JLA Vol:9 Iss:6 (Evolving issues in laser safety)

Authors:
David H. Sliney
US Army Center for Health Promotion and Preventive Medicine, Laser/Optical Radiation Program, Aberdeen Proving Ground, MD 21010‐5422, U.S.A.

The approach to laser safety has come a long way since the 1960s when the first guidelines were issued by defense research organizations in the US and the UK, and then by the American Conference of Governmental Industrial Hygienists. Although the search for ‘eye‐safe’ numbers continues in a few laboratories, this work is almost exclusively centered on deriving retinal thresholds for ultra‐short (sub‐nanosecond) lasers. Setting limits in this temporal region has been difficult, since...

JLA Vol:9 Iss:6 (Amendments to the Center for Devices and Radiological Health Federal Performance Standard for laser products)

Authors:
Jerome E. Dennis
Center for Devices and Radiological Health, Food and Drug Administration, Rockville, MD, U.S.A.

Federal law requires that all laser products that are imported into or introduced into commerce in the United States comply with the performance standard published in the Code of Federal Regulations (CRF), Title 21, Parts 1040.10 and 1040.11, administered by the Center for Devices and Radiological Health (CDRH), US Food and Drug Administration. Although it contains somewhat different requirements for hazard classification, engineering controls and labeling, the ANSI Z136.1 standard defers to the CDRH standard. The CDRH standard became effective in August, 1976 and ...

JLA Vol:9 Iss:6 (… .But is it really safe?)

Authors:
Peter A. Smith
DERA Centre for Human Sciences, Farnborough, Hampshire, U.K.

JLA Vol:8 Iss:1 (Recent progress in laser surface treatment: <emph type="4">I</emph>. Implications of laser wavelength)

Authors:
W. Bloehs
B. Gru¨nenwald
F. Dausinger
H. Hu¨gel
Institute fu¨r Strahlwerkzeuge, Universita¨t Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart, Germany

The coupling mechanisms of laser radiation and the mechanisms of heat transport in the workpiece are considered. Starting from the well&hyphen;known basics of Fresnel absorption — valid only for smooth and clean surfaces — further effects of coupling are examined. Studies on the effects of surface modifications inherent to all industrial parts and process conditions are presented. The more appropriate term coupling rate is introduced: This describes the r...

JLA Vol:8 Iss:1 (Comparison of aluminum alloy welding characteristics with 1 kW CO and CO₂ lasers)

Authors:
Bu¨lent A. Mehmetli
Kunimitsu Takahashi
Shunichi Sato
Institute of Research and Innovation, Laser Laboratory 1201 Takada, Kashiwa&hyphen;shi, Chiba 277, Japan

Welding characteristics of various aluminum alloys (A1100, A2017, A5083, A6063, A7N01) are investigated with CW CO and CO₂ lasers near 1 kW power level. The beam characteristics of both lasers at the welding point are similar, so that a comparison can be made of the effect of the wavelength difference. The welding characteristics are assessed by measuring the size of the weld bead. It is found that the threshold power between heat&hyphen;conduction and deep&hyphen;penetration typ...

JLA Vol:8 Iss:1 (Frequency&ndash;time characteristics of air&hyphen;borne signals from laser welds)

Authors:
D. Farson
K. Hillsley
J. Sames
R. Young

The acoustic emissions from laser lap welds in stainless steel sheet were recorded and analyzed. The acoustic signals emanating from the weld were sensed with an instrument microphone and analyzed using short&hyphen;time Fourier spectra to characterize their time&hyphen;frequency distributions. It was determined that the acoustic spectrum of good&hyphen;quality, full&hyphen;penetration welds could be differentiated from the spectra of poor&hyphen;quality welds, defined as either partial&hyphen;penetration welds or welds having a gap between the sheets being joined. A novel, relatively simple class...

JLA Vol:8 Iss:1 (Laser polarimeters: Overview of recent developments, design and applications)

Authors:
Vi´ctor Fajer Avila
Center for the Development of Scientific Equipment and Instruments, Ministry of Science Techonology and Environment, Havana, Cuba

Research carried out in Cuba has led to the design and construction of automatic polarimeters that use the He&hyphen;Ne laser as a luminous source and work on a magnetooptic principle of measurement. Physical and chemical investigations including the use of the He&hyphen;Ne laser as a light source are discussed. The principle of measurement for the design and construction of polarimeters, resulting in three different types of these instruments, is described. Finally, applications for magnetooptic polarimetry are described,...

JLA Vol:8 Iss:1 (Laser technology at the Oak Ridge National Laboratory)

Authors:
Marc L. Simpson
John C. Miller
Doug H. Lowndes
Oak Ridge National Laboratory, PO Box 2008 Oak Ridge, TN 37831, U.S.A.

Researchers at the Department of Energy (DOE) facilities at Oak Ridge perform a variety of basic and applied research involving lasers and laser technology. One of the major strengths at Oak Ridge is the combination of core capabilities in optical materials, optical diagnostics, and sensors. Communities benefiting from these core capabilities include environmental, biomedical, and industrial sponsors. Industry can interact with Oak Ridge in a variety of ways: with Cooperative Research and Development Agreements (CRADAs), through Work ...

JLA Vol:8 Iss:3 (Laser shock processing of materials, physical processes involved and examples of applications)

Authors:
P. Peyre
R. Fabbro
L. Berthe
C. Dubouchet

Laser shock processing (LSP) consists of irradiating a metallic target with a short (about 20 ns) and intense (>10¹³W m⁻²) laser light in order to generate, through a high pressure surface plasma (>1 GPa), a plastic deformation and a surface strengthening within materials. This paper initially reviews the physical processes involved in the analytical modeling of the generation pressure mechanism in a confined plasma regime. Limiting factors such as the dielectric breakdown in the confining medium are also discussed together with current research directions aimed...

JLA Vol:8 Iss:2 (Trepan drilling of fuel injection nozzles with a TEM₀₀ Nd:YAG slab laser)

Authors:
H. Rohde
E. Meiners

Holes of 160 μm diameter were trepan drilled in fuel injection nozzles of 1 mm thickness by means of a TEM₀₀ fundamental mode Nd:YAG slab laser. Two different types of holes have been trepan drilled: at an angle of 90°, and at an angle of 60° to the metal surface. The influence of nozzle distance, focal position, gas pressure, pulse repetition frequency and trepanning velocity on the hole diameter and on the conicity are investigated. A diameter accuracy of ±10 μm and a conicity of 3&percnt; were achieved. One hole is drilled in 7–25 seconds in dependence of the drilling strategy.