• JLA Vol:15 Iss:3 (Control of chaos in laser-induced vapor capillaries)

    M. H. Cho
    D. F. Farson
    Welding Engineering Department, The Ohio State University, Columbus, Ohio 43221

    J. I. Kim
    The Faculty of Marine Engineering, Mokpo National Maritime University, Mokpo, Chonnam 530-729, Korea

    Vapor capillaries associated with deep penetration laser welding (keyholes) are inherently unstable and it is well known that the bounded evolution of unstable modes of nonlinear dynamic systems can lead to complex fluctuations of state and/or output variables. In the case of keyholes, the magnitude of self-induced fluctuations is sometimes large enough to cause occasional closure (“collapse”) and trapping of voids in t...


  • JLA Vol:15 Iss:3 (Do <em>in vivo</em> terahertz imaging systems comply with safety guidelines?)

    Elizabeth Berry
    Gillian C. Walker
    Anthony J. Fitzgerald
    Academic Unit of Medical Physics and Centre of Medical Imaging Research, University of Leeds, Wellcome Wing, Leeds General Infirmary, Leeds LS1 3EX, United Kingdom

    N. N. Zinov’ev
    Martyn Chamberlain
    Institute of Microwaves and Photonics, University of Leeds, Leeds LS2 9JT, United Kingdom

    Stephen W. Smye
    Department of Medical Physics and Engineering, Leeds Teaching Hospitals NHS Trust, St. James’s University Hospital, Leeds LS9 7TF, United Kingdom

    Robert E. Miles
    Institute of Microwaves and Photonics, University of Leeds, Lee...


  • JLA Vol:15 Iss:3 (Experimental and numerical analyses of the mechanism for decreasing hydrogen-embrittlement sensitivity of aged Inconel 718 by laser surface annealing)

    Liufa Liu
    School of Materials Science and Engineering, Shanghai Jiao Tong University, Huashan Road 1954, Shanghai 200030, China

    Katsumi Tanaka
    Akio Hirose
    Kojiro F. Kobayashi
    Department of Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan

    Laser surface annealing (LSA) treatments were conducted to decrease the hydrogen embrittlement (HE) sensitivity of Inconel 718. Hydrogen was charged into the alloy by a cathodic-charging process. The LSA treatment significantly reduced the strength loss of the hydrogen-precharged notched specimen. Tensile tests and elasto–...


  • JLA Vol:15 Iss:3 (Hole drilling of Inconel 718 by high intensity pulsed ultraviolet laser)

    Qihong Wu
    Yurong Ma
    Jiansheng Jie
    Qingxuan Yu
    Yuan Liao
    Rongchuan Fang
    Department of Physics, Structure Research Laboratory, University of Science and Technology of China, Hefei, Anhui, 230026, People’s Republic of China

    Xiangli Chen
    Kelvin Wang
    GE Corporate Research and Development Shanghai Center, 421 Hongcao Road, Shanghai 200233, People’s Republic of China

    Holes were percussion drilled in Inconel 718 plates by a high intensity pulsed ultraviolet laser (266 and 355 nm) with 8 ns pulse width. It showed that shortening the laser wavelength resulted in thinner recas...


  • JLA Vol:15 Iss:3 (Preparation of polyperinaphthalenic organic semiconductive nanoparticles by excimer laser ablation and their application to optic and electronic devices)

    Satoru Nishio
    Hiroshi Fukumura
    Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Sendai, Miyagi 980-8578, Japan

    Kazuyuki Tamura
    Jun Murata
    Junko Kitahara
    Teruhiko Kan
    Akiyoshi Matsuzaki
    Department of Chemistry for Materials, Faculty of Engineering, Mi’e University, 1515 Kamihama-cho, Tsu, Mi’e 514-8507, Japan

    Nobuo Ando
    Yukinori Hato
    Kanebo LTD., 3-1, Kanebo-cho, Hofu, Yamaguchi 747-0823, Japan

    Polyperinaphthalene (PPN) nanoparticles are prepared by excimer laser ablation (ELA) of a 3, 4, 9, 10-perylenetetracarbox...


  • JLA Vol:15 Iss:3 (Process characteristics and effects of gas- and water-atomized stainless steel powders in laser-based rapid tooling)

    Andrew J. Pinkerton
    Lin Li
    Department of Mechanical, Aerospace, and Manufacturing Engineering, Laser Processing Research Centre, UMIST, P.O. Box 88, Sackville Street, Manchester M60 1QD, United Kingdom

    In rapid tooling using the direct laser deposition process and stainless steel materials, only powders prepared using the gas-atomization method have been used because of their presumed superior flow characteristics. In this article, the use of water-atomized powder is investigated by comparing the behavior of the two types of 316 L powders, deposited using a CO2 laser and coaxial head. Results show little difference in the pneumatic conveyance of the po...


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

    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 ...


  • JLA Vol:15 Iss:3 (Three-dimensional finite element modeling of laser cladding by powder injection: Effects of powder feedrate and travel speed on the process)

    Ehsan Toyserkani
    Amir Khajepour
    Steve Corbin
    University of Waterloo, Department of Mechanical Engineering, Waterloo, Ontario N2L 3G1, Canada

    This article addresses a novel three-dimensional transient finite element model of the laser cladding by powder injection process. The proposed model can predict clad geometry as a function of time and process parameters including beam velocity, laser power, powder jet geometry, laser pulse shaping, and material properties. In the proposed method, the interaction between powder and melt pool are assumed to be decoupled and as a result, the melt pool boundary is first obtained in the absence of powder spray....


  • JLA Vol:15 Iss:4 (Condition monitoring and lifetime estimation of a CO<sub>2</sub> laser)

    P. Koomsap
    V. V. Prabhu
    N. I. Shaikh
    J. T. Schriempf
    J. H. McDermott
    The Pennsylvania State University, University Park, Pennsylvania 16802

    Lasers are being successfully applied to a variety of manufacturing processes, including cutting, welding, cladding, and free forming. Part of their success is due to the high quality beam that is directly related to the condition of components involved in the lasing process. However, maintaining the requisite beam quality requires frequent and time-consuming intervention by maintenance operators, specifically, for dismounting, inspection, servicing, and reassembly. Preventive maintenanc...


  • JLA Vol:15 Iss:4 (Design and performance of multilevel phase fan-out diffractive optical elements for laser materials processing)

    Keiji Fuse
    Takayuki Hirai
    Toshihiko Ushiro
    Takeshi Okada
    Kenichi Kurisu
    Keiji Ebata
    Itami R&D Laboratories, Sumitomo Electric Industries, Ltd., 1-1-3 Shimaya, Konohana-ku, Osaka 554-0024, Japan

    A multilevel phase fan-out diffractive optical element (DOE) has been developed and introduced into various kinds of laser materials processing such as drilling, cutting, welding, and soldering. The larger the number of arrayed spots the DOE generates on the surface of the workpiece, the more sensitive the intensity uniformity of the spots becomes to fabrication errors, which are deviations between designed and fabric...