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Bekir Sami Yilbas - One of the best experts on this subject based on the ideXlab platform.
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Laser gas assisted texturing and formation of nitride and oxynitride compounds on alumina Surface: Surface response to environmental dust
Optics and Lasers in Engineering, 2018Co-Authors: Bekir Sami Yilbas, Hafiz Muhammad Ali, Abdullah Al-sharafi, N. Al-aqeeliAbstract:Abstract Laser gas assisted texturing of alumina Surface is carried out, and formation of nitride and oxynitride compounds in the Surface Vicinity is examined. The laser parameters are selected to create the Surface topology consisting of micro/nano pillars with minimum defect sites including micro-cracks, voids and large size cavities. Morphological and hydrophobic characteristics of the textured Surface are examined using the analytical tools. The characteristics of the environmental dust and its influence on the laser textured Surface are studied while mimicking the local humid air ambient. Adhesion of the dry mud on the laser textured Surface is assessed through the measurement of the tangential force, which is required to remove the dry mud from the Surface. It is found that laser texturing gives rise to micro/nano pillars topology and the formation of AlN and AlON compounds in the Surface Vicinity. This, in turn, lowers the free energy of the textured Surface and enhances the hydrophobicity of the Surface. The liquid solution resulted from the dissolution of alkaline and alkaline earth metals of the dust particles in water condensate forms locally scattered liquid islands at the interface of mud and textured Surface. The dried liquid solution at the interface increases the dry mud adhesion on the textured Surface. Some dry mud residues remain on the textured Surface after the dry mud is removed by a pressurized desalinated water jet.
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Laser gas assisted treatment of steel 309: Corrosion and scratch resistance of treated Surface
Optics & Laser Technology, 2017Co-Authors: Ihsan-ul-haq Toor, Bekir Sami Yilbas, Junaid Ahmed, Cihan KaratasAbstract:Abstract Laser gas assisted Surface treatment of steel 309 is carried out and the characteristics of the resulting Surface are analyzed using the analytical tools. Scanning electron and 3-D optical microscopes are used to assess the morphological and metallurgical changes in the laser treated layer. Energy spectroscopy and X-ray diffraction are carried out to determine the elemental composition and compounds formed on the laser treated Surface. The friction coefficient of the laser treated Surface is measured using the micro-tribometer and compared to that of the as received Surface. The corrosion resistance of the laser treated and as received Surfaces is measured incorporating the electrochemical tests. It is found that laser treatment results in a dense layer and formation of nitride compounds at the Surface. This enhances the microhardness at the laser treated Surface. The friction coefficient attains lower values at the laser treated Surface than that corresponding to the as received Surface. The corrosion rate of the Surface reduces significantly after the laser treatment process, which can be attributed to the passive layer at the Surface via formation of a dense layer and nitride compounds in the Surface Vicinity. In addition, the number of pit sites decreased for the laser treated Surface than that of as received Surface.
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Laser controlled melting of H12 hot-work tool steel with B4C particles at the Surface
Optics & Laser Technology, 2015Co-Authors: Bekir Sami Yilbas, F. Patel, Cihan KaratasAbstract:Abstract Laser controlled melting of pre-prepared H12 hot-work tool steel Surface is carried out. B 4 C particles in the carbon film are located at the workpiece Surface prior to the laser treatment process. Nitrogen at high pressure is used as an assisting gas during the laser melting. Morphological and metallurgical changes in the treated layer are examined using scanning electron microscope, energy dispersive spectroscopy, and X-ray diffraction. Microhardness of the treated Surface is measured and the residual stress formed at the treated Surface Vicinity is obtained using the X-ray diffraction technique. It is found that a dense layer consisting of fine grains is formed at the treated Surface. Microhardness of the treated Surface improves significantly because of fine grains, nitride compounds formed at the Surface and micro-stresses developed due to mismatched of thermal expansion coefficients of B 4 C and the base material. The residual stress formed at the Surface is suppressed by the self annealing effect of the initially formed laser scans.
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Flow into a hole in relation to laser drilling: influence of coating thickness
International Journal of Numerical Methods for Heat & Fluid Flow, 2014Co-Authors: S Z Shuja, Bekir Sami YilbasAbstract:Purpose – In laser drilling applications, hole wall remains almost the melting temperature of the substrate material and the thermodynamic pressure developed at high temperature molten Surface Vicinity influences the heat transfer rates and the skin friction at the Surface of the hole wall. This effect becomes complicated for the holes drilled in coated substrates. In this case, melting temperatures of the coating and base materials are different, which in turn modifies the flow field in the hole due to jet impingement. Consequently, investigation of the heat transfer rates from the hole wall Surfaces and the skin friction at the hole Surface becomes essential. The paper aims to discuss these issues. Design/methodology/approach – Numerical solution for jet impingement onto a hole with high wall temperature is introduced. Heat transfer rates and skin friction from the hole wall is predicted. The numerical model is validated with the experimental data reported in the open literature. Findings – The Nusselt ...
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Laser Treatment of Rene-41: Thermal and Microstructural Analysis
Journal of Manufacturing Science and Engineering, 2013Co-Authors: Bekir Sami Yilbas, Sohail Akhtar, Cihan KaratasAbstract:Laser treatment of Rene 41 Surface is carried out at high pressure environment of nitrogen. Temperature and stress fields are predicted using abaqus finite element code. Metallurgical and morphological changes in the laser treated layer are examined using optical and scanning electron microscopes (SEM). The residual stress formed at the Surface Vicinity is obtained by X-ray diffraction (XRD) technique. It is found that the predictions of the residual stress agree well with the results obtained from the XRD technique. Cellular or cellular dendritic structures with fine secondary dendrites are formed in the laser treated Surface due to high cooling rates. In addition, γ′ particles formed are generally in cubic morphology with varying sizes.
Cihan Karatas - One of the best experts on this subject based on the ideXlab platform.
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Laser gas assisted treatment of steel 309: Corrosion and scratch resistance of treated Surface
Optics & Laser Technology, 2017Co-Authors: Ihsan-ul-haq Toor, Bekir Sami Yilbas, Junaid Ahmed, Cihan KaratasAbstract:Abstract Laser gas assisted Surface treatment of steel 309 is carried out and the characteristics of the resulting Surface are analyzed using the analytical tools. Scanning electron and 3-D optical microscopes are used to assess the morphological and metallurgical changes in the laser treated layer. Energy spectroscopy and X-ray diffraction are carried out to determine the elemental composition and compounds formed on the laser treated Surface. The friction coefficient of the laser treated Surface is measured using the micro-tribometer and compared to that of the as received Surface. The corrosion resistance of the laser treated and as received Surfaces is measured incorporating the electrochemical tests. It is found that laser treatment results in a dense layer and formation of nitride compounds at the Surface. This enhances the microhardness at the laser treated Surface. The friction coefficient attains lower values at the laser treated Surface than that corresponding to the as received Surface. The corrosion rate of the Surface reduces significantly after the laser treatment process, which can be attributed to the passive layer at the Surface via formation of a dense layer and nitride compounds in the Surface Vicinity. In addition, the number of pit sites decreased for the laser treated Surface than that of as received Surface.
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Laser controlled melting of H12 hot-work tool steel with B4C particles at the Surface
Optics & Laser Technology, 2015Co-Authors: Bekir Sami Yilbas, F. Patel, Cihan KaratasAbstract:Abstract Laser controlled melting of pre-prepared H12 hot-work tool steel Surface is carried out. B 4 C particles in the carbon film are located at the workpiece Surface prior to the laser treatment process. Nitrogen at high pressure is used as an assisting gas during the laser melting. Morphological and metallurgical changes in the treated layer are examined using scanning electron microscope, energy dispersive spectroscopy, and X-ray diffraction. Microhardness of the treated Surface is measured and the residual stress formed at the treated Surface Vicinity is obtained using the X-ray diffraction technique. It is found that a dense layer consisting of fine grains is formed at the treated Surface. Microhardness of the treated Surface improves significantly because of fine grains, nitride compounds formed at the Surface and micro-stresses developed due to mismatched of thermal expansion coefficients of B 4 C and the base material. The residual stress formed at the Surface is suppressed by the self annealing effect of the initially formed laser scans.
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Laser Treatment of Rene-41: Thermal and Microstructural Analysis
Journal of Manufacturing Science and Engineering, 2013Co-Authors: Bekir Sami Yilbas, Sohail Akhtar, Cihan KaratasAbstract:Laser treatment of Rene 41 Surface is carried out at high pressure environment of nitrogen. Temperature and stress fields are predicted using abaqus finite element code. Metallurgical and morphological changes in the laser treated layer are examined using optical and scanning electron microscopes (SEM). The residual stress formed at the Surface Vicinity is obtained by X-ray diffraction (XRD) technique. It is found that the predictions of the residual stress agree well with the results obtained from the XRD technique. Cellular or cellular dendritic structures with fine secondary dendrites are formed in the laser treated Surface due to high cooling rates. In addition, γ′ particles formed are generally in cubic morphology with varying sizes.
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Laser controlled melting of HSLA steel Surface with presence of B4C particles
Applied Surface Science, 2013Co-Authors: Bekir Sami Yilbas, F. Patel, Cihan KaratasAbstract:Abstract Laser gas assisted melting of high strength low alloy steel Surface is carried out. The alloy Surface is pre-prepared to contain 5% B 4 C particles in a 40 μm thick carbon film prior to laser treatment process. Metallurgical and morphological changes in the laser treated layer are examined by using scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. The residual stress developed and the microhardness of the resulting Surface is measured. It is found that B 4 C particles remain in solid phase in the Surface region due to their high melting temperature. The dense layer consisting of fine grains are formed at the Surface and the feathery like structure is observed below the Surface Vicinity, which consists of martensite and nitride precipitations. The use of nitrogen at high pressure causes the formation of nitride compounds at the Surface, which contributes to the volume shrinkage in the dense layer. Surface microhardness increases considerably because of attainment of high cooling rates, formation of nitride compounds, and presence of B 4 C particles at the Surface.
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Laser control melting of alumina Surfaces with presence of B4C particles
Journal of Alloys and Compounds, 2012Co-Authors: Bekir Sami Yilbas, Nasser Al-aqeeli, Cihan KaratasAbstract:Abstract Laser gas assisted controlled melting of alumina tile Surface is carried out in this work. A carbon coating containing 5% of B 4 C particles is formed at the tile Surface prior to laser treatment process. The morphological and microstructural changes in the treated layer are examined using X-ray diffraction, energy dispersive spectroscopy, and scanning electron microscope. The Surface microhardness is measured and the residual stress formed at the Surface Vicinity is obtained from the X-ray diffractograms. It was found that microhardness of the Surface increases significantly after the laser treatment process, which is attributed to high cooling rates and the formation of nitride species at the Surface. The residual stress formed at the Surface is compressive and no micro- or major-cracks are observed at the laser treated Surface.
B S Yilbas - One of the best experts on this subject based on the ideXlab platform.
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laser gas assisted nitriding and characterization of tungsten Surface
Optics and Laser Technology, 2018Co-Authors: B S Yilbas, C Karatas, Abdullah AlsharafiAbstract:Abstract Laser gas assisted nitriding of tungsten Surface is carried out while incorporating the high pressure nitrogen assisting gas. Metallurgical and morphological changes in the laser treated layer are examined using the analytical tools. The nitride compounds formed in the Surface Vicinity are analyzed incorporating X-ray diffractogram and Fourier-transform infrared spectroscopy. The wetting state and the free energy of the laser treated Surface is determined using the droplet contact angle method. The friction coefficient of the resulting Surface is measured via microtribometer and UV visible absorption characteristic of the Surface is analyzed. It is found that the laser texturing of tungsten Surface results in micro/nano size pillars without forming micro-cracks and large size cavities. The laser treatment gives rise to hydrophobic Surface characteristic with improved UV visible spectrum absorption coefficient. The microhardness increased significantly because of the nitride compounds formed at the Surface and friction coefficient shows wave-like behavior because of the Surface texture.
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Laser controlled melting of Hastelloy X alloy with presence of B4C particles at Surface
Materials Science and Technology, 2013Co-Authors: B S YilbasAbstract:AbstractLaser controlled melting of pre-prepared Hastelloy X alloy Surface is carried out at high nitrogen gas pressure environment. The pre-prepared workpiece Surface consists of 40 μm carbon film with uniformly distributed 5%B4C particles. The carbon film enhances the absorption of the incident laser irradiation and holds B4C particles at the workpiece Surface prior to the laser treatment process. The morphological and metallurgical changes in the treated layer are characterised using scanning electron microscope, energy dispersive spectroscopy, and X-ray diffraction. The microhardness at the treated Surface and the residual stress formed in the Surface Vicinity are measured. It is found that dense layer consists of fine grains are formed at the Surface because of the high cooling rates. Locally distributed undissolved B4C particles are observed at the Surface due to high melting temperature of B4C. Although thermal expansion coefficients of B4C and the base material are different, no microcracks are to...
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Effects of Laser Re-melting on the Corrosion Properties of HVOF Coatings
Journal of Materials Engineering and Performance, 2013Co-Authors: B S Yilbas, I. H. Toor, F. Patel, M. A. BaigAbstract:HVOF coating of Inconel 625 powder on carbon steel is carried out. Laser melting of the resulting coating is realized to improve coating structural integrity. Morphological and microstructural changes are examined in the coating prior and after laser treatment process using scanning electron microscopy, energy dispersive spectroscopy, and x-ray diffraction (XRD). The residual stress developed is measured on the Surface Vicinity of the laser-treated coating using the XRD technique. The corrosion resistance of the laser-treated and untreated coating Surfaces is measured, incorporating the potentiodynamic tests in 0.5 M NaCl aqueous solution. It is found that laser treatment reduces the pores and produces cellular structures with different sizes and orientations in the coating. Laser-controlled melting improves the corrosion resistance of the coating Surface.
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laser embedding of tic particles into the Surface of phosphor bronze bearing material
Surface and Interface Analysis, 2012Co-Authors: B S Yilbas, C Karatas, S. S. Akhtar, Chris ChatwinAbstract:A carbon film containing 5% TiC particles is formed on a pre-prepared bronze Surface prior to laser treatment. The carbon film provides increased absorption of the incident laser beam and hosts TiC particles with a uniform distribution at the workpiece Surface. Optical and scanning electron microscopy are used to examine the metallurgical and morphological changes in the laser treated layer. Micro-hardness of the laser-treated Surface is measured, and the residual stress formed in the Surface Vicinity is measured using the X-ray diffraction technique. It was found that a dense layer with fine grains was formed in the laser-treated layer. The micro-hardness of the laser-treated Surface increases almost three times compared with the base material hardness. The presence of a dense layer and the formation of Cu 3N in the Surface region contribute to the hardness enhancement at the Surface. Copyright © 2012 John Wiley & Sons, Ltd.
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Corrosion Properties and Morphology of Laser Melted Aluminum Alloy 8022 Surface
Journal of Materials Engineering and Performance, 2009Co-Authors: B S Yilbas, M. Khaled, C KaratasAbstract:Laser Surface melting of aluminum alloy 8022 is considered and electrochemical studies of the laser-melted and as-received alloy Surface are carried out. The Surface morphology and metallurgical changes in the laser-melted region are examined using optical microscopy, electron scanning microscopy (SEM), and atomic force microscopy (AFM). Elemental changes in the specimens after the laser-melting process are examined using energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD) is used for assessment of the compound formed after the laser-treatment process. Nitrogen is used as an assisting gas during the laser-melting process to prevent high-temperature oxidation reactions. It is found that the laser-melted Surfaces is free from cracks and deep cavities. The oxygen diffusion in the Surface region of the melt layer forms Al_2O_3 compound in the Surface Vicinity. The corrosion current increases significantly for the laser-melted specimens due to the irregular Surface structure. AC impedance results showed a decrease in pores resistant and an increase in pores capacitance. In addition, the Surface morphology resulting from the laser melting gives rise to pitting sites at the Surface.
Abul Fazal M. Arif - One of the best experts on this subject based on the ideXlab platform.
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Prediction of Residual Stresses During Gas Nitriding of H13 Steels Using Phase Field Approach
Journal of Manufacturing Science and Engineering, 2015Co-Authors: Syed Sohail Akhtar, Abba Abdulhamid Abubakar, Abul Fazal M. ArifAbstract:Gas nitriding is a common Surface treatment practice to improve the wear resistance of AISI H13 hot extrusion die cavities. However, due to the presence of complex and sharp features of die cavities, it has been observed that nonuniform nitride layer develops in these regions. Moreover, the formation of compound layer in the Surface Vicinity of nitrided Surfaces leads to the development of transformation-induced stresses. The present work presents the application of the phase field method in predicting the evolution of the nitride layers and associated residual stresses during the gas nitriding of AISI H13 tool steels. Nitriding process is modeled and simulated in line with experimental setup, which uses automated two-stage controlled nitriding process. Some representative samples having commonly used geometric features are manufactured and nitrided for validation purpose. Both experimental and numerical results are found in close agreement in terms of nitrogen concentration and corresponding microhardness profiles. The results show that high stresses are induced at the Surface due to formation of the nitride layers, and these stresses are found to be higher at the sharp corners. In view of the current results, some process and design strategies are suggested for improved and more effective nitriding treatment of hot extrusion dies used in the industry.
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Prediction of Transformation-Induced Residual Stresses During Gas Nitriding of H13 Steels Using Phase Field Approach
Volume 14: Emerging Technologies; Engineering Management Safety Ethics Society and Education; Materials: Genetics to Structures, 2014Co-Authors: Syed Sohail Akhtar, Abba Abdulhamid Abubakar, Abul Fazal M. ArifAbstract:Gas nitriding is a common Surface treatment practice to improve the wear resistance of AISI H13 hot extrusion die cavities. However, due to the presence of complex and sharp features of die cavities, it has been observed that non-uniform nitride layer develops in these regions. Moreover, the formation of compound layer in the Surface Vicinity of nitrided Surfaces leads to the development of transformation-induced stresses. The present work presents the application of the phase field method in predicting the evolution of the nitride layers and associated residual stresses during the gas nitriding of AISI H13 tool steels. Nitriding process is modeled and simulated in line with experimental set-up which uses automated two-stage controlled nitriding process. Some representative samples having commonly used geometric features are manufactured and nitrided for validation purpose. Both experimental and numerical results are found in close agreement in terms of nitrogen concentration and corresponding micro-hardness profiles. The results show that high stresses are induced at the Surface due to formation of the nitride layers and these stresses are found to be higher at the sharp corners. In view of the current results, some process and design strategies are suggested for improved and more effective nitriding treatment of hot extrusion dies used in the industry.Copyright © 2014 by ASME
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Laser bending of AISI 304 steel sheets: Thermal stress analysis
Optics & Laser Technology, 2012Co-Authors: Bekir Sami Yilbas, Abul Fazal M. Arif, B.j. Abdul AleemAbstract:Abstract Laser induced bending of steel sheet is carried out and thermal stress developed in the heated region is examined. Temperature and stress fields are predicted using the finite element model. The microstructural changes in the melted region are investigated through scanning electron microscope, energy dispersive spectroscopy and X-ray diffraction. The residual stress developed at the Surface Vicinity of the laser treated region is measured using the X-ray diffraction technique, which is then compared with its counterpart predicted from the simulations. It is found that the residual stress at the Surface Vicinity is compressive and the prediction of the residual stress agrees well with that obtained from the X-ray diffraction technique. In addition, Surface temperature predictions are in good agreement with the thermocouple data. The laser treated region is free from major cracks and large cavities.
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Laser treatment of aluminum Surface: Analysis of thermal stress field in the irradiated region
Journal of Materials Processing Technology, 2009Co-Authors: Bekir Sami Yilbas, Cihan Karatas, Abul Fazal M. Arif, Kabeer RazaAbstract:Laser Surface treatment of aluminum is considered and the temperature as well as the stress fields developed in the laser irradiated region are predicted using the finite element method (FEM). The predictions are obtained for two laser pulses with different pulse lengths. In the simulations, the variable thermal properties of the substrate material are used. The experiment is conducted to treat the aluminum specimen Surface with the laser beam. The laser output pulse intensity consists of repetitive pulses, which are used in the model study to examine the metallurgical changes in the irradiated region. SEM and XRD are carried out in this regard. It is found that the von-Mises stress reaches the maximum in the Surface Vicinity, particularly at the onset of cooling cycle starts. The von-Mises stress attains values less than the critical values for the crack formation, which is particularly true after the end of the cooling cycle. The residual stress formed in the Surface region is in the order of a few MPa.
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Laser short pulse heating of copper: Thermo–elasto–plastic analysis
Journal of Laser Applications, 2004Co-Authors: Abul Fazal M. Arif, Bekir Sami YilbasAbstract:Laser short pulse heating of metallic substrates results in excessive electron temperatures in the Surface Vicinity. This gives rise to nonequilibrium energy transport in the region irradiated by a laser beam. Moreover, the thermomechanical coupling effect should be incorporated into the energy transport equation as lattice site temperature increases. In the present study, laser short pulse heating of copper is considered. The electron kinetic theory approach is employed to model the nonequilibrium heating process while thermomechanical coupling is introduced in the energy transport equation to account for the thermomechanical response of the substrate material. In order to determine the stress field, due to temperature gradient in the laser irradiated region, thermo–elastic and thermo–elasto–plastic analyses are carried out. Temperature and stress fields are computed numerically. It is found that temperature gradient is higher in the region next to the Surface Vicinity inside the substrate material. Equivalent stress levels attain high values in the Vicinity of the Surface which, in turn, results in a plastic zone in this region.
S Z Shuja - One of the best experts on this subject based on the ideXlab platform.
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Flow into a hole in relation to laser drilling: influence of coating thickness
International Journal of Numerical Methods for Heat & Fluid Flow, 2014Co-Authors: S Z Shuja, Bekir Sami YilbasAbstract:Purpose – In laser drilling applications, hole wall remains almost the melting temperature of the substrate material and the thermodynamic pressure developed at high temperature molten Surface Vicinity influences the heat transfer rates and the skin friction at the Surface of the hole wall. This effect becomes complicated for the holes drilled in coated substrates. In this case, melting temperatures of the coating and base materials are different, which in turn modifies the flow field in the hole due to jet impingement. Consequently, investigation of the heat transfer rates from the hole wall Surfaces and the skin friction at the hole Surface becomes essential. The paper aims to discuss these issues. Design/methodology/approach – Numerical solution for jet impingement onto a hole with high wall temperature is introduced. Heat transfer rates and skin friction from the hole wall is predicted. The numerical model is validated with the experimental data reported in the open literature. Findings – The Nusselt ...
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Laser shortpulse heating–variable properties case
Physica A: Statistical Mechanics and its Applications, 2006Co-Authors: Bekir Sami Yilbas, S Z ShujaAbstract:Nonequilibrium energy transport in the Surface region of the solid substrate irradiated by a shortpulse laser beam results in high electron and low lattice site temperatures. The rise of electron temperature in the region irradiated by a laser beam depends on the thermophysical properties of the substrate material. The assumption of constant thermophysical properties results in excessive rise of electron temperature in the Surface Vicinity of the substrate material. Consequently, when modeling the laser shortpulse heating process, variable properties should be employed in the analysis. In the present study, laser shortpulse heating of copper is considered. Electron kinetic theory approach is introduced to model the nonequilibrium energy transport taking place in the Surface region of the substrate material. The resulting equation of energy transport is decoupled into two equations as similar to those in the two-equation model. The constant as well as variable properties of the substrate material are introduced in the simulations. It is found that the variable properties have significant effect on electron temperature distribution in the Surface Vicinity of the substrate material. This is more pronounced in the early heating period. The constant properties predict excessive electron temperature rise in the Surface Vicinity of the substrate material.
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Laser-shock processing of steel
Journal of Materials Processing Technology, 2003Co-Authors: Bekir Sami Yilbas, S Z Shuja, Abul Fazal M. Arif, Mohammed A. GondalAbstract:Abstract The laser induced shock hardening of metal Surfaces has several advantages over the conventional Surface hardening methods. In order to improve the shock hardening process, investigation into the physical processes involved is necessary. In the present study, the modeling of the laser pulsed heating process is considered and the closed form solution for the Surface temperature rise is obtained. The recoil pressure developed during the Surface ablation is formulated and the elastic–plastic wave generation due to impact loading of the Surface is analyzed. The Surface temperature profile, the magnitude of the recoil pressure, and the depth of resulting plastic region inside the substrate are predicted for mild and stainless steel workpieces. The study is extended to include experimental investigation of laser-shock processing. Nd:YAG laser is used to ablate the steel Surfaces. SEM, TEM, and EDS are carried out for metallurgical and morphological examinations of the laser ablated region. Microhardness measurement is carried out and the prediction of depth of plastic zone from the wave propagation analysis is validated. It is found that the recoil pressure in the order of 1 GPa is developed at the Surface. The dislocations are generated in the Surface Vicinity of the substrate after the laser ablation of the Surface due to the impact loading of the Surface by a recoil pressure. The plastic zone extends about 450 μm below the Surface and the predictions well agreed with the experimental findings.
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INVESTIGATION INTO THERMOELASTIC DISPLACEMENT OF SurfaceS SUBJECTED TO GAS ASSISTED LASER REPETITIVE PULSE HEATING
Surface Engineering, 2002Co-Authors: S Z Shuja, Bekir Sami Yilbas, Abul Fazal M. ArifAbstract:AbstractGas assisted laser repetitive pulse heating of metallic Surfaces finds wide application in industry. As the temperature inside the substrate material rises, thermal expansion of the irradiated region occurs. The monitoring of the Surface displacement is a potential candidate for measuring the Surface temperature during the laser heating process. In the present study, gas assisted laser repetitive pulse heating of steel is modelled. The strain in the Surface Vicinity and the thermoelastic displacement of the Surface are predicted for two pulse types. The correlation between the Surface temperature and the Surface displacement is explored. It is found that the Surface displacement follows the frequency of the temperature profiles; however, the rise and fall of the rates of the Surface displacement differ considerably from those of the temperature field. This is more pronounced for the repetitive pulses with long cooling periods. In addition, the spatial resolution of the Surface displacement differs...
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Electron kinetic theory approach for sub-nanosecond laser pulse heating
Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2000Co-Authors: Bekir Sami Yilbas, S Z ShujaAbstract:Laser short-pulse heating initiates non-equilibrium thermodynamic processes in the Surface Vicinity of solid substrates that are subjected to the pulse heating. The Fourier heating model, however, overestimates the temperature rise in this region. Consequently, it becomes essential to consider a heating model employing a microscopic level energy exchange mechanism in the Surface Vicinity. In the present study, electron kinetic theory, Fourier theory (one-equation model) and a two-equation model are introduced for sub-nanosecond laser heating pulses. The effect of laser pulse intensity on the temperature rise is also considered. The equations resulting from the models are solved numerically for gold and chromium substrates. The predictions are validated for a triangular pulse and a silicon substrate. It is found that electron kinetic theory and a two-equation model both predict lower temperatures in the Surface Vicinity at early heating times. As the pulse heating progresses, the predictions of both models converge to the result of a one-equation model.