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  • Devotta, Ashwin Moris
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Improved finite element modelingfor chip morphology prediction inmachining of C45E steel2020Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Within the manufacturing of metallic components, machining plays an important role and is of vital significance to ensure process reliability. From a cutting tool design perspective, physics-based numerical modeling that can predict chip morphology is highly necessary to design tool macro geometry. The chip morphology describes the chip shape geometry and the chip curl geometry. Improved chip morphology prediction increases process reliability by improved chip breakability and effective chip evacuation.

    To this end, in this work, a platform is developed to compare a numerical model'schip morphology prediction with experimental results. The investigated cuttingprocesses are orthogonal cutting process and nose turning process. Numerical models that simulate the chip formation process are used to predict the chip morphology accompanied by machining experiments. Computed tomography isused to scan the chips obtained from machining experiments evaluating its ability to capture the chip morphology variation. For the nose turning process, chip curl parameters need to be calculated during the cutting process. Kharkevich model is utilized in this regard for calculating the 'chip in process' chip curl parameters. High-speed videography is used to measure the chip side-flow angle during thecutting process experiments enabling comparison with physics-based model predictions.

    With regards to chip shape predictability, the numerical models that simulate the chip formation process are improved by improving the flow stress models and evaluating advanced damage models. The workpiece material, C45E steel, arecharacterized using Gleeble thermo-mechanical simulator. The obtained flow stress is modeled using phenomenological flow stress models. Existing phenomenological flow stress models are modified to improve their accuracy. The fracture initiation strain component of damage models' influence on the prediction of transition from continuous chip to segmented chip is studied. The flow stress models and the damage models are implemented in the numerical models through FORTRAN subroutines. The prediction of continuous to segmented chip transitions are evaluated for varying rake angles and feed rate ata constant cutting velocity.

    The results from the numerical model evaluation platform show that the methodology provides the framework where an advance in numerical models is evaluated reliably from a 'chip morphology prediction capability' viewpoint forthe nose turning process. The numerical modeling results show that the chip curl variation for varying cutting conditions is predicted qualitatively. The flow stress curves obtained through Gleeble thermo-mechanical simulator show dynamic strain aging presence in specific temperature -strain rate ranges. The results of the phenomenological model modification show their ability to incorporate the dynamic strain aging influence. The modified phenomenological model improvesthe accuracy of the numerical models' prediction accuracy. The flow stress models combined with advanced damage model can predict the transition from continuous to segmented chip. Within damage model, the fracture initiation strain component is observed to influence the continuous chip to segmented chip transition and chip segmentation intensity for varying rake angle and feed rate and at a constant cutting velocity.

  • Goel, Sneha
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Bourreau, Kévin
    University of Limoges, Specialty Materials, Limoges 87000, France.
    Olsson, Jonas
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Klement, Uta
    Chalmers University of Technology, Department of Industrial and Materials Science, Gothenburg 41296, Sweden.
    Joshi, Shrikant V.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Forskningsmiljön produktionsteknik(PTW).
    Can Appropriate Thermal Post-Treatment Make Defect Content in as-Built Electron Beam Additively Manufactured Alloy 718 Irrelevant?2020Inngår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 13, nr 3, artikkel-id 536Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electron beam melting (EBM) is gaining rapid popularity for production of complex customized parts. For strategic applications involving materials like superalloys (e.g., Alloy 718), post-treatments including hot isostatic pressing (HIPing) to eliminate defects, and solutionizing and aging to achieve the desired phase constitution are often practiced. The present study specifically explores the ability of the combination of the above post-treatments to render the as-built defect content in EBM Alloy 718 irrelevant. Results show that HIPing can reduce defect content from as high as 17% in as-built samples (intentionally generated employing increased processing speeds in this illustrative proof-of-concept study) to <0.3%, with the small amount of remnant defects being mainly associated with oxide inclusions. The subsequent solution and aging treatments are also found to yield virtually identical phase distribution and hardness values in samples with vastly varying as-built defect contents. This can have considerable implications in contributing to minimizing elaborate process optimization efforts as well as slightly enhancing production speeds to promote industrialization of EBM for applications that demand the above post-treatments.

  • Sreekanth, Suhas
    et al.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Hurtig, Kjell
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Joshi, Shrikant V.
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för avverkande och additativa tillverkningsprocesser (AAT).
    Andersson, Joel
    Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för svetsteknologi (SV).
    Ghassemali, Ehsan
    Jönköping University.
    Effect of Direct Energy Deposition Process Parameters on Single-Track Deposits of Alloy 7182020Inngår i: Metals, E-ISSN 2075-4701, Vol. 10, nr 1, s. 01-16, artikkel-id 96Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effect of three important process parameters, namely laser power, scanning speed and laser stand-off distance on the deposit geometry, microstructure and segregation characteristics in direct energy deposited alloy 718 specimens has been studied. Laser power and laser stand-off distance were found to notably affect the width and depth of the deposit, while the scanning speed influenced the deposit height. An increase in specific energy conditions (between 0.5 J/mm2 and 1.0 J/mm2) increased the total area of deposit yielding varied grain morphologies and precipitation behaviors which were comprehensively analyzed. A deposit comprising three distinct zones, namely the top, middle and bottom regions, categorized based on the distinct microstructural features formed on account of variation in local solidification conditions. Nb-rich eutectics preferentially segregated in the top region of the deposit (5.4–9.6% area fraction, Af) which predominantly consisted of an equiaxed grain structure, as compared to the middle (1.5–5.7% Af) and the bottom regions (2.6–4.5% Af), where columnar dendritic morphology was observed. High scan speed was more effective in reducing the area fraction of Nb-rich phases in the top and middle regions of the deposit. The <100> crystallographic direction was observed to be the preferred growth direction of columnar grains while equiaxed grains had a random orientation.

  • Sund, Joakim
    Högskolan Väst, Institutionen för individ och samhälle, Avd för utbildningsvetenskap och språk.
    Words and Meaning in Gaming: 'World of Warcraft' and 'Counterstrike Global Offensive'2020Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [en]

    Online gaming is a relatively modern phenomenon that is not older than 20 years. Most online players speak English in some form, either by talking or writing. The two games, 'World of Warcraft' and 'Counterstrike' have taken over the gaming-world and the gamers' language has found its way right into the dictionary.

    The aim of the study was to examine how meanings of language change or evolve in the context of online video game playing.

    In this study, two gameplay videos were transcribed and analysed both qualitatively and quantitatively. Gaming words were identified through calculating word frequency in terms of types and tokens, and these identified words were then analysed qualitatively.

    The result contains three categories: Contextual Meaning, New Meaning, and New Words. The concepts of Contextual, New meaning and New Words were compared to dictionary meanings to see whether new meanings were created in the context of the gaming world. Based on the result, the study suggests that game language can influence the overall usage of language in the future.

  • Johansson, Anna
    Högskolan Väst, Institutionen för individ och samhälle, Avdelningen för socialt arbete och socialpedagogik.
    Summering av sex års samverkansforskning för främjande av barns och ungas välfärd: Teman och utmaningar2019Rapport (Annet vitenskapelig)
  • Henry, Alastair
    et al.
    Högskolan Väst, Institutionen för individ och samhälle, Avd för utbildningsvetenskap och språk.
    Thorsen, Cecilia
    Högskolan Väst, Institutionen för individ och samhälle, Avd för utbildningsvetenskap och språk.
    Engagement with Technology: Gaming, Immersion and Sub-Optimal Experiences2019Inngår i: Technology in Language Teaching & Learning, ISSN 2652-1687, Vol. 1, nr 2, s. 52-67Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This conceptual article focuses on student engagement, and the use of digital games in language classrooms. In making a contribution to the mapping of student engagement across SLA (Dörnyei, 2019a), and in line with the need to use established theories to develop insights into engagement when L2 learning involves digital games, a case is made for the concept of immersion (Brown & Cairns, 2004). The concept is first introduced. Then, to explain how immersion can contribute in understanding student engagement with digital games, an example of engaged gameplay from a classroom ethnographic project in Sweden is provided. Drawing on this example, immersion is contrasted with the more established concepts of L2 willingness to communicate and flow. These comparisons show how immersion captures a form of engaged behaviour particular to playing video games, and which is distinct from other types of focused behaviour previously identified in L2 learning contexts. It is suggested that immersion can make a significant contribution to understanding engagement in contemporary classrooms: it captures engaged behaviour of varying intensity, validated measurement instruments exist, and it can be used in multi-variable designs. Although immersion captures engagement particular to gaming experiences, it has potential to extend to other digital technologies.

  • Johansson, Kristina
    Högskolan Väst, Institutionen för individ och samhälle, Avdelningen för psykologi, pedagogik och sociologi.
    VILÄR 5-6 december 2019, University West, Trollhättan: Abstracts2019Konferanseproceedings (Annet vitenskapelig)