JLA Vol:20 Iss:4 (Tailored hybrid blank production—New joining concepts using different solders)

Authors:
C. von der Haar
L. Engelbrecht
O. Meier
A. Ostendorf
H. Haferkamp
Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover, Germany

A consistent lightweight concept necessitates the combination of different lightweight materials. Because of the significant weight reduction, multimaterial design is becoming more and more interesting for the transportation industry. Mixed material concepts are partially limited because of the insufficient deformation behavior of the joining seams. To overcome this limitation, a brazing process has been developed in which aluminium and steel can be joined, with an enhanced deformation beha...

JLA Vol:25 Iss:5 (Numerical and experimental study of the effect of groove on plasma plume during high power laser welding)

Authors:
Cai Yan
Xie Wen-Jing
Wu Yue
Sun Da-Wei
Wu Yixiong
Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China and Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai 200240, China

The influence of groove on the static feature and dynamic behavior of plasma plume during high power CO₂ laser welding process was studied using a hydrodynamic three-dimensional model and corresponding experiments. The temperature, composition, and velocity of plasma plume along the incident path of laser beam were computed. The static morphology of plasma plume was analyzed through both models ...

JLA Vol:23 Iss:4 (Investigation of the effect of irradiance and pulse duration in industrial percussion laser-drilling of Waspaloy)

Authors:
Robin Bright
Harris L. Marcus
Institute of Materials Science and the Department of Chemical, Materials, and Biomolecular Engineering, University of Connecticut, Storrs, Connecticut 06269-3136

As the use of pulsed lasers in the manufacture of cooling holes in high-temperature gas-turbine engine components continues to increase, understanding the material behavior during laser-material interaction and the subsequent effects on hole quality becomes critical. In this study, atomic emission spectroscopy is used to monitor the optical characteristics of ejected material during percussion laser-drilling of Waspaloy over irradiance and pulse duration values in the ranges...

JLA Vol:6 Iss:2 (National Science Foundation undergraduate faculty enhancement workshop on advanced laboratory experiments using lasers)

Authors:
James E. Parks
Charles S. Feigerle
Robert Deserio
Joseph Wiest

A National Science Foundation undergraduate faculty enhancement workshop on advanced laboratory experiments using lasers was developed at the University of Tennessee, Knoxville, with the authors as the instructors. The workshop emphasized the development and implementation of laser‐based experiments primarily suitable for advanced undergraduate physics and chemistry laboratories. Participants gained practical, hands‐on experience in approximately 16 unique laser‐based experiments in atomic and molecular physics, physical chemistry, and biophysics. The wo...

JLA Vol:14 Iss:4 (Determining source size from diode laser systems)

Authors:
Wesley J. Marshall
U.S. Army Center for Health Promotion and Preventive Medicine, Aberdeen Proving Ground, Maryland 21010-5403

Although hazard classification is performed at predefined distances, the maximum permissible exposure (MPE) for extended-source diode lasers decreases as the distance from the laser increases. The MPE depends on the apparent angular subtense of the source, which is simply the magnified image of the emitting diode. Small diameter beams require special consideration.

JLA Vol:18 Iss:4 (Cutaneous sensation threshold for 3.8 μm radiation from a short duration pulsed laser on the calves of human subjects: A pilot study)

Authors:
Thomas E. Johnson
Michael J. Roy
Department of Environmental and Radiological Health Sciences, Colorado State University, 1618 Campus Delivery, Fort Collins, Colorado 80528 and Department of Medicine, School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, Maryland 20814

The objective of this study was to determine the threshold for sensing a 3.8 μm laser on the skin. The identification of the skin sensation threshold for invisible lasers is useful in providing scientific guidance to the safety community regarding accidental skin exposures. Knowledge of the level of sensation of lasers might be used to s...

JLA Vol:1 Iss:3 (Laser Welding of Plastics in Low and High Gravity Environments)

Authors:
R. E. Mueller
W. W. Duley
CRESS and Laser Processing Laboratory, York University, Toronto, Ontario, Canada M3J 1P3

S. MacLean
M. Garneau
B. Tryggvason
Canadian Astronaut Office, National Research Council, Ottawa, Ontario, Canada K1A 0R6

W. F. J. Evans
Atmospheric Environment Service, 4905 Dufferin Street, Downsview, Ontario M3H 5T4

Initial results of a series of laser processing experiments performed under the micro‐gravity conditions supplied by NASA's KC‐135 aircraft are presented. Weld morphologies of polypropylene and polyethylene were obtained under both hyper‐ and hy...

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

JLA Vol:2 Iss:3 (Erbium:YAG (2.94 &mu;<em>m) Laser Effects on Dental Tissues</em>)

Authors:
James A. Hoke
E. Jeff Burkes
Edward D. Gomes
Myron L. Wolbarsht

Past trials with soft and calcified tissues have demonstrated that long pulse train (2.5 μs) Er:YAG (2.94 μm) laser may be used to ablate tooth structure of human teeth. Determination of physical and thermal damage to surrounding tissue during removal of enamel and dentin is a primary objective of this study. Extracted human teeth with thermal probes imbedded in the pulp chambers were submitted to cavity preparation using an Erbium YAG laser with water mist. Wavelength selection as well as use of a water mist during the procedure resulted in efficient tissue...

JLA Vol:17 Iss:2 (Modeling of laser deposition and repair process)

Authors:
Lijun Han
Kaushik M. Phatak
F. W. Liou
Department of Mechanical and Aerospace Engineering, University of Missouri-Rolla, Rolla, Missouri 65409-1350

Laser aided deposition is a material additive based manufacturing process via metallurgically bonding the deposited material to the substrate. Due to its capability to bond various materials together, it becomes an attractive technology for part repair in small scale. However, the details of the process remain an active area for research because of the complicated interactions involved. In this study, a mathematical model was established to investigate thermal and mass transportation phenomena, which incl...