    (Cranfield University, 2013-12) Adebayo, Adeyinka; Mehnen, Jorn; Tonnellier, Xavier P.
    This research describes the process of manufacturing and machining of wire and arc additive manufactured (WAAM) thin wall structures on integrated and non¬integrated WAAM systems. The overall aim of this thesis is to obtain a better understanding of deposition and machining of WAAM wall parts through an integrated system. This research includes the study of the comparison of deposition of WAAM wall structures on different WAAM platforms, namely an Integrated SAM Edgetek grinding machine, an ABB robot and a Friction Stir Welding (FSW) machine. The result shows that WAAM is a robustly transferable technique that can be implemented across a variety of different platforms typically available in industry. For WAAM deposition, a rise in output repeatedly involves high welding travel speed that usually leads to an undesired humping effect. As part of the objectives of this thesis was to study the travel speed limit for humping. The findings from this research show that the travel speed limit falls within a certain region at which humping starts to occur. One of the objectives of this thesis was to study the effect of lubricants during sequential and non-sequential machining/deposition of the WAAM parts. Conventional fluid lubricants and solid lubricants were used. In addition, the effect of cleaning of deposited wall samples with acetone was also studied. 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.
  • Thumbnail Image
    ItemOpen Access
    A concentrated solar still for community scale desalination.
    (2018-08) Bahrami, Mohammadali (Parsa); Sansom, Christopher L.; Tonnellier, Xavier P.
    Water and energy are two main basic elements that human lives are dependent on to improve our life standards. Unreliability and a lack of safe drinking water source constitute a major difficulty in developing countries. Among many water purification technologies, solar desalination/distillation has become one of the best solutions as the most attractive and sustainable method to supply drinkable water in remote areas at reasonable cost for future generations. Seawater desalination technologies needed substantial amount of energy in order to convert brackish water into drinkable water. Thus, an extensive research on many desalination technologies has taken place in the last few decades, and solar desalination technology has become one of the most favourable sustainable methods to provide fresh water of sufficiently high quality for human communities. However, this method is not commercialized yet due to its low productivity, but improving this t has become a great source of interest for many researchers. A solar still consumes direct solar energy to produce distilled water through evaporation and condensation process of brackish water. Much research has been conducted in order to increase the productivity, but the outcomes mostly require complex components and a notable increase in cost. Consequently, developing a productive, compact, easy to operate and reasonable cost solar distillation unit was the main challenge in this body of work. A comprehensive literature review is presented in order to illustrate different modifications and their properties on the productivity of solar stills. Even though there are considerations, which cannot be controlled by human intervention (such as meteorological parameters), design and operational factors could make a direct influence on the productivity of the solar still. A novel transportable single basin, double slope shape solar still, enhanced with an internal ventilation fan connected to a copper material heat exchanger, was designed and built without forsaking its basic remit order to increase both evaporation and condensation process. The unit was also designed to use two linear focused Fresnel lenses as a solar radiation concentrator to direct radiation onto the top of solar still basin area. A detailed comparison of theoretical and laboratory experimental results were obtained for the present solar still to find the influence of different modification factors to the present solar still productivity. The temperatures of different parts of the solar still unit such as basin water, top cover glasses, heat exchanger condenser etc. were measured to evaluate different modifications including different fan airflow ratios, with and without a fan shroud, and lava stone effects to the distillate water output. The results presented an increase in productivity of 25.73% in comparison with a conventional solar still, by using a ventilation exhaust fan at its maximum airflow. Also an increase of 16.3% was also achieved by using lava stone as a heat storage material in the basin area.
  • Thumbnail Image
    ItemOpen Access
    A laser-based multilateration system for measurement of metre-scale low-slope freeform non-specular surfaces.
    (Cranfield University, 2019-02) Norman, James P.; Tonnellier, Xavier P.; Giusca, Claudiu
    The manufacture of metre–scale mirror segments for telescopes requires measurement with low uncertainty to enable accurate form correction. The uncertainty of this measurement has a direct effect upon the time to manufacture these segments; it is therefore critical, to the viability of large optic manufacture, that a method for low uncertainty measurement of these surfaces is developed and evaluated. The state-of-the-art system for measurement of metre–scale surfaces has a length measurement uncertainty of 1.2 µm over 1 m. Multilateration is a method for determining Cartesian coordinates of measured positions utilising range displacement measuring stations. A four laser tracker multilateration system has been proposed and tested with the aim to determine whether a system can measure the specified surfaces with measurement uncertainties below 1 µm. Influence factors that affect the multilateration input parameters have been identified and utilised in Monte Carlo simulation of the multilateration system to estimate the uncertainty associated with the coordinate measurement. A small flat optic (0.2 m 0.2 m) was measured with the multilateration measurement setup to have z-coordinates with a standard deviation, σz = 0.25 µm, and a large flat optic (0.4 m 0.4 m) was measured with the multilateration measurement setup to have z-coordinates with a standard deviation, σ∆ z = 0.73 µm. The 10 x 10 point multilateration measurement of the large optic was repeated 10 times; the 100 points on the surface have a square root mean variance, σz = 0.46 µm. Monte Carlo simulations indicate the independence of measurement area and measurement noise for the experimental setup tested. It is concluded that a laser–based multilateration system can measure a metre–scale optic with z-coordinate measurement uncertainty below 1 µm. A 15.5 h measurement of the larger flat was carried out to determine the effect of time dependent parameters on measurement uncertainty. The measurement solution had a standard deviation of 1.88 µm: a factor of approximately 2.4 times the equivalent short–term multilateration measurement solution. Simulations have shown how this measurement drift is strongly related to temperature change in the local environment of the measurement setup. This has been confirmed by long–term measurements of laser tracker stationary SMR.
  • Thumbnail Image
    ItemOpen Access
    Robotic polishing of large optical components
    (Cranfield University, 2014-08) Chen, Sulei; Tonnellier, Xavier P.; Comley, Paul
    Lightweight space mirrors have been widely used in earth observation and astronomy applications. Many organizations and companies, such as NASA in America, ESA in Europe, SSTL in UK as well as CASC in China, have spent a lot of money and effort on researching new materials for larger size space mirrors to meet both the payload weight constraints of launch and the increased advanced manufacturing process demanded for higher observations quality. This project is aimed at robot neutral polishing of lapped, ground and polished optical substrates using an industrial FANUC robot system. The project focused on three main fields which were: robot polishing with polyurethane tool and cerium oxide, pitch polishing with pitch tool and cerium oxide, as well as polishing of a 400mm ULE component. The polishing process targets were to achieve: 1) a surface roughness (Ra) of 10 nm and a surface profile (Pt) of 6 µm and 2µm on lapped and ground substrates respectively with polyurethane based tools and 2) a surface roughness (Ra) of 2nm with a surface profile (Pt) unchanged on robot neutral polished substrates using pitch based tools. This thesis comprises four main sections: a literature review, an experimental implementation, metrology and analysis, and the final conclusions. The experiment results measured with the metrology equipment selected were analysed. Conclusions of the relationship between the polishing performance of a specific sample and the selected polishing tool, polishing slurry, tool pressure, polishing time and other parameters were drawn. Results obtained from robot neutral polishing were surface roughness (Ra) of 8-10nm and surface profile (Pt) of 6µm for 100mm square lapped and ground parts. The process scalability was demonstrated from robot neutral polishing in 45hours, a 400mm square ground component from a surface roughness (Ra) of 200nm to 10nm. There is additional work to be implemented in the future, such as the development of robot pitch polishing of robot neutral polished parts to achieve 2nm Ra.
  • Thumbnail Image
    ItemOpen Access
    Selected area hot machining with a multi-tipped diamond tooling system.
    (2017-09) Dennis, Ashley; Goel, Saurav; Tonnellier, Xavier P.
    An investigation of a novel ultra-precision tool is presented, the hot-milling multi-turret diamond tool. The tool implements micro-Laser Assisted Machining (μ-LAM) upon a multiple diamond fly cutter. Details of its design, both mechanical and optical, are presented- along with proposed modifications to Cranfield University’s Tetraform C machine to allow for its implementation. Relevant experimentation is presented- the modal analysis of the Tetraform C machine and the testing of laser heating on a silicon substrate. FE analyses are carried out and calculations presented to justify design choices. Analytical investigations predicted increased depths of cut by using laser, and indicated that at lower wavelengths of laser light and with lower feed rates that the depth of cut may be significantly increased. A novel method of selecting laser wavelength based upon change in material absorptivity with temperature is investigated which may offer substantial increases in μ-LAM performance