JLA Vol:9 Iss:3 (Experimental study of cutting thick aluminum and steel with a chemical oxygen–iodine laser using an N₂ or O₂ gas assist)

Authors:
David L. Carroll
James A. Rothenflue

A chemical oxygen–iodine laser (COIL) was used to cut aluminum and carbon steel. Cut depths of 20 mm in aluminum and 41 mm in carbon steel were obtained using an N₂ gas assist and 5–6 kW of power on target. The same laser at the same power level produced a cut depth of 65 mm in carbon steel with an O₂ gas assist; a low quality cut to a depth of nearly 100 mm in carbon steel was also demonstrated. These data are compared with existing COIL and CO₂ laser cutting data. COIL cuts carbon steel and stainless steel at approximately the same rate. For a given cut depth, power and spot size...

JLA Vol:9 Iss:3 (High power laser welding in hyperbaric gas and water environments)

Authors:
G. J. Shannon
W. McNaught
W. F. Deans
J. Watson

A hyperbaric laser welding facility has been constructed and the feasibility of high power CO₂ and Nd:YAG laser welding in both high pressure gas and water environments, to simulated water depths of 500 m, has been established. From initial trials on welding through water at atmospheric pressure, it was found that the different absorption characteristics of water to 10.6 μm (CO₂ laser) and 1.06 μm (Nd:YAG laser) radiation proved crucial. The Nd:YAG laser was totally unsuitable as the beam was largely diffused in the water, whereas the CO₂ beam was rea...

JLA Vol:9 Iss:3 (In‐process monitoring of laser welding by the analysis of ripples in the plasma emission)

Authors:
Kiyokazu Mori
Isamu Miyamoto

A novel in‐process monitoring system employing two detectors set above the workpiece at different aiming angles of 5° and 75° has been developed to detect whether or not CO₂ laser welding fully penetrates through to the back surface of steel sheets. The acquired signal contained a.c. components of the emission of the laser‐induced plasma in the plume and in the keyhole with frequencies up to approximately 10 kHz. The mean square value of the a.c. signal obtained by using the 75° sensor during full penetration welding was much larger than that of the partial penetration welding, showing that full p...

JLA Vol:9 Iss:3 (Laser through‐cutting and drilling models for ablating/decomposing materials)

Authors:
Michael F. Modest
Department of Mechanical Engineering, The Pennsylvania State University, University Park, PA 16802, U.S.A.

A previously‐developed three‐dimensional conduction model for scribing of a thick solid has been extended to predict the transient temperature distribution inside a finite thickness slab that is irradiated by a moving laser source, and the cutting rate and profile carved by evaporation of material. The laser may operate in CW or in pulsed mode (with arbitrary temporal intensity distribution) and may have an arbitrary spatial intensity profile. The governing equations are solved using a finite‐difference method on a boundary‐f...

JLA Vol:9 Iss:4 (Are we ready for the future?)

Authors:
R. James Rockwell
Rockwell Laser Industries, 77454 Camargo Rd., Cincinnati, OH 45243, U.S.A.

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 (In the beginning there was ANSI Z136.1)

Authors:
Sidney S. Charschan
Charschan Associates, 7351 Kinghurst Drive, Delray Beach, Florida, U.S.A.

In the early 1960s concerns about eye safety were concentrated in a handful of research laboratories and the military. Memoranda and guidelines were circulated internally with their own set of priorities and recommended practices. Then, in 1968, the First International Laser Safety Conference (the brainchild of Dr Leon Goldman), was held in Cincinnati with one of its avowed purposes, the development of a consensus among the most prominent investigators as to what exposure criteria should be adopted. They saw the (laser) light. By 1969 it had become clear that, because of widespread d...

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 Arabia

The 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...

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: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 ...