• JLA Vol:20 Iss:2 (Laser bioeffects associated with ultrafast lasers: Role of multiphoton absorption)

    Randolph D. Glickman
    Department of Ophthalmology, University of Texas Health Science Center, San Antonio, Texas 78229-3900

    Thomas E. Johnson
    Department of Environmental and Radiological Health Sciences, Colorado State University, Ft. Collins, Colorado 80523

    Gary D. Noojin
    David J. Stolarski
    Michael L. Denton
    Northrup Grumman Warfighter and Applications Department, San Antonio, Texas 78228-1330

    Neeru Kumar
    Department of Ophthalmology, University of Texas Health Science Center, San Antonio, Texas 78229-3900

    Benjamin A. Rockwell
    US Air Force Research Laboratory, AFRL/HEDO, Brooks City...


  • JLA Vol:8 Iss:6 (A modeling study on the influence of pulse shaping on keyhole laser welding)

    P. S. Mohanty
    A. Kar
    J. Mazumder

    A theoretical analysis describing the effects of pulse shaping on keyhole laser welding is presented. Calculation of the keyhole profile and melt pool dimensions was performed by the balancing of surface forces and energy at the liquid‐vapor and solid‐liquid interfaces in three dimensions. The effect of temporal pulse shape on weld dimensions has been examined over a range of power densities, pulse times and pulse frequencies. Several pulse types (e.g., top‐hat, Gaussian, ramp‐up and ramp‐down pulses) have been considered. Pulse shaping showed significant effect on the weld dimensio...


  • JLA Vol:1 Iss:4 (Recent Developments in Laser Melt/Particle Injection Processing)

    K. P. Cooper
    Geo‐Centers, Inc., 10903 Indian Head Highway, Fort Washington, Maryland 20744

    P. Slebodnick
    Naval Research Laboratory, Washington, D.C. 20375.

    Investigations into crack formation in particle injected surfaces and into microstructural evolution during cladding were some of the recent developments in laser melt/particle injection processing. Both surface modification techniques involved blowing powder particles into a melt pool formed by a laser beam. When the particulate materials were metal carbides composite surface layers were formed and the thermal stresses that developed during cooling of the carbide injected layer resulted in th...


  • JLA Vol:14 Iss:3 (Effects of laser welding parameters on magnetic materials with the aid of a mechatronic measuring system)

    Hussein A. Abdullah
    School of Engineering, University of Guelph, Guelph, Ontario N1G 2W1, Canada

    Chris R. Chatwin
    School of Engineering, University of Sussex, Brighton BN1 9QT, United Kingdom

    This article reports results from an experimental investigation into laser welding of ferromagnetic material, which, for example, is of interest to the European Space Agency. The effects of laser welding power and translation velocities on the magnetism of ferromagnetic materials were studied. An automated system using a Hall effect transducer was constructed to measure the magnetic field transverse to the laser weld before welding, immediately after welding and thr...


  • JLA Vol:18 Iss:3 (Femtosecond laser production of metal surfaces having unique surface structures that are broadband absorbers)

    Neha Singh
    Dennis R. Alexander
    John Schiffern
    David Doerr
    Center for Electro Optics and Electrical Engineering Department, University of Nebraska-Lincoln, 248 N WSEC, Lincoln, Nebraska 68588-0511

    Femtosecond laser induced modification of surface structure and the optical properties of metals are studied. A Ti:sapphire femtosecond laser is used for ablating bulk aluminum 2024 T3 alloy and highly pure neutron activation quality gold metal samples at different laser irradiation parameters. The ablation parameters are optimized for the two metals to form a low reflection surface in the wavelength range of 0.3–50 μm. “Blac...


  • JLA Vol:9 Iss:2 (Kinematic compensation of repetitive errors for non‐circular laser shaping)

    P. Sheng
    K. Liu
    Department of Mechanical Engineering, University of California, Berkeley, CA, U.S.A.

    This paper presents an approach for kinematic compensation of the laser shaping process which is capable of achieving improved dimensional accuracy for non‐circular profiles. In this approach, a plug‐in repetitive controller is added into the existing position servo loop to improve tracking of the desired sinusoidal trajectory and subsequently reduce tracking errors. The effect of tracking errors on different dimensional error modes in the non‐circular shaping process is identified. Simulation models are developed for testing the performance o...


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  • JLA Vol:17 Iss:1 (Thermodynamics and laser material processing)

    W. W. Duley
    Physics Department, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1

    In many laser applications it is the conversion of photon energy to heat that drives the process. Heat transfer theory accurately describes the effects produced, and other aspects of thermodynamics need not generally be considered explicitly. The highly nonequilibrium nature of laser materials processing operations can usually be ignored once the heat transfer problem is defined. However, “equilibrium” is a concept that is basic to thermodynamics, and so it is useful to examine this concept in the context of traditional laser materials processing applications. Some of the ass...


  • JLA Vol:21 Iss:2 (Visualization of refraction and attenuation of near-infrared laser beam due to laser-induced plume)

    Yousuke Kawahito
    Keisuke Kinoshita
    Naoyuki Matsumoto
    Seiji Katayama
    Joining and Welding Research Institute (JWRI), Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan

    This study was performed to obtain a fundamental knowledge of the interaction between a near-infrared laser beam and an induced plume during welding. The plume was characterized by spectroscopy, and the effect and mechanism of the laser-induced plume on the refraction and/or attenuation were investigated by high-speed video observation of the plume and the probe laser, and power meter measurement of the fiber probe laser beam of 1090 nm wavelength which pa...


  • JLA Vol:1 Iss:1 (Endoholography in Medicine)

    Marc D. Friedman
    Hans I. Bjelkhagen
    Max Epstein
    Biomedical Engineering, Northwestern University, Evanston, Illinois



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