E. A. Metzbower
US Naval Research Laboratory, Code 6320, Washington, DC 20375‐5000, U.S.A.
A thermodynamically based model has been developed to calculate the size and temperature of the ‘keyhole’ through the thickness of the weldment. The model is based on calculating the power loss resulting from evaporation of an element in the chemistry of the plate and a minimum power density required to produce a keyhole. The evaporative power loss is set equal to the Gaussian power density, which is used to represent the laser beam. The result is a temperature distribution across the keyhole. Absorption of the laser power in the keyhole is calculated based on inverse...
J. L. Sun
W. M. Steen
K. G. Watkins
W. P. Brown
Direct laser cladding of Al alloy on mild steel produces continuous brittle intermetallic FexAly layers at the interface resulting in weak bonding of the clad and the substrate. To overcome this problem, both Ni and Al were investigated as intermediate coatings. Although a Ni coating with a thickness of 70 μm was successful in eliminating the formation of continuous Al‐Fe intermetallics, the bonding at the Al alloy/Ni interface was not strong enough to survive a bending test. A pure Al coating was found to be a better ...
JLA Vol:9 Iss:1 (Continuous wave Nd:YAG laser cladding modeling: A physical study of track creation during low power processing)
D. F. Grevey
A. B. Vannes
This paper concerns the modeling of cladding using an Nd:YAG laser operating at low powers typically less than 800 W. Experimental observation of the evolution of the mass of the clads shows two power thresholds. The theoretical study relies on a calculation of the fluence provided to the substrate and on a model of heat transfer into the substrate. We suggest that the first threshold is the power required for substrate melting. The second power is the threshold when the powder is directly melted by the beam and is therefore a liquid when contacting the substrate.
JLA Vol:9 Iss:1 (The development of a laser machining curriculum: An interdisciplinary approach (the MAST program))
Gary J. Masciadrelli
Nicholas M. Massa
The development of an industry‐driven interdisciplinary curriculum in laser machining is presented. The Machine tool Advance Skills Technology (MAST) program is a US Department of Education grant to develop and demonstrate a national training model for new technologies and manufacturing processes in precision manufacturing. Springfield Technical Community College (STCC) in partnership with six other community colleges nationwide, developed, tested, and disseminated industry‐specific skills standards and model curricula in laser machining and related technologies for the United States machine tool industry. STC...
JLA Vol:9 Iss:1 (Laser generated air contaminants released during laser cutting of fabrics and polymers)
C. Eugene Moss
National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Cincinnati, OH 45226, U.S.A.
Environmental monitoring was conducted at an industrial facility to qualitatively identify the major contaminants generated while cutting fabrics and polymers with a 25 W CO2 continuous beam laser. Carbon monoxide, hydrogen cyanide, and particulates were also assessed, and a bulk sample of residue from the laser exhaust duct was analyzed for inorganic acids, pH, and volatile organic compounds. Samples were collected while cutting vinyl, acrylics, woven fabrics, felt, Formica®, and Plexiglass®....
Department of Mechanical Engineering, University of California, Berkeley, CA, U.S.A.
This paper presents an approach for kinematic compensation of the laser shaping process which is capable of achieving improved dimensional accuracy for non‐circular profiles. In this approach, a plug‐in repetitive controller is added into the existing position servo loop to improve tracking of the desired sinusoidal trajectory and subsequently reduce tracking errors. The effect of tracking errors on different dimensional error modes in the non‐circular shaping process is identified. Simulation models are developed for testing the performance o...
D. A. Scott
S. B. Emms
J. M. Yellup
A new laser cladding technique for producing wear and corrosion resistant surfaces on engineering components is reported. The technique involves the combination of the pre‐placed and injected powder delivery methods for producing clad layers. The clad layers were formed with a pulsed Nd:YAG laser and optical fibers. The results using a nickel‐based alloy (Hastelloy C) indicate that uniform clad layers in excess of 1 mm in thickness can be achieved in a single pass with 240 W average power incident on the workpiece. The laser beam was delivered through a step‐index glass ...
The acoustic emissions from laser lap welds in stainless steel sheet were recorded and analyzed. The acoustic signals emanating from the weld were sensed with an instrument microphone and analyzed using short‐time Fourier spectra to characterize their time‐frequency distributions. It was determined that the acoustic spectrum of good‐quality, full‐penetration welds could be differentiated from the spectra of poor‐quality welds, defined as either partial‐penetration welds or welds having a gap between the sheets being joined. A novel, relatively simple class...
JLA Vol:8 Iss:1 (Recent progress in laser surface treatment: <emph type="4">I</emph>. Implications of laser wavelength)
Institute fu¨r Strahlwerkzeuge, Universita¨t Stuttgart, Pfaffenwaldring 43, 70569 Stuttgart, Germany
The coupling mechanisms of laser radiation and the mechanisms of heat transport in the workpiece are considered. Starting from the well‐known basics of Fresnel absorption — valid only for smooth and clean surfaces — further effects of coupling are examined. Studies on the effects of surface modifications inherent to all industrial parts and process conditions are presented. The more appropriate term coupling rate is introduced: This describes the r...
JLA Vol:8 Iss:1 (Comparison of aluminum alloy welding characteristics with 1 kW CO and CO<sub>2</sub> lasers)
Bu¨lent A. Mehmetli
Institute of Research and Innovation, Laser Laboratory 1201 Takada, Kashiwa‐shi, Chiba 277, Japan
Welding characteristics of various aluminum alloys (A1100, A2017, A5083, A6063, A7N01) are investigated with CW CO and CO2 lasers near 1 kW power level. The beam characteristics of both lasers at the welding point are similar, so that a comparison can be made of the effect of the wavelength difference. The welding characteristics are assessed by measuring the size of the weld bead. It is found that the threshold power between heat‐conduction and deep‐penetration typ...
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