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)

Authors:
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...

JLA Vol:25 Iss:5 (Numerical and experimental study of the effect of groove on plasma plume during high power laser welding)

Authors:
Cai Yan
Xie Wen-Jing
Wu Yue
Sun Da-Wei
Wu Yixiong
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 ...

JLA Vol:24 Iss:4 (Femtosecond laser-induced periodic surface structures)

Authors:
J. Bonse
J. Kru¨ger
S. Ho¨hm
A. Rosenfeld
Array

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...

JLA Vol:5 Iss:1 (Single Pass Laser Cutting of Polymers)

Authors:
R. Patel
G. Baisch
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 ...

JLA Vol:17 Iss:2 (Modeling of laser deposition and repair process)

Authors:
Lijun Han
Kaushik M. Phatak
F. W. Liou
Department of Mechanical and Aerospace Engineering, University of Missouri-Rolla, Rolla, Missouri 65409-1350

Laser aided deposition is a material additive based manufacturing process via metallurgically bonding the deposited material to the substrate. Due to its capability to bond various materials together, it becomes an attractive technology for part repair in small scale. However, the details of the process remain an active area for research because of the complicated interactions involved. In this study, a mathematical model was established to investigate thermal and mass transportation phenomena, which incl...

JLA Vol:21 Iss:4 (How the laser started)

Authors:
Charles Townes
Department of Physics, University of California, Berkeley, California 94720

JLA Vol:7 Iss:1 (Development of laser finishing for non‐circular profiles)

Authors:
Ko‐Wang Liu
Paul S. Sheng
Department of Mechanical Engineering, University of California, Berkeley, CA 94720‐1740, U.S.A.

A laser‐based technique for finishing of non‐circular cylindrical parts is presented. In this process, the frequency characteristics of a desired non‐circular shape is extracted from a CAD through a Fast Fourier Transform algorithm and implemented through a CO₂ laser machining system. A galvanometer‐based scanner is used in the process to achieve programmable beam trajectories and high‐speed finishing. An error estimation scheme can be developed to determine the final dimensional erro...

JLA Vol:15 Iss:3 (Steady-state laser cutting modeling)

Authors:
Ce´dric Mas
Re´my Fabbro
CLFA, 16 bis Avenue Prieur de la Côte d’Or, 94114 Arcueil Cedex, France

Yannick Goue´dard
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)

Authors:
F. Quintero
J. Pou
F. Lusquin˜os
A. Riveiro
M. Pe´rez-Amor
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...

JLA Vol:9 Iss:3 (Experimental study of cutting thick aluminum and steel with a chemical oxygen–iodine laser using an N₂ or O₂ gas assist)

Authors:
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...