JLA Vol:19 Iss:4 (Novel technique for laser lap welding of zinc coated sheet steels)

Authors:
X. Li
S. Lawson
Y. Zhou
Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario N2L 3G1 Canada

F. Goodwin
International Lead Zinc Research Organization, Inc., Research Triangle Park, North Carolina, 27713, USA

When zinc coated steels are laser welded, zinc adjacent to the weld bead is vaporized and will cause serious weld pool disruption in lap welding unless special measures are applied such as provision of a joint gap for vapor venting. A novel alternative technique has been developed to stabilize laser lap welding: this involves addition of a small amount of aluminum to the faying surface region, so t...

JLA Vol:19 Iss:4 (Role of strong focusability on the welding process)

Authors:
Jan Weberpals
Friedrich Dausinger
IFSW Institut fu¨r Strahlwerkzeuge, D-70569 Stuttgart, Federal Republic of Germany

Gunther Go¨bel
Berndt Brenner
IWS Institut fu¨r Werkstoff- und Strahltechnik, D-01277 Dresden, Federal Republic of Germany

Thin disk lasers as well as fiber lasers are distinguished by their strong focusability and high efficiency. With the availability of such laser sources in a high power region, keyhole welding with very small focus diameters down to 50 μm became possible. Typical focus diameter regimes of such laser sources can now be compared with regard to their effect on welding depth an...

JLA Vol:19 Iss:4 (Structuring electrospun polycaprolactone nanofiber tissue scaffolds by femtosecond laser ablation)

Authors:
Hae woon Choi
Laboratory for Multiscale Materials Processing and Characterization, The Ohio State University, 1248 Arthur E. Adams Dr., Columbus, Ohio 43221

Jed K. Johnson
Jin Nam
Department of Materials Science and Engineering, The Ohio State University, 477 Watts Hall, 2041 College Road, Columbus, Ohio 43210

Dave F. Farson
Laboratory for Multiscale Materials Processing and Characterization, The Ohio State University, 1248 Arthur E. Adams Dr., Columbus, Ohio 43221

John Lannutti
Department of Materials Science and Engineering, The Ohio State University, 477 Watts Hall, 2041 College Road, Columbus, Ohio 43210

JLA Vol:2 Iss:1 (Interaction of Excimer Laser Radiation with Solids)

Authors:
Walter W. Duley
Kevin Dunphy
Grant Kinsman
Stephen Mihailov
Laser Processing Laboratory, York University, 4700 Keele St., North York, Ontario, Canada M3J 1P3

We review the nature of the interactions that occur when excimer laser radiation impacts on different materials. The physical processes that occur during such interactions can be traced by subsequent physical and chemical analysis of the interface following the irradiation. We illustrate this approach with data obtained for a variety of materials including Cu, Al, polyimide and foamed polystyrene. We also discuss the processes that initiate material removal in transparent (wide ban...

JLA Vol:2 Iss:1 (Laser Cutting of Thin Plates)

Authors:
M. Bozzo
Dipartimento di Fisica — Universita di Genova, Istituto Nazionale Fisica Nucleare Via Dodecaneso 33,1‐16146 GENOA (Italy)

The technical problems which need to be solved when starting the study of a laser machining operation are not in the difficulty of reaching an adequate energy density, but in the correct evaluation of the behaviour of the material on which one needs to operate. The mechanism of laser energy interaction with matter has been extensively studied and is not the scope of this note. Particular emphasis will however be put on understanding and minimizing the effects of the heat energy remaining in the workpiece after the passage of the lase...

JLA Vol:2 Iss:1 (Laser Laparoscopy Contamination)

Authors:
Douglas E. Ott
420 Charter Blvd. Macon, Georgia 31210

JLA Vol:2 Iss:1 (Novel Speckle Velocimeter Using the Double Clipping Cross‐Correlation Method)

Authors:
H. Kitajima
T. Yoshida
N. Nakatsuka
T. Yamashita
Central R&D Lab., Omron Tateisi Electronics Co., Shimokaiinji, Nagaokakyo, Kyoto 617, Japan

A new speckle velocimeter using the cross‐correlation method was developed. Its optical system achieved wide working distance range of ±5mm and small measuring errors for various materials. Furthermore the realtime correlation processor for the clipped signals makes the cross‐correlation method applicable to in‐line measurement in factories.

JLA Vol:2 Iss:1 (On Laser Vibrometry of Rotating Targets: Effects of Torsional and In‐Plane Vibration)

Authors:
S. J. Rothberg
J. R. Baker
N. A. Halliwell
ISVR, University of Southampton, Highfield, Southampton S09 5NH, England

Vibration measurements on rotating surfaces are often referred to in the commercial literature as a major application of laser Doppler vibration transducers. This paper examines such use of these instruments and shows how the presence of a velocity component due to the rotation itself leads to spurious measurement dependence on both torsional vibration and motion perpendicular to the line of incidence of the laser beam. In addition, the scale of this dependence increases with both rotation speed and perpendicular distance between the l...

JLA Vol:2 Iss:1 (Simultaneous Measurement of Temperature and Size of Droplets in the Micrometer Range)

Authors:
N. Roth
K. Anders
A. Frohn
Institut fu¨r Thermodynamik der Luft‐ und Raumfahrt, Universita¨t Stuttgart, Pfaffenwaldring 31, D‐7000 Stuttgart 80, Federal Republic of Germany

A new optical instrument for simultaneous measurements of temperature and size of periodically generated droplets is described. With this instrument, basic phenomena such as droplet evaporation or combustion can be studied. The droplets, which are produced with a vibrating orifice droplet generator, can be injected into different environments to study, for example, evaporation in a rarefied media or combustion in a hot environment. To determine evaporation o...

JLA Vol:2 Iss:1 (Spray Characterization of a NASA MOD‐1 Nozzle)

Authors:
Dennis R. Alexander
Diego F. F. Gutierrez
Center for Electro‐Optics, University of Nebraska‐Lincoln (UNL), Lincoln, Nebraska, U.S.A.

An aerometrics Phase Doppler Particle Analyzer with Frequency Shifting (PDPA/FS) and a Laser Imaging and Video Processing System (LI/VPS) were used to perform a detailed analysis of the spray characteristics of a NASA MOD‐1 air assist nozzle. These results were compared to the results obtained using an earlier version of a Phase Doppler Particle Analyzer (P/DPA). The spray plume was analyzed under two sets of operating conditions. For Case I, a water pressure of 105 psia (723.95 kPa) and a...