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  • 1.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Weldability of Ni-based Superalloys2014In: 8th International Symposium on Superalloy 718 and Derivatives: Conference Proceedings / [ed] Ott, E., Banik, A., Andersson, J., Dempster, I., Gabb, T., Groh, J., Heck, K., Helmink, R., Liu, X. & Wusatowska-Sarnek, A., Hoboken, NJ, USA: John Wiley & Sons, 2014, p. 249-262Conference paper (Refereed)
  • 2.
    Andersson, Joel
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Jacobsson, J.
    Brederholm, A.
    Hänninen, H.
    Improved understanding of Varestraint Testing: Nickel-based superalloys2016In: Cracking Phenomena in Welds IV / [ed] Boellinghaus, T., Lippold, J. C. and Cross, C. E., Springer Publishing Company, 2016Conference paper (Refereed)
    Abstract [en]

    Information about the book:

    This is the fourth volume in the well-established series of compendiums devoted to the subject of weld hot cracking. It contains the papers presented at the 4th International Cracking Workshop held in Berlin in April 2014. In the context of this workshop, the term “cracking” refers to hot cracking in the classical and previous sense, but also to cold cracking, stress-corrosion cracking and elevated temp. solid-state cracking.  A variety of different cracking subjects are discussed, including test standards, crack prediction, weldability determination, crack mitigation, stress states, numerical modelling, and cracking mechanisms.  Likewise, many different alloys were investigated such as aluminum alloys, copper-aluminum dissimilar metal, austenitic stainless steel, nickel base alloys, duplex stainless steel, creep resistant steel, and high strength steel.

  • 3.
    Andersson, Joel
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Jacobsson, J.
    Lundin, C.
    A Historical perspective on Varestraint testing and the importance of testing parameters2016In: Cracking Phenomena in Welds IV / [ed] Boellinghaus, T., Lippold, J. C. and Cross, C. E., Springer Publishing Company, 2016Conference paper (Refereed)
  • 4.
    Andersson, Joel
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Raza, Shahzad
    Department of Materials Science and Engineering, Royal Institute of Technology.
    Eliasson, Anders
    KTH, Department of Materials Science and Engineering, Royal Institute of Technology.
    Surreddi, Kumar Babu
    Chalmers University of Technology, Department of Materials and Manufacturing Technology.
    Solidification of Alloy 718, ATI 718Plus and Waspaloy2014In: 8th International Symposium on Superalloy 718 and Derivatives: Conference Proceedings / [ed] Ott, E., Banik, A., Andersson, J., Dempster, I., Gabb, T., Groh, J., Heck, K., Helmink, R., Liu, X. & Wusatowska-Sarnek, A, Hoboken, NJ, USA: John Wiley & Sons, 2014, p. 181-192Conference paper (Refereed)
  • 5.
    Andersson, Joel
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes. Department of Materials Technology, Volvo Aero Corporation, Trollha¨ttan, Sweden and Chalmers University of Technology, Gothenburg, Sweden.
    Sjöberg, G.
    Department of Materials Technology, Volvo Aero Corporation, Trollha¨ttan, Sweden and Chalmers University of Technology, Gothenburg, Sweden.
    Repair welding of wrought superalloys: Alloy 718, Allvac 718Plus and Waspaloy2012In: Science and Technology of Welding and Joining, ISSN 1362-1718, Vol. 17, no 1, p. 49-59Article in journal (Refereed)
    Abstract [en]

    The ability to weld repair three precipitation hardening superalloys, i.e. Alloy 718, Allvac 718Plus and Waspaloy, with gas tungsten arc welding, is compared in this study. Four different solution heat treatment conditions for each material were examined: Alloy 718 and Allvac 718Plus heat treated at 954uC–1 h, 982uC–1 h, 954uC–15 h and 1020uC–1 h and Waspaloy for 4 h at 996uC, 1010uC, 1040uC and at 1080uC. By metallography, the total number of cracks was evaluated in both the heat affected zone and the fusion zone, which made it possible to consistently rate the repair weldability of these three materials. Alloy 718 was significantly the best one, with Allvac 718Plus slightly better than Waspaloy. As expected, the solution heat treatment conditions only affected the heat affected zone cracking behaviour.

  • 6.
    Andersson, Joel
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Sjöberg, G.
    Brederholm, A.
    Hänninen, H.
    Solidification Cracking of Alloy Allvac 718Plus and Alloy 718 at Transvarestraint Testing2010In: EPD Congress 2008: Proceedings of Sessions and Symposia Sponsored by the Extraction and Processing Division (EPD) / [ed] Stanley M. Howard, Wiley-Blackwell, 2010, p. 157-169Conference paper (Refereed)
  • 7.
    Andersson, Joel
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Sjöberg, G.
    Chaturvedi, M.
    Hot Ductility Study of Haynes 282 Superalloy2010In: Superalloy 718 and Derivatives: Proceedings of the 7th International Symposium on Superalloy 718 and Derivatives / [ed] E. A. Ott, J. R. Groh, A. Banik, I. Dempster, T. P. Gabb, R. Helmink, X. Liu, A. Mitchell, G. P. Sjöberg and A. Wusatowska-Sarnek, The Minerals, Metals, and Materials Society, 2010, p. 539-554Conference paper (Refereed)
  • 8.
    Andersson, Joel
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Sjöberg, G.
    Hatami, S.
    Notch Sensitivity and Intergranular Crack Growth in the Allvac 718Plus Superalloy2007In: XVIII International Symposium on Air Breathing Engines (ISABE): Beijing, China, 2-7 September 2007, 2007, p. n.1293-Conference paper (Refereed)
  • 9.
    Andersson, Joel
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes. Volvo Aero Corporation, Trollhättan, Sweden och Chalmers University of Technology, Gothenburg, Sweden.
    Sjöberg, G.
    Volvo Aero Corporation, Trollhättan, Sweden och Chalmers University of Technology, Gothenburg, Sweden.
    Hänninen, H.
    Aalto University School of Science and Technology, Espoo, Finland.
    Metallurgical Response of Electron Beam Welded Allvac® 718Plus™2011In: Hot Cracking Phenomena in Welds III / [ed] Lippold, J., Böllinghaus, T. and Cross C. E., Springer Berlin/Heidelberg, 2011, p. 415-428Conference paper (Refereed)
    Abstract [en]

    Electron beam welding of forged Allvac 718Plus superalloy has been carried out without any visible cracks in weld cross-sections. Healed cracks in the heat affected zone were, however, seen in most cross-sections with the healing as well as the cracking believed to be due to the constitutional liquation of the δ-phase. The δ-phase undergoes constitutional liquation in the Heat Affected Zone (HAZ) and consequently decreases the ductility of the material and renders cracks in the HAZ but due to the large amount of eutectic liquid produced at the same time the healing of the opened cracks takes place.

  • 10.
    Andersson, Joel
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes. Volvo Aero Corporation, Materials Technology Department, Trollhättan, Sweden och Chalmers University of Technology, Department of Materials and Manufacturing Technology, Göteborg,Sweden.
    Sjöberg, G.
    Volvo Aero Corporation, Materials Technology Department, Trollhättan, Sweden och Chalmers University of Technology, Department of Materials and Manufacturing Technology, Göteborg, Sweden.
    Larsson, J.
    Chalmers University of Technology, Department of Materials and Manufacturing Technology, Göteborg,Sweden.
    Investigation of Homogenization and its Influence on the Repair Welding of Cast Allvac 718Plus(®)2010In: Superalloy 718 and Derivatives: Proceedings of the 7th International Symposium on Superalloy 718 and Derivatives / [ed] E. A. Ott, J. R. Groh, A. Banik, I. Dempster, T. P. Gabb, R. Helmink, X. Liu, A. Mitchell, G. P. Sjöberg, and A. Wusatowska-Sarnek, The Minerals, Metals, and Materials Society, 2010, p. 439-454Conference paper (Refereed)
  • 11.
    Andersson, Joel
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Sjöberg, G.
    Viskari, L.
    Brederholm, A.
    Hänninen, H.
    Knee, C.
    Hot Cracking of Allvac 718Plus, Alloy 718 and Waspaloy at Varestraint Testing2008In: 4th International Symposium on Aerospace Materials and Manufacturing Processes: Advances in Processing and Repair of Aerospace Materials 2008 / [ed] M. Jahazi, M. Elboujdaini and P. Patnaik, Montreal: Canadian Institute of Mining, Metallurgy and Petroleum, 2008, p. 401-413Conference paper (Refereed)
    Abstract [en]

    Varestraint testing together with DSC and SEM-EDX analyses have been performed as means of investigating the hot cracking susceptibility of Allvac 718Plus, alloy 718 and Waspaloy. The solidification sequences in Allvac 718Plus and alloy 718 were very similar to each other starting by an initial solidification of the gamma phase, gamma/MC reaction at around 1260°C and then finally ending the sequence by gamma/Laves eutectic reaction at around 1150°C. Waspaloy had the same solidification sequence, except no Laves phase formation takes place, and solidification started at a somewhat higher temperature as compared to alloy 718 and the solidification sequence ends by a gamma/MC reaction at around 1245°C. The total amount of hot cracking in Waspaloy was shown to be much less than that in alloy 718 and in Allvac 718Plus which is believed to be related to the presence of the Laves eutectic in the latter two alloys with corresponding larger solidification ranges. Hot cracking of 718Plus is slightly less than in 718.

  • 12.
    Andersson, Joel
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes. Department of Materials Technology, GKN Aerospace Engine Systems, Trollhättan, Sweden och Department of Materials and Manufacturing Technology, Chalmers University of Technology, Gothenburg, Sweden.
    Sjöberg, G.
    Department of Materials Technology, GKN Aerospace Engine Systems, Trollhättan, Sweden och Department of Materials and Manufacturing Technology, Chalmers University of Technology, Gothenburg, Sweden.
    Viskari, L.
    Department of Applied Physics, Chalmers University of Technology, Gothenburg, Sweden.
    Chaturvedi, M. C.
    Department of Mechanical and Industrial Engineering, University of Manitoba, Winnipeg, MB, Canada.
    Effect of Different Solution Heat Treatments on the Hot Ductility of Superalloys: Part 3 - Waspaloy2013In: Materials Science and Technology, ISSN 0267-0836, Vol. 29, no 1, p. 43-53Article in journal (Refereed)
    Abstract [en]

    The susceptibility to heat affected zone cracking of Waspaloy has been investigated in terms of its hot ductility, measured as the reduction of area (RA). Gleeble testing with on-heating as well as on-cooling test cycles was carried out to illuminate the influence of different 4 h solution heat treatments between 996 and 1080°C. A ductility maximum of between 80 and 90%RA was found at 1050–1100°C for all conditions in the on-heating tests. Although the different heat treatment conditions showed similar macrohardness, the particle size and distribution of the γ′ and M23C6 phases differed, which significantly affected the on-heating ductility in the lower temperature test region. The ductile to brittle transition was initiated at 1100°C in the on-heating testing with indications of grain boundary liquation at the higher test temperatures. Ductility recovery, as measured in the on-cooling tests from 1240°C, was very limited with <30%RA for all conditions and test temperatures except for the 1080°C/4 h treatment, which exhibited 60%RA at 980°C.

  • 13.
    Andersson, Joel
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes. Department of Materials Technology, Volvo Aero Corporation, Trollhättan, Sweden and Department of Materials and Manufacturing Technology, Chalmers University of Technology, Gothenburg, Sweden.
    Sjöberg, G.
    Department of Materials Technology, Volvo Aero Corporation, Trollhättan, Sweden and Department of Materials and Manufacturing Technology, Chalmers University of Technology, Gothenburg, Sweden.
    Viskari, L.
    Department of Applied Physics, Chalmers University of Technology, Gothenburg, Sweden.
    Chaturvedi, M.C.
    Department of Mechanical and Industrial Engineering, University of Manitoba, Winnipeg, MB, Canada.
    Effect of different solution heat treatments on hot ductility of superalloys: Part 2 – Allvac 718Plus2012In: Materials Science and Technology, ISSN 0267-0836, Vol. 28, no 6, p. 733-741Article in journal (Refereed)
    Abstract [en]

    The hot ductility of Allvac 718Plus for different solution heat treatments (954°C–15 h, 954°C–1 h, 982°C–1 h and 1050°C–3 h+954°C–1 h) has been investigated using Gleeble testing. Substantial variations in the microstructure among the heat treatments affected the Gleeble test hot ductility only to a very limited extent. Constitutional liquation of the NbC phase was found to be the main cause for the poor ductility at high testing temperatures in the on-heating cycle as well as at the lower temperatures on-cooling. Grain boundary δ phase was seen to assist the constitutional liquation of the NbC phase. Based on established evaluation criteria for Gleeble ductility testing, a ranked indicator for weldability is suggested.

  • 14.
    Andersson, Joel
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes. Department of Materials Technology at Volvo Aero Corporation, Trollhättan, and Chalmers University of Technology, Gothenburg, Sweden.
    Sjöberg, G.
    Department of Materials Technology at Volvo Aero Corporation, Trollhättan, and Chalmers University of Technology, Gothenburg, Sweden.
    Viskari, L.
    Department of Microscopy and Microanalysis at Chalmers University of Technology, 41296 Gothenburg, Sweden.
    Chaturvedi, M.C.
    Department of Mechanical and Industrial Engineering, University of Manitoba, Winnipeg, Manitoba, R3T 5V6 Canada.
    Effect of solution heat treatments on superalloys: Part 1 – alloy 7182012In: Materials Science and Technology, ISSN 0267-0836, Vol. 28, no 5, p. 609-619Article in journal (Refereed)
    Abstract [en]

    The hot ductility as measured by Gleeble testing of Alloy 718 at four different solution heat treatments (954°C/15 h, 954°C/1 h, 982°C/1 h and 1050°C/3 h+954°C/1 h) has been investigated. It is concluded that constitutional liquation of NbC assisted by δ phase takes place and deteriorates the ductility. Parameters established by analysing the ductility dependence on temperature indicate a reduced weldability of the material in the coarse grain size state (ASTM 3) while indicating an increased weldability when containing a large amount of δ phase due to a grain boundary pinning effect. The accumulation of trace elements during grain growth at the highest temperature is believed to be the cause for the observed reduced on-cooling ductility.

  • 15.
    Andersson, Joel
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Vikström, Fredrik
    GKN Aerospace Engine Systems.
    Pettersson, Bengt
    GKN Aerospace Engine Systems.
    HIP-Densification of Alloy 718 and ATI 718Plus2014In: 8th International Symposium on Superalloy 718 and Derivatives: Conference Proceedings / [ed] Ott, E., Banik, A., Andersson, J., Dempster, I., Gabb, T., Groh, J., Heck, K., Helmink, R., Liu, X. & Wusatowska-Sarnek, A., Hoboken, NJ, USA: John Wiley & Sons, 2014, p. 425-436Conference paper (Refereed)
  • 16.
    Atar, Mohammad
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Förstudie till fältbusslaboration för elkraftstillämpningar2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis describes how to develop a fieldbus lab. The lab will be part of the course Data communications with electric power applications (course code DML200) at University West. The goal and purpose of this lab will be to allow students learn how to set up, commission and troubleshoot equipment. In this context, the course also directed towards electric power technology and it is important for the Bachelor programme in electrical engineering with specialization in power electric because the course is included in the program.

    The work was aimed at developing suitable equipment which must include the appropriate number of protection relays and the necessary components for communication via ProfiBus such as PLC controllers, I/O-module, the Operation Panel. Different companies where asked about the prices of the components and a collection of quotations was made.

    The response from three out of five different companies indicated that ProfiBus is an old system. Everyone wondered why ProfiBus was chosen as a communications system over other system such as Ethernet with ModBus. According to these companies ProfiBus is an old communication system and it is expensive. It could save some money if the problem was solved with ethernet with ModBus because of the availability of the manufacturers. Finally the lab idea was illustrated with a wiring diagram.

  • 17.
    Augustsson, Svante
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    Gustavsson Christiernin, Linn
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Automation Systems.
    Human and robot interaction based on safety zones in a shared work environment2014In: HRI '14: Proceedings of the 2014 ACM/IEEE international conference on Human-robot interaction, New York: Association for Computing Machinery (ACM), 2014, p. 118-119Conference paper (Refereed)
    Abstract [en]

    In this paper, early work on how to implement flexible safety zones is presented. In the case study an industrial robot cell emulates the environment at a wall construction site, with a robot performing nailing routines. Tests are performed with humans entering the safety zones of a SafetyEye system. The zone violation is detected, and new warning zones initiated. The robot retracts but continues its work tasks with reduced speed and within a safe distance of the human operator. Interaction is achieved through simultaneous work on the same work piece and the warning zones can be initiated and adjusted in a flexible way.

  • 18.
    Augustsson, Svante
    et al.
    University West, Department of Engineering Science, Division of Automation Systems.
    Olsson, Jonas
    University West, Department of Engineering Science, Division of Manufacturing Processes. University West, Department of Engineering Science, Division of Subtractive and Additive Manufacturing.
    Gustavsson Christiernin, Linn
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Bolmsjö, Gunnar
    University West, Department of Engineering Science, Division of Automation and Computer Engineering.
    How to Transfer Information Between Collaborating Human Operators and Industrial Robots in an Assembly2014In: Proceedings the NordiCHI 2014: The 8th Nordic Conference on Human-Computer Interaction: Fun, Fast, Foundational, ACM Publications, 2014, p. 286-294Conference paper (Refereed)
    Abstract [en]

    Flexible human-robot industrial coproduction will be important in many small and middle-sized companies in the future. One of the major challenges in a flexible robot cell is how to transfer information between the human and the robot with help of existing and safety approved equipment. In this paper a case study will be presented where the first half focus on data transfer to the robot communicating the human's position and movements forcing the robot to respond to the triggers. The second half focuses on how to visualize information about the settings and assembly order to the human. The outcome was successful and flexible, efficient coproduction could be achieved but also a number of new challenges were found.

  • 19.
    Beaubert, Francois
    et al.
    Valenciennes University.
    Pálsson, Halldór
    University of Iceland.
    Lalot, Sylvain
    Valenciennes University.
    Choquet, Isabelle
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Bauduin, Hadrian
    Valenciennes University.
    Design of a device to induce swirling flow in pipes: A rational approach2015In: Comptes rendus. Mecanique, ISSN 1631-0721, E-ISSN 1873-7234, Vol. 343, no 1, p. 1-12Article in journal (Refereed)
    Abstract [en]

    In this study, a rational approach is proposed to design a device for inducing swirling flow in heat exchanger pipes, for improved efficiency in the laminar regime. First, 2D computational fluid dynamics results lead to select, among four profiles, the blade profile with the most favorable lift to drag ratio. Then, the fluid flow in the swirler made with the selected blade profile is simulated in 3D, for Reynolds numbers ranging from 50 to 1600. Based on the simulation results, an analytic approximation of the evolution of the tangential fluid velocity is proposed as a function of the Reynolds number.

  • 20.
    Beno, Tomas
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Repo, Jari
    University West, Department of Engineering Science, Division of Mechanical Engineering and Natural Sciences.
    Pejryd, Lars
    Örebro Universitet.
    The Use of Machine Tool Internal Encoders as Sensors in a Process Monitoring System2013In: International Journal of Automation Technology, ISSN 1881-7629, E-ISSN 1883-8022, Vol. 7, no 4, p. 410-417Article in journal (Refereed)
    Abstract [en]

    Tool wear in machining changes the geometry of the cutting edges, which affects the direction and amplitudes of the cutting force components and the dynamics in the machining process. These changes in the forces and dynamics are picked up by the internal encoders and thus can be used for monitoring of changes in process conditions. This paper presents an approach for the monitoring of a multi-tooth milling process. The method is based on the direct measurement of the output from the position encoders available in the machine tool and the application of advanced signal analysis methods.

    The paper investigates repeatability of the developed method and discusses how to implement this in a process monitoring and control system. The results of this work show that various signal features which are correlated with tool wear can be extracted from the first few oscillating components, representing the low-frequency components, of the machine axes velocity signatures. The responses from the position encoders exhibit good repeatability, especially short term repeatability while the long-term repeatability is more unreliable.

  • 21.
    Bonilla Hernández, Ana Esther
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Production Engineering.
    Repo, Jari
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Wretland, Anders
    GKN Aerospace Engine Systems AB, Trollhättan, Sweden.
    Analysis of Tool Utilization from Material Removal Rate Perspective2015In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 29, p. 109-113Article in journal (Refereed)
    Abstract [en]

    An end of life strategy algorithm has been used to study a CNC program to evaluate how the cutting inserts are used in terms of their full utilization. Utilized tool life (UTL) and remaining tool life (RTL) were used to evaluate if the insert has been used to its limits of expected tool life, or contributing to an accumulated tool waste. It is demonstrated that possible means to improvement exists to increase the material removal rate (MRR), thereby using the insert until its remaining tool life is as close to zero as possible. It was frequently found that inserts were used well below their maximum performance with respect to cutting velocity.

  • 22.
    Bonilla Hernández, Ana Esther
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Repo, Jari
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Wretland, Anders
    GKN Aerospace Engine Systems AB, Trollhättan, Sweden.
    Integrated optimization model for cutting data selection based on maximal MRR and tool utilization in continuous machining operations2016In: CIRP - Journal of Manufacturing Science and Technology, ISSN 1755-5817, E-ISSN 1878-0016, Vol. 13, p. 46-50Article in journal (Refereed)
    Abstract [en]

    The search for increased productivity can be interpreted as the increase of material removal rate (MRR). Namely, increase of feed, depth of cut and/or cutting speed. The increase of any of these three variables, will increase the tool wear rate; therefore decreasing its tool life according to the same tool life criteria. This paper proposes an integrated model for efficient selection of cutting data for maximal MRR and maximal tool utilization. The results show that, it is possible to obtain a limited range of cutting parameters from where the CAM Programmer can select the cutting data assuring both objectives.

  • 23.
    Bonilla Hernández, Ana Esther
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Repo, Jari
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Wretland, Anders
    GKN Aerospace Engine Systems AB, Trollhättan, Sweden.
    Streamlining the CAM programming process by Lean Principles within the aerospace industryManuscript (preprint) (Other academic)
  • 24.
    Chen, Y.
    et al.
    University of Manchester, School of Materials, Manchester, United Kingdom.
    Zhao, X.
    Shanghai Jiao Tong University, Shanghai Key Laboratory of Advanced High-Temperature Materials and Precision Forming, Shanghai, China .
    Dang, Y.
    University of Manchester, School of Materials, Manchester, United Kingdom.
    Xiao, Ping
    University of Manchester, School of Materials, Manchester, United Kingdom.
    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, Division of Production Engineering.
    Characterization and understanding of residual stresses in a NiCoCrAlY bond coat for thermal barrier coating application2015In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 94, p. 1-14Article in journal (Refereed)
    Abstract [en]

    The residual stresses in a NiCoCrAlY bond coat deposited on a Ni-base superalloy substrate after oxidation at 1150 °C were studied by X-ray diffraction using the sin2Ψ technique. The stresses were found to be tensile; they first increased and then decreased with oxidation time. High temperature stress measurement indicated that the stress developed and built up upon cooling, predominantly within the temperature range from 1150 °C to 600 °C. Microstructural examination suggested that, due to the limited penetration depth into the bond coat, the X-ray only probed the stress in a thin surface layer consisting of the single γ-phase formed through Al depletion during oxidation. Quantitative high temperature X-ray diffraction analysis revealed that, above 600 °C, the volume fraction of the β-phase in the bond coat increased with decreasing temperature. The mechanisms of stress generation in the bond coat were examined and are discussed based on the experiments designed to isolate the contribution of possible stress generation factors. It was found that the measured bond coat stresses were mainly induced by the volume change of the bond coat associated with the precipitation of the β-phase upon cooling.

  • 25.
    Choquet, Isabelle
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Johansson, J.
    Wigren, J.
    New powder port holder geometry to avoid lump formation in APS2005In: 17th international symposium on plasma chemistry (ISPC 17) :: Toronto, Canada, August 7th – 12th, 2005, 2005, p. OP7. 1-6Conference paper (Other academic)
    Abstract [en]

    A new geometry of the powder port ring holder used in atmospheric plasma spraying has recently been designed to avoid lump formation, and successfully tested for a set of process parameters associated with Ni-5Al powder used in production to form bond coat [1]. But with ZrO 2 powder used to made top coat, improvements were not enough satisfactory. Here, we investigate numerically the cause of the remaining defects, and further improve the ring geometry to prevent lump from forming in any part of the coating.

  • 26.
    Choquet, Isabelle
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Johansson, Jimmy
    Volvo Aero Corporation, Trollhättan.
    Wigren, Jan
    Volvo Aero Corporation, Trollhättan.
    Clogging and lump formation during atmospheric plasma spraying with powder injection downstream the plasma gun2007In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 16, no 4, p. 512-523Article in journal (Refereed)
    Abstract [en]

    This study aimed to numerically and experimentally investigate lump formation during atmospheric plasma spraying with powder injection downstream the plasma gun exit. A first set of investigations was focused on the location and orientation of the powder port injector. It turned out impossible to keep the coating quality while avoiding lumps by simply moving the powder injector. A new geometry of the powder port ring holder was designed and optimized to prevent nozzle clogging, and lump formation using a gas screen. This solution was successfully tested for applications with Ni-5wt.%Al and ZrO2-7wt.%Y2O3 powders used in production. The possible secondary effect of plasma jet shrouding by the gas screen, and its consequence on powder particles prior to impact was also studied.

  • 27.
    Choquet, Isabelle
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Nilsson, Håkan
    Chalmers University of Technology.
    Analysis of the Influence of the Composition of the Shielding Gas on Pressure Force and Heat Fluxes in Arc Welding2014In: Proceedings of The 6th International Swedish Production Symposium 2014 / [ed] Johan Stahre, Björn Johansson,Mats Björkman, 2014, p. 1-8Conference paper (Refereed)
    Abstract [en]

    A main problem raised by arc welding manufacturing is the determination ofthe optimal process parameters to ensure weld quality as well as resource efficient andsustainable production. To address this problem a better process understanding is required.In this study thermal magneto hydrodynamic modeling of a welding arc is used to reacha deeper insight into the influence of the composition of the shielding gas on the pressureforce and the heat fluxes to a workpiece. The model was implemented in the open sourcesimulation software OpenFOAM. Four different shielding gas mixtures combining argonand carbon dioxide were studied. When increasing the fraction of carbon dioxide the resultsshow a significant increase of the arc velocity and temperature with constriction of thetemperature field, a decrease of the pressure force and a significant increase of the heatfluxes on the base metal.

  • 28.
    Christiernin-Gustafsson, Linn
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Människor, Robotar och Maskiner2014In: Smart media, no November, p. 22-22Article in journal (Other (popular science, discussion, etc.))
  • 29.
    Clement, C.
    et al.
    National School of Engineers, University of Limoges, Limoges, 87280, France.
    Sadeghimeresht, Esmaeil
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Lyphout, Christophe
    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.
    Corrosion behavior of HVAF- and HVOF-sprayed high-chromium Fe-based coatings2015Conference paper (Refereed)
    Abstract [en]

    Fe-based coatings with three particular elemental compositions and two different powder particle size were prepared by high-velocity air fuel (HVAF) and high-velocity oxy fuel (HVOF) techniques. The corrosion behavior of which were comparatively studied in 3.5 wt.% NaCl solution. The results indicated that the coatings produced by HVAF process exhibited denser structure with lower porosity. Polarization and electrochemical impedance spectroscopy (EIS) tests indicated that the HVAF coatings provided better corrosion resistance than the HVOF coatings. The presence of defects was significant in HVOF coatings. The investigation illustrated that the corrosion paths initiated and grow through defects of the coating. Furthermore, adding Cr strongly improved the corrosion resistance of the coatings. The results confirmed that the cheap HVAF process could be a potential alternative to HVOF to fabricate Fe-based coatings for industrial applications.

  • 30.
    Coll Ferrari, Maria Teresa
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    On the evolution of tempering carbides in a modified H!# and a modified H11 when hardening at 1000°2013Conference paper (Refereed)
    Abstract [en]

    Hot- work tool steels require high austenitising temperature during hardening in order to yield the high tempering resistance that vanadium- rich carbides supply. Such grades, when offering high cleanness, are also used for plastic injection molding. The hardening temperature can then be lower, yielding a lower content of vanadium in the martensitic matrix and precipitating instead molybdenum-rich carbides, M2C- type, during tempering. M2C- type carbides are metastable and have high carbide/ matrix interface energy, which implies a greater driving force for coarsening than that in the MC- type. In this paper the carbide evolution in two hot- work grades hardened at 1000˚C, is studied after two and threetemperings. Type, size and distribution of tempering carbides were investigated with the help of TEM. Undissolved carbides were documented by SEM investigation and the microstructures classified by LOM. Hardness levels and Charpy V test results are also reported here.

  • 31.
    Coll Ferrari, Maria Teresa
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Andersson, J.
    Kvarnström, M.
    Influence of lowered austenitisation temperature during hardening on tempering resistance of modified H13 tool steel (Uddeholm Dievar)2013In: International Heat Treatment and Surface Engineering, ISSN 1749-5156, Vol. 7, no 3, p. 129-132Article in journal (Refereed)
    Abstract [en]

    The surface of large tools will be exposed to the hardening temperature for longer times than the core. This might in occasions, result in grain growth. In order to prevent this, it has become practice to lower the hardening temperature. This paper presents the effect of this practice on the precipitation of tempering carbides and the tempering resistance of Uddeholm Dievar. Composition of equilibrium austenite and the undissolved carbides at two different hardening temperatures were estimated by Thermo Calc simulations and the calculations predict that the balance between the amounts of molybdenum and vanadium in the austenite is shifted towards more molybdenum at the lower austenitising temperature. Since molybdenum stabilises M2C precipitates, it was predicted also that the tempering carbides would be almost only M2C in the sample with the lower austenitising temperature, whereas for the higher austenitising temperature, the subsequent tempering would yield a mixture of the much more stable MC together with M2C. Samples were hardened at the simulated temperatures and tempered. The existing carbides were investigated with help of SEM and TEM. The result shows that a lowered austenitisation temperature decreases the tempering resistance. However, the transmission electron microscopy reveals that both samples have the same mixture of tempering carbides, as the samples do not reach thermodynamical equilibrium during the holding time at the hardening temperature. The lower austenitising temperature gives less tempering carbides as less alloying elements are dissolved.

  • 32.
    Coll Ferrari, Maria Teresa
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Forsberg, Amanda
    Uddeholms AB.
    Andersson, Jörgen
    The Swedish School of Mining and Metallurgy.
    Mikula, Pavol
    Nuclear Physics Institute ASCR.
    Beran, Premysl
    Nuclear Physics Institute ASCR.
    Effect of Austenitising Temperature and Cooling Rate on Microstructure in a Hot-Work Tool Steel2014In: Proceedings of the 6th International Swedish Production Symposium / [ed] Stahre, Johan, Johansson, Björn & Björkman, Mats, 2014, p. 1-7Conference paper (Refereed)
    Abstract [en]

    The effects on microstructucture of austenitising temperature and cooling rate during hardening were studied for a hot-work tool steel. Transformation temperatures were determined by dilatometry, scanning electron microscopy was used to characterise the microstructure and both retained austenite contents and their lattice parameters were measured by neutron diffraction. For lower cooling rates, lower austenitising temperatures produce larger amounts of both retained austenite and bainite. Retained austenite in bainitic structures is higher in carbon than in martensitic structures. Consequently, lowering the austenitising temperature will affect microstructure and properties.

  • 33.
    Coll Ferrari, María Teresa
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Effect of austenitising temperature and cooling rate on microstructures of hot-work tool steels2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The average size of hot-work tools has gradually increased over the past years.This affects the effective temperature cycle tools experience during hardening,as large dimensions prevent uniform and rapid cooling, and thereby the resulting microstructures and properties. In order to avoid the formation of coarse structures or cracking during heat treatment it has become common practise to lower the austenitising temperature below that recommended by the steel manufacturer.In this work, therefore, the effects of austenitising at temperatures lower thancommonly recommended are investigated. Three 5% Cr hot-work tool steelsalloyed with Mo and V were heat treated, resulting microstructures andtempering carbides were studied and transformation characteristics determined for different austenitising temperatures and different cooling rates. The temperatures and cooling rates have been chosen to be representative for heat treatments of different sizes of tools. Bainite rather than martensite formed during slow cooling regardless of austenitising temperature. A lowered austenitising temperature produced largeramounts of both bainite and retained austenite while a higher caused graingrowth. Carbon partitioning during the bainitic transformation resulted in anincrease of the carbon content in the retained austenite of at least 0.3 wt.%. The austenitising temperature influences also the type and amount of tempering carbides that precipitate, which affects the properties of the steel. Higher austenitising temperatures favour the precipitation of MC carbides during tempering. The Mo rich M2C type carbides were proven to be more prone to coarsening during service at 560°C-600°C, while V rich MC carbides preserve their fine distribution. A best practice heat treatment needs to balance the increase of grain size with increasing austenitising temperatures, with the possibility to form more tempering carbides. Higher austenitising temperatures also give less retained austenite, which can affect dimensional stability and toughness negatively after tempering

  • 34.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Li, Xin-Hai
    Siemens Turbomachinery.
    Tricoire, Aurelien
    Volvo Aero Corp.
    Dorfman, Mitch
    Sulzer Metco.
    Next Generation Thermal Barrier Coatings for the Gas Turbine Industry2010In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, ISSN 1059-9630, Vol. 20, no 1-2, p. 108-115Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to develop the next generation of production ready air plasma sprayed thermalbarrier coating with a low conductivity and long lifetime. A number of coating architectures wereproduced using commercially available plasma spray guns. Modifications were made to powder chemistry,including high purity powders, dysprosia stabilized zirconia powders, and powders containingporosity formers. Agglomerated & sintered and homogenized oven spheroidized powder morphologieswere used to attain beneficial microstructures. Dual layer coatings were produced using the two powders.Laser flash technique was used to evaluate the thermal conductivity of the coating systems from roomtemperature to 1200 C. Tests were performed on as-sprayed samples and samples were heat treated for100 h at 1150 C. Thermal conductivity results were correlated to the coating microstructure using imageanalysis of porosity and cracks. The results show the influence of beneficial porosity on reducing thethermal conductivity of the produced coatings.

  • 35.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Östergren, Lars
    Volvo Aero Corporation, Trollhättan.
    Li, Xin-Hai
    Siemens Industrial Turbomachinery, Finspång.
    Dorfman, Mitch
    Sulzer Metco, Westbury, USA.
    Evaluation of the Lifetime and Thermal Conductivity of Dysprosia-Stabilized Thermal Barrier Coating Systems2013In: Journal of thermal spray technology (Print), ISSN 1059-9630, E-ISSN 1544-1016, Vol. 22, no 6, p. 864-872Article in journal (Refereed)
    Abstract [en]

    The aim of this study was the further development of dysprosia stabilised zirconia coatings for gas turbine applications. The target for these coatings was a longer lifetime and higher insulating performance compared to today's industrial stan dard thermal barrier coating. Two morphologies of ceramic top coat were studied; one using a dual layer systems and the second using a polymer to generate porosity. Evaluations were carried out using laser flash technique to measure thermal properties. Lifetime testing was conducted using thermal shock testing and thermo-cyclic fatigue testing. Microstructure was assessed with SEM and Image analysis used to characterise porosity content. The results show that coatings with an engineered microstructure give performance twice that of the present reference coating.

  • 36.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Mechanical Engineering.
    VanEvery, Kent
    Progressive Surface, Grand Rapids, MI 49512, USA .
    Snyder, Todd
    Progressive Surface, Grand Rapids, MI 49512, USA.
    Markocsan, Nicolaie
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Thermal Conductivity Analysis and Lifetime Testing of Suspension Plasma-Sprayed Thermal Barrier Coatings2014In: Coatings, ISSN 2079-6412, Vol. 4, no 3, p. 630-650Article in journal (Refereed)
    Abstract [en]

    Suspension plasma spraying (SPS) has become an interesting method for the production of thermal barrier coatings for gas turbine components. The development of the SPS process has led to structures with segmented vertical cracks or column-like structures that can imitate strain-tolerant air plasma spraying (APS) or electron beam physical vapor deposition (EB-PVD) coatings. Additionally, SPS coatings can have lower thermal conductivity than EB-PVD coatings, while also being easier to produce. The combination of similar or improved properties with a potential for lower production costs makes SPS of great interest to the gas turbine industry. This study compares a number of SPS thermal barrier coatings (TBCs) with vertical cracks or column-like structures with the reference of segmented APS coatings. The primary focus has been on lifetime testing of these new coating systems. Samples were tested in thermo-cyclic fatigue at temperatures of 1100 °C for 1 h cycles. Additional testing was performed to assess thermal shock performance and erosion resistance. Thermal conductivity was also assessed for samples in their as-sprayed state, and the microstructures were investigated using SEM

  • 37.
    Curry, Nicholas
    et al.
    University West, Department of Engineering Science, Division of Manufacturing Processes. Treibacher Industrie AG, Althofen 9330, Austria.
    VanEvery, Kent
    Progressive Surface, Grand Rapids, MI 49512, USA.
    Snyder, Todd
    Progressive Surface, Grand Rapids, MI 49512, USA.
    Susnjar, Johann
    Treibacher Industrie AG, Althofen 9330, Austria.
    Björklund, Stefan
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Performance Testing of Suspension Plasma Sprayed Thermal Barrier Coatings Produced with Varied Suspension Parameters2015In: Coatings, ISSN 2079-6412, Vol. 5, no 3, p. 338-356Article in journal (Refereed)
    Abstract [en]

    Suspension plasma spraying has become an emerging technology for the production of thermal barrier coatings for the gas turbine industry. Presently, though commercial systems for coating production are available, coatings remain in the development stage. Suitable suspension parameters for coating production remain an outstanding question and the influence of suspension properties on the final coatings is not well known. For this study, a number of suspensions were produced with varied solid loadings, powder size distributions and solvents. Suspensions were sprayed onto superalloy substrates coated with high velocity air fuel (HVAF) -sprayed bond coats. Plasma spray parameters were selected to generate columnar structures based on previous experiments and were maintained at constant to discover the influence of the suspension behavior on coating microstructures. Testing of the produced thermal barrier coating (TBC) systems has included thermal cyclic fatigue testing and thermal conductivity analysis. Pore size distribution has been characterized by mercury infiltration porosimetry. Results show a strong influence of suspension viscosity and surface tension on the microstructure of the produced coatings.

  • 38.
    Das, Kallol
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Effect of tool wear on surface integrity and burr formation in drilling of titanium alloy, Ti6Al4V2015Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Titanium alloys have been extensively used in aerospace industries and account for almost 30 wt% of materials used in an aerospace engine. Surface integrity of machined titanium components has a significant effect on reliability and sustainability those components in aer-ospace industry. Surface integrity could be affected by process parameters, cooling condi-tions and the wear level of the tools used in machining. An important example is the surface integrity of the holes drilled in titanium alloy Ti6Al4V. Although previous studies have shown that tool wear and cutting parameters influence surface integrity and burr formation, little work has been published about the effect of drill wear on the surface integrity and burr formation in drilling of titanium alloys in detail. In this study the influence of tool wear and use of coolant on surface integrity and burr formation in drilling of Ti6Al4V has been inves-tigated by metallographic study and micro hardness measurement of the material adjacent to holes drilled on plates of Ti6Al4V with drills of various wear levels and at three different cutting conditions. Micro structural and micro hardness alteration in drilled holes at the hole entrance, in the middle of the hole and at the hole exit as well as burr formation have been analyzed for the tool wear levels 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 mm. The tests were carried out in vertical direction without coolant and horizontal and vertical directions with coolant. The results show that limiting the wear level on the drills and use of coolant significantly lower the burr formation and microstructural alterations. Higher tool wear levels increase the depth of micro structural deformation, micro hardness and burr heights. These differences are not significant for wear levels up to 0.4 mm irrespective of cutting conditions but increase sig-nificantly when tool wear level exceeds 0.6 mm.

  • 39.
    Devotta, Ashwin
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Löf, Ronnie
    Sandvik Coromant AB, Sandviken, Sweden.
    FE Modelling and Characterization of Chip Curl in Nose Turning processIn: International Journal of Machining and Machinability of Materials, ISSN 1748-572XArticle in journal (Refereed)
  • 40.
    Devotta, Ashwin Moris
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Characterization of Chip Morphology in Oblique Nose Turning employing High Speed Videography and Computed Tomography Technique2016In: Proceedings International Conference on Competitive manufacturing: January 27, 2016 – January 29, 2016 Stellenbosch, South Africa, Conference on Assembly Technologies & Systems (CIRP), 2016, p. 249-254Conference paper (Refereed)
  • 41.
    Devotta, Ashwin Moris
    et al.
    University West, Department of Engineering Science, Research Enviroment Production Technology West.
    Beno, Tomas
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Löf, Ronnie
    Sandvik Coromant AB, Sandviken, Sweden.
    Modeling of Chip curl in Orthogonal Turning using Spiral Galaxy describing Function2016Conference paper (Refereed)
  • 42.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Analytical Stability Prediction in Five Axis Ball-End Milling2013In: Proceedings of the International Conference on Advanced Manufacturing Engineering and Technologies NEWTECH 2013 / [ed] Andreas Archenti and Antonio Maffei, Stockholm: KTH Royal Institute of Technology, 2013, p. 189-198Conference paper (Refereed)
    Abstract [en]

    In five axis ball-end milling, the cutting edge is a continuous curve and the engagement with workpiece changes as the cutting tool rotates. Therefore the sensitivity to vibration varies along the cutting edge and as the tool rotates. In this paper, the vibration-force relationship (VFR) is obtained for infinitesimal length of cutting edge as a function of tool’s rotation angle. Numerical integration results in the VFR of the whole cutting edge and the tool. VFR of the tool is coupled to the dynamic vibration model of the tool and the workpiece to predict the possibility of vibrational instability. This algorithm is then used to predict the effects of changing the lead angle in a test setup with a flexible depth of cut direction. The analytical results, along with experiments demonstrate that the large lead angles considerably improve the stability of the process.

  • 43.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Effect of thin viscoelastic material treatments of the clamping region on dynamic stiffness of the cantilever beams2013In: Proceedings of the International Conference on Advanced Manufacturing Engineering and Technologies NEWTECH 2013: Volume 1 / [ed] Andreas Archenti and Antonio Maffei, Stockholm: KTH Royal Institute of Technology, 2013, p. 313-322Conference paper (Refereed)
    Abstract [en]

    Cantilever beams and similar structures are found in machining systems. Often a set of cantilever beams attached to each other on spindle-tool holder and tool holder-cutter interfaces position the cutting edge with respect to the workpiece. Small static stiffness leads to deformations and geometrical errors due to the process forces, while small dynamic stiffness initiates chatter vibrations. Dynamic stiffness of structures could be improved by passive or active damping methods. Passive damping methods are suitable design choices considering their low cost and ease of application. In this paper, the constrained layer damping (CLD) method is compared to the application of viscoelastic damper materials on the clamping region and the resulting improvements are compared in terms of enhancement of damping ratio and dynamic stiffness. The maximum enhancement of dynamic stiffness was 487% using a thick layer of viscoelastic material on the clamping region. The effect of the thickness of the viscoelastic material is also studied which shows a linear increase in dynamic stiffness as the thickness of the viscoelastic layer increases.

  • 44.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Frequency Domain Study of Vibrations above and under Stability Lobes in Machining Systems2014In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 14, p. 164-169Article in journal (Refereed)
    Abstract [en]

    Using modified Nyquist contours, the dominant poles of the closed loop delay-differential equation for machining systems such as milling are identified. Contours with constant damping ratio of the dominant poles are constructed using this method. These contours are similar in shape to the stability lobes, but move upwards and to the right as the instability parameter increases. Additionally, it is possible to study the movement of the dominant poles to the right-hand side of the complex plane as the system becomes unstable by increasing the depth of cut at a constant spindle speed. The movement of the dominant pole is shown to be towards the right (unstable) and upward (higher vibration frequency) of the complex plane. In some cases, there would be a jump of vibration frequency due to the change of the lobe number. It is also shown that the damping ratio of the structure strongly affects both the vibration frequency and the damping ratio of the dominant poles in the closed loop system. Finally, in two milling experiments with two different spindle speeds and continuously increasing depth of cuts, vibration frequencies are measured and compared to the theoretical predictions. The measurements agree with the theoretical predictions, particularly in the unstable cutting conditions.

  • 45.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Prediction of vibration frequencies in milling using modified Nyquist method2015In: CIRP - Journal of Manufacturing Science and Technology, ISSN 1755-5817, E-ISSN 1878-0016, Vol. 11, no November, p. 73-81Article in journal (Refereed)
    Abstract [en]

    Study of the vibration frequencies at different cutting conditions is an alternative to the use of impact hammer test for identification of natural frequencies of the machining structure and calculation of stability lobe diagrams. Vibration frequencies not only depend on the natural frequencies of the structure, but also they are dependent on the spindle speed, damping ratio of the structure and the depth of cut. Ignoring these additional parameters would lead to errors in identification of the natural frequencies of the system and considerable deviation of the calculated stability lobe diagrams from actual cutting tests. In this study modified Nyquist method is used to investigate the effects of spindle speed, depth of cut and damping ratio of the structure on vibration frequencies. The quality of frequency prediction is compared to linear and nonlinear time domain simulations and machining experiments.

  • 46.
    Eynian, Mahdi
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Vibration frequencies in stable and unstable milling2015In: International Journal of Machine Tools and Manufacture, ISSN 0890-6955, Vol. 90, p. 44-49Article in journal (Refereed)
    Abstract [en]

    Vibration frequencies in machining may be employed for calculation of natural frequencies of the dominant modes in chatter and selection of chatter-free spindle speeds with large material removal rates. In this approach, it is important to investigate the relationship between the vibration frequencies, the natural frequencies, spindle speeds and depth of cuts for both stable and unstable cutting conditions. In this paper, the dominant poles of the closed loop time delay differential equation of a milling operation are calculated by successive sectioning of the complex plane and using Cauchy's argument principle. Vibration frequency and damping ratio of the closed loop machining system for each cutting condition is calculated based on the position of the dominant pole on the complex plane which provides 3D plots of the vibration frequency and closed loop damping ratio over any range of depth of cuts and spindle speeds. Finally, the findings of the analytical approach are compared to a machining experiment and a time domain simulation and differences and similarities in their predictions are discussed.

  • 47.
    Fisk, Martin
    et al.
    Materials Science and Applied Mathematics, Malmö University.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes. GKN Aerospace Engine Systems, Trollhättan.
    du Rietz, Rickard
    Materials Science and Applied Mathematics, Malmö University.
    Haas, Sylvio
    MAX IV Laboratory, Lund University.
    Hall, Stephen
    Division of Solid Mechanics, Lund University.
    Precipitate evolution in the early stages of ageing in Inconel 718 investigated using small-angle x-ray scattering2014In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 612, p. 202-207Article in journal (Refereed)
    Abstract [en]

    Microstructural evolution during the early stages of ageing (less than one hour) in a Ni-Cr-Fe based superalloy Inconel 718 (IN718) has been investigated using Small-Angle X-ray Scattering (SAXS). The effects of precipitate kinetics on the precipitate size distribution are compared indirectly with SAXS measurements by using Vickers microhardness data. The microhardness increased after 4 min of ageing at a temperature of 760 degrees C, although the recorded SAXS data did not reveal the precipitate size distribution. This indicates that the precipitates had not evolved enough to be detected, but still a small number of precipitates increased the yield strength. After ageing the alloy for the shortest period for which data were available, 8 min, clear evidence of precipitates could be found from the SAXS data, showing that the gamma ‘’ - precipitates are about 6 nm in width and 3 nm in height. (C) 2014 Elsevier B.V. All rights reserved.

  • 48.
    Fisk, Martin
    et al.
    Malmö Högskola.
    Lundbäck, Andreas
    Luleå Tekniska Universitet.
    Andersson, Joel
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Lindgren, Lars-Erik
    Luleå Tekniska Universitet.
    Finite Element Analysis Using a Dislocation Density Based Flow Stress Model Coupled with Model for Precipitate Evolution2014In: 8th International Symposium on Superalloy 718 and Derivatives / [ed] E. Ott, A. Banik, J. Andersson, I. Dempster, T. Gabb, J. Groh, K. Heck, R. Helmink, X. Liu och A. Wusatowska-Sarnek, Hoboken, NJ, USA: John Wiley & Sons, 2014, p. 155-168Conference paper (Refereed)
  • 49.
    Freton, Pierre
    et al.
    University Paul Sabatier, Toulouse, France.
    Choquet, Isabelle
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Gonzales, Jean-Jacques
    University Paul Sabatier, Toulouse, France.
    Teulet, Philippe
    University Paul Sabatier, Toulouse, France.
    Improvement of a pseudo kinetic method for the calculation of a two-temperature thermal plasma composition2013In: Proceedings of the XXth Symposium on Physics of Switching Arc, 2013, p. 139-142Conference paper (Refereed)
    Abstract [en]

    This paper proposes an improved Saha law for calculating the 2T composition of an Argon thermal plasma. This law is based on a simplified kinetic approach. The obtainedresults are compared with other laws from the literature (Van de Sanden, Pseudokinetic) and provide a satisfying qualitative behaviour.

  • 50.
    Freton, Pierre
    et al.
    Paul Sabatier University, Toulouse, France.
    Gonzales, Jean-Jacques
    Paul Sabatier University, Toulouse, France.
    Choquet, Isabelle
    University West, Department of Engineering Science, Division of Manufacturing Processes.
    Mougenot, Jacques
    Paul Sabatier University, Toulouse, France.
    Discussion sur les différentes formulations des équations de l´énergie dans les modèles de plasmas thermiques à deux températures2013Conference paper (Other academic)
    Abstract [fr]

    Pour modéliser un plasma thermique à deux températures, les travaux de la littérature proposent en général de résoudre une équation pour l’énergie des électrons et une autre pour celle des lourds. Néanmoins, tous les auteurs ne sont pas d’accord sur une formulation et diverses écritures de ces deux équations de l'énergie peuvent être trouvées dans la littérature. Les principales différences concernent deux termes : le terme correspondant à l'énergie d'ionisation et le terme relatif à la part de conductivité thermique réactive. Suivant les auteurs ces deux termes peuvent être attribués, indifféremment à l’équation de l’énergie régissant la température des particules lourdes ou celle des électrons.

      Afin de nous positionner et éclaircir ce point, nous proposons de développer théoriquement les deux équations de l'énergie en repartant de l'équation de Boltzmann et de ses moments. Les résultats obtenus avec la formulation proposée sont alors comparés avec ceux obtenus avec les formulation de la littérature.

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