Search

In the first of the metalforming operations considered, that of plane-strain side-pressing, the finite-element predicted deformation behaviour of 60-40 brass and 7075 aluminium alloy has been compared with experiment. Both visioplasticity and hardness studies have been performed. The macrohardness survey was found to be the most appropriate in validating the use of the finite-element technique. The numerical calculations of the local stress and strain distributions are then used with a number of previously published continuum fracture criteria to predict the fracture initiation sites. For certain of the successful criteria the level of deformation at fracture has also been predicted using critical values of fracture found experimentally from an axisymmetric tensile test. For the operation of plane-strain side-pressing, very good agreement with both the experimental fracture initiation site, and the level of deformation at fracture, is reported for the criterion of a critical value of generalised plastic strain at fracture, and the equivalent criterion of generalised plastic work. The second metalforming operation considered is simple upsetting. The fracture initiation behaviour of 60-40 brass has been examined for specimens of the four initial aspect ratios of 0.5, 1.0, 1.5 and 2.0. Again, the generalised plastic strain/work criterion has successfully predicted the experimental fracture initiation sites in all cases. However, satisfactory levels of deformation at fracture predictions have only been found for the two lower aspect ratio specimens. A small range of strip compression and tension operations on 60-40 brass compose the third type of metalforming operation considered in this thesis. Yet again the generalised plastic strain/work criterion has successfully predicted the fracture initiation site found experimentally but not the level of deformation at fracture. Finally, the axisymmetric extrusion of 60-40 brass and 7075 aluminium alloy is examined. For the brass using the generalised plastic strain/work criterion, good agreement with experiment has been found for both the fracture initiation site and level of deformation at fracture found experimentally. However, for the aluminium alloy only the correct fracture initiation site has been found. In summary, it appears that the fracture criterion of a critical value of generalised plastic strain/work has successfully predicted the fracture initiation site found experimentally in all the operations considered in this thesis but has been unable to consistently predict the correct level of deformation at fracture. These differences in the predicted and experimental level of deformation at fracture cannot be explained with reference to the finite-element calculated levels of hydrostatic stress. Further work is necessary to explain this difference.

Marine litter is considered a common concern of humankind that poses a serious risk to marine life, human health and the economy. One of the most abundant and harmful types of marine litter is abandoned, lost or otherwise discarded fishing gear. As it comprises of durable mate-rials like nylon or polyethylene it can continue to catch fish for years before it breaks down into smaller pieces. The smaller pieces can then be ingested with possibly fatal consequences. To mitigate those impacts, derelict fishing gear [DFG] is increasingly retrieved from the ocean. However, apart from landfilling there is currently no established waste treatment system to process this material in Europe. In the context of the European Interregional project MARELITT Baltic and in collaboration with WWF Germany and PreZero, this thesis investigated the retrieval and alternative waste treatment options for DFG. In total, four scenarios, namely the (1) mechanical recycling, (2) chemical recycling, (3) energy recovery and (4) disposal were evaluated to assess their poten-tial environmental impact and feasibility. For this, industrial experiments and a life cycle as-sessment (LCA) were conducted. The experiments highlighted DFG as a challenging mix of materials. Apart from large bulky items such as anchors, chains and cables, also smaller contaminants like sediments, salt and lead were contained. While this made the pre-treatment very time-consuming, a technical fea-sibility of the recycling techniques could be shown. The LCA results indicate that the mechan-ical recycling and energy recovery achieve the lowest potential environmental impacts. The chemical recycling scenario was too energy intensive to be environmentally competitive. Due to the determined lead content of up to 13.5% by weight in DFG, a disposal should be avoided as it poses a significant potential impact to human toxicity. For the establishment of a waste treatment system and as far as possible, existing infrastructure such as local incineration plants or recycling facilities for end-of-life fishing gear should be used. As this requires the setup of a pre-treatment process, harbour personnel or other stake-holders should be encouraged to conduct those tasks. Further work is required to include social, economic and possibly other aspects, before a decision on the most appropriate waste treatment system can be made. Still, given DFG’s harmful nature and challenging composition, preven-tive measures like the introduction of an extended producer responsibility scheme for fishing gear are key.

This research aims to determine whether rationalised life cycle assessment approaches (RLCAAs) are useful and suitable techniques to measure the environmental impacts of small and medium size enterprises (SMEs) from service industries. RLCAAs are simplified; less resource intensive techniques; that do not measure exclusively carbon dioxide equivalents (CO2e) but consider the wider environmental impact details. There is limited research on suitable techniques that measure the wider environmental impacts of service industry SMEs; however, with increasing pressures on accountability, it is important for businesses to recognise these impacts. This study provides an interdisciplinary assessment on such SMEs by using a range of appraisal tools and approaches and using primary data collected from owner-managers and employees. The results suggest SMEs do not adopt a strategic approach to environmental matters and that the respondent companies produce on average 70t CO2e a year. A qualitative assessment undertaken from a roundtable discussion found amongst employees concern, that using CO2e only, as a quantifying metric to gauge impacts, loses wider impact details. Life cycle assessments seek to acknowledge wider environmental impact details, are not promoted to SMEs because they are resource intensive and too complex, to be of practical use. The criticisms are pertinent relative to a ‘cradle to grave’ quantitative assessment. However, in terms of RLCAAs their specific application and benefits to SMEs is unknown Two RLCAAs were configured and tested upon three-service industry case studies; a packing, film and online distance learning establishment. One a magnitude, the other a pragmatic approach differed in the use of qualitative criteria; demonstrated by similar findings, with transport, energy and equipment identified as core emitters, less time consuming approaches can be used effectively by SMEs. In conclusion, both RLCAAs would prove useful at raising environmental awareness, assessing aspects and highlighting impacts thereby, potentially improving the sustainability of SMEs.

Electricity sector decarbonisation is widely seen as a fundamental step in the global fight against climate change. The need to secure this transition is compounded by the prospective use of electrification to deliver economy-wide carbon reductions, especially in harder to address sectors like heat and transport. No agreement has yet been reached on the best decarbonisation approach. Empirical evidence is required to guide a transition that not only succeeds in delivering a ‘truly’ low carbon electricity source, but also prevents wider environmental issues being exacerbated. This research portfolio examines the low carbon transition of electricity systems in a UK context. The energy and environmental implications in response to different decarbonisation approaches were evaluated using Life Cycle Assessment (LCA) and related methods. Potential UK low carbon electricity systems were investigated via three socio-technical energy scenarios, known as the Transition Pathways. Key factors were identified, which may impact the future environmental performance of UK electricity, such as supply chain dynamics, policy shifts, and new entrant technologies, were investigated to assess their consequences on decarbonisation targets. This research exemplifies the guiding principles of LCA as a valuable proactive tool in shaping superior future decarbonisation and wider environmental policies. A key finding of this thesis was the importance of whole life cycle accounting of power sector GHG emissions, including upstream impacts which are often overlooked by governmental bodies. Hence, current decarbonisation policies may lead to a shift in practices and the adoption of production routes with unintended negative effects upstream. In this work, the upstream gas emissions for future supplies increase significantly (rising 2.7 to 3.4 times current mix per MJ supplied) and are foreseen to be highly influential on the future electricity systems analysed. Increased influx of biomethane leads to a substantial reduction in direct fossil emissions (up to 10.6 million tonnes of CO2eq), and is found to be critical in offsetting rising upstream emissions. The roll-out of carbon capture and storage was also found to be instrumental in the success of the pathways. The electricity system transitions assessed achieved differing, yet significant, levels of decarbonisation (between 75-85% reductions on 1990 levels on a lifecycle basis). Nevertheless, these were often achieved at the expense of wider environmental impacts, suggesting trade-offs were unavoidable. The civic-led energy transition resulted in the greatest associated environmental benefits, realising the greatest reduction in 13 of 18 environmental categories assessed, compared to the 2008 levels. It was also the only pathway to decouple electricity supply from fossil fuel use. Reliance on metal resources was seen to steadily increase in response to a developing renewable energy sector, rising 23-75% from the 2008 baseline system. The presented results, models and data are transparently presented for others in the field to build upon, and scrutinise their implications for wider decarbonisation strategies within and outside of the electricity sector.

Echolocation is the primary tool dolphins depend on for their survival underwater. Without this ability, the localization of food and navigation would be much harder for the animals. This active sonar is characterised by narrow transmission and reception directivity patterns, over a variety of ranges. In Cetaceans, only toothed whales and dolphins (odontocetes) are able to echolocate. The main concept for echolocation is to emit sound and listen to the returning echoes. Where sound enters the head first and how the signals are transmitted to the mandibular fats and inner ears is not fully understood. There are several theories on how sound reaches the fatty tissues in the lower jaw: through a thin region in the lower jaw called the pan bone, through the throat region and an opening in the rear mandibles and through the teeth, acting as an end-fire array and enhancing the directional hearing. The hypothesis on sound reception via the teeth was investigated further in this thesis. The sound pressure was modelled at the teeth of a bottlenose dolphin (Tursiops truncatus) using acoustic characteristics of different components of the entire jaw. The angle of the jaw was changed from 0° to ±10° in 1 degree steps and from ±10° to ±90° in 5 degree steps. The pressure was measured at 3 front and back teeth and the difference between pressure values compared. The pressure was also measured at each of the 22 teeth on both sides of the jaw for two different angles, 0° and +5°. Multiple scattering and the influence from the relative positions and sizes of teeth as well as the effect of missing teeth was investigated. Results show that the propagation of sound varies with size and position of the teeth. The simulations display the relation between neighbouring teeth and the attenuation or amplification of the signals at other teeth. Teeth cannot be considered as individual point-like receivers. A pressure tendency can be seen at the back teeth for the first ±15°, which indicates that directional hearing occurs for the first degrees the dolphin moves its head. It also shows that hearing takes place primarily at the back of the jaw.

There are as many perspectives in designing as there have been instances in which it has occured. In each instance, constraints will have invariably arisen in various forms, to the extent that designing and constraints are considered to be an inherently natural pairing. In addition, they are both affected by the challenges of complexity, amongst many others, which is especially compounded by an increasingly significant shift towards interdisciplinary methods and means of working. This has been in response to the influences and implications with regards to the integrated elements of sustainability and sustainable development. To this effect, the body of research effort presented in this thesis searches for a simpler perspective towards designing, to which constraint-based thinking can be applied. It explores the implications of interdisciplinarity in the context of sustainability and sustainable development. It also considers an example of design-based process within the built environment that is inclusive of multiple disciplines and therefore not only interdisciplinary, but also affected by complexity. In response to these instances of complex interdisciplinary designing, this thesis contributes an exploration of constraint-based thinking and the consideration of an approach which uses design objectives as optimisation constraints, from which a methodology has been created. Furthermore, this thesis demonstrates constraints as useful in understanding, especially in the context of problem structures and their respective design spaces. As a form of constraint, optimisation objectives are also presented in this thesis as a means of exposing and handling complexity when applied as constrained optimisation for focusing designing efforts. Above all, this thesis advocates the use of constraint-based thinking and simplicity towards enhancing and supporting designing process.

Some of the most common diseases and disorders that occur in the adult population are those which affect the joints of the musculo-skeletal system. Most joint diseases cause damage to articular cartilage, the soft tissue that acts as a bearing surface within the load-bearing joints. The function of articular cartilage is to provide a wear-resistant joint surface with a very low coefficient of friction and to reduce the compressive stresses experienced at the end of the long bones. Osteoarthritis can be described as the progressive degeneration of articular cartilage. This disorder causes large areas of cartilage in the load-bearing regions of the joint to become split and fragmented, resulting finally in the exposure of underlying bone. Osteoarthritis has been associated with a number of conditions including the deposition of crystals within the tissue. It has been postulated that crystal deposits have the potential to cause mechanical damage to articular cartilage. Two possible damage mechanisms have been identified; localised tissue damage in the vicinity of the crystal aggregate and surface damage induced by the presence of an aggregate. Articular cartilage is a biphasic material as it consists of a fluid phase, composed mainly of water, and a porous-permeable solid phase. The biphasic nature of the tissue was modelled using the ABAQUS/Standard Finite Element software. Failure criteria for the tissue were investigated using this technique and radial stress and radial strain were found to be reliable predictors of damage. Damage threshold values were determined for radial tensile stress (72 kPa) and radial tensile strain (0.144). A finite element model was then developed to investigate the propensity for crystal deposits to cause damage to a cartilage layer under cyclic loading conditions. It was predicted that aggregates embedded deep within the cartilage layer do not have the potential to cause either local or surface damage. Aggregates nearer the articular surface have the potential to cause localised tissue damage, and it was found that this was dependent upon their stiffness.