JLA Vol:24 Iss:1 (Ultra-high speed disk laser cutting of carbon fiber reinforced plastics)
Authors:
Kwang-Woon Jung
Yousuke Kawahito
Seiji Katayama
Joining and Welding Research Institute (JWRI), Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047, JapanLaser cutting of carbon fiber reinforced plastics (CFRPs) has been known to be difficult due to the thermal damage to CFRP material. Therefore, with the objectives of evaluating the cutting possibility for long- or short-fiber pellet CFRP sheets of 3 mm in thickness and obtaining narrower heat affected zone (HAZ) for better cut quality, ultra-high speed cutting was conducted by using a continuous-wave high brightness disk laser. The increase in the laser power rendered the cutting time shorter...
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JLA Vol:6 Iss:4 (Holographic optical elements (HOEs): A serious application of holography)
Authors:
Gareth T. Williams
Jeff Fredrick
Physics Department, San Jose State University, San Jose, CA, U.S.A.Without disputing the excitement and sense of accomplishment associated with the production of display holograms, this paper suggests equal rewards from the production of holographic optical elements (HOEs). The elements described here are zone plates, diffraction gratings, interference filters and mirrors, and lenses. Ways of making each of these in an optics teaching laboratory are described, but the main emphasis will be on positive lens HOE.
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JLA Vol:6 Iss:4 (Exposure to “lessons learned”: A tool for laser safety)
Authors:
Kenneth Barat
Susan Elisabeth Kelly
Lawrence Berkeley Laboratory, Environment, Health & Safety Division, University of California, Berkeley, CA 94720, U.S.A.This article outlines the value and steps to follow for establishing a “lessons learned program”, with specific application to a laser safety program. As a communication tool and preventive measure for laser safety issues, the program is an effective means of turning accident investigation into a proactive rather than a reactive exercise by emphasizing corrective rather than disciplinary (looking for someone to blame) actions.
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JLA Vol:6 Iss:4 (Effect of the helium–neon laser on the healing of extraction wounds: A histological study in rats)
Authors:
Walter Niccoli‐Filho
Tetuo OkamotoA histological study on the healing of extraction wounds following laser irradiation using a He–Ne laser, was carried out in rats. The results suggest that this mode of treatment has a beneficial effect on initial bony wound healing. Proliferation of fibroblasts and formation of trabecular osteoid tissue were found to be more prominent within the irradiated group. The deposition of led in the newly formed bone suggests swifter ossification within the irradiated group.
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JLA Vol:6 Iss:4 (Characteristics of power meters for high power CO<sub>2</sub> lasers)
Authors:
Keng H. Leong
Donna J. Holdridge
Kenneth R. Sabo
Laser Applications Laboratory, Technology Development, Argonne National Laboratory, University of Chicago, IL 60439, U.S.A.Four different instruments used for measuring CO2 laser beam power in the kilowatt range were evaluated. The techniques used to determine the laser beam power included temperature increase from an absorber of known mass and specific heat, temperature increase from a steady flow of water used to cool the absorber, thermal gradient caused by edge‐cooling a circular absorber, and diffuse scattering from a small portion of the water‐cooled absorber surface. Th...
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JLA Vol:6 Iss:4 (Nd:YAG laser welding of coated sheet steel)
Authors:
M. P. Graham
D. M. Hirak
H. W. Kerr
D. C. Weckman
Department of Mechanical Engineering, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1.The weldability of coated sheet steels by a 2 kW Nd:YAG laser has been examined. Laser seam welds were produced in 0.75‐mm thick (23 gauge) galvanized and galvannealed sheet steels in the lap‐joint configuration. Three types of laser beam power output were used: continuous wave, sine‐wave modulated, and square‐wave modulated. The effects on weld quality of varying laser welding parameters such as welding speed, shielding gas composition, and gas flow rate were stud...
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JLA Vol:6 Iss:4 (Hazardous chemicals produced by laser materials processing)
Authors:
John M. Kokosa
GMI Engineering & Management Institute, Flint, MI, U.S.A.Despite evidence to the contrary, until recently many laser operators believed, or at least stated, that the only chemical by‐products of laser processing of any consequence were water and CO2. During the last eight years, especially, several investigations have shown that hazardous materials are produced when cutting or welding nearly all substrates. In the following paper, the major chemical hazards associated with processing metals, inorganics, biomaterials, and polymers are outlined.
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JLA Vol:6 Iss:4 (Laser accidents: Reviewing thirty years of incidents: what are the concerns — Old and new?)
Authors:
R. James Rockwell
Rockwell Laser Industries, PO Box 43010, Cincinnati, OH, U.S.A.Overall analysis reveals that laser accidents are generally caused by one or more of the following: unanticipated eye exposure during alignment; non‐use of available eye protection; equipment malfunction causing unwanted exposure; improper methods of handling high voltages, leading to severe shock or death; lack of protection for non‐beam hazards; improper restoration of equipment following service; and incorrect eyewear selection and/or eyewear failure, leading to unwanted exposure. The statistical laser information given in this review provides a starting point for more complete ...
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JLA Vol:6 Iss:2 (Laser cladding of Ti–6Al–4V with various carbide powders)
Authors:
J. A. Folkes
K. Shibata
Nissan Motor Co., Ltd, Material Research Laboratory, Central Engineering Laboratories, 1, Natsushima‐cho, Yokosuka 237, JapanLaser cladding Ti–6Al–4V can be achieved with various weight percentages of different carbide powders. The microstructure and morphology of the clad layer is determined by the cladding powder composition, for a given set of laser parameters, such that 10 and 20 wt %Cr3C2 results in a β + TiC clad microstructure; 10 and 20 wt %WC results in an α + TiC clad microstructure (plus some original WC); and Mo2C gives an α + &be...
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JLA Vol:6 Iss:4 (Investigation into the underwater laser welding of steel)
Authors:
G. J. Shannon
J. Watson
W. F. Deans
Department of Engineering, Laser Laboratory, Kings College, University of Aberdeen, Aberdeen, U.K.An investigation was undertaken using a 1.2 kW carbon dioxide laser for underwater butt welding of BS 4360 43A and 50D steel, in order to assess the quality of the welds and to achieve an understanding of the laser/water/material interaction. Using a high‐speed camera, the temporal behavior of the melt pool and “plasma” dynamics surrounded by an aqueous environment were monitored. Experiments were undertaken to characterize the attenuation of the laser beam in the water as a function of various foca...
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