This thesis has investigated the possibility of optimizing curing time by changing the energy source from a conventional oven to infrared radiation (IR) and if it is possible to achieve similar results as the company's current production of glass fiber composite tubes.   Many different parameters (time, temperature, heating rate, and rotation speed) might influence a cured composite tube's properties. Reduced factorial experiments were conducted to test all these parameters cost-efficient where each parameter was tested at a high and low level. However, every possible combination was not investigated.   Temperature measurements during the curing cycles, energy calculations, three-point bending, and differential scanning calorimetry analysis were conducted to compare the two different curing methods, hot air and IR curing. The current production flexural strength and glass transition temperature (Tg) have acted as benchmark values that the tubes cured with IR would have to reach to be considered a reliable manufacturing method. Differential scanning calorimetry (DSC) analyses were conducted to measure the Tg and three-point bending to determine the flexural strength. Due to that no standard exist for three-point bending of composite tubes, an in-house method was created and verified with a finite element simulation in Abaqus, to measure the flexural strength. The simulated reaction force was circa 76.9% of the measured force at the same displacement during the three-point bending test of the tubes. The simulation found that the stress concentration did occur at the same locations as the fracture occurred in the three-point bending test.     The temperature difference between the top of the laminate and the core was close to zero degrees for the current production by hot air in a thermal oven. A more significant temperature difference between the core and top of the laminate was found during curing with IR. However, a higher rotation speed was found to create a more evenly temperature distribution in the composite.    No clear correlation between the Tg and the flexural strength was found, as the literature suggests while comparing each test cured with IR. Nevertheless, by comparing every test cured with IR with the current production of the tube, it was determined that a lower Tg could cause a lower flexural strength. However, the lower flexural strength for the tubes cured by IR could also be explained by the temperature difference found between the core temperature and the top of the laminate during the curing process.       The reduced factorial experiments showed that it was possible to reach similar properties by curing with IR and reducing the curing time by 69.3%. Time and the combination of time and temperature were found to affect the result when it comes to the glass transition temperature. Regarding flexural strength, no parameters were found to impact the outcome. By investigating the time and temperature further, the curing time could be reduced to 71.3% compared with the current production and still achieve similar properties. Nevertheless, the energy use for curing with IR was found to require 8.3 times more than the current production.

The assignment handed out by Cementa in Skövde is to investigate why crack formation and propagation emerge in the fixed attachment clamps and propose solutions against it. The fixed attachments are part of the cooling element suspension, used in the cement production to cool the material coming out of the oven. There is also an attachment clamp for the cooling elements with a clearance around the cooling elements which allows some movement in all directions. Since Cementa has not performed any former research for this case, a thorough literature study is conducted. Material properties, manufacturing, fracture types and fracture mechanisms are subjects examined in the literature study. Hypotheses are formed using the gathered information and are tested by calculations and analyses. The two main hypotheses formed are: Stresses greater than the tensile strength for the steel causes crack formation. Fatigue causes crack formation. The methods used to investigate the hypotheses are calculations by hand and FE-analysis. The results from calculations and analyses shows that the clearance in the movable attachment had great influence on the stresses obtained in the fixed attachment and is the probable cause for crack formation and propagation. The most likely fracture mechanism is fatigue and corrosion, bad welds and thermal tension could be contributing factors for crack formation.

No description available.

A prediction model [3] of macrosegregation in continuously cast steel slabs developed by Barber et al from Corus Teesside Technology Centre, UK as an extension of the work of Miyazawa and Schwerdtfeger [4] is presented in this thesis. Improvements have been made in the model to include the effect of many bulges between the supporting rolls induced by the ferrostatic pressure exerted on the solidifying shell by the liquid phase, which were approximated following a deflection of an elastic beam model. The system involved three alloying elements that are 0.1 wt% C, 1.05 wt% Mn, and 0.25 wt% Si as initial concentrations. The iterative numerical methods used to solve for velocity and concentration were the Gauss-Seidel method and Upwind Differencing, respectively.Through a mesh sensitivity analysis, a horizontal growth rate of 1.25 was decided while the grid is equally spaced in the vertical direction over a two-dimensional mid-width plane of the CC22 slab caster configuration at Tata Steel Netherlands in Ijmuiden. Good results were obtained from a validation run despite the assumptions considered. The predicted macrosegregation patterns for C and Mn were to a great extent compatible with the measured ones. The maximum concentrations were predicted at the strand centerline that are 0.13 wt% C, 1.10 wt% Mn, and 0.26 wt% Si. With respect to measured values, it was slightly higher for C by 2.23% error but lower for Mn at 2.28%error, which could be seen negligible. The main factors concluded to influence the strand centerline macrosegregation were initial melt temperature, casting speed, cooling rate and supporting-rolls location when neglecting the mutual interactions between elements. Further improvements can include modifications of the assumptions followed in this model.

No description available.

Power Transformers are an important and complex part of the electrical transmission technology. One of the main producers of these transformers worldwide is Hitachi Energy, for which this work has been done.This work proposes to create a simulation model for the transport of moisture in transformer insulation material using Finite Element Method implemented in COMSOL 6.1. The transport of moisture in cellulose material is a complex process but the model assumes that diffusion is the dominant transport mechanism. For that, a model based on Fick’s second law is used. The value of the coefficient is defined experimentally at different temperatures. But some of the tools used for their measurements are inaccurate, for example at higher temperatures or because they only give an average moisture content at a given time. Then a difficulty is to assert the simulation’s validity by comparison with the experimental data. In the present work, care is given to validate the model by comparison with precedent works.Using experimental data coming from internal sources at the company (Hitachi Energy), curves are then drawn to see the process of ingress and egress of moisture in pressboard material under different boundary conditions to simulate several steps of the production process. Possible future research directions include the use of data from future experiments and the creation of a more complex model to simulate a more realistic geometry.

The large environmental impact related to the use of fossil fuel has driven the shift toward renewable sourced alternatives. Fossil diesel can be nowadays replaced by biodiesel, obtained from vegetable oils and fats, mostly used as biodiesel blends. However, some drawbacks are related to the use of this bio-fuel, among which the formation of deposit in injectors and filters causing a reduction of engine performances or engine failure. This thesis project focuses on the analysis of the mechanism of formation of soft particles in biodiesel deposits. These particles are constituted mostly of carboxylic metal soaps, and were found in biodiesel engines after using aged biofuel with contaminants, such as engine oil. The role of short chain fatty acids (SCFAs) has been investigated, together with the use of three different calcium sources, to analyse the formation mechanism of calcium soaps. Artificial ageing of B10 and B100 test fuels was performed, and in some cases an inert gas was bubbled to remove the formed SCFAs. Calcium sources, namely calcium oxide, calcium carbonate and engine oil, were added to investigatethe formation of soft particles. Ion chromatography, pH measurements, NMR spectroscopy and oxidation stability tests have been performed on the liquid test fuel to verify the presence and effect of SCFAs, while FTIR spectroscopy and GC/MS analyses were used to verify the presence of calcium soaps in the deposit and in solution. In contrast to the expectation, it was found that the presence of SCFAs in the fuel not is fundamental for the formation of carboxylic soap. Moreover, the different calcium sources result in different amounts and textures of metal soaps in deposits and in solution. / Den stora miljöpåverkan relaterad till användningen av fossilt bränsle har drivit övergången till förnybara alternativ. Fossil diesel kan numera ersättas av biodiesel, härledd av vegetabiliska oljor och fetter, oftast används som biodieselblandningar. Vissa nackdelar är emellertid relaterade till användningen av detta biobränsle, bland annat bildandet av avlagring i injektorer och filter som orsakar en minskning av motorprestanda eller motorfel. Detta projekt fokuserar på analysen av mekanismen för bildning av mjuka partiklar i biodieselavlagring. Dessa partiklar består huvudsakligen av karboxylmetall tvålar och hittades i biodieselmotorer efter användning av åldrad biobränsle med föroreningar, såsom motorolja. Rollen för kortkedjiga fettsyror (SCFA) har undersökts, tillsammans med användning av tre olika kalciumkomponenter, för att analysera bildningsmekanismen för kalciumtvålar. Experimentellt åldring av testbränslen B10 och B100 på labbet utfördes, och i vissa fall bubblades en inert gas för att avlägsna de bildade SCFA. Kalcium komponenter, nämligen kalciumoxid, kalciumkarbonat och motorolja, tillsattes för att undersöka bildningen av mjuka partiklar. Jonkromatografi, pH-mätningar, NMR- spektroskopi och oxidations stabilitetstester har utförts på det flytande testbränslet för att verifiera närvaron och effekten av SCFA, medan FTIR-spektroskopi och GC/MS-analyser användes för att verifiera närvaron av kalciumtvålar i sedimentet och i lösning. I motsats till förväntningarna visades det att närvaron av SCFA i bränslet inte är grundläggande för bildandet av karboxyltvål. Dessutom resulterar de olika kalciumkomponenterna i olika mängder och strukturer av metalltvålar i sediment och i lösning.

Lignin has the potential to be used as green material to inhibit the corrosion of metallic substrates. Mussel adhesive protein is used to modify lignin due to its great adhesive and film forming abilities. Electrochemical impedance spectroscopy (EIS) has been applied to in-situ measure the corrosion resistance of the formed surface composite films in the corrosive environment. The equivalent circuit is used to fit the EIS data to obtain the quantitative results of the surface films. The results show that MAP modified lignin composite film can provide enhanced corrosion protection to the carbon steel substrate and presents self-healing property. / Lignin har potential att användas som grönt material för att hämma korrosion av metalliska underlag. Mussellhäftande protein används för att modifiera lignin på grund av dess stora lim- och filmbildningsförmåga. Elektrokemisk impedansspektroskopi (EIS) har applicerats för att mäta korrosionsbeständigheten hos de bildade ytkompositfilmerna i den korrosiva miljön. Ekvivalentkretsen används för att passa EIS-data för att erhålla kvantitativa resultat från ytfilmerna. Resultaten visar att MAP-modifierad ligninkompositfilm kan ge förbättrat korrosionsskydd för kolfastsubstratet och uppvisar självhelande egenskaper.

Techniques to improve the speed at which materials are researched and developed has been conducted by investigating the machine learning methodology. These techniques offer solutions to connect the length scales of material prop- erties from atomistic and chemical features using materials databases generated from collected data. In this assessment, two material informatics methodologies are used to predict material properties in steels and nickel based superalloys using this approach. Martensite start temperature and sigma phase amount as a function of input composition has been modelled with the use of machine learning algorithms. The experimental methodology had a collection of over 2000 unique experimental martensite start temperature points. This yielded important information on higher order interactions for the martensite start temperature, and a root mean square error (rmse) of 29 Kelvin using ensemble tree based algorithms. The metamodel was designed using an artificial neural network from TensorFlow’s library to predict sigma phase fraction and its composition. The methodology for building, calculating, and using data from TC-Python will be laid out. This generates a model that would generalize sigma phase fraction 97.9 % of Thermo-Calc’s equilibrium model in 7.1 seconds compared to 227 hours neded in the simulation to calculate the same amount of material property data. / Tekniker för att förbättra hastigheten med material som forskas och utvecklas har genomförts genom att undersöka metodik för maskininlärning. Dessa tekniker erbjuder lösningar för att ansluta längdskalorna för materialegenskaper från atomistiska och kemiska egenskaper med hjälp av materialdatabaser genererade från insamlade data. I denna bedömning används två materialinformatikmetoder för att förutsäga materialegenskaper i stål och nickelbaserade superlegeringar med denna metod. Martensite-starttemperatur och sigmafasmängd som en funktion av ingångssammansättningen har modellerats med användning av maskininlärningsalgoritmer. Den experimentella metoden hade en samling av över 2000 unika experimentella starttemperaturpunkter för martensit. Detta gav viktig information om interaktioner med högre ordning för martensit-starttemperaturen och ett root-medelvärde-kvadratfel (rmse) på 29 Kelvin med användning av ensemble-trädbaserade algoritmer. Metamodellen designades med hjälp av ett artificiellt neuralt nätverk från TensorFlows bibliotek för att förutsäga sigma-fasfraktion och dess sammansättning. Metoden för att bygga, beräkna och använda data från TC-Python kommer att anges. Detta genererar en modell som skulle generalisera sigma-fasfraktion 97,9 % av Thermo-Calcs jämviktsmodell på 7,1 sekunder jämfört med 227 timmar som behövs i simuleringen för att beräkna samma mängd materialegenskapsdata.

<p>Confidential</p>