JLA Vol:19 Iss:3 (Interaction between laser beam, process effects, and structural properties during welding using models based on the finite element analysis)
Authors:
Loucas Papadakis
Tobias Hornfeck
Michael F. Zaeh
Institute for Machine Tools and Industrial Management (iwb), Technische Universitaet Muenchen, Boltzmannstr. 15, 85747 Garching, GermanyThe aim of this contribution is to study the influence of the laser beam on the structural properties of sheet metals during welding by considering particular process effects. The interaction between process parameters, such as the exact positioning of the laser focus and the weld gap between sheets, affects the stability of the laser beam welding process and thus the quality of weld seams. Furthermore, additional interaction of the welding process with manufacturing ...
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JLA Vol:19 Iss:3 (Nanoscale self-assembled surface structures of silicon at femtosecond excitation)
Authors:
M. El-Bandrawy
A. A. Bugayev
Applied Research Center, Old Dominion University, Newport News, Virginia 23606The results are presented for single picosecond and femtosecond pulse ablation of silicon which creates a continuum of the dominant filament structures with periods as small as 200 nm. It is assumed that the instability of the capillary waves is responsible for the phenomenon observed. Also it is shown that for single pulse femtosecond excitation the filament structure formation is accompanied by a fine substructure generation with a period of 60 nm. The mechanism of this substructure remains obscure.
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JLA Vol:19 Iss:3 (Rationale for laser classification measurement conditions)
Authors:
David H. Sliney
Wesley J. Marshall
E. Christopher Brumage
Laser/Optical Radiation Program, U.S. Army Center for Health Promotion and Preventive Medicine, Aberdeen Proving Ground, Maryland 21010-5403The basic concept of laser hazard classification with four fundamental risk groups and several subclasses is well understood by most laser users. However, many readers of laser safety standards are frequently puzzled by the rigid measurement conditions applied for hazard classification, even if this is normally a task performed by the laser manufacturer and not by a laser user or a Laser Safety Officer. The historical rationale for the measurement conditi...
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JLA Vol:19 Iss:3 (Single-Pass and Multi-Pass Laser Cutting of Si–SiC: Assessment of the Cut Quality and Microstructure in the Heat Affected Zone)
Authors:
F. Quintero
J. Pou
F. Lusquin˜os
A. Riveiro
M. Pe´rez-Amor
Departamento Fi´sica Aplicada, E.T.S. Ingenieros Industriales, University de Vigo, 36310 Vigo, Spain
A. J. S. Fernandes
Department of Physics, University of Aveiro, 3810-193 Aveiro, PortugalExperimental investigations on the laser cutting of thick silicon infiltrated silicon carbide (Si–SiC) elements are presented. Si–SiC is a fully dense ceramic composite with high hardness and chemical and thermal stability, which makes it a valuable material in severe conditions. However, machining is still a challenging task. A...
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JLA Vol:19 Iss:3 (Surface treatment of welded duplex stainless steels by diode laser)
Authors:
Edoardo Capello
Moreno Castelnuovo
Barbara Previtali
Maurizio Vedani
Mechanical Department, Politecnico di Milano, Via Bonardi 9, 20133 Milano, ItalyThe good mechanical properties and the high corrosion resistance are some of the most appreciated characteristics of duplex stainless steels, which are now widely used in several application fields. One limit in the duplex stainless steel diffusion derives from their complex structure: The optimal 50%-50% austenite to ferrite ratio is lost after welding and measures must be taken to improve the as welded structure. The joint can be postweld heat treated or a filler wire having a tailored co...
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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 ChinaFemtosecond 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...
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JLA Vol:19 Iss:4 (Absorption of laser irradiation in a porous powder layer)
Authors:
R. W. McVey
R. M. Melnychuk
Department of Engineering Science and Mechanics and the Applied Research Laboratory, Pennsylvania State University, University Park, Pennsylvania 16801
J. A. Todd
Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania 16801
R. P. Martukanitz
Applied Research Laboratory, Pennsylvania State University, State College, Pennsylvania 16803An analytical relationship was derived to describe the amount of energy absorbed within preplaced powder during the laser deposition process. The relationship, which reflects an exponential decay of Beer&ndas...
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JLA Vol:19 Iss:4 (Bench-top antigen detection technique that utilizes nanofiltration and fluorescent dyes which emit and absorb light in the near infrared)
Authors:
Vanessa A. Varaljay-Spence
Department of Biological, Geological and Environmental Sciences, Cleveland State University, Cleveland, Ohio 44115, NASA Glenn Research Center at Lewis Field, Brook Park, Ohio 44135, and Department of Microbiology, University of Georgia, Athens, Georgia 30602
Maximilian C. Scardelletti
NASA Glenn Research Center at Lewis Field, Brook Park, Ohio 44135This article discusses the development of a bench-top technique to detect antigens in fluids. The technique involves the use of near infrared (NIR) fluorescent dyes conjugated to antibodies, centrifugation, nanofilters, and spectrometry. The system used to detect the antigens utili...
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JLA Vol:19 Iss:4 (Development and performance evaluation of solid freeform fabrication system by using dual laser sintering process)
Authors:
Dong Soo Kim
Won Hee Lee
Sung Woo Bae
Intelligence and Precision Machinery Research Division/IT Machinery Research Center, Korea Institute of Machinery & Materials, 171, Jang-Dong, Youseong-Gu, Daejeon, South Korea
Kyung Hyun Choi
School of Mechanical Engineering, Cheju National Eniversity, Cheju, South KoreaA solid freeform fabrication (SFF) system using selective laser sintering (SLS) is currently recognized as a leading process and SLS extends the application to machinery and automobiles due to the various materials employed. In order to develop a more elaborate and rapid system for fabricating large objects compared to ...
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JLA Vol:19 Iss:4 (Experimental observation of keyhole shapes in the laser welding of aluminum blanks)
Authors:
B. J. Aalderink
Netherlands Institute for Metals Research, P.O. Box 217, 7500 AE Enschede, The Netherlands
R. G. K. M. Aarts
University of Twente, Laboratory of Mechanical Automation, P.O. Box 217, 7500 AE Enschede, The Netherlands
D. F. de Lange
Netherlands Institute for Metals Research, P.O. Box 217, 7500 AE Enschede, The Netherlands
J. Meijer
University of Twente, Laboratory of Mechanical Automation, P.O. Box 217, 7500 AE Enschede, The NetherlandsA camera-based in situ monitoring system for the Nd:yttrium–aluminum–garnet laser keyhole welding process of aluminium has been developed. The...
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