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Sökning: db:Swepub > Övrigt vetenskapligt > Högskolan Väst > Licentiatavhandling

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1.
  • Anderberg, Staffan, 1981- (författare)
  • A study of process planning for metal cutting
  • 2009
  • Licentiatavhandling (övrigt vetenskapligt)abstract
    • Process planning as a function for competitiveness is often neglected. However, as an intermediary between product development and manufacturing, it holds a key function in transforming product specifications and requirements into a producible process plan. Demands and requirements should be met concurrently as manufacturing costs and lead times are minimised. The focus of this thesis is the act of process planning, where the use of better methodologies, computer-aids and performance measurements are essential parts. Since process planning has the function of transforming demands and requirements, changing customer and regulative requirements are vital to regard. Since environmentally benign products and production increases in importance, the research presented in this thesis includes a CNC machining cost model, which relates machining costs to energy consumption.  The presented results in this thesis are based on quantitative and qualitative studies in the metal working industry. This thesis has contributed to an enhanced understanding of process planning to achieve better performance and important areas for improvements. Despite a 50 year history of computerised process planning aids, few of these are used in the industry, where manual process planning activities are more common. Process planning aids should be developed around the process planner so that non-value adding activities, such as information management and documentation are minimised in order to allow more resources for value adding activities, such as decision making. This thesis presents a study of systematic process planning in relation to perceived efficiency. This correlation could however not be verified, which opens up for further studies of other possible explanations for process planning efficiency. Process planning improvements in the industry are difficult to make, since there is little focus on process planning activities and limited knowledge about actual performance hereof. This means that measures taken regarding process planning development are difficult to verify.
2.
  • Bernhard, Irene, et al. (författare)
  • E-government and E-governance - Swedish Case Studies with Focus on the Local level
  • 2013
  • Licentiatavhandling (övrigt vetenskapligt)abstract
    • The concepts of e-government and e-governance are used interchangeably in most research and there is no single definition of these terms. The objective of this licentiate thesis is to provide a deeper understanding of these concepts through empirical studies in a Swedish context. Further, it aims to analyse whether – and if so in what way – the implementation of local contact centres (CC) affect conditions for local planning. This is reported in three articles. In this thesis e-government is defined to as the use of tools and systems by governmental bodies made possible by ICT that affect the organization of public administration. E-governance is defined as the ICT-based networks of services and administration in New Public Management settings including both public and private actors. Case study methodology is used as research method, including interviews, focus group studies, document studies, and some participatory observations. The analysis is partly built on an inductive methodological approach, since this is a new, emerging field of innovative policy and practice. Based on a theoretical discussion of New Public Management in the digital era, findings show that there is a difference between the concepts of e-government and e-governance from the perspective of e-administration and e-services and that the terms should not be used interchangeably. The study indicates that there are examples of implementation that are referred to the e-governance setting. Further the study indicates that local municipal contact centres may be referred to not only as an implementation of e-government but as a combination of e-governance and e-government. The findings indicate that there is a potential for positive impact on the conditions for local planning through the implementation of municipal contact centres.
3.
  • Broberg, Patrik, 1983- (författare)
  • Towards Automation of Non-Destructive Testing of Welds
  • 2011
  • Licentiatavhandling (övrigt vetenskapligt)abstract
    • All welding processes can give rise to defects that will weaken the joint and can lead to failure of the welded structure. Because of this, non-destructive testing (NDT) of welds have become increasingly important to ensure the structural integrity when the material becomes thinner and stronger and welds become smaller; all to reduce weight in order to save material and reduce emissions due to lighter constructions.Several NDT methods exists for testing welds and they all have their advantages and disadvantages when it comes to the types and sizes of defects that are detectable, but also in the ability to automate the method. Several methods were compared using common weld defects to determine which method or methods were best suited for automated NDT of welds. The methods compared were radiography, phased array ultrasound, eddy current, thermography and shearography. Phased array ultrasound was deemed most suitable for detecting the weld defects used in the comparison and for automation and was therefore chosen to be used in the continuation of this work. Thermography was shown to be useful for detecting surface defects; something not easily detected using ultrasound. A combination of these techniques will be able to find most weld defects of interest.Automation of NDT can be split into two separate areas; mechanisation of the testing and automation of the analysis, both presenting their own difficulties. The problem of mechanising the testing has been solved for simple geometries but for more general welds it will require a more advance system using an industrial robot or similar. Automation of the analysis of phased array ultrasound data consists of detection, sizing, positioning and classification of defects. There are several problems to solve before a completely automatic analysis can be made, including positioning of the data, improving signal quality, segmenting the images and classifying the defects. As a step on the way towards positioning of the data, and thereby easing the analysis, the phase of the signal was studied. It was shown that the phase can be used for finding corners in the image and will also improve the ability to position the corner as compared to using the amplitude of the signal. Further work will have to be done to improve the signal in order to reliably analyse the data automatically.
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4.
  • Carlsson, Henrik, 1979- (författare)
  • Reliable Virtual Commissioning
  • 2012
  • Licentiatavhandling (övrigt vetenskapligt)abstract
    • Virtual commissioning is a technique for programming, optimising and verifying industrial automated production, such as robot controllers and programmable logic controllers (PLC), off-line in a simulated environment. Compared with traditional robot off-line programming and simulation, the scope is wider and can include an entire production cell.Robot simulation is a well-established technique and widely used in industry today, much thanks to the RRS interface that enables simulated robot control systems to be integrated in the simulation software. A more general interface for industrial control system integration is OPC that has been an industrial de facto standard for connection between industrial control systems and regular PCs. State-of-the-art production simulation tools often include the possibility to connect an industrial control system via OPC. However, OPC suffers a major drawback when it comes to production simulation, there is no mechanism that synchronises the industrial control system with the simulation and this could lead to unreliable results from the simulation.Another obstacle for virtual commissioning is the amount of time that needs to be spent during the simulation model building phase, since virtual commissioning includes more signals. This does not only take more time, but it is also an error prone process that might lead to unreliable results.In this thesis problems related to the OPC interface and the modelling process are discussed, and suggestions how these issues can be solved are presented so reliable virtual commissioning can be achieved.
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5.
  • Charles, Corinne, 1979- (författare)
  • Modelling microstructure evolution of weld deposited Ti-6Al-4V
  • 2008
  • Licentiatavhandling (övrigt vetenskapligt)abstract
    • The microstructure and consequently the mechanical properties of titanium alloys are highly dependent on the temperature history endured by the material. The manufacturing process of metal deposition induces repetitive cooling and heating in the material determining a specific microstructure. The presented study is devoted to developing and implementing a microstructure model for Ti-6Al-4V intended to be coupled to a thermo- mechanical model of the metal deposition process.Microstructural analysis of the metal deposited samples was first performed to understand the formed microstructure. A set of representative parameters for microstructure modelling were then selected as representative for the known impact of Ti-6Al-4V microstructure on mechanical properties. Evolution equations for these parameters were implemented for thermal finite element analysis of the process. Six representative state variables are modelled: the phase volume fraction of total alpha, beta, Widmanstätten alpha, grain boundary alpha, martensite alpha, and the alpha lath thickness. Heating, cooling and repeated re-heating involved in the process of metal deposition are taken into account in the model. The phase transformations were modelled based on a diffusionnal theory described by a Johnson-Mehl-Avrami formulation, as well as diffusionless transformations for the martensite alpha formation and the beta reformation during reheating. The Arrhenius equation is applied as a simplification to model temperature dependent alpha lath size calculation. Grain growth is not included in the present formulation, but would have to be added for capturing alpha lath coarsening during long term heat treatment.The temperature history during robotised tungsten inert gas deposition welding is simulated together with the microstructure. The implementation of the model handles well the complex cyclic thermal loading from the metal deposition process. A particular banded structure observed in the metal deposited microstructure is partially explained using the proposed microstructure model. It is concluded that although qualitatively interesting results have been achieved, further calibration testing over a wider range of temperature histories must be performed to improve the transformation kinetic parameters for reliable quantitative predictions of the microstructure.
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6.
  • Curry, Nicholas, 1984- (författare)
  • Design of Thermal Barrier Coating Systems
  • 2012
  • Licentiatavhandling (övrigt vetenskapligt)abstract
    • Thermal barrier coatings (TBC’s) are used to provide both thermal insulation and oxidation protection to high temperature components within gas turbines. The development of turbines for power generation and aviation has led to designs where the operation conditions exceed the upper limits of most conventional engineering materials. As a result there has been a drive to improve thermal barrier coatings to allow the turbine to operate hotter for longer.The focus of this study has been the development of a new generation of TBC system for industrial implementation. The goal for these new coatings was to achieve lower conductivity and longer lifetime than those coatings used today. The route taken to achieve these goals has been twofold. Firstly an alternative stabiliser has been chosen for the zirconium oxide system in the form of dysprosia. Secondly, Control of the powder morphology and spray parameters has been used to generate coating microstructures with favourable levels of porosity.Samples have been heavily characterised using the laser flash technique for evaluation of thermal properties. Measurements were performed at room temperature and at intervals up to 1200°C. Samples have also been tested in their as produced state and after heat treatments of up to 200 hours.Lifetime evaluation has been performed using the thermo-cyclic fatigue test to expose coating systems to successive cycles of heating and cooling combined with oxidation of the underlying metallic coating.Microstructures have been prepared and analysed using SEM. An image analysis routine has been used to attempt to quantify changes in microstructure features between coating types or coating exposure times and to relate those changes to changes in thermal propertiesResults show that dysprosia as an alternative dopant gives a reduction in thermal conductivity. While small at room temperature and in the as produced state; the influence becomes more pronounced at high temperatures and with thermal exposure time. Overall, the greatest sustained influence on thermal conductivity has been from creating coatings with high levels of porosity.In relation to lifetime, the target of double the thermo-cyclic fatigue life was achieved using a coating with engineered porosity. Introducing a polymer to the spray powder helps to generate large globular pores within the coating together with a large number of delaminations. Such a structure has shown to be highly resistant to TCF testing.
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7.
  • De Backer, Jeroen, 1987- (författare)
  • Robotic Friction Stir Welding for Flexible Production
  • 2012
  • Licentiatavhandling (övrigt vetenskapligt)abstract
    • Friction Stir Welding eller ”friktionsomrörningssvetsning” är en svetsprocess som kräver ett roterande verktyg som genom friktionsvärme får materialet att mjukna. Verktyget blandar runt det plastiska materialet mekaniskt och skapar en fog av hög kvalité. Processen fungerar utan gas, utan rök, utan tillsatsmaterial och utan att smälta materialet. Alla dessa fördelar skapar stort industriellt intresse inom flera branscher. Idag används tekniken nästan uteslutande i styva maskiner som svetsar raka eller cirkulära fogar och framförallt för aluminium. Eftersom processen kräver stora krafter mellan material och verktyg är det svårt att implementera processen på en robot. En robot möjliggör svetsning av tredimensionella geometrier och ökar dessutom flexibiliteten.  Flera forskargrupper runt i världen har tagit fram en fungerande FSW robot som kan svetsa tunn lättviksmaterial som aluminium med hög kvalitet. Användningen i industrin av FSW robotar är däremot obefintlig och det finns ett antal anledningar till det. Först är roboten vek vilket gör att verktyget kan missa svetsfogen i hårda material och svetsdefekter kan uppstå. En annan anledning är at det inte finns en användbar automatiserad processtyrning tillgänglig, mest för att FSW är en robust process och inte kräver en avancerad styrning vid svetsning av raka fogar.De praktiska arbeten som redovisas i denna licentiatuppsats är huvudsakligen utförda i en robotiserad FSW-demonstrator på Högskolan Väst. FSW-roboten är en modifierad industrirobot som är försetts med spindel och kraftåterkoppling för att styra kraften som roboten applicerar på arbetsstycket.Detta arbete har identifierat ett antal problem som behöver lösas för att få en robust robotiserad FSW process i en flexibel produktionsmiljö. I denna licentiatrapport beskrivs en lösning hur en typ av svetsdefekter kan förhindras genom en sensorbaserad bankompensering. Både en kamera- och lasersensor-baserad mätmetod presenteras. En annan bankompenseringsstrategi är beskriven, som använder kraftsensorn från befintlig kraftåterkoppling istället för att lägga till extra sensor. Denna strategi kan utvecklas till en komplett utböjningsmodell på roboten i hela arbetsområdet. Robotens begränsningar gällande svetsbarhet av hårda material har undersökts och med hjälp av parameteroptimering och förvärmning kan även hårda nickelbaserade legeringar svetsas med roboten.
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8.
  • Edstorp, Marcus, 1980- (författare)
  • Weld Pool Simulations
  • 2008
  • Licentiatavhandling (övrigt vetenskapligt)abstract
    • This investigation is devoted to the study of welding and its effect on the workpiece, focusing on the thermo and fluid dynamical phenomena occuring during a autogenous or nonautogenous arc fusion welding process. Its aim is to simulate the behaviour of the weld pool and analyze the consequence of the solid-liquid phase change, thus obtaining a methodology for predicting the appearance of weld defects related to solidification and cooling. In order to accomplish this, we solve equations governing a number of continuum mechanical and electromagnetical quantities, as well as consider the motion of the freely moving boundary of the weld pool. Since the state of these quantities is strongly influenced by phenomena such as arc and droplet impingement, non-isothermal phase change, surface tension, Marangoni forces and Lorentz forces, much effort is necessarily devoted to the modelling of the corresponding fluxes and sources, as well as to the implementation of computationally efficient techniques for simulating the geometrical deformation of the workpiece, which in our setting is entirely determined by the motion of the weld pool surface.Common to all arc fusion welding processes is the employment of a welding arc. Many techniques rely on the arc to clean and shield the workpiece during the process, however in this study we consider it to be its main purpose to cause the local increase of thermal energy that is required for the establishment of the weld pool, and also to exert the mechanical forces that provoke the subsequent fluid flow which enhances heat transfer and facilitates weld penetration. The physics of the welding arc itself is quite intricate, and although the modelling of the arc is not the prime objective of this research project, we conclude that arc forces act on the pool surface, and that the investigation of the arc behaviour is important insofar that it provides input to the pool model and thus enables a more accurate prediction of the quality of the weldment that is created once the pool has solidified
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9.
  • Emilsson, Maria, 1966- (författare)
  • Betydelsen av personlighet och uppfattning om läkemedel för följsamhet till astmamedicinering
  • 2010
  • Licentiatavhandling (övrigt vetenskapligt)abstract
    • En okontrollerad astma kan leda till komplikationer i lungor och luftvägar. Astma kan kontrolleras med läkemedelsbehandling men fullständig astmakontroll uppnås inte alltid. Den vanligaste orsaken till att astmakontrollen inte uppnås är brister i följsamheten till astmamedicinering. Syfte: 1) Att undersöka om personlighetsdrag hos unga vuxna med astma var relaterad till astmakon-troll och hälsorelaterad livskvalitet, samt belysa samband mellan personlighetsdrag och följsamhet till regelbunden a... merstmamedicinering. 2) Att belysa samband mellan personlighetsdrag, uppfattning om läkemedel och följsamhet till astmamedicinering. Material och metod: I Studie I ingick 268 individer (165 kvinnor och 103 män) i åldern 22 år (±1år). I Studie II ingick 35 patienter (25 kvinnor och 10 män) med en medelålder av 52.8 år. I studierna an-vändes frågeformulär för att samla in data om personlighet, följsamhet, astmakontroll, hälsorelaterad livskvalitet och uppfattning om läkemedel. Resultat: Personlighet hade samband med följsamhet till astmamedicinering, uppfattningar om läke-medel, astmakontroll och hälsorelaterad livskvalitet. I Studie I framkom att de som skattade sig mer impulsiva rapporterade lägre följsamhet. Ett negativt samband fanns mellan höga värden i personlig-hetsdraget alexitymi (bristande intresse att förstå och prata om känslor) och följsamhet till astmamedi-cinering hos unga vuxna män. Likaledes framkom ett negativt samband mellan personlighetsdraget antagonism och följsamhet hos unga vuxna män. Hos båda könen var personlighetsdraget negativ af-fektivitet relaterat till dåligt kontrollerad astma. Det indikerades att personlighet kan påverka den men-tala hälsan hos både unga kvinnor och män, medan den fysiska hälsan hade samband med astmakon-troll och fysisk aktivitet. I Studie II framkom att fyra av fem personlighetsdrag hade samband i olika riktningar med uppfattningar om läkemedel. Högt värde i Specefikt-nödvändighetsskalan (uppfattning om nödvändigheten av förskrivna läkemedel) var relaterat till hög grad av följsamhet. Personlighets-draget målmedvetenhet var relaterat till hög följsamhet hos män. Känslomässig instabilitet hade sam-band med lägre värden i följsamhet också hos män. Konklusion: Kunskapen om personlighetens betydelse behöver fördjupas, men uppsatsens resultat indikerar behovet av att identifiera individuella skillnader i personlighet för att öka patienternas följ-samhetsbeteende, stärka deras uppfattning om nödvändigheten av läkemedelsbehandling och minska deras oro för läkemedelsbehandling, vilket har betydelse för både astmakontroll och hälsorelaterad livskvalitet. 
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10.
  • Ericsson, Mikael (författare)
  • Simulation of robotic TIG-welding
  • 2003
  • Licentiatavhandling (övrigt vetenskapligt)abstract
    • Robotised welding is one of the most important robot tasks used in manufacturing industry. The operator usually performs the programming of the robot manually, i.e. by jogging the robot arm to each coordinate pose in space. Programming can, however, be made more accurate by the use of simulation, using so called Computer Aided Robotics. Simulation can also be a powerful tool to evaluate and control welding heat effects, such as unwanted stresses and deformation. The objective of this thesis was to develop a simulation tool and a method by which robot trajectories, temperature histories, residual stresses and distortion can be analysed and optimised off-line. This was performed by integrating robot simulation software with finite element analysis software. A special interface was created allowing information exchange between the two software programs. The method was used to program welding trajectories both for planar plates and for a part of an aerospace component. The trajectories was downloaded to the finite element analysis software where temperature and residual stress prediction were performed. Good agreement was found between the programmed robot trajectory, and the actual trajectory and only small adjustments were necessary. Temperature measurements were performed using both thermocouples and infrared imaging. Good agreement was also found between the results using these two methods. The method developed provides a powerful tool to construct and optimise robot trajectories and welding process parameters off-line.
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