Change search
Refine search result
1234 51 - 100 of 157
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 51.
    Frodelius, Jenny
    et al.
    Linköping University, Thin Film Physics Division, Department of Physics.
    Sonestedt, Marie
    Chalmers University of Technology, Microscopy and Microanalysis, Department of Applied Physics.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Palmquist, Jens-Petter
    Kanthal AB, 734 27 Hallstahammar, Sweden.
    Stiller, Krystyna
    Chalmers University of Technology, Microscopy and Microanalysis, Department of Applied Physics.
    Högberg, Hans
    Linköping University, Thin Film Physics Division, Department of Physics.
    Hultman, Lars
    Linköping University, Thin Film Physics Division, Department of Physics.
    Ti2AlC coatings deposited by High Velocity Oxy-Fuel spraying2008In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 202, no 24, p. 5976-5981Article in journal (Refereed)
    Abstract [en]

    High Velocity Oxy-Fuel has been utilized to spray coatings from Ti2AlC (MAXTHAL 211®) powders. X-ray diffraction showed that the coatings consist predominantly of Ti2AlC with inclusions of the phases Ti3AlC2, TiC, and Al–Ti alloys. The fraction of Ti2AlC in coatings sprayed with a powder size of 38 μm was found to increase with decreasing power of the spraying flame as controlled by the total gas flow of H2 and O2. A more coarse powder (56 μm) is less sensitive to the total gas flow and retains higher volume fraction of MAX-phase in the coatings, however, at the expense of increasing porosity. X-ray pole figure measurements showed a preferred crystal orientation in the coatings with the Ti2AlC (000l) planes aligned to the substrate surface. Bending tests show a good adhesion to stainless steel substrates and indentation yields a hardness of 3–5 GPa for the coatings sprayed with a powder size of 38 μm.

  • 52.
    Ganvir, Ashish
    University West, Department of Engineering Science, Division of Manufacturing Processes. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Comparative analysis of Thermal Barrier Coatings produced using Suspension and Solution Precursor Feedstock2014Independent thesis Advanced level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The research work performed in this thesis has been carried out at the Production Tech-nology Centre where the Thermal Spray research group of University West has its work-shop and labs.

    This research work has been performed in collaboration with the International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), Hyderabad, India.

    First of all, I would like to express my sincere thanks and gratitude to my supervisors Dr. Nicolaie Markocsan and Dr. Nicholas Curry for their guidance, great support and valuable suggestions without which this work could not have been possible. I would also like to thanks Prof. Per Nylén for keeping faith in me and providing me an opportunity to work at PTC, which is a great place to perform research. It is my pleasure being their student and I wish I would keep learning from all of them, both on academic and personal grounds. I would also like to thank my colleagues at PTC Mr. Mohit Gupta and Mr. Stefan Björklund, for their help and support during this work.

    I would like to acknowledge the H.C. Starck Company for its financial support for the pro-ject; Dr. Filofteia-Laura TOMA at Fraunhofer IWS, Dresden to help us in spraying suspen-sion sprayed YSZ top coats, G Shivkumar from ARCI to help us in spraying solution pre-cursor sprayed top coats and Toni Bogdanoff, Jönköping University to help us in conduct-ing the LFA experiment

    Download full text (pdf)
    fulltext
  • 53.
    Ganvir, Ashish
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Microstructure and Thermal Conductivity of Liquid Feedstock Plasma Sprayed Thermal Barrier Coatings2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Thermal barrier coating (TBC) systems are widely used on gas turbine components to provide thermal insulation and oxidation protection. TBCs, incombination with advanced cooling, can enable the gas turbine to operate at significantly higher temperatures even above the melting temperature of the metallic materials. There is a permanent need mainly of environmental reasons to increase the combustion turbine temperature, hence new TBC solutions are needed.By using a liquid feedstock in thermal spraying, new types of TBCs can be produced. Suspension plasma/flame or solution precursor plasma spraying are examples of techniques that can be utilized for liquid feedstock thermal spraying.This approach of using suspension and solution feedstock, which is an alternative to the conventional solid powder feed stock spraying, is gaining increasing research interest, since it has been shown to be capable of producing coatings with superior coating performance.The objective of this research work was to explore relationships between process parameters, coating microstructure, thermal diffusivity and thermal conductivity in liquid feedstock thermal sprayed TBCs. A further aim was to utilize this knowledge to produce a TBC with lower thermal diffusivity and lower thermal conductivity compared to state-of-the-art in industry today, i.e. solid feed stock plasma spraying. Different spraying techniques, suspension high velocity oxy fuel,solution precursor plasma and suspension plasma spraying (with axial and radialfeeding) were explored and compared with solid feedstock plasma spraying.A variety of microstructures, such as highly porous, vertically cracked and columnar, were obtained. It was shown that there are strong relationships between the microstructures and the thermal properties of the coatings.Specifically axial suspension plasma spraying was shown as a very promising technique to produce various microstructures as well as low thermal diffusivity and low thermal conductivity coatings.

    Download full text (pdf)
    fulltext
  • 54.
    Ganvir, Ashish
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Characterization of Microstructure and Thermal Properties of YSZ Coatings Obtained by Axial Suspension Plasma Spraying (ASPS)2015In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 24, no 7, p. 1195-1204Article in journal (Refereed)
    Abstract [en]

    The paper aims at demonstrating various microstructures which can be obtained using the suspension spraying technique and their respective significance in enhancing the thermal insulation property of a thermal barrier coating. Three different types of coating microstructures are discussed which were produced by the Axial Suspension Plasma Spraying. Detailed characterization of coatings was then performed. Optical and scanning electron microscopy were utilized for microstructure evaluations; x-ray diffraction for phase analysis; water impregnation, image analysis, and mercury intrusion porosimetry for porosity analysis, and laser flash analysis for thermal diffusivity measurements were used. The results showed that Axial Suspension Plasma Spraying can generate vertically cracked, porous, and feathery columnar-type microstructures. Pore size distribution was found in micron, submicron, and nanometer range. Higher overall porosity, the lower density of vertical cracks or inter-column spacing, and higher inter-pass porosity favored thermal insulation property of the coating. Significant increase in thermal diffusivity and conductivity was found at higher temperature, which is believed to be due to the pore rearrangement (sintering and pore coarsening). Thermal conductivity values for these coatings were also compared with electron beam physical vapor deposition (EBPVD) thermal barrier coatings from the literature and found to be much lower. © 2015 ASM International

  • 55.
    Ganvir, Ashish
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Govindarajan, Sivakumar
    International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), 500005 Hyderabad, India.
    Characterization of Thermal Barrier Coatings Produced by Various Thermal Spray Techniques Using Solid Powder, Suspension, and Solution Precursor Feedstock Material2016In: International Journal of Applied CeramicTechnology, ISSN 1546-542X, Vol. 13, no 2, p. 324-332Article in journal (Refereed)
    Abstract [en]

    Use of a liquid feedstock in thermal spraying (an alternative to the conventional solid powder feedstock) is receiving an increasing level of interest due to its capability to produce the advanced submicrometer/nanostructured coatings. Suspension plasma spraying (SPS) and solution precursor plasma spraying (SPPS) are those advanced thermal spraying techniques which help to feed this liquid feedstock. These techniques have shown to produce better performance thermal barrier coatings (TBCs) than conventional thermal spraying. In this work, a comparative study was performed between SPS- and SPPS-sprayed TBCs which then were also compared with the conventional atmospheric plasma-sprayed (APS) TBCs. Experimental characterization included SEM, porosity analysis using weight difference by water infiltration, thermal conductivity measurements using laser flash analysis, and lifetime assessment using thermo-cyclic fatigue test. It was concluded that SPS coatings can produce a microstructure with columnar type features (intermediary between the columnar and vertically cracked microstructure), whereas SPPS can produce vertically cracked microstructure. It was also shown that SPS coatings with particle size in suspension (D50) <3 μm were highly porous with lower thermal conductivity than SPPS and APS coatings. Furthermore, SPS coatings have also shown a relatively better thermal cyclic fatigue lifetime than SPPS.

  • 56.
    Ganvir, Ashish
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Joshi, Shrikant
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Vilemova, Monika
    IPP.
    Pala, Zdenek
    IPP.
    Influence of Microstructure on Thermal Properties of Axial Suspension Plasma-Sprayed YSZ Thermal Barrier Coatings2016In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 25, no 1-2, p. 202-212Article in journal (Refereed)
    Abstract [en]

    Suspension plasma spraying is a relatively new thermal spaying technique to produce advanced thermal barrier coatings (TBCs) and enables production of coatings with a variety of structures—highly dense, highly porous, segmented, or columnar. This work investigates suspension plasma-sprayed TBCs produced using axial injection with different process parameters. The influence of coating microstructure on thermal properties was of specific interest. Tests carried out included microstructural analysis, phase analysis, determination of porosity, and pore size distribution, as well as thermal diffusivity/conductivity measurements. Results showed that axial suspension plasma spraying process makes it possible to produce various columnar-type coatings under different processing conditions. Significant influence of microstructural features on thermal properties of the coatings was noted. In particular, the process parameter-dependent microstructural attributes, such as porosity, column density, and crystallite size, were shown to govern the thermal diffusivity and thermal conductivity of the coating.

  • 57.
    Ganvir, Ashish
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Research Environment Production Technology West.
    Toma, Filofteia-Laura
    Fraunhofer Institute for Material and Beam Technology, Dresden, Germany.
    Comparative study of suspension plasma sprayed and suspension high velocity oxy-fuel sprayed YSZ thermal barrier coatings2015In: Surface and Coatings Technology, ISSN 0257-8972, Vol. 268, p. 70-76Article in journal (Refereed)
    Abstract [en]

    Suspension Thermal Spraying is a relatively new thermal spaying technique to produce advanced thermal barrier coatings. This technique enables the production of much different performance thermal barrier coatings than conventional thermal spraying which uses solid powder as a feedstock material. In this work a comparative study is performed on four different types of thermal barrier coatings sprayed with two different thermal spay processes, suspension high velocity oxy-fuel spraying (SHVOF) and suspension plasma spraying (SPS) using two different water-based suspensions. Tests carried out include microstructural analysis with SEM, porosity analysis using weight difference by water infiltration, thermal conductivity measurements using laser flash analysis and lifetime assessment using thermo-cyclic fatigue tests. The results showed that SPS coatings were much porous and hence showed lower thermal conductivity than SHVOF coatings produced with the same suspension. From the thermo-cycling tests it was observed that the SPS coatings showed a higher lifetime than the SHVOF ones.

  • 58.
    Ganvir, Ashish
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Vilemova, Monika
    IPP Prague, Czech Republic.
    Pala, Zdenek
    IPP Prague, Czech Republic.
    Influence of Microstructure on Thermal Properties of Columnar Axial Suspension Plasma Sprayed Thermal Barrier Coatings2015In: Proceedings of the International Thermal Spray Conference: International Thermal Spray Conference and Exposition, ITSC 2015; Long Beach; United States; 11 May 2015 through 14 May 2015 / [ed] A. McDonald, A. Agarwal, G. Bolelli, A. Concustell, Y.-C. Lau, F.-L. Toma, E. Turunen, C. Widener, ASM International, 2015, p. 498-505Conference paper (Refereed)
    Abstract [en]

    Suspension Plasma Spraying is a relatively new thermal spraying technique to produce advanced thermal barrier coatings. This technique enables the production of a variety of structures from highly dense, highly porous, segmented or columnar coatings. In this work a comparative study is performed on six different suspension plasma sprayed thermal barrier coatings which were produced using axial injection and different process parameters. The influence of coating morphology and porosity on thermal properties was of specific interest. Tests carried out include microstructural analysis with SEM, phase analysis using XRD, porosity calculation using Archimedes experimental setup, pore distribution analysis using mercury infiltration technique and thermal diffusivity/conductivity measurements using laser flash analysis. The results showed that columnar and cauliflower type coatings were produced by axial suspension plasma spraying process. Better performance coatings were produced with relatively higher overall energy input given during spraying. Coatings with higher energy input, lower thickness and wider range of submicron and nanometer sized pores distribution showed lower thermal diffusivity and hence lower thermal conductivity. Also, in-situ heat treatment did not show dramatic increase in thermal properties.

  • 59.
    Glorieux, Emile
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    Svensson, Bo
    University West, Department of Engineering Science, Division of Automation Systems.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Manufacturing Processes. University West, Department of Engineering Science, Division of Production Systems. Chalmers.
    Optimised Control of Sheet Metal Press Lines2014In: Proceedings of the 6th International Swedish Production Symposium 2014 / [ed] Stahre, Johan, Johansson, Björn & Björkman, Mats, 2014, p. 1-9Conference paper (Refereed)
    Abstract [en]

    Determining the control parameters for sheet metal press lines is a large scale and complex optimisation problem. These control parameters determine velocities, time constants, and cam values of critical interactions between the equipment. The complexity of this problem is due to the nonlinearities and high dimensionality. Classical optimisation techniques often underperform in solving this kind of problems within a practical timeframe. Therefore, specialised techniques need to be developed for these problems. An existing approach is simulation-based optimisation, which is to use a simulation model to evaluate the trial solutions during the optimisation. In this paper, an efficient simulation-based optimisation algorithm for large scale and complex problems is proposed. The proposed algorithm extends the cooperative coevolutionary algorithm, which optimises subproblems separately. Hence, the optimisation problem must be decomposed into subproblems that can be evaluated separately. To optimise the subproblems, the proposed algorithm allows using embedded deterministic algorithms, next to stochastic genetic algorithms, getting the flexibility of using either type. It also includes a constructive heuristic that creates good initial feasible solutions to expedite the optimisation. The extension enables solving complex, computationally expensive problems efficiently. The proposed algorithm has been applied on an automated sheet metal press line from the automotive industry. The objective is to find control parameters that maximise the line’s production rate. The results show that the proposed algorithm manages to find optimal control parameters efficiently within the practical timeframe. This is a step forward in press line optimisation since to the authors’ knowledge this is the first time a press line has been optimised efficiently in this way.

  • 60.
    Gokavarapu, Naga Sai Pavan Rahul
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Termisk cyklisk utmattning studie av Gd2Zr2O7 / YSZ flerskikts termiska barriärbeläggningar2015Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    From many years YSZ is used as the top coat material for TBC's, as it has good phase stability up to 1200°C, higher fracture toughness, lower thermal conductivity, erosion resistance & higher coefficient of thermal expansion. But, it has a drawbacks at high temperature such as sintering and transformation of phases. For this reason new ceramic materials with pyrochlores crystal structure such as Gd2Zr2O7 are being considered as it has high melting points, phase stability, lower thermal conductivity and CMAS resistance. But it has low fracture toughness when compared to YSZ. In order to take advantage of low thermal conductivity and high thermal stability of gadolinium zirconate and avoiding the drawbacks of low coefficient of thermal expansion and low toughness using YSZ, a double/multi-layer coatings approach is being used. Therefore, multi-layer TBCs are sprayed and compared with single layer coating in this work. These coatings are processed by suspension plasma spraying. For single layer coating YSZ is used, for double layer coating YSZ as the intermediate coating and Gd2Zr2O7 as the top coat is used. Additionally, a triple layer coating system comprising YSZ, Gd2Zr2O7 and dense Gd2Zr2O7 as top coat is also sprayed. The as sprayed coatings are characterized for microstructure analysis using optical microscope and scanning electron microscope (SEM), elemental analysis of TGO using Energy-Dispersive Spectrometer (EDS). XRD analysis was done to identify various phases in the coating. Porosity analysis using Archimedes principle was carried out. Thermal cyclic fatigue (TCF) test of the sprayed coatings was carried out at 1100°C. Failure analysis of the TCF specimens was carried out using SEM/EDS. TCF results showed that the triple layer coatings (dense Gd2Zr2O7/Gd2Zr2O7/YSZ) had higher thermal cyclic fatigue life and lower TGO thickness when compared to single layer (YSZ) and double layer (Gd2Zr2O7/YSZ) TBCs.

    Download full text (pdf)
    fulltext
  • 61.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Vaßen, Robert
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Design of Next Generation Thermal Barrier Coatings- Experiments and Modelling2013In: Surface and Coatings Technology, ISSN 0257-8972, Vol. 220, p. 20-26Article in journal (Refereed)
    Abstract [en]

    Thermal barrier coating (TBC) systems have been used in the gas turbine industry since the 1980's. The future needs of both the air and land based turbine industry involve higher operating temperatures with longer lifetime on the component so as to increase power and efficiency of gas turbines. The aim of this study was to meet these future needs by further development of zirconia coatings. The intention was to design a coating system which could be implemented in industry within the next three years. Different morphologies of ceramic topcoat were evaluated; using dual layer systems and polymers to generate porosity. Dysprosia stabilised zirconia was also included in this study as a topcoat material along with the state-of-the-art yttria stabilised zirconia (YSZ). High purity powders were selected in this work. Microstructure was assessed with scanning electron microscope and an in-house developed image analysis routine was used to characterise porosity content. Evaluations were carried out using the laser flash technique to measure thermal conductivity. Lifetime was assessed using thermo-cyclic fatigue testing. Finite element analysis was utilised to evaluate thermal-mechanical material behaviour and to design the morphology of the coating with the help of an artificial coating morphology generator through establishment of relationships between microstructure, thermal conductivity and stiffness. It was shown that the combined empirical and numerical approach is an effective tool for developing high performance coatings. The results show that large globular pores and connected cracks inherited within the coating microstructure result in a coating with best performance. A low thermal conductivity coating with twice the lifetime compared to the industrial standard today was fabricated in this work.

  • 62.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Dwivedi, Gopal
    Stony Brook University, USA.
    Nylén, Per
    University West, Department of Engineering Science, Research Environment Production Technology West.
    Vackel, Andrew
    Stony Brook University, USA.
    Sampath, Sanjay
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    An Experimental Study of Microstructure: Property Relationships in Thermal Barrier Coatings2013In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 22, no 5, p. 659-670Article in journal (Refereed)
    Abstract [en]

    The thermal-mechanical properties of thermal barrier coatings are highly influenced by the defects present in coating microstructure. The aim of this study was to meet the future needs of the gas turbine industry by further development of zirconia coatings through the assessment of microstructure-property relationships. A design of experiments was conducted for this purpose with current, spray distance, and powder feed rate as the varied parameters. Microstructure was assessed with SEM and image analysis was used to characterize porosity content. Evaluations were carried out using laser flash technique to measure thermal properties. A bi-layer beam curvature technique in conjunction with controlled thermal cycling was used to assess the mechanical properties, in particular their nonlinear elastic response. Coating lifetime was evaluated by thermo-cyclic fatigue testing. Relationships between microstructure and coating properties are discussed. Dense vertically cracked microstructure and highly porous microstructure with large globular pores were also fabricated. Correlations between parameters obtained from nonlinear measurements and lifetime based on a priori established microstructural analysis were attempted in an effort to develop and identify a simplified strategy to assess coating durability following sustained long-term exposure to high temperature thermal cycling.

  • 63.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    A modelling approach to design of microstructures in thermal barrier coatings2013In: Journal of Ceramic Science and Technology, ISSN 2190-9385, Vol. 4, no 2, p. 85-92Article in journal (Refereed)
    Abstract [en]

    Thermo-mechanical properties of TBCs are strongly influenced by coating defects, such as delaminations and pores, thus making it essential to have a fundamental understanding of microstructure-property relationships in TBCs to produce a desired coating. Object-Oriented Finite element analysis (OOF) has been shown previously as an effective tool for evaluating thermal and mechanical material behaviour, as this method is capable of incorporating the inherent material microstructure as an input to the model. In this work, OOF was used to predict the thermal conductivity and effective Young's modulus of TBC topcoats. A Design of Experiments (DoE) was conducted by varying selected spray parameters for spraying Yttria Stabilized Zirconia (YSZ) topcoat. Microstructure was assessed with SEM and image analysis was used to characterize porosity content. The relationships between microstructural features and properties predicted by modelling are discussed. The microstructural features having the most beneficial effect on properties were sprayed with another spray gun so as to verify the results obtained from modelling. Characterisation of the coatings included microstructure evaluation, thermal conductivity and lifetime measurements. The modelling approach in combination with experiments undertaken in this study was shown to be an effective way in achieving coatings with optimised thermo-mechanical properties.

  • 64.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Weber, A.
    Karlsruhe Institute of Technology, Karlsruhe, Germany .
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Gindrat, M.
    Oerlikon Metco, Wohlen, Switzerland.
    Electrochemical performance of plasma sprayed metal supported planar solid oxide fuel cells2015In: ECS Transactions, ISSN 1938-5862, E-ISSN 1938-6737, Vol. 68, no 1, p. 1791-1802Article in journal (Refereed)
    Abstract [en]

    High production cost is one of the major barriers to widespread commercialization of solid oxide fuel cells (SOFCs). Thermal spray techniques are a low cost alternative for the production of SOFCs. The objective of this work was to evaluate the electrochemical performance of half-cells produced by plasma spraying. The anode was deposited on a porous metallic support by atmospheric plasma spraying (APS) whereas the electrolyte was deposited by plasma spray-thin film (PS-TF) technique which can produce thin and dense coatings at high deposition rates. The cathode was deposited by screen-printing. The electrochemical tests were performed at 650-800°C. Current-voltage characteristics and impedance spectra were measured and analyzed. The impact of electrolyte composition and layer thickness on the gas tightness of the electrolyte and the area specific resistance of the cell is discussed. The results show that the applied thermal spraying techniques are a potential alternative for producing SOFCs. © The Electrochemical Society.

  • 65.
    Gustavsson Christiernin, Linn
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Flexibla robotceller inom fordonsindustrin: Men hur ska informationsutbytet och interaktionen ske?2012In: Fordonskomponenten, ISSN 2000-7299, no 4, p. 26-28Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    En stor del av bilproduktionsprocessen är automatiserad. Ett fordons alla delar passerar flera olika stationer eller celler för att justeras och installeras, och robotar och människor har olika,vanligtvis separerade, uppgifter. Ett problem med denna typ av automatiserade produktion är den tid som det tar att vidta ändringar och frånvaron av medel hos den mänskliga operatören att kommunicera och interagera med roboten på ett flexibelt vis.

  • 66.
    Gustavsson Christiernin, Linn
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Augustsson, Svante
    University West, Department of Engineering Science, Division of Automation Systems.
    Christiernin, Stefan
    University West, Department of Social and Behavioural Studies. University West, Department of Technology, Mathematics and Computer Science, Division for Computer Science.
    Safety Critical Robot Programming and Testing for Operations in Industrial Co-production2014In: IEEE Conference Publications, IEEE, 2014, p. 29-32Conference paper (Refereed)
  • 67.
    Hagqvist, Petter
    et al.
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    Heralic, Almir
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Technology, Mathematics and Computer Science, Division for Electrical Engineering and Land Surveying.
    Lennartson, Bengt
    University West, Department of Engineering Science, Division of Manufacturing Processes. University West, Department of Engineering Science, Division of Production Systems. Chalmers.
    Resistance based iterative learning control of additive manufacturing with wire2015In: Mechatronics (Oxford), ISSN 0957-4158, E-ISSN 1873-4006, Vol. 31, p. 116-123Article in journal (Refereed)
    Abstract [en]

    This paper presents successful feed forward control of additive manufacturing of fully dense metallic components. The study is a refinement of former control solutions of the process, providing more robust and industrially acceptable measurement techniques. The system uses a solid state laser that melts metal wire, which in turn is deposited and solidified to build the desired solid feature on a substrate. The process is inherently subjected to disturbances that might hinder consecutive layers to be deposited appropriately. The control action is a modified wire feed rate depending on the surface of the deposited former layer, in this case measured as a resistance. The resistance of the wire stick-out and the weld pool has shown to give an accurate measure of the process stability, and a solution is proposed on how to measure it. By controlling the wire feed rate based on the resistance measure, the next layer surface can be made more even. A second order iterative learning control algorithm is used for determining the wire feed rate, and the solution is implemented and validated in an industrial setting for building a single bead wall in titanium alloy. A comparison is made between a controlled and an uncontrolled situation when a relevant disturbance is introduced throughout all layers. The controller proves to successfully mitigate these disturbances and maintain stable deposition while the uncontrolled deposition fails.

  • 68.
    Harati, Ebrahim
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Fatigue strength of welds in 800 MPa yield strength steels: Effects of weld toe geometry and residual stress2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Nowadays there is a strong demand for lighter vehicles in order to increase the pay load. Through this the specific fuel consumption is decreased, the amount of greenhouse gases is lowered and the transport economy improved. One possibility to optimize the weight is to make the components from high strength steels and join them by welding. Welding is the main joining method for fabrication of a large proportion of all engineering structures. Many components experience fatigue loading during all or part of their life time and welded connections are often the prime location of fatigue failure.Fatigue fracture in welded structures often initiates at the weld toe as aconsequence of large residual stresses and changes in geometry acting as stress concentrators. The objective of this research is to increase the understanding of the factors that control fatigue life in welded components made from very high strength steels with a yield strength of more than 800 MPa. In particular the influences of the local weld toe geometry (weld toe radius and angle) and residual stress on fatigue life have been studied. Residual stresses have been varied by welding with conventional as well as Low Transformation Temperature (LTT) filler materials. The three non-destructive techniques Weld Impression Analysis (WIA), Laser Scanning Profiling (LSP) and Structured Light Projection (SLP) have been applied to evaluate the weld toe geometry.Results suggest that all three methods could be used successfully to measure the weld toe radius and angle, but the obtained data are dependent on the evaluation procedure. WIA seems to be a suitable and economical choice when the aim is just finding the radius. However, SLP is a good method to fast obtain a threedimensional image of the weld profile, which also makes it more suitable for quality control in production. It was also found that the use of LTTconsumables increased fatigue life and that residual stress has a relatively larger influence than the weld toe geometry on fatigue strength of welded parts.

    Download full text (pdf)
    fulltext
  • 69.
    Harati, Ebrahim
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Dalaei, Kamellia
    ESAB AB, Gothenburg.
    The relative effects of residual stresses and weld toe geometry on fatigue life of weldments2015In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 77, p. 160-165Article in journal (Refereed)
    Abstract [en]

    The weld toe is one of the most probable fatigue crack initiation sites in welded components. In this paper, the relative influences of residual stresses and weld toe geometry on the fatigue life of cruciform welds was studied. Fatigue strength of cruciform welds produced using Low Transformation Temperature (LTT) filler material has been compared to that of welds produced with a conventional filler material. LTT welds had higher fatigue strength than conventional welds. A moderate decrease in residual stress of about 15% at the 300 MPa stress level had the same effect on fatigue strength as increasing the weld toe radius by approximately 85% from 1.4 mm to 2.6 mm. It was concluded that residual stress had a relatively larger influence than the weld toe geometry on fatigue strength.

  • 70.
    Harati, Ebrahim
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Malek Ghaini, Farshid
    Tarbiat Modares University,Tehran.
    Torkamany, Mohammad Javad
    Tarbiat Modares University, Tehran.
    Microstructural Analysis of Laser Cladding of Stellite 6 on Ductile Iron2014In: Proceedings of The 6th International Swedish Production Symposium 2014 / [ed] Johan Stahre, Björn Johansson,Mats Björkman, 2014, p. 1-8Conference paper (Refereed)
    Abstract [en]

    Stellite 6 alloy in the form of powder was deposited on a ductile cast iron substrate using a low power pulsed Nd:YAG laser. The effects of process parameters on the resulting microstructure and hardness were studied with emphasis on the single and multi-track deposits. The results revealed that the cladded layers consist of carbides dispersed in a Co-based solid solution matrix with a dendritic structure. Multi-track cladded layers have coarser dendrites compared to those of single-track cladded layer due to a longer exposure time at high temperature and slower cooling rates as more layers were deposited

    Download full text (pdf)
    fulltext
  • 71.
    Harati, Ebrahim
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Ottosson, Mattias
    University West, Department of Engineering Science, Division of Automation Systems.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Non-destructive measurement of weld toe radius using Weld Impression Analysis, Laser Scanning Profiling and Structured Light Projection methods2014In: Proceedings of First International Conference on Welding and Non Destructive Testing (ICWNDT2014), 2014, p. 1-8Conference paper (Refereed)
    Download full text (pdf)
    fulltext
  • 72.
    Harati, Ebrahim
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    The measurement of weld toe radius using three non-destructive techniques2014In: Proceedings of The 6th International Swedish Production Symposium 201416-18 September 2014 / [ed] Johan Stahre, Björn Johansson,Mats Björkman, 2014, p. 1-8Conference paper (Refereed)
    Abstract [en]

    The three non-destructive methods Weld Impression Analysis, Laser Scanning Profiling and Structured Light Projection were employed to measure the weld toe radius of fillet welds. All three methods could be used succesfully but results are dependent on evaluation procedure. The results show that the weld toe geometry cannot be considered uniform and varies along the weld. It was also found that the measured weld toe radii do not vary significantly with minor variations ofthe surface profile orientation.

    Download full text (pdf)
    fulltext
  • 73.
    Harati, Ebrahim
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Welding Technology.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Welding Technology.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Welding Technology.
    Effect of HFMI treatment procedure on weld toe geometry and fatigue properties of high strength steel welds2016In: Procedia Structural Integrity, Vol. 2, p. 3483-3490Article in journal (Refereed)
    Abstract [en]

    The effects of high frequency mechanical impact (HFMI) treatment procedure on the weld toe geometry and fatigue strength in 1300 MPa yield strength steel welds were investigated. In this regard first the effect of three or six run treatments on the weld toe geometry was evaluated. The fatigue strength and weld toe geometry of as-welded and HFMI treated samples was then compared. Fatigue testing was done under fully reversed, constant amplitude bending load. When increasing the number of treatment runs from three to six, the weld toe radius and width of treatment remained almost constant. However, a slightly smaller depth of treatment in the base metal and a somewhat larger depth of treatment in the weld metal was observed. HFMI treatment increased the fatigue strength by 26%. The treatment did not increase the weld toe radius significantly, but resulted in a more uniform weld toe geometry along the weld. A depth of treatment in the base metal in the range of 0.15-0.19 mm and a width of treatment in the range of 2.5-3 mm, were achieved. It is concluded that the three run treatment would be a more economical option than the six run treatment providing a similar or even more favourable geometry modification.

  • 74.
    Hattinger, Monika
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Organizational e-learning readiness for technology enhanced competence initiatives in the manufacturing industry2015In: Global e-learning / [ed] Landeta Etxeberria, Ana, Madrid: Udima , 2015, 2Chapter in book (Other academic)
  • 75.
    Hattinger, Monika
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Eriksson, Kristina
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Action Design Research: Design of e-WIL for the Manufacturing Industry2015In: The 2015 Americas Conference on Information Systems (AMCIS 2015): Proceedings, 2015, p. 1-14Conference paper (Refereed)
    Abstract [en]

    This paper reports on a design process of e-learning courses for competence development of experienced employees in the manufacturing industry. Through a cross- organizational collaborative action design research project the aim was to design e-learning courses at university level to support work-integrated learning. Two design- and learning cycles were evaluated over two years. The first cycle identified challenges that were applied to a pilot course in Industrial automation. From evaluation of this course we derived design principles applied to two further courses in Machining and Negotiation skills. The results from our empirical data suggest general principles as competence mapping work, collaborative manufacturing e-WIL cases and interactive learning technologies for design of e-WIL courses as boundary crossing activities to reach transformative learning integrated in the manufacturing industry.

    Download full text (pdf)
    fulltext
  • 76.
    Hattinger, Monika
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Eriksson, Kristina
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Malmsköld, Lennart
    University West, Department of Engineering Science, Division of Automation Systems.
    Svensson, Lars
    University West, Department of Economics and IT, Divison of Informatics.
    E-learning Readiness and Absorptive Capacity in the Manufacturing Industry2014In: International Journal of Advanced Corporate Learning, ISSN 1867-5565, E-ISSN 1867-5565, Vol. 7, no 3, p. 33-40Article in journal (Refereed)
    Abstract [en]

    The manufacturing industry constantly strive to develop the competencies of their expert production engineers in order to achieve and maintain a competitive advantage. Research shows that the absorptive capacity of a firm is central in order to reach such a goal. The absorptive capacity is the firm´s ability to recognize the value of new external information, assimilate it, and apply it to commercial ends, and thereby exploit the conditions for innovation. In this paper the concept of absorptive capacity is used as a lens for analyzing managerial rationales for engaging in technology enhanced competence development projects. Through interviews with key informants in 15 manufacturing firms we study the capabilities and readiness that organizations need for participation in e-learning initiatives. We present a framework of readiness for technology enhanced competence development comprised of the following interrelated constructs; awareness, e-learning maturity, dynamic capability and co-creativity. Results show a broad variation of levels within the constructs among the firms. Notable is the low level of e-learning maturity and dynamic capability. We argue that e-learning maturity is dependent on all four constructs.

  • 77.
    Hattinger, Monika
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Eriksson, Kristina
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Malmsköld, Lennart
    University West, Department of Engineering Science, Division of Automation Systems. Chalmers University of Technology, Department of Product and Production Development,.
    Svensson, Lars
    University West, Department of Economics and IT, Divison of Informatics.
    Work-Integrated Learning and Co-creation of Knowledge: Design of collaborative technology enhanced learning activities2014In: Proceedings of the 37th Information Systems Research Seminar in Scandinavia (IRIS 37) / [ed] Ahmad Ghazawneh, Jacob Nørbjerg and Jan Pries-Heje, Ringsted, 2014, p. 1-15Conference paper (Refereed)
    Abstract [en]

    In this paper we aim to understand management’s perceptions of knowledge and competence development to inform the design of technology enhanced learning activities integrated in the workplace. Work-integrated learning can be viewed with the university lens on studies of formal education integrated in the workplace setting, but here we rather emphasize the conditions of the workplace as implications for design of successful e-learning initiatives. We conducted interviews with 15 manufacturing industries in Sweden and used qualitative content analysis approach to interpret the text data. Results show that companies describe a rich variation of work-integrated learning activities, but the step towards external collaboration with academia for co-production of knowledge is marginal. Also, broad-minded work for innovations is limited. This imply the need for well-planned design of richer collaborative acitivites between academia and organizations through use of media technology to encourage competence development.

    Download full text (pdf)
    fulltext
  • 78.
    Hattinger, Monika
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Spante, Maria
    University West, Department of Economics and IT, Divison of Informatics.
    Ruijan, Du
    Mediated and Situated Engineering Education2014In: Proceedings of World Conference on E-Learning in Corporate, Government, Healthcare, and Higher Education 2014, Cheasapeake, VA: Association for the Advancement of Computing in Education, 2014, p. 810-817Conference paper (Refereed)
    Abstract [en]

    This small-scale interview study explore engineering expert teachers’ experiences and ideas of e-learning within engineering education. The aim is to capture teachers`experiences entering educational situations that forces them towards new modes of teaching as well as towards a closer collaboration with the industry engineering professional practice. The study addresses challenges crucial for engineering teachers to master when designing e-learning courses that manufacturing industry needs. In the paper we highlight how teachers’perspectives effect the design of work-integrated e-learning courses. In particular we investigate how teacher express their ideas regarding the transition of campus courses into work-integrated e-learning courses as a new teaching situation. Findings show that teachers are content experts in the engineering knowledge field but lack experiences and support for design of e-learning courses.

  • 79.
    Hattinger, Monika
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Treurnicht, Nico
    Department of Industrial Engineering Stellenbosch University, South Africa.
    Learning Aspects for Manufacturing Enterprises within Aerospace industry entering into Quality Standard AS91002011In: 24th ICDE World Conference on Open and Distance Learning: Expanding Horizons- new approaches to ODL, 2011, p. 1-11Conference paper (Refereed)
    Abstract [en]

    The aerospace industry is expected to grow substantially during the next two decades. As a result more suppliers aim for entering into this industry. Demands on safety and quality in this sector are particularly high, where SME´s must upgrade from the generic group of quality standards, the ISO9000 family, to AS9100, the aerospace standard. In this research we focus on the meaning of learning processes for successful implementation of quality standards in a workplace context at a manufacturing company. By using Blooms Revised Taxonomy of learning, we can understand, evaluate and design actions for continuous improvement which can be supported by an IT-based tool for self-assessment supporting organisational learning and implementation of the Quality Management System.

  • 80.
    Hosseini, Vahid A.
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Aashuri, H.
    Materials Science and Engineering Dep., Sharif University of Technology, Tehran, Iran.
    Kokabi, A. H.
    Materials Science and Engineering Dep., Sharif University of Technology, Tehran, Iran.
    Study of the effect of tool geometry on semisolid stir welding of a AZ91 magnesium alloy2015In: Proceedings of the 18th International Conference on Joining Materials, JOM-Institute , 2015, p. 1-10Conference paper (Refereed)
    Abstract [en]

    Semisolid stir welding is a newly developed method suitable for joining of the magnesium alloy AZ91. In this study, the effect of tool geometries on the joint properties such as bending strength and the occurrence of porosity are studied. A 2 mm-thick Mg-25%Zn interlayer was placed between two AZ91 plates and the plate was heated up to 530°C before joining. At this temperature, when both the interlayer and the base metal were in the semisolid state, a stirrer was introduced into the joint. Drill-tip and round shape stirrer tools were employed at three different stirring rates. Welds produced with the two methods showed similar properties in the shear punch test. However, using the round tool geometry resulted in welds with excellent bending strength closely matching that of the base metal especially at the highest stirring rate. The improved properties when using the round tool was a result of the formation of a very fine and uniform microstructure with a low content of porosity.

  • 81.
    Hosseini, Vahid A.
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes. Innovatum AB, Trollhättan, Sweden.
    Valiente Bermejo, María Asunción
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Gårdstam, Johannes
    Swerea KIMAB AB, Kista, Sweden.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Influence of multiple thermal cycles on microstructure of heat-affected zone in TIG-welded super duplex stainless steel2016In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 60, no 2, p. 233-245Article in journal (Refereed)
    Abstract [en]

    The influence of heat input and multiple welding cycles on the microstructure of the heat-affected zone in autogenously TIG-welded 6 mm 2507 type super duplex stainless steel plates was investigated. In order to produce multiple thermal cycles, one to four pass bead-on-plate welds were made with arc energies of 0.47 and 1.08 kJ/mm, corresponding to heat inputs of 0.37 and 0.87 kJ/mm. Several thermocouples were attached to record thermal cycles on the front and back sides of the plates. Finite element modelling was successfully done to map and correlate measured and calculated peak temperatures. Only minor changes were seen in the ferrite content at 1 and 2 mm from the fusion boundary. Nitrides formed in all passes of the low heat input samples in a region next to the fusion boundary, but only after the third and fourth passes of the high heat input samples. Sigma phase precipitated only in a zone heated to a peak temperature in the range of approximately 828 to 1028 °C. Multiple reheating was found to promote precipitation of sigma phase relatively more than slower cooling. A precipitation free zone was observed between the nitride and sigma phase bands. The precipitation behaviour could be understood from equilibrium phase diagrams, evaluation of local thermal cycles and by correlating results from the modelling and measurements of peak temperatures. It is suggested that the peak temperature, the accumulated time in the critical temperature range between approximately 828 and 1028 °C, and the number of thermal cycles are the most relevant criteria when evaluating the risk of sigma phase formation.

  • 82.
    Hosseini, Vahid A.
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Wessman, Sten
    University West, Department of Engineering Science, Division of Manufacturing Processes. Swerea KIMAB AB, Kista, Sweden.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nitrogen loss and effects on microstructure in multipass TIG welding of a super duplex stainless steel2016In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 98, no May, p. 88-97Article in journal (Refereed)
    Abstract [en]

    Nitrogen loss is an important phenomenon in welding of super duplex stainless steels. In this study, a super duplex stainless steel was autogenously TIG-welded with one to four bead-on-plate passes with low or high heat inputs using pure argon shielding gas. The goal was to monitor nitrogen content and microstructure for each weld pass. Nitrogen content, measured by wavelength dispersive X-ray spectrometry, was after four passes reduced from 0.28 wt% in the base metal to 0.17 wt% and 0.10 wt% in low and high heat input samples, respectively. Nitrogen loss resulted in a more ferritic structure with larger grains and nitride precipitates. The ferrite grain width markedly increased with increasing number of passes and heat input. Ferrite content increased from 55% in base metal to 75% at low and 79% at high heat inputs after four passes. An increasing amount of nitrides were seen with increasing number of weld passes. An equation was suggested for calculation of the final nitrogen content of the weld metal as functions of initial nitrogen content and arc energy. Acceptable ferrite contents were seen for one or two passes. The recommendation is to use nitrogen in shielding gas and proper filler metals.

  • 83.
    Hosseini, Vahid
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Multipass Autogenous TIG Welding of Super Duplex Stainless2015In: 16th national conference of welding and inspection, Yazd, Iran: Proceedings, Yazd, 2015Conference paper (Refereed)
    Abstract [en]

    Multipass welding of super duplex stainless steels (SDSS) needs further characterization due to their growing applications inpetrochemical and offshore industries. This study, as a result, is aimed at investigating the effects of the number of passesand the arc energy on the microstructure and properties of 2507-type SDSS (UNS S32750). From one to four TIG weldpasses were autogenously applied on a plate using two different arc energies and with pure argon gas as the shielding gas.Chemical analysis showed increasing nitrogen loss with an increasing number of passes and increasing arc energy.Microstructural analyses revealed formation of nitrides in the weld metal and heat affected zone, and sigma phase at somedistance from the fusion boundary. Thermal cycle analysis in combination with Thermo-Calc calculations indicated thatexcessive reheating cause degradation of corrosion properties of multipass weldments, by reducing the pitting resistanceequivalent number of austenite to less than 40. Multipass welding resulted in a more ferritic weld metal microstructure and anincreased hardness.Recommendations, based on the present study, are as follows: 1) Corrosion attack can occur not only in the weld zone andnext to the fusion boundary, but also in a location at some distance from the fusion zone due to reheating in the sigma phaseformation temperature range. This should be considered in inspection procedures 2) Nitrogen loss degrades the mechanicaland corrosion properties of weldments even when welding with a low heat input. Using filler metals with higher nickelcontents and nitrogen containing shielding gases are therefore recommended. 3) It is often recommended to use a heat inputin the lower end of the recommended 0.3-1.5 kJ/mm range in multipass welding of super duplex stainless steels. However,welding with a higher heat input and fewer passes, in some cases, can decrease the risk of formation of secondary phases.

  • 84.
    Hosseini, Vahid
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Shabestari, S.G.
    Iran University of Science and Technology (IUST), Center of Excellence for High Strength Alloys Technology (CEHSAT), School of Metallurgy and Materials Engineering, Narmak, Tehran, Iran.
    Study on the eutectic and post-eutectic reactions in LM13 aluminum alloy using cooling curve thermal analysis technique2016In: Journal of thermal analysis and calorimetry (Print), ISSN 1388-6150, E-ISSN 1588-2926, Vol. 124, no 2, p. 611-617Article in journal (Refereed)
    Abstract [en]

    Effect of non-equilibrium solidification conditions on the eutectic and post-eutectic reactions temperature and percentage of the phases were investigated using computer-aided cooling curve thermal analysis. In addition, hardness, secondary dendrite arm spacing, and maximum pore size were studied at different cooling conditions. Cooling curves were determined by setting thermocouples in the center of the molds. Solid fractions were calculated by Newtonian baseline technique. Results showed that increasing the cooling rate shifted the temperature of post-eutectic reaction upward, except final reaction. Higher cooling rate increased eutectic percentage about 4 %, but reduced total percentage of post-eutectic phases. Additionally, increasing the cooling rate shortened the maximum porosity diameter and secondary dendrite arm spacing and increased the hardness of the alloy. © 2015 Akadémiai Kiadó, Budapest, Hungary

  • 85.
    Hurtig, Kjell
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Choquet, Isabelle
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Scotti, Americo
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    A critical analysis of weld heat input measurement through a water-cooled stationary anode calorimeter2015In: Proceedings of JOM 18 International conference on joining materials, Helsingör, Danmark, april 26-29, 2015, JOM-institute , 2015, p. 1-19Conference paper (Refereed)
    Abstract [en]

    A comprehensive model on heat transfer in welded plates is able to calculate the amount of heat losses from the surfaces. A model demands as input parameter the amount of heat delivered to the plate, independently of any loss (called here gross heat input for clarity). However, the great discrepancies among the results of calorimetric measurements have left many researchers skeptical about using this parameter in modeling as absolute term. The objective of this work was to assess the use of a water-cooled stationary anode calorimeter to obtain not only arc efficiency, but also gross heat input. A series of tests was carried out to determine the effect of current, material type and water flow rate on the calorimeter performance, as well as to evaluate some measures for reducing the calorimeter intrinsic errors. Finally, a sensitivity test was conducted to estimate the effect of measurement inaccuracies on the absorbed heat and arc efficiency values. The results showed that this calorimetric approach is a simple way for measuring gross heat inputs in arc welding. Nevertheless some improvement to reduce heat losses from the top surface and boost heat sinking from the opposite surface of the test coupon must be applied. This calorimeter is, on the other hand, highly sensitive to the parameter measurements, leading to errors up to ± 0.09 in arc efficiency determination if the instrument is not properly calibrated and installed.

  • 86.
    Hurtig, Kjell
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Choquet, Isabelle
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Scotti, Americo
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering.
    A critical analysis of weld heat input measurement through a water-cooled stationary anode calorimeter2016In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 21, no 5, p. 339-350Article in journal (Refereed)
    Abstract [en]

    Comprehensive models of heat transfer require specification of the total amount of heat received by the workpiece. The objective of this work was to critically examine the use of a water-cooled stationary anode calorimeter to obtain both arc efficiency and total heat input into the workpiece. For simplicity and clarity, this last quantity is called the gross heat input. The effects of current, material type and water flow rate on the calorimeter performance were determined experimentally. Some measures for reducing errors in calorimetry were evaluated. Improvements were made to reduce heat losses from the top surface of the test coupon and boost heat removal from the opposite surface. A sensitivity test was conducted to estimate the effect of measurement inaccuracies. The results demonstrate the effectiveness of calorimetry for measuring gross heat input in arc welding.

  • 87.
    Hussain, Dena
    et al.
    University West, Department of Engineering Science, Division of Computer, Electrical and Surveying Engineering.
    Gustavsson Christiernin, Linn
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Inter-communication management in cases with disabled children2015In: International Conference on Information Society, Technical Co-Sponsored by IEEE UK/RI Computer Chapter, November 9-11, 2015, London, UK: Proceedings / [ed] Charles A. Shoniregun & Galyna A. Akmayeva, Infonomics Society, 2015, p. 30-31Conference paper (Refereed)
    Abstract [en]

    Since the use of Information and communication tools has offered new possibilities for improving different aspect of the healthcare sector, the objective of this research is to design an Information and Communication Technology (ICT) tool to assist the learning process of caretakers of special need children inSweden. The research is based on long-term observations and indepth interviews with key experts, with the aim of developing a tool which should assist the intercommunication between caretakers, creating optimized action plans in a work integrated environment. Enhancing the learning processes of the caretakers’methods and knowledge of each other’s work processes through knowledge bridging between all caretakers involved and hence have a direct influence on the child’s development.

  • 88.
    Javidi Shirvan, Alireza
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Choquet, Isabelle
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nilsson, Håkan
    Chalmers University of Technology.
    Effect of cathode model on arc attachment for short high-intensity arc on a refractory cathode2016In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 49, no 3 November 2016, p. 1-17, article id 485201Article in journal (Other academic)
    Abstract [en]

    Various models coupling the refractory cathode, the cathode sheath and the arc at atmospheric pressure exist. They assume a homogeneous cathode with a uniform physical state, and differ by the cathode layer and the plasma arc model. However even the most advanced of these models still fail in predicting the extent of the arc attachment when applied to short high-intensity arcs such as gas tungsten arcs. Cathodes operating in these conditions present a non-uniform physical state. A model taking into account the first level of this non-homogeneity is proposed based on physical criteria. Calculations are done for 5 mm argon arcs with a thoriated tungsten cathode. The results obtained show that radiative heating and cooling of the cathode surface are of the same order. They also show that cathode inhomogeneity has a significant effect on the arc attachment, the arc temperature and pressure. When changing the arc current (100 A, 200 A) the proposed model allows predicting trends observed experimentally that cannot be captured by the homogeneous cathode model unless restricting a priori the size of the arc attachment. The cathode physics is thus an important element to include to obtain a comprehensive and predictive arc model

  • 89.
    Javidi Shirvan, Alireza
    et al.
    University West, Department of Engineering Science, Divison of Natural Sciences, Surveying and Mechanical Engineering.
    Choquet, Isabelle
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nilsson, Håkan
    Chalmers University of Technology.
    Modelling of electrode-arc coupling in electric arc welding2014In: Proceedings of The 6th International Swedish Production Symposium 2014 16-18 September 2014 / [ed] Johan Stahre, Björn Johansson,Mats Björkman, 2014, p. 1-8Conference paper (Refereed)
    Abstract [en]

    Modelling of the arc in electric arc welding is significant to achieve a better pro-cess understanding, thus gain better weld quality and a more efficient production process.It requires knowing the conditions at the surfaces of the anode and cathode. These condi-tions are very difficult to set from measurements and should be calculated. This requiresmodelling the complex physics of the electrode layer coupling electrode and arc. Thispaper presents a self-consistent electrode layer model that 1) is suited to welding applica-tions, 2) accounts for the known physics taking place, and 3) satisfies the basic conservationrequirements. The model is tested for different conditions. Its potentiality for welding ap-plications is shown through calculations coupling plasma arc, electrode and cathode layermodels. The calculations are done for both tungsten and thoriated tungsten electrode.

    Download full text (pdf)
    fulltext
  • 90.
    Javidi Shirvan, Alireza
    et al.
    University West, Department of Engineering Science, Division of Welding Technology.
    Choquet, Isabelle
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nilsson, Håkan
    Chalmers University of Technology, Department of Mechanics and Maritime Sciences, 412 96 Gothenburg, Sweden..
    Jasak, Hrvoje
    University of Zagreb, Faculty of Mechanical Engineering and Naval Architecture, 10 000 Zagreb, Croatia..
    Coupling boundary condition for high-intensity electric arc attached on a non-homogeneous refractory cathode2018In: Computer Physics Communications, ISSN 0010-4655, E-ISSN 1879-2944, Vol. 222, p. 31-45Article in journal (Refereed)
  • 91.
    Johansson, Anders
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. Global Industrial Development, Scania CV AB, Södertälje.
    Pejryd, Lars
    School of Science and Technology, Örebro University.
    Gustavsson Christiernin, Linn
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Consideration of market demand volatility risks, when making manufacturing system investments2016In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 40, p. 307-311Article in journal (Refereed)
    Abstract [en]

    When investing in new manufacturing systems, many aspects must be taken into consideration to ensure a sustainable business. In respect to the financial aspect, both the one-off investment cost and the continuous operational cost must be analysed to ensure that the life-cycle cost perspective is appreciated. However, one detail in the cost analyses that is often overlooked is the composition of fixed and variable cost elements. These details are important to be able to better manage the risk of market demand volatility, and accordingly make appropriateinvestment decisions. This case study demonstrates that when there is a low risk for reduced market demand, investing in a manufacturing system with low variable cost is favourable. However, if there is a high risk for reduced market demand, the importance will instead be to have a low fixed cost, as this will be the dominant cost factor.

  • 92.
    Kovářík, Ondrej
    et al.
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Haušild, Petr
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Medricky, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Tomek, Libor
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Siegl, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Mušálek, Radek
    Institute of Plasma Physics CAS..
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Fatigue crack growth in bodies with thermally sprayed coating2015In: Proceedings from the International Thermal Spray Conference (May 11–14, 2015, Long Beach, California, USA), ASM International, 2015, Vol. 1-2, p. 398-405Conference paper (Refereed)
    Abstract [en]

    Many applications of thermally sprayed coatings call for increased fatigue resistance of coated parts. Despite the intensive research in this area, the influence of coating on fatigue is still not completely understood. In this paper, the spatiotemporal localization of crack initiation and the dynamics of crack propagation are studied. The resonance bending fatigue test is employed to test flat specimens with both sides coated. Hastelloy-X substrates coated with classical TBC YSZ/NiCoCrAlY composites were tested. The strain distribution on the coating surface is evaluated by the digital image correlation method (DIC) through the whole duration of the fatigue test. Localization of crack initiation sites and the mode of crack propagation in the coated specimen are related to the observed resonance frequency. The individual phases of specimen degradation, i.e. the changes of material properties, crack initiation, and crack propagation are identified. The tested coatings strongly influenced the first two phases, the influence on the crack propagation was less significant. © Copyright (2015) by ASM International All rights reserved.

  • 93.
    Kovářík, Ondrej
    et al.
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Haušild, Petr
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Medřický, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic..
    Tomek, Libor
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Siegl, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Mušálek, Radek
    Institute of Plasma Physics CAS.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Fatigue Crack Growth in Bodies with Thermally Sprayed Coating2016In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 25, no 1-2, p. 311-320Article in journal (Refereed)
    Abstract [en]

    Many applications of thermally sprayed coatings call for increased fatigue resistance of coated parts. Despite the intensive research in this area, the influence of coating on fatigue is still not completely understood. In this paper, the localization of crack initiation sites and the dynamics of crack propagation are studied. The resonance bending fatigue test was employed to test flat specimens with both sides coated. Hastelloy-X substrates coated with classical thermal barrier coating consisting of yttria stabilized zirconia and NiCoCrAlY layers. The strain distribution on the coating surface was evaluated by the Digital Image Correlation method through the whole duration of the fatigue test. Localization of crack initiation sites and the mode of crack propagation in the coated specimen are related to the observed resonance frequency. The individual phases of specimen degradation, i.e., the changes of material properties, crack initiation, and crack propagation, were identified. The tested coatings strongly influenced the first two phases, and the influence on the crack propagation was less significant. In general, the presented crack detection method can be used as a sensitive nondestructive testing method well suited for coated parts. © 2015 ASM International

  • 94.
    Kovářík, Ondrej
    et al.
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Haušild, Petr
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Čapek, Jiří
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Medřický, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Siegl, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Mušálek, Radek
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Pala, Zdeněk
    Institute of Plasma Physics AS CR, v.v.i., Prague, Czech Republic.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Resonance bending fatigue testing with simultaneous damping measurement and its application on layered coatings2016In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 82, Part 2, p. 300-309Article in journal (Refereed)
    Abstract [en]

    Abstract The use of specimen loss factor as fatigue damage indicator of Hastelloy-X substrates with different surface treatments was investigated together with other fatigue damage indicators, namely resonance frequency and crack mouth length. The tested surface treatments included grit-blasting and plasma spraying of NiCoCrAlY bond coat and yttria stabilized zirconia (YSZ) top coat. The loss factors of fatigue test specimens were measured repeatedly during the resonance bending fatigue test using the conventional free decay method. The analysis of the damping spectra, i.e. the model describing the relation of loss factor to maximum macroscopic specimen strain εyy was drafted. The model is based on the combination of defect models developed by Göken and Riehemann (2004) and classical dislocation model of Granato and LÌcke (1956). It appears, that the damping spectra can be well approximated as a combination of two defect peaks (C1 and C2) and one dislocation peak (D1). The low strain defect peak (peak C1) is sensitive to the presence of fatigue cracks. The second defect peak (peak C2) can be attributed to the remaining substrate and coating defects such as embedded grit particles, coating porosity, surface roughness and sliding in the sample clamping area. The fatigue damage detection using the C1 peak magnitude was performed and its results were related to the crack length obtained by digital image correlation (DIC) method. In the crack initiation stage I., the C1 peak height shows different behavior than the resonance frequency and therefore provides new information. The underlying processes causing C1 peak changes need to be found yet, however. In the crack growth stage II., both resonance frequency and peak height C1 correlate with the measured fatigue crack size.

  • 95.
    Kovářík, Ondřej
    et al.
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Haušild, Petr
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Čapek, Jiří
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Medřický, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Siegl, Jan
    Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic.
    Mušálek, Radek
    Institute of Plasma Physics AS CR, v.v.i., Prague, Czech Republic.
    Pala, Zdeněk
    Institute of Plasma Physics AS CR, v.v.i., Prague, Czech Republic.
    Curry, Nicholas
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Damping measurement during resonance fatigue test and its application for crack detection in TBC samples2016In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 82, no Part 2, p. 300-309Article in journal (Refereed)
    Abstract [en]

    Abstract The use of specimen loss factor as fatigue damage indicator of Hastelloy-X substrates with different surface treatments was investigated together with other fatigue damage indicators, namely resonance frequency and crack mouth length. The tested surface treatments included grit-blasting and plasma spraying of NiCoCrAlY bond coat and yttria stabilized zirconia (YSZ) top coat. The loss factors of fatigue test specimens were measured repeatedly during the resonance bending fatigue test using the conventional free decay method. The analysis of the damping spectra, i.e. the model describing the relation of loss factor to maximum macroscopic specimen strain εyy was drafted. The model is based on the combination of defect models developed by Göken and Riehemann [1] and classical dislocation model of Granato and LÌcke [2]. It appears, that the damping spectra can be well approximated as a combination of two defect peaks (C1 and C2) and one dislocation peak (D1). The low strain defect peak (peak C1) is sensitive to the presence of fatigue cracks. The second defect peak (peak C2) can be attributed to the remaining substrate and coating defects such as embedded grit particles, coating porosity, surface roughness and sliding in the sample clamping area. The fatigue damage detection using the C1 peak magnitude was performed and its results were related to the crack length obtained by digital image correlation (DIC) method. In the crack initiation stage I., the C1 peak height shows different behavior than the resonance frequency and therefore provides new information. The underlying processes causing C1 peak changes need to be found yet, however. In the crack growth stage II., both resonance frequency and peak height C1 correlate with the measured fatigue crack size.

  • 96.
    Lahti, K.
    et al.
    Lappeenranta University of Technology, Finland.
    Hiltunen, E.
    Lappeenranta University of Technology, Finland.
    Pirinen, M.
    Lappeenranta University of Technology, Finland.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Submerged Arc Welding of High Strength Steel for Shipbuilding Applications2015In: Proceedings of JOM 18 International conference on joining materials, Helsingör, Danmark, april 26-29 2015, JOM-institute , 2015, p. 1-8Conference paper (Refereed)
    Abstract [en]

    In most cases primary purpose for use of high strength steels is weight reduction with resulting benefits in product lifecycle costs. However, as the operating environments vary, it is important to take consideration to the specific requirements for the product in concern. In this study, high strength steel F40SW (YS 460 MPA, UTS 550 MPa) for use in arctic conditions, e.g., icebreakers, are welded with submerged arc welding (SAW) and resulting welds are analyzed for mechanical and metallurgical properties. Submerged arc welding (SAW) is preferred joining process for thick steel plates in shipbuilding.However, as the mechanical properties of steel are improved, restrictions in heat input are often set thus limiting effective use of SAW, and probably therefore Manual Metal Arc (MMA) welding and manual Gas Metal Arc (GMA) welding are typically the processes mainly referenced in literature when welding steels with higher strength levels are studied. In this study, submerged arc welds on F40SW steel were made with overmatching tubular and solid welding wire at heat input levels above the normally recommended maximum of approximately 2,0 kJ/mm. Resulting welds were tested for mechanical properties with focus on toughness properties at low temperatures.Impact toughness KV 150 / 7,5 at -60°C was above 27J for both tested wires in the weld and at the heat affected zone (HAZ). Tested yield and tensile strength of the joints matched unwelded base material and all of the samples were broken at the base material far from the weld and HAZ area. Also the 180° bending tests for both surface- and rootside were passed without remarks. Based on the findings in this study, no obvious limitations for use of submerged arc welding in joining of arctic grade steel F40SW were observed. This encourages for increased use of SAW as economical and environmentally sound joining process for this kind of steel.

  • 97.
    Lahti, K.
    et al.
    Lappeenranta University of Technology, Finland.
    Hiltunen, E.
    Lappeenranta University of Technology, Finland.
    Pirinen, M.
    Lappeenranta University of Technology, Finland.
    Karlsson, Leif
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Martikainen, J.
    Lappeenranta University of Technology, Finland.
    Productivity Aspects in Submerged Arc Welding of Thick High-Strength Steels2015In: Proceedings of IIW International Conference, High-Strength Materials: Challenges and Applications, 2-3 July 2015, Helsinki, Finland, Helsingfors, 2015, Helsingfors, 2015, Vol. 0904, p. 1-6-Conference paper (Refereed)
    Abstract [en]

    A series of welding tests were made on 35 mm thick F500W high strength steel. This specific steel grade is developed for use in arctic conditions, especially in shipbuilding, and it has excellent impact toughness at temperatures down to -60°C. Submerged arc welding tests were performed using solid and flux-cored welding wire keeping the heat-input at levels typically recommended for thermo mechanically processed highstrengthsteels. Process improvement trials were even made using electrode extension (EE) allowing for higher melt-on rates without any increase in the heat input.However, as the chemical composition of F500W allows for higher heat input without risk for excessive grain growth, tests at higher heat inputs were also made as reference for additional ways to increase productivity. Three fundamental means for improving productivity were analyzed in this study: 1) use of solid or flux-cored wire, 2) effect of groove preparation, and 3) use ofelectrode extension. These all can be introduced without changes in heat input, and hence implementation to existing production systems is easy, economical and quick. Highest increase in productivity is gained by using electrode extension with optimized groove geometry. In the studied thickness of 35 mm, the number of runs was decrease by 60 % from 22 to 9 without increase in the heat input and with approved mechanical properties for this specific steel. Based on the outcome of this study, submerged arc welding can successfully be used for joining of this high strength steel with approved mechanical properties and high productivity.

  • 98.
    Li, C.
    et al.
    University of Manchester, School of Materials, M13 9PL, UK.
    Jacques, S. D. M.
    University of Manchester, School of Materials, M13 9PL, UK.
    Chen, Y.
    University of Manchester, School of Materials, M13 9PL, UK.
    Xiao, Ping
    University of Manchester, School of Materials, M13 9PL, UK.
    Beale, A. M.
    University College London, RCaH Rutherford Appleton Laboratory, Harwell Oxford Didcot Oxon, OX11 0FA, UK.
    di Michiel, M.
    ESRF-The European Synchrotron, 71, Avenue des Martyrs, Grenoble, France.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Cernik, R. J.
    University of Manchester, School of Materials, M13 9PL, UK.
    Precise strain profile measurement as a function of depth in thermal barrier coatings using high energy synchrotron X-rays2016In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 113, p. 122-126Article in journal (Refereed)
    Abstract [en]

    We have developed a method of directly measuring the strain gradient as a function of depth in plasma sprayed Thermal Barrier Coatings (TBCs). A 92.8 keV monochromatic synchrotron X-ray beam was used to penetrate the 10 × 10 × 8 mm samples in transmission geometry. The samples had been heated to 1150 °C and held at that temperature for 190 h. The diffraction patterns were collected using a DECTRIS pilatus3 X CdTe 300 K area detector. The patterns were analyzed by partial circular integration followed by full Rietveld refinement to obtain the lattice parameters of the TBC top coat at 25 μm intervals as function of depth. The coatings surviving the heat treatment process without significant damage were found to exhibit a variable compressive stress state inside the top coat. This was found to be about − 600 MPa at the bond coat interface decreasing in a non-linear fashion towards the surface. By refinement of the data collected from sectors of whole Debye Scherrer rings we were able to estimate both the in-plane and out-of-plane strain.

  • 99.
    Li, Peigang
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. University West, Department of Engineering Science, Division of Production Engineering.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Influence of preheating temperature on cold lap formation in tandem GMAW2013Conference paper (Other academic)
    Abstract [en]

    A cold lap is defined as a type of micro-lack of fusion in ISO standard (ISO 6520-1:2007) and have been found to influence fatigue properties of welds significantly. In the present study, the main purpose was to investigate the influence of preheating temperature on cold lap formation in tandem GMAW, both with respect to dimensions and occurrence probabilities.

    Three different preheating temperatures were applied and cross-sections of welds were evaluated by light optical microscopy. The results showed that the cold lap occurrence frequency is a function of base metal temperature. However, the base metal temperature does not have a significant influence on cold lap depth.

  • 100.
    Li, Peigang
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering. University West, Department of Engineering Science, Division of Production Engineering.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Study on temperature influence on lack of fusion formation in spatter/base metal interface2014In: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 875 - 877, p. 1421-1428Article in journal (Refereed)
    Abstract [en]

    In the development of modern welded structures with longer life-time and/or higher load-carrying ability, fatigue properties are becoming more and more important. A lot of researches have been done to investigate which factors can elongate the fatigue life of weldments. Cold lap defects, were found to be important initiation sites of the fatigue failure in 1990s. In the ISO standard, cold lap is referred to as a type of micro-lack of fusion. Previous study found that most of the cold laps in GMAW process are formed in spatters. In this paper the interface of spatter/base metal was cut, polished and investigated by conventional metallographic methods. The aim is to reveal the influence of temperature on cold lap formation. In the experiments, different pre-heating temperatures of the parent plate were used in tandem GMAW. Results showed linear empirical relationship between the temperature of the parent plate and the amount of lack of fusion in the spatter/base metal interface.

1234 51 - 100 of 157
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf