• JLA Vol:25 Iss:5 (Numerical and experimental study of the effect of groove on plasma plume during high power laser welding)


    Authors:
    Cai Yan
    Xie Wen-Jing
    Wu Yue
    Sun Da-Wei
    Wu Yixiong
    Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China and Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai 200240, China


    The influence of groove on the static feature and dynamic behavior of plasma plume during high power CO2 laser welding process was studied using a hydrodynamic three-dimensional model and corresponding experiments. The temperature, composition, and velocity of plasma plume along the incident path of laser beam were computed. The static morphology of plasma plume was analyzed through both models ...

    $25.00

  • JLA Vol:24 Iss:4 (Femtosecond laser-induced periodic surface structures)


    Authors:
    J. Bonse
    J. Kru¨ger
    S. Ho¨hm
    A. Rosenfeld
    Array


    The formation of laser-induced periodic surface structures (LIPSS) in different materials (metals, semiconductors, and dielectrics) upon irradiation with linearly polarized fs-laser pulses (τ ∼ 30–150 fs, λ ∼ 800 nm) in air environment is studied experimentally and theoretically. In metals, predominantly low-spatial-frequency-LIPSS with periods close to the laser wavelength λ are observed perpendicular to the polarization. Under specific irradiation conditions, high-spatial-frequency-LIPSS with sub-100-nm spatial periods (∼λ/10) can be gene...

    $25.00

  • JLA Vol:5 Iss:1 (Single Pass Laser Cutting of Polymers)


    Authors:
    R. Patel
    G. Baisch
    IBM Corporation, GTD, Hopewell Junction, New York


    Since the early 1980's discovery of the ability of excimer lasers to etch polymers precisely and cleanly with minimal thermal damage, excimer lasers have been used actively in the semiconductor industry for various manufacturing processes. In the present study a process for laser cutting of polymers has been investigated. A laser beam of controlled cross‐sectional shape is imaged onto a polymer surface. The geometry of the cutting path is controlled by precise movement of a sample mounted on a 2‐axis computer controlled work stage. This type of a process is useful for applications ...

    $25.00

  • 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.

    $25.00

  • JLA Vol:18 Iss:4 (Cutaneous sensation threshold for 3.8 μm radiation from a short duration pulsed laser on the calves of human subjects: A pilot study)


    Authors:
    Thomas E. Johnson
    Michael J. Roy
    Department of Environmental and Radiological Health Sciences, Colorado State University, 1618 Campus Delivery, Fort Collins, Colorado 80528 and Department of Medicine, School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, Maryland 20814


    The objective of this study was to determine the threshold for sensing a 3.8 μm laser on the skin. The identification of the skin sensation threshold for invisible lasers is useful in providing scientific guidance to the safety community regarding accidental skin exposures. Knowledge of the level of sensation of lasers might be used to s...

    $25.00

  • JLA Vol:1 Iss:3 (Laser Welding of Plastics in Low and High Gravity Environments)


    Authors:
    R. E. Mueller
    W. W. Duley
    CRESS and Laser Processing Laboratory, York University, Toronto, Ontario, Canada M3J 1P3

    S. MacLean
    M. Garneau
    B. Tryggvason
    Canadian Astronaut Office, National Research Council, Ottawa, Ontario, Canada K1A 0R6

    W. F. J. Evans
    Atmospheric Environment Service, 4905 Dufferin Street, Downsview, Ontario M3H 5T4


    Initial results of a series of laser processing experiments performed under the micro‐gravity conditions supplied by NASA's KC‐135 aircraft are presented. Weld morphologies of polypropylene and polyethylene were obtained under both hyper‐ and hy...

    $25.00

  • 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)


    Authors:
    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...

    $25.00

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


    Authors:
    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...

    $25.00

  • JLA Vol:15 Iss:3 (Steady-state laser cutting modeling)


    Authors:
    Ce´dric Mas
    Re´my Fabbro
    CLFA, 16 bis Avenue Prieur de la Côte d’Or, 94114 Arcueil Cedex, France

    Yannick Goue´dard
    OPTIS, ZE la Farlède, BP 275, 83078 Toulon Cedex 9, France


    We present a global self-consistent model of the laser cutting process where we have taken into account the main parameters of the process that are the laser beam intensity distribution, the thermal phenomena controlling the melt parameters, the fluid, both cutting gas and melt hydrodynamics, and the local equilibrium of the geometry of the cutting front. This steady state approach provides us with different fluid velocities, surface ...

    $25.00

  • JLA Vol:19 Iss:3 (Single-Pass and Multi-Pass Laser Cutting of Si&ndash;SiC: Assessment of the Cut Quality and Microstructure in the Heat Affected Zone)


    Authors:
    F. Quintero
    J. Pou
    F. Lusquin˜os
    A. Riveiro
    M. Pe´rez-Amor
    Departamento Fi´sica Aplicada, E.T.S. Ingenieros Industriales, University de Vigo, 36310 Vigo, Spain

    A. J. S. Fernandes
    Department of Physics, University of Aveiro, 3810-193 Aveiro, Portugal


    Experimental investigations on the laser cutting of thick silicon infiltrated silicon carbide (Si–SiC) elements are presented. Si–SiC is a fully dense ceramic composite with high hardness and chemical and thermal stability, which makes it a valuable material in severe conditions. However, machining is still a challenging task. A...

    $25.00

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