JLA Vol:25 Iss:5 (Numerical and experimental study of the effect of groove on plasma plume during high power laser welding)
Shanghai Jiao Tong University, Dongchuan Road 800, Shanghai 200240, China and Shanghai Key Laboratory of Materials Laser Processing and Modification, Shanghai 200240, China
The influence of groove on the static feature and dynamic behavior of plasma plume during high power CO2 laser welding process was studied using a hydrodynamic three-dimensional model and corresponding experiments. The temperature, composition, and velocity of plasma plume along the incident path of laser beam were computed. The static morphology of plasma plume was analyzed through both models ...
The formation of laser-induced periodic surface structures (LIPSS) in different materials (metals, semiconductors, and dielectrics) upon irradiation with linearly polarized fs-laser pulses (τ ∼ 30–150 fs, λ ∼ 800 nm) in air environment is studied experimentally and theoretically. In metals, predominantly low-spatial-frequency-LIPSS with periods close to the laser wavelength λ are observed perpendicular to the polarization. Under specific irradiation conditions, high-spatial-frequency-LIPSS with sub-100-nm spatial periods (∼λ/10) can be gene...
IBM Corporation, GTD, Hopewell Junction, New York
Since the early 1980's discovery of the ability of excimer lasers to etch polymers precisely and cleanly with minimal thermal damage, excimer lasers have been used actively in the semiconductor industry for various manufacturing processes. In the present study a process for laser cutting of polymers has been investigated. A laser beam of controlled cross‐sectional shape is imaged onto a polymer surface. The geometry of the cutting path is controlled by precise movement of a sample mounted on a 2‐axis computer controlled work stage. This type of a process is useful for applications ...
Wesley J. Marshall
U.S. Army Center for Health Promotion and Preventive Medicine, Aberdeen Proving Ground, Maryland 21010-5403
Although hazard classification is performed at predefined distances, the maximum permissible exposure (MPE) for extended-source diode lasers decreases as the distance from the laser increases. The MPE depends on the apparent angular subtense of the source, which is simply the magnified image of the emitting diode. Small diameter beams require special consideration.
JLA Vol:18 Iss:4 (Cutaneous sensation threshold for 3.8 μm radiation from a short duration pulsed laser on the calves of human subjects: A pilot study)
Thomas E. Johnson
Michael J. Roy
Department of Environmental and Radiological Health Sciences, Colorado State University, 1618 Campus Delivery, Fort Collins, Colorado 80528 and Department of Medicine, School of Medicine, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, Maryland 20814
The objective of this study was to determine the threshold for sensing a 3.8 μm laser on the skin. The identification of the skin sensation threshold for invisible lasers is useful in providing scientific guidance to the safety community regarding accidental skin exposures. Knowledge of the level of sensation of lasers might be used to s...
R. E. Mueller
W. W. Duley
CRESS and Laser Processing Laboratory, York University, Toronto, Ontario, Canada M3J 1P3
Canadian Astronaut Office, National Research Council, Ottawa, Ontario, Canada K1A 0R6
W. F. J. Evans
Atmospheric Environment Service, 4905 Dufferin Street, Downsview, Ontario M3H 5T4
Initial results of a series of laser processing experiments performed under the micro‐gravity conditions supplied by NASA's KC‐135 aircraft are presented. Weld morphologies of polypropylene and polyethylene were obtained under both hyper‐ and hy...
JLA Vol:9 Iss:3 (Experimental study of cutting thick aluminum and steel with a chemical oxygen–iodine laser using an N<sub>2</sub> or O<sub>2</sub> gas assist)
David L. Carroll
James A. Rothenflue
A chemical oxygen–iodine laser (COIL) was used to cut aluminum and carbon steel. Cut depths of 20 mm in aluminum and 41 mm in carbon steel were obtained using an N2 gas assist and 5–6 kW of power on target. The same laser at the same power level produced a cut depth of 65 mm in carbon steel with an O2 gas assist; a low quality cut to a depth of nearly 100 mm in carbon steel was also demonstrated. These data are compared with existing COIL and CO2 laser cutting data. COIL cuts carbon steel and stainless steel at approximately the same rate. For a given cut depth, power and spot size...
Milind M. Rajadhyaksha
Warren H. Stevenson
Applied Optics Laboratory, School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907, U.S.A.
This paper presents the results of a detailed analytical and experimental investigation into the accuracy of a differential laser Doppler velocimeter (LDV) for dynamic, solid surface velocity measurements made over very short averaging times on the order of one millisecond. Accuracy limitations are derived, along with operating conditions and signal processing considerations needed to optimize LDV performance. An experiment is described which demonstrates the use of an LDV to instantaneously and accurate...
CLFA, 16 bis Avenue Prieur de la Côte d’Or, 94114 Arcueil Cedex, France
OPTIS, ZE la Farlède, BP 275, 83078 Toulon Cedex 9, France
We present a global self-consistent model of the laser cutting process where we have taken into account the main parameters of the process that are the laser beam intensity distribution, the thermal phenomena controlling the melt parameters, the fluid, both cutting gas and melt hydrodynamics, and the local equilibrium of the geometry of the cutting front. This steady state approach provides us with different fluid velocities, surface ...
JLA Vol:19 Iss:3 (Single-Pass and Multi-Pass Laser Cutting of Si–SiC: Assessment of the Cut Quality and Microstructure in the Heat Affected Zone)
Departamento Fi´sica Aplicada, E.T.S. Ingenieros Industriales, University de Vigo, 36310 Vigo, Spain
A. J. S. Fernandes
Department of Physics, University of Aveiro, 3810-193 Aveiro, Portugal
Experimental investigations on the laser cutting of thick silicon infiltrated silicon carbide (Si–SiC) elements are presented. Si–SiC is a fully dense ceramic composite with high hardness and chemical and thermal stability, which makes it a valuable material in severe conditions. However, machining is still a challenging task. A...
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