/library/oar/handle/123456789/12099 2025-12-28T17:48:15Z /library/oar/handle/123456789/70811 Title: Digital factory planning for a range of products : a changeability knowledge-based integrated product development approach Abstract: Due to highly competitive markets, constantly shifting consumer requirements, and technological advances, product ranges are continuously evolving over time. This product evolution leads to new part variants being added to the existing part mix. Manufacturing changeability concepts such as flexibility and reconfigurability have been developed by existing research in order to design Changeable Manufacturing System (CMS) which are capable of evolving with the evolving product ranges. Factory planning, in particular CMS design decisions, can result in consequences on the future manufacturing capability (MCCs) of the manufacturing system, to manufacture the evolved part variants. Furthermore CMS design decisions can also result in consequences on the factory changeability (FCCs) which would limit the capability of the manufacturing system to economically and feasibly evolve with the evolving product ranges. This phenomena is being termed as disruptive product evolution. Due to complex interdependencies, incomplete information and uncertainty in CMS requirements this phenomena leads to a wicked problem. Moreover, a literature review established that designers currently lack the means which make them aware of MCCs and FCCs and support them in exploring different CMS design solutions. To address this problem, this PhD research proposes, implements and evaluates a changeability knowledge-based CMS design approach framework. The establishment of a phenomena model discloses how disruptive product evolution can occur from two different conditions; MCCs and FCCs. This phenomena model provided a basis for how to model and timely utilise changeability knowledge for revealing MCCs and FCCs during the exploratory CMS design activity. This was then utilised by the CMS design approach framework which supports manufacturing system designers in becoming aware of CMS decision consequences by revealing the interactions between business strategies, evolving product ranges and manufacturing systems decisions. A prototype digital factory design tool based on the underlying concepts of the CMS design approach framework has been developed and implemented. The encouraging results obtained have shown that this PhD research paves the way for the development and integration of such knowledge-based CMS design approaches within state of the art digital factory tools. Description: PH.D 2016-01-01T00:00:00Z /library/oar/handle/123456789/70810 Title: An investigation and optimisation study on the structural performance of filament wound GRP pressure vessels Abstract: Filament wound composite pressure vessels and pipes are tailored to cater for specific needs and the design phase is usually the crucial factor for the successful implementation of these novel materials. According to the European standard EN 13923:2005, the ultimate pressure of glass-fibre reinforced polymer (GRP) filament wound pressure vessels is defined by the first occurrence of failure. There is no definitive way how to detect the onset of failure during a pressurisation test therefore, a methodology involving the monitoring of the mid-span expansion, backed up by strain measurements, to capture both the first ply failure and the successive behaviour leading to the ultimate failure of the vessels, was proposed. The methodology was successfully implemented in a set of pressurisation tests performed on e-glass reinforced polyester filament wound pressure vessels. From an analytical point of view, it was shown that utilising the classical laminate theory (CLT), together with the stress resultants as indicated by the standard EN 13923:2005, is not adequate to predict the stress-state of unsymmetric and/or unbalanced cylindrical laminates. Ideally, the use of finite elements software or closed solutions, where available, should be encouraged. Furthermore, modelling the actual failure progression of a filament wound cylindrical pipes post the FPF load utilising a progressive failure analysis (PFA) based on a failure mode dependent sudden degradation methodology, is not sufficient. A novel method to overcome this shortcoming was proposed where initial imperfections are introduced systemically in the geometry or the material properties based on the void fractions of the specimens used in the material characterisation tests. The novel method creates a link between the manufacturing induced inhomogeneities and the numerical model, thus improving significantly the predicted behaviour both quantitatively and qualitatively. A study on the implementation of the novel Big Bang – Big Crunch (BB-BC) optimisation procedure to optimise filament wound pressure vessels composed of different types of layers is presented. The BB-BC methodology is able to find the global extremum although care should be taken when choosing the population size and the β parameter. Higher population sizes increase the algorithm robustness in finding the global extremum, whilst favouring the fittest solution while creating subsequent populations is essential for objective functions with local extrema. Description: PH.D 2016-01-01T00:00:00Z /library/oar/handle/123456789/70809 Title: Modelling and analysis of hydraulic wind turbines with integrated energy storage Abstract: In the present work, a refrigeration cycle model is developed to quantify the benefits of using deep seawater from below the thermocline. The model showed a Coefficient Of Performance (COP) improvement of 37.5% when using deep seawater instead of surface seawater. It also showed that the integration of an energy storage device into the hydraulic wind turbine allows it to provide a more consistent supply of cold deep seawater. This results in the refrigeration cycle providing more stable delivery temperatures and a marginal increase in COP. When the hydraulic wind turbine operates in higher wind climates, it was also observed that mixing some surface seawater to compensate for deficits in the wind-driven deep seawater flow is not significantly detrimental to the system performance. In lower wind scenarios, the mixing process can have a more negative effect on the COP. Nonetheless, it is still higher than that observed in coastal systems operating on only surface seawater. Overall, the electrical energy saving resulting from the use of cold deep seawater adds around 7% to the hydraulic wind farm yield. This more than compensates for the higher transmission losses associated with hydraulic wind turbines. Description: PH.D 2017-01-01T00:00:00Z /library/oar/handle/123456789/15757 Title: Structural evaluation and testing of a multi-bladed wind turbine prototype Abstract: Alternative energy sources have become much more necessary as fossil fuels are being depleted and pollute the environment. Wind energy is one of the cleanest and effective of all types of renewable energy. This is the driving force which led to the creation of this project. The Chicago type wind pump was introduced to the Maltese countryside with the main purpose to pump water from the aquifer which is then stored in reservoirs. Most of these wind pumps are no longer utilised because of the introduction of the electric water pump and grid availability. For this reason most of these wind pumps were abandoned and became useless. This fact provided the necessary motivation by which these unused wind pumps would be replaced to generate clean electricity. This included the design and construction of a new prototype of a wind turbine system. The objective of this project was to continue on the previous work done on the concept wind turbine. An elaborate structural analysis was carried out to check if the supporting structure is adequate. Any identified design deficiencies were noted and modified, so that the structure would meet the required design standard guidelines. Further to this, the supporting structure was subjected to a full-scale load test, which verified that the structure can withstand the design loads. Additional functions and sensors were designed and implemented onto the wind turbine. Following this, it was transported and installed at the location where it was tested. During this operation, management and health and safety measures were of utmost importance. Subsequent to this, the turbine was tested under local conditions. Promising results from initial testing proved that the wind turbine is efficient to convert wind energy into electrical energy. Its performance was found to be comparable to that of commercial wind turbines. This prototype proved to achieve a balanced design between the aesthetics of the old Chicago Wind Pump, coupled with efficient aerodynamic and structural performance. Further design improvements were suggested based on the testing results. Description: M.SC.MECH.ENG. 2016-01-01T00:00:00Z