The Experts below are selected from a list of 10458 Experts worldwide ranked by ideXlab platform
B S Yilbas - One of the best experts on this subject based on the ideXlab platform.
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three dimensional electron kinetic theory approach for Laser Heating moving heat source consideration
Physica A-statistical Mechanics and Its Applications, 1998Co-Authors: M Sami, B S YilbasAbstract:Abstract Lasers are extensively used for the heat treatment of engineering surfaces. The simulation of Laser Heating may enhance the understanding of the Process parameters and yields insight into the phenomena occurring within the region activated by the Laser beam. Consequently, in the present study, electron-kinetic theory approach is introduced to model the three-dimensional Laser Heating Process. However, the phase change (melting) Process is not considered in the present study due to the fact that the temperature of the heated surface is usually kept below the melting temperature of the substrate in most surface treatment Processes. Since the energy equation derived is in the form of an integro-differential equation, a numerical scheme using finite-difference approximation is employed. A Laser beam with a constant velocity is considered as scanning the workpiece surface. The study is extended to include three Laser beam scanning velocities, therefore, the respective temperature fields are computed. To validate the theoretical predictions, the surface temperature measurements are carried out. It is found that the surface temperature rises at low scanning velocities. In addition, the surface temperatures obtained from the measurements agree with the theoretical predictions.
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heat transfer analysis of Laser heated surfaces conduction limited case
Applied Surface Science, 1997Co-Authors: B S Yilbas, S Z ShujaAbstract:The Laser surface heat treatment technique is widely spread in industry for the treatment of the engineering parts. To improve the heat treatment Process, study of the heat transfer mechanism appropriate to the Laser Heating is necessary. The present study develops an analytical solution to the Laser Heating Process using the Fourier heat conduction model. The temperature distribution inside the substance together with its variations in the direction perpendicular to surface are predicted. The validity of the Fourier theory in Laser Heating is also discussed. To validate the theoretical predictions, the measurement of surface temperature is carried out. The study is extended to include the effect of the Laser output pulse lengths.
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an approach to convergency of kinetic theory to fourier theory in relation to Laser Heating Process
Japanese Journal of Applied Physics, 1993Co-Authors: B S Yilbas, Ahmet şah Z UinAbstract:Fourier theory may be derived from analytical considerations of the heat transfer Process in a substance and neglecting of higher order terms in Fourier analysis becomes important at high input power fluxes. It is apparent from the previous work that the kinetic theory equations governing the heat conduction Process are more general than the Fourier equation. The special case may exist where the kinetic theory solutions converge to solutions extracted from the Fourier analysis. Consequently, research into the convergence of kinetic theory approach to Fourier analysis becomes necessary. To achieve this, the special case in which local thermal equilibrium is assumed to exist between the electrons and atoms at any section on the surface region of the solid substance is studied in the present work, providing that the study does not allow the existence of phase changes. For this purpose, an analytical approach is introduced and a computer solution of the reduced integral equations is obtained. It is found that the solutions of electron kinetic theory equations based on the assumption of existence of thermal equilibrium between electrons and atoms are identical with those obtained from Fourier theory.
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analytical solution for the heat conduction mechanism appropriate to the Laser Heating Process
International Communications in Heat and Mass Transfer, 1993Co-Authors: B S YilbasAbstract:Abstract In the application of pulsed Laser material Processing, such as Laser hardening of metallic surfaces, conduction limited Heating is the dominant mechanism during Laser-workpiece interaction. Consequently, unsteady analysis of this problem becomes necessary. The present study examines the unsteady analysis of the conduction limited heat transfer Process for an exponential pulse input with time dependent intensity. It is shown that, in the limit, the solution obtained in the present case reduces to that obtained for a step input.
Cihan Karatas - One of the best experts on this subject based on the ideXlab platform.
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Laser surface treatment of Inconel 718 alloy: Thermal stress analysis
Optics and Lasers in Engineering, 2010Co-Authors: Bekir Sami Yilbas, Syed Sohail Akhtar, Cihan KaratasAbstract:Abstract Laser Heating of Inconel 718 alloy is considered and the resulting temperature and stress fields are predicted using the finite element method (FEM). An experiment is carried out to treat the alloy surface by a Laser beam at high pressure nitrogen environment. The metallurgical and morphological changes in the irradiated region are examined using the Scanning Electron Microscope (SEM), optical microscope, and X-ray Diffraction (XRD). It is found that the surface hardness of the alloy improves after the Laser Heating Process, which is due to the microstructural changes and γ-phase nitride formation in the surface region. The maximum value of the residual stress predicted in the irradiated region is close to the yielding limit of the alloy.
Benedict D Rogers - One of the best experts on this subject based on the ideXlab platform.
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smoothed particle hydrodynamics sph modelling of transient heat transfer in pulsed Laser ablation of al and associated free surface problems
Computational Materials Science, 2017Co-Authors: Ahmad W Alshaer, Benedict D RogersAbstract:A Smoothed Particle Hydrodynamics (SPH) numerical model is developed to simulate pulsed-Laser ablation Processes for micro-machining. Heat diffusion behaviour of a specimen under the action of nanosecond pulsed Lasers can be described analytically by using complementary error function solutions of second-order differential equations. However, their application is limited to cases without loss of material at the surface. Compared to conventional mesh-based techniques, as a novel meshless simulation method, SPH is ideally suited to applications with highly non-linear and explosive behaviour in Laser ablation. However, little is known about the suitability of using SPH for the modelling of Laser-material interactions with multiple phases at the micro scale. The present work investigates SPH modelling of pulsed-Laser ablation of aluminium where the Laser is applied directly to the free-surface boundary of the specimen. Having first assessed the performance of standard SPH surface treatments for functions commonly used to describe Laser Heating, the heat conduction behaviour of a new SPH methodology is then evaluated through a number of test cases for single- and multiple-pulse Laser Heating of aluminium showing excellent agreement when compared with an analytical solution. Simulation of real ablation Processes, however, requires the model to capture the removal of material from the surface and its subsequent effects on the Laser Heating Process. Hence, the SPH model for describing the transient behaviour of nanosecond Laser ablation is validated with a number of experimental and reference results reported in the literature. The SPH model successfully predicts the material ablation depth profiles over a wide range of Laser fluences 4–23 J/cm2 and pulse durations 6–10 ns, and also predicts the transient behaviour of the ejected material during the Laser ablation Process. Unlike conventional mesh-based methods, the SPH model was not only able to provide the thermo-physical properties of the ejected particles, but also the effect of the interaction between them as well as the direction and the pattern of the ejection.
Bekir Sami Yilbas - One of the best experts on this subject based on the ideXlab platform.
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Laser surface treatment of Inconel 718 alloy: Thermal stress analysis
Optics and Lasers in Engineering, 2010Co-Authors: Bekir Sami Yilbas, Syed Sohail Akhtar, Cihan KaratasAbstract:Abstract Laser Heating of Inconel 718 alloy is considered and the resulting temperature and stress fields are predicted using the finite element method (FEM). An experiment is carried out to treat the alloy surface by a Laser beam at high pressure nitrogen environment. The metallurgical and morphological changes in the irradiated region are examined using the Scanning Electron Microscope (SEM), optical microscope, and X-ray Diffraction (XRD). It is found that the surface hardness of the alloy improves after the Laser Heating Process, which is due to the microstructural changes and γ-phase nitride formation in the surface region. The maximum value of the residual stress predicted in the irradiated region is close to the yielding limit of the alloy.
S Z Shuja - One of the best experts on this subject based on the ideXlab platform.
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heat transfer analysis of Laser heated surfaces conduction limited case
Applied Surface Science, 1997Co-Authors: B S Yilbas, S Z ShujaAbstract:The Laser surface heat treatment technique is widely spread in industry for the treatment of the engineering parts. To improve the heat treatment Process, study of the heat transfer mechanism appropriate to the Laser Heating is necessary. The present study develops an analytical solution to the Laser Heating Process using the Fourier heat conduction model. The temperature distribution inside the substance together with its variations in the direction perpendicular to surface are predicted. The validity of the Fourier theory in Laser Heating is also discussed. To validate the theoretical predictions, the measurement of surface temperature is carried out. The study is extended to include the effect of the Laser output pulse lengths.
