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Sökning: WFRF:(Powell John F) > Konferensbidrag

  • Resultat 1-4 av 4
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1.
  • Eriksson, Ingemar, et al. (författare)
  • Ultra high speed camera investigations of laser beam welding
  • 2010
  • Ingår i: Congress proceedings ICALEO. - Anaheim, CA : Laser institute of America. - 9780912035611 ; , s. 172-178
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • 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.
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2.
  • Frostevarg, Jan, 1982-, et al. (författare)
  • The formation of osseointegrating surfaceson titanium by laser irradiation
  • 2018
  • Ingår i: 71st IIW General Assembly, C-IV.
  • Konferensbidrag (refereegranskat)abstract
    • 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
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3.
  • Olsson, Rickard, 1959-, et al. (författare)
  • Topographical evaluation of laser generated surfaces using statistical analysis of surface-normal vector distributions
  • 2021
  • Ingår i: IOP Conference Series: Materials Science and Engineering. - : Institute of Physics (IOP).
  • Konferensbidrag (refereegranskat)abstract
    • Surfaces generated by Additive Manufacturing or laser texturing can involve the solidification of droplets of liquid, which can give rise to overhanging features on the solidified surface. Overhanging features add a layer of complexity to the surface topography and are undetectable by standard surface roughness measurement techniques such as profilometry. Such features are important because they can have a considerable effect on surface properties such as wettability. New techniques and algorithms are therefore required to analyse and quantify convoluted surfaces with overhanging (re-entrant) features. Earlier work by the authors introduced the concept of using X-ray micro-computed tomography (Micro-CT) to identify the directions of vectors normal to the surface at any point and thus indicate the presence or absence of overhanging features. This paper divides overhanging features into two types; simple and compound, and introduces new, size independent, analysis techniques which measure what proportion of each type is on the surface. Another extension of the analysis is the comparison of surface profiles taken in different directions in order to identify any surface roughness anisotropies.
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4.
  • Pocorni, Jetro Kenneth, et al. (författare)
  • Measuring the Melt Flow on the Laser Cut Front
  • 2015
  • Ingår i: 15th Nordic Laser Materials Processing Conference, Nolamp 15, 25-27 August 2015, Lappeenranta, Finland. - : Elsevier. ; 78, s. 99-109
  • Konferensbidrag (refereegranskat)abstract
    • The flow characteristics on the laser cut front for 10 mm stainless steel AISI 304 (EN 1.4301) are studied in this paper using High Speed Imaging (HSI). The laser cut samples were produced with a 6 kW fiber laser with nitrogen gas assist. Previous work in this field has used unusual cutting parameters to make the experimentation easier. This work presents, for the first time, HSI results from standard commercially viable cutting parameters. This was made possible by the development of a new experimental technique. The results presented here suggest that the cut front produced when cutting stainless steel with a fiber laser and a nitrogen assist gas is covered in bumps which themselves are covered in a thin layer of liquid. Under the conditions shown here the bumps move down the cut front at an average speed of approximately 0.4m/s. The liquid flows at an average speed of approximately 1.1m/s. The average melt depth at the bottom of the cut zone under these conditions is approximately 0.17 mm.
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  • Resultat 1-4 av 4

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