Department of Mechanical Engineering, Laboratory for Lasers, MEMS and Nanotechnology, Iowa State University, Ames, Iowa 50011
A review of various laser techniques for microscale processing of SiC for microelectronics and microelectromechanical-system applications is presented. SiC is an excellent material for harsh environments due to its outstanding mechanical, thermal, and chemical properties. However, its extreme thermodynamic stability and inert properties created difficulties in conventional microfabrication methods which provided an opportunity for the exploration of laser processing as an alternative. Many aspects...
JLA Vol:7 Iss:3 (Characterization of chromium bearing surface alloys produced by laser alloying on low carbon steel substrates)
G. L. Goswami
A. L. Pappachan
A. K. Grover
High‐chromium ferritic alloys were produced on mild steel substrates by laser surface alloying. For this, chromium‐plated mild steel samples were treated with a pulsed Nd:YAG laser (300 W maximum power) by varying the average power level from 21.6 W to 30.0 W. The chromium content of the surface alloys was in the range of 3.0–27.0 wt%, with fairly uniform depth of alloying. Microscopy showed very fine austenite needles within elongated/equiaxed ferrite grains in the laser‐alloyed zone (LAZ). X‐ray diffraction indi...
B. V. Anikeev
D. V. Sin'ko
Department of Laser Physics, Volgograd State University, 2‐aya Prodolnay 30, Volgograd 400 062, Russia
A new spectroscopic technique to gain information on the nonlinear constants of optical materials is presented. This technique is made possible due to the point that the application of an external controlled negative feedback (CNF) circuit to an intracavity nonlinear cell results in the generation of extended boundaries of the stability for the laser beam. This effect is analyzed using a semiclassical set of equations that govern laser oscillation. Measurements are made on systems containing either an instantaneous CNF circuit o...
JLA Vol:4 Iss:1 (Combustion‐Assisted Laser Cutting of a Difficult‐to‐Machine Superalloy)
P. A. Molian
In laser cutting, the largest single application of lasers in manufacturing, the assist gas plays an important role in affecting the cutting performance. The assist gas is usually oxygen or an inert gas. In this work a mixture of acetylene and oxygen was employed to create combustion reactions during CO2 laser cutting that enabled an improvement in the cutting speed, and cut quality of a difficult‐to‐machine superalloy. A comparison with laser cutting of a plain carbon steel under identical conditions was also made to determine the usefulness of combustion energy. Results indicate that both cutting speed and qual...
JLA Vol:14 Iss:1 (Physical–computational model to describe the interaction between a laser beam and a powder jet in laser surface processing)
O. O. Diniz Neto
Departamento de Engenharia de Materiais, Instituto Superior Te´cnico, 1049-001 Lisboa, Portugal
Frequently laser surface treatments use a powder jet in conjunction with the laser beam. In this study we present a physical–computational model to describe the interaction between a laser beam and a powder jet. The model can be used to calculate the spatial distribution of particle temperature and laser beam attenuation at any moment and all over the region where the laser and particle beams interact. In calculating particle temperature, the attenuation of the laser beam by the particles themselves is taken into acc...
JLA Vol:18 Iss:2 (Fabrication of titanium microchannels using laser-assisted thermochemical wet etching)
S. W. Son
M. K. Lee
K. H. Oh
S. H. Jeong
Department of Mechatronics, Gwangju Institute of Science and Technology, 1 Oryongdong Bukgu, Gwangju, 500-712 Republic of Korea
A fabrication method of titanium microchannels of an aspect ratio up to 16 and channel width of 10–30 μm is developed using laser-assisted thermochemical wet etching. For the fabrication of deep channel, the workpiece was repeatedly etched over the same path with the control of process parameters. The cross-sectional profile of the microchannel varied between a V shape and a U shape, depending largely upon the laser beam power and etchant concentration. Bubb...
M. T. Wang
Inner Mongolia University, Hohhot 010021, China
A novel localization scheme called laser beam scan localization by combining grid and light (laser) with mobile localization policy for wireless sensor networks is designed. The scheme utilizes a moving location assistant (LA) with a laser beam, through which the deployed area is scanned. The LA sends identities to unknown nodes to obtain the locations of sensor nodes. High localization accuracy can be achieved without the aid of expensive hardware on the sensor nodes, as required by other localization systems...
JLA Vol:23 Iss:4 (Evaluation of the bone repair in defects grafted with hydroxyapatite and collagen membrane combined with laser therapy in rats)
Marcelo Rodrigues da Cunha
Luanda de Abreu Figueira
Joa˜o Paulo Mardegan Issa
Ricardo Alexandre Junqueira Calzzani
Daniele Cristina do Prado Ribeiro
Mariane Silva Pettian
Bone regeneration is the result of cellular events such as osteogenesis and neovascularization. However, implantation of autogenous grafts may be necessary in cases of bone mass loss due to high impact trauma. The disadvantages of the latter approach include morbidity of the donor area. Biomaterials represent an alternative for bone restoration. The most widely used compounds are collagen or hydroxyapat...
D. H. Abbott
C. E. Albright
The most widely used shielding gases for laser welding of steels are helium and argon. Helium produces significantly more penetration than argon in penetration‐mode laser beam welding. Another gas that has been proposed as an alternative to these inert gases is carbon dioxide. The benefits of using carbon dioxide as a shielding gas for laser welding are that it costs less than helium and argon and that it provides nearly the same penetration as helium. The major drawback to its use as a shielding gas for mild steel is that it can cause porosity and other weld discontinuities. In this investigation helium and carbon dioxide were...
Department of Mechanical Engineering, National Cheng Kung University, Tainan 701, Taiwan
The object of this study is to investigate the solidification problem in laser cladding with the wire feeding technique. The solidification phenomenon of laser cladding was analyzed by numerical simulation and experimental visualization. Good agreement has been obtained for 304 stainless steel wires cladding on round tubes and it transpires that there were three basic modes of clad profiles: thinning, thickening, and wavering of the clad thickness at different velocity settings between the feeding wire and the substrate in laser wire cladding. ©...
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