JLA Vol:9 Iss:4 (Investigation into first and second law efficiencies of solid state laser head: A case study)
Authors:
B. S. Yilbas
A. Kar
M. Sunar
Mechanical Engineering Department, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi ArabiaThe efficiency of a solid state pulsed laser is very low which is generally ascribed to the poor optical and electrical efficiencies of the components used in the laser head. The temperature of the laser rod rises during the optical pumping process which causes thermally induced distortions in the laser output beam and hence a low quality laser beam is obtained. In the present study, the temperature rise in the laser rod during the pulsed optical pumping process is investigated, and the first and second law effic...
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JLA Vol:9 Iss:5 (Threshold laser beam irradiances for melting and welding)
Authors:
K. H. Leong
H. K. Geyer
K. R. Sabo
P. G. Sanders
Technology Development Division, Argonne National Laboratory, Argonne, IL 60439, U.S.A.A model based on the conservation of energy for a moving heat source incident on a flat plate is used to predict the threshold laser beam irradiance required to initiate melting on a metal surface. With the use of a non‐dimensional variable and its solution, the threshold irradiance can be predicted with the use of a simple equation. This equation is a function of the absorptivity of the surface, thermal conductivity of the metal, temperature increase for melting, diameter of the laser beam at th...
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JLA Vol:9 Iss:5 (Experimental development of a machining database for the CO<sub>2</sub> laser cutting of ceramic tile)
Authors:
S. A. J. Livingstone
K. L. Chua
I. Black
Department of Mechanical and Chemical Engineering, Heriot‐Watt University, Riccarton, Edinburgh EH14 4AS, U.K.This paper covers the cutting of commercially‐available ceramic tiles using a CO2 laser cutting machine, with the object of producing a laser beam machining database which contains the essential parameter information for their successful processing. Various laser cutting parameters were investigated that would generate a cut in ceramic tile which required minimal posttreatment. The effects of various shield gases, multipass cutting and underwater cutting were also examined.
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JLA Vol:9 Iss:5 (Characteristics of Nd:YAG laser welded high carbon steels)
Authors:
Eng S. Ng
Ian A. Watson
Laser and Optical System Engineering Centre, Department of Mechanical Engineering, James Watt Building, University of Glasgow, Glasgow G12 8QQ, U.K.A quantitative study of the relationship between the laser process parameters and the mechanical properties of welded high carbon steels was performed utilizing a Lumonics Nd:YAG pulsed laser, operating at 1.06μm, and a robotically manipulated fiber optic beam delivery system. A gage plate (0.88 mm thick) was butt welded with a constant power of 200 W and a He shielding gas was used at a pressure of 5 × 104 Pa. The welding performance of the Nd:YAG laser was strongly affect...
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JLA Vol:9 Iss:5 (Laser safety analysis of a retinal scanning display system)
Authors:
Erik Viirre
Richard Johnston
Homer Pryor
Satoru Nagata
Thomas A. Furness
Human Interface Technology Laboratory, University of Washington, Box 352142, Seattle, WA 98195–2142, U.S.A.The Virtual Retinal Display (VRD) is a visual display that scans modulated laser light on to the retina of the viewer's eye to create an image. Maximum permissible exposures (MPE) have been calculated for the VRD in both normal viewing and possible failure modes. The MPE power levels are compared to the measured power that enters the eye while viewing images with the VRD. The power levels indicate that the VRD is safe in both normal operatin...
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JLA Vol:9 Iss:5 (Laser‐Induced Damage in Optical Materials at the October 7–9, 1996 Symposium on Optical Materials for High‐Power Lasers (the Boulder Damage Symposium) Boulder, Colorado)
Authors:
Arthur H. Guenther
Sandia National Laboratories, Albuquerque, New Mexico 87106, U.S.A.The 28th annual symposium on optical materials for high‐power lasers (Boulder damage symposium) was held at the National Institute of Standards and Technology in Boulder, CO, 7–9 October 1996. The symposium was held under the joint sponsorship of Bennett Optical Research, the Center for Research and Education in Optics and Lasers (CREOL) at the Center for Research and Education in Optics and Lasers (CREOL) at the University of Central Florida, Los Alamos National Laboratory, Lawrence Livermore National Laboratory, Sandia National Laboratories, and SPIE—The International ...
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JLA Vol:9 Iss:6 (Effect of nozzle orientation on the gas dynamics of inert-gas laser cutting of mild steel)
Authors:
Aaron D. Brandt
Gary S. Settles
Gas Dynamics Laboratory, Mechanical Engineering Department, Penn State University, University Park, PA 16802, U.S.A.This investigation applies sonic and supersonic coaxial and off‐axis nozzles to the cutting of mild steel sheet of 1–4 mm thickness. A 1.5 kW CW CO2 laser is used with nitrogen as the assist gas. Sonic coaxial cutting is compared to that of off‐axis nozzles, which vary in orientation from 20–60° behind the laser axis and in exit Mach number from 1 to 2.4. Results show a 50% increase in maximum cutting speed at approximately a 40° off‐axis nozzle angle. In com...
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JLA Vol:9 Iss:6 (Scaling laws for thick‐section cutting with a chemical oxygen–iodine laser)
Authors:
A. Kar
J. A. Rothenflue
W. P. LathamAlmost all laser‐assisted materials processing involves melting, vaporization and plasma formation which affect the utilization of laser energy for materials processing. To account for the effect of these phases, an effective absorptivity is defined, and a simple mathematical model is developed for the cutting of thick‐section stainless steel using a high power chemical oxygen—iodine laser (COIL). The model is based on an overall energy balance, and it relates the cutting depth with various process parameters that can be used to predictively scale the laser materials processing performance to ...
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JLA Vol:9 Iss:6 (Improved hole drilling using a high peak power Nd:YAG laser at the second harmonic wavelength)
Authors:
Xiangli Chen
Angel L. Ortiz
P. Randall Staver
William T. Lotshaw
Todd J. Rockstroh
Michael H. McLaughlinWe have previously described the drilling of advanced materials such as intermetallics, superalloys, and composites using an Nd:YAG laser operating at the fundamental wavelength of 1.064 μm [1]. We have now extended these studies to the second harmonic wavelength of 532 nm of a high peak power Nd:YAG laser. The results show that drilling using the shorter wavelength further reduces undesired thermal effects such as recast layers and heat affected zones. A comparison of these results with those obtained at...
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JLA Vol:9 Iss:6 (Intrapulpar temperature during continuous CO<sub>2</sub> laser irradiation in human molars: An <em>in vitro</em> study)
Authors:
Walter Niccoli‐Filho
Jose´ Camilo Furlani
Carlos Schwab
Fernando Vagner Raldi
Carlos de Paula EduardoTo establish safety parameters, we in vitro studied the increase in intrapulpal temperature caused by the use of a cw CO2 laser. A thermistor was implanted in the inner part of the pulpal chamber of 25 human lower third molars to measure the intrapulpal temperature produced by laser powers between 2–10 W and exposure times of 0.5–25.0 s. The Pearson linear correlation factor applied to the measured values showed there is a direct relationship between the independent variable and ...
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