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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.
301

Simulation of the Filling of Epoxy in Resin Impregnated Paper Bushings : Analysis of Temperature Measurements during Filling of Epoxy and the Generation of New Filling Recipes to Avoid Cavities in the RIP Bushing

Damsgaard Falck, Hanna January 2023 (has links)
The goal of the project was to create a model in COMSOL Multiphysics that can simulate thefilling of resin (epoxy) in Resin Impregnated Paper (RIP) bushings. Using the model new fillingrecipes that avoid problematic double-fronts and thereby avoid the creation of cavities in thebushings should be designed. Another goal was to use Thermocouples and Fiber optics tomeasure the temperature at different positions during the filling to get a better understanding ofthe filling. The first step was to design and determine functions, parameters (such as thepermeability), boundary conditions etc. for the simulation model in COMSOL Multiphysics and tocalibrate the model to align with measurements of fillings previously done. The second part wasto increase the filling time to minimize the maximum difference between filling fronts in thebushings and thereby decrease the risk of problematical double-fronts that create cavities,which decrease the bushing's dielectrical properties. The simulation model aligned somewhatwith the measured data but there is a lot of uncertainty both in the measurements and due toassumptions made in the simulation model. The measurements from Thermocouples and Fiberoptics where almost identical and they indicated that the filling of the bushing is symmetric.
302

Self-assembly of Fatty Acids of Hair at the water-air interface

Batista, Marine January 2020 (has links)
18-methyl eicosanoic acid (18-MEA), which is a branched fatty acid, is found at the outermost surface of mammalian hair with other straight-chain fatty acids such as palmitic acid and stearic acid. However, the precise role of 18-MEA is not yet completely understood. 18-MEA on Cadmium chloride subphase forms curvature at the water/air interface, leading to the formation of 3D-domains that can be easily transferred into solid support allowing to create complex and multi-functional structures. This project investigates if a non-toxic subphase would also lead to the formation of 3D-domains or if it is an intrinsic property of Cadmium chloride; and to investigate if the domain properties were tuneable. A combination of the Langmuir trough and the Atomic Force Microscopy is used. It is shown that a toxic subphase is not necessary and a more benign sodium subphase can be used to obtain 3D-domains. It is also shown that different chains length interact dissimilarly with the branched fatty acid. This results in the formation of very various structures. It is also shown that the subphase, the surface pressure of deposition and the composition of the fatty acid in the monolayer affect the properties of the domain, leading to different size of domain but also different morphology in the domain. Circular domains, elongated domains, continuous labyrinthine structures, dendritic centipede-like structures and no domains are obtained. / På den yttersta ytan av däggdjurshår återfinns den grenade fettsyran 18-methyleikosansyra tillsammans en mindre mängd av de raka fettsyrornapalmitinsyra och stearinsyra. Den exakta rollen av 18-MEA är dock ännu inte heltklarlagd. Ett monoskikt av 18-MEA på en subfas innehållande kadmiumklorid påtvingar en krökning av vatten–luftgränsytan. Det leder till bildandet av 3D-domäner som lätt kan överföras från vattenytan till fasta ytor vilket möjliggör att dekorera dessa ytor med komplexa och multifunktionella strukturer. Detta projekt undersöker om andra, miljövänliga motjoner i subfasen också skulle leda till bildandet av 3D-domäner eller om det är en inneboende egenskap hos kadmiumklorid. Det här ger även insikt om hur motjoner kan användas för att påverka och kontrollera domänbildningen. En kombination av Langmuirtråg och atomkraftsmikroskopi används för att karakterisera monoskikten. Det visas att en subfas innehållande kadmium inte är nödvändig och att en mer miljövänlig natriumsubfas kan användas för att bilda 3D-domäner. Det visas också att olika kedjors längd interagerar olika med den grenade fettsyran 18-MEA, vilket resulterar i bildandet av olika strukturer i deponerade monoskikt. Det visas också att yttrycket vid deponering och sammansättningen av fettsyror i mono skiktet påverkar egenskaperna hos monoskiktet, vilket leder till varierande storlek och struktur på de bildade domänerna, där cirkulära och långsträckta domäner, kontinuerliga labyrintstrukturer och dendritiska tusenfotingsliknande strukturer observeras.
303

Tribological behaviour of CVD diamondcoated tools during machining of highstrength aluminum alloy : Master thesis project on tribological behavior of super hard materials: chemicalvapor deposition diamond (CVD) coated cutting tools and polycrystalline diamond(PCD) cutting tools used in machining of high strength aluminium alloy

Lundquist, Oskar January 2022 (has links)
Machining of Aluminum can be complicated due to large amounts of adhesion and diffusion of the aluminum onto the cutting tool, causing effects such as built-up layers and built-up edges. This leads to poor surface finishes and can significantly affect the tool life. CVD diamond coated tools have shown to be a potential solution to this problem and is tested and analyzed as such in this thesis. CVD diamond coated inserts are tested and compared to uncoated cemented carbide inserts and Polycrystalline diamond tipped inserts, in milling, turning and in refined tribological methods. The workpiece material in both the machine tests and the tribological tests is a high strength aluminum of the name Alumec 89. The machine tests were performed for 5 and 60 seconds at three cutting speeds, 600, 900 and 1200 m/min, keeping other parameters constant. The cutting inserts, the chips and the generated workpiece surface are examined using LOM, SEM and EDS. In the refined tribological testing, a pin-turning tribometer is used, with pins of uncoated and coated (CVD diamond) cemented carbide pins. These are tested at 5 and 30 seconds at 600 and 1200 m/min, applying a constant force of 10 N. In addition, a friction test was performed to measure the friction of the uncoated and the CVD diamond coated cemented carbide. Like the cutting inserts, the used pins were examined in LOM and SEM. The results show that while a large amount of built-up layer and built-up edges gather when using uncoated cemented carbide tools, only minimal amounts can be detected on CVD diamond and PCD. It has also been shown that the reason for the reduced adhesion in the case of diamond tooling materials is most likely due to the lack of chemical interactions between the diamond and the aluminum. The friction of the CVD diamond material was shown to be lower compared to the cemented carbide. The surface finish generated by the different materials, was the best in the case of PCD while the CVD generated multiple small scratches that severely reduced the surface roughness. This thesis provides some initial basic understanding of the interaction of CVD diamond coated inserts with high strength aluminum alloys.
304

Methodology for Obtaining S-N Curves using Fatigue Testing and Static FEA

Anderfelt, Filip, Äse, David January 2022 (has links)
The use of recommended S-N curves, presented in current literature, to analyse and determine the fatigue life of a part is common practice in, inter alia, the construction industry.However, the recommended S-N curves are generally created for larger components used in mainly the construction industry. Hence, the use of S-N curves for the evaluation of smaller parts, may result in over-dimensioning of such parts. For this reason, evaluation and designing of smaller parts could benefit from the development of an in house S-N curve specific for the part. The purpose of this thesis is to generate and validate an in-house method for creating a S-N curve, for a specific part to be compared with recommended S-N curves in the literature. The specific part used for the generating of the method is a welded steel joint with the geometry of two steel pipes, welded together in a t-formation and which has been provided by Thule AB for the purpose of the thesis. The method presented uses the results from 1) physical fatigue tests using a fatigue testing machine and 2) static FEA to derive a S-N curve for the specific part using the least squares method. A fatigue testing rig enables the gathering of data of the number of cycles to failure when the part is subject to a given cyclic load. The rig uses pneumatics to control the forces applied onto the part with the use of a cylinder. Furthermore, the fatigue testing rig was designed to be controlled by the applied force, meaning, that the rig ensured a homogeneous load cycle by measuring the force from a load cell and alternating the direction of the cylinder with an electrically controlled pressure valve. The performance of static FEA evaluations aim at locating stresses in the part. For this thesis the stresses were evaluated using the hot spot method due to the part's welded geometry. The data gathered from the physical fatigue tests and the static FEA evaluations are subsequently combined deriving S-N curves applicable to the part. From the fatigue tests and FEA evaluations for the t-shaped welded steel part, four S-N curves were derived of which two curves showed the results of a linear fitted curve whereas the other curves used the recommended slope of $-1/3$. The results showed that the S-N curves derived, using a set slope, resulted in similar curves to the recommended S-N curve provided by the literature. However, the linear fitted S-N curve showed that the part, according to the S-N curve, had a higher fatigue resistance than recommended.  Due to limitations in the thesis work, the S-N curves derived within the framework of this thesis should be regarded as theoretical and have been strictly used to identify whether the method generated is applicable for deriving of S-N curves.
305

Investigating the Impact of Additive Manufacturing on Business Models and Associated Barriers in Spare Parts Production : A Comparative Case Study

Rehmet, Jan David January 2023 (has links)
Additive manufacturing is described in literature as a disruptive technology for spare parts supply chains and shows the potential to impact business models for spare parts production through various advantages over conventional manufacturing. Understanding changes in business models is important for companies to adopt any technology and explore business opportunities around it. This research aims to fill the gap in literature on how business models change when additive manufacturing is used for spare parts production in the automotive industry. To investigate those changes a qualitative research design with semi-guided interviews with experts in automotive companies was chosen. The findings showed that the adoption of additive manufacturing in the automotive industry is generally slow and only a few spare parts are specifically developed for additive manufacturing. Especially for niche low-volume and high-value applications AM is already used. At the same time identifying new business cases is needed for broader adoption. Contrasting opinions in literature that additive manufacturing is a disruptive technology, the adopters referred to it rather as a tool. Moreover, the findings showed that the potential of additive manufacturing described in literature is still there but cannot be utilized yet due to various identified barriers at the current stage. The main identified barriers are lack of knowledge, suitable manufacturing data, and resources to explore additive manufacturing.
306

Iron Pieces from The Copper Wreck : An archaeometallurgical analysis of iron bars, billets and osmund iron found in Gdansk, Poland

Ghaysari, Mikael, Tiberghien, Benjamin, Åkerblom Jonsson, Maximilian January 2022 (has links)
The topic of osmund iron is of great interest in both historical and metallurgical perspective. Between the 14th and the 17th century osmund iron was exported extensively from Sweden but it has been difficult to characterize and confirm what exactly osmund iron is. Further research should be conducted to improve the understanding of this kind of iron.   This work is primarily focused on medieval osmund iron. It is trying to determine what can be stated about their production methods and how to identify osmund pieces. A literature review was performed, to present an overview of iron production methods in medieval Europe. A metallurgical analysis was conducted on a number of osmund samples from the polish shipwreck ‘Miedsiowiec’, W5., together with samples from bar irons and iron billets from the same ship. Analysis was performed using LOM and SEM with EDS, analysing the crystallographic structure of the samples, and performing slag analysis using EDS to establish statistical trends. One of the aims was to evaluate a previously suggested hypothesis, namely that osmunds were shipped to Danzig from Stockholm, and then refined into iron bars and billets.  The studied iron bars and billets were purely ferritic with some slag inclusions. By looking at the shape of the slag inclusions, it can be stated that the bars and billets were forged differently from the osmund pieces. The osmunds were found to be made by indirect reduction as seen by the prevalence of cementite. It could not be confirmed if the bars and billets were forged by osmunds.  The osmunds showed different trace element compositions, than the iron bars and billets. The microstructure of all the osmunds varies greatly, which was to be expected. The osmunds had a higher carbon content and fewer slag inclusions. The hypothesis that osmunds were refined into iron bars and billets is not supported by the findings of this study. / Osmundjärn är av stort arkeometallurgiskt intresse, som en svensk exportvara som exporterades mellan 1300- och 1600-talet. Det är dock svårt att definitivt avgöra vad osmundjärn är för något. Det krävs därför ytterligare analyser och studier inom detta område för att förbättra vår förståelse av osmundjärn.   Denna studie behandlar upphittade medeltida osmundjärn och stångjärn i syfte att avgöra hur dessa har tillverkats. En litteraturstudie genomfördes som omfattande medeltida järntillverkningsprocesser, den existerande forskningen om osmundjärn samt relevanta forskningsmetoder. Järnproverna som erhölls kommer från den polska skeppsvraket ’Miedsiowiec’, W5. Mikrostrukturen av proverna analyserades med ljusmikroskop och en SEM-EDS analys utfördes. En föregående publicering om osmundar har föreslagit att osmundar exporterades från Stockholm till Gdansk, där de välldes och bearbetades till stångjärn. Osmundarna och stångjärnen som erhölls undersöktes också för att korrektheten i denna hypotes. Stångjärnens mikrostrukturer var ferritiska med ett flertal inneslutningar. Två av de så kallade iron billets hade anisotropiskt formad slagg, jämfört med de så kallade iron bars som hade isotropiskt format slagg. Det bedömdes att osmundarna var tillverkade i en masugn, på grund av perliten som hittades i mikrostrukturen i samtliga osmundar. Mikrostrukturen i alla osmundar varierade dock kraftigt, som väntat. Osmundarna hade också högre kolhalt, och färre slaggpartiklar. Hypotesen om att osmundar bearbetades till stångjärn stöds därför inte av resultaten som hittats i denna studie.
307

Magnetic Ionic Liquids in Solutions and Emulsions

Bruno, Simon January 2022 (has links)
This research thesis reports experimental work done to design a stable magneticmicroemulsion of ionic liquid in 2-ethylhexyl laurate with the help of an ionic surfactant andan alcohol co-surfactant. The ionic liquids tested were based on a 1,3-dialkylimidazoliumcation with different alkyl chain lengths and a tetrachloroferrate anion ([FeCl4]+) to ensure theemulsion is sensitive to applied magnetic fields. Tests of solubility of these ionic liquids havebeen performed in different solvents and oils. Emulsification tests have been done withdifferent dispersing medium, surfactants as well as with different components quantities tofind the best composition possible. Polarity and chain length of alkyl radicals in ionic liquidsand hydrocarbons in alcohol co-surfactants were proved to affect the emulsification process.Shorter chains, and higher polarity of [C1C2im]+ [FeCl4]- (at 1wt%) combined with [C1C12im]+[FeCl4]- surfactant (between 3 and 5wt%) and non-polar 1-Hexanol co-surfactant (at 10 wt%)were the best combination to create a stable magnetic microemulsion in 2-ethylhexyl laurate. Applications for this microemulsion could vary from improved oil recovery to transport ofmaterials in liquid medium for examples and have all in common a better and tunablecontrollability of the used liquid via magnetic fields. / Denna forskningsuppsats rapporterar experimentellt arbete som gjorts för att designa enstabil magnetisk mikroemulsion av jonisk vätska i 2-EtylHexyllaurat med hjälp av ett jonisktytaktivt ämne och ett alkoholsamverkande ytaktivt ämne. De joniska vätskorna som testadesvar baserade på en 1,3-dialkylimidazoliumkatjon med olika alkylkedjelängder och entetraklorferratanjon ([FeCl4]+) för att säkerställa att emulsionen är känslig för applicerademagnetfält. Tester av lösligheten av dessa joniska vätskor har utförts i olika lösningsmedel ocholjor. Emulgeringstester har gjorts med olika dispergeringsmedium, ytaktiva ämnen samt medolika mängd komponenter för att hitta bästa möjliga sammansättning. Polaritet ochkedjelängd för alkylradikaler i joniska vätskor och kolväten i alkoholsamverkande ytaktivaämnen visade sig påverka emulgeringsprocessen. Kortare kedjor och högre polaritet för[C1C2im]+[FeCl4]- (vid 1 wt%) kombinerat med [C1C12im]+[FeCl4]- ytaktivt ämne (mellan 3 och 5 wt%) och opolär 1-hexanol medytaktivt medel (vid 10 wt% var den bästa kombinationen föratt skapa en stabil magnetisk mikroemulsion i 2-EtylHexyllaurat. Tillämpningar för denna mikroemulsion kan variera från förbättrad oljeutvinning tilltransport av material i flytande medium till exempel och har alla gemensamt en bättre ochavstämbar styrbarhet av den använda vätskan via magnetfält.
308

Techno-economic Analysis of Biomass Conversion to Hard Carbon Materials

Liu, Yuxin January 2022 (has links)
Hard carbon is an important material for future fossil-free transport systems, as it is a popular choice for the production of anodes for sodium-ion batteries. Biomass is a popular carbonaceous raw material for making hard carbon. It was only noticed at first because it is a renewable energy source, but with the wide application of carbon materials in several fields, industrial manufacturing using biomass as raw material has also been studied a lot. Process simulation of biomass pyrolysis and carbonization to produce hard carbon, pyrolysis gas, and bio-oil are investigated in this thesis work. The model simulation is assumed based on the current operating data and previous literature review, where the first two models use heat exchangers, and the last case uses by-products to generate heat. Economic analysis based on operating expenses and total capital investment is given based on simulated results. The results show that the yield of hard carbon is about 17% under 1000kg/h biomass feedstock, and the economic performance of using heat exchangers is better than that of pyrolysis gas combustion to supply energy. The economic results and break-even point are used to calculate the minimum selling price, payback period, and sensitivity analysis. The calculated minimum selling price for hard carbon is about SEK 20/kg, which is within the range of the current market price, and the payback period is about 16 years. From the sensitivity analysis results, if electricity prices continue to rise, the economics of using cracked gas may become more significant. / Hårt kol är ett viktigt material för framtida fossilfria transportsystem, eftersom det är ett populärt val för tillverkning av anoder till natriumjonbatterier. Biomassa är en populär kolhaltig råvara för att tillverka hårt kol. Det märktes först bara för att det är en förnybar energikälla, men med den breda användningen av kolmaterial inom flera områden har även industriell tillverkning med biomassa som råvara studerats mycket. Processimulering av biomassa pyrolys och karbonisering för att producera hårt kol, pyrolysgas och bioolja undersöks i detta examensarbete. Modellsimuleringen antas baserat på nuvarande driftdata och tidigare litteraturgenomgång, där de två första modellerna använder värmeväxlare och det sista fallet använder biprodukter för att generera värme. Ekonomisk analys baserad på driftskostnader och totala kapitalinvesteringar ges utifrån simulerade resultat. Resultaten visar att utbytet av hårt kol är cirka 17 % under 1000 kg/h biomassaråvara, och den ekonomiska prestandan för att använda värmeväxlare är bättre än för pyrolysgas förbränning för att leverera energi. De ekonomiska resultaten och brytpunkten används för att beräkna lägsta försäljningspris, återbetalningstid och känslighetsanalys. Det beräknade lägsta försäljningspriset för hårt kol är cirka 20 kr/kg, vilket ligger inom intervallet för gällande marknadspris, och återbetalningstiden är cirka 16 år. Om elpriserna fortsätter att stiga från resultaten av känslighetsanalysen kan ekonomin med att använda krackad gas bli mer betydande.
309

Developing a closed-loop supply chain to eliminate Single Use Plastic products : Implementing Circular Economy practices driven by EU commission directives

Ottosson, Elsa, Oweini, Rania January 2023 (has links)
Single use plastic products (SUPs) are a primary cause of plastic pollution causing significant environmental harm. These products have little to no value after use and are challenging to recycle cost efficiently. In a bid to combat this issue and foster circular economy, the European Union has declared a series of directives to gradually phase out SUPs as a strategy to eliminate these disposables from the market. This approach allows the market time to discover alternative solutions to replace SUPs, promoting the adoption of reusable products. To make a sustainable system of reusable products feasible and profitable, the key lies in devising a business model designed for a circular strategy of repeated use of goods. One effective approach involves establishing a closed-loop supply chain (CLSC) which entails the entire life cycle of a product, from sourcing raw materials, through manufacturing, utilisation, collection, reverse logistics and recycling. The purpose of this study was to develop a CLSC system for reusable plastic products between a plastic producing small or medium sized enterprise (SME) and an incumbent firm customer to attain a smooth transition from linear to circular economy. Employing an inductive approach, this case study considered the EU-directives as observational data, the change of business model as the result, and a general recommendation as the rule. The research method encompassed conducted interviews, mathematical prototyping, product design, and life cycle analysis, using various tools and methods in the process. Two case companies were involved: one large incumbent firm and one plastic producing SME. The aim was to design a circular business model (CBM) to capture the value of the collaboration between these two companies. After an analysation of the current situation, the main obstacles to a successful transition were identified. A comprehensive solution was developed, including a network of partners for the CLSC, a reusable product design, and the necessary implementation calculations. The finalised business model was anchored in the principles of the CLSC, the product design specifications and the calculations that determined the system’s viability. Implementation of the CBM would yield economic advantages for both stakeholders, as well as an improved green image factor and advancement in circular economy. Furthermore, this transition would cultivate valuable and lasting business relationships for both companies. These case findings harmonise with established theories which emphasise the significance of business models that are dependent on collaboration and long-term strategic planning. Lastly, they also underscore that value is created in product utilisation and not ownership.
310

Evaluation of the η (Eta) nitride with three laboratory melts

Lind, Martin, Johansson, Cecilia January 2015 (has links)
η (eta) nitride, Cr3Ni2SiN, is a precipitate found in high temperature austenitic stainless steel and is not yet included in Thermo-Calc steel database TCFE7. The aim of this thesis is to collect thermodynamic data to enable the addition of η nitride in the databases. Three laboratory melts with varying levels of silicon, chromium and nickel have been aged at 700-1000 °C for 75 h, 300 h and 1200 h and examined by Light Optical Microscopy, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, Wavelength Dispersive Spectroscopy, Electron Backscattered Diffraction and X-ray Powder Diffraction. η nitride is in the studied alloys an equilibrium phase stabilized with nitrogen. Presence of η nitride was confirmed by Energy Dispersive Spectroscopy and X-ray Powder Diffraction. It was found to precipitate in four different ways, at primary grain boundaries, intragranularly, as a "skeleton-like" precipitate and as a border around the occurring Cr2N precipitates. The area fraction of η nitrides increases with longer aging times and is favored by silicon and nickel. The composition of η nitride is not changing regardless of material composition, aging temperature and aging time. The composition of η nitride in all three materials are 8.7-9.7 wt.% silicon, 47-54 wt.% chromium, 1.4-4.1 wt.% iron and 33-36 wt.% nickel. The nitrogen content 2 determined by Wavelength Dispersive Spectroscopy is 2.8-3.2 wt.%. No complete equilibrium was achieved and together with incomplete mixing of the alloying elements during melting, the microstructure is difficult to evaluate. Other precipitates found are Cr2N, π nitride, σ phase and two unidentified phases, M and N. Of these phases at least Cr2N is not an equilibrium phase as it dissolves during aging. Further aging to achieve complete equilibrium is necessary.

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