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  • 1.
    Bergström, David
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    The absorptance of metal surfaces to Nd:YAG/Nd:YLF laser light2008Ingår i: 3rd Pacific International Conference on Applications of Lasers and Optics, PICALO 2008 - Conference Proceedings, 2008, s. 375-380Konferensbidrag (Refereegranskat)
    Abstract [en]

    The absorptance of the metal 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 using 3D ray-tracing simulations. The results have increased the understanding of how surface roughness influences the laser-workpiece coupling efficiency.

  • 2.
    Bergström, David
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik och hållbar utveckling.
    The Absorption of Laser Light by Rough Metal Surfaces2008Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
  • 3.
    Bergström, David
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    The reflectance of steels and non-ferrous alloys: 2nd Pacific International Conference on Application of Lasers and Optics 20062006Ingår i: PICALO 2006 - 2nd Pacific International Conference on Applications of Laser and Optics - Conference Proceedings, 2006, s. 140-145Konferensbidrag (Övrigt vetenskapligt)
    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 as-received 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.

  • 4.
    Bergström, David
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Kaplan, AFH
    Powell, J
    Light scattering and absorption in Gaussian random rough metal surfaces using the geometric optics approximation2007Ingår i: 20th Meeting on Mathematical Modelling of Material Processing with Lasers, 2007Konferensbidrag (Refereegranskat)
  • 5.
    Bergström, David
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik och hållbar utveckling.
    Kaplan, AFH
    Powell, J
    The absorption of light by rough metal surfaces - a three-dimensional ray-tracing analysis2008Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, nr 10, s. 103515-Artikel i tidskrift (Refereegranskat)
    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.

  • 6.
    Bergström, David
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Kaplan, Alexander
    Mathematical Modelling of Laser Absorption Mechanisms in Metals: A Review2003Ingår i: M4PL16 - 16th Meeting on Mathematical Modelling of Materials Processing with Lasers, 2003Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    In Laser Material Processing, an understanding of the fundamental absorption mechanisms plays a vital role in determining the optimum processing parameters and conditions. To this end, a combination of experimental as well as of theoretical work is required. In this paper, results of some of the most important mathematical models of laser-metal interactions are reviewed, including models for absorptivity dependence on wavelength, polarization, angle of incidence, workpiece temperature, surface roughness, defects, impurities and oxides.

  • 7.
    Bergström, David
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Kaplan, Alexander
    Powell, J
    Laser absorption measurements in opaque solids2005Ingår i: 10th NOLAMP Conference : the 10th Nordic Laser Materials Processing Conference, 17-19 August 2005, Luleå Sweden, Luleå: Luleå University of Technology , 2005, s. 444-Konferensbidrag (Refereegranskat)
    Abstract [en]

    In LaserMaterial Processing, an understanding of the fundamental absorption mechanisms plays a vital role in determining the optimum processing parameters and conditions. The absorptance, which characterizes how much a material absorbs, can alter during a processing application, as a result of melting, boiling, structural changes of the surface, oxidation, plasma formation, etc. To gain knowledge of these complex processes, a combination of experimental as well as of theoretical work is required. In this paper, an overview of the most common experimental methods and techniques to measure laser absorption in opaque solids, such as metals, will be presented.

  • 8.
    Bergström, David
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Powell, J
    Laser Expertise Ltd., Nottingham, NG7 2TR, United Kingdom.
    Kaplan, A
    Div. of Manufacturing Systems Engineering, Luleå University of Technology, S-971 87 Luleå, Sweden.
    Nd:YAG laser absorptance by rough metal surfaces2007Ingår i: 26th International Congress on Applications of Lasers and Electro-Optics, ICALEO 2007 - Congress Proceedings, 2007Konferensbidrag (Refereegranskat)
    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.

  • 9.
    Bergström, David
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Powell, J.
    Kaplan, A. F. H.
    A ray-tracing analysis of the absorption of light by smooth and rough metal surfaces2007Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, nr 11, artikel-id 113504Artikel i tidskrift (Refereegranskat)
    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.

  • 10.
    Bergström, David
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Powell, John
    Laser Expertise Ltd., Nottingham, United Kingdom.
    Kaplan, Alexander
    Luleå University of Technology.
    Absorptance of Non-Ferrous Alloys to Nd:YLF and Nd:YAG Laser Light at Room Temperature2007Ingår i: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 46, nr 8, s. 1290-1301Artikel i tidskrift (Refereegranskat)
    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 non-ferrous metals (Al, Cu and Zn alloys). The measurements were made using an integrating sphere with an Nd:YLF laser at two wavelengths (1053nm and 527nm � which means that the results are also valid for Nd:YAG radiation at 1064nm and 532nm). 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 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.

  • 11.
    Bergström, David
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Powell, John
    Laser Expertise Ltd., Nottingham, United Kingdom.
    Kaplan, Alexander
    Luleå University of Technology.
    The absorptance of steels to Nd:YLF and Nd:YAG laser light at room temperature2007Ingår i: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 253, nr 11, s. 5017-5028Artikel i tidskrift (Refereegranskat)
    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.

1 - 11 av 11
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