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August 2012

Volume 24, Issue 3 (partial)

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Stability limits of laser drilled hole arrays on large areas

Nelli Hambach, Claudia Hartmann, Jens Holtkamp, and Arnold Gillner

J. Laser Appl. 24, 032001 (2012); http://dx.doi.org/10.2351/1.3702944 (5 pages)

Online Publication Date: 19 April 2012

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Large area microdrilling utilizing short pulsed solid state lasers is a promising manufacturing technique for filtration technology. High degree of perforation and high quality of the drilled hole arrays regarding roundness and diameter variation of holes are the main challenges. The goal is to achieve a high degree of perforation with a high number of round holes on a constant pitch. The resulting variation of hole roundness and mechanical stability limitations of the percussion drilled foil using a ns pulsed laser source with a wavelength of 355 nm when drilling a 50 µm thin aluminum foil are presented here. Different drilling strategies are investigated in relation to roundness, hole diameter, and heat propagation. The quality of drilled holes decreases with decreasing pitch and hole diameter. This can be related to thermal effects and pointing stability of the laser beam. Both effects are directional in the setup used here and can, therefore, be superposed positively or negatively. Due to adapted superposition of the effects, the roundness of the holes can be maximized.
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42.62.Cf Industrial applications
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
81.20.Wk Machining, milling

Optimization of the aluminum oxide properties for adhesive bonding by laser surface pretreatment

Rico Rechner, Irene Jansen, and Eckhard Beyer

J. Laser Appl. 24, 032002 (2012); http://dx.doi.org/10.2351/1.4704854 (9 pages)

Online Publication Date: 19 April 2012

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The laser pretreatment of AlMg3 has been conducted to investigate the influence of the fluence on the oxide properties. Therefore, the aluminum surface is pretreated by a fiber laser and subsequently analyzed by SEM, EDX, and XPS. Finally, mechanical measurements are performed on adhesively bonded specimens to study the surface properties produced. For the purpose of comparison, the two state-of-the-art pretreatment methods etching and phosphoric acid anodizing are also investigated. The results show that laser pretreatment changes the properties of the aluminum surface and especially those of the oxide layer. The latter grows in comparison to the natural oxide layer of etched surfaces but does not reach the dimensions of an electrochemically formed oxide layer. Mechanical testing showed that the laser treated specimens reach and exceed the strength values of etched and anodized surfaces, respectively. However, strength after aging does not keep up with the good long-term resistance of anodized aluminum, but it exceeds by far the values obtained for etched surfaces. Overall the study showed that optimizing the oxide layer by laser pretreatment leads to improved adhesion and enhances the strength of adhesively bonded aluminum. Therefore, the laser pretreatment of aluminum is an excellent alternative to wet (electro)chemical processes.
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42.62.Cf Industrial applications
81.40.Cd Solid solution hardening, precipitation hardening, and dispersion hardening; aging
81.65.Cf Surface cleaning, etching, patterning
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
82.80.Pv Electron spectroscopy (X-ray photoelectron (XPS), Auger electron spectroscopy (AES), etc.)
68.35.bd Metals and alloys

Laser cladding with scanning optics: Effect of power adjustment

Joonas Pekkarinen, Veli Kujanpää, and Antti Salminen

J. Laser Appl. 24, 032003 (2012); http://dx.doi.org/10.2351/1.4706582 (7 pages)

Online Publication Date: 01 May 2012

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Laser cladding with fiber laser using scanning optics is a relatively new way of laser cladding. Modern oscillating scanners enable laser power adjustment according to scanning direction. This is a versatile tool for making process more stable as well as modifying the shape of clad bead. Laser cladding was made using 5 kW IPG fiber laser with ILV-oscillating scanner, using 316L powder as clad material and S355 mild steel plate as substrate material. These tests showed that power adjustment is necessary for cladding process stability when sinusoidal scanning is used. Power adjustment can be used also for adjusting the geometry of clad bead and for constructing simple geometries. The oscillating scanner enables flexibility for controlling the geometry of clad bead and process stability compared to the conventional laser cladding with static optics.
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42.62.-b Laser applications

Laser cladding for railway repair and preventative maintenance

Adam Clare, Olusola Oyelola, Janet Folkes, and Peter Farayibi

J. Laser Appl. 24, 032004 (2012); http://dx.doi.org/10.2351/1.4710578 (10 pages)

Online Publication Date: 07 May 2012

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Rolling contact fatigue, amongst other mechanisms of wear, between railway track and train wheel ensures that periodic replacement of worn track and other key components such as switches must be undertaken. The cost associated with repairing/replacing track is significant. This places a financial burden upon the rail network provider, creates a significant carbon footprint associated with remanufacture of track, and also interruption to train services. It is proposed that laser cladding, when deployed strategically, can reduce the costs associated with replacing worn track by enhancing the longevity of new rail components (preservice) and also for the repair of sections of track which are prone to excessive wear (in service). This will lead to a cheaper, more reliable, and sustainable rail network. This paper details a series of investigations undertaken to laser clad with premium wear resistant alloys (nickel alloy, Stellite 6, maraging steel, and hadfield steel) to much cheaper rail material substrates. The methodology for process optimization is presented, and the specimens are characterized for suitability. Laser cladding is demonstrated to be a viable solution to repair worn track, and a deposition process for actual track sections is presented.
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89.40.Bb Land transportation
89.20.Kk Engineering
42.62.Cf Industrial applications
81.65.-b Surface treatments

Contributing factors to fires in clinical settings during medical laser applications

J. Pierce, S. Lacey, R. Lopez, J. Lippert, and J. Franke

J. Laser Appl. 24, 032005 (2012); http://dx.doi.org/10.2351/1.4704850 (10 pages)

Online Publication Date: 10 May 2012

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An estimated 650 fires occur in the surgical environment annually in the U.S.; a figure which may be severely underreported. Any fire in the surgical environment can have devastating implications for patient safety and is clearly an occupational risk to healthcare personnel. Literature searches of the PubMed and Rockwell Laser Industries Laser Accident Databases were performed in order to (1) identify factors and sources affecting the risk of fire in the medical environment, namely, oxidizers, ignition sources, and fuels, and (2) to identify areas of future research for prevention. All papers relevant to the flammability of commonly used medical supplies when subjected to laser radiation, including clinical case reports and publicly available incident data, were identified, reviewed, and summarized. There are numerous materials that are ubiquitous within the medical setting that can ignite when accidentally contacted with laser radiation, including gauze, drapes, sponges, adhesive tapes, and gowns, skin preparatory solutions and ointments, and endotracheal tubes. Future research is warranted to determine the dependence of the ignition potential of the various fuels on laser type and operational parameters. The purpose of this analysis is to summarize and present all of the seminal published literature pertaining to medical laser-related fires and their prevention in order to understand the contributing factors and extent to which these hazards exist, to inform the medical laser community about these hazards, and to prioritize future areas of occupational health and safety research.
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42.62.Be Biological and medical applications
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