JLA Vol:22 Iss:2 (Nd:YAG laser welding of titanium alloys using a directed gas jet)

Authors:
Jonathan Blackburn
Laser Processing Research Centre, The University of Manchester, Manchester M60 1QD, United Kingdom

Chris Allen
Paul Hilton
TWI Ltd., Granta Park, Abington, Cambridge CB21 6AL, United Kingdom

Lin Li
Laser Processing Research Centre, The University of Manchester, Manchester M60 1QD, United Kingdom

The increasing utilization of titanium alloys in the aerospace industry, a direct result of socioeconomic pressures, has created the need for a production process which can produce high quality near-net-shape titanium alloy components. Keyhole laser welding is a joining technology which could be utilized for t...

JLA Vol:1 Iss:2 (Laser Applications in Biomedicine. Part II: Clinical Applications)

Authors:
J. Stuart Nelson
Michael W. Berns
Beckman Laser Institute and Medical Clinic, University of California, Irvine, 1002 Health Sciences Road East, Irvine, California 92715

JLA Vol:23 Iss:2 (Experimental investigation of laser shock peening using femtosecond laser pulses)

Authors:
Dongkyun Lee
Elijah Kannatey-Asibu
Department of Mechanical Engineering, The University of Michigan, Ann Arbor, Michigan 48105-2125

In this study, the feasibility of laser shock peening using ultrafast laser pulses was experimentally investigated. A top coating of zinc with a water confining layer was applied in the investigation. The zinc coating was used for the thermoprotective effect. A high numerical aperture (NA≅0.5) aspheric lens was used to minimize the optical breakdown of water. Microhardness measurements were made on the top surface of the shock peened specimen and compared with the original material hardness. The results provide useful insight on...

JLA Vol:7 Iss:3 (Laser beam surveying, refractive index measurements and the making of a 360° reflection hologram)

Authors:
David Foster
Notre Dame High School, 596 South Second St., San Jose, California 95112, U.S.A.

Triangulation measurements, using a laser to find the height of a room and of buildings, will be described first. This will be followed by triangulation and laser beam divergence measurements for range finding. The use of a hollow prism to hold liquids, whose refractive indicies are to be found, will then be described. The final topic will describe how a 360° reflection hologram was made at Notre Dame High School, utilizing three lasers and beam spreaders and four lasers and beam spreaders. The 360° hologram, made by a student, will be available for viewing.

JLA Vol:16 Iss:1 (Influence of surface preparation and process parameters on the porosity generation in aluminum alloys)

Authors:
A. Haboudou
P. Peyre
CLFA, avenue Prieur de la Côte d’or, 94114 Arcueil, France

A. B. Vannes
Ecole Centrale de Lyon, Ecully, France

The 4 kW cw Nd:yttrium–aluminum–garnet laser welding of solid solution hardened A5083 (5% Mg) and precipitation-hardened A356 (7% Si) alloys, sensitive to porosity formation was carried out at different welding speeds, under He gas shielding, and for partial penetration conditions, on bead on plate configuration. The porosity formation was examined through observation and evaluation of weld beads, based on x-ray radiography inspection coupled with image analysis, and quantification of gas...

JLA Vol:20 Iss:2 (Design and validation of a hybrid laser/water-jet machining system for brittle materials)

Authors:
Dinesh Kalyanasundaram
Gamal Shehata
Clayton Neumann
Pranav Shrotriya
Pal Molian
Department of Mechanical Engineering, Laboratory for Lasers, MEMS and Nanotechnology, Iowa State University, Ames, Iowa 50011-2161

A unique laser/water-jet (LWJ) cutting head has been designed, built, and interfaced with a CO₂ laser for cutting and scribing of hard and brittle ceramic materials. Alumina samples were used to validate the effectiveness of the LWJ cutting head in thermal fracture mode. The results were compared with vaporization mode (focused beam) as well as thermal fracture mode (defocused beam) of air-assisted laser c...

JLA Vol:9 Iss:6 (Amendments to the Center for Devices and Radiological Health Federal Performance Standard for laser products)

Authors:
Jerome E. Dennis
Center for Devices and Radiological Health, Food and Drug Administration, Rockville, MD, U.S.A.

Federal law requires that all laser products that are imported into or introduced into commerce in the United States comply with the performance standard published in the Code of Federal Regulations (CRF), Title 21, Parts 1040.10 and 1040.11, administered by the Center for Devices and Radiological Health (CDRH), US Food and Drug Administration. Although it contains somewhat different requirements for hazard classification, engineering controls and labeling, the ANSI Z136.1 standard defers to the CDRH standard. The CDRH standard became effective in August, 1976 and ...

JLA Vol:3 Iss:2 (Precision Limits of the Estimation of the Parameters of Fo¨rster Models of Fluorescence Waveforms)

Authors:
L. Jonathan Dowell
Los Alamos National Laboratory, Los Alamos, NM 87545

The author examined the precision of maximum‐likelihood‐derived, nonlinear least‐squared‐error algorithms that are suitable for laboratory implementation and that estimate the parameters of Fo¨rster models of fluorescence. The estimation precision for these parameters is limited by inherent noise in the fluorescence‐waveform measurement. This paper examines the Fo¨rster model and its recent applications and discusses parameter estimations for models of energy transfer by different wavefunction interactions. It presents the results of Monte Carlo simulation studi...

JLA Vol:14 Iss:2 (Deformation behavior and microstructural changes of a hardened high carbon alloy steel in laser bending)

Authors:
K. C. Chan
J. Liang
Department of Manufacturing Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong

In this article, the deformation behavior and microstructure of a hardened high carbon steel in laser bending were examined. A CO₂ laser unit (TEM₀₀) was used to bend the samples at different laser powers, scanning velocities, and number of scans. A relatively linear relationship between bending angle and number of scans was obtained at laser powers of 150 and 200 W and at a scanning velocity of 30 mm/s. A threshold heat input of about 3.25 J/mm was observed, below which bending was unlikely to occur. The bending angle was al...

JLA Vol:18 Iss:3 (Femtosecond laser bulk micromachining of microfluid channels in poly(methylmethacrylate))

Authors:
Dave F. Farson
Hae Woon Choi
Department of Industrial, Welding and Systems Engineering, The Ohio State University, Columbus, Ohio 43221

Chunmeng Lu
L. James Lee
Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, Ohio 43221

Internal channels in a polymer are widely used in biotechnology applications such as DNA stretching and in devices such as micrototal analysis systems and lab on a chip systems. For manufacturing prototype devices, femtosecond pulsed laser energy has been used to implement a convenient direct write bulk-machining process in glass. In this technique, the laser beam is focu...