• JLA Vol:9 Iss:2 (Temperature&hyphen;dependent absorptivity and cutting capability of CO<sub>2</sub>, Nd:YAG and chemical oxygen&ndash;iodine lasers)

    J. Xie
    A. Kar
    J. A. Rothenflue
    W. P. Latham

    The most widely used high power industrial lasers are the Nd:YAG and CO2 lasers. The chemical oxygen iodine laser (COIL), whose wavelength (1.315 μm) is between that of the Nd:YAG (1.06 μm) and CO2 (10.6 μm) lasers, is another high power laser for industrial applications. The cutting capability of these lasers is investigated in this paper. The cut depth strongly depends on the absorptivity of the cut material, kerf width and cutting speed. The absorptivity is an unknown parameter for which experimental data at high temperatures are currently unavailable. Theoret...


  • JLA Vol:9 Iss:3 (A power distribution model of industrial CO<sub>2</sub> lasers for system diagnosis)

    James G. Katter
    Jay F. Tu
    Mark Gartner

    Industrial lasers are high power pieces of equipment that occasionally function under undesirable operating conditions. For example, the performance of a transverse&hyphen;flow d.c.&hyphen;excited gas laser can be adversely affected by many factors such as electrode arcing, poor lens and mirror cleanliness, focusing problems, improper gas mixture composition, poor gas quality, poor beam stability, poor beam path cleanliness, operator error, poor maintenance, poor chiller water temperature and flow rate stability, and improper laser beam ramp&hyphen;in/ramp&hyphen;out rates. Many of these factors which occur in ...


  • JLA Vol:9 Iss:3 (Diode laser scribing of non&hyphen;oriented 3 wt&percnt; Si&hyphen;steel for core loss reduction)

    Ravisankar Gurusamy
    P. A. Molian
    Mechanical Engineering Department, Iowa State University, Ames, IA 50011, U.S.A.

    The electrical power industries are experiencing a considerable energy loss in transformers and motors because of inefficiencies caused by core loss. The objective of our research is to investigate any effect of laser scribing on the reduction of the core loss in the low cost, non&hyphen;oriented steels used in numerous utility applications. A 15 W diode laser transmitted through fiber optics was used to scribe 0.35 mm thick, non&hyphen;oriented 3 wt&percnt; Si steel. The magnetic properties including the core loss and permeability were evaluated both...


  • JLA Vol:9 Iss:3 (Effective laser ablation of enamel and dentine without thermal side effects)

    Peter Kohns
    Ping Zhou
    Reinhard Sto¨rmann
    Optikzentrum NRW, Universita¨tsstraß 142, D&hyphen;44799 Bochum, Germany

    We present a feasibility study into laser treating dental materials by using femtosecond pulses generated by a titanium:sapphire laser system which consisted of an oscillator and a regenerative amplifier. The pulse duration was varied between 200 fs and 2 ps. The observed energy thresholds for the ablation process of dentine and enamel were clearly smaller than those observed when longer pulse durations were used. The consequence of this observation is a lower thermal load within the vicinity of the radiated area. Thus no th...


  • 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)

    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...


  • JLA Vol:9 Iss:3 (High power laser welding in hyperbaric gas and water environments)

    G. J. Shannon
    W. McNaught
    W. F. Deans
    J. Watson

    A hyperbaric laser welding facility has been constructed and the feasibility of high power CO2 and Nd:YAG laser welding in both high pressure gas and water environments, to simulated water depths of 500 m, has been established. From initial trials on welding through water at atmospheric pressure, it was found that the different absorption characteristics of water to 10.6 μm (CO2 laser) and 1.06 μm (Nd:YAG laser) radiation proved crucial. The Nd:YAG laser was totally unsuitable as the beam was largely diffused in the water, whereas the CO2 beam was rea...


  • JLA Vol:9 Iss:3 (In&hyphen;process monitoring of laser welding by the analysis of ripples in the plasma emission)

    Kiyokazu Mori
    Isamu Miyamoto

    A novel in&hyphen;process monitoring system employing two detectors set above the workpiece at different aiming angles of 5° and 75° has been developed to detect whether or not CO2 laser welding fully penetrates through to the back surface of steel sheets. The acquired signal contained a.c. components of the emission of the laser&hyphen;induced plasma in the plume and in the keyhole with frequencies up to approximately 10 kHz. The mean square value of the a.c. signal obtained by using the 75° sensor during full penetration welding was much larger than that of the partial penetration welding, showing that full p...


  • JLA Vol:9 Iss:3 (Laser through&hyphen;cutting and drilling models for ablating/decomposing materials)

    Michael F. Modest
    Department of Mechanical Engineering, The Pennsylvania State University, University Park, PA 16802, U.S.A.

    A previously&hyphen;developed three&hyphen;dimensional conduction model for scribing of a thick solid has been extended to predict the transient temperature distribution inside a finite thickness slab that is irradiated by a moving laser source, and the cutting rate and profile carved by evaporation of material. The laser may operate in CW or in pulsed mode (with arbitrary temporal intensity distribution) and may have an arbitrary spatial intensity profile. The governing equations are solved using a finite&hyphen;difference method on a boundary&hyphen;f...


  • JLA Vol:9 Iss:4 (Are we ready for the future?)

    R. James Rockwell
    Rockwell Laser Industries, 77454 Camargo Rd., Cincinnati, OH 45243, U.S.A.


  • JLA Vol:9 Iss:4 (Dual wavelength laser beam alloying of aluminum alloy for enhanced corrosion resistance)

    Z. Liu
    K. G. Watkins
    W. M. Steen
    R. Vilar
    M. G. Ferreira

    Aluminum alloys are known for their poor resistance to localized attack and, in particular, for pitting in chloride&hyphen;containing electrolytes. In this paper, improvement of the pitting corrosion resistance of 2014&hyphen;T6 aluminum alloy has been investigated by means of laser surface alloying of Cr into the substrate. Since aluminum is a highly reflective and thermally conductive material, it is often difficult to process with laser beams. Oxide films on the surface can prevent surface alloying as with the case of Cr alloying into aluminum by in&hyphen;situ...



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