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  • Akram, Yasser
    et al.
    University West, Department of Engineering Science, Division of Industrial Engineering and Management, Electrical- and Mechanical Engineering.
    Mirzad, Elias
    University West, Department of Engineering Science, Division of Industrial Engineering and Management, Electrical- and Mechanical Engineering.
    Studie av övertoners inverkan på relätripptiden hos ett elektromekaniskt överströmsrelä2019Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A problem that has been noticed in the electricity grid is the increase in level of harmonics. In some cases, there may also be currents or voltages with frequencies that differ from the fundamental tone and this leads to the grid having harmonics meaning that when loads and components in the electricity grid are not sinusoidal, harmonics occur. For example, an increase in these types of loads e.g. charging an electric car or computers, in the electricity grid gives rise to an increasing harmonic content.

    In view of the aforementioned, this thesis has been carried out in collaboration with the Megger Sweden AB, Stockholm, as the official client for this study. The purpose here is to study the effect of harmonics on the relay trip time of an electromechanical overcurrent relay that is installed in the power grid's control facilities.

    The tests are performed with the test instrument Sverker 900 and an electromechanical overcurrent relay, ASEA RI. For testing the RI relay, a Swedish standard, an upcoming international standard as well as instructions from the client have been thoroughly followed and applied. The results of the tests shows the difference between the trip time with harmonics and the trip time for the fundamental tone.

    Conclusions based on the results are partly that the overcurrent relay is slower at weak currents, that is 2.8A and 3A respectively, as well as for long trip times in relation to the behavior without harmonics. According to the findings conducted herein, there is no significant correlation between the presence of harmonics and the influence of the relay trip time on medium and strong currents, between 4A-8A, or on shorter trip times.

    By reason of the time constraint experienced in conducting this study, the results and findings reached leaves a sound potential and promise for future tests conducted at different harmonic levels. A future recommendation for similar studies will be to test only at low currents, long trip times and slow disk speeds as this would facilitate the possibility of fulfilling a more robust result analysis.

  • Yehorov, Yuri
    et al.
    Center for Research and Development of Welding Processes, Federal University of Uberlandia, Uberlândia, Brazil.
    da Silva, Leandro João
    Center for Research and Development of Welding Processes, Federal University of Uberlandia, Uberlândia, Brazil.
    Scotti, Americo
    University West, Department of Engineering Science, Division of Welding Technology. Center for Research and Development of Welding Processes, Federal University of Uberlandia, Uberlândia, Brazil.
    Balancing WAAM Production Costs and Wall Surface Quality through Parameter Selection: A Case Study of an Al-Mg5 Alloy Multilayer-Non-Oscillated Single Pass Wall2019In: Journal of Manufacturing and Materials Processing, E-ISSN 2504-4494, Vol. 3, no 2, p. 1-19Article in journal (Refereed)
    Abstract [en]

    The purpose of the study was to propose a strategy to assess the potential reduction of the production cost during wire+arc additive manufacturing (WAAM) based on the combination of wire feed speed (related to deposition rate) and travel speed (related to deposition time). A series of experiments, using a multilayer-non-oscillated single pass wall made of an Al-Mg alloy, was conducted. The quality of the wall was assessed through the lateral surface waviness and top layer undulation. The concepts of Surface Waviness and Buy-to-Apply indices were introduced. Initially, the range of travel speed (TS) that provided layers with acceptable quality was determined for a given wire feed speed (WFS), corresponding to a constant current. Then, the effect of the increase of production capacity of the process (though current raising, yet maintaining the ratio WFS/TS constant) on the wall quality for a given condition within the TS range was assessed. The results showed that the useful range of TS prevents too rough a waving surface below the lower limit and top surface undulation over the higher limit. However, inside the range, there is little quality variation for the case under study. Finally, simulations of deposition time were developed to demonstrate the weight of the TS on the final deposition time and wall quality as a function of a target wall width. This respective weight showed the existence of a complex and unpredictable, yet determined, power of a combination of TS, target wall geometry, and dead time between subsequent layers. It was verified to be possible to find optimized TS as a function of different target geometries. 

  • Frödin, Rolf
    University West, Department of Social and Behavioural Studies, Division of Psychology, Pedagogy and Sociology.
    Arbetet som ordningsvakt: Att möta motstridiga krav2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The study has its starting point in two articles in the daily press, one debate article and one reply, about the security guards work at the pub. The debaters in the article said that the insecurity in the nightlife depends on the security guards abusing their power discriminating and committing violence against the guests at the pub. A security guard replicated on the article and said that the insecurity in the pub is not created by the security guards but by the pub owner with his staff. There is a conflict of interest between the security guard's assignment and the pub owner who pays the guard's salary. The owner of the pub would like to have influence over the work of the security guards, otherwise he /she may lose his /her work. In the reply, it is proposed that the solution to the conflict of interest is that the security guards become employees and receive a salary from the police authority. The contents of the security guard's reply to the debate article caught my interest in this study.

    The aim of the study is to gain increased knowledge and understanding of how the conditions are for the work of the security guards, in a pub environment, based on three issues. 

    • How do the guards experience their profession and mission?

    • How do the security guards handle the conflict of interest between the principal police authority and the owner of the pub?

    • How do the security guards reason to be state employees and receive salaries from the police authority? 

    The theoretical perspective of the study consists of Rational Choice theory (RC), Georg Simmel's theory of triads and Pierre Bourdieu's concept of habitus. To answer the questions, qualitative method was chosen with interview. Five security guards were interviewed through semi-structured interview method. The interviews were printed and analyzed by thematic analysis. The themes that appear in the study are the professional role of the security guards, conflict of interest, form of employment and improvement area.

    The study's results show that the security guards watch their professional role as an important service function at the pub where good reception of the guests is in focus. The described conflict of interest was known by the interviewed guards, but they judged that it was caused by security guards who were unsuitable and who did not stand up for their profession and assignments. All security guards did not want to be employed and receive salaries from the police authority, but argued that security guards would only be employed by security companies and not directly by the owner of the pub.

  • Bengtsson, Daniel
    et al.
    University West, Department of Engineering Science, Division of Industrial Engineering and Management, Electrical- and Mechanical Engineering.
    Gustafsson, Karin
    University West, Department of Engineering Science, Division of Industrial Engineering and Management, Electrical- and Mechanical Engineering.
    Kvalitetsarbete inom mätteknik med FARO-arm2019Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The thesis has been performed at Siemens Industrial Turbomachinery AB in Trollhättan. The company manufactures combustors for gas turbines. The purpose of the work has been to investigate whether qualified measurements can be performed with Siemens Industrial Turbomachinery AB's measuring instruments. This study has been performed through a measurement system analysis. The purpose has also been to investigate whether it is possible to introduce statistical process control for a detail.

    To carry out this study, the study designs case study and action research have been used. The case study has been for the measurement system analysis because it concerned a specific case that has been analyzed. Action research has been used to investigate statistical process management since the survey has been part of planning work for the introduction of an improvement. Measurements on a gauge block with known dimensions have also been made. The measurements were compiled in an Excel sheet and analyzed in Minitab. Then a VMEA was performed.

    Analysis of the measurements made it clear that the operators vary in both repeatability and reproducibility. The measuring instrument has proved to be stable and not a basis for variation. The study on implementation of statistical process control has shown that it is not possible to be introduced because the measurement results are too unstable. This leads to the company having to review its measurement methods to achieve a reduced spread of the measurement results. That the study has not used enough measuring objects for a statistically correct result should be emphasized. Consideration should therefore be taken that the result of the study is not entirely reliable, but rather indicate that it is a probable result that has emerged. Suggestions that have emerged during the study is:

    • The details are placed indoors long enough before they are measured.

    • The company introduces a separate, customized room for measuring the details.

    • The company reviews the work methodology for the measurements.

    • The company updates work instructions for measurements.

    • The company introduces measurement training for operators.

    What has not been made is the actual introduction and making of user data for statistical process control. This is because the measurement results have a too great variation for the use of SPS.

  • Viking, Tuija
    University West, Department of Health Sciences, Section for health promotion and care sciences.
    En studie om interprofessionellt lärande i teamarbete: Fallet med en 'best practice´ för tvångsvård2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [sv]

    Det interprofessionella lärandet, IPL, i team har blivit ett populärt medel för att öka samarbete och kvalité i den sociala sektorn och hälso- och sjukvård. En alltmer specialiserad och fragmentiserad vård, som ofta genomförs i team, har lett till stor spridning av interprofessionell utbildning, IPE. Studerande och/eller medlemmar från olika professioner lär sig därmed, med, från och om varandra. Sådant lärande antas ske vid utbyte av och reflektion över varandras olika erfarenheter, perspektiv och kunskaper, d.v.s. professionella skillnader, och leda till förbättrad effektivitet och kvalitet i vården.

    Inom hälso- och sjukvårdsområdet har man dock bara i mindre skala undersökt vad IPL i etablerade team innebär och hur professionella skillnader påverkar lärandet. Denna licentiatuppsats hade som övergripande syfte att bidra med ökad kunskap inom detta område. Här studerades ett arbete, med kliniska riktlinjer för psykiatrisk tvångsvård, som skulle genomföras av ett interprofessionellt team. Huvudfrågan var hur teamet arbetade med riktlinjerna och hur professionella skillnader kom till uttryck och gav implikationer för IPL. Licentiatuppsatsen är en fallstudie. Undersökningen baseras dels på material (mötesprotokoll, mejlkommunikation, dokument och mediarapporter) från teamets tre-åriga arbete, dels nio intervjuer och en observation av seminariet där teammedlemmar presenterade de färdiga riktlinjerna. Studie 1 syftade till att undersöka hur teamet hanterade en kontrovers och hur de strategier som användes gav konsekvenser för interprofessionellt lärande. Studie 2 syftade till att studera hur teamet granskade kön/genus i arbetet med riktlinjerna och vilka implikationer det blev för riktlinjerna och för interprofessionellt lärande. Fokus här är därmed på ett lärande i ett "färdigt" team. Resultaten i studierna baseras på fallbeskrivning och narrativ analys. Fynden i studierna tolkades huvudsakligen utifrån sociokulturell teori och idéer och insikter från kontroversstudier (studie 1) och det genusvetenskapliga fältet (studie 2).

    Resultatet i studie 1 visade att kontroversen hanterades främst genom en kompromiss. Resultatet visar också hur lärandestrategier nyttjades vid användning av texter. Lärandet utmanades dock när maktstrategier användes genom hävdande av auktoritet snarare än utforskande av kunskapsläget.

    Resultatet i studie 2 visade hur kön/genus aktualiserades i en diskussion om könsskillnader i användning av tvångsbälten. I diskussionen användes professionsspecifika erfarenheter och kunskaper om kön/genus, vilket kan antas främjade IPL. Teamets lärande om komplexiteten kring kön/genus resulterade i riktlinjer som betonar makt och med fokus på den individuella patienten. Därmed ledde teamets analys och lärande relaterat till kön/genus paradoxalt till könsneutrala riktlinjer. Slutsatsen är att studierna, på olika sätt, visade förekomst av IPL och hur detta påverkades både positivt och negativt av professionella skillnader.

  • Public defence: 2019-04-23 10:00 F131, Trollhättan
    Rehan, Arbab
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Effect of heat treatment on microstructure and mechanical properties of a 5 wt.% Cr cold work tool steel2019Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This work presents investigations related to phase transformations occurring inthe 5 wt.% Cr cold work tool steel Caldie during hardening and tempering treatments. The influence of austenitisation temperature, cooling rate, sub-zero cooling, isothermal treatment during cooling, tempering temperature and holding time on the microstructure and mechanical properties were investigated.The hardened microstructure of the investigated steel consisted of a mixture ofplate and lath martensite, minor amounts of bainite, blocky and thin retained austenite and M7C3 carbides. Increasing austenitisation temperature from 1020°Cto 1050°C was found useful as it provided higher hardness, good compressive strength and sufficient toughness. However, a further increase to 1075°C resulted in large prior austenite grains which produced coarse martensite containing somewhat increased carbon content. This was found to reduce the impacttoughness of the steel. Significant amounts of retained austenite were present after tempering for 2x2 h between 200°C and 500°C while tempering at 525°C or higher, reduced retained austenite content to below 2%. During holding at tempering temperature carbides precipitated in martensite and possibly in retained austenite. The retained austenite was thereby destabilised and transformed to martensite on cooling. This fresh martensite was tempered by following tempering treatments. It was concluded that tempering at 525°C for 2x2 h was suitable to achieve a good combination of hardness, compressive strength and impact toughness. Retained austenite was also found to transform during holding at 600°C for longer times. Initially, carbides formed in the austenite and after some time transformation of retained austenite to ferrite and carbides took place. Results were used to discuss alternative heat treatment procedures for the 5wt.% Cr cold work tool steel Caldie and some changes of current heat treatment recommendations were suggested.

  • Public defence: 2019-04-24 10:00 F131, Trollhättan
    Fahlström, Karl
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Laser welding of ultra-high strength steel and a cast magnesium alloy for light-weight design2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    There is a strong industrial need for developing robust and flexible manufacturing methods for future light-weight design. Better performing, environmental friendly vehicles will gain competitive strength from using light weight structures. In this study, focus has been on laser welding induced distortions for ultra-high strength steel (UHSS) where trials were performed on single hat and double hat beams simulating A-pillar and B-pillar structures. Furthermore, also laser welding induced porosity in cast magnesium alloy AM50 for interior parts were studied. For UHSS, conventional laser welding was done in a fixture designed for research. For cast magnesium, single-spot and twin-spot welding were done. Measurements of final distortions and metallographic investigations have been performed. The results show that the total weld metal volume or the total energy input were good measures for predicting the distortions within one steel grade. For comparing different steel grades, the width of the hard zone should be used. The relation between the width of the hard zone, corresponding to the martensitic area of the weld, and the distortions is almost linear. Additionally, compared with continuous welds, stitching reduced the distortions. For cast magnesium, two-pass (repeated parameters) welding with single-spot gave the lowest porosity of approximately 3%. However, two-pass welding is not considered production friendly. Twin-spot welding was done, where the first beam provided time for nucleation and some growth of pores while reheating by the second beam should provide time for pores to grow and escape. This gave a porosity of around 5%. Distortions and porosity are the main quality problems that occur while laser welding UHSS and cast magnesium, respectively. Low energy input seems to generally minimize quality issues. Laser welding shows high potential regarding weld quality and other general aspects such as productivity in light-weight design for both high strength steel and cast magnesium.