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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.
1

Light Stabilisation of Photochromic Prints

Brixland, Nikolina January 2016 (has links)
Light stabilisation of photochromic dyes is seen as the most challenging part in the development of photochromic dyes. The aim of this research is to compare stabilisation methods and their effect on the lifetime of a photochromic print on textile. The vision is to create a textile UV-sensor that detects current UV light exposure in the surroundings and alarms the wearer by showing colour. The developed inks have been formulated for ink-jet printing as a novel production method with resource saving properties. UV-LED light curable ink formulations were prepared for two dye classes; a non-commercial spirooxazine, a commercial spirooxazine (Oxford Blue) and a commercial naphthopyran (Ruby Red). Two different stabilisation methods were applied; chemically by incorporation of hindered amine light stabilisers and physically by polyurethane coating. Fatigue tests were performed to evaluate and compare the stabilisation methods. The tests included were household washing, multiple activations and intensive sun-lamp exposure. As a result it was found that Oxford Blue and spirooxazine had an initial better resistance to photodegradation than Ruby Red. The coating reduced the ability of colour development in higher extend for Oxford Blue and spirooxazine compared to Ruby Red. Moreover, the photocolouration increased with the number of activations for Oxford Blue and spirooxazine in particular. In general, the physically stabilised samples showed a better or similar fatigue resistance compared to chemically stabilised samples. On the other hand the results are weak in significance. It is concluded that the developed coating method in combination with further optimising has potential.
2

Modeling, Simulation and Optimization Approaches for Design of Lightweight Car Body Structures

Kiani, Morteza 17 August 2013 (has links)
Simulation-based design optimization and finite element method are used in this research to investigate weight reduction of car body structures made of metallic and composite materials under different design criteria. Besides crashworthiness in full frontal, offset frontal, and side impact scenarios, vibration frequencies, static stiffness, and joint rigidity are also considered. Energy absorption at the component level is used to study the effectiveness of carbon fiber reinforced polymer (CFRP) composite material with consideration of different failure criteria. A global-local design strategy is introduced and applied to multi-objective optimization of car body structures with CFRP components. Multiple example problems involving the analysis of full-vehicle crash and body-in-white models are used to examine the effect of material substitution and the choice of design criteria on weight reduction. The results of this study show that car body structures that are optimized for crashworthiness alone may not meet the vibration criterion. Moreover, optimized car body structures with CFRP components can be lighter with superior crashworthiness than the baseline and optimized metallic structures.
3

Modelling of a compensated foundation in GeoSuite Settlement / Modellering av en kompensationsgrundläggning i GeoSuite Sättning

Hermansson, Linnea, Söderberg, Rebecka January 2020 (has links)
The world today is constantly growing, creating a need of new roads and residential areas. New constructions lead to an increased load onto the soil, which can result in deformations when the soil layers underneath are compressed. To reduce the increased load on the soil, a compensated foundation can be used. This method is based on the principle that the load from the construction will be compensated by the excavated soil, often replaced by a lightweight material. As an example, this method can be used in areas with great clay layers and in sensitive projects where the rise of deformations can have undesirable consequences. It is of great importance to be able to understand the impact this method has on the soil and what long-term deformations that can be expected.GeoSuite Settlement is a tool for calculation of settlements and is frequently used in the Nordic industry of geotechnical engineering. In this study, the possibilities of modelling a compensated foundation in the software has been examined. Additionally, an analysis of parameters has been conducted in the aim of evaluating the importance of the parameters in the modelling process and the final results. Three different projects have been used as a basis, where one of them is a made-up case, based on the test site of Lilla Mellösa, and two actual cases designed by Structor Geoteknik Stockholm AB. Only one of these two projects have been completed, enabling post-construction measuring to be able to compare the calculated deformations with measured data, just about 16 months post-construction.Mainly three different approaches to the modelling of a compensated foundation has been studied in this work; unloading and loading, only loading corresponding to the total increase of load and with an edited soil profile adapted for a lightweight material (the description of the methods are to be found in Appendix 11.7). Similar patterns of deformations have been found in the results for the three methods, aside from one case where a slightly larger deformation occurred as a result of the lightweight material getting in contact with the underlying clay (instead of the filling/ dry crust). Based on this work, the simplest method is suggested to be used, i.e. only loading corresponding to the increased load.Due to the time limitations of this work, a decision to only study a few parameters in the analysis has been made and also to study them individually. Since the compressibility and creep characteristics of the clay is strongly dependent on the actual and former situation of the stress, the results of this parameter study are not directly applicable to any other case. However, this study clearly shows the importance of carefully evaluating the parameters of the clay, especially the preconsolidation pressure σ’c and the compressibility modulus M, which are important to obtain lifelike results. The importance of evaluating the time resistance value rS with respect to the current addition of stress has also been shown in this study. As expected, the groundwater level also plays an important role for the final settlements in the clay. / Vi lever i en värld som ständigt växer och detta skapar ett behov av nya vägar och bostadsområden. Nya konstruktioner som leder till en ökad belastning på jorden, kan ge upphov till sättningar när underliggande jordlager komprimeras. För att reducera belastningen på jorden kan en kompensationsgrundläggning användas, vilken bygger på principen att lasten från konstruktionen kompenseras av bortschaktad jord som ofta ersätts av ett lättfyllnadsmaterial. Metoden kan till exempel tillämpas i områden med mäktiga lerlager samt i känsliga projekt där uppkomsten av sättningar kan få stora konsekvenser. För att kunna dimensionera dessa är det av stor vikt att förstå dess påverkan på jorden och vilka långsiktiga sättningar som kan väntas uppkomma till följd av den nya konstruktionen.GeoSuite Sättning är ett beräkningsverktyg för sättningsberäkningar som idag används flitigt inom geoteknikbranschen. I detta arbete har möjligheterna att modellera en kompensationsgrundläggning med hjälp av programvaran studerats. Dessutom har en parameterstudie genomförts i syfte att undersöka vilka parametrar som är av stor betydelse för modelleringen och dess resultat. Som grund har tre projekt använts, varav ett är ett påhittat fall där jordprofilen baserats på den i testområdet Lilla Mellösa, och två är verkliga projekt tillhörande Structor Geoteknik Stockholm AB. I ett av dessa projekt har även beräknade deformationer jämförts mot uppmätta deformationer, cirka 16 månader efter konstruktion.Denna studie har främst studerat tre tillvägagångssätt för modellering av en kompensationsgrundläggning; av- och pålast, endast pålast motsvarande total lastökning samt av- och pålast med en redigerad jordprofil som anpassats till lättfyllnadsmaterialet (metoderna beskrivs i Bilaga 11.7). Resultaten har visat på ett snarlikt sättningsförlopp för de tre metoderna, bortsett från ett fall där en något större sättning uppkom till följd av att lättfyllningen i jordprofilen kom i kontakt med underliggande lera (istället för fyllning/ torrskorpelera). Utifrån detta arbete rekommenderas därmed att använda den enklaste metoden med endast pålast.På grund av arbetets tidsbegränsning har endast ett antal parametrar inkluderats i parameterstudien, dessutom har de främst utvärderats separat. Vilka parametrar för jordens kompressions- och krypegenskaper som har störst påverkan på resultatet är starkt beroende av spänningssituationen i det aktuella fallet och resultaten från detta arbete är därmed inte direkt applicerbart på andra projekt. Tydligt är dock att en noggrann utvärdering av jordens parametrar som dess förkonsolideringstryck σ’c samt kompressionsmodul M är väsentligt för att erhålla verklighetstrogna resultat. Studien har även visat på vikten av att utvärdera lerors kryptal rS med hänsyn till den aktuella tillskottsspänningen. Även grundvattennivån har visat sig ha en betydlig påverkan på uppkomsten av sättningar.
4

Entwicklung von Dünnglas-Kunststoff-Hybridplatten für das Bauwesen

Hänig, Julian 19 July 2023 (has links)
Moderne architektonische Fassadengestaltungen und Ganzglaskonstruktionen fordern immer häufiger entmaterialisiert wirkende Ansichten mit maximaler Transparenz für eine edle Erscheinung und einen hohen Grad an natürlicher Belichtung. Damit gehen große Spannweiten einher. Diese führen zu stark dimensionierten Glasaufbauten und bringen hohes Eigengewicht in die Konstruktion ein. Die Verfügbarkeit von Dünnglas in bautechnisch relevanten Abmessungen ermöglicht neue gewichtssparende Konstruktionsprinzipien und innovative Materialkombinationen. Dünnglas-Kunststoff-Hybridplatten bestehen aus einem leichten transparenten Kunststoffkern mit außenliegenden kratzbeständigen und dauerhaften Deckschichten aus Dünnglas. Sie bieten eine hohe Steifigkeit, Dauerhaftigkeit und volle Transparenz bei geringem Eigengewicht. Die Aushärtung der Ausgangskomponenten des Kunststoffkerns erfolgt direkt zwischen den Deckschichten und erzeugt dadurch einen vollflächigen Verbund zwischen Glas und Kunststoff ohne zusätzliche Zwischenschichten. Im Bauwesen sind Dünnglas-Kunststoff-Hybridplatten bislang unbekannt. Es liegen weder ausreichend Kenntnisse zu den Material- und Verbundeigenschaften vor noch sind die Eigenschaften als Bauprodukt entsprechend den hohen strukturellen und sicherheitstechnischen Anforderungen sowie den Ansprüchen an die Dauerhaftigkeit und an die optischen Eigenschaften nachgewiesen. Darüber hinaus fehlen konkrete Verbindungskonzepte zur Integration in das Bauwesen, um das Leichtbaupotenzial für entmaterialisiert wirkende transparente Konstruktionen auszunutzen. Im Rahmen dieser Arbeit werden erstmals Dünnglas-Kunststoff-Hybridplatten als innovatives Leichtbauprodukt systematisch untersucht und in das Bauwesen eingeordnet. Experimentelle und numerische Untersuchungen charakterisieren die Material- und Verbundeigenschaften mit zwei, am Markt verfügbaren, Kunststoffkernmaterialien – Polymethylmethacrylat (PMMA) und Polyurethan (PU), die jeweils für ein unterschiedliches Eigenschaftsspektrum stehen. Darüber hinaus wird zur Umsetzung maximaler Transparenz eine materialgerechte Verbindungstechnik entwickelt und deren mechanische Tragfähigkeiten charakterisiert. Zunächst werden in experimentellen Kleinteilprüfungen die thermophysikalischen und mechanischen Kennwerte der reinen Kunststoffkernmaterialien für die Beschreibung des Tragverhaltens im Verbund ermittelt. Anhand der Ergebnisse werden das PMMA als steifes, dauerhaftes, aber sprödes Material und das PU als vergleichsweise flexibles, zähes Material charakterisiert. Die experimentellen Untersuchungen zum Verbundverhalten fokussieren sich auf die Anforderungen für den Einsatz im Bauwesen. Eine numerische Strukturanalyse erweitert die Ergebnisse zum Tragverhalten und klärt offengebliebene Fragestellungen zum thermischen Ausdehnungsverhalten. Die Ergebnisse zeigen, dass mit Dünnglas-Kunststoff-Hybridplatten ein effizientes Tragverhalten und eine signifikante Gewichtsreduktion gegenüber herkömmlichem monolithischem Glas und Verbundglas erreicht wird. Anhand der spezifizierten Verbundeigenschaften werden resultierende Anwendungspotenziale entsprechend der Materialkombination abgeleitet. Die weiterführende Entwicklung einer tragfähig in den Kunststoffkern integrierten Verbindungstechnik bietet innovative Anbindungsmöglichkeiten für Dünnglas-Kunststoff-Hybridplatten im Strukturleichtbau. Die Funktionsweise wurde anhand eines Konstruktionsbeispiels auf der „glasstec 2022“ demonstriert. Die vorliegende Arbeit beinhaltet eine strukturierte Kennwertsammlung zur erstmaligen ingenieurmäßigen Beschreibung des Material- und Verbundverhaltens von Dünnglas-Kunststoff-Hybridplatten mit zwei unterschiedlichen Kunststoffkernmaterialien. Die Materialkombination aus Dünnglas und PMMA-Kunststoffkern erzielt die größte Materialeffizienz für eine effektive Gewichtsreduktion und erfüllt die grundlegenden Anforderungen aus dem Bauwesen. Anhand der weiterführend entwickelten konstruktiven Verbindungstechnik wird ein breiter Anwendungsbereich erschlossen. Mit den Ergebnissen dieser Arbeit werden somit die Grundlagen für die Einführung als Bauprodukt und für eine gewichtssparende Konstruktionsweise zur Umsetzung maximaler Transparenz geschaffen.:1 Einleitung 2 Grundlagen 3 Dünnglas-Kunststoff-Hybridplatten 4 Materialcharakterisierung Kunststoffkern 5 Verbundverhalten 6 Numerische Strukturanalyse 7 Einordnung in das Bauwesen 8 Konstruktive Verbindungstechnik 9 Konstruktionsbeispiel und Empfehlungen 10 Zusammenfassung und Ausblick 11 Literatur / Modern façade designs and all-glass construction are increasingly calling for dematerialisation and maximum transparency for a sophisticated appearance and a high degree of natural lighting. This is accompanied by large glass spans leading to increasing thickness of glass panels that introduce a high dead load into the supporting structure. The availability of thin glass in architecturally relevant dimensions permits new lightweight design principles and innovative material combinations. Innovative thin glass-plastic-composite panels consist of a lightweight and transparent polymeric interlayer core with scratch-resistant and durable cover layers of thin glass. They offer high stiffness, durability and full transparency at a low specific weight. The raw components of the polymer core are directly cured between the cover layers resulting in a chemical bond between glass and polymer over the entire surface without the need for additional interlayers. The thin glass-plastic-composite panels are currently unknown in the building industry. There is a lack of knowledge about the material and its composite behaviour. It has not been verified as a building product in accordance with the high structural and safety requirements as well as the requirements for durability and optical properties. In order to employ the lightweight design potential for dematerialised and transparent construction suitable for the building industry, there is a need for specific and material-appropriate connection techniques. In the context of this thesis, the novel thin glass-plastic-composite panels are systematically investigated in order to assess them as an innovative lightweight product. For the first time, they are classified in detail for application in the building industry. Material and composite properties using two different polymeric interlayer core materials – polymethyl methacrylate (PMMA) and polyurethane (PU) – are characterised by means of experimental and numerical investigations. Moreover, to achieve maximum transparency, a material-specific connection technique is developed and a wide range of mechanical load-bearing capacities are specified. First of all, the thermophysical and mechanical parameters of the pure polymer core materials are determined in experimental small part tests for the description of the composite load-bearing behaviour. The results identify the PMMA as a stiff, durable but brittle material and the PU as a fairly flexible, viscoelastic material. The investigations on the composite behaviour focus on the demands for use in the building industry and include experimental tests on the durability, the adhesion, the composite load-bearing behaviour as well as the response to hard and soft body impacts. A numerical analysis extends the results of experimental investigations on the structural load-bearing behaviour and examines the thermal expansion behaviour. The results indicate that the new material combination achieves a highly efficient structural load-bearing behaviour and a significant weight reduction compared to conventional monolithic and laminated glass. Application possibilities are derived based on the observed interlayer core material and composite characteristics. Further development of a connection technique as an integrated design into the polymeric interlayer core offers wide-ranging concepts of connecting thin glass-plastic-composite panels. Its functionality and practicability have been demonstrated in a construction prototype exhibited at “glasstec 2022” fair. The present work contains a well-structured material dataset to describe the material and composite behaviour of thin glass-plastic-composite panels comprehensively with two different polymeric interlayer core materials in engineering methodology. The material combination of thin glass and PMMA interlayer core achieves outstanding material efficiency with an effective weight reduction and fulfils the general requirements for application in building industry. A wide range of applications is facilitated thanks to the further development of a slim and integrated structural connection technique. The results of this work provide the framework for the introduction of a new lightweight building product with an innovative structural design to realise maximum transparency of façades and all-glass structures.:1 Einleitung 2 Grundlagen 3 Dünnglas-Kunststoff-Hybridplatten 4 Materialcharakterisierung Kunststoffkern 5 Verbundverhalten 6 Numerische Strukturanalyse 7 Einordnung in das Bauwesen 8 Konstruktive Verbindungstechnik 9 Konstruktionsbeispiel und Empfehlungen 10 Zusammenfassung und Ausblick 11 Literatur

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