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...
H. W. Bergmann
Forschungsverbund Lasertechnologie Erlangen (FLE), Martensstr. 5, 8520 Erlangen, West Germany
Aluminum alloys are used extensively in aerospace structures because of their high strength‐to‐weight characteristics. Unfortunately, these alloys are difficult to cut by laser processing. This behavior stems from: 1) their affinity for atmospheric gases, 2) their tendency to form high melting point reaction products and 3) the marked difference between their solidus and liquidus temperatures, which leads to formation of a mushy zone during cutting. This paper describes the results of a program directed t...
JLA Vol:14 Iss:3 (Effects of laser welding parameters on magnetic materials with the aid of a mechatronic measuring system)
Hussein A. Abdullah
School of Engineering, University of Guelph, Guelph, Ontario N1G 2W1, Canada
Chris R. Chatwin
School of Engineering, University of Sussex, Brighton BN1 9QT, United Kingdom
This article reports results from an experimental investigation into laser welding of ferromagnetic material, which, for example, is of interest to the European Space Agency. The effects of laser welding power and translation velocities on the magnetism of ferromagnetic materials were studied. An automated system using a Hall effect transducer was constructed to measure the magnetic field transverse to the laser weld before welding, immediately after welding and thr...
JLA Vol:18 Iss:3 (Femtosecond laser production of metal surfaces having unique surface structures that are broadband absorbers)
Dennis R. Alexander
Center for Electro Optics and Electrical Engineering Department, University of Nebraska-Lincoln, 248 N WSEC, Lincoln, Nebraska 68588-0511
Femtosecond laser induced modification of surface structure and the optical properties of metals are studied. A Ti:sapphire femtosecond laser is used for ablating bulk aluminum 2024 T3 alloy and highly pure neutron activation quality gold metal samples at different laser irradiation parameters. The ablation parameters are optimized for the two metals to form a low reflection surface in the wavelength range of 0.3–50 μm. “Blac...
Laboratory of Laser Processing, Department of Mechanical Engineering, Lappeenranta University of Technology, Tuotantokatu 2, 53850 Lappeenranta, Finland
Laser cladding with fiber laser using scanning optics is a relatively new way of laser cladding. Modern oscillating scanners enable laser power adjustment according to scanning direction. This is a versatile tool for making process more stable as well as modifying the shape of clad bead. Laser cladding was made using 5 kW IPG fiber laser with ILV-oscillating scanner, using 316L powder as clad material and S355 mild steel plate as substrate mate...
G. J. Shannon
W. F. Deans
Department of Engineering, Laser Laboratory, Kings College, University of Aberdeen, Aberdeen, U.K.
An investigation was undertaken using a 1.2 kW carbon dioxide laser for underwater butt welding of BS 4360 43A and 50D steel, in order to assess the quality of the welds and to achieve an understanding of the laser/water/material interaction. Using a high‐speed camera, the temporal behavior of the melt pool and “plasma” dynamics surrounded by an aqueous environment were monitored. Experiments were undertaken to characterize the attenuation of the laser beam in the water as a function of various foca...
W. W. Duley
Physics Department, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
In many laser applications it is the conversion of photon energy to heat that drives the process. Heat transfer theory accurately describes the effects produced, and other aspects of thermodynamics need not generally be considered explicitly. The highly nonequilibrium nature of laser materials processing operations can usually be ignored once the heat transfer problem is defined. However, “equilibrium” is a concept that is basic to thermodynamics, and so it is useful to examine this concept in the context of traditional laser materials processing applications. Some of the ass...
JLA Vol:21 Iss:2 (Visualization of refraction and attenuation of near-infrared laser beam due to laser-induced plume)
Joining and Welding Research Institute (JWRI), Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan
This study was performed to obtain a fundamental knowledge of the interaction between a near-infrared laser beam and an induced plume during welding. The plume was characterized by spectroscopy, and the effect and mechanism of the laser-induced plume on the refraction and/or attenuation were investigated by high-speed video observation of the plume and the probe laser, and power meter measurement of the fiber probe laser beam of 1090 nm wavelength which pa...
Marc D. Friedman
Hans I. Bjelkhagen
Biomedical Engineering, Northwestern University, Evanston, Illinois
P. S. Mohanty
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...
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