JLA Vol:19 Iss:2 (Laser micro adjustment—from new basic process knowledge to the application)
Authors:
Michael Schmidt
Manfred Dirscherl
Matthias Rank
Maik Zimmermann
Bayerisches Laserzentrum gGmbH, Erlangen, GermanyLaser micro bending and its controlled variant, laser micro adjustment, have been known for many years. Different theories on the working principle, mainly differing in interaction time and energy flux density, have been evolved and experimentally proven. The temperature gradient mechanism and the buckling mechanism are the most established laser adjustment techniques. However, as interaction times are getting shorter with the development of new laser sources, additional phenomena are being detected and new interaction princi...
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JLA Vol:19 Iss:2 (Nanoparticles as potential risk during femtosecond laser ablation)
Authors:
Stephan Barcikowski
Anne Hahn
Boris N. Chichkov
Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover, GermanyDuring femtosecond (fs) laser ablation, fumes with remarkably low emission mass rates compared to conventional laser processes are generated. In this case the size of particles released in the workplace is relatively small, in the range of 10 nm–1 μm. The high amount of inhalable particles generated during femtosecond laser ablation has to be considered as a potential health risk, demanding quantification. In order to provide safety-related statements on nonbeam hazards during laser materials processing, the partic...
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JLA Vol:19 Iss:2 (Removal of layers of corrosion from steel surfaces: A qualitative comparison of laser methods and mechanical techniques)
Authors:
Y. S. Koh
Kiruna Center for Conservation of Cultural Property, Kiruna, Sweden and Luleå University of Technology, Luleå, Sweden
J. Powell
Luleå University of Technology, Luleå, Sweden and Laser Expertise Ltd., Nottingham, United Kingdom
A. F. H. Kaplan
Luleå University of Technology, Luleå, SwedenA series of steel substrates with precisely grooved surfaces were produced and subsequently corroded under controlled conditions. The oxidized surfaces were then cleaned by one of eight methods, three of which were mechanical (brushing, micro blasting with Al2O3 or glass) and five o...
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JLA Vol:19 Iss:2 (Welding of titanium and other refractory metals with a free pulse shaping laser)
Authors:
Karsten Richter
Lasag AG, Switzerland
Uwe Reisgen
Wilfried Behr
Forschungszentrum Ju¨lich GmbH, Germany
Ronald Holtz
Lasag AG, SwitzerlandRefractory metals are used as construction materials for specific applications. Amongst the refractory metals, titanium has a special status due to its multi-faceted property profile and its comparatively low price. Titanium materials have outstanding properties, such as excellent resistance to corrosion and very high strength at low densities, which lead to their preferred use in chemical engineering and as a structural material in lightweight construction. Due to the high affin...
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JLA Vol:19 Iss:3 (Characteristics of the laser clad metal made with powder mixture of Co-based alloy and vanadium carbide)
Authors:
Guojian Xu
Munaharu Kutsuna
Zhognjie Liu
Graduate School of Engineering, Nagoya University, 1 Furo-cho, Chikusa-ku, Nagoya 464-8603, JapanA powder mixture of Co-based alloy (Stellite-6) and vanadium carbide (VC) was deposited to substrates of SM400B mild steel and SUS304 stainless steel using a 2.4 kW cw CO2 laser. The mechanism of crack for clad metal was investigated by changing the VC weight fraction in the range of 0%–56%. The microstructures of the clad layer for matrix of Co-based alloy can be classified into two types—hypoeutectic structure (0–12 wt % VC) and hypereutectic structure (13–56&ens...
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JLA Vol:19 Iss:3 (Estimating spot size and relating hole diameters with fluence and number of shots for nanosecond and femtosecond laser ablation of polyethylene terephthalate)
Authors:
Claire Mullan
Gerard M. O’Connor
Sebastian Favre
Diana Ilie
Thomas J. Glynn
National Centre for Laser Applications, National University of Ireland, Galway, IrelandThe relationship between focused spot size, pulse energy, and ablated hole diameter was explored using 266 nm nanosecond pulses and 775 nm femtosecond pulses on polyethylene terephthalate. The spot size of a Gaussian laser beam can be deduced from the diameters of holes machined with single shots at different pulse energies but the results can be influenced by such issues as the thickness of the material and the range of fluence chosen. These limit...
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JLA Vol:19 Iss:3 (Evaluation of subsurface dentin microhardness after Er: yttrium-aluminum-garnet and Nd: yttrium-aluminum-garnet laser irradiation)
Authors:
Leily Macedo Firoozmand
Andressa Pereira da Silva
Carlos Rocha Gomes Torres
Department of Restorative Dentistry, Sa˜o Jose´ dos Campos School of Dentistry, Sa˜o Paulo State, BrazilBackground and objectives: To assess the microhardness of dentin subsurface after Er: yttrium-aluminum-garnet (YAG) and Nd:YAG laser irradiation. Study design/materials and methods: Twenty-four bovine incisors, without pulp, were used. The vestibular surface was worn out until the dentin was reached and divided in mesial and distal regions. The samples were divided into two groups: GI-distal, irradiated by Er:YAG laser, and GII-distal, irradiated by Nd:YA...
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JLA Vol:19 Iss:3 (Femtosecond pulsed laser microfabrication of SiC MEMS microgripper)
Authors:
Monica Vendan
Pal Molian
Mechanical Engineering Department, Iowa State University, Ames, Iowa 50011We report the capability of an ultrafast laser to pattern an electrostatic-comb-drive microgripper in the chemically difficult-to-etch 3C-SiC thin films. A microgripper with overall dimensions 1.2 mm×0.35 mm and a gap of 20 μm was designed and fabricated for the purpose of grasping and transporting microscale objects in hostile and harsh environments. Atmospheric pressure chemical vapor deposition was used to deposit thin films (∼2 μm) of 3C-SiC on 〈100〉 silicon substrates. A Ti:sapphire laser with 120 fs pulse wid...
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JLA Vol:19 Iss:3 (Gas investigation for laser drilling)
Authors:
Matthieu Schneider
GIP GERAILP,16 bis Avenue Prieur de la Coˆte d’Or 94114 Arcueil Cedex, France
Laurent Berthe
Re´my Fabbro
Maryse Muller
Mariette Nivard
Laboratoire pour l’Application des Lasers de Puissance (UPR CNRS no 1578), 16 bis Avenue Prieur de la Coˆte d’Or 94114 Arcueil Cedex, FranceThis article deals with the gas effect on percussion laser drilling in ms pulse duration range. On the one hand, the flow of assistance gas jet is investigated with and without a target using a strioscopy setup and Pitot’s tube. By this way, the position of shock waves in the supersonic...
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JLA Vol:19 Iss:3 (Improving coaxial measurements in laser welding by correcting distortions of a laser focus lens with a wide field of view)
Authors:
Jorg Entzinger
Dimitrios Iakovou
Ronald Aarts
Johan Meijer
Mechanical Automation Laboratory, University of Twente, Faculty of Engineering Technology Horst-CTW, P.O. Box 217, 7500 AE Enschede, The NetherlandsA compact, lightweight, and multifunctional head for robotic laser welding applications has been equipped with a camera to provide a real time image stream of the work piece for seam teaching, tracking, and inspection purposes [D. Iakovou, R. G. K. M. Aarts, and J. Meijer, “Integrated sensors for robotic laser welding,” in Proceedings of the Third International WLT Conference on Lasers in Manufacturing, Munich, German...
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