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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:17 Iss:4 (Faster and damage-reduced laser cutting of thick ceramics using a simultaneous prescore approach)
Authors:
V. Pereles-Santiago
M. Washington
P. Brugan
G. Cai
R. Akarapu
S. Pulford
A. E. Segall
The Pennsylvania State University, University Park, Pennsylvania 16802Laser machining of structural ceramics is increasingly gaining acceptance as an alternative to traditional machining methods. However, despite the great promise of lasers for a variety of cutting and drilling procedures, premature fractures and prohibitively low cutting speeds are still among the greatest obstacles encountered, particularly when thick cross sections are involved. While many factors contribute to the fractures encountered during ...
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JLA Vol:3 Iss:3 (Safety of Medical Excimer Lasers with an Emphasis on Compressed Gases)
Authors:
David H. Sliney
Laser Microwave Division, US Army Environmental Hygiene Agency, Aberdeen Proving Ground, MD 21010‐5422
Terrance N. Clapham
VISX, Inc., 919 Kifer Road, Santa Clara, CA 94086Excimer lasers which emit short ultraviolet radiation (UVR) are currently being used in experimental and developmental surgical applications. Although UVR exposure is possible, it is not normal in laser angioplasty (cardiovascular surgery) and is insignificant in photokera‐toplasty (ophthalmic surgery). However, significant potential hazards exist with the use of excimer laser gases such as fluorine and HCI. Stringent safeguards for handling and use are ...
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JLA Vol:22 Iss:2 (Keyhole behavior in deep penetration CO<sub>2</sub> laser welding)
Authors:
Hiroshi Honda
Susumu Tsukamoto
Isao Kawaguchi
Goro Arakane
Structural Metals Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, JapanA slender keyhole formed by deep penetration laser welding fluctuates violently and is apt to form porosity. To reveal the keyhole depth behavior, the authors observed the keyhole images simultaneously by using a microfocus x-ray transmission imaging system and plasma plume images in deep penetration CO2 laser welding at various welding speeds. Plasma light emission was also measured by using photodiodes. The upper part of the keyhole was found to fluctuat...
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JLA Vol:25 Iss:3 (Evaluation of corneal and eye lens irradiance for optical aided viewing)
Authors:
Enrico Galbiati
GEST Labs, Via Kennedy, 20871 Vimercate, ItalyThe use of a magnifying lens with a highly divergent laser beam may cause a big increase of the irradiance on the cornea and the eye lens. This study provides the analysis of several cases where the use of a lens lead to a corneal irradiance significantly higher than the naked-eye viewing. The examples analyzed in this study allow determining the factors that represent the increase of the corneal irradiance caused by the use of the lens. The results indicate that these factors of irradiance increase may be close to 100.
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JLA Vol:24 Iss:2 (Laser dressing of metal bonded diamond blades for cutting of hard brittle materials)
Authors:
Philipp von Witzendorff
Anas Moalem
Rainer Kling
Ludger Overmeyer
Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover, GermanyIn this study, the authors investigate the laser dressing of metal bonded diamond blades by means of laser pulses with different pulse durations and wavelengths. Conventional dressing suffers from excessive blade wear, whereas laser dressing enables precise removal of the bonding metal to generate the required chip space of protruding diamond grains. The challenge for processing this composite material is to find appropriate level of ablation for the bonding metal without damaging the diamond grains thr...
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JLA Vol:15 Iss:4 (Laser–material interaction and process sensing in underwater Nd:yttrium–aluminum–garnet laser welding)
Authors:
Xudong Zhang
Wuzhu Chen
Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
Eiji Ashida
Fukuhisa Matsuda
Tarasaki R&D Center, JAPEIC, Hitachinaka, Ibaraki 312-0003, JapanLaser–material interaction and process sensing technology for local-dry underwater Nd:yttrium–aluminum–garnet laser beam welding were studied. The optical emissions induced by laser–water interaction were detected with an infrared (IR) optical sensor and observed with a charge coupled device camera. It was found that under laser irradiation, a kind of water–vapor plasma formed immediately above the ...
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JLA Vol:6 Iss:3 (Safety concerns about laser pointers)
Authors:
David H. Sliney
Jerome E. DennisIn the past two years considerable concerns have been expressed about the safety of Class 3A laser pointers. The concern has been that Class 3A diode–laser pointers have replaced the safer helium–neon (He–Ne) Class 2 laser pointers. Hundreds of thousands of small He–Ne visible‐wavelength lasers have been traditionally used for alignment and pointing, laser demonstrations and laser displays in science, education and industry, but can the diode laser be as safe and effective? Not infrequently, some people associate “lasers” with Buck Rogers and “Star Wars”, and are concerned wh...
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JLA Vol:20 Iss:1 (Practical and theoretical investigations into inert gas cutting of 304 stainless steel using a high brightness fiber laser)
Authors:
Martin Sparkes
Markus Gross
Steven Celotto
Tao Zhang
William O’Neill
Centre for Industrial Photonics, Institute for Manufacturing, Department of Engineering, University of Cambridge, Cambridge, CB2 1RX, United KingdomA 2.2 kW fiber laser was used in a series of inert cutting trials on stainless steels of section thicknesses in the range of 6–10 mm. Variations in the cutting performance with changing gas pressure, focal position, and nozzle diameter were investigated. Results showed the difficulties associated in cutting with high brightness lasers, specifically in obtaining full melt eject through narr...
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JLA Vol:14 Iss:2 (Human behavioral factors in laser safety)
Authors:
Rick Mannix
Environmental Health & Safety Office, University of California, Irvine, California 92697-2725While training, engineering controls, warning signs/systems, and protective eyewear are emphasized in laser safety programs, laser-related accidents do occur in facilities without obvious deficiencies in those areas. Problems still occur because of insufficient attention to administrative safety issues directly related to human nature and behavioral factors. Common safety problems associated with behavioral factors are discussed. Personal experiences of the author, including lessons learned, are included. The issues are discussed within the context of laser safety, bu...
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