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  • 1.
    Alam, Md. Minhaj
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Tuominen, Jari
    Tampere University of Technology.
    Vuoristo, Petri MJ J
    Tampere University of Technology.
    Miettinen, Juha S.
    Tampere University of Technology.
    Poutala, J.
    Department of Mechanics and Design, Tampere University of Technology.
    Näkki, Jonne
    Tampere University of Technology.
    Junkala, J.
    Tampere University of Technology.
    Peltola, Tero
    Tampere University of Technology.
    Surface pore initiated fatigue failure in laser clad components2013In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 25, no 3Article in journal (Refereed)
    Abstract [en]

    A laser clad and machined cylindrical structural steel rod was fatigue tested under four-point bending load. The resulting fracture could be tracked back to a spherical surface pore in the Co-based coating. Due to an oxide inclusion, the pore was not identified by dye penetrant inspection. Two circular buckling strain patterns that were detected beside the pore at the surfaces after fracture confirm local plastic deformation prior to crack initiation. In order to calculate the stress field around the surface pore, linear elastic finite element analysis was carried out. For four-point bending load, a surface pore generally exceeds the maximum stress of a smooth rod as long as the pore is located within an azimuthal angle of ±55°, which was the case for the presented as well as for another pore initiated sample.

  • 2.
    Al-Mashikhi, S.O.
    et al.
    University of Notttingham.
    Powell, John
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Voisey, K.T.
    University of Notttingham.
    An explanation of ‘striation free' cutting of mild steel by fibre laser2009In: Lasers in manufacturing 2009: proceedings of the Fifth International WLT-Conference Lasers in Manufacturing, LIM 2009 : Munich, Germany, June 15th - 18th, 2009 / [ed] Andreas Ostendorf, Stuttgart: AT-Fachverlag , 2009Conference paper (Refereed)
    Abstract [en]

    This paper presents the results of an experimental and theoretical investigation into the phenomenon of ‘striation free cutting', which is a feature of fibre laser cutting of thin section mild steel. The paper concludes that the creation of very low roughness edges is related to an optimisation of the cut front geometry when the cut front is inclined at angles close to the Brewster angle for the laser - material combination. For purely geometric reasons this particular type of cut front optimisation is not possible for CO2 laser cutting of mild steel.

  • 3.
    Al-Mashikhi, S.O
    et al.
    Salalah College of Technology, Engineering Department, Salalah, Oman and Faculty of Engineering, University of Nottingham.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Voisey, K.T.
    Faculty of Engineering, University of Nottingham.
    Heat affected zones and oxidation marks in fiber laser–oxygen cutting of mild steel2011In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 23, no 4Article in journal (Refereed)
    Abstract [en]

    The effect of cutting speed and sheet thickness on surface oxidation and heat affected zones (HAZs) has been investigated for laser–oxygen cutting of mild steel sheet with a fiber laser. Optical and scanning electron micrographs were used to determine the extent of surface oxidation and HAZ from plan and cross-sectional views, respectively. The HAZ is consistently wider at the bottom of the cut compared to the HAZ at the top of the cut. With increasing speed, the width of the HAZ at the top of the cut decreases whereas the HAZ width at the bottom of the cut generally increases. No simple, direct relationship between HAZ width and surface oxidation was seen. However, it is possible to state that in each case considered here, the HAZ would be completely removed if they are machined back by a depth equal to the extent of the surface oxidation.

  • 4.
    Andersson, Roger
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Magnusson, Claes
    Fem-simulation of forming and subsequently impact behaviour of a stainless steel component2005In: Proceedings of the 8th ESAFORM Conference on Material Forming / [ed] Dorel Banabic, Bucharest: The Romanian Academy Publishing House , 2005, Vol. 1, p. 265-268Conference paper (Refereed)
  • 5.
    Andersson, Roger
    et al.
    Swedish Tool and Die Technology, Aurorum 8A.
    Syk, M.
    Swedish Tool and Die Technology, Aurorum 8A.
    Powell, John
    Magnusson, Claes
    Volvo.
    Development of high strain rate equations for stainless steels2005In: Journal of materials engineering and performance (Print), ISSN 1059-9495, E-ISSN 1544-1024, Vol. 14, no 5, p. 553-562Article in journal (Refereed)
    Abstract [en]

    The dynamic response of four types of stainless steel sheet was investigated at different strain rates from 10-2 up to 103 s-1. The results from the tensile tests were used to evaluate the parameters in three different multiplicative strain rate equations of the type used in crashworthiness calculations. A new type of sigmoid constitutive equation is proposed for one grade of stainless steel. [Materials include 1.4362 and Nanoflex steels; application is automotive manufacturing].

  • 6.
    Andersson, Roger
    et al.
    Luleå tekniska universitet.
    Syk, M.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Magnusson, Claes
    Formability behaviour of meta-stable stainless steels2005In: Proceedings of the 8th ESAFORM Conference on Material Forming / [ed] Dorel Banabic, Bucharest: The Romanian Academy Publishing House , 2005, Vol. 1, p. 359-362Conference paper (Refereed)
  • 7.
    Atiyah, H.
    et al.
    Faculty of Engineering, The University of Nottingham.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Petring, D.
    Fraunhofer Institute for Laser Technology ILT.
    Stoyanov, S.
    Fraunhofer Institute for Laser Technology ILT.
    Voisey, T.
    Faculty of Engineering, The University of Nottingham.
    Fiber laser cutting: The use of carbon-filled acrylic as a qualitative and quantitative analysis tool2018In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 30, article id 032009Article in journal (Refereed)
    Abstract [en]

    The use of carbon-filled black acrylic (CFBA) as a quantitative and qualitative analytical tool for fiber laser cutting is investigated. In the qualitative work, CFBA targets placed below the laser cutting zone when cutting stainless steel showed a distinctive “leaf” shaped evaporation crater which can provide information about the nature of the reflections taking place in the cut zone. Quantitative measurements have revealed a specific evaporation energy of 3.4 J/mm3 for CFBA. However, this figure is only applicable when considering intense beams when the CFBA target is stationary with respect to the laser beam.

  • 8.
    Bergström, David
    et al.
    Mid Sweden University, Östersund.
    Powell, John
    Laser Expertise Ltd., Acorn Park Industrial Estate, Nottingham.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    A ray-tracing analysis of the absorption of light by smooth and rough metal surfaces2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 11, p. 113504-1Article in journal (Refereed)
    Abstract [en]

    Ray tracing has been employed to investigate the absorption of light by smooth and random rough metal surfaces. For normally incident light the absorptance of the surface increases with surface roughness. However, for light incident at a tangent to the surface the absorptance-surface roughness relationship is more complex. For example, in certain cases the absorptance can rise, fall, and rise again as the surface roughness increases. In this paper this complex absorptance-roughness relationship is defined and explained. The wavelengths of the light chosen for this study correspond to the primary and secondary output wavelengths of Nd:YAG lasers.

  • 9.
    Bergström, David
    et al.
    Mid Sweden University.
    Powell, John
    Laser Expertise Ltd., Acorn Park Industrial Estate, Nottingham.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Absorptance of nonferrous alloys to Nd:YLF and Nd:YAG laser light at room temperature2007In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 46, no 8, p. 1290-1301Article in journal (Refereed)
    Abstract [en]

    The measurement of absorptance is important for the analysis and modeling of laser-material interactions. Unfortunately, most of the absorptance data currently available consider only polished pure metals rather than the commercially available (unpolished, oxidized) alloys that are actually being processed in manufacturing. We present the results of absorptance measurements carried out at room temperature on as-received engineering grade nonferrous metals (Al, Cu, and Zn alloys). The measurements were made using an integrating sphere with a Nd:YLF laser at two wavelengths (1053 and 527 nm, which means that the results are also valid for Nd:YAG radiation at 1064 and 532 nm). The absorptance results obtained differ considerably from the existing data for polished, pure metals and should help improve the accuracy of laser-material interaction models. Some clear trends were identified. For all 22 cases studied the absorptance was higher than for ideal pure, polished metals. For all Al and Cu samples the absorptance was higher for the green than it was for the infrared wavelength, while for all Zn coatings this trend was reversed. No clear correlation between absorptance and surface roughness was found at low roughness values (Sa 0.15-0.60), but one rougher set of samples (Sa 2.34) indicated a roughness-absorptance correlation at higher roughness levels.

  • 10.
    Bergström, David
    et al.
    Mittuniversitetet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Fresnel absorption of rough metal surfaces using ray-traycing analysis2007In: 2007 European conference on lasers and electro-optics, IEEE Communications Society, 2007Conference paper (Refereed)
  • 11. Bergström, David
    et al.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Laser absorption measurements in opaque solids2005In: 10th NOLAMP Conference: the 10th Nordic Laser Materials Processing Conference, 17-19 August 2005, Luleå Sweden / [ed] Alexander Kaplan, Luleå: Luleå tekniska universitet, 2005, p. 91-115Conference paper (Refereed)
  • 12. Bergström, David
    et al.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Light scattering and absorption in Gaussian random rough metal surfaces using the geometric optics approximation2007In: Proceedings / M4PL 20: Igls/Innsbruck (A), 17. - 19.01.2007, 2007Conference paper (Refereed)
  • 13.
    Bergström, David
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Nd:YAG laser absorptance of rough metal surfaces2007In: Congress proceedings: 2007 ICALEO, 26th International Congress on Applications of Lasers & Electro-Optics : October 29 - November 1, 2007, Hilton in the Walt Disney World Resort, Orlando, FL, USA ; [including] Laser Materials Processing Conference, Laser Microprocessing Conference [and] Nanomanufacturing Conference / [ed] Yongfeng Lu, Orlando, Fla: Laser institute of America , 2007Conference paper (Refereed)
    Abstract [en]

    The Nd:YLF/Nd:YAG laser absorptance of rough metal surfaces has been investigated using 3D ray tracing simulations on computer-generated Gaussian random rough metal surfaces. The impact of multiple scattering, shadowing and Fresnel-equation based angle dependence on the overall absorption is discussed

  • 14. Bergström, David
    et al.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Ray-tracing analysis of Nd:YAG laser absorption by random rough metal surfaces2007In: 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, 2007Conference paper (Refereed)
  • 15.
    Bergström, David
    et al.
    Luleå tekniska universitet.
    Powell, John
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    The absorptance of metal surfaces to Nd:YAG/Nd:YLF laser light2008In: Conference proceedings: / 3rd Pacific International Conference on Applications of Lasers and Optics, PICALO : April 16 - 18, 2008, Capital Hotel, Beijing, China / [ed] Minlin Zhong, Orlando, Fla.: Laser institute of America , 2008, p. 375-380Conference paper (Refereed)
    Abstract [en]

    The absorptance of real metallic engineering surfaces used in Laser Material Processing depends strongly upon the particular surface conditions, including the degree of roughness and oxidation. In this paper the influence of surface topography on Nd:YAG/Nd:YLF laser absorptance has been studied, both experimentally and theoretically, on a set of randomly selected as-received metallic engineering surfaces. The surfaces were sputter-coated with a thin layer of gold to eliminate differences in surface chemistry and oxidation. The absorptance was measured using integrating sphere reflectometry and compared to calculations from 3D ray-tracing simulations of AFM-scanned images of the surfaces. The results have increased the understanding of how surface roughness influences the laser-workpiece coupling efficiency.

  • 16.
    Bergström, David
    et al.
    Mid Sweden University.
    Powell, John
    Laser Expertise Ltd., Acorn Park Industrial Estate, Nottingham.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    The absorptance of steels to Nd:YLF and Nd:YAG laser light at room temperature2007In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 253, no 11, p. 5017-5028Article in journal (Refereed)
    Abstract [en]

    The measurement of absorptance is important for the analysis and modelling of laser-material interactions. Unfortunately, most of the absorptance data presently available considers only polished pure metals rather than the commercially available (unpolished, oxidised) alloys, which are actually being processed in manufacturing. This paper presents the results of absorptance measurements carried out at room temperature on as-received engineering grade steels including hot and cold rolled mild steel and stainless steels of various types. The measurements were made using an integrating sphere with an Nd:YLF laser at two wavelengths (1053 and 527 nm, which means that the results are also valid for Nd:YAG radiation at 1064 and 532 nm). The absorptance results obtained differ considerably from existing data for polished, pure metals and should help improve the accuracy of laser-material interaction models. Some clear trends were identified; for all materials studied, the absorptance was considerably higher than the previously published values for the relevant pure metals with polished surfaces. For all 15 samples the absorptance was higher for the green than for the infrared wavelength. No clear trend correlating the absorptance with the roughness was found for mild steel in the roughness range Sa 0.4-5.6 μm. A correlation between absorptance and roughness was noted for stainless steel for Sa values above 1.5 μm.

  • 17.
    Bergström, David
    et al.
    Mid Sweden University, Department of Engineering, Physics and Mathematics.
    Powell, John
    Laser Expertise Ltd., Acorn Park Industrial Estate, Nottingham.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    The absorption of light by rough metal surfaces: a three-dimensional ray-tracing analysis2008In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, no 10Article in journal (Refereed)
    Abstract [en]

    The laser absorptance of rough surfaces has been investigated by using Monte Carlo simulations based on three-dimensional (3D) ray tracing. The influence of multiple scattering, shadowing, and the Fresnel-equation based angle dependence is discussed. The 3D results are compared to previously published results from a two-dimensional ray-tracing analysis and the different applications of the two models are explained

  • 18.
    Bergström, David
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    The absortion of light by rough metal surfaces: a three-dimensional ray-tracving analysis2007In: Congress proceedings: 2007 ICALEO, 26th International Congress on Applications of Lasers & Electro-Optics : October 29 - November 1, 2007, Hilton in the Walt Disney World Resort, Orlando, FL, USA ; [including] Laser Materials Processing Conference, Laser Microprocessing Conference [and] Nanomanufacturing Conference / [ed] Yongfeng Lu, Orlanndo, Fla: Laser institute of America , 2007Conference paper (Refereed)
  • 19.
    Bergström, David
    et al.
    Mittuniversitetet, Östersund.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    The reflectance of steels and non-ferrous alloys to Nd:YAG and Nd:YLF laser light2006In: Peer reviewed conference proceedings: / PICALO 2006, 2nd Pacific International Conference on Applications of Lasers and Optics : April 3 - 5, 2006, Grand Hyatt Melbourne, Melbourne, Australia / [ed] Milan Brandt, Orlando, Fla.: Laser institute of America , 2006, p. 140-145Conference paper (Refereed)
    Abstract [en]

    The measurement of reflectance is important for the analysis and modelling of laser-material interactions. Unfortunately, most of the reflectance data presently available consider only polished pure metals rather than the commercially available (unpolished, oxidised) alloys which are actually being processed. This paper presents the results of reflectance measurements carried out on asreceived engineering grade metals including: hot and cold rolled mild steel, zinc coated mild steel, stainless steel, aluminium alloys, copper and brass. The measurements were made using an integrating sphere with an Nd:YLF laser at two wavelengths (1053 nm and 527 nm). The results obtained differ considerably from existing data for polished, pure metals and should help to improve the accuracy of laser-material interaction models.

  • 20.
    Ducharme, R.
    et al.
    University of Essex.
    Kapadia, Phiroze D.
    University of Essex.
    Lampa, C.
    Luleå tekniska universitet.
    Ivarsson, Anders
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Magnusson, Claes
    Effects of different shielding gas compositions on the process of cw CO2 laser welding in the hyperbaric range1996In: XI International Symposium on Gas Flow and Chemical Lasers and High-Power Laser Conference / [ed] Denis R. Hall; Howard J. Baker, Bellingham, Wash: SPIE - International Society for Optical Engineering, 1996, p. 530-533Conference paper (Refereed)
    Abstract [en]

    A continuous carbon-dioxide laser of 1.35 kW has been used to study the welding of 5 mm thick stainless steel for pressures ranging from 0.1 to 0.8 MPa in increments of 0.1 MPa. Experimental data, including penetration depths, weld widths, and in some cases weld pool profiles, has been obtained for each value of the pressure using different mixtures of argon and helium shielding gases. In a previous paper it has been reported that keyhole welding could not be carried out for pressures significantly in excess of atmospheric pressure using pure argon and nitrogen shielding gases, but that the process was possible at pressures up to 0.8 MPa using helium. In the present paper the critical pressure for keyhole welding is determined as a function of the mixed shielding gas composition. The laser material interaction is analyzed by solving the heat conduction equation with line and point heat sources representing the keyhole and plume respectively. The line source strength is itself calculated from consideration of the inverse bremsstrahlung and Fresnel absorption processes in the keyhole. It is concluded that successful laser welding in the hyperbaric range crucially hinges on good plume control through the effective delivery of an appropriate shielding gas mixture.

  • 21.
    Eriksson, Ingemar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Gren, Per
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    New high-speed photography technique for observation of fluid flow in laser welding2010In: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 49, no 10Article in journal (Refereed)
    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.

  • 22.
    Eriksson, Ingemar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Haglund, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Sjödahl, Mikael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Holographic measurement of thermal distortion during laser spot welding2012In: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 51, no 3Article in journal (Refereed)
    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.

  • 23.
    Eriksson, Ingemar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Melt behavior on the keyhole front during high speed laser welding2013In: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 51, no 6, p. 735-740Article in journal (Refereed)
    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.

  • 24.
    Eriksson, Ingemar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Guidelines in the choice of parameters for hybrid laser arc welding with fiber lasers2013In: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 41, p. 119-127Article in journal (Refereed)
    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.

  • 25.
    Eriksson, Ingemar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    High speed video analysis of melt flow inside fiber laser welding keyholes2011In: Congress proceedings ICALEO: 30th International Congress on Applications of Lasers & Electro-Optics : October 23-27, 2011, Orlando, Fl., Laser institute of America , 2011, p. 221-226Conference paper (Refereed)
    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.

  • 26.
    Eriksson, Ingemar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Measurements of fluid flow on keyhole front during laser welding2011In: Science and technology of welding and joining, ISSN 1362-1718, E-ISSN 1743-2936, Vol. 16, no 7, p. 636-641Article in journal (Refereed)
    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

  • 27.
    Eriksson, Ingemar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Melt flow measurement inside the keyhole during laser welding2011In: 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, 2011Conference paper (Refereed)
    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.

  • 28.
    Eriksson, Ingemar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Kaplan, Alexander
    Signal overlap in the monitoring of laser welding2010In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, no 10Article in journal (Refereed)
    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

  • 29.
    Eriksson, Ingemar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Surface tension generated defects in full penetration laser keyhole welding2014In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 26, no 1, article id 12006Article in journal (Refereed)
    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.

  • 30.
    Eriksson, Ingemar
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Kaplan, Alexander
    Ultra high speed camera investigations of laser beam welding2010In: 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, p. 172-178Conference paper (Other academic)
    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.

  • 31. Forsman, Tomas
    et al.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Magnusson, Claes
    Initiation and termination phenomena in laser welding of aluminum2000In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 12, no 2, p. 81-84Article in journal (Refereed)
    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.

  • 32.
    Forsman, Tomas
    et al.
    Luleå tekniska universitet.
    Lampa, Conny
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Magnusson, Claes
    Prediction of the cross-sectional geometry of Nd:YAG laser welds in aluminum alloys2000In: Proceedings of the Laser Materials Processing Conference: [November 15 - 18, 1999, Catamaran Resort Hotel, San Diego, CA, USA], [presented at] ICALEO '99 / [sponsored by Laser Institute of America]. Co-chairs: Paul Denney ..., Orlando, Fla.: Laser institute of America , 2000, p. E156-E165Conference paper (Refereed)
    Abstract [en]

    This paper describes an analytical model for determining the geometry of laser welds. An earlier model by Lampa and Kaplan (1997), for CO2 laser welding of stainless steel, has been further developed to cover Nd:YAG laser welding of aluminium alloys. This analytical work was followed by experimental verification using a 4 kW Nd:YAG laser. The model was found to be accurate over a wide range of process parameters

  • 33. Forsman, Tomas
    et al.
    Magnusson, Claes
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Nd:YAG laser welding of coated aluminium sheet with a new dry lubricant film1998In: Svetsen, ISSN 0039-7091, Vol. 57, no 3, p. 10-12Article in journal (Refereed)
    Abstract [en]

    Trials are reported of the Nd:YAG laser welding of sheet of thickness about 1 mm in two aluminium alloys (AA-5182 (Al, 4.0-5.0%Mg) and AA-6016 (Al, 0.3-0.6%Mg, 1.0-1.5%Si)) coated with "Drylube" dry lubricant (some with zinc passivation first). Effects were investigated of welding conditions (constant or pulsed operation, gap of 0.0-0.3 mm) on porosity, penetration, and microcracking at the fusion boundary. Weld cross-sections are presented. Results are given also of hardness and tensile tests.

  • 34. Forsman, Tomas
    et al.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Lampa, Conny
    Luleå tekniska universitet.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Magnusson, Claes
    Nd:YAG laser welding of aluminium: factors affecting absorptivity1999In: Lasers in engineering (Print), ISSN 0898-1507, E-ISSN 1029-029X, Vol. 8, no 4, p. 295-310Article in journal (Refereed)
    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.

  • 35.
    Forsman, Tomas
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Magnusson, Claes
    A review of laser welding of low density structural materials: (Alloys of titanium, aluminium, magnesium and polymers)1997In: Proceedings of the 6th Nordic Laser Material Processing Conference, Luleå, Sweden, August 27-29, 1997 / [ed] Claes Magnusson; Hans Engström, Luleå: Luleå tekniska universitet, 1997, p. 44-57Conference paper (Refereed)
  • 36.
    Forsman, Tomas
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Magnusson, Claes
    Nd:YAG laser lap welding of coated aluminum alloys1997In: Proceedings of the Laser Materials Processing Conference: [November 17 - 20, 1997, Catamaran Resort Hotel, San Diego, California, USA] / [ed] Rémy Fabbro, Orlando, Fla: Laser institute of America , 1997, p. G113-G120Conference paper (Refereed)
    Abstract [en]

    This experimental program investigated the production of lap welds between 1 mm thick sheets of aluminium alloys 5182 and 6016 which had previously been coated with Drylube. (Drylube is a polymer based coating approx1 mu m thick which improves the formability of the aluminium alloy sheet). Successful welds were produced using a 2.5 kW Nd:YAG laser in conjunction with a 0.6 mm optical fibre. It was discovered that there is an optimum gap width between the two sheets which gives the best weld quality and strength. Pulsed and CW laser welds were produced and compared with respect to porosity and surface profile, etc

  • 37.
    Forsman, Tomas
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Magnusson, Claes
    Process instability in laser welding of aluminum alloys at the boundary of complete penetration2001In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 13, no 5, p. 193-198Article in journal (Refereed)
    Abstract [en]

    Intrinsic instabilities in the depth of penetration achieved when laser welding aluminum alloys were investigated in this article. Four types of weld pool configuration, resulting in different welds, were identified, only two of which are associated with full penetration. A simple phenomenological explanation of the unstable welding process at the boundary of complete penetration was proposed. The nature and cause of the instabilities were discussed and suggestions were offered for process control. Materials used: AA6016 aluminum alloy.

  • 38.
    Frostevarg, Jan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Torkamany, Mohammad
    Department of Materials Engineering, Tarbiat Modares University.
    Powell, John
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Improving weld quality by laser re-melting2014In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 26, no 4, article id 41502Article in journal (Refereed)
    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.

  • 39.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Melt-solid interactions in laser cladding and laser casting2005In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 36B, no 5, p. 683-689Article in journal (Refereed)
    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].

  • 40.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Rüstig, Katja
    Material Science and Materials Technology, Technische Universitat Bergakademie, Freiberg.
    Laser wire casting2003In: 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 , 2003Conference paper (Refereed)
  • 41.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Rüstig, Katja
    Material Science and Materials Technology, Technische Universitat Bergakademie, Freiberg.
    Laser wire casting2003In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 46, no 3, p. 199-201Article in journal (Refereed)
    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.

  • 42.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    A process efficiency comparison of Nd:YAG and CO2 laser cladding2002In: Welding in the World, ISSN 0043-2288, E-ISSN 1878-6669, Vol. 46, no spec, p. 75-86Article in journal (Refereed)
    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

  • 43.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    A process efficiency comparison of Nd:YAG and CO2 laser cladding2002In: 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 , 2002Conference paper (Refereed)
  • 44. Gedda, Hans
    et al.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Controlled laser melting of metal powders using moulds2005In: 10th NOLAMP Conference: the 10th Nordic Laser Materials Processing Conference, 17-19 August 2005, Luleå Sweden / [ed] Alexander Kaplan, Luleå: Luleå tekniska universitet, 2005, p. 225-238Conference paper (Refereed)
  • 45.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Development of the laser clad casting techniques2003In: 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, p. 137-148Conference paper (Refereed)
  • 46.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Laser cladding into pre-machining groves2004In: 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, p. 18-23Conference paper (Refereed)
    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

  • 47.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Shaping the cross section of laser clad layers and laser castings2005In: 10th NOLAMP Conference: the 10th Nordic Laser Materials Processing Conference, 17-19 August 2005, Luleå Sweden / [ed] Alexander Kaplan, Luleå: Luleå tekniska universitet, 2005Conference paper (Refereed)
  • 48.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Wahlström, G.
    Li, W-B
    Luleå tekniska universitet.
    Engström, Hans
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Magnusson, Claes
    Energy redistribution during CO2 laser cladding2001In: Congress proceedings: Laser Materials Processing Conference; Laser Microfabrication Conference [at] ICALEO 2001, 20th International Congress on Applications of Lasers & Electro-Optics : October 15 - 18, 2001, Adam's Mark Hotel, Jacksonville, Florida, USA / [ed] Xiangli Chen, Orlando, Fla: Laser institute of America , 2001, p. 549-558Conference paper (Refereed)
    Abstract [en]

    This paper examines the factors that effect the efficiency of the CO sub 2 -laser powder cladding process. By theoretical calculation and experimental work it has been possible to identify how much of the original laser energy contributes to the cladding process and how much is lost to the surrounding environment by reflection, radiation, convection etc. Every aspect of energy redistribution has been analysed and quantified and this has lead to a deeper understanding of the process. The paper concludes with a number of suggestions for improving the efficiency of blown powder laser cladding

  • 49.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Wahlström, G.
    Duroc AB.
    Li, W-B
    Luleå tekniska universitet.
    Engström, Hans
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Magnusson, Claes
    Energy redistribution during CO2 laser cladding2002In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 14, no 2, p. 78-82Article in journal (Refereed)
    Abstract [en]

    This article examines the factors that effect the efficiency of the CO sub 2 -laser powder cladding process. By theoretical calculation and experimental work it has been possible to identify how much of the original laser energy contributes to the cladding process and how much is lost to the surrounding environment by reflection, radiation, convection, etc. Every aspect of energy redistribution has been analyzed and quantified and this has led to a deeper understanding of the process. The article concludes with a number of suggestions for improving the efficiency of blown powder laser cladding.

  • 50.
    Haglund, Peter
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Eriksson, Ingemar
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Powell, John
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Surface tension stabilized laser welding (donut laser welding): A new laser welding technique2013In: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 25, no 3Article in journal (Refereed)
    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.

123 1 - 50 of 129
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