JLA Vol:14 Iss:1 (Physical–computational model to describe the interaction between a laser beam and a powder jet in laser surface processing)

Authors:
O. O. Diniz Neto
Array

R. Vilar
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:14 Iss:2 (An investigation of rapid prototyping of sand casting molds by selective laser sintering)

Authors:
G. Casalino
L. A. C. De Filippis
A. D. Ludovico
L. Tricarico
Dipartimento di Ingegneria Meccanica e Gestionale, Politecnico di Bari, 70126 Bari, Italy

Among the layer fabrication techniques, selective laser sintering (SLS), is widely used for manufacturing various products made of different materials (i.e., polycarbonates, nylons, polyamides, sand casting, metal powders, and others). The SLS of precoated foundry sands allows the aggregation of adjacent particles, which are then cemented by furnace heat treatment. Moreover, geometrically complex molds and cores not obtainable with conventional methods can be realized by this method. In th...

JLA Vol:14 Iss:2 (Application of 7 kW class high power yttrium–aluminum–garnet laser welding to stainless steel tanks)

Authors:
Yoshiaki Shimokusu
Kobe Shipyard & Machinery Works, Mitsubishi Heavy Industries Ltd., 1-1-1 Wadasaki-cho, Hyogo-ku, Kobe Hyogo 652-8585, Japan

Seiji Fukumoto
Kobe Shipyard & Machinery Works, Mitsubishi Heavy Industries Ltd., 1-1-1 Wadasaki-cho, Hyogo-ku, Kobe Hyogo 652-8585, Japan

Michisuke Nayama
Technology Planning Department, Technical Headquarters, Mitsubishi Heavy Industries Ltd., 3-3-1 Minatomirai, Nishi-ku, Yokohama Kanagawa 220-8401, Japan

Takashi Ishide
Takasago R&D Center, Mitsubishi Heavy Industries Ltd., 2-2-1 Shinhama, Arai-cho, Takasago Hyogo 676-8686, Japan

Shuho Tsubota
Takasago...

JLA Vol:14 Iss:2 (Deformation behavior and microstructural changes of a hardened high carbon alloy steel in laser bending)

Authors:
K. C. Chan
J. Liang
Department of Manufacturing Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong

In this article, the deformation behavior and microstructure of a hardened high carbon steel in laser bending were examined. A CO₂ laser unit (TEM₀₀) was used to bend the samples at different laser powers, scanning velocities, and number of scans. A relatively linear relationship between bending angle and number of scans was obtained at laser powers of 150 and 200 W and at a scanning velocity of 30 mm/s. A threshold heat input of about 3.25 J/mm was observed, below which bending was unlikely to occur. The bending angle was al...

JLA Vol:14 Iss:2 (Development of simulated pigmented lesions in an optical skin-tissue phantom: Experimental measurements in the visible and near infrared)

Authors:
Manuela Lualdi
Ambrogio Colombo
Alberto Mari
Stefano Tomatis
Renato Marchesini
Medical Physics Unit, Istituto Nazionale per lo Studio e la Cura dei Tumori, Milan, Italy

Realistic, pigmented skin simulants (“phantoms”) can be useful in optimizing dermal laser procedures and for laser surgical training. Diffuse reflectance of skin pigmented lesions depends on the amount and distribution of the absorbing/diffusing chromophores, mainly hemoglobin and melanin, embedded in the skin layers. The reason why diffuse reflectance of benign melanocytic lesions is different from that of melanoma is still unclear. In an attempt...

JLA Vol:14 Iss:2 (Energy redistribution during CO₂ laser cladding)

Authors:
H. Gedda
Luleå University of Technology, Division of System and Manufacturing Engineering, S-971 87 Luleå, Sweden

J. Powell
Laser Expertise Ltd., Acorn Park Industrial Estate, Harrimans Lane, Nottingham NG7 2TR, United Kingdom

G. Wahlstro¨m
Duroc AB, Industriva¨gen 8, S-90130 Umeå, Sweden

W.-B. Li
H. Engstro¨m
C. Magnusson
Luleå University of Technology, Division of System and Manufacturing Engineering, S-971 87 Luleå, Sweden

This article examines the factors that effect the efficiency of the CO₂-laser powder cladding process. By the...

JLA Vol:14 Iss:2 (Human behavioral factors in laser safety)

Authors:
Rick Mannix
Environmental Health & Safety Office, University of California, Irvine, California 92697-2725

While training, engineering controls, warning signs/systems, and protective eyewear are emphasized in laser safety programs, laser-related accidents do occur in facilities without obvious deficiencies in those areas. Problems still occur because of insufficient attention to administrative safety issues directly related to human nature and behavioral factors. Common safety problems associated with behavioral factors are discussed. Personal experiences of the author, including lessons learned, are included. The issues are discussed within the context of laser safety, bu...

JLA Vol:14 Iss:2 (Influence of oxide film on weld characteristics of mild steel in CO₂ laser welding)

Authors:
Kazuhiko Ono
Kaoru Adachi
Manufacturing Engineering Development Center, Komatsu Ltd., Hirakata, Osaka 573-1011, Japan

Isamu Miyamoto
Takashi Inoue
Department of Manufacturing Science, Osaka University, Suita, Osaka 565-0871, Japan

The influence of oxide film, such as laser cutting edge or mill scale, on CO₂ laser welding phenomena and weld characteristics of mild steel was investigated. Laser welding of butt joints, which were different in location and thickness of oxide film, were performed. Examinations were made on the weld characteristics which were: bead geometry, defect, and microstructure. Light emitted from la...

JLA Vol:14 Iss:2 (Monitoring of laser weld penetration using sensor fusion)

Authors:
Allen Sun
Elijah Kannatey-Asibu
Department of Mechanical Engineering, The University of Michigan, Ann Arbor, Michigan 48109

Mark Gartner
Ford Motor Company, Dearborn, Michigan 48121

Depth of penetration is a critical parameter in laser welding. In many applications, full penetration is desired, but difficult to detect in real time. A sensor fusion system using infrared, ultraviolet, audible sound, and acoustic emission has been implemented for real time monitoring of CO₂ laser lap welds in both laboratory and industrial production settings. Signals from the welds were analyzed by: (1) singular value decomposition with data fusion,...

JLA Vol:14 Iss:2 (On the mechanisms of wetting characteristics modification for selected metallic materials by means of high power diode laser radiation)

Authors:
J. Lawrence
L. Li
Department of Mechanical Engineering, Laser Processing Research Centre, Manufacturing Division, University of Manchester Institute of Science and Technology (UMIST), Manchester M60 1QD, United Kingdom

This work elucidates and analyzes the factors responsible for modifications to the wettability characteristics of metallic materials after high power diode laser (HPDL) treatment. It was found that interaction of EN3 and EN8 mild steel with HPDL radiation resulted in the wettability characteristics of the mild steels altering to various degrees depending upon the laser processing parameters. Such changes in the wettability characteristics of the mi...