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...

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...

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 ...

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...

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...

JLA Vol:9 Iss:5 (Experimental development of a machining database for the CO₂ 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.

JLA Vol:9 Iss:4 (The drilling of slate tiles by a Nd:YAG laser)

Authors:
F. Lusquin˜os
J. Pou
R. Soto
M. Pe´rez‐Amor
Departamento de Fisica Aplicada, Universidade de Vigo, Lagoas Marcosende 9, E‐36280 Vigo, Spain

We have undertaken a series of experiments to investigate the feasibility of using a Nd:YAG laser to drill slate tiles. Slate is used primarily as a roof building material after it is split into thin flat layers. The traditional fixation system of slate tiles in Europe consists of clamping the slate pieces by means of metallic clamps and overlapping the different tiles in order to form an impervious roof. An alternative to this clamping technique, is the use of nails to fix ...

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

Authors:
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‐containing electrolytes. In this paper, improvement of the pitting corrosion resistance of 2014‐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‐situ...

JLA Vol:9 Iss:4 (The application of external feedback in the laser spectroscopy of nonlinear media)

Authors:
B. V. Anikeev
D. V. Sin'ko
Department of Laser Physics, Volgograd State University, 2‐aya Prodolnay 30, Volgograd 400 062, Russia

A new spectroscopic technique to gain information on the nonlinear constants of optical materials is presented. This technique is made possible due to the point that the application of an external controlled negative feedback (CNF) circuit to an intracavity nonlinear cell results in the generation of extended boundaries of the stability for the laser beam. This effect is analyzed using a semiclassical set of equations that govern laser oscillation. Measurements are made on systems containing either an instantaneous CNF circuit o...

JLA Vol:8 Iss:3 (Commonwealth of Independent States (CIS) laser scene and Laser Association (LAS) activities)

Authors:
Ivan B. Kovsh
LAS Headquarters, Moscow, Rozhdestvenkastr, 27, 117485, Russia