• JLA Vol:9 Iss:3 (High power laser welding in hyperbaric gas and water environments)


    Authors:
    G. J. Shannon
    W. McNaught
    W. F. Deans
    J. Watson



    A hyperbaric laser welding facility has been constructed and the feasibility of high power CO2 and Nd:YAG laser welding in both high pressure gas and water environments, to simulated water depths of 500 m, has been established. From initial trials on welding through water at atmospheric pressure, it was found that the different absorption characteristics of water to 10.6 μm (CO2 laser) and 1.06 μm (Nd:YAG laser) radiation proved crucial. The Nd:YAG laser was totally unsuitable as the beam was largely diffused in the water, whereas the CO2 beam was rea...

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  • JLA Vol:4 Iss:2 (A Systematic Method for the Design of a Multivariable Controller Actuating Power and Speed during a CO<sub>2</sub> Laser Surface Treatment)


    Authors:
    F. Bataille
    J. M. Cerez
    D. Kechemair



    Temperature control systems actuating laser power and scanning velocity during laser surface hardening have already been presented. This paper exposes a systematic method for the design of a multivariable Linear Quadratic Gaussian controller adapted to this laser treatment. The preliminary identification step and the controller design are included. This corrector insures a better regulation and the generality of the method hopefully allows an easier adaptation to other laser treatments, materials or absorbing coatings.

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  • JLA Vol:14 Iss:3 (Assessment of laser Doppler perfusion imager&rsquo;s <em>in vivo</em> reliability: Can it be used for a prospective analysis?)


    Authors:
    Antonella Caselli
    Array

    Damanpreet Singh Bedi
    Colleen O’Connor
    Chirag Shah
    Aristidis Veves
    Joslin–Beth Israel Deaconess Foot Center, Department of Surgery, and Microcirculation Laboratory, Beth Israel–Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts


    The aim of this study was to assess the reliability of the laser Doppler perfusion imager (Lisca PIM 1.0; Lisca development, Linkoping, Sweden) for longitudinal analysis. We measured the skin blood flow under a biological zero condition at the forearm level in 84 patients enrolled in a 12 week prospective interventional trial. Sin...

    $25.00

  • JLA Vol:18 Iss:4 (Aluminum alloy welding by using a high power direct diode laser)


    Authors:
    N. Abe
    M. Tsukamoto
    Joining and Welding Research Institute, Osaka University, 11-1, Mihogaoka, Ibaraki, Osaka 567-0047, Japan

    K. Maeda
    K. Namba
    Research and Development Center, Sumitomo Light Metal Industries, Ltd., 3-1-12 Chitose, Minato-ku, Nagoya 455-8670, Japan

    J. Morimoto
    School of Science and Engineering, Kinki University, 3-4-1, Kowakae, Higashiosaka, Osaka 577-8502, Japan


    Aluminum alloys are the focus of increasing attention from the automobile industry because of their light weight, high formability, and easy recyclability. In this report, a 4 kW high power direct diode laser was used to exami...

    $25.00

  • JLA Vol:23 Iss:3 (Spatter in laser welding)


    Authors:
    A. F. H. Kaplan
    J. Powell
    Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden


    Spatter, the ejection of melt from a weld pool, is a major problem whenever it occurs in a welding process. The ejection of droplets from the weld metal results in a weld with underfill, undercuts, craters, blowholes, or blowouts—all of which can have a detrimental effect on the mechanical properties of the weld. This paper presents a systematic description of the different types of spatter phenomena which occur during laser welding. A categorization system is proposed to facilitate the comparison and combination ...

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  • JLA Vol:6 Iss:1 (Mass transport during laser welding of stainless steels and alloys used by US Navy)


    Authors:
    Anand J. Paul
    Parwaiz A. A. Khan
    Manufacturing and Materials Division, Concurrent Technologies Corporation, 1450 Scalp Avenue, Johnstown, PA 15904, U.S.A.


    Lasers, though developed only about a quarter century ago, are now being routinely used in the automotive, aerospace and other industries to produce superior quality, high&hyphen;speed autogenous welds with narrow heat&hyphen;affected zones in a number of alloys. However, they cannot at present be used to successfully weld certain important structural alloys due to a change in weld composition resulting from selective mass transport of certain alloying elements from the laser&hyphen;melted region. The loss of a...

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  • JLA Vol:17 Iss:1 (Fracture control of unsupported ceramics during laser machining using a simultaneous prescore)


    Authors:
    A. E. Segall
    G. Cai
    R. Akarapu
    A. Romasco
    Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, Pennsylvania 16802

    B. Q. Li
    Department of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164


    While lasers offer many advantages when machining ceramics, costly premature fractures and related damage is the tradeoff often faced by manufacturers. This tradeoff is especially apparent for higher-speed machining of complex shapes where traditional “nail-bed” supports are not always practical. To help overcome these problems, re...

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  • JLA Vol:21 Iss:3 (Laser welding of galvanized DP980 steel assisted by the GTAW preheating in a gap-free lap joint configuration)


    Authors:
    Shanglu Yang
    Radovan Kovacevic
    Center for Advanced Manufacturing, Southern Methodist University, Dallas, Texas, USA 75205


    With the increasing need for reducing the vehicle’s weight, improving fuel efficiency and safety, as well as the corrosion resistance, more and more galvanized high-strength steels have been used in the automotive industry. However, the successful laser welding of galvanized steels in gap-free lap joint configuration is still a big challenge. The high-pressurized zinc vapor is readily developed at the interface of the two metal sheets due to the lower boiling point of zinc (around 906 °C) than the melting point of steel (over 13...

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  • JLA Vol:8 Iss:2 (Recent progress in laser surface treatment: <emph type="4">II</emph>. Adopted processing for high efficiency and quality)


    Authors:
    W. Bloehs
    B. Gru¨nenwald
    F. Dausinger
    H. Hu¨gel
    Institut fu¨r Strahlwerkzeuge, Universita¨t Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart, Germany


    In Part I of this contribution, energy coupling and transport mechanisms were considered in detail. The second part concentrates on the effect of the spatial distribution of the energy in the laser beam, which will be discussed in connection with applications of laser surface technologies. Along these lines, a variety of beam shaping facilities is presented for laser hardening and cladding. Their purpose is to adapt the irradiated area to the workpiece ge...

    $25.00

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