Browsing by Author "Clark, G."
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Item Open Access Machined part cost estimating in SMEs: a feature-driven case-based approach(Cranfield University, 2010-03) Dimmock, S. I.; Greenough, Richard; Tjahjono, Benny; Clark, G.; Hadley, S. J.This thesis describes the application of a novel decision support process for machined part estimating in small and medium-sized engineering companies. Many SMEs tend to adopt manual estimating techniques, however this dependence on human expertise represents a risk to such organizations. Better information management in estimating can improve process performance and contribute to increased competitiveness. The research which is the subject of this thesis investigated whether a systems approach to machined part estimating would extend the capacity of an SME to manage knowledge more effectively. The research explored the workplace learning context, the provision of learning opportunities and the management of organizational knowledge; before determining that an intelligent information system offered the most beneficial solution to the situation-of-interest. The case study company produce low-volume, make-to-order, medium and large sized machined steel forgings; utilising conventional machine tool equipment. The application of the decision support system enabled novice estimators to produce viable cost estimates; reducing the risk from reliance on human expertise inherent in manual estimating. The hybrid feature-based costing / case-based reasoning estimating technique, which is the core of the novel METALmpe cost model, proved exceptionally well suited to the SME environment. Estimates produced using METALmpe were consistently more accurate than those of the human expert; with a level of accuracy that exceeds the initial research aim, i.e. a tolerance of -5% / +10%. Significantly, implementation of METALmpe (hardware, software and support for 5 users), can be provided at a cost which is within the typical information technology budget of many SMEs. With demands on organizations to process and disseminate ever increasing volumes of information, METALmpe can improve an SME’s information management capabilities and contribute to competitive advantage through strengthening strategic assets and core competencies.Item Open Access Multidisciplinary optimisation of a CFRP wing cover(Cranfield University, 2009) Phillips, Benjamin John; Guo, Shijun J.; Fielding, John; Clark, G.With the market introduction of both the Airbus A350XWB and the Boeing 787, Carbon Fibre Reinforced Plastics (CFRP) has been applied to primary structure of large commercial aircraft, as a means of enhancing overall performance. Both these aircraft are being developed and produced in a unique way where Airbus and Boeing are acting as System Integrators and using Risk Sharing Partners to develop the majority of the principal components. To support this new business and technological model it is necessary that the System Integrator has sufficient knowledge and tools to support the development of the components. Of particular interest are items such as the wing covers, as they are both heavy and expensive items, thus offering large opportunities for optimisation, in particular when the benefits of applying CFRP are considered. This creates the forum for this thesis, i.e. to thoroughly understand all factors that influence a CFRP wing cover, from which an optimisation methodology is developed, incorporating design constraints, while seeking the lightest weight solution, with a resultant Life Cycle Cost (LCC). Based on this, different solutions can be compared based on weight and LCC. In general stringer-stiffened panels are, from a weight perspective, the optimal configuration for wing covers, and thus are solely considered. Serendipitously, due to their prismatic shapes, buckling calculations of stringer-stiffened panels can be solved with reasonable accuracy and ease using the Finite Strip Method (FSM), as opposed to more time consuming methods such as the Finite Element Method. A suitable FSM program is available from ESDU, which when used in combination with a configured Excel spreadsheet can take into consideration constraints established from the extensive literature review. Once the lowest weight solution is obtained under buckling constraints, the solution is then checked for in-plane and if desired out-of-plane strength. Based on the structurally optimised wing cover, the manufacturing cost is calculated using a Process Based Cost Model (PBCM), which has been developed based on different CFRP materials for the skin and stringer fabrication, as well as suitable manufacturing and integration methods. In order to consider the LCC, i.e. all costs from cradle to grave, the PBCM factors in both the cost of recycling scrap material during manufacture and after retirement. Furthermore, when more than one solution is compared then the Economic Value of Weight Saving, which is based on the range equation, can be factored in to consider the financial benefit of weight saving. The optimisation methodology and PBCM has been evaluated on diverse wing cover examples, which has considered both uni-directional prepreg, non-crimp fabric and braids materials in combination with autoclave and liquid composite moulding techniques. The results demonstrated a trend which can be considered realistic, although the cost estimation is very much dependent on the assumptions made. In conclusion, the thesis and the optimisation methodology can be used to compare different configurations.Item Open Access Planning Product Support for Medical Products(Cranfield University, 1992-10) Goffin, Keith; New, Colin; Clark, G.Product support is a key aspect in the marketing of high-technology products, since it strongly influences customer satisfaction and can also be an important source of revenue. Typical forms of support include operator training, equipment maintenance and, if necessary, repair - all of these are normally provided by manufacturers' support organizations. Good support is particularly important in some markets; an example is medical equipment where good operator training and quick repairs are essential because products are used in critical situations. Despite its importance, support has not been extensively researched. This study describes a management investigation of two aspects. Several authors have identified that product support is dependent on product design. Consequently, the same authors emphasize that support should be thoroughly evaluated during product design. This study identifies the range of factors that may be evaluated and shows that most of the companies surveyed do not fully evaluate support during the design stage. These results are not covered by previously published material and have implications for management. As support influences customer satisfaction, it is important to know how customers perceive support. The study investigated the customer attributes of good support, using interviews with medical equipment customers. The results show that a common set of attributes are associated with support, some relating to the product itself and some to the support organization. The characteristics of products which are easier to support were also identified from the interviews. The contribution of the research is that it made an exploratory investigation of the concept product support. It not only gave the first survey data on how companies plan support but also investigated customers' perceptions of product support. Consequently the study provides a foundation from which there is real scope for further management research, into what is becoming recognized as a vital element of high-technology marketing.Item Open Access Sub-idle modelling of gas turbines: Altitude relight and windmilling(Cranfield University, 2007-10-05) Howard, Jason; Rowe, Arthur; Pilidis, Pericles; Clark, G.; Naylor, P.Gas turbine sub-idle performance modelling is still in an early development stage and this research aims to provide and improve present techniques, for modelling of windmilling and transient windmilling relights, through to groundstart simulations. Engine ATF data was studied and used to align models created within this research for low and high bypass engines, and compare these models simulation results. Methods for the extrapolation of component characteristics are improved and performed in linearised parameter form, and the most efficient approach discussed. The mixer behaviour is analysed and recommendations of off-design mixer behaviour representation in a sub-idle model are proposed and performed within the modelling. Combustion at sub-idle conditions is investigated with regards to the loading parameter definition, and also its representation for the influence of evaporation rate being limiting to overall combustion efficiency. A method is proposed on extrapolating and representation of the combustion characteristic. Compressor behaviour and the blade torques at locked rotor and windmilling conditions are studied using 3D CFD, producing insight and discussion on CFD suitability and what it can offer at these operating conditions. From the CFD studies generic loss coefficients were created for all compressor blades, from which a zero speed is created for the whole compressor, from a theoretical stage stacking calculation. This zero-speed curve is shown to allow interpolation of component characteristics to the sub-idle region, improving the definition and a predictive approach. A windmilling conditions cascade test rig is proposed, designed and built for validating the CFD loss coefficients. The findings and discussions within this thesis provide useful reference material on this complicated and little documented area of research. The modelling and methods proposed, provide great advancement of the research area, along with further integration of the Cranfield UTC in performance with Rolls-Royce.