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  • JLA Vol:15 Iss:2 (Antigalling and low friction properties of a laser processed Co-based material)

    D. H. E. Persson
    Duroc AB, Umeå, Sweden

    S. Jacobson
    S. Hogmark
    The Tribomaterials Group at Ångstro¨m Laboratory, Uppsala University, Sweden

    The antigalling and low friction properties of a CO2-laser processed Co-based material (Stellite 21) was investigated under high-load sliding conditions. Dry sliding tests were carried out at both room temperature and at 250 °C. The tests were performed by sliding two identical specimens against each other in a dedicated test. A low and stable friction coefficient at a level of about 0.20, and relatively independent on load and sliding speed, was obtained after a short runn...


  • JLA Vol:19 Iss:2 (Interaction of a focused laser beam and a coaxial powder jet in laser surface processing)

    O. O. Diniz Neto
    A. M. Alcalde
    Instituto de Fi´sica, Universidade Federal de Uberlaˆndia, Caixa Postal 593, CEP 38400-902, Uberlaˆndia MG, Brazil

    R. Vilar
    Instituto Superior Te´cnico and ICEMS, Av. Rovisco Pais, 1096-001 Lisboa, Portugal

    Laser cladding, laser alloying, and laser free-form manufacturing are promising techniques where a laser beam is frequently used in conjunction with a coaxial powder jet for surface treating or rapid manufacturing. In the present work, a computational model was developed and used to simulate several experimental setups in order to optimize the processing conditions. More specifically, t...


  • JLA Vol:23 Iss:2 (Experimental investigation of laser shock peening using femtosecond laser pulses)

    Dongkyun Lee
    Elijah Kannatey-Asibu
    Department of Mechanical Engineering, The University of Michigan, Ann Arbor, Michigan 48105-2125

    In this study, the feasibility of laser shock peening using ultrafast laser pulses was experimentally investigated. A top coating of zinc with a water confining layer was applied in the investigation. The zinc coating was used for the thermoprotective effect. A high numerical aperture (NA≅0.5) aspheric lens was used to minimize the optical breakdown of water. Microhardness measurements were made on the top surface of the shock peened specimen and compared with the original material hardness. The results provide useful insight on...


  • JLA Vol:7 Iss:3 (Laser beam surveying, refractive index measurements and the making of a 360° reflection hologram)

    David Foster
    Notre Dame High School, 596 South Second St., San Jose, California 95112, U.S.A.

    Triangulation measurements, using a laser to find the height of a room and of buildings, will be described first. This will be followed by triangulation and laser beam divergence measurements for range finding. The use of a hollow prism to hold liquids, whose refractive indicies are to be found, will then be described. The final topic will describe how a 360° reflection hologram was made at Notre Dame High School, utilizing three lasers and beam spreaders and four lasers and beam spreaders. The 360° hologram, made by a student, will be available for viewing.


  • JLA Vol:17 Iss:4 (Developments towards controlled three-dimensional laser forming of continuous surfaces)

    S. P. Edwardson
    E. Abed
    P. French
    G. Dearden
    K. G. Watkins
    Laser Group, Department of Engineering, The University of Liverpool, Liverpool L69 3GH, United Kingdom

    R. McBride
    D. P. Hand
    J. D. C. Jones
    A. J. Moore
    School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom

    There has been a considerable amount of work carried out on two-dimensional laser forming, using multipass straight line scan strategies to produce a reasonably controlled bend angle in a number of materials, including aerospace alloys. However, in order t...


  • JLA Vol:22 Iss:2 (Nd:YAG laser welding of titanium alloys using a directed gas jet)

    Jonathan Blackburn
    Laser Processing Research Centre, The University of Manchester, Manchester M60 1QD, United Kingdom

    Chris Allen
    Paul Hilton
    TWI Ltd., Granta Park, Abington, Cambridge CB21 6AL, United Kingdom

    Lin Li
    Laser Processing Research Centre, The University of Manchester, Manchester M60 1QD, United Kingdom

    The increasing utilization of titanium alloys in the aerospace industry, a direct result of socioeconomic pressures, has created the need for a production process which can produce high quality near-net-shape titanium alloy components. Keyhole laser welding is a joining technology which could be utilized for t...


  • 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¨rster Models of Fluorescence Waveforms)

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

    The author examined the precision of maximum‐likelihood‐derived, nonlinear least‐squared‐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‐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...


  • JLA Vol:26 Iss:1 (Two-dimensional simulation of laser ablation with 235 nanosecond pulses)

    Sousan Ghalamdaran
    Iranian National Centre for Laser Science and Technology (INLC), PO Box 14665-576 Tehran, Iran and Department of Physics, Amir Kabir University of Technology, PO Box 15875-4413 Tehran, Iran

    Parviz Parvin
    Department of Physics, Amir Kabir University of Technology, PO Box 15875-4413 Tehran, Iran

    Mohamad Javad Torkamany
    Jamshid Sabbagh Zadeh
    Iranian National Centre for Laser Science and Technology (INLC), PO Box 14665-576 Tehran, Iran

    A two-dimensional thermal model of nanosecond pulsed laser ablation is developed to describe the physical processes, the plasma absorption, the crater profile, and the temp...


  • JLA Vol:16 Iss:1 (Influence of surface preparation and process parameters on the porosity generation in aluminum alloys)

    A. Haboudou
    P. Peyre
    CLFA, avenue Prieur de la Côte d’or, 94114 Arcueil, France

    A. B. Vannes
    Ecole Centrale de Lyon, Ecully, France

    The 4 kW cw Nd:yttrium–aluminum–garnet laser welding of solid solution hardened A5083 (5% Mg) and precipitation-hardened A356 (7% Si) alloys, sensitive to porosity formation was carried out at different welding speeds, under He gas shielding, and for partial penetration conditions, on bead on plate configuration. The porosity formation was examined through observation and evaluation of weld beads, based on x-ray radiography inspection coupled with image analysis, and quantification of gas...



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