JLA Vol:21 Iss:2 (Laser use vs. handpiece for tooth preparation: A preliminary <em>in vitro</em> study)

Authors:
B. Go¨kc¸e
B. O¨zpinar
C. Artunc¸
G. Aksoy
Department of Prosthodontics, School of Dentistry, Ege University, 35100 Turkey

The key fields of research of dental lasers have focused on the use of different wavelengths on hard and soft tissues; however it is not clear whether they can be used for tooth preparation for full coverage restorations or not. The objective of this study was to investigate the possibility of tooth preparation for full coverage restorations using a scanner assembly added-on Er:YAG laser system and compare the tooth preparation durations performed with dental drills and the laser. The 20 freshly e...

JLA Vol:21 Iss:2 (Partial growth of crack in laser scribing of glass)

Authors:
Koji Yamamoto
Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565–0871, Japan

Noboru Hasaka
Hideki Morita
Mitsuboshi Diamond Industrial Co., Ltd., 1-4-37 Minami-kaneden, Suita, Osaka 564–0044, Japan

Etsuji Ohmura
Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565–0871, Japan

The scribing of glass by a CO₂ laser is much more effective compared to the conventional mechanical technology in use because the strength of the cut glass is improved since microcracks and particles along the cut edge are lessened. However, the crack depth of ...

JLA Vol:21 Iss:2 (Structure and properties of a biomedical Co-Cr-Mo alloy produced by laser powder microdeposition)

Authors:
C. G. Meacock
R. Vilar
Departmento de Materiais, Instituto Superior Tecnico, Avenida Rovisco Pais, Lisboa 1049-001, Portugal

Laser powder microdeposition is a very promising technique to manufacture functional complex-shaped customized medical devices directly from a computer-aided design (CAD) file. It uses a finely focused laser beam to generate a small meltpool on the surface of a metallic substrate into which metallic powder is blown via a fine capillary. The laser/powder interaction zone is scanned over the substrate and molten material re-solidifies, leaving microscale tracks of deposited material. These tracks can be overlapped according to a previously es...

JLA Vol:21 Iss:2 (Thermoelectric currents in laser induced melts pools)

Authors:
Adrian Lange
Andreas Cramer
Eckhard Beyer

Applying an external static magnetic field to laser beam welding may lead to a change in geometry of the weld seam. Since the most common influence of a magnetic field acting on an electrically high conducting fluid is the generation of a Lorentz force, the outcome of such experiments is a strong indication of the presence of electric current in the melt pool. Owing to the static nature of the magnetic field, induction is restricted to the movement of the liquid metal and therefore negligible, leaving thermoelectricity as the sole potential source of current. The present work discloses analytically that the ...

JLA Vol:21 Iss:2 (Visualization of refraction and attenuation of near-infrared laser beam due to laser-induced plume)

Authors:
Yousuke Kawahito
Keisuke Kinoshita
Naoyuki Matsumoto
Seiji Katayama
Joining and Welding Research Institute (JWRI), Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan

This study was performed to obtain a fundamental knowledge of the interaction between a near-infrared laser beam and an induced plume during welding. The plume was characterized by spectroscopy, and the effect and mechanism of the laser-induced plume on the refraction and/or attenuation were investigated by high-speed video observation of the plume and the probe laser, and power meter measurement of the fiber probe laser beam of 1090 nm wavelength which pa...

JLA Vol:21 Iss:3 (Assessment of external root temperature during root canal irradiation by Nd:YAG and Er:YAG lasers)

Authors:
Daphne Caˆmara Barcellos
Department of Restorative Dentistry, Sa˜o Jose´ dos Campos School of Dentistry, Sa˜o Paulo State University, SP, Brazil

Cla´udio Antonio Talge Carvalho
Department of Restorative Dentistry, Endodontics Course, Sa˜o Jose´ dos Campos School of Dentistry, Sa˜o Paulo State University, SP, Brazil

Carlos Rocha Gomes Torres
Ce´sar Roge´rio Pucci
Claudia Roberta Santos Azuma
Eduardo Nunes Pugliesi
Department of Restorative Dentistry, Sa˜o Jose´ dos Campos School of Dentistry, Sa˜o Paulo State University, SP, Brazil
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JLA Vol:21 Iss:3 (Inert gas cutting of thick-section stainless steel and medium-section aluminum using a high power fiber laser)

Authors:
Catherine Wandera
Department of Mechanical Engineering, Lappeenranta University of Technology, Tuotantokatu 2, Lappeenranta FIN-53850, Finland

Antti Salminen
Department of Mechanical Engineering, Lappeenranta University of Technology, Tuotantokatu 2, Lappeenranta FIN-53850, Finland and Machine Technology Centre Turku Ltd., Lemminka¨isenkatu 28, Turku FIN-20520, Finland

Veli Kujanpaa
Department of Mechanical Engineering, Lappeenranta University of Technology, Tuotantokatu 2, Lappeenranta FIN-53850, Finland and VTT The Technical Research Centre of Finland, Tuotantokatu 2, Lappeenranta, FI-53850, Finland

Inert gas assisted laser cu...

JLA Vol:21 Iss:3 (Infrared observations and finite element modeling of a laser transmission welding process)

Authors:
L. S. Mayboudi
A. M. Birk
G. Zak
Mechanical and Materials Engineering, Queen’s University, Kingston, Ontario K7L 3N6, Canada

P. J. Bates
Chemistry and Chemical Engineering, Royal Military College, Kingston, Ontario K7K 7B4, Canada

Laser transmission welding (LTW), a technique to join thermoplastic components, involves a laser beam passing through a laser-transmitting part and then being absorbed by the laser-absorbing part at the weld interface. To form a strong bond, it is important that the weld interface be exposed to sufficient heat to melt the polymer without degrading it. A lap-joint geometry was investigated and the...

JLA Vol:21 Iss:3 (Laser sintering effects on the physical properties and structure of 0.94(K_0.5Na_0.5)NbO₃-0.06LiTaO₃ lead-free piezoelectric ceramics)

Authors:
Lingfei Ji
Yijian Jiang
Yi Gao
Xinyu Du
Institute of Laser Engineering, Beijing University of Technology, Beijing 100022, People’s Republic of China

Taking laser as the heat source for ceramic sintering, 0.94K_0.5Na_0.5NbO₃-0.06LiTaO₃ ceramics with unique physical properties were prepared. Fine ferroelectric properties with remnant polarization of 18 μC/cm² and coercive field of 18.8 kV/cm were obtained. The piezoelectric properties and density of the ceramics were d₃₃∼120 pC/N, k_p∼36.6%, T_C∼420 °C, and ρ∼4.125...

JLA Vol:21 Iss:3 (Laser welding of galvanized DP980 steel assisted by the GTAW preheating in a gap-free lap joint configuration)

Authors:
Shanglu Yang
Radovan Kovacevic
Center for Advanced Manufacturing, Southern Methodist University, Dallas, Texas, USA 75205

With the increasing need for reducing the vehicle’s weight, improving fuel efficiency and safety, as well as the corrosion resistance, more and more galvanized high-strength steels have been used in the automotive industry. However, the successful laser welding of galvanized steels in gap-free lap joint configuration is still a big challenge. The high-pressurized zinc vapor is readily developed at the interface of the two metal sheets due to the lower boiling point of zinc (around 906 °C) than the melting point of steel (over 13...