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...
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JLA Vol:24 Iss:5 (The numerical analysis and measurements of temperature profile in fat tissue during neodymium-doped yttrium aluminum garnet laser irradiation for laser-assisted lipolysis)
Authors:
Jong-In Youn
Department of Biomedical Engineering, College of Medical Science, Catholic University of Daegu, Hayangeup, Gyongsansi, Gyongbuk 712-702, South KoreaThe purpose of the study is to investigate the temperature profile of fat tissue during neodymium-doped yttrium aluminum garnet laser irradiation (1064, 1320, and 1444 nm wavelengths) for laser-assisted lipolysis. The numerical analysis was performed to assess the wavelength dependence of the temperature distribution in fat tissue. For the internal temperature profile measurements, a cannula was placed in the middle of fat tissue for laser irradiation, and two hypodermic thermocouple needles were placed at 2 and 5 mm...
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JLA Vol:16 Iss:2 (High-power CO<sub>2</sub> laser design “from resonator end mirror to cutting lens focal point”)
Authors:
David Toebaert
HACO NV, Oekenestraat 120, 8800 Rumbeke, Belgium
Wybo Wagenaar
Infinite Simulation Systems BV, Lange Bunder 3, 4854 MB Bavel, NetherlandsAn algorithm is derived that allows calculating all optical parameters relevant to the design of a high-power CO2 laser, taking into account the practical needs of a flying-optics type of laser cutting machine. The novelty of the approach taken is that the resonator and the beam delivery optics are treated simultaneously, which allows for greater flexibility in design. To begin with, the often-used optical configuration of a stable resonator combined with a beam expander for collimation is mod...
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JLA Vol:20 Iss:3 (Investigation of femtosecond laser induced thermal ablation of polyethylene)
Authors:
Andrew J. Lee
Judith M. Dawes
Michael J. Withford
Centre of Ultrahigh-bandwidth Devices for Optical Systems (CUDOS) and MQPhotonics Research Centre, Department of Physics, Macquarie University, 2109 NSW, AustraliaWe present a novel method for profiling high aspect ratio and undercut laser drilled holes using sacrificial layers. This profiling method is used to compare and contrast laser ablation of polyethylene films under exposure to ultraviolet (266 nm) and near-infrared (800 nm) radiation from an ultrafast, femtosecond laser. We find that ultraviolet femtosecond pulsed laser processing of this polymer exhibits similar characteristics to...
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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)
Authors:
David L. Carroll
James A. RothenflueA 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...
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JLA Vol:4 Iss:2 (Dynamic Laser Doppler Velocimetry on Solid Surfaces)
Authors:
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...
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JLA Vol:14 Iss:2 (Deformation behavior and microstructural changes of a hardened high carbon alloy steel in laser bending)
Authors:
K. C. Chan
J. Liang
Department of Manufacturing Engineering, The Hong Kong Polytechnic University, Kowloon, Hong KongIn this article, the deformation behavior and microstructure of a hardened high carbon steel in laser bending were examined. A CO2 laser unit (TEM00) was used to bend the samples at different laser powers, scanning velocities, and number of scans. A relatively linear relationship between bending angle and number of scans was obtained at laser powers of 150 and 200 W and at a scanning velocity of 30 mm/s. A threshold heat input of about 3.25 J/mm was observed, below which bending was unlikely to occur. The bending angle was al...
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JLA Vol:18 Iss:3 (Femtosecond laser bulk micromachining of microfluid channels in poly(methylmethacrylate))
Authors:
Dave F. Farson
Hae Woon Choi
Department of Industrial, Welding and Systems Engineering, The Ohio State University, Columbus, Ohio 43221
Chunmeng Lu
L. James Lee
Department of Chemical and Biomolecular Engineering, The Ohio State University, Columbus, Ohio 43221Internal channels in a polymer are widely used in biotechnology applications such as DNA stretching and in devices such as micrototal analysis systems and lab on a chip systems. For manufacturing prototype devices, femtosecond pulsed laser energy has been used to implement a convenient direct write bulk-machining process in glass. In this technique, the laser beam is focu...
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JLA Vol:23 Iss:2 (Experimental investigation of laser shock peening using femtosecond laser pulses)
Authors:
Dongkyun Lee
Elijah Kannatey-Asibu
Department of Mechanical Engineering, The University of Michigan, Ann Arbor, Michigan 48105-2125In this study, the feasibility of laser shock peening using ultrafast laser pulses was experimentally investigated. A top coating of zinc with a water confining layer was applied in the investigation. The zinc coating was used for the thermoprotective effect. A high numerical aperture (NA≅0.5) aspheric lens was used to minimize the optical breakdown of water. Microhardness measurements were made on the top surface of the shock peened specimen and compared with the original material hardness. The results provide useful insight on...
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JLA Vol:7 Iss:3 (Laser beam surveying, refractive index measurements and the making of a 360° reflection hologram)
Authors:
David Foster
Notre Dame High School, 596 South Second St., San Jose, California 95112, U.S.A.Triangulation measurements, using a laser to find the height of a room and of buildings, will be described first. This will be followed by triangulation and laser beam divergence measurements for range finding. The use of a hollow prism to hold liquids, whose refractive indicies are to be found, will then be described. The final topic will describe how a 360° reflection hologram was made at Notre Dame High School, utilizing three lasers and beam spreaders and four lasers and beam spreaders. The 360° hologram, made by a student, will be available for viewing.
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