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...

JLA Vol:21 Iss:4 (How the laser started)

Authors:
Charles Townes
Department of Physics, University of California, Berkeley, California 94720

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: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:15 Iss:4 (Induction heat treatment of laser welds)

Authors:
Claus Bagger
Joakim Ilsing Sørensen
Flemming O. Olsen
Manufacturing Engineering and Management, Materials and Process Technology, Technical University of Denmark, Building 425, DK-2800 Lyngby, Denmark

In this article, a new approach based on induction heat treatment of flat laser welded sheets is presented. With this new concept, the ductility of high strength steels GA260 with a thickness of 1.8 mm and CMn with a thickness of 2.13 mm is believed to be improved by prolonging the cooling time from 750 to 450 °C. Initially, a simple analytical model was used to calculate the ideal energy contributions from a CO₂ high power laser s...

JLA Vol:19 Iss:4 (Ablation and cutting of silicon wafer and micro-mold fabrication using femtosecond laser pulses)

Authors:
Ying Wang
Nengli Dai
Yuhua Li
Xinlin Wang
Peixiang Lu
Wuhan National Laboratory for Optoelectronics and School of Optoelectronics Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, People’s Republic of China

Femtosecond laser micromachining of silicon wafer at a relatively higher energy fluence level (>50 J/cm²) is investigated. Laser ablating spots and cutting kerfs are examined by means of charge coupled device camera and scanning electron microscopy. The area of ablated spots increases linearly with increasing the shot number from 1 to 16 and shows saturation with t...

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:14 Iss:1 (Multiple reflection and its influence on keyhole evolution)

Authors:
Hyungson Ki
Pravansu S. Mohanty
Jyotirmoy Mazumder
Center for Laser Aided Intelligent Manufacturing, Department of Mechanical Engineering and Applied Mechanics, The University of Michigan, Ann Arbor, Michigan 48109-2125

In laser drilling and keyhole welding, multiple reflection phenomena determine how the energy is transferred from the laser beam to the workpiece, and, most importantly, all other physics such as fluid flow, heat transfer, and the cavity shape itself depend on these phenomena. In this study, a multiple reflection model inside a self-consistent (or self-evolving) cavity has been developed based on the level set method and ray tracing t...