JLA Vol:20 Iss:2 (Laser bioeffects associated with ultrafast lasers: Role of multiphoton absorption)

Authors:
Randolph D. Glickman
Department of Ophthalmology, University of Texas Health Science Center, San Antonio, Texas 78229-3900

Thomas E. Johnson
Department of Environmental and Radiological Health Sciences, Colorado State University, Ft. Collins, Colorado 80523

Gary D. Noojin
David J. Stolarski
Michael L. Denton
Northrup Grumman Warfighter and Applications Department, San Antonio, Texas 78228-1330

Neeru Kumar
Department of Ophthalmology, University of Texas Health Science Center, San Antonio, Texas 78229-3900

Benjamin A. Rockwell
US Air Force Research Laboratory, AFRL/HEDO, Brooks City...

JLA Vol:1 Iss:4 (Recent Developments in Laser Melt/Particle Injection Processing)

Authors:
K. P. Cooper
Geo‐Centers, Inc., 10903 Indian Head Highway, Fort Washington, Maryland 20744

P. Slebodnick
Naval Research Laboratory, Washington, D.C. 20375.

Investigations into crack formation in particle injected surfaces and into microstructural evolution during cladding were some of the recent developments in laser melt/particle injection processing. Both surface modification techniques involved blowing powder particles into a melt pool formed by a laser beam. When the particulate materials were metal carbides composite surface layers were formed and the thermal stresses that developed during cooling of the carbide injected layer resulted in th...

JLA Vol:1 Iss:2 (A Study in Surface Alloying of Titanium Alloys)

Authors:
A. Bharti
R. Sivakumar
Defence Metallurgical Research Laboratory, Kanchanbagh, Hyderabad‐500 258, India

D. B. Goel
Department of Metallurgical Engineering, University of Roorkee, Roorkee‐247 667, India

A 5 KW CW CO₂ laser has been used to alloy the surface of Ti6Al4V alloy with carbon. As a result the average microhardness was increased from 365 to 600 kg/mm.² Compositional inhomogeneity was observed on the alloyed surface, however the compositional inhomogeneity index reduced considerably by cross scanning with defocused laser beam. Surface roughness of the alloyed surface was also studied and the roughn...

JLA Vol:23 Iss:1 (Picosecond laser-induced color centers in glass optics)

Authors:
David Ashkenasi
Andreas Lemke
Applied Laser Technology, Laser- and Medical-Technology Berlin (LMTB) GmbH, Fabeckstr. 60-62, 14195 Berlin, Germany

It is known that ionizing radiation (x ray, gamma rays, and electrons) can induce numerous changes in the physical properties of glasses. The most obvious effect is visible coloration, which is caused by the accumulation of color centers (defects) in the irradiated volume. The application of such induced color centers has prompted a renewed interest since they can be generated and bleached reversibly. We present results on laser-induced color centers in different types of glasses using picosecond laser pulses. By applyi...

JLA Vol:16 Iss:4 (Laser transmission welding of polymer and wood composites: Material and joint mechanism related studies)

Authors:
H. Haferkamp
A. von Busse
S. Barcikowski
A. Ostendorf
J. Bunte
Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover, Germany

Laser beam transmission welding is an innovative and promising technology for many industries such as the automotive, electronic, and medical industry. Extension to application of this technology to wood components makes it also interesting for the woodworking and furniture industry. Therefore, several investigations in the field of welding of fiber reinforced thermoplastic and wood composites with polymers have been carried out. Focus is given to the determination of the weldability and weld ...

JLA Vol:7 Iss:3 (Study of liquid and vapor ejection processes during laser drilling of metals)

Authors:
Bekir S. Yilbas¸
Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia

In an experimental investigation of laser–metal interaction, one of the important parameters is the propagation velocity of the liquid–vapor interface. The quantity appears as a direct result of the theoretical examination of the interaction and may be used to test the accuracy of the theory. Consequently, in the present study, the nature of the interaction mechanism between a pulsed laser beam and metals is examined using streak photographs of the ejecta from four metals: titanium, tantalum, nickel, and EN58B stainless steel. It...

JLA Vol:21 Iss:1 (Visualization of events inside kerfs during laser cutting of fusible metal)

Authors:
Peter Yudin
Oleg Kovalev
Khristianovich Institute of Theoretical and Applied Mechanics, Novosibirsk, 630090, Russia

The subject of the research is mechanism of melt removal and striated roughness generation. Being the main obstacle limiting laser cutting process performance, these phenomena are widely discussed. Available theoretical descriptions are not conclusive, as they have nothing to be verified with. High temperatures and narrowness of the kerf severely limit visual access at a real facility. Observation will become possible if one wall of the kerf is made of glass. This possibility is utilized in present experiments, which reproduce the process at low tem...

JLA Vol:15 Iss:1 (Dual laser beam modification of high alumina ceramics)

Authors:
D. Triantafyllidis
Array

J. R. Bernstein
Corrosion and Protection Centre, University of Manchester Institute of Science and Technology, Manchester M60 1QD, United Kingdom

L. Li
Department of Mechanical, Aerospace and Manufacturing Engineering, University of Manchester Institute of Science and Technology, Manchester M60 1QD, United Kingdom

F. H. Stott
Corrosion and Protection Centre, University of Manchester Institute of Science and Technology, Manchester M60 1QD, United Kingdom

Alumina-based refractory materials are extensively used in high-temperature applications, such as linings in waste incinerators. A sign...

JLA Vol:9 Iss:6 (Effect of nozzle orientation on the gas dynamics of inert-gas laser cutting of mild steel)

Authors:
Aaron D. Brandt
Gary S. Settles
Gas Dynamics Laboratory, Mechanical Engineering Department, Penn State University, University Park, PA 16802, U.S.A.

This investigation applies sonic and supersonic coaxial and off‐axis nozzles to the cutting of mild steel sheet of 1–4 mm thickness. A 1.5 kW CW CO₂ laser is used with nitrogen as the assist gas. Sonic coaxial cutting is compared to that of off‐axis nozzles, which vary in orientation from 20–60° behind the laser axis and in exit Mach number from 1 to 2.4. Results show a 50% increase in maximum cutting speed at approximately a 40° off‐axis nozzle angle. In com...

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, Germany

Densely 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...