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  • 51. Engström, Hans
    et al.
    Norman, Peter
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    DATLAS: a new approach for monitoring the laser welding process2007Inngår i: 11th NOLAMP Conference: 11th NOLAMP Conference in Laser Processing of Materials ; Lappeenranta, August 20 - 22,2007 / [ed] Veli Kujanpää, Lappeenranta: Lappeenranta University of Technology Press, 2007Konferansepaper (Fagfellevurdert)
  • 52.
    Eriksson, Ingemar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Gren, Per
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    New high-speed photography technique for observation of fluid flow in laser welding2010Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 49, nr 10Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recent developments in digital high-speed photography allow us to directly observe the surface topology and flow conditions of the melt surface inside a laser evaporated capillary. Such capillaries (known as keyholes) are a central feature of deep penetration laser welding. For the first time, it can be confirmed that the liquid capillary surface has a rippled, complex topology, indicative of subsurface turbulent flow. Manipulation of the raw data also provides quantitative measurements of the vertical fluid flow from the top to the bottom of the keyhole.

    Fulltekst (pdf)
    FULLTEXT01
  • 53.
    Eriksson, Ingemar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Haglund, Peter
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Sjödahl, Mikael
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Holographic measurement of thermal distortion during laser spot welding2012Inngår i: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 51, nr 3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Welding distortion is an important engineering topic for simulation and modeling, and there is a need for experimental verification of such models by experimental studies. High-speed pulsed digital holography is proposed as a measurement technique for out-of-plane welding distortion. To demonstrate the capability of this technique, measurements from a laser spot weld are presented. A complete twodimensional deformation map with submicrometer accuracy was acquired at a rate of 1000 measurements per second. From this map, particular points of interest can be extracted for analysis of the temporal development of the final distortion geometry.

    Fulltekst (pdf)
    FULLTEXT01
  • 54. Eriksson, Ingemar
    et al.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Evaluation of laser weld monitoring: a case study2009Inngår i: Congress proceedings: ICALEO, 28th International Congress on Applications of Lasers & Electro-Optics : November 2 - 5, 2009 - Orlando, FL : Laser Materials Processing Conference, Laser Microprocessing Conference, Nanomanufacturing Conference, poster presentation, gallery, Orlando, Fla: Laser institute of America , 2009, Vol. 102, s. 1419-1425Konferansepaper (Fagfellevurdert)
    Abstract [en]

    On-line monitoring of the quality of laser welding is of interest for many industrial applications. For photodiodes the monitoring strategy usually aims at observing whether the signal exceeds a threshold. This well known technique is mainly based on empirical values, thus the monitoring has to be trained for each application. For improved understanding of the context between the physics of a welding defect generated and the resulting voltage signal, the experiments were observed by high speed imaging, followed by evaluation and modelling. A commercial system with three detector wavelength windows was studied for nine different industrial welding applications with distinct defects. We here present selected cases for which we try to generalise the findings and to draw conclusions for the applicability of commercial monitoring systems. For example humping was clearly detected by the signal, spatter and crater formation for overlapping Zn-coated steel surprisingly not. An interesting cause for welding defects is contamination of the joint prior to welding by oil, grease or detergents. The corresponding experiments showed unexpected signal responses, which can be partially explained by the analysis. We summarise that improved understanding of the signal causes facilitates to apply monitoring systems in a reliable manner.

    Fulltekst (pdf)
    FULLTEXT01
  • 55.
    Eriksson, Ingemar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Melt behavior on the keyhole front during high speed laser welding2013Inngår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 51, nr 6, s. 735-740Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The flow of molten metal on the front wall of a laser generated welding keyhole has been observed by high speed photography, optically measured by mapping the flow of ripples on the liquid surface and theoretically calculated. A clear downward flow can be observed and measured by a Particle Image Velocimetry algorithm. A theoretical calculation of the melt thickness on the keyhole front is also presented. Results indicate that the thickness of the liquid on the keyhole front is similar to that of the resolidified layer found in micrographs of the front if the laser is suddenly turned off. The measured surface ripple flow speeds are between two and four times as high as the theoretical average fluid flow rate.

    Fulltekst (pdf)
    FULLTEXT01
  • 56. Eriksson, Ingemar
    et al.
    Norman, Peter
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Basic study of photodiode signals from laser welding emissions2009Inngår i: 12th NOLAMP proceeding 2009: Nordic Laser Materials Processing Conference ; 24th - 26th August 2009 in Copenhagen, Kgs. Lyngby: ATV-SEMAPP , 2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Photodiodes are commonly used to monitor laser welding as a cheap, rugged, online method to get an indication of changes in the process, particularly the occurrence of defects. However, the correlations between the signal characteristics and the process are usually empirical and not fully understood. In this basic study we try to obtain a better understanding of the generation of the signals from the laser welding process. By synchronising high speed imaging with photodiode signals in three wavelength spectra, we attempt to identify the contributions from different geometrical domains and temporal events, particularly from the weld pool surface, the keyhole opening and the escaping metal vapour flow. It is particularly valuable to study dynamic behaviour during pulsed laser welding. A quantitative estimation is difficult, but , with the help of high speed photography and modelling, clear correlations between different dynamic events and signal changes can be identified.

    Fulltekst (pdf)
    FULLTEXT01
  • 57.
    Eriksson, Ingemar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Guidelines in the choice of parameters for hybrid laser arc welding with fiber lasers2013Inngår i: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 41, s. 119-127Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Laser arc hybrid welding has been a promising technology for three decades and laser welding in combination with gas metal arc welding (GMAW) has shown that it is an extremely promising technique. On the other hand the process is often considered complicated and difficult to set up correctly. An important factor in setting up the hybrid welding process is an understanding of the GMAW process. It is especially important to understand how the wire feed rate and the arc voltage (the two main parameters) affect the process. In this paper the authors show that laser hybrid welding with a 1 μm laser is similar to ordinary GMAW, and several guidelines are therefore inherited by the laser hybrid process.

    Fulltekst (pdf)
    FULLTEXT01
  • 58.
    Eriksson, Ingemar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    High speed video analysis of melt flow inside fiber laser welding keyholes2011Inngår i: Congress proceedings ICALEO: 30th International Congress on Applications of Lasers & Electro-Optics : October 23-27, 2011, Orlando, Fl., Laser institute of America , 2011, s. 221-226Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A high speed video survey of melt flow within fiber laser welding keyholes has revealed a number of interesting observations about the mechanics of weld formation. Using Streak Images and FFT (Fast Fourier Transform) techniques to interpret the video results, quantitative values of fluid flow velocities down the keyhole front have been established. The results have lead to a phenomenological understanding of some of the quality problems which arise at high welding speeds -such as undercut and humping.

  • 59.
    Eriksson, Ingemar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Measurements of fluid flow on keyhole front during laser welding2011Inngår i: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 16, nr 7, s. 636-641Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents the results of a high speed video survey of melt flow on the front face of a keyhole created during fibre laser welding. Using fast Fourier transform techniques, quantitative values of fluid flow velocities down the keyhole front have been established. The results have led to a phenomenological understanding of some of the quality problems which arise at excess welding speeds. The downward flow velocity on the keyhole front is found to be generally independent of welding speed, and proportional to laser power

    Fulltekst (pdf)
    FULLTEXT01
  • 60.
    Eriksson, Ingemar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Melt flow measurement inside the keyhole during laser welding2011Inngår i: 13th NOLAMP Conference: 13th Conference on Laser Materials Proce Nordic Countries 27 - 29 June 2011 / [ed] Einar Halmøy, Trondheim: Department of Geography, Norwegian University of Science and Technology, 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Laser keyhole welding has been in use for decades, but many of the complex mechanisms which take place within the keyhole remain poorly understood. Thispaper describes a streak image technique based on videos from high speed digital cameras. Itis similar to the technique used in goal cameras to visualize time-dependent events. Thecamera’s ability to acquire high speed image patterns with clear grayscale contrast hasenabled us to see the melt flow on the keyhole surface. In this paper the measured flowvelocity down the front of the keyhole is presented, showing a clear vertical downwardmotion on the keyhole front with speeds of the order of meters per second.

    Fulltekst (pdf)
    FULLTEXT01
  • 61.
    Eriksson, Ingemar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Kaplan, Alexander
    Signal overlap in the monitoring of laser welding2010Inngår i: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, nr 10Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Laser weld monitoring is usually based on the feedback from three photodiodes which are intended to provide independent information about the thermal condition of the melt (the T signal), the radiation from the plume of a heated gas above the melt (the P signal) and the amount of reflected laser light (the R signal). This work demonstrates that, in fact, the plume of the hot gas above the weld pool contributes a large part of the thermal signal, which has hitherto been assumed to come only from the melt itself. It is suggested that the correlation between the T and P signals is so strong that a T-P signal would be more useful than the raw T signal in identifying the fluctuations in infrared radiation from the melt pool

    Fulltekst (pdf)
    FULLTEXT01
  • 62.
    Eriksson, Ingemar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Surface tension generated defects in full penetration laser keyhole welding2014Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 26, nr 1, artikkel-id 12006Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    During laser keyhole welding of thin plates the melt pool is relatively wide compared to the plate thickness. Under certain conditions an elongated keyhole can be created and a permanent hole is sometimes left in the weld seam. The generation of such holes is determined by surface tension effects in the melt which can generate a self sustaining geometry at the rear of the melt pool. The geometry of the shape is known as a catenoid and has clear geometrical limits.

  • 63.
    Eriksson, Ingemar
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Kaplan, Alexander
    Ultra high speed camera investigations of laser beam welding2010Inngår i: Congress proceedings ICALEO: 29th International Congress on Applications of Lasers & Electro-Optics : September 26 - 30, 2010, Anaheim, CA, USA, Anaheim Marriot ; [including] Laser Materials Processing Conference, Laser Microprocessing Conference, Nanomanufacturing Conference / [ed] Xinbing Liu, Anaheim, CA: Laser institute of America , 2010, s. 172-178Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    With the help of high speed camera equipment, researchers can now directly observe melt flow phenomena which only could be imagined or simulated in the past. In this paper the motion of the molten metal inside the keyhole has been observed at frame rates as high as 180000 fps to provide useful information about the laser beam welding process. This paper describes two different cases where high speed imaging has given new insights into the laser beam welding process: A. In pulsed welding the melt pool oscillations can create ripples on the solidified weld surface. With the help of a high speed camera this phenomenon was analyzed, and the pulse shape was adjusted to reduce the ripple amplitude to a minimum. B. In Zn-coated steel edge welding it could be seen that blowouts were sometimes created in the melt pool at some distance behind the keyhole. Direct slowmotion observation has led to the formulation of a phenomenological model of this effect.

    Fulltekst (pdf)
    FULLTEXT01
  • 64. Forsman, Tomas
    et al.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Magnusson, Claes
    Initiation and termination phenomena in laser welding of aluminum2000Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 12, nr 2, s. 81-84Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article investigates a defect problem related to laser welding of tailored aluminum blanks. During the initial few millimeters of welding the weld was intermittent. By applying an analytical line source model the weld was shown to experience overheating close to the starting edge. This overheating was reduced by ramping the power during the initial 100 mm and this made the defects disappear. Al sheets of 0.1mm thickness with milled edges were butt welded and bead-on-plate welded in the present investigation.

  • 65. Forsman, Tomas
    et al.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Lampa, Conny
    Luleå tekniska universitet.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Magnusson, Claes
    Nd:YAG laser welding of aluminium: factors affecting absorptivity1999Inngår i: Lasers in engineering (Print), ISSN 0898-1507, E-ISSN 1029-029X, Vol. 8, nr 4, s. 295-310Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper investigates the factors affecting the absorptivity during Nd:YAG laser keyhole welding of a 6xxx aluminum alloy. The influence of surface condition on absorption is shown to be negligible. Experimental absorption measurements by calorimetry are compared to analytical absorption values using a simple model based on Fresnel absorption during multiple reflections in the keyhole.

  • 66.
    Frostevarg, Jan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Bunaziv, Ivan
    Norwegian University of Science and Technology, Department of Engineering Design and Materials.
    Axelsen, Odd M.
    Norwegian University of Science and Technology, Department of Engineering Design and Materials.
    Kaplan, Alexander F.H
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    45 mm thick steel section joining for cold climate applications by applyinglaser-arc hybrid welding2018Inngår i: 71st IIW International Conference, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Production and joining of components for energy industries(wind, oil and gas) for cold climate applications is achallenging task. Joining of thick steels is usually performedby using arc techniques such as submerged arc welding(SAW) or Gas Metal Arc Welding (GMAW). To fill thicksections, wide gap preparation is made and gradually filled inseveral weld passes. To reduce the number of weld passes,high power laser-arc hybrid welding (LAHW) is a promisingalternative, but can also weld at higher travel rates therebyreducing the total heat input and reduced filler material.LAHW is applied using a metal-cored wire, demonstratingwelding in 45 mm thick steel sheets. Setup and selection ofprocess parameters are essential for obtaining high processstability, penetration efficiency and material mixingthroughout the depth of the weld. Each weld where repeatedand performed on 500x200x45 mm (x,y,z) steel sheets withmilled joint edges. Using LAHW and selected materials, largeamounts of acicular ferrite was formed in the upper half of thejoint, gradually having increasingly more bainitic structurescloser to the weld root. 

    From these results, it is concluded thatLAHW has high potential for increased production efficiencyand lowered costs, potentially replacing arc welding for thesetypes of applications.

  • 67.
    Frostevarg, Jan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Differences between arc models in laser hybrid arc welding upon weld bead stability and undercut formation2013Inngår i: 14th NOLAMP Conference: The 14th Nordic Laser Materials Processing Conference, August 26th – 28th 2013, Gothenburg, Sweden / [ed] Alexander Kaplan; Hans Engström, Luleå: Luleå tekniska universitet, 2013, s. 205-216Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In this study, three different arc modes are studied in laser hybrid arc welding with a gasmetal arc, i.e. Standard, Pulsed and Cold Metal Transfer mode. Originally developed forbeing able to weld thin materials, the pulsed mode is the favoured arc mode in both ordinaryarc welding and hybrid welding. The pulsed mode is a more controlled gas metal arc weldingprocess that uses less heat and is able to weld thinner materials than the spray mode processwith globular drop transfer. The cold metal transfer mode utilizes surface tension droptransfer, compared to the free flying drops governing the other modes and is thus even morecontrolled than the pulsed mode. The cold metal transfer mode is much colder than the otherarc modes and is considered to generate less undercuts and spatter than the other modes, byboth developers and users alike.This study compares welds made by the three arc modes for both low and highdeposition rates. The welds are studied by macrographs, scanning and high speed imaging.This study shows that the differences between drop transfer modes are partially eliminateddue to the presence of a laser keyhole. The main arguments to use either arc mode arediscussed.

    Fulltekst (pdf)
    FULLTEXT01
  • 68.
    Frostevarg, Jan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Undercut suppression in laser-arc hybrid welding by melt pool tailoring2014Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 26, nr 3, s. 4-, artikkel-id 31501Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In welding, high welding speeds are usually limited by an increase in undercut. This study shows that the geometrical conditions of the melt flow can be tailored to suppress undercut when using the arc leading setup. By applying high speed imaging, it can be seen that the keyhole and its position affects the melt flow, making the distance between the laser and the arc an important parameter. Undercut formation usually occurs due to a narrowing or necking of the melt flow behind the gouge that can be prevented if the melt flow is changed by optimizing the laser/arc positioning

  • 69.
    Frostevarg, Jan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Undercuts in Laser Arc Hybrid Welding2014Inngår i: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 56, s. 663-672Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Undercuts are usually an imperfection in welding that either continuously or sporadically form, especially when welding at high speed. Efforts, usually lowering the welding speed or overfilling, are applied to avoid undercuts as they can significantly lower the fatigue properties of the welded workpiece. Undercut formation is complex and occurs by various means, mainly based on temperature and melt flow mechanisms. When having two power sources as in laser arc hybrid welding, the melt flow can be tailored to suppress undercut formation. This can be done e.g. by narrowing the width of the gouge or by optimum positioning of the power sources relative to each other. The present paper shows and explains the main reasons of various types of undercut formation. By following the herein generated guidelines, the critical welding speed during laser arc hybrid welding can be further increased, free of undercuts

  • 70.
    Frostevarg, Jan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Lamas, Javier
    Comparison of CMT with other arc modes for laser arc hybrid welding of 7 mm steel2013Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this study, three different arc modes in laser arc hybrid welding with a Gas Metal Arc (GMA) are studied, i.e. Standard, Pulsed and Cold Metal Transfer (CMT) mode. Originally developed for being able to weld thin materials, the pulsed mode is the favoured arc mode in both ordinary arc welding and laser hybrid welding. The pulsed mode is a more controlled GMA welding process that uses less heat and is able to weld thinner materials than the Standard mode process while utilizing globular drop flight transfer. The CMT mode utilizes surface tension drop transfer with controlled wire feeding and can thereby be used for much less heated welds compared to the other arc modes. It is also considered to generate less undercuts and spatter compared to the other modes, by both developers and users alike. This study compares hybrid welds made by the three arc modes for low and medium wire deposition rates, within the limits of the CMT process. The welds are studied by macrographs, scanning and high speed imaging. The study shows that the differences between the drop transfer modes are partially eliminated due to the presence of a laser keyhole. The dominating impact on the solidification and melt flow is the arc and especially the gouge created ahead of the keyhole. The main pros and cons to use either arc mode are discussed.

  • 71.
    Frostevarg, Jan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Lamas, Javier
    Luleå University of Technology, Centro Tecnolóxico do Naval Galego, Ferrol.
    Comparison of CMT with other arc modes for laser-arc hybrid welding of steel2014Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 58, nr 5, s. 649-660Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, three different arc modes in laser-arc hybrid welding with a gas metal arc were studied, i.e. the standard, pulsed and cold metal transfer (CMT) modes. The pulsed mode is more controlled than the standard mode and offers reduced heat input to the workpiece, which enables welding of thinner materials. The CMT mode utilizes surface tension drop transfer with controlled wire feeding, and therefore, involves less heat input than the other arc modes, and it is also considered to generate less undercut and spatter than the other modes. This study compares hybrid welds made by the three arc modes with a close-to-production setup for low and medium wire deposition rates, within the limits of the CMT process. The welds were studied by scanning and high speed imaging. The study shows that the differences between the drop transfer modes are reduced due to the presence of a laser keyhole. The dominating influence on the solidification and melt flow is the arc and especially the gouge created ahead of the keyhole. The main pros and cons of the different arc modes are discussed.

  • 72.
    Frostevarg, Jan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Olsson, Rickard
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Lasernova.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Laser Expertise Ltd.
    Palmquist, Anders
    Department of Biomaterials, University of Gothenburg, Gothenburg, Sweden.
    Brånemark, Rickard
    Department of Orthopaedic Surgery, University of California, San Francisco, USA.
    Kaplan, Alexander F.H.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    The formation of osseointegrating surfaceson titanium by laser irradiation2018Inngår i: 71st IIW General Assembly, C-IV, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Pulsed lasers can be used to modify the surface of medical implants in order to accelerate bone growth(osseointegration). Here, it is used to create a surface that is beneficial for rapid osseointegration, also calledBioHelix™, having ridges and covered in attached droplets of diameters between 1 and 20 μm. This paper presentsthe results of an experimental program in which a range of laser parameters were used to create different surfacetextures on titanium substrates. The resulting surfaces were analyzed by scanning electron microscope and MicroComputer Tomography. The paper explains how different types of surface are created by the laser-materialinteraction under different conditions. It is shown that optimization of the laser parameters results in a robustprocess which produces a surface that is fundamentally different from those created by other methods

  • 73.
    Frostevarg, Jan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Torkamany, Mohammad
    Department of Materials Engineering, Tarbiat Modares University.
    Powell, John
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Improving weld quality by laser re-melting2014Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 26, nr 4, artikkel-id 41502Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Laser welding, arc welding, and laser-arc hybrid welding can all result in undercut and varying penetration. In some cases, it is technically and commercially viable to reduce undercut at the weld cap and smooth out the weld root profile by defocussing the welding laser and using it to remelt the welded surfaces.

  • 74.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Melt-solid interactions in laser cladding and laser casting2005Inngår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 36B, nr 5, s. 683-689Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Experimental data in conjunction with mathematical models are used to explain various aspects of laser casting and laser cladding by the preplaced powder method. For increasing speed, the data can be distinguished between substrate melting, dilution-free clad bonding, bond-free casting, and poor contact breaking the melt track into spheres. Results include a thermodynamic explanation of the wide range of process parameters over which dilution-free clad deposits can be produced, as the process switches from heating of the insulating powder to additional cooling when the melt front reaches the substrate. Also, the interaction of the melt pool with the powder bed is analyzed to identify why laser castings have microscopically uneven surfaces and do not bind with the substrate. The advancement of the melt front through the powder layer is governed by heating, melting, and incorporation of each individual grain. Although most powder grains are in the small size range for the case studied, the few particles up to a factor 3 larger delay and therefore govern the front advancement due to much slower melting and surface tension driven incorporation, depending on the particle size in a nonlinear manner. [Substrate: mild steel; cladding material: Co-base alloy].

  • 75.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Rüstig, Katja
    Material Science and Materials Technology, Technische Universitat Bergakademie, Freiberg.
    Laser wire casting2003Inngår i: Congress proceedings: Laser Materials Processing Conference [and] Laser Microfabrication Conference [at] ICALEO 2003, 22nd International Congress on Applications of Lasers & Electro-Optics, October 13 - 16, 2003, Adam's Mark Hotel, Jacksonville, Florida, USA / [ed] Xiangli Chen, Orlando, Fla: Laser institute of America , 2003Konferansepaper (Fagfellevurdert)
  • 76.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Rüstig, Katja
    Material Science and Materials Technology, Technische Universitat Bergakademie, Freiberg.
    Laser wire casting2003Inngår i: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 46, nr 3, s. 199-201Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new technique has been developed for the production of solid wire or rods from powder by laser melting. Three techniques have been developed to ensure that the molten powder solidifies as a rod or wire rather than a series of droplets. The straight rods or wires produced in this way have near-circular cross-section, are several millimetres in diameter and can be pore free. The techniques can be used to produce welding rods, tensile test samples and other solid pieces from a wide range of powder mixes. The rapid thermal cycle involved means that it is now possible to produce hitherto difficult mixtures and alloys in the solid form in seconds.

  • 77.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    A process efficiency comparison of Nd:YAG and CO2 laser cladding2002Inngår i: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 46, nr spec, s. 75-86Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Blown powder laser cladding is a cost effective way of producing a surface layer to withstand wear and corrosion. However, the cladding process is slow. Therefore is it of great interest to investigate how much of the laser power is used in the cladding process and how much is reflected etc. In this investigation an Nd:YAG and a CO2-laser have been compared as energy sources for the process. Every aspect of the energy redistribution during cladding has been analysed. The main energy loss to the process for both lasers is by reflection from the melt pool and the powder cloud. It was found that the Nd: YAG laser cladding process is approximately twice as energy efficient as the CO2 laser cladding process

  • 78.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    A process efficiency comparison of Nd:YAG and CO2 laser cladding2002Inngår i: Congress proceedings: Laser Materials Processing Conference [and] Laser Microfabrication Conference [presented at] ICALEO 2002, 21st International Congress on Applications of Lasers & Electro-Optics, October 14 - 17, 2002, Double Tree Paradise Valley Resort, Scottsdale, Arizona, USA / [ed] Eckhard Beyer, Orlando, Fla: Laser institute of America , 2002Konferansepaper (Fagfellevurdert)
  • 79. Gedda, Hans
    et al.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Controlled laser melting of metal powders using moulds2005Inngår i: 10th NOLAMP Conference: the 10th Nordic Laser Materials Processing Conference, 17-19 August 2005, Luleå Sweden / [ed] Alexander Kaplan, Luleå: Luleå tekniska universitet, 2005, s. 225-238Konferansepaper (Fagfellevurdert)
  • 80.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Development of the laser clad casting techniques2003Inngår i: 9th NOLAMP Conference: 9th Conference on Laser Materials Processing in the Nordic Countries ; 4 - 6 August 2003, [Trondheim] / [ed] Einar Halmøy, Trondheim: Department of Geography, Norwegian University of Science and Technology, 2003, s. 137-148Konferansepaper (Fagfellevurdert)
  • 81.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Laser cladding into pre-machining groves2004Inngår i: Peer reviewed conference proceedings: PICALO 2004, 1st Pacific International Conference on Applications of Lasers and Optics : April 19 - 21, 2004, Grand Hyatt Melbourne, Melbourne, Australia, Orlando, Fla.: Laser institute of America , 2004, s. 18-23Konferansepaper (Fagfellevurdert)
    Abstract [en]

    When laser cladding is used to improve the wear characteristics of a substrate it is not always necessary to clad the whole surface. Wear resistant individual tracks can be clad directly onto the substrate or into pre machined grooves. This paper investigates the process parameters which affect the finished product when cladding into groves including; groove geometry, powder application method and laser type

  • 82.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Shaping the cross section of laser clad layers and laser castings2005Inngår i: 10th NOLAMP Conference: the 10th Nordic Laser Materials Processing Conference, 17-19 August 2005, Luleå Sweden / [ed] Alexander Kaplan, Luleå: Luleå tekniska universitet, 2005Konferansepaper (Fagfellevurdert)
  • 83.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Svoboda, Ales
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    FE-analysis of laser spot welding of microelectronics devices2003Inngår i: Proceedings of the 16th Meeting on Modelling, Simulation, Virtuality in High Power Laser Technology, M4PL 16: Igls/Innsbruck, 22.01.2003-24.01.2003 / Vienna University of Technology, Department of Nonconventional Processing, Forming and Laser Technology / [ed] D. Schöcker, 2003Konferansepaper (Fagfellevurdert)
  • 84.
    Haglund, Peter
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Eriksson, Ingemar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Surface tension stabilized laser welding (donut laser welding): A new laser welding technique2013Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 25, nr 3Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new laser welding process is presented which delivers a porosity free, spatter free weld. The process involves a donut shaped melt with a central hole of the same order of magnitude as the material thickness. The laser illuminates only the leading section of this melt. The hole is kept open by the melt surface tension.

  • 85.
    Haglund, Peter
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Westinghouse Electric Sweden AB, Västerås.
    Frostevarg, Jan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Eriksson, Igemar
    Dalco Elteknik AB, Östersund.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Holographic measurement of distortion during laser melting: Additive distortion from overlapping pulses2018Inngår i: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 100, s. 1-6Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Laser - material interactions such as welding, heat treatment and thermal bending generate thermal gradients which give rise to thermal stresses and strains which often result in a permanent distortion of the heated object. This paper investigates the thermal distortion response which results from pulsed laser surface melting of a stainless steel sheet. Pulsed holography has been used to accurately monitor, in real time, the out-of-plane distortion of stainless steel samples melted on one face by with both single and multiple laser pulses. It has been shown that surface melting by additional laser pulses increases the out of plane distortion of the sample without significantly increasing the melt depth. The distortion differences between the primary pulse and subsequent pulses has also been analysed for fully and partially overlapping laser pulses.

  • 86.
    Hashemzadeh, M.
    et al.
    Faculty of Engineering, University of Nottingham.
    Suder, W.
    Welding Engineering Research Centre, Cranfield University.
    Williams, S.
    Welding Engineering Research Centre, Cranfield University.
    Powell, John
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Voisey, K.T.
    Faculty of Engineering, University of Nottingham.
    The Application of Specific Point Energy Analysis to Laser Cutting with 1 μm Laser Radiation2014Inngår i: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 56, s. 909-918Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Specific point energy (SPE) is a concept that has been successfully used in laser welding where SPE and power density determine penetration depth. This type of analysis allows the welding characteristics of different laser systems to be directly compared. This paper investigates if the SPE concept can usefully be applied to laser cutting. In order to provide data for the analysis laser cutting of various thicknesses of mild steel with a 2 kW fibre laser was carried out over a wide range of parameter combinations. It was found that the SPE concept is applicable to laser cutting within the range of parameters investigated here

  • 87.
    Hauser, Tobias
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling. Siemens AG, Otto-Hahn-Ring 6, 81739 München, Germany.
    Breese, Philipp Peter
    Siemens AG, Otto-Hahn-Ring 6, 81739 München, Germany.
    Kamps, Tobias
    Siemens AG, Otto-Hahn-Ring 6, 81739 München, Germany.
    Heinze, Christoph
    Siemens AG, Siemensdamm 50, 13629 Berlin, Germany.
    Volpp, Joerg
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander F.H.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Material transitions within multi-material laser deposited intermetallic Iron Aluminides2020Inngår i: Additive Manufacturing, ISSN 2214-8604, artikkel-id 101242Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Laser Metal Deposition is a near-net-shape processing technology, which allows remarkable freedom in multi-material processing. In the present work, the multi-material processing of two intermetallic iron aluminides, Fe28Al(at.%) and Fe30Al5Ti0.7B(at.%), was investigated. It has been shown that multi-material processing of the two alloys via discrete as well as via gradual material transition is possible without any cracks for manufacturing small cubes. Cross-sections of manufactured parts and tracks showed that a preheating temperature of at least 400 °C is necessary to process crack free samples. EDX-analyses indicated that if a discrete material transition is required in multi-material processing, the material transition should be implemented in the vertical build-up direction because the mixing zone in this direction is significantly smaller than the mixing zone in the horizontal direction. Due to the stronger mixing effects in the horizontal direction, a gradual material transition by a linear progression should be implemented in this direction rather than in the vertical direction. The mixing effects are mainly caused by melt flow, while diffusion effects can be neglected.

  • 88.
    Håkansson, Anders
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Innovation och Design.
    Abrahamsson, Lena
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Arbetsvetenskap.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Engström, Hans
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Määttä, Antti
    University of Oulu.
    Mäntyjärvi, Kari
    University of Oulu.
    Barriers to implementation of laser welding technology: A study of 11 companies in Scandinavia2015Inngår i: Manufacturing Science and Technology, ISSN 2333-2735, Vol. 3, nr 2, s. 48-55Artikkel i tidsskrift (Fagfellevurdert)
  • 89.
    Ilar, Torbjörn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Eriksson, Ingemar
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Root humping in laser welding: an investigation based on high speed imaging2012Inngår i: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 39, s. 27-32Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Regular drop formation (humping) along the weld root during laser welding was studied by high speed imaging of the melt pool underneath the workpiece. The formation of droplets towards the rear of this weld pool was seen to be primarily caused by the pumping of melt from the bottom of the keyhole and the influence of gravity drawing melt into a sagging hump. This is a different process from the one which creates humps on the top surface of welds.

  • 90.
    Ilar, Torbjörn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    An extended feasibility study to identify laser welding and laser.arc hybrid welding business cases and business models2013Inngår i: 14th NOLAMP Conference: The 14th Nordic Laser Materials Processing Conference, August 26th – 28th 2013, Gothenburg, Sweden / [ed] Alexander Kaplan; Hans Engström, Luleå: Luleå tekniska universitet, 2013, s. 217-226Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The laser research group at Luleå University of Technology has, in collaboration withSwedish industries, performed more than 20 laser welding and laser arc hybrid welding casestudies during the last decade. Most of them can be considered as successful and havedemonstrated improved mechanical properties, new design opportunities and higher weldingproductivity. Nevertheless, very few of the successful case studies have resulted in anindustrial application and the number of industrial implementations is still very limited. Thereare of course several reasons, like company organisation, human factors or lack of experience,but usually it is a rational analysis based on return of investment. The case studies are alsousually limited to one component at one company without any further evaluation and analysisof other business opportunities, i.e. other components/products within the company orforming a cluster of companies in a geographic region. This paper presents an extend analysesof a number of the performed case studies with the objectives to evaluate and identifybusiness cases. Different business models, such as investigate product families for laserwelding within a company and company clusters with common laser welding resource, isevaluated and analysed.

    Fulltekst (pdf)
    FULLTEXT01
  • 91. Ilar, Torbjörn
    et al.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Hybright - generic understanding of the mechanical strength of hybrid welds2007Inngår i: 11th NOLAMP Conference: 11th NOLAMP Conference in Laser Processing of Materials ; Lappeenranta, August 20 - 22, 2007 / [ed] Veli Kujanpää, Lappeenranta: Lappeenranta University of Technology Press, 2007Konferansepaper (Fagfellevurdert)
  • 92. Ilar, Torbjörn
    et al.
    Powell, John
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Modelling, simulation and analyses of systems with breakdown imposed scrapping2009Inngår i: Journal of Simulation, ISSN 1747-7778, Vol. 3, nr 2, s. 107-113Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This study shows that, for many manufacturing processes (such as welding and injection moulding), a machine breakdown will result in the scrapping of a component, and goes on to explain the effect that this can have on process simulation models. Breakdown-related scrapping events are ignored by commercially available process simulation packages and this reduces their usefulness in decision support. This paper explains the different types of breakdown/scrapping dynamic possible and clearly demonstrates the scrapping dynamics effect on one of the major performance measures in LEAN-based manufacturing systems, namely the Overall Equipment Effectiveness. The paper also demonstrates the effect on model accuracy of a miss interpretation of part scrap behaviour or none deliberately simplified modelling of part scrap. This uncertainty in model accuracy will reduce the usefulness of the simulation model as a decision support tool.

  • 93.
    Ilar, Torbjörn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    Simulation of production lines involving unreliable machines: the importance of machine position and breakdown statistics2007Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper demonstrates the importance of choosing the correct statistical distributions for breakdown frequency and duration when simulating production line productivity. Statistical distributions with a wide range tend to reduce the productivity of the line. Also, it is demonstrated that the productivity of a production line can be improved simply by re-arranging the order of unreliable machines in the line. If the line consists of similar or exchangeable machines, productivity can improved if the most unreliable machines are placed towards the end of the line.

    Fulltekst (pdf)
    FULLTEXT01
  • 94. Ilar, Torbjörn
    et al.
    Powell, John
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Simulation of production lines: The importance of breakdown statistics and the effect of machine position2008Inngår i: International Journal of Simulation Modelling, ISSN 1726-4529, Vol. 7, nr 4, s. 176-185Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper demonstrates the importance of choosing the correct values and statistical distributions for breakdown frequency and duration when simulating production line productivity. Statistical distributions with a wide range tend to reduce the productivity of the line but this trend can be disrupted by poor choice of mean values for the variables in question. Also, it is demonstrated that the productivity of a production line can be improved simply by re-arranging the order of unreliable machines in the line. If the line consists of similar or exchangeable machines, productivity can improved if the most unreliable machines are placed towards the end of the line. The paper also demonstrates the risks of reduction of the standard deviation to obtain a more deterministic model.

  • 95.
    Ilar, Torbjörn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Powell, John
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik.
    Kaplan, Alexander
    The effect of process interruption and scrap on production simulation models2007Inngår i: CARV 2007: 2nd International Conference on Changeable, Agile, Reconfigurable and Virtual Production, Toronto, Ontario, Canada, july, 23-24 2007 : today's reaction, tomorrow's challenge / [ed] Michael F. Zäh; Hoda A. ElMaraghy, CARV , 2007Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This study shows that, for many manufacturing processes (such as welding and injection moulding), a machine breakdown will result in the scrapping of a component, and goes on to explain the effect that this can have on process simulation models. Breakdown related scrapping events are ignored by commercially available process simulation packages and this reduces their usefulness in decision support. This paper explains the different types of breakdown/scrapping dynamic possible and provides equations which can be used to describe them in future generations of simulation software. This work clearly demonstrates the scrapping dynamics effect on one of the major performance measures in LEAN based manufacturing systems, namely the Overall Equipment Effectiveness.

    Fulltekst (pdf)
    FULLTEXT01
  • 96.
    Johansson, Charlotta
    et al.
    Luleå tekniska universitet.
    Svenningsson, Inge
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Achieving advantages of scale in small companies through horizontal networking2004Inngår i: Adaptive engineering for sustainable value creation: ICE 2004, the 10th International Conference on Concurrent Enterprising ; Sevilla, Spain, 14 - 14 June 2004 ; [proceedings] / [ed] Klaus-Dieter Thoben, Nottingham: Centre for concurrent enterprising, University of Nottongham , 2004Konferansepaper (Fagfellevurdert)
  • 97.
    Johansson, Christian
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Innovation och Design.
    Karlsson, Jan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Bertoni, Marco
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Innovation och Design.
    Chirumalla, Koteshwar
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Innovation och Design.
    Enhancing intra-cognitive communication between engineering designers and operators: a case study in the laser welding industry2012Inngår i: Proceedings of the 3rd IEEE International Conference on Cognitive Communications: CogInfoCom 2012, Piscataway, NJ: IEEE Communications Society, 2012, s. 493-497Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In manufacturing, metal parts can be joined using a laser as a welding tool, i.e. laser welding. Despite huge amount of research over the years, the process is neither sufficiently understood nor mathematically predictable. This study aims to holistically analyze the knowledge management issues occurring in laser welding. Emerging from observations and semi-structured interviews from industry and academy, the complexity and the criticalities of the process as well as the current knowledge transfers is explained and analyzed, using a knowledge lifecycle framework as a reference. Besides enhanced awareness of the limiting issues, information and knowledge visualization, e.g. knowledge maps, is identified as a key for progress in the community. The Matrix Flow Chart is suggested as an alternative descaled map of process changes.

  • 98.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    10th NOLAMP Conference: the 10th Nordic Laser Materials Processing Conference, 17-19 August 2005, Luleå Sweden2005Collection/Antologi (Annet vitenskapelig)
  • 99. Kaplan, Alexander
    A model of deep penetration laser welding based on calculation of the keyhole profile1994Inngår i: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 27, nr 8, s. 1805-1814Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A model describing the process of deep-penetration laser welding has been developed by calculating the keyhole profile using a point-by-point determination of the energy balance at the keyhole wall. A formula for heat conduction was derived from the model of a moving line source of heat. The various absorption mechanisms were modelled. The corresponding absorbed power transferred to the keyhole wall balances the conduction losses, which yields the local inclination of the wall. The thermodynamics and the flow of metal vapour inside the keyhole have been calculated. Accordingly, beam damping due to the plasma plume above the workpiece and the mean plasma absorption coefficient in the keyhole could be estimated. The keyhole profile tends to a geometry that distributes the major part of the beam to the front wall owing to higher conduction losses at the upstream side. The reasons for decreasing energy absorption with increasing welding speed are discussed.

  • 100.
    Kaplan, Alexander
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Produkt- och produktionsutveckling.
    Absorption behavior in microelectronics laser welding2003Inngår i: Proceedings of the 16th Meeting on Modelling, Simulation, Virtuality in High Power Laser Technology, M4PL 16: Igls/Innsbruck, 22.01.2003-24.01.2003 / Vienna University of Technology, Department of Nonconventional Processing, Forming and Laser Technology / [ed] D. Schuöcker, 2003Konferansepaper (Fagfellevurdert)
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