Die sichere Einleitung und Übertragung der wirkenden Kräfte ist Bedingung für die Funktionsfähigkeit und die vollständige Ausnutzung der Tragfähigkeit von Textilbetonbauteilen und -verstärkungsschichten. So kann es bei ungünstiger Konfiguration und Anordnung der Einzelkomponenten des Verbundbaustoffes zur Ausbildung einer Vielzahl verschiedener Verbundversagensformen kommen. Diese umfassen neben der Bildung von verbundschädigenden Delaminations- und Spaltrissen lokale Abplatzungen der Betondeckung oder einen vorzeitigen Auszug der Garne aus dem Beton. Besonders beansprucht sind in diesem Zusammenhang die bei einer Anwendung von Textilbeton erforderlichen Endverankerungs- und Stoßbereiche der textilen Bewehrungen. Zur sicheren Ausbildung und Bemessung dieser wichtigen Detailpunkte liegen jedoch momentan noch keine umfassenden und zusammenhängenden Untersuchungen vor. Hauptziel der vorliegenden Dissertation war daher eine systematische Erforschung und Beschreibung des Tragverhaltens von Textilbeton in Endverankerungs- und Übergreifungsbereichen. Eine funktionierende und schädigungsfreie Verbundkraftübertragung bildet die Grundlage für die sichere Lasteinleitung und -übertragung. Daher wurden im ersten Teil der Arbeit ausführliche Untersuchungen zur Charakterisierung der zwischen Bewehrungstextil und Feinbetonmatrix wirkenden Kräfte und -mechanismen durchgeführt. Nach der Entwicklung eines geeigneten Versuchsaufbaus erfolgten umfangreiche Parametervariationen zur experimentellen Überprüfung des textilspezifischen Verbundverhaltens. Den Schwerpunkt der Untersuchungen bildete die Identifikation und Bewertung der aus verschiedenen Verarbeitungsparametern der textilen Bewehrungen resultierenden Verbundeinflüsse. Die Versuchsergebnisse ermöglichen die Bestimmung der zugehörigen Verbundspannungs-Schlupf-Beziehungen (VSB) mithilfe eines erarbeiteten Modellierungsverfahrens. Die so ermittelten Verbundkennwerte bilden die Grundlage für die weiteren rechnerischen Untersuchungen. Im zweiten Teil der Arbeit erfolgten Forschungen zum Tragverhalten von Endverankerungsbereichen. Hierbei stand der im Regelfall bemessungsrelevante Grenzzustand eines vorzeitigen Auszuges der Textilien aus der Betonmatrix im Mittelpunkt. Die Arbeiten umfassten experimentelle und theoretische Untersuchungen zur Beschreibung der Kraftübertragung. Aufbauend auf die ermittelten Verbundkennwerte wird ein unabhängiger analytischer Auswertealgorithmus zur Beschreibung des Verbundtragverhaltens in Endverankerungsbereichen dargestellt. Dieser ermöglicht eine detaillierte rechnerische Bestimmung der erforderlichen Endverankerungslängen von Textilbeton in Abhängigkeit konkreter bzw. untersuchter Bewehrungstextilien. Den dritten Forschungsschwerpunkt bildeten Untersuchungen zum Tragverhalten von Übergreifungsstößen in Textilbetonbauteilen. Mithilfe von umfassenden experimentellen und theoretischen Analysen an unterschiedlich konfigurierten und bewehrten Textilbetonen konnten die maßgebenden Versagensmechanismen untersucht und grundlegende Vorgaben für die Bemessung und Ausführung der Übergreifungsbereiche abgeleitet werden. Die gewonnenen Erkenntnisse wurden anhand von großformatigen Bauteilversuchen mit entsprechend konstruierten Übergreifungsstößen bestätigt. Zum Abschluss wird ein vereinfachtes Ingenieurmodell vorgestellt. Dieses erlaubt eine allgemeingültige und hinreichend genaue Bemessung der untersuchten Detailpunkte unter Beachtung der maßgebenden Grenzzustände. / The safe introduction and transmission of forces is a requirement for the workability as well as the possibility to make full use of the load bearing capacities of components and strengthening layers made of textile reinforced concrete. Accordingly, an unfavourable configuration and arrangement of the composite material’s individual components can lead to various modes of bond failure. These can result from the formation of bond damaging delamination cracks and longitudinal matrix splitting, local spalling of the concrete layer in the outer reinforcement layers or early yarn pull-out from the concrete. In this context, the areas of end anchorage and lap joints of the textile reinforcement, which cannot be avoided when using textile reinforced concrete, are particularly prone to failure. However, no comprehensive and coherent investigations regarding the safe configuration and dimensioning of these essential details are available yet. Consequently, systematic research into textile reinforced concrete’s load-bearing behaviour in the areas of end anchorage and lap joints and the subsequent description was the main goal of this dissertation. A working and damage-free transmission of bond force is the basis for a faultless load transmission and introduction. As a result, extensive tests concerning the characterization of the mechanisms and forces acting between reinforcing textile and fine grained concrete matrix were carried out as the first part of the investigations. After an appropriate test setup had been developed, a great variety of parameters was applied to experimentally examine the bond behaviour specific to the textile. The determination of the influencing factors resulting from various parameters in the textile reinforcement’s processing was a focus in the research. Based on a specifically developed modelling technique, the test results could be used to calculate the corresponding bond stress-slip-relation. The bond parameters, which were determined like this, served as the basis for the following calculations. The second part of the investigations was concerned with the load-bearing behaviour in end anchorage areas. In this case, the limit state of a yarn pull-out from the concrete matrix, which is usually essential for the dimensioning, was at the centre of attention. The investigations encompassed experimental and theoretical tests regarding the description of the force transmission. Based on the determined compound parameters, an independent analytic evaluation algorithm, which served to describe the load carrying behaviour of the bond in the end anchorage area, was presented. Through this algorithm, the detailed calculation of the required end anchorage lengths of textile reinforced concrete depending on the specific reinforcement textile was possible. The third research focus was on tests regarding the load-bearing behaviour of lap joints in textile reinforced concrete components. With the help of comprehensive experimental and theoretical analyses of variously configured and reinforced textile reinforced concretes, the decisive failure mechanisms were examined. Furthermore, fundamental demands for the dimensioning and execution of the lap joint areas could be derived. The findings were confirmed through tests on large-sized building components with corresponding lap joints. At the end of the investigations, a simplified engineering model is presented. This model makes a universally valid and exact dimensioning of the examined details possible while also paying attention to the decisive limit states.

Two vehicular optimal control problems are visited. The first relates to the minimum lap time problem, which is of interest in racing and the second the minimum fuel problem, which is of great importance in commercial road vehicles. Historically, minimum lap time problems were considered impractical due to their slow solution times compared with the quasi-steady static (QSS) simulations. However, with increasing computational power and advancement of numerical algorithms, such problems have become an invaluable tool for the racing teams. To keep the solution times reasonable, much attention still has to be paid to the problem formulation. The suspension of a Formula One car is modelled using classical mechanics and a meta-model is proposed to enable its incorporation in the optimal control problem. The interactions between the aerodynamics and the suspension are thereby studied and various related parameters are optimised. Aerodynamics plays a crucial role in the performance of Formula One cars. The influence of a locally applied perturbation to the aerodynamic balance is investigated to determine if a compromise made in design can actually lead to lap time improvements. Various issues related to minimum lap time calculations are then discussed. With the danger of climate change and the pressing need to reduce emissions, improvements in fuel consumption are presently needed more than ever. A methodology is developed for fuel performance optimisation of a hybrid vehicle equipped with an undersized engine, battery and a flywheel. Rather than using the widely used driving cycles, a three-dimensional route is chosen and the optimal driving and power management strategy is found with respect to a time of arrival constraint. The benefits of a multi-storage configuration are thereby demonstrated. Finally, the nonlinear stability of a vehicle model described by rational vector fields is investigated using region of attraction (RoA) analysis. With the aid of sum-of-squares programming techniques, Lyapunov functions are found whose level sets act as an under-approximation to the RoA. The influence of different vehicle parameters and driving conditions on the RoA is studied.

Traffic accidents are the second leading cause of child fatality among children younger than 15 years of age. In the course of 10 years, the implementation of child restraint systems has decreased child fatality in traffic accidents with 50%, for children younger than 15 years. To gain an understanding of the kinematics and injury mechanisms of children in cars, finite element based human body models, representing higher biofidelity compared to crash test dummies, are developed. An FP7 European project, PIPER, developed a child HBM with an associated framework for scaling, morphing and positioning. The PIPER child HBM is scalable between the ages of 1.5-6YO, with scalable anthropometrics. This makes the PIPER child HBM, a powerful tool for analyzing children in vehicles.  There are insufficient analyses conducted with the PIPER child HBM, due to its recent release. The purpose is thus to study the robustness of the HBM and its sensitivity to variation of lap belts by conducting a parametric study. Injury analysis and its sensitivity to lap belt variations were in addition studied in terms of kinematics by the study of submarining, the pelvic interaction with the lap belt, and the study of injuries related to the skull, brain, kidneys and liver. A full frontal crash simulation of a 6YO PIPER child HBM, with anthropometrics, covering the 50th percentile, have been investigated. The 6YO PIPER child HBM was seated with no booster, Volvo booster cushion and Volvo highback booster, with variations of the lap belt. The hip interactions and the submarining response of the 6YO PIPER child HBM were studied, by the study of the lap belt interactions with the pelvis and abdominal organs. The abdominal organs were related to the liver and kidneys, and compared to published threshold values.  This study showed that the overall robustness of the model was questionable. With respect to kinematics, the model indicated higher robustness, however, when conducted the crash simulations with the 6YO PIPER child HBM, it was concluded that the robustness was low due to repeated premature terminations. The 6YO PIPER child HBM revealed repeated errors such as, mesh distortions, negative volume and shooting nodes. When studying the sensitivity of the 6YO PIPER child HBM, when varying the lap belt angles, as well as changing the type of boosters in addition to vehicle anchorage positions, it could be seen that the 6YO PIPER child HBM was able to capture variations with respect to lap belt positioning. Hence, the model seems to be capable of providing relevant information regarding sensitivity for lap belt variations from the kinematic perspective, in terms of being able to capture kinematic o↵set, submarining and pelvis interaction with the lap belt. However, with respect to predicted abdominal injuries and head injuries, the sensitivity was not as distinct. Some limitations were observed in which the 6YO PIPER child HBM indicated unrealistic predicted injuries related to the head, which was associated with excessive movement of the 6YO PIPER child HBM. / Trafikolyckor är den näst vanligaste orsaken till barndödlighet i världen bland barn yngre än 15 år. Inom loppet av 10 år har användning av bilbarnstolar i fordon minskat barndödligheten med 50% hos barn under 15 år. För att få en ökad förståelse om barn i bilar framtogs finita element humanmodeller som har en detaljerad anatomi samt responser liknande till människan. Ett FP7 finansierat europeiskt projekt, PIPER, skapade en barnhumanmodell med en tillhörande programvara som används för skalning, förvandling, och positionering av barnhumanmodellen. Humanmodellen är skalbar för åldrarna 1.5 år upp till 6 år, med olika antropometriska värden. Detta gör att PIPER barnhumanmodellen är ett kraftfullt verktyg att använda sig av för att studera barn i bilar. Då PIPER barnhumanmodell lanserades nyligen, finns det i dagsläget bristfällig information om humanmodellen och programmet. Syftet var därmed att undersöka hur robust modellen var samt hur dess känslighet var mot variationer av höftbältet genom en parameterstudie. Skadors känslighet studerades dessutom mot variationer av höftbältet genom att studera kinematiken i form av underglidning och höftens interaktion med höftbältet. Dessutom studerades känsligheten på skador relaterade till skallen, levern och njurarna. I denna studie har en frontalkrock med en 6 årig PIPER barnhumanmodell med antropometriska värden, som innefattar 50:e percentilen, undersökts. Den 6åriga PIPER barnhumanmodellen var placerad utan bilbarnstol, på en Volvo bälteskudde och på en Volvo bältesstol, där höftbältet sedan varierades. Höftens interaktion och PIPER barnhumanmodellens respons för variationer i höftbälte studerades. Interaktionerna med höften och bukorganen var relaterade till skador på levern och njurarna genom att jämföra med publicerad data. Denna studie påvisade att den generella robustheten av modellen kunde ifrågasättas. Modellen hade ändock högre robusthet med hänsyn på kinematiken, men på grund av de upprepande felen vid simuleringarna, kunde man konstatera att robustheten på den 6åriga PIPER barnhumanmodellen var låg. När höftbältet varierades, både när bilbarnstol varierades såväl som vinkel på höftbälte, kunde man konstatera att den 6åriga PIPER barnhumanmodellen kunde fånga skillnaderna med hänsyn på höftbältets vinkel. Modellen var dessutom kapabel till att fånga känsligheten från det kinematiska perspektivet i form av kinematisk förskjutning, underglidningen samt höftens interaktion med höftbältet. Modellen påvisade däremot ingen distinkt känslighet med hänsyn på skador relaterade till bukorganen samt huvudet. Några begränsningar observerades där den 6åriga PIPER barnhumanmodellen indikerade orealistiska skador på huvudet, som var relaterade till modellens överrörlighet. / FFI, Assessment of Passenger Safety in Future Cars

Performing multiple tasks simultaneously is proposed to have an influence on the amount of mental resources available for attending to incoming stimuli’s. Concentration is presumed to be divided between focussing on driving (incoming visual information) while attending to incoming auditory information. The study aimed to investigate the influence of the tempo of music on concentration and driving ability by means of simulation. Concentration was measured by driving errors (DE) whereas driving ability was measured by lap-times (LT) and elicited behaviour. Four treatment conditions were utilised; that is a no-music (NM) control condition, low tempo music (LTM)-, medium tempo music (MTM)- and high tempo music (HTM) treatment conditions. Results found that the tempo of music does not have an influence on concentration; however, significant results were obtained indicating that the tempo of music does have an influence on driving behaviour. / Psychology / M.A. Soc. Sc. (Psychology)

Submitted by Daniele Amaral (daniee_ni@hotmail.com) on 2017-10-09T20:25:42Z No. of bitstreams: 1 DissSBML.pdf: 11036305 bytes, checksum: bfd6a7dc18c9f75ffae64cce4523adf4 (MD5) / Approved for entry into archive by Ronildo Prado (bco.producao.intelectual@gmail.com) on 2018-01-25T12:34:11Z (GMT) No. of bitstreams: 1 DissSBML.pdf: 11036305 bytes, checksum: bfd6a7dc18c9f75ffae64cce4523adf4 (MD5) / Approved for entry into archive by Ronildo Prado (bco.producao.intelectual@gmail.com) on 2018-01-25T12:34:20Z (GMT) No. of bitstreams: 1 DissSBML.pdf: 11036305 bytes, checksum: bfd6a7dc18c9f75ffae64cce4523adf4 (MD5) / Made available in DSpace on 2018-01-25T12:39:08Z (GMT). No. of bitstreams: 1 DissSBML.pdf: 11036305 bytes, checksum: bfd6a7dc18c9f75ffae64cce4523adf4 (MD5) Previous issue date: 2017-08-28 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Aluminum alloys are widely used in transportation industry to reduce structural weight and fuel consumption. The development of advanced alloys and more effective technologies for joining materials contribute to achieve such objectives. AlMgSc alloys emerge as an interesting option to structural applications due to low density and high mechanical performance, as well as an attractive cost. Friction spot welding (FSpW) process is a novel solid state joining technology that has proven to be suitable for joining lightweight materials. This process is carried out in a few steps and in a short time with low thermal cycles and energy consumption as well as without extra materials addition. Thus, this process is an alternative to industrial techniques such as riveting and resistance spot welding. This work presents, for the first time, the application results of FSpW on AlMgSc sheets in overlapping configuration. The effect of the process parameters, such as rotational speed, plunge depth and plunge time, was investigated in order to obtain joints with higher lap shear strength. The Taguchi method and the analysis of variance were applied to study the influence of each parameter on mechanical properties of the joints. In addition, the welds were submitted to microstructural characterization and a material flow analysis provided an initial understanding about the formation of microstructural features. Therefore, the fatigue performance was analyzed for the condition of higher lap shear strength and the S-N curve was drawn. The results indicated a good static performance of the welds, although the fatigue performance was less satisfactory. Finally, failure mechanisms of static and dynamic tests seemed to be strongly related to geometric features, such as hook, bonding ligament and microstructural transition regions. / Ligas de alumínio são amplamente utilizadas em indústrias de transporte visando a redução do peso estrutural e consumo de combustíveis. O desenvolvimento de ligas avançadas e tecnologias mais efetivas de união contribuem para o alcance de tais objetivos. Ligas do sistema AlMgSc surgem como opção interessante para utilização estrutural devido à baixa densidade e alto desempenho mecânico, aliados a um custo atrativo. O processo de soldagem a ponto por fricção (FSpW) é uma tecnologia recente de união de materiais no estado sólido, que tem se mostrado adequado para a união de ligas leves. Tal processo é realizado em poucas etapas e curto tempo, com baixos ciclos térmicos e consumo energético e sem adição de materiais extras, se mostrando, portanto, uma alternativa a técnicas utilizadas industrialmente, como rebitagem e solda a ponto por resistência. Esse trabalho apresenta, pela primeira vez, resultados de aplicação do FSpW em chapas AlMgSc sobrepostas. O efeito dos parâmetros do processo, como velocidade de rotação, profundidade e tempo de penetração da ferramenta, foi investigado visando a obtenção de soldas com maior resistência em ensaios de cisalhamento, dita condição otimizada. Para tal, foi aplicado o método Taguchi e análise de variância para estudar a importância de cada parâmetro na resistência mecânica das juntas. Além disso, as soldas foram caracterizadas microestruturalmente e uma análise do fluxo de material proporcionou um entendimento inicial acerca da formação de algumas características microestruturais. Ademais, o desempenho em fadiga foi analisado para a condição otimizada de soldagem e a curva S-N foi levantada. Os resultados obtidos apontam um bom desempenho estático das soldas, embora o desempenho em fadiga tenha sido menos satisfatório. Finalmente, os mecanismos de falha, de ensaios estáticos e dinâmicos, foram observados e se mostraram fortemente relacionados a elementos geométricos, como cunha, e linha de união, além de regiões de transições microestruturais. / CNPq: 134654/2016-1

Pour les structures aéronautiques, les zones sensibles à la corrosion sont principalement celles où le plan de protection de la structure peut être mis en défaut, comme à l’intérieur des joints de recouvrement (dénommé «lap joint» en anglais). Les assemblages de tôles métalliques réalisés par recouvrement en utilisant, par exemple le rivetage, peuvent présenter des défauts de contact et donc il peut exister un interstice entre les deux parties de l’assemblage. En général cet interstice est isolé de l’environnement extérieur par un mastic. Mais il y a un risque de piégeage d’humidité plus ou moins concentrée en ions agressifs qui peut provoquer des endommagements ou aggraver ceux initiés sur des défauts des revêtements. Le premier objectif de cette thèse est de développer une méthodologie permettant de reproduire, de manière contrôlée et de façon la plus représentative de cas réels, la corrosion d’un alliage d’aluminium 2024-T3 constituant un joint de recouvrement afin d’effectuer des observations complétées par des mesures chimiques et électrochimiques. Le deuxième objectif est de tester l’application de modèles de transport réactif (en milieu confiné) pour voir s’il est possible de simuler les réponses (chimiques ou électrochimiques) mesurées expérimentalement et donc de prédire sur le long terme l’évolution d’un assemblage. / For aircraft structures, corrosion sensitive areas are mainly those where the protection of the structure may suffer local breakdowns, as encountered inside lap joints. The assemblies of metal plates by overlapping (riveting) may present some defects in contact and consequently a gap can exist between the two parts of the assembly. Typically this gap is isolated from the outside environment by a sealant. But there is a risk of trapping of moisture more or less concentrated in aggressive ions which can induce corrosion or increase the damages initiated on coating defects. The first objective of this thesis is to develop a methodology to reproduce in a controlled manner and in the most representative way regarding actual cases, the corrosion of a lap joint made of aluminum alloy 2024- T3 plates, to perform not only observations but also chemical and electrochemical measurements. The second objective is to test the application of reactive transport models (in confined media) to check if it is possible to simulate the chemical or electrochemical changes recorded during experiments and thus to predict the long-term evolution of lap-joint in humid environment.

Plasma pretreatments are environmentally benign and energy efficient processes for modifying the surface chemistry of materials. In an effort to improve the strength of the titanium alloy/FM-5 polyimide adhesive joint for aerospace applications, oxygen plasma pretreatments and novel thin plasma polymerized (PP) films were investigated as adhesion promoters. Plasma treatments were carried out using custom-built, low pressure, radio frequency, inductively coupled plasma reactors. Ti-6Al-4V coupons were plasma treated and used to prepare miniature single lap shear (SLS) joints. The effects of plasma pretreatments on surface chemistry were studied using x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), Fourier transform infrared analysis (FTIR), and contact angle measurements. Relationships between composition, mechanical properties, and adhesion of PP films on Ti-6Al-4V and silicon wafers were investigated. The nanomechanical properties (modulus, hardness and adhesion) were studied using atomic force microscopy (AFM) nanoindentation and nanoscratch testing. A design of experiments (DOE) three factorial model was used to optimize the parameters for oxygen plasma treatments. Oxygen plasma pretreatments enhanced joint strength by cleaning the titanium surface and creating an extended oxide layer. Nanoindentation of oxygen plasma treated substrates showed no change in the surface mechanical properties due to the oxygen plasma treatment. This suggested that the improved SLS strength of the oxygen plasma pretreated substrates was due to the cleaning of the substrate and the removal of carbonaceous contaminants, rather than any changes in the morphology of the oxide layer. PP acetylene films were predominantly carbon, with oxygen as the other main constituent (incorporated mostly as C-O and C=O). For all SLS specimens tested, the adhesion between PP acetylene and FM-5 adhesive was adequate. However, the strength of SLS joints was limited by the adhesion of the PP acetylene to the Ti-6Al-4V substrate. The effects of a large number of plasma parameters, such as substrate pretreatment, carrier gas, input power, flow rate and film thickness were investigated. All samples failed at the PP film/Ti-6Al-4V interface or within the PP acetylene film, and thicker PP films yielded lower SLS strengths. PP films deposited at lower power exhibited higher hardness and reduced modulus than films deposited at higher power. Overall, thinner films exhibited higher hardness and reduced Young's modulus than thicker films. PP films of higher hardness yielded higher critical loads at debond (thickness normalized) during the nanoscratch test. Thin films were developed via the vapor plasma polymerization of titanium(IV) isobutoxide (TiiB). XPS results suggested that titanium was incorporated into the film as TiO2 clusters dispersed in an organic matrix. No evidence for Ti-C was obtained from the XPS spectra. PP films of TiiB were much more compliant than PP acetylene films. This behavior was attributed to decreased fragmentation and lower crosslinking that occurred during PP TiiB film deposition. These PP films did not exhibit sol-gel-like qualities, and because of the way titanium was incorporated into the films, a more appropriate name for these films might be "titanium dioxide-doped plasma polymerized films." / Ph. D.

In the automotive industry a commonly used material is thin steel sheets coated with a thin layer of zinc for corrosion resistance purposes. Welding of this material, with the high temperatures involved, causes problems with zinc burn-off leading to reduced corrosion resistance. The zinc evaporation also causes arc disturbances leading to spatter formation, pores and difficulties achieving good visual weld quality. The joints are in many cases visible or semi-visible (e.g. visible after opening a door) and “A-grade” quality is demanded, meaning no visible discontinuities are allowed. It also implies a smooth and generally appealing appearance of the joint.An alternative to welding is brazing, and laser brazing meets the requirements but the process is associated with high costs. In the national project “LEX-B”, funded by Vinnova, the possibilities of using arc brazing, in particular one MIG/MAG brazing and two TIG brazing processes, for some automotive applications are investigated. This master thesis is connected to the first part of the project and aims at compiling data for making a selection of the most promising process to investigate and optimise further. LEX-B is conducted in cooperation between Swerea KIMAB, Volvo Trucks, Scania CV and University West. The joint of interest is a lap joint between bottom and upper sheets of 1.2 mm and 0.8 mm respectively that represents a joint on the side of a truck cabin. The requirements are visual A-grade quality and tensile shear strength of 300 MPa.In the project the MIG/MAG process Cold Metal Transfer (CMT) was compared to the TIG processes forceTIG and Plasmatron. CMT was experimentally investigated while the results for the other two processes were obtained partly from a previous study and partly from Volvo Trucks where tests were performed simultaneously. A system for measuring data for the process was developed, test specimens were brazed and examined visually and mechanical destructive testing was performed to ensure the tensile shear strength. Parameter studies were done for further process optimisation. / Inom fordonsindustrin är ett ofta använt material stål i tunna ark belagda med zink p.g.a. zinkets korrossionsskyddande egenskaper. Vid svetsning av detta material uppstår problem med zink som förångas vilket leder till minskad korrosionsbeständighet. Förångningen av zink orsakar också störningar av ljusbågen vilket leder till sprut, porer och svårighet att uppnå god visuell svetskvalitet. Fogarna är i många fall synliga eller delvis synliga (t.ex. synlig efter att ha öppnat en dörr) och "A-kvalitet" efterfrågas, vilket innebär att inga synliga diskontinuiteter tillåts. Fogen ska upplevas jämn och tilltalande.Lödning är ett alternativ till svetsning, och laserlödning är en process som uppfyller kraven men är förknippad med höga kostnader. I det nationella projektet "LEX-B", som finansieras av Vinnova, undersöks möjligheterna att använda båglödning, specifikt en MIG/MAG-process och två TIG-processer, för dessa applikationer. Detta examensarbete är anslutet till den första delen av projektet och syftar till ta fram underlag för att välja den mest lovande av dessa processer för vidare utredning och optimering. LEX-B sker i samarbete mellan Swerea KIMAB, Volvo Lastvagnar, Scania CV och Högskolan Väst. Den undersökta fogen är en överlappsfog mellan en undre plåt med 1,2 mm tjocklek och en övre plåt med 0,8 mm tjocklek. Detta representerar en fog på sidan av en lastbilshytt. Kraven är visuell A-kvalitet och en drag-skjuvhållfasthet av 300 MPa.I projektet jämfördes MIG/MAG-processen Cold Metal Transfer (CMT) med TIG-processerna forceTIG och Plasmatron. CMT testades experimentellt medan resultaten för de övriga två processerna erhölls dels från tidigare tester och dels från Volvo Lastvagnar där tester utfördes parallellt. Ett mätsystem for att dokumentera processdata utvecklades och de framställda lödfogarna undersöktes visuellt och med mekanisk förstörande provning för att säkerställa drag-skjuvhållfastheten. Parameterstudier gjordes för vidare optimering av processen.

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Water-assisted crack growth at an epoxy/glass interface was measured as a function of applied strain energy release rate, G, and temperature using a wedge test geometry. The specimens consist of two glass plates bonded with a thin layer of proprietary epoxy adhesive. The crack fronts along the epoxy/glass interfaces were measured using an optical stereomicroscope. The relationship between G and the debonding rate, v, can be measured using this method, and the threshold value of strain energy release rate, Gth, can be determined from the measured data. Two types of testing procedures were conducted in this study: ex situ, i.e., pre-conditioned wedge tests and in situ ones, in which wedges were applied before the specimens were submerged into water. A preliminary model was developed based on the thermal activation barrier concept, and allows the prediction of Gth for the temperatures beyond the testing region. Changes in interfacial strain energy release rate caused by thermal residual stresses in a triple-layered specimen were analyzed in Chapter Three. The method is based on linear elastic fracture mechanics and simple beam theory. The curvature of a bimaterial strip was chosen to characterize the residual stress in the specimen, and the strain energy release rate, caused by both tensile and compressive residual stresses in the adhesive, was derived for an asymmetric double cantilever beam (ADCB) geometry. The contribution of the thermal residual and mechanical stress to the global energy release rate was analyzed. The thermally induced energy release rate, GT, is found to be independent of crack length, but is a function of residual stress level and geometric and material parameters of the specimen. The adhesion of films and coatings to rigid substrates is often measured using blister geometries, which are loaded either by an applied pressure or a central shaft. The measurement will be affected if there are residual stresses that make a contribution to the energy release rate. This effect is investigated using analytical solutions based on the principle of virtual displacements. A geometrically nonlinear finite element analysis is conducted for comparison. Furthermore, the relationships among strain energy release rate, load, deflection, and fracture radius are discussed in detail in Chapter Four. Both analytical solutions and numerical results reveal that uniform tensile residual stresses reduce a specimen's deflection if it experiences plate behavior under small loads. However, this effect diminishes when membrane behavior is dominant. The mechanics of a single-lap joint with different boundary conditions subjected to tensile loading are investigated. Closed-form solutions are obtained for a specimen configuration considering different clamping methods. Based on the approach pioneered by Goland and Reissner, the solutions reported in this paper provide a simple but useful way to understand the effects of boundary conditions on this test geometry. The solutions in this study suggest that different grip configurations mainly affect the response of the specimens if the grip position is close to the joint edge or the loads are small. Generally, the influence caused by different gripping methods is only limited to the boundary region, and the behavior of the joint part subjected to tensile loading is almost the same as that for a simply-supported case. / Ph. D.