Chalmers Open Digital Repository
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Extruded aluminum decks for pedestrian bridges Design optimization using genetic algorithm
Material efficiency in bridge structures is an important research topic to reduce the climate footprint and initial costs. One way of increasing material efficiency is to use appropriate materials where their properties benefit the structure. Aluminium offers a high stiffness-to-weight ratio, high durability, and is to a large degree re cyclable. These properties make aluminium an interesting material for bridge deck applications. The initial cost of the bridge deck has high priority amongst bridge authorities in Europe. To minimize the initial cost, one target is to minimize material con sumption. This thesis aims to develop an optimization procedure with the objective to minimize the material consumption of extruded aluminium profiles for pedestrian bridge deck applications. In the design of the deck, requirements stated in Eurocode are followed. The optimization is made using a genetic algorithm function from the global optimization toolbox in the software MATLAB. Cross-sectional geometries generated by the optimization procedure was evaluated separately by the imple mentation of a FE-module. The FE-module is controlled by parameterized Python scripting to create a FE-model and execute an analysis in the software ABAQUS CAE for each iteration. The optimization provided a cross-sectional geometry for the bridge deck. These results were used for a cost comparison between the optimized cross-section and more conventional alternatives in C-Mn and duplex steel. The comparison showed that the weight per square meter of the resulting optimized profile was significantly lower compared to the deck alternatives in steel. It also showed that saving from 8% up to 27% can be made on the initial investment cost if choosing aluminium instead of a conventional deck alternative in stainless steel. Thus, aluminium is shown to be a potential alternative to steel.
Effective Testing: Analysing and tackling challenges in production testing of industrial machines Master’s thesis in Production Engineering PHILIP LEES
This thesis aims to study the barriers affecting effective testing and setup of print and apply machinery, and how these barriers can be overcome. Based on theoretical foundation of quality, testing, production concepts (Product Lifecycle Management, Industry 4.0 etc.) and production engineering, and methodologies such as design research methodology, observation, time study, process mapping and ergonomics, results found indications of barriers within testing. These indications show that while test technicians are able to identify and rectify quality issues, more support to perform more effective testing is desired. Further analysis showed that specification definition, information flow, standardisation and documentation are specific areas where barriers for effective testing could be identified. A number of practical rec ommendations based on concepts such as Product Lifecycle Management, Industry 4.0 and checklist design are proposed. These are designed to leverage digitalisation and knowledge management in order to overcome the barriers discussed.
Investigating and developing a user-friendly interface for a DLP 3D bioprinter
The project investigates a light-based 3D bioprinter from a user point of view. It aims at finding how the current functionality and interface is perceived, what future functionalities are desired and how the interface could be improved. This should result in two deliverables. Firstly, a needs and desires list based on user insights and theoretical investigation. Secondly, a redesign of the current interface based on the needs and desires list that take aesthetic inspiration from the company’s existing software for extrusion-based printing. The bioprinter was investigated by observations, presentations, and theoretical evaluations. User insights were found through interviews with the primary user group, researchers within the medical field. Through these investigations and interviews, input was given on how the printer operates and what future functionality is wanted. With the product interface, three overarching goals were in focus for the redesign. The first goal was to improve the interface architecture, by having a consistent layout based on functional hierarchy. The second goal was to create a more touch friendly interface, and the last goal was to provide a design with high visual clarity. Apart from these interface improvements, new functionality was added to the redesign, for example expanding the interface compatibility to a 96 well plate and providing 3D model navigation. Design suggestions were created through iterations and evaluations with company experts throughout the design creation which helped the project create an interface that met the needs and desires. The final design combines concepts on different interactions needed to solve a setup process that suits current and future functionalities
From waste to wardrobe A comparative life cycle assessment on prolonging garment lifetime through repair and online second-hand
The clothing industry, encompassing all its activities from production to end-of-life, is a major contributor to environmental damage. The global production and consumption of clothes have roughly doubled in the past 15 years and fast fashion, with short garment lifecycles, intensifies the resource demand and the ensuing emissions. As a response, a shift from the traditional linear model of take-make-dispose to circularity can be seen through clothing companies working with circular business models (CBMs) or implementing circular strategies. Understanding the environmental impact of these circular initiatives is crucial for reducing the overall environmental footprint of clothing. The aim of the thesis was to assess the environmental impact of prolonging a pair of pant’s lifetime through two CBMs based on circular strategies or business models represented on the Swedish market and comparing it to the linear model. This was done by a mapping of Swedish clothing companies to select two either circular strategies or CBMS to serve as the foundation for the proposed models. Two general CBMs, one based on repair and one on an online second-hand (OSH) platform, were created, derived from information from interviews and literature. The environmental impact of the models was evaluated by conducting a life cycle assessment, and a sensitivity analysis was performed to assess the robustness of the results. The study found that companies are embracing circularity, either through CBMs or by implementing circular strategies such as physical and online second-hand, repair, exchange, and rental services. It was also shown that by extending a pair of pants’ lifetime through CBMs based on repair or OSH, the environmental impact per garment lifetime is reduced compared to the linear model. It was found that repair resulted in the lowest impact due to the significant increase in the number of enabled uses and the relatively small impact from the repairing process, despite a large impact from additional consumer car transports. OSH was also found to be preferable to the linear model. The additional processes required by OSH, i.e. truck transports and sorting and managing of the pants had a relatively low environmental impact and the CBM enabled more uses of the pants than the linear model achieved. However, OSH enabled fewer uses compared to repair, which made it fall between the linear model and repair in terms of overall impact. Lastly, it was also found that the potential of both repair and OSH is mainly dependent on consumers’ transportation modes and distances, and the actual number of achieved uses. The study shows the importance for consumers to fully utilize purchased garments and to consider repairing them instead of buying new ones when they are worn out. When consid- ering selling or donating their clothes, the study also shows the importance of only doing so if the garments are undamaged and of good quality to avoid additional transportation and waste creation that could ensue if the receiving company should deem the clothes unfit for resale. This, as general consumer behavior, would result in an overall reduction in the demand for the production of new clothing. Furthermore, the study shows that the con- sumers’ choice of transportation mode and ability to combine errands is of big importance to the overall efficiency and impact of the CBM.
Identification of critical pipes in a drinking water distribution system
The aim of this master thesis is to identify the most critical pipes in a drinking water distribution system through hydraulic modelling. The criticality of a pipe will be based on the consequences of pipe breakage including the affect on the supply of valuable users. Reliability will be seen as the ability to supply the quantitative demand to the households and valuable users at any time and to identify the criticality of a pipe, the pipe´s contribution to the system reliability has been evaluated. The contribution are estimated by evaluating the results from hydraulic simulation of the drinking water system, without the investigated pipe. Four indices, demand, affected users, time and valuable user index as well as a gathered criticality index are used to estimate the reliability of a drinking water system. To give more substance of the identification of critical pipes the reliability requirements of a drinking water distribution system could be further evolved. When determining the criticality of the pipes in the system, one key aspect is how pipes with different patterns should be compared between each other. Pressure driven and demand driven approach gave the same results for the majority of the pipes and a risk-based approach including probabilities would give a more in depth analysis of the criticality.