JLA Vol:7 Iss:2 (A study of polarization‐maintaining fiber characteristics with applications to force and displacement sensing)

Authors:
P. V. P. Yupapin
K. Weir
K. T. V. Grattan
A. W. Palmer

An experimental investigation of three different types of highly birefringent fiber sensor element configured as a force and a displacement sensor is described. From the coupling of power between the two eigenmodes, the magnitude of the force and the position of the coupling point can then be determined using ‘white‐light interferometric’ techniques.

JLA Vol:7 Iss:2 (Understanding laser hazard evaluation)

Authors:
Wesley J. Marshall
U.S. Army Center for Health Promotion and Preventive Medicine (Provisional), Aberdeen Proving Ground, MD 21010‐5422, U.S.A.

The current 1993 version of the ANSI Z136.1 standard for the safe use of lasers provides maximum permissible exposures which more closely match available biological injury data. Interpreting the standard can be more difficult at times than with previous versions. By keeping the biological injury mechanism in mind, the reasoning behind the multitude of rules contained in the standard are more understandable.

JLA Vol:7 Iss:3 (Institut fu¨r Strahlwerkzeuge (IFSW), University of Stuttgart)

Authors:
Helmut Hu¨gel
Institut fu¨r Strahlwerkzeuge, University of Stuttgart, Pfaffenwaldring 43, D‐70569 Stuttgart, Germany

JLA Vol:7 Iss:3 (Institut de Soudure Laser Center)

Authors:
J. C. Goussain
A. Chehaibou
Institut de Soudure, 4 Boulevard Henri Becquerel, 57110 Yutz, France

JLA Vol:7 Iss:3 (Study of liquid and vapor ejection processes during laser drilling of metals)

Authors:
Bekir S. Yilbas¸
Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia

In an experimental investigation of laser–metal interaction, one of the important parameters is the propagation velocity of the liquid–vapor interface. The quantity appears as a direct result of the theoretical examination of the interaction and may be used to test the accuracy of the theory. Consequently, in the present study, the nature of the interaction mechanism between a pulsed laser beam and metals is examined using streak photographs of the ejecta from four metals: titanium, tantalum, nickel, and EN58B stainless steel. It...

JLA Vol:7 Iss:3 (Characterization of chromium bearing surface alloys produced by laser alloying on low carbon steel substrates)

Authors:
G. L. Goswami
Dilip Kumar
A. L. Pappachan
A. K. Grover
K. Sridhar
Array

High‐chromium ferritic alloys were produced on mild steel substrates by laser surface alloying. For this, chromium‐plated mild steel samples were treated with a pulsed Nd:YAG laser (300 W maximum power) by varying the average power level from 21.6 W to 30.0 W. The chromium content of the surface alloys was in the range of 3.0–27.0 wt%, with fairly uniform depth of alloying. Microscopy showed very fine austenite needles within elongated/equiaxed ferrite grains in the laser‐alloyed zone (LAZ). X‐ray diffraction indi...

JLA Vol:7 Iss:3 (Determination of energy absorption during laser welding by an iterative conduction method)

Authors:
Junji Mimatsu
Jeannine A. Bos
Elijah Kannatey‐Asibu
Michael M. Chen
Department of Mechanical Engineering and Applied Mechanics, The University of Michigan, 2146 G. G. Brown, Ann Arbor, MI 48109‐2125, U.S.A.

Energy absorption is a key process in laser welding. While there is now good qualitative empirical knowledge of the dependence of the effective absorptivity on laser power level, detailed quantitative understanding is poor. In recent years there has been considerable interest in computational modeling of the heat transfer and fluid flow phenomena during laser welding, in order to have a better understanding of the physic...

JLA Vol:7 Iss:3 (Impact resistance of adhesive joints using laser‐induced shock waves)

Authors:
I. Gilath
R. Englman
Z. Jaeger
A. Buchman
H. Dodiuk

The impact resistance of aluminum–aluminum joint bonded with FM‐73 (American Cyanamid) structural adhesive was studied using laser‐induced shock waves. The adhesive joint failed in a ductile mode, showing shock absorbtion ability through plastic deformation. All stages of the impact damage were identified from threshold damage through complete sample perforation. In the theoretical study, the damage induced in the target is obtained as follows. The shock wave is modeled by an expanding stress front, which creates a void population in the laser‐im...

JLA Vol:6 Iss:3 (Free electron laser irradiation at 200 μm inhibits DNA synthesis in living cells)

Authors:
Michael W. Berns
William Bewley
Chung‐Ho Sun
Pamela Templin
Alexander Karn

The effect of a 200 μm wavelength free electron laser (FEL) beam on vertebrate tissue culture cells in two study series is described. Cell cultures exhibited no morphological alterations. However, a statistically significant proportion of the cells exhibited a reduction in tritiated thymidine incorporation. The results suggest that this wavelength might affect DNA synthesis, and the studies demonstrate the feasibility of biological investigations with the FEL.

JLA Vol:6 Iss:3 (Acoustic emission response of soda lime glass after a single Nd‐YAG laser pulse)

Authors:
R. Harrysson
P. Vomacka
Department of Engineering Materials, Luleå University of Technology, S‐951 87 Luleå, Sweden

When machining brittle solids with a laser, crack formation can occur in the material around the irradiated area causing a strength reduction of the machined material. The purpose of this work was to study a well known brittle material (soda lime glass) by means of acoustic emission (AE) in order to investigate the correlation between visually observed crack formation and detected AE energy released by the crack formation in the material. During and after irradiation of soda lime glass with an Nd‐YAG laser pulse, the number...