• JLA Vol:8 Iss:4 (Acoustic emission from modulated laser beam welding of materials)

    Hongping Gu
    W. W. Duley
    Guelph‐Waterloo Program for Graduate Work in Physics, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1

    Acoustic emission during the laser welding of metals with a modulated CO2 laser beam has been investigated. Sharp resonances at many frequencies in the acoustic emission spectra have been observed. This was most noticeable when the average laser power was high enough to produce full penetration welds whose acoustic emission at high harmonics with frequencies that overlap with bands of vibrational frequencies corresponding to eigenmodes of the keyhole are greatly enhanced. Lower harmonics were not clearly observe...


  • JLA Vol:8 Iss:4 (Integrated instruction: Lasers across the curriculum in an associate's degree program)

    R. Allen Shotwell
    Ivy Tech State College, 7999 U.S. Highway 41, Terre Haute, IN 47802, U.S.A.


  • JLA Vol:8 Iss:4 (Laser hazard evaluation method for middle infrared laser systems)

    Wesley J. Marshall
    Robert C. Aldrich
    Sheldon A. Zimmerman

    Hazard evaluation methods for lasers, with wavelengths greater than 1.4 μm (mostly in the middle infrared), have changed significantly in the current version of the American National Standard for the Safe Use of Lasers, ANSI Z136.1‐1993. A correct evaluation involves comparing the hazard potential based on two evaluation models; one based on individual pulses and the other based on an equivalent continuous‐wave exposure. An example of the hazard evaluation method within this spectral region is provided.


  • JLA Vol:8 Iss:4 (On the relation between fluid dynamic pressure and the formation of pores in laser keyhole welding)

    John Dowden
    Phiroze Kapadia
    Andy Clucas
    R. Ducharme
    W. M. Steen

    In the laser welding of metals with a continuous CO2 laser, a hole containing a partially ionized metal vapor is formed throughout the depth of the material. A full description of flow conditions inside this hole is needed for a complete understanding of the process, but much can be learned from a simpler analysis of this aspect of the problem. The balance of forces that keeps the keyhole open can be investigated in this way. Such a model shows that over most of the keyhole's length, the dominant force keeping the keyhole open against surface tension...


  • JLA Vol:8 Iss:4 (Some aspects of laser heating of engineering materials)

    B. S. Yilbas
    A. Z. Al‐Garni
    Mechanical Eng. Dept., KFUPM, P.O. Box 1913, Dhahran, Saudi Arabia

    Laser induced heating processes are important when a laser is used as a machine tool in industry, since the quality of the machining process strongly depends on the heating mechanism. The present study examines a heat transfer model that provides useful information on the laser induced interaction mechanism. Steady state and time dependent heating models are introduced and temperature profiles inside the materials are predicted. Using appropriate assumptions, the time for the surface temperature to reach 90% of its steady state value is estimated. To valid...


  • JLA Vol:8 Iss:4 (The role of oxygen pressure in laser cutting mild steels)

    A. Ivarson
    J. Powell
    C. Magnusson

    This paper presents the results of an experimental program investigating the effects of using high pressure oxygen as assist gas in combination with a pulsed laser while cutting medium thick mild steel plates. It was discovered that if the pulse conditions are optimized, the maximum cutting speed for a set average laser power could be increased by up to 10% compared to low oxygen pressure continuous wave (CW) laser cutting. The assist gas was found to have two optimum pressure ranges between which the material suffered from burning on the cut edge. The paper presents a phenomenological model to explain the ch...


  • JLA Vol:8 Iss:5 (A guide to developing a laser standard operating procedure)

    Ken Barat
    Lawrence Berkeley National Laboratory, Berkeley, CA 94720, U.S.A.

    The ANSI Z 136.1 standard requires a standard operating procedure (SOP), however, it does not recommend or suggest a format for the SOP. The goal of this article is to outline, explain and suggest an SOP format that could be applied by a laser safety officer to a varied number of situations and laser uses.


  • JLA Vol:8 Iss:5 (Diode‐pumped Nd:YAG laser for precision laser machining)

    Jason Machan
    Marcy Valley
    Gerry Holleman
    Marc Mitchell
    Dave Burchman
    Jim Zamel
    George Harpole
    Hagop Injeyan
    Len Marabella
    TRW R1/1184, One Space Park, Redondo Beach, CA 90278, U.S.A.

    Results are presented on a high power, diode‐pumped, pulsed Nd:YAG laser for precision laser machining. The laser is an unstable resonator with a graded reflectivity outcoupler, generating a beam with excellent beam quality. The gain medium is a single zig‐zag slab, pumped symmetrically by diode arrays. The use of diode arrays minimizes the thermal loading on the slab, and the zig...


  • JLA Vol:8 Iss:5 (Excimer laser interactions with an aluminum alloy)

    Angelos Koutsomichalis
    Anastasia Kefalidou
    Laboratory of Physical Metallurgy, National Technical University of Athens, Zografou Campus 15773 Athens, Greece

    An AlCuMg alloy was irradiated using a KrF pulsed excimer laser. A microstructural study showed the presence of a laser treated zone having a uniform depth of approximately 20 μm. The surface layer of the laser treated aluminum alloy exhibited a wavy topography and its surface roughness was found to depend on the number of laser pulses per step. A X‐ray diffraction analysis revealed the presence of aluminum oxides and nitrides on the surface of the laser irradiated specimens. Corrosion measurements s...


  • JLA Vol:8 Iss:5 (Filtration of the fumes generated by industrial CO<sub>2</sub> laser cutting)

    J. Powell
    H. Haferkamp
    F. W. Bach
    D. Seebaum
    A. Hampe

    This paper reviews the subject of fume filtration in the context of industrial laser cutting. Self&hyphen;cleaning or surface filtration can be used to good effect when cutting metals. The clean exhaust air from such a filter can be recycled into the workplace with an obvious saving on heating bills. Fumes generated during non&hyphen;metal cutting are a great deal more difficult to filter and recycling of the air is not possible.



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