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:4 Iss:2 (A Systematic Method for the Design of a Multivariable Controller Actuating Power and Speed during a CO₂ Laser Surface Treatment)

Authors:
F. Bataille
J. M. Cerez
D. Kechemair

Temperature control systems actuating laser power and scanning velocity during laser surface hardening have already been presented. This paper exposes a systematic method for the design of a multivariable Linear Quadratic Gaussian controller adapted to this laser treatment. The preliminary identification step and the controller design are included. This corrector insures a better regulation and the generality of the method hopefully allows an easier adaptation to other laser treatments, materials or absorbing coatings.

JLA Vol:16 Iss:2 (Laser short pulse heating of copper: Thermo–elasto–plastic analysis)

Authors:
A. F. M. Arif
B. S. Yilbas
ME Department, KFUPM. Dhahran, Saudi Arabia

Laser short pulse heating of metallic substrates results in excessive electron temperatures in the surface vicinity. This gives rise to nonequilibrium energy transport in the region irradiated by a laser beam. Moreover, the thermomechanical coupling effect should be incorporated into the energy transport equation as lattice site temperature increases. In the present study, laser short pulse heating of copper is considered. The electron kinetic theory approach is employed to model the nonequilibrium heating process while thermomechanical coupling is introduced in the energy transport equation t...

JLA Vol:20 Iss:3 (Diode-pumped solid state laser light sources for confocal laser scanning fluorescence microscopy)

Authors:
Mårten Stjernstro¨m
Department of Applied Physics, Royal Institute of Technology, SE-106 91 Stockholm, Sweden and Department of Chemistry, Royal Institute of Technology, SE-100 44 Stockholm, Sweden

Fredrik Laurell
Hjalmar Brismar
Department of Applied Physics, Royal Institute of Technology, SE-106 91 Stockholm, Sweden

Diode-pumped solid-state lasers (DPSSLs) have been integrated as light sources in confocal laser scanning microscopy (CLSM). The standard argon ion laser at 488 nm is compared with a DPSSL operating at 473 nm in terms of noise and CLSM image characteristics. The equally high fluorescence image quality togeth...

JLA Vol:23 Iss:3 (Spatter in laser welding)

Authors:
A. F. H. Kaplan
J. Powell
Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-971 87 Luleå, Sweden

Spatter, the ejection of melt from a weld pool, is a major problem whenever it occurs in a welding process. The ejection of droplets from the weld metal results in a weld with underfill, undercuts, craters, blowholes, or blowouts—all of which can have a detrimental effect on the mechanical properties of the weld. This paper presents a systematic description of the different types of spatter phenomena which occur during laser welding. A categorization system is proposed to facilitate the comparison and combination ...

JLA Vol:1 Iss:1 (High‐Speed Laser Welding Discontinuities)

Authors:
Charles E. Albright
Shichan Chiang
Department of Welding Engineering, Ohio State University, Columbus, Ohio

JLA Vol:9 Iss:6 (… .But is it really safe?)

Authors:
Peter A. Smith
DERA Centre for Human Sciences, Farnborough, Hampshire, U.K.

JLA Vol:3 Iss:2 (Laser Applications in Criminalistics)

Authors:
E. R. Menzel
Center for Forensic Studies, Department of Physics, Texas Tech University, Lubbock, Texas 79409

Lasers find application in numerous areas of criminalistics, such as fiber analysis, document examination and serology. Their widest use, however, is in detection of latent fingerprints. Several routine procedures for obtaining laser‐excited fingerprint fluorescence on a range of surfaces have been developed. However, many surfaces fluoresce so strongly themselves that they are not amenable to these procedures. Time‐resolved luminescence imaging is being investigated to permit detection of fingerprints on such surfaces.

JLA Vol:16 Iss:4 (Dimensional and material characteristics of direct deposited H13 tool steel by CO₂ laser)

Authors:
J. Choi
Y. Hua
Department of Mechanical and Aerospace Engineering and Engineering Mechanics, University of Missouri, Rolla, Missouri 65409-1060

Laser aided direct metal/material deposition process builds metal parts layer-by-layer directly from the computer aided design representation. Success of this technology in the die and tool industry depends on the parts quality to be achieved. To get designed geometric dimensions and material properties, delicate control of the process variables such as laser power, spot diameter, traverse speed, and powder mass flow rate is critical. With a closed loop optical height control system, the dimensional accuracy was achieved ...

JLA Vol:21 Iss:2 (Corrosion performance and restoration of laser-formed metallic alloy sheets)

Authors:
Z. Liu
C. Guzma´n
H. Liu
A. Anacleto
T. Francisco
M. Abdoalshafie
L. Ma
O. Abodunrin
P. Skeldon

Previous studies of laser forming have been focused on understanding the laser forming mechanisms, investigating the effects of important laser process parameters on deformed shape, and modeling the forming process. Although microstructures and mechanical properties have received some attention, no work has addressed corrosion behavior of laser-formed components. However, laser forming is a thermal process with substantial thermal cycles required; sensitization of microstr...