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  • Kumara, Chamara
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Microstructure Modelling of Additive Manufacturing of Alloy 7182018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In recent years, additive manufacturing (AM) of Alloy 718 has received increasing interest in the field of manufacturing engineering owing to its attractive features compared to those of conventional manufacturing methods. The ability to produce complicated geometries, low cost of retooling, and control of the microstructure are some of the advantages of the AM process over traditional manufacturing methods. Nevertheless, during the building process, the build material undergoes complex thermal conditions owing to the inherent nature of the process. This results in phase transformation from liquid to solid and solid state. Thus, it creates microstructural gradients in the built objects, and as a result,heterogeneous material properties. The manufacturing process, including the following heat treatment that is used to minimise the heterogeneity, will cause the additively manufactured material to behave differently when compared to components produced by conventional manufacturing methods. Therefore, understanding the microstructure formation during the building and subsequent post-heat treatment is important, which is the objective of this work. Alloy 718 is a nickel-iron based super alloy that is widely used in the aerospace industry and in the gas turbine power plants for making components subjected tohigh temperatures. Good weldability, good mechanical properties at high temperatures, and high corrosion resistance make this alloy particularly suitablefor these applications. Nevertheless, the manufacturing of Alloy 718 components through traditional manufacturing methods is time-consuming and expensive. For example, machining of Alloy 718 to obtain the desired shape is difficult and resource-consuming, owing to significant material waste. Therefore, the application of novel non-conventional processing methods, such as AM, seems to be a promising technique for manufacturing near-net-shape complex components.In this work, microstructure modelling was carried out by using multiphase-field modelling to model the microstructure evolution in electron beam melting (EBM) and laser metal powder directed energy deposition (LMPDED) of Alloy 718 and x subsequent heat treatments. The thermal conditions that are generated during the building process were used as input to the models to predict the as-built microstructure. This as-built microstructure was then used as an input for the heat treatment simulations to predict the microstructural evolution during heat treatments. The results showed smaller dendrite arm spacing (one order of magnitude smaller than the casting material) in these additive manufactured microstructures, which creates a shorter diffusion length for the elements compared to the cast material. In EBM Alloy 718, this caused the material to have a faster homogenisation during in-situ heat treatment that resulting from the elevated powder bed temperature (> 1000 °C). In addition, the compositional segregation that occurs during solidification was shown to alter the local thermodynamic and kinetic properties of the alloy. This was observed in the predicted TTT and CCT diagrams using the JMat Pro software based on the predicted local segregated compositions from the multiphase-field models. In the LMPDED Alloy 718 samples, this resulted in the formation of δ phase in the interdendritic region during the solution heat treatment. Moreover, this resulted in different-size precipitation of γ'/γ'' in the inter-dendritic region and in the dendrite core. Themicro structure modelling predictions agreed well with the experimental observations. The proposed methodology used in this thesis work can be an appropriate tool to understand how the thermal conditions in AM affect themicro structure formation during the building process and how these as-built microstructures behave under different heat treatments.

  • Nordström, Malin
    et al.
    University West, Department of Social and Behavioural Studies, Division for Educational Science and Languages.
    Moisio, Rebekka
    University West, Department of Social and Behavioural Studies, Division for Educational Science and Languages.
    Det är okej att vara blyg: En studie om hur pedagoger arbetar med blyga barn i förskolan2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Bakgrund: Studien bygger på pedagogers arbete med blyga barn i förskolans verksamhet. Under vår utbildning till förskollärare har vi saknat att ta del av området men även för att fördjupa oss hur tidigare forskning beskriver arbetet kring blyga barn. Skolverket (2016 s 12) menar att barnen ska "utveckla sin förmåga att uttrycka sina tankar och åsikter och därmed få möjlighet att påverka sin situation". Tystlåtna barn har lättare för att försvinna i mängden och därmed funderar vi på om blyga barn får en chans till att leva upp till läroplansmålet eller förblir osynliga.

    Syfte: Vårt syfte är att få en bredare förståelse för hur pedagoger arbetar med blyga barn i förskolan.

    Metod: Fem verksamma pedagoger intervjuades i fyra olika förskolor. Vi kontaktade varje förskolechef via telefon där vi kort beskrev vår studie. Varje intervju spelades in för att i efterhand transkriberas från tal till skrift, detta för att underlätta vår analysprocess. Vi granskade, jämförde och letade sedan efter likheter och skillnader mellan intervjuerna.

    Resultat: Det visade sig att blyghet är ett vanligt förekommande fenomen i förskolan och att det är pedagogens viktiga roll att ständigt bemöta och stötta blyga barn. Det framgår hur pedagoger upptäcker blyga barn samt hur de arbetar genom flera olika sätt för att stötta dessa barn.

  • Danielsson, John
    University West, School of Business, Economics and IT, Divison of Informatics.
    Lokomotion i ett gyllene snitt: En observationsstudie av naturtrogna och uttryckslösa kroppsrörelser med en metod designad för naturalistisk karaktärsanimation.2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In aspiration to achieve naturalistic character animation, some difficulty does show up, both in 3D-CGI, 2D-CGI as in traditional handmade animation. The reason why difficulty appears in the task of achieving naturalism is for instance because of the simulated natural laws in the digital world which cannot affect the characters cinematic movement. The result of illustrating the natural law manually by hand can affect the illusion of the movement as not naturalistic or inconsistent, which can result in that the spatial adaptation to space is not perceived as naturalistic. It is most often up to the animator to make a believable illusion of the natural laws. This study examines a deeper understanding of the human way to behave and to adapt to the physical reality and through that, apply this movement on character animation.

    The purpose of a deeper understanding of movement's phenomena is to find a clearer method dedicated to naturalistic movement that can be adapted to all forms of character animation, regardless of the character anatomy. Unfortunately, it would not be possible to study all aspects of the physically adaptive behaviors as to the size of the topic. This study will therefore orbit the human locomotion, also known as walking. Focus will therefore be on the bottom part of the body, from the pelvis down to the ankles. There are scientists that do argue about a connection between the golden ratio and the human locomotion. This study is an attempt to apply the golden ratio on 3D-characters.

    This study has been devoted to a different approach in the character animation, where its starting point will be mathematical equations. For this study, it has meant an application of the golden section in a temporary form, that is in motion.

    The result is therefore a mathematically based method dedicated to imitating naturalistic movement in terms of time, that is to say human locomotion. The method has been proved to be useful even in the imitation of characters movements that do not possess human proportions.

  • Lind, Maria
    et al.
    University West, Department of Health Sciences, Section for nursing - undergraduate level.
    Appasi, Bisan
    University West, Department of Health Sciences, Section for nursing - undergraduate level.
    Att se människan bakom sjukdomen är som att lösa en gåta: En litteraturbaserad studie om vårdpersonalens erfarenheter av personcentrerad vård vid beteendemässiga och psykiska symtom vid demens (BPSD)2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Background: There are around 150.000 people with dementia in Sweden. It is common to suffer from BPSD sometime during the course of the disease, which adversely affects the quality of life. Symptoms cause impairment to varying degrees, making everyday life difficult to handle independently. Person-centered care means seeing the person behind the disease and it is necessary to find the cause of behavior and to compensate for loss of function. Knowledge of experience of working person-centered is a prerequisite for being able to provide staff with necessary support.

    Aim: To highlight healthcare professionals' experiences of person-centered care in BPSD.

    Method: This is a qualitative literature study based on 12 scientific articles.

    Result: The main themes that emerged were: Own conditions and obstacles, External conditions and obstacles and Contradictory feelings at work. With associated subthemes: Seeing the person behind the disease, To balance between strategies and routines,To take personal responsibility, To have knowledge and experience, Being in need of support and cooperation, To meet organizational / environmental factors, To have access to background information, To feel success and satisfaction and To feel insufficient and powerless.

    Conclusion: Several conditions that favor dementia care emerged from the results, but there were also factors and obstacles that hampered nursing work. Person-centered work practices increase the possibility of well-being for all involved. In order to care for people with dementia with a person-centered approach, more research in the subject, more resources and in-depth education is required.

  • Balachandramurthi Ramanathan, Arun
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Fatigue Properties of Additively Manufactured Alloy 7182018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Additive Manufacturing (AM), commonly known as 3D Printing, is a disruptive modern manufacturing process, in which parts are manufactured in a layer-wise fashion. Among the metal AM processes, Powder Bed Fusion (PBF) technology has opened up a design space that was not formerly accessible with conventional manufacturing processes. It is, now, possible to manufacture complex geometries, such as topology-optimized structures, lattice structures and intricate internal channels, with relative ease. PBF is comprised of Electron Beam Melting (EBM) and Selective Laser Melting (SLM) processes.

    Though AM processes offer several advantages, the suitability of these processes to replace conventional manufacturing processes must be studied in detail; for instance, the capability to produce components of consistent quality. Therefore, understanding the relationship between the AM process together with the post treatment used and the resulting microstructure and its influence on the mechanical properties is crucial, to enable manufacturing of high-performance components. In this regard, for AM built Alloy 718, only a limited amount of work has been performed compared to conventional processes such as casting and forging. The aim of this work, therefore, is to understand how the fatigue properties of EBM and SLM built Alloy 718, subjected to different thermal post-treatments, is affected by the microstructure. In addition, the effect of as-built surface roughness is also studied.

    Defects can have a detrimental effect on fatigue life. Numerous factors such as the defect type, size, shape, location, distribution and nature determine the effect of defects on properties. Hot Isostatic Pressing (HIP) improves fatigue life as it leads to closure of most defects. Presence of oxides in the defects, however, hinders complete closure by HIP. Machining the as-built surface improves fatiguelife; however, for EBM manufactured material, the extent of improvement is dependent on the amount of material removed. The as-built surface roughness, which has numerous crack initiation sites, leads to lower scatter in fatigue life. In both SLM and EBM manufactured material, fatigue crack propagation is transgranular. Crack propagation is affected by grain size and texture of the material.

  • Karimi Neghlani, Paria
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Electron beam melting of Alloy 718: Influence of process parameters on the microstructure2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Additive manufacturing (AM) is the name given to the technology of building 3D parts by adding layer-by-layer of materials, including metals, plastics, concrete, etc. Of the different types of AM techniques, electron beam melting (EBM), as a powder bed fusion technology, has been used in this study. EBM is used to build parts by melting metallic powders by using a highly intense electron beam as the energy source. Compared to a conventional process, EBM offers enhanced efficiency for the production of customized and specific parts in aerospace, space, and medical fields. In addition, the EBM process is used to produce complex parts for which other technologies would be either expensive or difficult to apply. This thesis has been divided into three sections, starting from a wider window and proceeding to a smaller one. The first section reveals how the position-related parameters (distance between samples, height from build plate, and sample location on build plate) can affect the microstructural characteristics. It has been found that the gap between the samples and the height from the build plate can have significant effects on the defect content and niobium-rich phase fraction. In the second section, through a deeper investigation, the behavior of Alloy 718 during the EBM process as a function of different geometry-related parameters is examined by building single tracks adjacent to each other (track-by-track) andsingle-wall samples (single tracks on top of each other). In this section, the main focus is to understand the effect of successive thermal cycling on microstructural evolution. In the final section, the correlations between the main machine-related parameters (scanning speed, beam current, and focus offset) and the geometrical (melt pool width, track height, re-melted depth, and contact angle) and microstructural (grain structure, niobium-rich phase fraction, and primary dendrite arm spacing) characteristics of a single track of Alloy 718 have been investigated. It has been found that the most influential machine-related parameters are scanning speed and beam current, which have significant effects on the geometry and the microstructure of the single-melted tracks.