• JLA Vol:14 Iss:3 (Evaluation of nozzle geometries for laser surface alloying)


    Authors:
    Terri L. Tramel
    Mary H. McCay
    John A. Hopkins
    T. Dwayne McCay
    The University of Tennessee Space Institute, Tullahoma, Tennessee


    Five general types of nozzles and nine configurations were tested in a water tunnel and using gas pressure analysis to determine their effectiveness at reducing entrained air from the outside environment during laser surface alloying. Two orientations with regard to the work piece were employed: The optics and nozzle being normal, the optics and nozzle being at a 15° oblique angle. Both argon and nitrogen were studied. In the impingement region, they produced roughly the same results regardless of the nozzle...

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  • JLA Vol:14 Iss:3 (Laser-assisted chemical etching for embedded microchannels and overhanging microstructures on Si/SiO<sub>2</sub> substrates)


    Authors:
    George P. Vakanas
    Array

    Ampere A. Tseng
    Department of Mechanical and Aerospace Engineering, Arizona State University, Tempe, Arizona 85287

    Paul Winer
    Silicon Debug Tools Development, SC9-09, Intel Corporation, Santa Clara, California 95054


    The feasibility of fabricating buried (embedded or subsurface) microstructures between silicon and silicon oxide using laser-assisted chemical etching (LACE) in chlorine atmosphere is demonstrated in this article. An associated LACE ablation model and sample calculations based on one-dimensional thermal analysis and chemical kinetics are presented. A strategy for optimizing the laser process for 3...

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  • JLA Vol:14 Iss:3 (Prevention of welding defect by side gas flow and its monitoring method in continuous wave Nd:YAG laser welding)


    Authors:
    Kenichi Kamimuki
    Takashi Inoue
    Applied Laser Engineering Research Institute, 2085-16 Uenoyama, Fukasawamachi, Nagaoka, Niigata 940-2135, Japan

    Kouzou Yasuda
    Mikio Muro
    Tokuhiro Nakabayashi
    Technical Institute, Kawasaki Heavy Industries, 118 Futatsuzuka, Noda, Chiba 278-8585, Japan

    Akira Matsunawa
    Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan


    In the Nd:yttrium–aluminum–garnet (YAG) laser welding of thick plates, reduction of porosity and monitoring the keyhole/molten metal behavior are very important issues to assure the high...

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  • JLA Vol:14 Iss:3 (Pulsed laser driven deposition of spattered molten particles and its application to the manufacturing of wear-resistant coatings)


    Authors:
    Toru Nagai
    Takashi Inoue
    Applied Laser Engineering Research Institute, 2085-16 Uenoyama, Fukasawa, Nagaoka 940-2135, Japan

    Hirofumi Shimura
    Mechanical Engineering Laboratory, Agency of Industrial Science and Technology, 1-2 Namiki, Tsukuba 305-8564, Japan


    In this article, we report on a new process for manufacturing metal coatings with submillimeter thickness by pulsed laser driven deposition of molten metal particles. The process of “laser spattering of molten particles” using a high pulse-energy laser is considered to be effective compared to the conventional physical vapor process based on vaporized ultrafine particle generati...

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  • JLA Vol:14 Iss:4 (Determining source size from diode laser systems)


    Authors:
    Wesley J. Marshall
    U.S. Army Center for Health Promotion and Preventive Medicine, Aberdeen Proving Ground, Maryland 21010-5403


    Although hazard classification is performed at predefined distances, the maximum permissible exposure (MPE) for extended-source diode lasers decreases as the distance from the laser increases. The MPE depends on the apparent angular subtense of the source, which is simply the magnified image of the emitting diode. Small diameter beams require special consideration.

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  • JLA Vol:14 Iss:4 (High-energy femtosecond pulsed laser micromachining of thin film deposited silicon in self-focused air medium)


    Authors:
    Yuanyuan Dong
    Pal Molian
    Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011

    Christian Zorman
    Mehran Mehregany
    Department of Electrical Engineering and Computer Science, Case Western Reserve University, Cleveland, Ohio 44106


    The ultrashort pulsed laser ablation of silicon wafers deposited with 1 μm thin film of SiC was performed in air medium using a 1 mJ, 120 fs, 800 nm Ti:sapphire laser, the objective being to determine the self-focusing capability of air to produce nanostructures. The effects of pulse energy, the number of pulses, pulse repetition rate and x–y translation speed on t...

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  • JLA Vol:14 Iss:4 (Interaction of the keyhole and weld pool in laser keyhole welding)


    Authors:
    John Dowden
    Department of Mathematics, University of Essex, Colchester, Essex CO4 3SQ, United Kingdom


    There are several components to the motion of the liquid material in the weld pool in laser keyhole welding. Observations have shown not only that it moves in the plane perpendicular to the axis of the laser, but also that it moves parallel to the laser beam. It has been recognized for many years that the motion in the direction perpendicular to the surface of the work piece is important in connection with arc welding; it has, however, received less detailed study in connection with keyhole welding. The possible mechanisms are reviewed from a mathematical standpoint and Maran...

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  • JLA Vol:14 Iss:4 (Penetration control in laser welding of sheet metal)


    Authors:
    S. Postma
    Netherlands Institute for Metals Research (NIMR), P.O. Box 5008, 2600 GA, Delft, the Netherlands

    R. G. K. M. Aarts
    Johan Meijer
    J. B. Jonker
    Faculty of Engineering, University of Twente, P.O. Box 217, 7500 AE Enschede, the Netherlands


    For economical reasons it is desirable to apply the highest possible speed during laser welding. Increasing the welding speed at a certain laser power might result in insufficient penetration of the weld. This work describes the design of a feedback controller, which is able to maintain full penetration in mild steel sheets. An optical detector, which is placed inside the Nd:Yttrium&ndash...

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  • JLA Vol:14 Iss:4 (Process study for laser-induced surface coloration)


    Authors:
    H. Y. Zheng
    G. C. Lim
    X. C. Wang
    J. L. Tan
    Gintic Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075

    James Hilfiker
    J. A. Woollam Company, Inc., 645 M Street, Suite 102, Lincoln, Nebraska 68508


    A KrF excimer laser beam is used to induce controllable and high-contrast colors on a stainless-steel surface under different processing conditions. The laser beam acts as a localized heating source that promotes the formation of semitransparent oxide films of varying thicknesses and morphologies on the sample surface. Ellipsometry and atomic force microscopy were employed to understand the laser-induce...

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  • JLA Vol:14 Iss:4 (Surface characteristics and corrosion behavior of laser surface nitrided NiTi shape memory alloy for biomedical applications)


    Authors:
    H. C. Man
    Z. D. Cui
    T. M. Yue
    Laser Processing Group, Advanced Manufacturing Technology Research Centre, Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Kowloon, Hung hom, Hong Kong


    Laser gas nitriding (LGN) has been applied to fabricate a TiN coating on the surface of NiTi alloy for the purpose of improving the surface properties. The microstructure, surface characteristics, and corrosion properties of the laser gas nitrided layer on NiTi alloy surface were investigated. The nickel release rate of the LGN specimen in Hanks’ solution was also investigated. The results of x-ray diffraction, x-ray photoelec...

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