• JLA Vol:19 Iss:1 (Three-dimensional numerical approach for geometrical prediction of multilayer laser solid freeform fabrication process)


    Authors:
    Masoud Alimardani
    Ehsan Toyserkani
    Jan P. Huissoon
    Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada


    This article presents the development of a three-dimensional numerical method for predicting transient geometrical and thermal characteristics of multilayer laser solid freeform fabrication as a function of process parameters and material properties. In the proposed method, the thermal domain is numerically obtained, assuming the interaction between the laser beam and powder stream is to be decoupled. Once the melt pool boundary is obtained, the physical domain is discretized in a cross-se...

    $25.00

  • JLA Vol:9 Iss:4 (The application of external feedback in the laser spectroscopy of nonlinear media)


    Authors:
    B. V. Anikeev
    D. V. Sin'ko
    Department of Laser Physics, Volgograd State University, 2‐aya Prodolnay 30, Volgograd 400 062, Russia


    A new spectroscopic technique to gain information on the nonlinear constants of optical materials is presented. This technique is made possible due to the point that the application of an external controlled negative feedback (CNF) circuit to an intracavity nonlinear cell results in the generation of extended boundaries of the stability for the laser beam. This effect is analyzed using a semiclassical set of equations that govern laser oscillation. Measurements are made on systems containing either an instantaneous CNF circuit o...

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  • JLA Vol:17 Iss:3 (Laser beam analysis in direct metal deposition process)


    Authors:
    Huan Qi
    Jyoti Mazumder
    Center for Laser Aided Intelligent Manufacturing, Department of Mechanical Engineering, The University of Michigan, Ann Arbor, Michigan 48109

    Larry Green
    Spiricon, Inc., Logan, Utah 84341

    Gary Herrit
    II-VI, Inc., Saxonburg, Pennsylvania 16056


    The quality of a laser beam profile and its stability play fundamental roles in laser material processing. Beam reflections may dramatically affect the beam quality under certain material processing conditions. In this study, experiments were carried out to examine the variations of the continuous wave CO2 laser beam profile during the direct metal...

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  • JLA Vol:4 Iss:1 (Combustion‐Assisted Laser Cutting of a Difficult‐to‐Machine Superalloy)


    Authors:
    P. A. Molian
    M. Baldwin



    In laser cutting, the largest single application of lasers in manufacturing, the assist gas plays an important role in affecting the cutting performance. The assist gas is usually oxygen or an inert gas. In this work a mixture of acetylene and oxygen was employed to create combustion reactions during CO2 laser cutting that enabled an improvement in the cutting speed, and cut quality of a difficult‐to‐machine superalloy. A comparison with laser cutting of a plain carbon steel under identical conditions was also made to determine the usefulness of combustion energy. Results indicate that both cutting speed and qual...

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  • JLA Vol:21 Iss:4 (Contributions of Charles Townes’ research to nonlinear optics)


    Authors:
    Elsa Garmire
    Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire 03755, USA


    Nonlinear optics was profoundly influenced by early work of Charles Townes and his group at Massachusetts Institute of Technology from 1961 to 1967. His foundational contribution was the realization that coherent molecular oscillations resulted from stimulated Raman scattering, leading to the introduction of stimulated Brillouin scattering. Self-trapping of light beams and self-steeping of light pulses in nonlinear materials were two other important innovations. Some applications today of these early ideas are outlined.

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  • JLA Vol:25 Iss:1 (Implementation of a novel scan localization system for wireless sensor networks)


    Authors:
    K. Sun
    W. Huang
    Sachula Meng
    Y. Xiao
    M. T. Wang
    Z. Xiao
    Inner Mongolia University, Hohhot 010021, China


    A novel localization scheme called laser beam scan localization by combining grid and light (laser) with mobile localization policy for wireless sensor networks is designed. The scheme utilizes a moving location assistant (LA) with a laser beam, through which the deployed area is scanned. The LA sends identities to unknown nodes to obtain the locations of sensor nodes. High localization accuracy can be achieved without the aid of expensive hardware on the sensor nodes, as required by other localization systems...

    $25.00

  • JLA Vol:23 Iss:4 (Evaluation of the bone repair in defects grafted with hydroxyapatite and collagen membrane combined with laser therapy in rats)


    Authors:
    Marcelo Rodrigues da Cunha
    Luanda de Abreu Figueira
    Joa˜o Paulo Mardegan Issa
    Ricardo Alexandre Junqueira Calzzani
    Daniele Cristina do Prado Ribeiro
    Amilton Iatecola
    Mariane Silva Pettian
    Array


    Bone regeneration is the result of cellular events such as osteogenesis and neovascularization. However, implantation of autogenous grafts may be necessary in cases of bone mass loss due to high impact trauma. The disadvantages of the latter approach include morbidity of the donor area. Biomaterials represent an alternative for bone restoration. The most widely used compounds are collagen or hydroxyapat...

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  • JLA Vol:15 Iss:4 (Welding of thick austenitic stainless steel using Nd:yttrium–aluminum–garnet laser with filler wire and hybrid process)


    Authors:
    Tommi Jokinen
    Miikka Karhu
    VTT Industrial Systems, P.O. Box 17021, FIN 53851 Lappeenranta, Finland

    Veli Kujanpa¨a¨
    Lappeenranta University of Technology, P.O. Box 20, FIN 53851 Lappeenranta, Finland


    Autogenous laser welding has shown many advantages over traditional welding methods in numerous applications. However, there could be even more applications, but due to the power levels of present high power lasers, depth of penetration is limited. One way to overcome this limitation is to use multipass laser welding, in which a narrow gap and a filler wire are applied. By this process thick sections can be welded with a smaller heat inpu...

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  • JLA Vol:6 Iss:2 (CO<sub>2</sub> shielding gas effects in laser welding mild steel)


    Authors:
    D. H. Abbott
    C. E. Albright



    The most widely used shielding gases for laser welding of steels are helium and argon. Helium produces significantly more penetration than argon in penetration&hyphen;mode laser beam welding. Another gas that has been proposed as an alternative to these inert gases is carbon dioxide. The benefits of using carbon dioxide as a shielding gas for laser welding are that it costs less than helium and argon and that it provides nearly the same penetration as helium. The major drawback to its use as a shielding gas for mild steel is that it can cause porosity and other weld discontinuities. In this investigation helium and carbon dioxide were...

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  • JLA Vol:19 Iss:4 (Experimental observation of keyhole shapes in the laser welding of aluminum blanks)


    Authors:
    B. J. Aalderink
    Netherlands Institute for Metals Research, P.O. Box 217, 7500 AE Enschede, The Netherlands

    R. G. K. M. Aarts
    University of Twente, Laboratory of Mechanical Automation, P.O. Box 217, 7500 AE Enschede, The Netherlands

    D. F. de Lange
    Netherlands Institute for Metals Research, P.O. Box 217, 7500 AE Enschede, The Netherlands

    J. Meijer
    University of Twente, Laboratory of Mechanical Automation, P.O. Box 217, 7500 AE Enschede, The Netherlands


    A camera-based in situ monitoring system for the Nd:yttrium–aluminum–garnet laser keyhole welding process of aluminium has been developed. The...

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