JLA Vol:8 Iss:4 (Some aspects of laser heating of engineering materials)

Authors:
B. S. Yilbas
A. Z. Al‐Garni
Mechanical Eng. Dept., KFUPM, P.O. Box 1913, Dhahran, Saudi Arabia

Laser induced heating processes are important when a laser is used as a machine tool in industry, since the quality of the machining process strongly depends on the heating mechanism. The present study examines a heat transfer model that provides useful information on the laser induced interaction mechanism. Steady state and time dependent heating models are introduced and temperature profiles inside the materials are predicted. Using appropriate assumptions, the time for the surface temperature to reach 90% of its steady state value is estimated. To valid...

JLA Vol:8 Iss:4 (The role of oxygen pressure in laser cutting mild steels)

Authors:
A. Ivarson
J. Powell
C. Magnusson

This paper presents the results of an experimental program investigating the effects of using high pressure oxygen as assist gas in combination with a pulsed laser while cutting medium thick mild steel plates. It was discovered that if the pulse conditions are optimized, the maximum cutting speed for a set average laser power could be increased by up to 10% compared to low oxygen pressure continuous wave (CW) laser cutting. The assist gas was found to have two optimum pressure ranges between which the material suffered from burning on the cut edge. The paper presents a phenomenological model to explain the ch...

JLA Vol:8 Iss:5 (A guide to developing a laser standard operating procedure)

Authors:
Ken Barat
Lawrence Berkeley National Laboratory, Berkeley, CA 94720, U.S.A.

The ANSI Z 136.1 standard requires a standard operating procedure (SOP), however, it does not recommend or suggest a format for the SOP. The goal of this article is to outline, explain and suggest an SOP format that could be applied by a laser safety officer to a varied number of situations and laser uses.

JLA Vol:8 Iss:5 (Diode‐pumped Nd:YAG laser for precision laser machining)

Authors:
Jason Machan
Marcy Valley
Gerry Holleman
Marc Mitchell
Dave Burchman
Jim Zamel
George Harpole
Hagop Injeyan
Len Marabella
TRW R1/1184, One Space Park, Redondo Beach, CA 90278, U.S.A.

Results are presented on a high power, diode‐pumped, pulsed Nd:YAG laser for precision laser machining. The laser is an unstable resonator with a graded reflectivity outcoupler, generating a beam with excellent beam quality. The gain medium is a single zig‐zag slab, pumped symmetrically by diode arrays. The use of diode arrays minimizes the thermal loading on the slab, and the zig...

JLA Vol:8 Iss:5 (Excimer laser interactions with an aluminum alloy)

Authors:
Angelos Koutsomichalis
Anastasia Kefalidou
Laboratory of Physical Metallurgy, National Technical University of Athens, Zografou Campus 15773 Athens, Greece

An AlCuMg alloy was irradiated using a KrF pulsed excimer laser. A microstructural study showed the presence of a laser treated zone having a uniform depth of approximately 20 μm. The surface layer of the laser treated aluminum alloy exhibited a wavy topography and its surface roughness was found to depend on the number of laser pulses per step. A X‐ray diffraction analysis revealed the presence of aluminum oxides and nitrides on the surface of the laser irradiated specimens. Corrosion measurements s...

JLA Vol:8 Iss:5 (Filtration of the fumes generated by industrial CO₂ laser cutting)

Authors:
J. Powell
H. Haferkamp
F. W. Bach
D. Seebaum
A. Hampe

This paper reviews the subject of fume filtration in the context of industrial laser cutting. Self‐cleaning or surface filtration can be used to good effect when cutting metals. The clean exhaust air from such a filter can be recycled into the workplace with an obvious saving on heating bills. Fumes generated during non‐metal cutting are a great deal more difficult to filter and recycling of the air is not possible.

JLA Vol:8 Iss:5 (Laser drilling of advanced materials: Effects of peak power, pulse format, and wavelength)

Authors:
X. Chen
W. T. Lotshaw
A. L. Ortiz
P. R. Staver
C. E. Erikson
M. H. McLaughlin
T. J. Rockstroh

The quality of laser‐drilled holes is significantly influenced by the laser peak power, pulse format, and wavelength. Three advanced materials are used to demonstrate the importance of choosing the correct laser parameters for a specific material. The materials are: (1) intermetallic single crystal nickel aluminide (NiAl) alloy; (2) N5, a single crystal nickel‐based superalloy; and (3) a silicon carbide (SiC) ceramic matrix composite (CMC). The laser peak power is varied in terms of the pulse...

JLA Vol:8 Iss:5 (Taking advantage of laser properties to enhance demonstrations and student laboratories)

Authors:
Michele L. Brill
Camden County College — Physics/Lasers, Box 200, Blackwood, NJ 08012, U.S.A.

This paper reflects the proceedings of a workshop for local educators provided by Camden County College Laser Curriculum faculty which addressed the question: ‘How can the teacher take advantage of laser properties to improve or enhance demonstrations and student labs?’ Explored here are illustrative ways in which to utilize, for educational purposes, the three well‐known characteristics of lasers: directionality, monochromaticity, and coherence. There is a faculty overlap between the Physics Department and the Laser Curriculum faculty at the college. The use...

JLA Vol:8 Iss:5 (William B. Mark Memorial Lecture)

Authors:
Kenneth A. Arndt
Department of Dermatology, Beth Israel Hospital, 330 Brookline Ave., Boston, MA 02215, U.S.A.

JLA Vol:8 Iss:6 (A modeling study on the influence of pulse shaping on keyhole laser welding)

Authors:
P. S. Mohanty
A. Kar
J. Mazumder

A theoretical analysis describing the effects of pulse shaping on keyhole laser welding is presented. Calculation of the keyhole profile and melt pool dimensions was performed by the balancing of surface forces and energy at the liquid‐vapor and solid‐liquid interfaces in three dimensions. The effect of temporal pulse shape on weld dimensions has been examined over a range of power densities, pulse times and pulse frequencies. Several pulse types (e.g., top‐hat, Gaussian, ramp‐up and ramp‐down pulses) have been considered. Pulse shaping showed significant effect on the weld dimensio...