• JLA Vol:16 Iss:4 (Microstructural aspects of laser dissimilar welds of hard metals to steels)


    Authors:
    A. Costa
    IDMEC, Av. Rovisco Pais, 1049-001 Lisboa, Portugal

    L. Quintino
    IDMEC, Av. Rovisco Pais, 1049-001 Lisboa, Portugal and Instituto Superior Te´cnico, Secc¸a˜o de Tecnologia Mecaˆnica, Av. Rovisco Pais, 1049-001 Lisboa, Portugal

    R. M. Miranda
    IDMEC, Av. Rovisco Pais, 1049-001 Lisboa, Portugal and Universidade Aberta, R. Escola Polite´cnica 147, 1269-001 Lisboa, Portugal


    Laser beam welding has been widely used in industry in the past decade. Recently, applications in dissimilar welds involving hard metals have been investigated. Hard metals are commonly used in tool manufacturing and this application...

    $25.00

  • JLA Vol:21 Iss:1 (Local susceptibility of the retina, formation and duration of afterimages in the case of Class 1 laser products, and disability glare arising from high-brightness light emitting diodes)


    Authors:
    Hans-Dieter Reidenbach
    Cologne University of Applied Sciences, Research Laboratory on Medical Technology and Non-Ionizing Radiation, Betzdorfer Str 2, 50679 Koeln, Germany


    According to the new European Directive on Artificial Optical Radiation, the employer has to determine the exposure and the assessment of risks and in addition, he shall give particular attention to any indirect effects, such as temporary blinding, when carrying out the risk assessment. Up to now, secondary effects such as temporary blinding have not been regarded in safety standards and there exist but a few data on this topic as far as modern artificial high-brightness (HB) light sources are concerned. Te...

    $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...

    $25.00

  • 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...

    $25.00

  • 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...

    $25.00

  • JLA Vol:21 Iss:4 (Contributions of Charles Townes&rsquo; 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.

    $25.00

  • JLA Vol:8 Iss:3 (Laser Hardened Materials Evaluation Laboratory (LHMEL))


    Authors:
    R. J. Hull
    M. L. Lander



    Since 1976, the Laser Hardened Materials Evaluation Laboratory (LHMEL) has been characterizing material responses to laser energy in support of national defense programs and the aerospace industry. Now that capability is available to commercial industry as well. LHMEL's power levels, beam uniformity, and diagnostics capabilities make it an ideal facility for proof&hyphen;of&hyphen;concept testing or process development. Located at Wright&hyphen;Patterson Air Force Base, Ohio, LHMEL is managed by the Wright Laboratory Materials Directorate and operated by Lawrence Associates, Incorporated. The facility's advanced hardware is centered aroun...

    $25.00

  • JLA Vol:2 Iss:2 (Binary Phase Gratings for Materials Processing)


    Authors:
    Paul J. Patt
    Array


    The feasibility of using a diffractive optical element, a phase grating, as a beam handling device for use in industrial laser material processing is examined. The binary phase grating is an efficient beam splitting device and is useful in many materials processing operations (welding, cutting, soldering, drilling) where a high degree of parallelism could significantly improve process throughput. Overall efficiency of etched quartz binary gratings agrees well with published predictions (nominal 70–90&percnt;). Copies of the grating formed in PMMA (acrylic) survived preliminary life tests (more than 1000 9&hyphen;J pulses from a commercial multimode N...

    $25.00

  • JLA Vol:25 Iss:5 (Heat transfer and fluid flow in additive manufacturing)


    Authors:
    A. Raghavan
    H. L. Wei
    T. A. Palmer
    T. DebRoy
    Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802


    In laser-based direct energy deposition additive manufacturing, process control can be achieved through a closed loop control system in which thermal sensing of the melt pool surface is used to adjust laser processing parameters to maintain a constant surface geometry. Although this process control technique takes advantage of important in-process information, the conclusions drawn about the final solidification structure and mechanical properties of the deposited material are li...

    $25.00

  • JLA Vol:15 Iss:4 (Welding of thick austenitic stainless steel using Nd:yttrium&ndash;aluminum&ndash;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...

    $25.00

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