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  • 51.
    Eynian, Mahdi
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Altintas, Y.
    University of British Columbia, Department of Mechanical Engineering, Manufacturing Automation Laboratory.
    Analytical Chatter Stability of Milling With Rotating Cutter Dynamics at Process Damping Speeds2010In: Journal of manufacturing science and engineering, ISSN 1087-1357, E-ISSN 1528-8935, Vol. 132, no 2Article in journal (Refereed)
    Abstract [en]

    This paper presents a chatter stability prediction method for milling flexible workpiece with end mills having asymmetric structural dynamics. The dynamic chip thickness regenerated by the vibrations of the rotating cutter and the fixed workpiece is transformed into the principle modal directions of the rotating tool. The process damping is modeled as a linear function of vibration velocity. The dynamics of the milling system is modeled by a time delay matrix differential equation with time varying directional factors and speed dependent elements. The periodic directional factors are averaged over a spindle period, and the stability of the resulting time invariant but speed dependent characteristic equation of the system is investigated using the Nyquist stability criterion. The stability model is verified with time domain numerical simulations and milling experiments.

  • 52.
    Fahlström, Karl
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West. University West, Department of Engineering Science, Research Environment Production Technology West.
    Andersson, Oscar
    Volvo Cars, Torslanda, Sweden.
    Karlsson, Leif
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering. University West, Department of Engineering Science, Division of Welding Technology.
    Metallurgical effects and distortions in laser welding of thin sheet steels with variations in strength2017In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 22, no 7, p. 573-579Article in journal (Refereed)
    Abstract [en]

    Geometrical distortions occur while welding, but the understanding of how and why they occur and how to control them is limited. The relation between the weld width, weld metal volume, total energy input, width of hard zone and distortions when laser welding three different thin sheet steels with varying strength has therefore been studied. Weld metal volume and total energy input show a good correlation with distortion for one steel at a time. The best correlation with the when including all three steel grades was the width of the hard zone composed of weld metal and the martensitic area in the heat affected zone. © 2017 Institute of Materials, Minerals and Mining. Published by Taylor & Francis on behalf of the Institute.

  • 53.
    Fahlström, Karl
    et al.
    Swerea KIMAB.
    Andersson, Oscar
    KTH Royal Institute of Technology.
    Todal, Urban
    Volvo Car Corporation.
    Melander, Arne
    Swerea KIMAB.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering.
    Karlsson, Leif
    University West, Department of Engineering Science, Divison of Natural Sciences, Surveying and Mechanical Engineering.
    Distortion Analysis in Laser Welding of Ultra High Strength Steel2014In: Proceedings of the 6th International Swedish Production Symposium 2014 / [ed] Stahre, Johan, Johansson, Björn & Björkman, Mats, 2014, p. 1-9Conference paper (Refereed)
    Abstract [en]

    Due to increased demands on reduced weight in automotive industries, the use of ultra high strength steels (UHSS) has increased. When laser welding UHSS sheets, heating and cooling of the material will cause geometrical distortions and may cause low joint quality. 700 mm long U-beam structures of 1 mm thick boron steel simulating structural pillars in body-in-white constructions have been welded along the flanges with different welding speeds to investigate distortions and weld quality. The results show that final distortions appear in the range of 0-8 mm. FE simulation methods have also been presented which generally predict the distribution of welding distortions.

  • 54.
    Fasth, Angelica
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylen, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Choi, B.
    Center for Theraml Spray Research, Stony Brook, New York.
    Klement, Uta
    Chalmers University.
    A Comparative studey of Mechanical Properties Between HVOF-spryed Maxphase Materials and Plasma Sprayed MCrAIY Coatings2009In: Surface Modification Technologies XXII: Proceedings of the Twenty Second International Conference on Surface Modification Technologies Held at University West, Trollhättan, Sweden September 22-24 2008 / [ed] T.S. Sudarshan & Per Nylen, VALAR Docs , 2009, p. 149-156Conference paper (Other academic)
  • 55.
    Fasth, Angelica
    et al.
    University West, Department of Engineering Science.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science.
    Musalek, Radek
    Characterization of thermo-mechanical properties for thermal sprayed NiCoCrAlY coatings2010In: Proceedings of the Thermal Spray: Global Solutions for Future Application (ITSC 2010) Conference: Singapore, May 3-5, 2010, 2010, p. 431-435Conference paper (Refereed)
  • 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.
    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

  • 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 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.

  • 58.
    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.

  • 59.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Eriksson, Robert
    Linköping University, Linköping, Sweden.
    Sand, Ulf
    EDR Medeso, Västerås, Sweden.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    A Diffusion-based Oxide Layer Growth Model using Real Interface Roughness in Thermal Barrier Coatings for Lifetime Assessment2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 271, no June, p. 181-191Article in journal (Refereed)
    Abstract [en]

    The development of thermo-mechanical stresses during thermal cycling can lead to the formation of detrimental cracks in Atmospheric Plasma Sprayed (APS) Thermal Barrier Coatings systems (TBCs). These stresses are significantly increased by the formation of a Thermally Grown Oxide (TGO) layer that forms through the oxidation of mainly aluminium in the bondcoat layer of the TBC. As shown in previous work done by the authors, the topcoat-bondcoat interface roughness plays a major role in the development of the stress profile in the topcoat and significantly affects the lifetime of TBCs. This roughness profile varies as the TGO layer grows and changes the stress profile in the topcoat leading to crack propagation and thus failure.

    In this work, a two-dimensional TGO growth model is presented, based on oxygen and aluminium diffusion-reaction equations, using real interface profiles extracted from cross-section micrographs. The model was first validated by comparing the TGO profiles artificially created by the model to thermally cycled specimens with varying interface roughness. Thereafter, stress profiles in the TBC system, before and after the TGO layer growth, were estimated using a finite element modelling model described in previous work done by the authors. Three experimental specimens consisting of the same chemistry but with different topcoat-bondcoat interface roughness were studied by the models and the stress state was compared to the lifetimes measured experimentally. The combination of the two models described in this work was shown to be an effective approach to assess the stress behaviour and lifetime of TBCs in a comparative way.

  • 60.
    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.

  • 61.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Skogsberg, Kristoffer
    University West, Department of Engineering Science.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Influence of topcoat-bondcoat interface roughness on stresses and lifetime in Thermal Barrier Coatings2013In: Proceedings of the International Thermal Spray Conference / [ed] Editor: Rogerio S. Lima, Arvind Agarwal, Margaret M. Hyland, Yuk-Chiu Lau, Georg Mauer, André McDonald, and Filofteia-Laura, ASM International, 2013, p. 596-601Conference paper (Refereed)
    Abstract [en]

    Failure in Atmospheric Plasma Sprayed (APS) Thermal Barrier Coatings (TBCs) is associated with the thermomechanical stresses developing due to the Thermally Grown Oxide (TGO) layer growth and thermal expansion mismatch during thermal cycling. The interface roughness has been shown to play a major role in the development of these induced stresses and lifetime of TBCs. Modeling has been shown as an effective tool to understand the effect of interface roughness on induced stresses. In previous work done by the research group, it was observed that APS bondcoats performed better than the bondcoats sprayed with High Velocity OxyFuel (HVOF) process which is contrary to the present literature data. The objective of this work was to understand this observed difference in life-time with the help of finite element modeling by using real surface topographies. Different TGO layer thicknesses were evaluated. The modeling results were also compared with existing theories established on simplified sinusoidal profiles published in earlier works. It was shown that modeling can be used as an effective tool to understand the stress behavior in TBCs with different roughness profiles.

  • 62.
    Gupta, Mohit Kumar
    et al.
    University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Skogsberg, Kristoffer
    University West, Department of Engineering Science.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Influence of Topcoat-Bondcoat Interface Roughness on Stresses and Lifetime inThermal Barrier Coatings2014In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 23, no 1-2, p. 170-181Article in journal (Refereed)
    Abstract [en]

    Failure in Atmospheric Plasma Sprayed (APS) Thermal Barrier Coatings (TBCs) is associated with the thermo-mechanical stresses developing due to the Thermally Grown Oxide (TGO) layer growth and thermal expansion mismatch during thermal cycling. The interface roughness has been shown to play a major role in the development of these induced stresses and lifetime of TBCs. Modeling has been shown as an effective tool to understand the effect of interface roughness on induced stresses. In previous work done by our research group, it was observed that APS bondcoats performed better than the bondcoats sprayed with High Velocity Oxy-Fuel (HVOF) process which is contrary to the present literature data. The objective of this work was to understand this observed difference in lifetime with the help of finite element modeling by using real surface topographies. Different TGO layer thicknesses were evaluated. The modeling results were also compared with existing theories established on simplified sinusoidal profiles published in earlier works. It was shown that modeling can be used as an effective tool to understand the stress behavior in TBCs with different roughness profiles.

  • 63.
    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.

  • 64.
    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.

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  • 65.
    Hattinger, Monika
    et al.
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Christiernin-Gustafsson, Linn
    University West, School of Business, Economics and IT, Division of Computer Engineering.
    Eriksson, Kristina M.
    University West, Department of Engineering Science, Division of Production Engineering. University West, Department of Engineering Science, Division of Production System.
    Digitizing work: Organizational Work-Integrated Learning through Technology Mediated Courses in Manufacturing Industry2013In: 18th WACE World Conference on Cooperative & Work-Integrated Education: WIL-POWER: FUELING THE FUTURE WORKFORCE, WACE , 2013, p. 1-12Conference paper (Other academic)
    Abstract [en]

    The manufacturing industry is continuously facing global competition and customer demands which impose the need to knowledge development to manage changes and long-term business goals. Continuous and lifelong learning is often seen as processes that support competence development and learning integrated within work. In this paper we focus on processes of learning within the manufacturing industry and how learning initiatives as technology mediated courses (TMC) can support learning from the workplace learning needs. Is learning initiatives integrated in work considered as means for strategic business goals? Can TMC be an important learning tool for support of knowledge creation? The study is performed through interviews with production managers and human resource managers with eight manufacturing industries in the western part of Sweden. Through the study we try to understand what knowledge the industry needs to evolve and achieve effective production. We also study the readiness for technology mediated learning. Early results show that the industries have interest in learning initiatives such as TMC and are willing to co-produce knowledge together with universities. We present a matrix model that interlinks business goals and the industries current use of technology mediated learning tools. However, the experience of using tools such as web conference systems and learning management systems for learning initiatives is diversified.

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    Digitizing work
  • 66.
    Hattinger, Monika
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Hellsten, Jan-Olof
    Lundh Snis, Ulrika
    University West, Department of Economics and IT, Division of Computer Science and Informatics.
    Lärcentrum - perspektiv och möjligheter: analys och praktik2007Report (Other academic)
  • 67.
    Heralic, Almir
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Charles, Corinne
    University West, Department of Engineering Science, Division of Production Engineering. University West, Department of Engineering Science, Division of Welding Technology.
    Dzevad, Imamovic
    Volvo Aero Coorporation.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    Dep of signal and systems, Chalmers.
    Towards stable high-speed metal-wire deposition, Part I: Parameter studyIn: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387Article in journal (Refereed)
  • 68.
    Heralic, Almir
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Christiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Production Engineering.
    Ottosson, Mattias
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Lennartson, Bengt
    Chalmers.
    Control Design for Automation of Robotized Laser Metal-Wire Deposition2008In: Proceedings of the 17th IFAC World Congress, International Federation of Automatic Control , 2008, p. 14785-14791Conference paper (Other academic)
    Abstract [en]

    In this paper a novel approach towards automation of robotized laser metal-wire deposition (RLMwD) is described. The RLMwD technique is being developed at University West in cooperation with Swedish industry for solid freeform fabrication of fully dense metal structures. The process utilizes robotized fibre laser welding and metal wire filler material, together with a layered manufacturing method, to create metal structures directly from a CAD drawing. The RLMwD process can also be used for repair or modification of existing components. This paper faces the challenge of designing a control system for maintaining stable process variables, such as a constant layer height and a stable component temperature, during the entire manufacturing process. Several problems are identified and discussed in the paper, e.g. the difficulty of obtaining the bead height in the weld pool environment. The case study is a repair application for stamping tools, where worn out trim edges are to be repaired. Issues regarding the control design, system identification, and the practical implementation of this application are discussed.

  • 69.
    Heralic, Almir
    et al.
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Ottosson, Mattias
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Hurtig, Kjell
    University West, Department of Engineering Science, Division of Production Engineering.
    Kristiansson, Anna-Karin
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    Visual feed-back for operator interaction in robotized laser metal deposition2008In: Proceedings of the 22nd International Conference on Surface Modification Technologies SMT22: Held at University West, Trollhättan, Sweden September 22-24, 2008 / [ed] T.S. Sudarshan & Per Nylen, 2008, p. 297-304Conference paper (Other academic)
  • 70.
    Hosseini, S.B.
    et al.
    Chalmers University of Technology, Department of Materials and Manufacturing Technology.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Production Engineering. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Johansson, S
    Lektronik, Ing.f:a, 424 49 Angered, Sweden .
    Klement, Uta
    Chalmers University of Technology, Department of Materials and Manufacturing Technology.
    Kaminski, J
    Chalmers University of Technology, Department of Materials and Manufacturing Technology.
    Ryttberg, K.
    AB SKF, 415 50 Gothenburg.
    Cutting temperatures during hard turning: Measurements and effects on white layer formation in AISI 521002014In: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 214, no 6, p. 1293-1300Article in journal (Refereed)
    Abstract [en]

    This paper concerns the temperature evolution during white layer formation induced by hard turning of martensitic and bainitic hardened AISI 52100 steel, as well as the effects of cutting temperatures and surface cooling rates on the microstructure and properties of the induced white layers. The cutting temperatures were measured using a high speed two-colour pyrometer, equipped with an optical fibre allowing for temperature measurements at the cutting edge. Depending on the machining conditions, white layers were shown to have formed both above and well below the parent austenitic transformation temperature, Ac1, of about 750 C. Thus at least two different mechanisms, phase transformation above the Ac1 (thermally) and severe plastic deformation below the Ac1 (mechanically), have been active during white layer formation. In the case of the predominantly thermally induced white layers, the cutting temperatures were above 900 C, while for the predominantly mechanically induced white layers the cutting temperatures were approximately 550 C. The surface cooling rates during hard turning were shown to be as high as 104-105 C/s for cutting speeds between 30 and 260 m/min independent of whether the studied microstructure was martensitic or bainitic. Adding the results from the cutting temperature measurements to previous results on the retained austenite contents and residual stresses of the white layers, it can be summarised that thermally induced white layers contain significantly higher amounts of retained austenite compared to the unaffected material and display high tensile residual stresses. On the contrary, in the case of white layers formed mainly due to severe plastic deformation, no retained austenite could be measured and the surface and subsurface residual stresses were compressive. © 2014 Elsevier B.V.

  • 71.
    Hosseini, Seyed B.
    et al.
    Chalmers University of Technology, Department of Materials and Manufacturing Technology.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Production Engineering. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Johansson, S
    Lektronik, Ing.f:a, 424 49 Angered.
    Klement, Uta
    Chalmers University of Technology, Department of Materials and Manufacturing Technology.
    Kaminski, J
    Chalmers University of Technology, Department of Materials and Manufacturing Technology.
    Ryttberg, K.
    AB SKF, 415 50 Gothenburg.
    A Methodology for Temperature Correction When Using Two-Color Pyrometers: Compensation for Surface Topography and Material2014In: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 54, no 3, p. 369-377Article in journal (Refereed)
    Abstract [en]

    In this investigation, the applicability of the two-color pyrometer technique for temperature measurements in dry hard turning of AISI 52100 steel was studied, where both machined surfaces as well as cutting tools were considered. The impacts of differing hard turned surface topography on the two-color pyrometer readings was studied by conducting temperature measurements on reference samples created using cutting tools with different degrees of tool flank wear. In order to conduct measurements in a controlled environment, a specially designed furnace was developed in which the samples were heated step-wise up to 1,000 °C in a protective atmosphere. At each testing temperature, the temperatures measured by the two-color pyrometer were compared with temperatures recorded by thermocouples. For all materials and surfaces as studied here, the two-color pyrometer generally recorded significantly lower temperatures than the thermocouples; for the hard turned surfaces, depending on the surface topography, the temperatures were as much as 20 % lower and for the CBN cutting tools, 13 % lower. To be able to use the two-color pyrometer technique for temperature measurements in hard turning of AISI 52100 steel, a linear approximation function was determined resulting in three unique equations, one for each of the studied materials and surfaces. By using the developed approximation function, the measured cutting temperatures can be adjusted to compensate for differing materials or surface topographies for comparable machining conditions. Even though the proposed equations are unique for the hard turning conditions as studied here, the proposed methodology can be applied to determine the temperature compensation required for other surface topographies, as well as other materials. © 2013 Society for Experimental Mechanics.

  • 72.
    Hulling, Ulf
    University West, Department of Engineering Science, Division of Production Engineering.
    Temperaturmätning i skärande bearbetning2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Denna rapport är resultatet av ett examensarbete omfattande 15 hp på C-nivå utfört vid Högskolan Väst. Arbetets första del bestod av en litteraturstudie och undersökning av befintliga temperaturmätningssystem som används i skärande bearbetning. Arbetets andra del bestod av att rekommendera temperaturmätningssystem och skapa en implementeringsplan för det rekommenderade systemet i utrustning på Produktions Tekniskt Center (PTC) i Trollhättan.

    Sex stycken olika tekniker för att mäta temperatur har undersökts med avseende på lämplighet för skärande bearbetning. Varje teknik presenteras med sammanfattande tabell med egenskaper samt för- och nackdelar.

    En teknik (pyrometri via optisk fiber) har valts ut för PTC och för den finns två tekniska specifikationer. En specifikation för ett system som kan anses vara kommersiellt tillgängligt (om en i mycket liten skala, 4-5 installationer i världen). En specifikation är framtagen baserat på forskningsresultat redovisat av prof. Ueda vid Kanazawa University men anpassad för att vara generell.

    För dessa system finns en implementeringsplan framtagen för att anpassa systemet och utrustning för att fungera vid PTC.

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  • 73.
    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.

  • 74. Håkansson, Johan
    et al.
    Skoog, Emil
    Eriksson K. M., Kristina M
    University West, Department of Engineering Science, Division of Production Engineering.
    A review of assembly line balancing and sequencing including line layouts2008In: Proceedings of PLANs forsknings- och tillämpningskonferens, 2008Conference paper (Refereed)
    Abstract [en]

    This paper comprises a literature review focused on mixed-model assembly line balancing and sequencing problems, including different line layouts. The study was undertaken in collaboration with a company to assist in mapping current state of the art. Balancing problems affect businesses long-term strategic decisions and are complex problems with regard to installation and rebalancing of assembly lines. Sequencing concerns decisions of short-term problem. Sequencing approaches include: level scheduling, mixed-model sequencing and car sequencing. Level scheduling constructs a sequence of variants to create efficient deliveries supported by the just-in-time concept, whereas both car- and mixed-model sequencing aim to minimise violations of a work station’s capacity through constructing a sequence, which alternates variants with high and low work intensity. Five layouts were considered: single-, mixed-model-, multi-model-, two-sided- and u-shaped assembly lines. These layouts were evaluated on the basis of the manufactured product(s), size and space at the production plant, economic resources, number of required operators and machinery. Following a thorough investigation of the literature, a substantial gap between academic discussions and real world practical applications was identified. The aim of forthcoming work is therefore to put this theory into practice.

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  • 75.
    Jiang, Janna
    University West, Department of Engineering Science, Division of Production Engineering.
    Modelling of mechanical properties of MAX-phase materials2009Licentiate thesis, comprehensive summary (Other academic)
  • 76.
    Jiang, Janna
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Fasth, Angelica
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylen, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Choi, W.B.
    Center for Thermal Spray Research, Stony Brook, NY, USA.
    Microindentation and Inverse Analysis to Characterize Elastic-Plastic Properties for Thermal Sprayed Ti2AlC and NiCoCrAlY2009In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 18, no 2, p. 194-200Article in journal (Refereed)
    Abstract [en]

    Elastic-plastic material properties for HVOF sprayed Ti2AlC (sprayed with Maxthal 211 powder) and plasma sprayed NiCoCrAlY coatings were investigated using modeling and experimental Berkovich microindentation. Optical microstructure evaluations were also performed. The theories of Hertz, Oliver and Pharr were combined with finite element analysis for extracting the material properties. Empirically based material models for both thermal sprayed Ti2AlC and NiCoCrAlY coatings are proposed.

  • 77.
    Jiang, Janna
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Fasth, Angelica
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Choi, W. B.
    Center for Thermal Spray Research, Stony Brook, NY, United States.
    Microindentation and inverse analysis to characterize elastic-plastic properties for thermal sprayed Ti2AlC and NiCoCrAlY2009In: Surface Modification Technologies XXII: Proceedings of the 22nd International Conference on Surface Modification Technologies SMT22 / [ed] T.S. Sudarshan & Per Nylen, VALAR Docs , 2009, Vol. 18, no 2, p. 177-186Conference paper (Refereed)
  • 78.
    Jiang, Janna
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Numerical modelling of the compression behaviour of single-crystalline MAX-phase materials2010In: Advanced materials research, ISSN 1022-6680, Vol. 89-91, p. 262-267Article in journal (Refereed)
    Abstract [en]

    In this article a numerical model to describe the mechanical behaviour of nanophased singlecrystalline Ti3SiC2 is proposed. The approach is a two dimensional finite element periodic unit cell consisting of an elastic matrix interlayered with shear deformable slip planes which obey the Hill's yield criterion. The periodic unit cell is used to predict compression material behaviour of Ti3SiC2 crystals with arbitrary slip plane orientations. Stress strain relationships are derived for Ti 3SiC2, and the effect of slip plane volume fraction as well as orientation of the slip planes are investigated. The two main deformation mechanisms of the material namely; ordinary slip and so called kinking are considered in the study.

  • 79.
    Jiang, Janna
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Object-oriented finite element analysis to simulate microindentation of thermal sprayed MAX-phase coatings2009In: Proceedings - 2009 International Conference on Computer Modeling and Simulation, ICCMS 2009, 2009, p. 337-341Conference paper (Other (popular science, discussion, etc.))
  • 80.
    Karlsson, Leif
    et al.
    University West, Department of Engineering Science, Divison of Natural Sciences, Surveying and Mechanical Engineering.
    Hurtig, Kjell
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering.
    Influence of dilution on properties of high strength steel weld metals2014In: Biuletyn Instytutu Spawalnictwa W Gliwicach: Rocznik 58, 2014, p. 65-71Conference paper (Refereed)
  • 81.
    Karlsson, Leif
    et al.
    University West, Department of Engineering Science, Divison of Natural Sciences, Surveying and Mechanical Engineering.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering.
    Hurtig, Kjell
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Efficient welding of high strength steel2014In: Proceedings of the 6th International Swedish Production Symposium 2014 / [ed] Stahre, Johan, Johansson, Björn & Björkman, Mats, 2014, p. 1-8Conference paper (Refereed)
    Abstract [en]

     Producing welds with properties matching those of the steel is a challenge at high strength levels. The present study investigated how cooling rates and dilution affects strength and toughness when welding steels with yield strengths of 777 MPa and 1193 MPa. Overmatching weld metal strength was achieved for the less strong steel and weld strengths >1000 MPa were recorded for the stronger steel. Fracture in transverse tensile testing was always located in base material or HAZ. Low dilution, rapid cooling and single pass welding contributed to higher strength. Impact toughness was higher for lower strength and low dilution.

  • 82.
    Keyvani, Ali
    et al.
    University West, Department of Engineering Science, Division of Production Engineering. University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Danielsson, Fredrik
    University West, Department of Engineering Science, Division of Electrical and Automation Engineering.
    A Virtual Manufacturing Approach for Integrating Fixture Design with Process Planning2009In: Proceedings of the sixth CIRP-sponsored International Conference on Digital Enterprise Technology: 14-16 dec, HongKong, 2009, p. 483-496Conference paper (Other academic)
    Abstract [en]

    Computer Aided Process Planning has received more attention recently due to considerable progress in the aspects of both technology and theory. Beside the traditional trends and efforts to integrate the product design and process planning activities usually referred to as concurrent engineering, virtual manufacturing tools have opened new horizons to this domain. This paper describes how to combine an existing modular fixture design with process planning and simulation tools. The proposed concurrent architecture consists of a functional model and an operational workflow for the design of modular fixtures within the process-planning phase. Two different paradigms, the Variant and the Generative, are discussed in relation to the proposed architecture. Fixtures for Body in White lines are a crucial design problem in the automotive industry. Therefore, the proposed architecture has been tested and investigated in such an environment.

  • 83.
    Keyvani, Ali
    et al.
    University West, Department of Engineering Science, Division of Natural Sciences and Electrical and Surveying Engineering. University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Lämkull, Dan
    Volvo Car Corporation, Gothenburg.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Production Engineering.
    Örtengren, Roland
    Chalmers University.
    Using methods-time measurement to connect digital humans and motion databases2013In: Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349, Vol. 8026, no Part 2, p. 343-352Article in journal (Refereed)
    Abstract [en]

    To simulate human motions in DHM tools, using techniques which are based on real human data is one promising solution. We have presented a solution in this study to connect motion databases with DHM tools. We have showed that using a motion database with MTM-based annotations is a promising way in order to synthesize natural looking motions. A platform consists of a Motion Database, a Motion Generator, and a DHM tool was introduced and tested. The results showed successful application of the presented platform in the designed test case. © 2013 Springer-Verlag.

  • 84.
    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.

  • 85.
    Li, Peigang
    University West, Department of Engineering Science, Division of Mechanical Engineering. University West, Department of Engineering Science, Division of Production Engineering.
    Cold lap formation in Gas Metal Arc Welding of steel: An experimental study of micro-lack of fusion defects2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Cold laps are defined as micro-lack of fusion defects at the weld toe more or less parallel to the surface of the parent plate. These defects are known to negatively influence the fatigue properties of weldments. Previous studies suggest that cold lap formation can not be avoided completely in Gas Metal Arc Welding (GMAW). Therefore, a better understanding of formation mechanisms is imperative to be able to minimize the number and size of these defects. The main objective of this work has been to provide a more comprehensive understanding of cold laps, including categorising, characterisation and defining the most significant factors for formation. GMAW was used to produce welds that were investigated by metallographic methods using light optical microscopy, scanning electron microscopy and energy dispersive spectrometry. A novel classification of cold laps was introduced and three types of cold laps were identified: spatter cold laps, overlap cold laps and spatter-overlap cold laps. It was shown that cold laps are partially or fully filled by oxides. The most common oxides are manganese silicon oxides which were concluded to be formed primarily by oxidation of droplets. The presence of oxides was found to significantly increase the tendency to form spatter cold laps as well as overlap cold laps. Particularly for overlap cold laps, it was found that the depth (in transverse direction of weld) is reduced when welding in a non-oxidising environment. Welding on blasted surfaces increased the cold lap formation by entrapment of gas. The droplet and base metal temperatures were also found to be significant factors in cold lap formation. For overlap cold laps the occurrence frequency decreased with increased preheating temperature of the base metal. Mechanisms of overflowing resulting in overlap cold laps were discussed based on an extensive literature review. Several phenomena are believed to contribute to overflow including Rayleigh instability, the balance of forces, transfer of lateral momentum by droplets and an outward Marangoni fluid flow of the weld pool.

    The present studies suggest that cold lap formation can be suppressed by ensuring that the welding process (arc) is as stable as possible and by welding on a preheated work piece in a non-oxidising environment.

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  • 86.
    Li, Peigang
    University West, Department of Engineering Science, Division of Production Engineering.
    Experimental study on cold lap formation in tandem gas metal arc welding2011Licentiate thesis, comprehensive summary (Other academic)
  • 87.
    Li, Peigang
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Klement, Uta
    University West, Department of Engineering Science.
    Characterization of Cold Lap Defects in Tandem Arc MAG Welding2010In: Proceedings of the International Conference on Advances in Welding Science & Technology for Construction, Energy & Transportation AWST-2010: Istanbul, Turkey, 12-15 July, 2010, 2010, p. 303-311Conference paper (Refereed)
  • 88.
    Li, Peigang
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Factors influencing fusion of spatter to the base metal during tandem GMAW2012In: Proceedings of The 5th International Swedish Production Symposium: 6th-8th of November 2012 Linköping, Sweden / [ed] Mats Björkman, Linköping, Sweden, 2012, p. 233-239Conference paper (Refereed)
    Abstract [en]

    Tandem gas metal arc welding (tandem GMAW) is, as a high productivity welding method of manufacturing process, utilized broadly in modern Swedish industry. Spatter is more or less an inevitable flaw in GMAW, especially for the high efficiency processes. Recently, spatter was found as a potential source of cold laps, which negatively influences fatigue life. The main objectives of this paper are to investigate the spatter/base metal interface and identify the primary factors for formation of cold laps.

    Tandem GMAW was performed in a sealed chamber filled with either pure argon or pure dioxide. Cross sections of spatter and base metal were prepared and evaluated by Light optical microscopy and Scanning Electron Microscopy (SEM) with an attached Energy Dispersive Spectroscope (EDS).

    Mn-Si oxides were found to enhance the lack of fusion occurrence in the spatter/base metal. The oxide of Mn and Si mostly came from oxidation of the droplets in the welding process. Spatter diameter and spatter distance was evaluated with respect to lack of fusion in spatter/base metal interface for welds using pure Ar shielding gas. From this it was concluded that temperature is another important factor for lack of fusion formation in the spatter/base metal interface.

  • 89.
    Li, Peigang
    et al.
    University West, Department of Engineering Science, Division of Production Engineering.
    Svensson, Lars-Erik
    University West, Department of Engineering Science, Division of Production Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Factors influencing fusion on spatter to the base metal during tandem GMAW weldingIn: Article in journal (Refereed)
  • 90.
    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 Mechanical Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    Influence of oxides on cold lap formation in tandem GMAW2012In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 17, no 8, p. 643-648Article in journal (Refereed)
    Abstract [en]

    The connection between the formation of cold laps and the presence of Mn‐Si oxides was studied. The underlying purpose is to understand the fundamental mechanisms of cold lap formation and to avoid it. Tandem gas metal arc welding (GMAW) was used to produce welded specimens in two different shielding gases (pure Ar and pure CO2) with base metal S355 MC (EN-10149-2) and wire G3Si1 (EN ISO 14341-A). Cross-sections of welds in the cold lap location were evaluated by light optical microscopy and scanning electron microscopy combined with energy dispersive spectroscopy. The results showed that the Mn‐Si oxides significantly enhanced cold laps formation, especially the overlap type cold lap formation. The Mn‐Si oxides originated from oxidation of the droplets. These oxides transfers to the surface of the weld pool at the weld toe, where they contributed to the formation of the cold laps.

  • 91.
    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.

  • 92.
    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.

  • 93.
    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 Mechanical Engineering.
    Markocsan, Nicolaie
    University West, Department of Technology, Mathematics and Computer Science, Division for Mechanical Engineering.
    Karlsson, Leif
    University West, Department of Engineering Science.
    Cold laps - micro-lack of fusion defects in steel arc welds: a reviewManuscript (preprint) (Other academic)
  • 94.
    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 Production Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Klement, Uta
    Department of Materials and manufacture, Chalmers University.
    Characterization of cold lap defects in tandem arc MAG welding2012In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 56, no 9/10, p. 20-25Article in journal (Refereed)
    Abstract [en]

    The objective of this investigation was to classify and characterize the small lack of fusion defects, called cold lap, located at the weld toe. Since the defects are very small (0.01–1.5 mm) and difficult to detect by NDT methods, a better understanding of the formation mechanism is required to be able to avoid their formation. The investigation consisted of two parts. Firstly, a study was made on the type and frequency of cold laps. Three types were identified, namely “spatter cold lap”, and “overlap cold lap” and “spatter-overlap cold lap”. No relation between type or frequency of cold laps and the welding parameters could be established. Secondly, the interface between spatter and the base material was investigated using optical and scanning electron microscopy, to better understand the cold lap formation mechanism. Manganese-silicate particles were found in the interface located in such a way that they may assist cold lap formation.

  • 95.
    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 Mechanical Engineering.
    Nylén, Per
    University West, Department of Engineering Science, Division of Production Engineering.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Production Engineering.
    Klement, Uta
    Chalmers University of Technology, Materials and Manufacturing Technology.
    Characterization of cold lap defects in tandem arc MAG welding2013In: Rivista Italiana della Saldatura, ISSN 0035-6794, Vol. 65, no 5, p. 761-769Article in journal (Refereed)
    Abstract [en]

    The objective of this investigation was to classify and characterize the small lack of fusion defects, called cold lap, located at the weld toe. Since the defects are very small (0.01-1.5 mm) and difficult to detect by NDT methods, a better understanding of the formation mechanism is required to be able to avoid their formation. The investigation consisted of two parts. Firstly, a study was made on the type and frequency of cold laps. Three types were identified, namely "spatter cold lap", and "overlap cold lap" and "spatter-overlap cold lap". No relation between type or frequency of cold laps and the welding parameters could be established. Secondly, the interface between spatter and the base material was investigated using optical and scanning electron microscopy, to better understand the cold lap formation mechanism. Manganese-silicate particles were found in the interface located in such a way that they may assist cold lap formation.

  • 96.
    Lindgren, Lars-Erik
    et al.
    Luleå Technology University.
    Babu, Bijish
    Luleå Technology University.
    Charles, Corinne
    University West, Department of Engineering Science, Division of Production Engineering.
    Wedberg, Dan
    Luleå Technology University.
    Simulation of manufacturing chains and use of coupled microstructure and constitutive models2010In: Finite Plasticity and Visco-plasticity of Conventional and Emerging Materials / [ed] Aktar S Khan, Babak Farrokh,, Fulton, Maryland, USA,: NEAT PRESS , 2010, p. 4 s.-Conference paper (Refereed)
  • 97.
    Liskevych, Olga
    et al.
    Center for Research and Development of Welding Processes of Federal University of Uberlandia (Laprosolda), Brazil.
    Scotti, Americo
    University West, Department of Engineering Science, Division of Production Engineering.
    Influence of the CO2 Content on Operational Performance of Short-Circuit GMAW2015In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 59, no 2, p. 217-224Article in journal (Refereed)
    Abstract [en]

    CO2 blended with Ar is the most common shielding gas used for short-circuit GMAW. There has been some technical knowledge devised from the process application over the years (personal opinion and results from practice) on the selection of the gas blend composition. However, there is still lack of more scientific data to explain the performance of the mixtures. This paper presents a systematic study of the influence that CO2 content in mixture with Argon has on the operational performance of the short-circuit GMAW. The objective of this study was to describe, to quantify and to explain the alterations in the metal transfer behavior, spatter generation, weld bead geometry and bead finish due to the different CO2 contents in the shielding gas. Carbon steel plates were welded in adequate parametric conditions for each CO2+Ar shielding gas composition (CO2 ranging from 2% to 100%). These parametric conditions were found by applying a metal transfer regularity index over welds carried out at different voltage settings for each gas blend. A target of 130 A was applied as base for comparison. Laser shadowgraphy with high speed filming and current and voltage oscillograms were used as analysis tools. The results showed (and confirmed) that the increase of the CO2 content deteriorates metal transfer regularity, leading to excessive spatter generation and uneven bead appearance, but increases the penetration and the fusion area of the weld beads and improves bead convexity. In general, the CO2 content should neither be lower than 10% (unless for thin plates) nor higher than 30%.

  • 98.
    List, A
    et al.
    Helmut Schmidt University, University of the Federal Armed Forces, Hamburg.
    Lyphout, Christophe
    University West, Department of Engineering Science, Division of Production Engineering.
    Villa, M
    Helmut Schmidt University, University of the Federal Armed Forces, Hamburg.
    Gärtner, F
    Helmut Schmidt University, University of the Federal Armed Forces, Hamburg.
    Klassen, T
    Helmut Schmidt University, University of the Federal Armed Forces, Hamburg.
    Mechanical properties of cold-sprayed Ti-6Al-4V coatings2013In: Proceedings of the International Thermal Spray Conference, ASM International, 2013, p. 155-160Conference paper (Refereed)
    Abstract [en]

    Titanium and titanium alloys are of great interest in aerospace and medical industries. Especially, Ti-6Al-4V alloys show a unique combination of high mechanical strength, low density and an outstanding corrosion resistance. However, particularly the high strength restricts industrial processing procedures. Thus, there are increasing demands for powder metallurgical process routes. For pure titanium, cold spraying already proved to be a promising alternative for manufacturing semi-finished products, mainly due to the use of high process gas temperatures and pressures. Nevertheless, due to the higher material strength, the production of Ti-6Al-4V coatings by cold spraying is still challenging, even under higher process parameters. The present study deals with the production and characterization of Ti-6Al-4V coatings produced by cold spraying. All experiments were performed using nitrogen as process gas. By a systematic variation of the spray parameters up to a process gas temperature of 1000°C and a process gas pressure of 5 MPa, the coatings could be tuned for optimum mechanical properties. In addition, attainable coating properties are described in terms of a newly introduced coating quality parameter η, namely the ratio of the particle velocity to the critical velocity, to reveal the most significant influences on coating performance and to give hints for further optimization.

  • 99.
    Lorentzon, John
    et al.
    University West, Department of Engineering Science.
    Järvstråt, Niklas
    University West, Department of Engineering Science, Division of Production Engineering.
    Modelling tool wear in cemented-carbide machining alloy 7182008In: International journal of machine tools & manufacture, ISSN 0890-6955, E-ISSN 1879-2170, Vol. 48, no 10, p. 1072-1080Article in journal (Refereed)
  • 100.
    Lorentzon, John
    et al.
    University West, School of Business, Economics and IT, Division of Business Administration. University West, Department of Engineering Science, Division of Production Engineering.
    Järvstråt, Niklas
    University West, Department of Engineering Science, Division of Production Engineering.
    Josefson, B. L.
    Chalmers University of Technology, Department of Applied Mechanics.
    Modelling chip formation of alloy 7182009In: Journal of Materials Processing Technology, Vol. 209, no 10, p. 4645-4653Article in journal (Refereed)
1234 51 - 100 of 159
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