JLA Vol:17 Iss:3 (Three-dimensional transient finite element analysis for residual stresses in the laser aided direct metal/material deposition process)
Authors:
S. Ghosh
J. Choi
Department of Mechanical and Aerospace Engineering, University of Missouri-Rolla, Rolla, Missouri 65409Despite immense advances in the laser aided direct metal/material deposition (DMD) process many issues concerning the adverse effects of process parameters on the stability of variety of properties and the integrity of microstructure have been reported. Comprehensive understanding of the transport phenomena and heat transfer analysis including phase transformations are essential to predict the effects of thermally induced residual stresses and distortions in the deposited materials. A complete model that provides a quantitative relationship bet...
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JLA Vol:17 Iss:4 (Adaptive direct metal/material deposition process using a fuzzy logic-based controller)
Authors:
Y. Hua
J. Choi
Department of Mechanical & Aerospace Engineering, University of Missouri-Rolla, Rolla, Missouri 65409The laser aided direct metal/material deposition (DMD) process is a layered manufacturing process able to produce a three-dimensional (3D) part directly from a computer aided design image. A closed-loop feedback control system is considered as a requirement to ensure dimensional accuracy. For conventional control methods, the effectiveness of process control strongly relies on accuracy of the analytical model of the system behavior. However, development of such an analytical model is quite difficult and impractical, since coupled process variab...
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JLA Vol:17 Iss:4 (An investigation into delamination mechanisms in inclined laser drilling of thermal barrier coated aerospace superalloys)
Authors:
H. K. Sezer
A. J. Pinkerton
Lin Li
Laser Processing Research Centre, Department of Mechanical, Aerospace and Manufacturing Engineering, UMIST, Manchester M60 1QD, United Kingdom
P. Byrd
Manufacturing Technology, Rolls Royce, Filton, Bristol BS34 7QW, United KingdomThermal barrier coatings are widely used in aircraft engine hot-end components to protect the component materials from direct exposure to the damaging high temperatures. Effusion cooling techniques are widely used in these situations and laser drilling is normally employed to produce holes of less than 1.5 mm diameter in tough aerospace alloys coated with heat-re...
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JLA Vol:17 Iss:4 (Characteristics of parallel irradiations in laser forming of stainless steel)
Authors:
J. Pennuto
J. Choi
Department of Mechanical and Aerospace Engineering, University of Missouri, Rolla, Missouri 65409The manufacturability of stainless steels has been extensively studied, but the spring back effect during material deformation continues to result in a costly trial and error tooling process. In an effort to develop a process free of dedicated tooling, this research seeks to study large radius deformation by laser forming. This is useful for shapes such as the lead edge of airfoils on airplane wings and rotor blades. Experimental testing was conducted to determine how the single pass output bend angle relates to the laser parameters of power, trave...
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JLA Vol:17 Iss:4 (Developments towards controlled three-dimensional laser forming of continuous surfaces)
Authors:
S. P. Edwardson
E. Abed
P. French
G. Dearden
K. G. Watkins
Laser Group, Department of Engineering, The University of Liverpool, Liverpool L69 3GH, United Kingdom
R. McBride
D. P. Hand
J. D. C. Jones
A. J. Moore
School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United KingdomThere has been a considerable amount of work carried out on two-dimensional laser forming, using multipass straight line scan strategies to produce a reasonably controlled bend angle in a number of materials, including aerospace alloys. However, in order t...
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JLA Vol:17 Iss:4 (Effect of steel composition on the laser cutting behavior of 25-mm-thick plates)
Authors:
M. Manohar
R. L. Bodnar
Mittal Steel USA R&D, Bethlehem, Pennsylvania
R. I. Asfahani
U.S. Steel Research and Technology Center, Monroeville, Pennsylvania
N. Chen
C. Huang
Caterpillar Technical Center, Peoria, IllinoisAttempts were made to gain a better understanding of the effects of steel composition and thermophysical properties, such as solidus and liquidus temperatures, heat of oxidation, surface tension, viscosity and thermal conductivity, on laser-cutting behavior. Laboratory-produced heats containing varying levels of C, S, Si, Cu, Ni, Cr, and Mo were hot-rolled to 32-mm-thick plates. Laser cutt...
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JLA Vol:17 Iss:4 (Examination of laser hardened steel surfaces using interference microscopy)
Authors:
Henrikki Pantsar
Laser Processing Laboratory of Lappeenranta University of Technology, Lappeenranta, FinlandA diode laser beam in the near-infrared region is absorbed more efficiently by a metal surface than a CO2 or a Nd:yttrium-aluminum-garnet laser beam. Diode laser transformation hardening without an absorptive coating is feasible even in an inert gas atmosphere. Absence of the absorptive coating, and the fact that the formation of an oxide layer is inhibited, makes it possible to study phase transformations occurring during hardening from the surface relief formed to the processed surface. In the present study diamond polished plain carbon and low alloy steel...
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JLA Vol:17 Iss:4 (Faster and damage-reduced laser cutting of thick ceramics using a simultaneous prescore approach)
Authors:
V. Pereles-Santiago
M. Washington
P. Brugan
G. Cai
R. Akarapu
S. Pulford
A. E. Segall
The Pennsylvania State University, University Park, Pennsylvania 16802Laser machining of structural ceramics is increasingly gaining acceptance as an alternative to traditional machining methods. However, despite the great promise of lasers for a variety of cutting and drilling procedures, premature fractures and prohibitively low cutting speeds are still among the greatest obstacles encountered, particularly when thick cross sections are involved. While many factors contribute to the fractures encountered during ...
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JLA Vol:17 Iss:4 (Femtosecond pulse stretching in microscope objectives used for micro/nanomachining)
Authors:
Nageswara Rao Tadepalli
Dennis Alexander
David Doerr
Jianchao Li
Haifeng Zhang
Department of Electrical Engineering and Center for Electro-Optics, University of Nebraska-Lincoln, Nebraska 68588-0511Femtosecond laser pulses are stretched when they pass through an optical microscope objective used for laser machining. The question that must be answered is how much does the pulse stretch passing through the objective. Stretching of pulses would be more prominent in the case of ultrashort laser pulses (∼9 fs). In this article, a study was performed to measure the final pulse duration for a 9 fs laser pulse passing...
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JLA Vol:17 Iss:4 (Pit and rim formation during laser marking of acrylonitrile butadiene styrene plastic)
Authors:
Yongjin Shin
Department of Physics, Chosun University, Gwangju 501-759, South Korea and Beckman Laser Institute, University of California at Irvine, Irvine, California 92612
Youngseop Kim
Sohee Park
Laser Imaging Laboratory, Chosun University, Gwangju 501-759, South Korea
Byungjo Jung
Department of Biomedical Engineering, Yonsei University, Wonju 220–710, South Korea
Jangwoen Lee
J. Stuart Nelson
Beckman Laser Institute, University of California at Irvine, Irvine, California 92612Pit and rim formation on the acrylonitrile butadiene styrene (ABS) plastic surface was evaluated aft...
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