Energy Coupling And Plume Dynamics During High Power Laser Heating Of Metals

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ISBN 13 :
Total Pages : 193 pages
Book Rating : 4.84/5 ( download)

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Download or read book Energy Coupling and Plume Dynamics During High Power Laser Heating of Metals written by and published by . This book was released on 1997 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: High power laser heating of metals was studied utilizing experimental and numerical methods with an emphasis on the laser energy coupling with a target and on the dynamics of the laser generated vapor flow. Rigorous theoretical modeling of the heating, melting, and evaporation of metals due to laser radiation with a power density below the plasma shielding threshold was carried out. Experimentally, the probe beam deflection technique was utilized to measure the propagation of a laser induced shock wave. The effects of a cylindrical cavity in a metal surface on the laser energy coupling with a solid were investigated utilizing photothermal deflection measurements. A numerical calculation of target temperature and photothermal deflection was performed to compare with the measured results. Reflection of the heating laser beam inside the cavity was found to increase the photothermal deflection amplitude significantly and to enhance the overall energy coupling between a heating laser beam and a solid. Next, unsteady vaporization of metals due to nanosecond pulsed laser heating with an ambient gas at finite pressure was analyzed with a one dimensional thermal evaporation model for target heating and one dimensional compressible flow equations for inviscid fluid for the vapor flow. Lastly, the propagation of a shock wave during excimer laser heating of aluminum was measured with the probe beam deflection technique. The transit time of the shock wave was measured at the elevation of the probe beam above the target surface; these results were compared with the predicted behavior using ideal blast wave theory. The propagation of a gaseous material plume was also observed from the deflection of the probe beam at later times.

Author : Sungho Jeong
Publisher :
ISBN 13 :
Total Pages : 392 pages
Book Rating : 4.37/5 ( download)

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Download or read book Energy Coupling and Plume Dynamics During High Power Laser Heating of Metals written by Sungho Jeong and published by . This book was released on 1997 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Author : A. M. Prokhorov
Publisher : CRC Press
ISBN 13 : 1351082396
Total Pages : 259 pages
Book Rating : 4.96/5 ( download)

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Download or read book Laser Heating of Metals written by A. M. Prokhorov and published by CRC Press. This book was released on 2018-01-31 with total page 259 pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to ensure efficient use of lasers, and for any large-scale implementation, a thorough knowledge of the fundamental laws governing the interaction of radiation with matter is required. Laser Heating of Metals provides a systematic and comprehensive presentation of the fundamental principles underlying the physical and chemical mechanisms governing the interaction of laser radiation with solid targets, and in particular metals in gaseous environments, for a wide range of beam parameters. The authors have been active in the field of interactions between lasers and materials for many years, and this book summarises the results of their work, in particular concerning the action of CO2 lasers on metals. These results are then discussed at some length. Laser Heating of Materials will be of interest to scientists at all levels with an interest in the interaction of radiation with condensed matter, and in particular to those involved in laser cutting and welding etc, and metal-working.

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ISBN 13 :
Total Pages : 380 pages
Book Rating : 4.27/5 ( download)

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Download or read book Proceedings of the ASME Heat Transfer Division written by and published by . This book was released on 1997 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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ISBN 13 :
Total Pages : 816 pages
Book Rating : 4.59/5 ( download)

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Download or read book Dissertation Abstracts International written by and published by . This book was released on 1998 with total page 816 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Author : Kedar Ashok Pathak
Publisher :
ISBN 13 :
Total Pages : 141 pages
Book Rating : 4.74/5 ( download)

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Download or read book Computational Modeling of Plume Dynamics in Multiple Pulse Laser Ablation of Carbon written by Kedar Ashok Pathak and published by . This book was released on 2008 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt: The flow field induced by the ablation plume in the presence of background gas is simulated numerically. The study of plume flow that occurs in laser ablation is important for it can yield information on ablation process itself and the properties of end product for which the ablation is carried out. Unsteady compressible axisymmetric Navier-Stokes equations govern the plume flow. The major challenge involved, even in this simplified model of plume dynamics, is twofold: (i) the time scale of simulation spans six orders of magnitude, from nanosecond to millisecond, and (ii) the high nonlinearity of governing equations because of high pressure, temperature and injection velocity of plume. A computational model is developed that can account for the entire range of time scale and high nonlinearity. This model is a combination of numerical methods and includes multi-time step and multi-size grid technique. The uniqueness of model lies in choosing the combination of numerical methods and handling multi-size grid interface in a conservative way. The combination of numerical methods is decided after comparing the results of few numerical methods for a single plume. The plume dynamics for single plume is explained with the help of proposed post-processing model based on vorticity dynamics. The model not only helps in understanding the expansion dynamics of plume but also provides quantitative comparison amongst numerical methods. The validity of nano-to-micro second range viscous and inviscid models of plume dynamics is discussed by means of evaluation of source terms in the vorticity transport equation. The role of turbulence is evaluated by millisecond-scale modeling of plume expanding in surrounding furnace gas with imposed turbulent gust. The results for multiple plumes typical for real life ablation are presented and discussed. Shielding of laser beam by previously ejected plume in multiple laser hits is important because it changes energy deposition of incident laser pulse at the target surface and in turn influences the ablation dynamics and amount of material removed. To account for this shielding effect, shielding models are developed and implemented. The quantity of ablated mass due to the shielding effect is evaluated. Ionization of carbon plume and its impact on plume dynamics and shielding is studied. An iterative procedure is developed to determine the local equilibrium temperature affected by ionization. It is shown that though shielding due to the presence of ionized particles in carbon plume is small, the effect of ionization on plume dynamics can be considerable. Shielding effect is calculated for laser pulses with different time interval between pulses. The effect of high temperature and low density of plume are controversary and cause shielding behavior to be non-monotonic with pulse number. It is shown that the non-monotonic dependence of the delivered laser energy with the pulse number and the difference in shielding characteristics between planar and axisymmetric formulations increase with the time duration between two consecutive pulses. The developed numerical methodology is employed to study the heat transfer modulation between the Thermal Protection Shield (TPS) and the gas flow occurring because of ejection of under-expanded pyrolysis gases through the cracks in the TPS in hypersonic flight. The simulations are performed for an axisymmetric bluff body flying at Mach 7. The influence of the geometry of the TPS on heat transfer pattern is studied for two representative shapes. The results are presented for three different flight altitudes (low-ground level, moderate-20km and high-30km). At the low altitude the plume pressure is lower than the pressure behind the detached front shockwave and the plume propagates slowly along the wall surface. At high and moderate altitudes, the plume path and consequently, convective heat transfer between the TPS and the plume depends on the plume interaction with the bow shock wave. The effect of viscosity for the plume injection conditions and free stream Mach number considered is found to be negligible at simulated altitudes. However, the effect of initial pressure of pyrolysis gas on the plume dynamics is significant. The presence of the blast wave associated with under-expanded plume alters the heat transfer and increases mixing. Finally, the enhanced heat transfer caused by the emergence of multiple pyrolysis plumes is investigated.

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ISBN 13 :
Total Pages : 212 pages
Book Rating : 4.44/5 ( download)

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Download or read book Laser-material Interactions written by and published by . This book was released on 1993 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study of laser-light interactions with solid materials ranges from low-temperature heating to explosive, plasma-forming reactions. Contained are four works concerning laser-energy coupling: laser (i) heating and (ii) melting monitored using a mirage effect technique, (iii) the mechanical stress-power generated during high-powered laser ablation, and (iv) plasma-shielding. First, a photothermal deflection (PTD) technique is presented for monitoring heat transfer during modulated laser heating of opaque solids that have not undergone phase-change. Of main interest is the physical significance of the shape, magnitude, and phase for the temporal profile of the deflection signal. Considered are the effects that thermophysical properties, boundary conditions, and geometry of the target and optical probe-beam have on the deflection response. PTD is shown to monitor spatial and temporal changes in heat flux leaving the surface due to changes in laser energy coupling. The PTD technique is then extended to detect phase-change at the surface of a solid target. Experimental data shows the onset of melt for indium and tin targets. The conditions for which melt can be detected by PTD is analyzed in terms of geometry, incident power and pulse length, and thermophysical properties of the target and surroundings. Next, monitoring high-powered laser ablation of materials with stress-power is introduced. The motivation for considering stress-power is given, followed by a theoretical discussion of stress-power and how it is determined experimentally. Experiments are presented for the ablation of aluminum targets as a function of energy and intensity. The stress-power response is analyzed for its physical significance. Lastly, the influence of plasma-shielding during high-powered pulsed laser-material interactions is considered. Crater size, emission, and stress-power are measured to determine the role that the gas medium and laser pulse length have on plasma shielding.

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ISBN 13 :
Total Pages : 704 pages
Book Rating : 4.04/5 ( download)

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Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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ISBN 13 :
Total Pages : 848 pages
Book Rating : 4.73/5 ( download)

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Download or read book American Doctoral Dissertations written by and published by . This book was released on 1999 with total page 848 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Author : KOJI SUGIOKA.
Publisher :
ISBN 13 : 9783319695372
Total Pages : pages
Book Rating : 4.71/5 ( download)

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Download or read book Handbook of Laser Micro- and Nano-Engineering written by KOJI SUGIOKA. and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This handbook provides a comprehensive review of the entire field of laser micro and nano processing, including not only a detailed introduction to individual laser processing techniques but also the fundamentals of laser-matter interaction and lasers, optics, equipment, diagnostics, as well as monitoring and measurement techniques for laser processing. Consisting of 11 sections, each composed of 4 to 6 chapters written by leading experts in the relevant field. Each main part of the handbook is supervised by its own part editor(s) so that high-quality content as well as completeness are assured. The book provides essential scientific and technical information to researchers and engineers already working in the field as well as students and young scientists planning to work in the area in the future. Lasers found application in materials processing practically since their invention in 1960, and are currently used widely in manufacturing. The main driving force behind this fact is that the lasers can provide unique solutions in material processing with high quality, high efficiency, high flexibility, high resolution, versatility and low environmental load. Macro-processing based on thermal process using infrared lasers such as CO2 lasers has been the mainstream in the early stages, while research and development of micro- and nano-processing are becoming increasingly more active as short wavelength and/or short pulse width lasers have been developed. In particular, recent advances in ultrafast lasers have opened up a new avenue to laser material processing due to the capabilities of ultrahigh precision micro- and nanofabrication of diverse materials. This handbook is the first book covering the basics, the state-of-the-art and important applications of the dynamic and rapidly expanding discipline of laser micro- and nanoengineering. This comprehensive source makes readers familiar with a broad spectrum of approaches to solve all relevant problems in science and technology. This handbook is the ultimate desk reference for all people working in the field.