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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Surface Roughness Considerations in Design for Additive Manufacturing: A Space Industry Case Study

Obilanade, Didunoluwa January 2023 (has links)
Additive Manufacturing (AM), commonly known as 3D printing, represents manufacturing technology that creates objects layer by layer based on 3D model data. AM technologies have capabilities that provide engineers with new design opportunities outside the constraints of traditional subtractive manufacturing. These capabilities of AM have made it attractive for manufacturing components in the space industry., where parts are often bespoke and complex. In particular, Laser Powder Bed Fusion (LPBF) has attracted attention due to its ability to produce components with the part properties required for space applications. Additionally, the precision of the laser enables the production of innovative near-net shape and low-weight part designs.  However, due to the powdered metal material, the LPBF process is categorised with rough surfaces in the as-built state. The extent and effect of surface roughness are closely linked to geometrical design variables, including build orientation, overhangs, support structure, and build parameters; hence the more intricate the design, the more difficult the removal of this roughness. Consequently, the as-built surface for most applications is too rough and could adversely affect proprieties, i.e., fatigue. Hence, practical Design for AM (DfAM) supports should be developed that understand how design factors, such as surface roughness, will impact a part’s performance. This thesis therefore presents literature reviews on research related to LPBF surface roughness and design support, exploring the trends in managing surface roughness and investigations on the characteristics of design support. Additionally, through a space industry case study, a proposed process involving additive manufacturing design artefacts (AMDAs) is considered to investigate and describe the relationship between design, surface roughness, and performance. The review found that, in general, research focuses on the relationship between surface roughness and LPBF build parameters, material properties, or post-processing. There is very little support for design engineers to consider how surface roughness from an AM process affects the final product (less than 1% of the review articles). In investigating surface roughness, the AMDA process identified characteristics that impact roughness levels and geometric adherence to part design. Additionally, twelve characteristics of design support were identified and considered to review the AMDA process. The process aided the evaluation of design uncertainties and provided indications of part performance. However, iterations of the process can be required to clarify product-specific design uncertainties. Though, the designer obtains a better understanding of their design and the AM process with each iteration. The inclusion of the requirement to set evaluation criteria for artefacts was recommended to develop the AMDA process as design support.
22

Exploring Megaproject Governance with Regard to Collaboration : The case of the International Space Station / Utforska megaprojektstyrning med hänsyn till samarbete : Fallet med den internationella rymdstationen

Gabor, Tatar January 2021 (has links)
Our society is more dependent on global problem-solving than ever before. Megaprojects are one way of solving this challenge. Even though some of them are supposed to give answers to the direst problems of our time, our knowledge about them is paradoxically poor that leads to economic losses. The areas that especially demand attention are the project architecture, relationships, and innovative governance solutions that promote collaboration. The purpose of the thesis is to explore how megaprojects are governed in regard to collaboration through the case of a science-focused intergovernmental megaproject. The report builds an understanding of megaprojects, governance, and collaboration. Then it attempts to identify how governance affects collaboration over the paradox of control and flexibility within the case of the International Space Station (ISS) as one of the most recognized examples of megaprojects. It has been found that contractual and relational governance should be both present within megaproject governance. Because historically contractual arrangements are dominating governance, additional focus is required on the relational counterpart. The five main parts of the ISS governance, legal framework, organizational structure, goals, roles, and funding system, are mainly related to contractual governance, facilitating control. However, they also feature mechanisms that promote flexibility, thus providing a platform for collaborative practices to be formed. The top tier of the legal framework provides stability but the lower tiers offer opportunities to implement changes in the program. The goals of the ISS serve as a strong motivator that puts the common goals in front of the individual agendas of the partner countries. Furthermore, concerning funding, the in-kind contributions system provides a different set of incentives through bartering, compared to the traditionally used financing, and supports the collaborative environment by building closer relationships with industry partners. The example of the ISS revealed valuable lessons to better understand intergovernmental megaprojects and solve the challenges of the future affecting us. / Vårt samhälle är mer beroende av problemlösning på en globalnivå där specifikt Megaprojekt är en form för att lösa denna utmaning. Även om vissa av dem ska ge svar på de allvarligaste problemen i vår tid, är vår kunskap om dem paradoxalt dålig vilket leder till ekonomiska förluster. De områden som särskilt kräver uppmärksamhet är projektarkitekturen, relationer och innovativa styrningslösningar som främjar samarbete. Syftet med denna masteruppsats är att undersöka hur megaprojekt styrs gällande samarbetet mellan vetenskapligt fokuserat mellanstatliga projekt. Uppsatsen skapar en ökad förståelse av megaprojekt, styrning och samarbete. Därefter identifieras hur styrning påverkar samarbetet över motsägelserna mellan kontroll och flexibilitet inom den International Space Station (ISS). ISS är ett av de mest erkända exemplen på megaprojekt. Man har funnit att både avtals- och relationell styrning bör vara närvarande inom megaprojektstyrning. Eftersom historiskt avtalsmässiga arrangemang är dominansstyrning krävs mer fokus på den relationella motsvarigheten. Den fem huvuddelarna av ISS styrning, rättsligt ramverk, organisationsstruktur, mål, roller och finansieringssystem är huvudsakligen relaterade till avtalsstyrning vilket underlättar kontroll. Delarna visas även ha mekanismer som främjar flexibilitet vilket skapar en plattform för kommande samarbetsmetoder. Den högsta nivån i den rättsliga ramen ger stabilitet medan de lägre nivåerna främjar möjligheter att genomföra förändringar i programmet. Målen med ISS fungerar som en stark motivator som sätter de gemensamma målen framför partnerländernas individuella dagordningar. Gällande finansiering tillhandahåller systemet med naturbidrag genom byteshandel en annan uppsättning incitament jämfört med den traditionellt använda finansieringen och stöder vidare samarbetsmiljön genom att bygga närmare relationer med industripartners. Exemplet på ISS avslöjade värdefulla lärdomar för att bättre förstå mellanstatliga megaprojekt och lösa framtidens utmaningar som påverkar oss.
23

Využití uhlíkových kompozitů k pasivnímu chlazení v oblasti kosmického průmyslu / Passive heat dissipation using carbon-based material

Genco, Ondřej January 2020 (has links)
The content of the diploma thesis is evaluation of the usability of carbon composites in the space industry. The aim of this work is to assess whether carbon composites can find application in mechanical systems of passive thermal protection of artificial objects. Model examples demonstrate the principle of operation of selected passive thermal protection. The evaluation is realized based on the results of thermal analysis. Analytical formulas from field theory of heat transfer are used as a calculation method. The diploma thesis consists from two parts. The theoretical part briefly describes the mechanisms of heat transfer, selected types of passive thermal protection and properties and applications of carbon composites. The practical part consists of the assignment, calculation and evaluation of three examples. The results show that carbon composites can compete with commonly used materials for specific requirements.
24

Key components of building customer trust in the space industry : An investigation of the future of satellite applications

Nittler, Josefine, Ahlsén, Mattias January 2021 (has links)
This study is an empirical case study of the Swedish space- and automation company Unibap AB about how to build trust in the space industry. The space industry is distinctive in the way that space missions are at high stakes because of the high costs and the fact that the technology can not be modified after launch. Reliability and trust are therefore crucial factors of doing business in the space industry. Also, AI-based satellite solutions can bring huge benefits but 60% of the resistance from companies to running AI is linked to lack of trust. The concept of trust has been discussed before in the industrial marketing literature and differentiates between social sources and offer-related sources of trust. However, there appears to be an empirical as well as a theoretical gap when it comes to building trust in the space industry. Because the topic is unexplored, an exploratory methodology is used when interviewing 12 actors in the space- and high-tech industry worldwide. Since one important aspect of offer-related trust seems to be usability, this study also includes a usability evaluation of Unibap's space computer solution SpaceCloud which enables on-board AI applications. Key antecedents of trust in the space industry were found to be transparency, competence, reliability of technology, and exact delivery times. It appears that social- and offer-related trust significantly influence partnerships between companies and that offer-related trust is the most important type of trust to win contracts of tax-funded agencies. Strengths and improvements of the usability of SpaceCloud are also identified, and it is concluded that SpaceCloud has the potential to offer a new way of building satellite applications in the future.

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