JLA Vol:19 Iss:1 (Development of a monitoring system for quality prediction in laser marking using fuzzy theory)
Authors:
Young Whan Park
Taehyung Kim
Sehun Rhee
Department of Mechanical Engineering, Hanyang University, Sungdang-Gu, Seoul 133-791, KoreaWhen laser marking on a silicon wafer is performed during chip scale packaging processing, predicting the quality of the marked region may be necessary to increase productivity. Research to estimate marking line geometry after marking has been carried out. The methods to evaluate the line geometry after marking have limited applicability in production. Therefore, in this study, a process monitoring system was applied to laser micromaterial processing and an algorithm for quality estimation was developed using fuzzy theor...
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JLA Vol:19 Iss:1 (Effect of plasma on ultrashort pulse laser material processing)
Authors:
Chengde Li
S. R. Vatsya
S. K. Nikumb
Integrated Manufacturing Technologies Institute, National Research Council of Canada, London, Ontario N6G 4X8, CanadaMachining with high power ultrashort-pulsed lasers is becoming a preferred technique in material processing. However, the laser beam passing through a medium, e.g., air, experiences the self-focusing Kerr effect. High intensities increased further by self-focusing cause optical breakdown of the air, generating plasma. The associated diffusion compensates for the Kerr effect but it also deforms the laser beam. In the present article, properties of the plasma columns so induced by the femtosecond las...
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JLA Vol:19 Iss:1 (Laser beam shaping for microstructural control during laser surface melting)
Authors:
Jai Khare
Rakesh Kaul
P. Ganesh
Harish Kumar
R. Jagdheesh
A. K. Nath
Industrial CO2 Laser Section, Raja Ramanna Centre for Advanced Technology, P.O.: CAT, Indore, 452 013, IndiaLaser surface melting of austenitic stainless steel at high speed carries the risk of centerline solidification cracking due to the formation of tear-drop shaped melt pool. Laser beam shaping can be effectively employed to engineer surface microstructure of laser melted region by controlling the shape of associated melt pool. Results of the present study, involving numerical thermal simulation and experiments, demonstrated that by using ...
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JLA Vol:19 Iss:1 (Melt pool temperature and its effect on clad formation in pulsed Nd:yttrium-aluminum-garnet laser cladding of Stellite 6)
Authors:
S. Sun
Y. Durandet
M. Brandt
Industrial Laser Applications Laboratory, Industrial Research Institute Swinburne, Swinburne University of Technology, 533–545 Burwood Road, Hawthorn, VIC 3122, AustraliaThe effective melt pool temperature in pulsed Nd:yttrium-aluminum-garnet laser cladding of Stellite 6 was measured with a two-color pyrometer. The pulse peak temperature (Tp) and durations when the melt pool temperature is above the melting point of Stellite 6 powder (t1) and substrate (t2) in each pulse have been calculated and averaged. The effects of laser operating parameters (pulse energy, pulse frequency, spot...
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JLA Vol:19 Iss:1 (Procedure for the computation of hazards from diffusely scattering surfaces under the Z136.1-2000 American National Standard for Safe Use of Lasers)
Authors:
Robert J. Thomas
Benjamin A. Rockwell
Air Force Research Laboratory, Brooks AFB, Texas 78235-5128
Wesley J. Marshall
USACHPPM, Aberdeen Proving Ground, Maryland 21010-5403
Robert C. Aldrich
Mary F. Gorschboth
Sheldon A. Zimmerman
Dahlgren Division, Naval Surface Warfare Center, Dahlgren, Virginia 22448-5100
R. James Rockwell
Rockwell Laser Industries, Cincinnati, Ohio 45243The current national consensus standard for laser safety in the United States is the American National Standard for Safe Use of Lasers (ANSI Z136.1). The most recent standard, Z136.1-2000, incorporates ...
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JLA Vol:19 Iss:1 (Three-dimensional numerical approach for geometrical prediction of multilayer laser solid freeform fabrication process)
Authors:
Masoud Alimardani
Ehsan Toyserkani
Jan P. Huissoon
Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, CanadaThis article presents the development of a three-dimensional numerical method for predicting transient geometrical and thermal characteristics of multilayer laser solid freeform fabrication as a function of process parameters and material properties. In the proposed method, the thermal domain is numerically obtained, assuming the interaction between the laser beam and powder stream is to be decoupled. Once the melt pool boundary is obtained, the physical domain is discretized in a cross-se...
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JLA Vol:19 Iss:2 (Femtosecond laser microstructuring of hot-isostatically pressed zirconia ceramic)
Authors:
Niko Ba¨rsch
Laser Zentrum Hannover, Hollerithallee 8, 30419 Hannover, Germany
Kristian Werelius
Department of Prosthodontics, Johann Wolfgang Goethe University Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt/Main, Germany
Stephan Barcikowski
Fernando Liebana
Uwe Stute
Andreas Ostendorf
Laser Zentrum Hannover, Hollerithallee 8, 30419 Hannover, GermanyDensely sintered zirconia ceramics—especially hot-isostatically pressed forms of zirconia ceramics like hot-isostatically pressed yttria-stabilized tetragonal zirconia polycrystal (HIP Y-TZP)—have the potential of superseding conve...
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JLA Vol:19 Iss:2 (How Long After Laser Irradiation Should Cellular Responses be Measured to Determine the Laser Effect?)
Authors:
Denise Hawkins
Heidi Abrahamse
Laser Research Group, Faculty of Health Sciences, University of Johannesburg, P.O. Box 17011, Doornfontein, Johannesburg 2028, South AfricaBackground: Low level laser therapy (LLLT) is a type of photomodulation, which uses photons to modulate biological activity. This photobiological effect depends on the wavelength, dose, intensity, as well as cell culture conditions. One problem with most of the published data on low level laser irradiation is that most studies do not record the duration between the exposure and the evaluation. It has been established that a single dose of 5 J/cm2 stimulates cell prolifer...
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JLA Vol:19 Iss:2 (Interaction of a focused laser beam and a coaxial powder jet in laser surface processing)
Authors:
O. O. Diniz Neto
A. M. Alcalde
Instituto de Fi´sica, Universidade Federal de Uberlaˆndia, Caixa Postal 593, CEP 38400-902, Uberlaˆndia MG, Brazil
R. Vilar
Instituto Superior Te´cnico and ICEMS, Av. Rovisco Pais, 1096-001 Lisboa, PortugalLaser cladding, laser alloying, and laser free-form manufacturing are promising techniques where a laser beam is frequently used in conjunction with a coaxial powder jet for surface treating or rapid manufacturing. In the present work, a computational model was developed and used to simulate several experimental setups in order to optimize the processing conditions. More specifically, t...
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JLA Vol:19 Iss:2 (Intrabeam viewing of extended-source lasers with telescopes)
Authors:
Wesley J. Marshall
E. Christopher Brumage
David H. Sliney
U.S. Army Center for Health Promotion and Preventive Medicine, AberdeenProving Ground, Maryland 21010-5403Magnifying optics can increase the hazards for intrabeam viewing of lasers. Although it is rather straightforward to evaluate these increased hazards for point-source lasers at distance, limited information is available for determining the hazards from viewing extended-source lasers from within the beam when magnifying optics are used. Since intrabeam viewing of nearly all lasers results in an extremely small retinal image, commonly known as a “point source,” extended-source m...
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