• JLA Vol:18 Iss:1 (Three-dimensional analytical model on laser-powder interaction during laser cladding)

    Yan-Lu Huang
    Jian Liu
    Nai-Heng Ma
    Jian-Guo Li
    School of Materials Science and Engineering, Shanghai Jiaotong University, Shanghai, China 200030

    To compute the attenuation of laser power by powder stream and the temperature distribution of the powder particles arriving at different sites on the surface of the workpiece, a three-dimensional analytical model was presented based on Lambert-Beer theorem, Mie’s theory, and heat equilibrium principle. The obtained results revealed that for a given stream spread and speed of powder particles, the laser intensity distribution of laser spot and the temperature distribution of the powder part...


  • JLA Vol:7 Iss:1 (Development of laser finishing for non‐circular profiles)

    Ko‐Wang Liu
    Paul S. Sheng
    Department of Mechanical Engineering, University of California, Berkeley, CA 94720‐1740, U.S.A.

    A laser‐based technique for finishing of non‐circular cylindrical parts is presented. In this process, the frequency characteristics of a desired non‐circular shape is extracted from a CAD through a Fast Fourier Transform algorithm and implemented through a CO2 laser machining system. A galvanometer‐based scanner is used in the process to achieve programmable beam trajectories and high‐speed finishing. An error estimation scheme can be developed to determine the final dimensional erro...


  • JLA Vol:16 Iss:2 (High-power CO<sub>2</sub> laser design &ldquo;from resonator end mirror to cutting lens focal point&rdquo;)

    David Toebaert
    HACO NV, Oekenestraat 120, 8800 Rumbeke, Belgium

    Wybo Wagenaar
    Infinite Simulation Systems BV, Lange Bunder 3, 4854 MB Bavel, Netherlands

    An algorithm is derived that allows calculating all optical parameters relevant to the design of a high-power CO2 laser, taking into account the practical needs of a flying-optics type of laser cutting machine. The novelty of the approach taken is that the resonator and the beam delivery optics are treated simultaneously, which allows for greater flexibility in design. To begin with, the often-used optical configuration of a stable resonator combined with a beam expander for collimation is mod...


  • JLA Vol:20 Iss:3 (Investigation of femtosecond laser induced thermal ablation of polyethylene)

    Andrew J. Lee
    Judith M. Dawes
    Michael J. Withford
    Centre of Ultrahigh-bandwidth Devices for Optical Systems (CUDOS) and MQPhotonics Research Centre, Department of Physics, Macquarie University, 2109 NSW, Australia

    We present a novel method for profiling high aspect ratio and undercut laser drilled holes using sacrificial layers. This profiling method is used to compare and contrast laser ablation of polyethylene films under exposure to ultraviolet (266 nm) and near-infrared (800 nm) radiation from an ultrafast, femtosecond laser. We find that ultraviolet femtosecond pulsed laser processing of this polymer exhibits similar characteristics to...


  • JLA Vol:9 Iss:3 (Experimental study of cutting thick aluminum and steel with a chemical oxygen&ndash;iodine laser using an N<sub>2</sub> or O<sub>2</sub> gas assist)

    David L. Carroll
    James A. Rothenflue

    A chemical oxygen–iodine laser (COIL) was used to cut aluminum and carbon steel. Cut depths of 20 mm in aluminum and 41 mm in carbon steel were obtained using an N2 gas assist and 5–6 kW of power on target. The same laser at the same power level produced a cut depth of 65 mm in carbon steel with an O2 gas assist; a low quality cut to a depth of nearly 100 mm in carbon steel was also demonstrated. These data are compared with existing COIL and CO2 laser cutting data. COIL cuts carbon steel and stainless steel at approximately the same rate. For a given cut depth, power and spot size...


  • JLA Vol:4 Iss:2 (Dynamic Laser Doppler Velocimetry on Solid Surfaces)

    Milind M. Rajadhyaksha
    Warren H. Stevenson
    Applied Optics Laboratory, School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907, U.S.A.

    This paper presents the results of a detailed analytical and experimental investigation into the accuracy of a differential laser Doppler velocimeter (LDV) for dynamic, solid surface velocity measurements made over very short averaging times on the order of one millisecond. Accuracy limitations are derived, along with operating conditions and signal processing considerations needed to optimize LDV performance. An experiment is described which demonstrates the use of an LDV to instantaneously and accurate...


  • JLA Vol:16 Iss:4 (Laser assisted cleaning of oxide films on SUS409 stainless steel)

    H. Guo
    Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802

    R. Martukanitz
    Applied Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802

    T. DebRoy
    Department of Materials Science and Engineering, The Pennsylvania State Univeristy, University Park, Pennsylvania 16802

    Laser assisted cleaning of oxide films on SUS409 stainless steel plates was studied both experimentally and theoretically. The highly oxidized surfaces with oxide scales of about 25 μm thickness were irradiated with Q-switched pulsed Nd:yttritium–aluminu...


  • JLA Vol:21 Iss:2 (Partial growth of crack in laser scribing of glass)

    Koji Yamamoto
    Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565–0871, Japan

    Noboru Hasaka
    Hideki Morita
    Mitsuboshi Diamond Industrial Co., Ltd., 1-4-37 Minami-kaneden, Suita, Osaka 564–0044, Japan

    Etsuji Ohmura
    Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565–0871, Japan

    The scribing of glass by a CO2 laser is much more effective compared to the conventional mechanical technology in use because the strength of the cut glass is improved since microcracks and particles along the cut edge are lessened. However, the crack depth of ...


  • JLA Vol:9 Iss:6 (Amendments to the Center for Devices and Radiological Health Federal Performance Standard for laser products)

    Jerome E. Dennis
    Center for Devices and Radiological Health, Food and Drug Administration, Rockville, MD, U.S.A.

    Federal law requires that all laser products that are imported into or introduced into commerce in the United States comply with the performance standard published in the Code of Federal Regulations (CRF), Title 21, Parts 1040.10 and 1040.11, administered by the Center for Devices and Radiological Health (CDRH), US Food and Drug Administration. Although it contains somewhat different requirements for hazard classification, engineering controls and labeling, the ANSI Z136.1 standard defers to the CDRH standard. The CDRH standard became effective in August, 1976 and ...


  • JLA Vol:3 Iss:2 (Precision Limits of the Estimation of the Parameters of Fo&uml;rster Models of Fluorescence Waveforms)

    L. Jonathan Dowell
    Los Alamos National Laboratory, Los Alamos, NM 87545

    The author examined the precision of maximum&hyphen;likelihood&hyphen;derived, nonlinear least&hyphen;squared&hyphen;error algorithms that are suitable for laboratory implementation and that estimate the parameters of Fo¨rster models of fluorescence. The estimation precision for these parameters is limited by inherent noise in the fluorescence&hyphen;waveform measurement. This paper examines the Fo¨rster model and its recent applications and discusses parameter estimations for models of energy transfer by different wavefunction interactions. It presents the results of Monte Carlo simulation studi...



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