Browsing by Author "Wimpenny, D. I. (David I.)"
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Item Unknown Additive manufacturing by electrophotography: Challenges and successes.(2010) Jones, Jason B.; Wimpenny, D. I. (David I.); Gibbons, G. J. (Greg); Sutcliffe, C.Item Unknown Allosteric control model of bone remodelling containing periodical modes.(Elsevier, 2007-05-01) Moroz, Adam; Wimpenny, D. I. (David I.)To help to understand the modelling process that occurs when a scaffold is implanted it is vital to understand the rather complex bone remodelling process prevalent in native bone. We have formulated a mathematical model that predicts osteoactivity both in scaffolds, as well as in bone in vivo and could set a basis for the more detailed allosteric models. The model is extended towards a bio-cybernetic vision of basic multicellular unit (BMU) action, when some of the regulation loops have been modified to reflect the allosteric control mechanisms, developed by Michaels–Menten, Hill, Koshland–Nemethy–Filmer, Monod–Wyman–Changeux. By implementation of this approach a four-dimensional system was obtained that shows steady cyclic behaviour using a wide range of constants with clear biological meaning. We have observed that a local steady state appears as a limiting cycle in multi-dimensional phase space and this is discussed in this paper. Physiological interpretation of this limiting four-dimension cycle possibly related to a conservative-like value has been proposed. Analysis and simulation of the model has shown an analogy between this conservative value, as a kind of substrate-energy regenerative potential of the bone remodelling system with a molecular nature, and to the classical physical value — energy. This dynamic recovery potential is directed against both mechanical and biomechanical damage to the bone. Furthermore, the current model has credibility when compared to the normal bone remodelling process. In the framework of widely recognised Hill mechanisms of allosteric regulation the cyclic attractor, described formerly for a pure cellular model, prevails for different forms of feedback control. This result indicates the viability of the proposed existence of a conservative value (analogous to energy) that characterises the recovery potential of the bone remodelling cycle. Linear stability analysis has been performed in order to determine the robustness of the basic state, however, additional work is required to study a wider range of constants.Item Unknown Bone tissue remodelling – the local and systemic control and mathematical modelling.(UNESCO, 2010) Wimpenny, D. I. (David I.); Moroz, Adam; Tallis, AndreaItem Unknown Customised rapid manufactured parts: technology and case studies from the custom-fit project.(2008-10-21) Jones, Jason B.; Wimpenny, D. I. (David I.)The design and manufacture of products which are individually customised to the precise requirement of the user, including anatomical matching, is generally restricted to bespoke clothing or footwear for very wealthy customers. The aim of the EU FP6 CUSTOM-FIT project is to develop a fast, flexible and economically viable route for the manufacture of individually customised parts. These products not only provide improved comfort levels but also provide better functional performance, including enhanced safety for the user. This 4.5 year , €16m project involves over 30 partners across the breadth of the Europe is now in its final year and this presentation will showcase the technology developed, including new body scanning technology, CAD packages which automate the design process and new rapid manufacturing methods and materials. The presentation will include case studies on a range of customised products, including customised seats for Ducati Motorcycles. The case studies not only demonstrate the performance benefits of individual customisation but also show the potential for new approaches to product design including both functionally graded structures and materials to achieve precise control of product performance.Item Unknown Customised rapid manufactured parts: Technology and case studies from the custom-fit project.(2009-12-01) Jones, Jason B.; Wimpenny, D. I. (David I.)The design and manufacture of individually customised products is generally restricted to bespoke clothing or footwear for very wealthy customers. The aim of the Custom-Fit project is to develop a fast, flexible and economically viable route for the manufacture of individually customised parts. These products not only provide improved comfort levels but also provide better functional performance, including enhanced safety for the user. This 4.5 year, €16m project involving 30 partners across the breadth of the Europe finished last month. This presentation will showcase the technology developed: CAD packages which automate the design process and three new rapid manufacturing methods. The presentation includes case studies on a range of customised products, including customised seats for Ducati Motorcycles. The case studies not only demonstrate the performance benefits of individual customisation but also show the potential for new approaches to product design including both functionally graded structures and materials to achieve precise control of product performance.Item Open Access Gateways Toward Dissimilar Multi-material Parts(Society of Manufacturing Engineers, 2012-08) Jones, Jason B.; Cooper, David E.; Wimpenny, D. I. (David I.); Gibbons, G. J. (Greg)Nature provides a pattern of complex systems in which materials with vastly dissimilar properties grow together and function in close proximity. Although the gap between biological and existing AM systems cannot be overstated, the aspiration for AM to mimic this capability of nature has been widely admired (but is currently limited to multi-material parts made from families of like materials). The recent ASTM F2921 standard provides the first standardized framework to identify anisotropic properties of printed parts. This research highlights how understanding and quantifying the anisotropies between and within layers of printed parts provides foundational understanding to begin to emulate nature’s pattern by consolidating dissimilar multi-material parts in AM which promises future potential to supersede conventional part assembly with integral printed systems.Item Metadata only Laser printed elastomeric parts and their properties.(2009-12-01) Wimpenny, D. I. (David I.); Banerjee, Soumya; Jones, Jason B.The precise deposition of polymeric toner powder by laser printing is reliant on having powder particles with appropriate flow and uniform charge properties. Nanometer sized particles known as flow control agent (FCA) charge control agents (CCA) are used to modify powder behavior to provide the appropriate characteristic for printing. This paper shows how varying the quantity of FCA/CCA applied to the surface of Somos201 particles can affect the elongation to failure and ultimate tensile strength of laser printed tensile test specimens.Item Metadata only Metal spray tooling for composite forming.(Elsevier, 2003-01-01) Wimpenny, D. I. (David I.); Gibbons, G. J. (Greg)Thermal spraying methods have been mooted as a method of manufacturing tooling for many years and yet they have not made a significant in-road into this market. Generally, recent metal spraying research has focussed on the manufacture of small, high-pressure tools (for example, for automotive injection moulding tools). However, the metal spray process really lends itself to the manufacture of large tooling where it can compete more effectively against alternatives such as machining. The 3-year, £ 750k, IMI Spray Mould Programme, funded jointly by EPSRC (IMI) and the industrial partners: Airbus, BAE SYSTEMS, Bombardier Aerospace Shorts, A.T. Poeton, Rover Group, and Sulzer Metco, commenced in June 1997. The aim of this research is to develop a method of manufacturing tooling for composite aerospace components, particularly large primary structures over 15 m in length. This paper will present the results of this research programme, including technical data comparing both the technical and economic advantages of this novel approach to tool construction.Item Metadata only On the variational framework employing optimal control for biochemical thermodynamics.(Elsevier, 2011) Moroz, Adam; Wimpenny, D. I. (David I.)Item Metadata only Phenomenological model of bone remodeling cycle containing osteocyte regulation loop.(Elsevier, 2006-01-01) Moroz, Adam; Crane, Martin C.; Smith, Geoff; Wimpenny, D. I. (David I.)Item Metadata only Printed Circuit Boards by Selective Deposition and Processing(University of Texas, 2011-08) Jones, Jason B.; Wimpenny, D. I. (David I.); Chudasama, Rupesh; Gibbons, G. J. (Greg)With electronic applications on the horizon for AM, comes the dilemma of how to consolidate conductors, semi-conductors, and insulators in close proximity. To answer this challenge, laser printing (selective deposition) was used in tandem with fiber laser consolidation (selective processing) to produce PCBs for the first time. This combination offers the potential to generate tracks with high mechanical integrity and excellent electrical conductivity (close to bulk metal) without prolonged exposure of the substrate to elevated temperatures. Herein are the findings of a two-year feasibility study for a “one-stop” solution for producing PCBs (including conductive tracks, dielectric layers, protective resists, and legends).Item Metadata only Rapid laminated tooling.(Elsevier, 2003-01-01) Wimpenny, D. I. (David I.); Bryden, B. (Brian G.); Pashby, I. R. (Ian R.)Item Metadata only Rapid manufacturing of bioceramic implants by direct writing.(2008-09-18) Tallis, Andrea; Jones, Jason B.; Wimpenny, D. I. (David I.)Abstract: A new process for the manufacture of customised implants for replacing damaged or diseased bone is being developed at DMU under a UK Government funded project – TSB Direct Writing of Bioceramic Implants. The new process is based on the extrusion of a fine bead of colloidal slurry which is then rapidly cooled to below -40oC to initiate an irreversible freeze casting reaction. When the slurry is returned to room temperature it remains a brittle solid which can be fired at elevated temperatures to generate the required mechanical properties. By sequentially depositing layers of material it is possible to generate a complex 3D object which has an internal lattice structure which enables rapid integration of the implant with the surrounding natural bone to produce a secure, long lasting repair. In this paper the results extrusion and freeze casting trials will be presented and discussed.Item Metadata only Rheological Properties of HA Slurry for the Production of Bone Scaffolds by Layer Manufacturing(2007) Jones, Jason B.; Tallis, Andrea; Tillotta, V.; Moroz, Adam; Wimpenny, D. I. (David I.)In recent years, innovative methods have been developed for the repair and regeneration of damaged and diseased bone tissue. Ceramic bio-scaffolds provide advantageous features as compared to other materials. The potential exists to use a slurry* composed of silica and hydroxyapatite (HA) which can be extruded through a controlled rate/pressure nozzle for rapid and accurate manufacturing of the green body of the scaffold. In order to fine-tune the slurry to be used in this process analysis of the HA particles and rheological characterisation and testing of a range of slurry formulations was undertaken. The measurement of the viscosity, its time dependent behaviour and the strength of the internal structure of the slurry are vital tools to characterize the suitability of ceramic slurry for the extrusion process. A plotting trial was also conducted with the objective of examining the behaviour of the different formulations under a range of pressure/extrusion rate parameters. The composition of the slurry formulations was in the range of 30 to 40 weight % of HA and was eventually fine-tuned to 35% by weight HA, which gave the best performance from the point of view of viscosity, oscillation, and extrusion properties. It was observed that the slurries behaved in non-Newtonian, shear-dependent complex modes.Item Metadata only Transfer methods toward additive manufacturing by electrophotography(Society for Imaging Science and Technology., 2011) Jones, Jason B.; Gibbons, G. J. (Greg); Wimpenny, D. I. (David I.)Item Metadata only The use of non-contact structured light scanning in burns pressure splint construction.(Elsevier, 2011) Pilley, M. J.; Hitchens, C.; Rose, G.; Alexander, S.; Wimpenny, D. I. (David I.)