The Experts below are selected from a list of 2262 Experts worldwide ranked by ideXlab platform
Maryse Muller - One of the best experts on this subject based on the ideXlab platform.
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Study on temperature dependence of Recoil Pressure near the boiling temperature - Towards better modeling simulation
International Congress on Applications of Lasers & Electro-Optics, 2012Co-Authors: Koji Hirano, Rémy Fabbro, Maryse MullerAbstract:Nowadays it is widely accepted that Recoil Pressure is an important driving force of molten material in various laser material processing. However, we do not fully understand the physical processes that occur around the liquid-gas interface during evaporation. Consequently, temperature dependence of the Recoil Pressure near the boiling temperature remains unclear, although this information is essential to perform numerical simulations of laser keyhole welding. In this study we experimentally estimated the temperature dependence of the Recoil Pressure of pure iron from combined measurements of melt surface deformation and melt surface temperature. Our results provide the first experimental evidence that the Recoil Pressure can drive molten material only when the surface temperature exceeds the boiling temperature. This result indicates that a proper consideration of the ambient atmospheric Pressure is indispensable to analyze hydrodynamics of molten material either analytically or numerically.Nowadays it is widely accepted that Recoil Pressure is an important driving force of molten material in various laser material processing. However, we do not fully understand the physical processes that occur around the liquid-gas interface during evaporation. Consequently, temperature dependence of the Recoil Pressure near the boiling temperature remains unclear, although this information is essential to perform numerical simulations of laser keyhole welding. In this study we experimentally estimated the temperature dependence of the Recoil Pressure of pure iron from combined measurements of melt surface deformation and melt surface temperature. Our results provide the first experimental evidence that the Recoil Pressure can drive molten material only when the surface temperature exceeds the boiling temperature. This result indicates that a proper consideration of the ambient atmospheric Pressure is indispensable to analyze hydrodynamics of molten material either analytically or numerically.
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experimental determination of temperature threshold for melt surface deformation during laser interaction on iron at atmospheric Pressure
Journal of Physics D, 2011Co-Authors: Koji Hirano, Rémy Fabbro, Maryse MullerAbstract:Recoil Pressure is the principal driving force of molten metal in laser processing in the intensity range 10−1–102 MW cm−2. It is thus essential to estimate the Recoil Pressure in order to describe physical processes or to carry out numerical simulations. However, there exists no quantitative estimation of the Recoil Pressure near the boiling temperature (Tv), which is particularly important in the welding process. In this study we experimentally investigated the Recoil Pressure of pure iron around Tv. The main interest was to determine the threshold surface temperature to start deformation of melt surface. Using camera-based temperature measurement with accurate evaluation of emissivity from experiment, it was shown that the surface temperature has to reach Tv to initiate the melt surface deformation. This result provides the first experimental evidence for the frequently used assumption that a deep keyhole welding requires surface temperature over Tv. It is indicated also that, in normal gas-assisted laser cutting process, the Recoil Pressure hardly contributes to material ejection when the surface temperature is lower than Tv, as opposed to the commonly believed presumption.
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Experimental determination of temperature threshold for melt surface deformation during laser interaction on iron at atmospheric Pressure
Journal of Physics D: Applied Physics, 2011Co-Authors: Koji Hirano, Rémy Fabbro, Maryse MullerAbstract:Recoil Pressure is the principal driving force of molten metal in laser processing in the intensity range of 10^-1 ~ 10^2 MW/cm2. It is thus essential to estimate the Recoil Pressure in order to describe physical processes or to carry out numerical simulations. However, there exists no quantitative estimation of the Recoil Pressure near the boiling temperature (Tv), which is particularly important in welding process. In this study we experimentally investigated the Recoil Pressure of pure iron around Tv. The main interest was to determine the threshold surface temperature to start deformation of melt surface. Using camera-based temperature measurement with accurate evaluation of emissivity from experiment, it was shown that the surface temperature has to reach Tv to initiate the melt surface deformation. This result provides the first experimental evidence for the frequently used assumption that a deep keyhole welding requires surface temperature over Tv. It is indicated also that, in normal gas-assisted laser cutting process, the Recoil Pressure hardly contributes to material ejection when the surface temperature is lower than Tv, as opposed to commonly believed presumption.
Koji Hirano - One of the best experts on this subject based on the ideXlab platform.
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Study on temperature dependence of Recoil Pressure near the boiling temperature - Towards better modeling simulation
International Congress on Applications of Lasers & Electro-Optics, 2012Co-Authors: Koji Hirano, Rémy Fabbro, Maryse MullerAbstract:Nowadays it is widely accepted that Recoil Pressure is an important driving force of molten material in various laser material processing. However, we do not fully understand the physical processes that occur around the liquid-gas interface during evaporation. Consequently, temperature dependence of the Recoil Pressure near the boiling temperature remains unclear, although this information is essential to perform numerical simulations of laser keyhole welding. In this study we experimentally estimated the temperature dependence of the Recoil Pressure of pure iron from combined measurements of melt surface deformation and melt surface temperature. Our results provide the first experimental evidence that the Recoil Pressure can drive molten material only when the surface temperature exceeds the boiling temperature. This result indicates that a proper consideration of the ambient atmospheric Pressure is indispensable to analyze hydrodynamics of molten material either analytically or numerically.Nowadays it is widely accepted that Recoil Pressure is an important driving force of molten material in various laser material processing. However, we do not fully understand the physical processes that occur around the liquid-gas interface during evaporation. Consequently, temperature dependence of the Recoil Pressure near the boiling temperature remains unclear, although this information is essential to perform numerical simulations of laser keyhole welding. In this study we experimentally estimated the temperature dependence of the Recoil Pressure of pure iron from combined measurements of melt surface deformation and melt surface temperature. Our results provide the first experimental evidence that the Recoil Pressure can drive molten material only when the surface temperature exceeds the boiling temperature. This result indicates that a proper consideration of the ambient atmospheric Pressure is indispensable to analyze hydrodynamics of molten material either analytically or numerically.
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Modeling keyhole and weld pool dynamics of laser welding under variable ambient Pressure
International Congress on Applications of Lasers & Electro-Optics, 2012Co-Authors: Shengyong Pang, Koji Hirano, Rémy Fabbro, Tao JiangAbstract:It is widely accepted that evaporation induced Recoil Pressure plays critical roles in keyhole and weld pool dynamics during laser welding. Recent experiments by some of the authors have demonstrated that the partial Pressure of surrounding gas could also contribute an important role to the dynamics of evaporation surface during laser welding under atmospheric Pressure. However, most of mathematical models of keyhole and weld pool behaviours of laser welding did not include the effect of ambient Pressure. In this study, we formulate a new mathematical model of Recoil Pressure which considering the effect of ambient gas Pressure and adopt it to theoretically investigate keyhole and weld pool behaviours in laser welding under different ambient Pressure, based on HUST’s comprehensive transient keyhole welding simulation code. Preliminary theoretical comparisons of three dimensional transient keyhole and weld pool behaviours during laser welding under variable ambient Pressure are discussed. Some interesting phenomena which correspond well to recent experimental results are found. This research provides some theoretical backgrounds for applications of laser welding under different atmospheric Pressure.It is widely accepted that evaporation induced Recoil Pressure plays critical roles in keyhole and weld pool dynamics during laser welding. Recent experiments by some of the authors have demonstrated that the partial Pressure of surrounding gas could also contribute an important role to the dynamics of evaporation surface during laser welding under atmospheric Pressure. However, most of mathematical models of keyhole and weld pool behaviours of laser welding did not include the effect of ambient Pressure. In this study, we formulate a new mathematical model of Recoil Pressure which considering the effect of ambient gas Pressure and adopt it to theoretically investigate keyhole and weld pool behaviours in laser welding under different ambient Pressure, based on HUST’s comprehensive transient keyhole welding simulation code. Preliminary theoretical comparisons of three dimensional transient keyhole and weld pool behaviours during laser welding under variable ambient Pressure are discussed. Some interesting ...
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experimental determination of temperature threshold for melt surface deformation during laser interaction on iron at atmospheric Pressure
Journal of Physics D, 2011Co-Authors: Koji Hirano, Rémy Fabbro, Maryse MullerAbstract:Recoil Pressure is the principal driving force of molten metal in laser processing in the intensity range 10−1–102 MW cm−2. It is thus essential to estimate the Recoil Pressure in order to describe physical processes or to carry out numerical simulations. However, there exists no quantitative estimation of the Recoil Pressure near the boiling temperature (Tv), which is particularly important in the welding process. In this study we experimentally investigated the Recoil Pressure of pure iron around Tv. The main interest was to determine the threshold surface temperature to start deformation of melt surface. Using camera-based temperature measurement with accurate evaluation of emissivity from experiment, it was shown that the surface temperature has to reach Tv to initiate the melt surface deformation. This result provides the first experimental evidence for the frequently used assumption that a deep keyhole welding requires surface temperature over Tv. It is indicated also that, in normal gas-assisted laser cutting process, the Recoil Pressure hardly contributes to material ejection when the surface temperature is lower than Tv, as opposed to the commonly believed presumption.
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Experimental determination of temperature threshold for melt surface deformation during laser interaction on iron at atmospheric Pressure
Journal of Physics D: Applied Physics, 2011Co-Authors: Koji Hirano, Rémy Fabbro, Maryse MullerAbstract:Recoil Pressure is the principal driving force of molten metal in laser processing in the intensity range of 10^-1 ~ 10^2 MW/cm2. It is thus essential to estimate the Recoil Pressure in order to describe physical processes or to carry out numerical simulations. However, there exists no quantitative estimation of the Recoil Pressure near the boiling temperature (Tv), which is particularly important in welding process. In this study we experimentally investigated the Recoil Pressure of pure iron around Tv. The main interest was to determine the threshold surface temperature to start deformation of melt surface. Using camera-based temperature measurement with accurate evaluation of emissivity from experiment, it was shown that the surface temperature has to reach Tv to initiate the melt surface deformation. This result provides the first experimental evidence for the frequently used assumption that a deep keyhole welding requires surface temperature over Tv. It is indicated also that, in normal gas-assisted laser cutting process, the Recoil Pressure hardly contributes to material ejection when the surface temperature is lower than Tv, as opposed to commonly believed presumption.
Rémy Fabbro - One of the best experts on this subject based on the ideXlab platform.
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Study on temperature dependence of Recoil Pressure near the boiling temperature - Towards better modeling simulation
International Congress on Applications of Lasers & Electro-Optics, 2012Co-Authors: Koji Hirano, Rémy Fabbro, Maryse MullerAbstract:Nowadays it is widely accepted that Recoil Pressure is an important driving force of molten material in various laser material processing. However, we do not fully understand the physical processes that occur around the liquid-gas interface during evaporation. Consequently, temperature dependence of the Recoil Pressure near the boiling temperature remains unclear, although this information is essential to perform numerical simulations of laser keyhole welding. In this study we experimentally estimated the temperature dependence of the Recoil Pressure of pure iron from combined measurements of melt surface deformation and melt surface temperature. Our results provide the first experimental evidence that the Recoil Pressure can drive molten material only when the surface temperature exceeds the boiling temperature. This result indicates that a proper consideration of the ambient atmospheric Pressure is indispensable to analyze hydrodynamics of molten material either analytically or numerically.Nowadays it is widely accepted that Recoil Pressure is an important driving force of molten material in various laser material processing. However, we do not fully understand the physical processes that occur around the liquid-gas interface during evaporation. Consequently, temperature dependence of the Recoil Pressure near the boiling temperature remains unclear, although this information is essential to perform numerical simulations of laser keyhole welding. In this study we experimentally estimated the temperature dependence of the Recoil Pressure of pure iron from combined measurements of melt surface deformation and melt surface temperature. Our results provide the first experimental evidence that the Recoil Pressure can drive molten material only when the surface temperature exceeds the boiling temperature. This result indicates that a proper consideration of the ambient atmospheric Pressure is indispensable to analyze hydrodynamics of molten material either analytically or numerically.
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Modeling keyhole and weld pool dynamics of laser welding under variable ambient Pressure
International Congress on Applications of Lasers & Electro-Optics, 2012Co-Authors: Shengyong Pang, Koji Hirano, Rémy Fabbro, Tao JiangAbstract:It is widely accepted that evaporation induced Recoil Pressure plays critical roles in keyhole and weld pool dynamics during laser welding. Recent experiments by some of the authors have demonstrated that the partial Pressure of surrounding gas could also contribute an important role to the dynamics of evaporation surface during laser welding under atmospheric Pressure. However, most of mathematical models of keyhole and weld pool behaviours of laser welding did not include the effect of ambient Pressure. In this study, we formulate a new mathematical model of Recoil Pressure which considering the effect of ambient gas Pressure and adopt it to theoretically investigate keyhole and weld pool behaviours in laser welding under different ambient Pressure, based on HUST’s comprehensive transient keyhole welding simulation code. Preliminary theoretical comparisons of three dimensional transient keyhole and weld pool behaviours during laser welding under variable ambient Pressure are discussed. Some interesting phenomena which correspond well to recent experimental results are found. This research provides some theoretical backgrounds for applications of laser welding under different atmospheric Pressure.It is widely accepted that evaporation induced Recoil Pressure plays critical roles in keyhole and weld pool dynamics during laser welding. Recent experiments by some of the authors have demonstrated that the partial Pressure of surrounding gas could also contribute an important role to the dynamics of evaporation surface during laser welding under atmospheric Pressure. However, most of mathematical models of keyhole and weld pool behaviours of laser welding did not include the effect of ambient Pressure. In this study, we formulate a new mathematical model of Recoil Pressure which considering the effect of ambient gas Pressure and adopt it to theoretically investigate keyhole and weld pool behaviours in laser welding under different ambient Pressure, based on HUST’s comprehensive transient keyhole welding simulation code. Preliminary theoretical comparisons of three dimensional transient keyhole and weld pool behaviours during laser welding under variable ambient Pressure are discussed. Some interesting ...
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experimental determination of temperature threshold for melt surface deformation during laser interaction on iron at atmospheric Pressure
Journal of Physics D, 2011Co-Authors: Koji Hirano, Rémy Fabbro, Maryse MullerAbstract:Recoil Pressure is the principal driving force of molten metal in laser processing in the intensity range 10−1–102 MW cm−2. It is thus essential to estimate the Recoil Pressure in order to describe physical processes or to carry out numerical simulations. However, there exists no quantitative estimation of the Recoil Pressure near the boiling temperature (Tv), which is particularly important in the welding process. In this study we experimentally investigated the Recoil Pressure of pure iron around Tv. The main interest was to determine the threshold surface temperature to start deformation of melt surface. Using camera-based temperature measurement with accurate evaluation of emissivity from experiment, it was shown that the surface temperature has to reach Tv to initiate the melt surface deformation. This result provides the first experimental evidence for the frequently used assumption that a deep keyhole welding requires surface temperature over Tv. It is indicated also that, in normal gas-assisted laser cutting process, the Recoil Pressure hardly contributes to material ejection when the surface temperature is lower than Tv, as opposed to the commonly believed presumption.
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Experimental determination of temperature threshold for melt surface deformation during laser interaction on iron at atmospheric Pressure
Journal of Physics D: Applied Physics, 2011Co-Authors: Koji Hirano, Rémy Fabbro, Maryse MullerAbstract:Recoil Pressure is the principal driving force of molten metal in laser processing in the intensity range of 10^-1 ~ 10^2 MW/cm2. It is thus essential to estimate the Recoil Pressure in order to describe physical processes or to carry out numerical simulations. However, there exists no quantitative estimation of the Recoil Pressure near the boiling temperature (Tv), which is particularly important in welding process. In this study we experimentally investigated the Recoil Pressure of pure iron around Tv. The main interest was to determine the threshold surface temperature to start deformation of melt surface. Using camera-based temperature measurement with accurate evaluation of emissivity from experiment, it was shown that the surface temperature has to reach Tv to initiate the melt surface deformation. This result provides the first experimental evidence for the frequently used assumption that a deep keyhole welding requires surface temperature over Tv. It is indicated also that, in normal gas-assisted laser cutting process, the Recoil Pressure hardly contributes to material ejection when the surface temperature is lower than Tv, as opposed to commonly believed presumption.
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Modeling of humps formation during deep-penetration laser welding
Applied Physics A, 2010Co-Authors: El Hachemi Amara, Rémy FabbroAbstract:A 3-D transient modeling based on the numerical resolution of the fluid flow ant the heat transfer equations is developed for deep-penetration laser welding at high-welding speed regime, which results in the humping phenomenon. The physical mechanisms included in our model concern matter melting, vaporization inducing a Recoil Pressure, and resolidification. The implementation of developed procedures called User Defined Functions (UDFs) working interactively with the CFD Fluent code and a dynamic mesh method allowed us to treat the problem with specific and complex boundary conditions. The Recoil Pressure, fusion, resolidification, and the temperature dependence of the physical properties were thus taken into account. As a result, regular humps could be observed after resolidification on the weld seam.
Mohammed A. Gondal - One of the best experts on this subject based on the ideXlab platform.
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Plastic Deformation of Steel Surface Due to Laser Shock Processing
Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2006Co-Authors: Bekir Sami Yilbas, Abul Fazal M. Arif, Mohammed A. GondalAbstract:AbstractLaser shock processing improves the properties of metallic surfaces, such as microhardness, through increased dislocation density. In the present study, laser shock processing of steel surfaces is considered. The Recoil Pressure developed across the vapour-solid interface is formulated and the temporal and spatial distributions of Recoil Pressure are computed. The stress wave generated owing to impacting force of Recoil Pressure and the plastic deformation in the substrate materials are computed. An experiment, in which an Nd:YAG laser is employed to irradiate the workpiece surface, is conducted to compare the predictions. Morphological and metallurgical changes in the laserprocessed regions are examined using scanning electron microscopy and transmission electron microscopy. It is found that the hardness of surfaces improved considerably after the shock processing owing to enhanced dislocation sites in the surface region of the substrate material. The predicted Recoil Pressure agreed well with th...
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Investigation into laser shock processing
Journal of Materials Engineering and Performance, 2004Co-Authors: B.s. Yilbas, Mohammed A. Gondal, S.z. Shuja, A. F. M. Arif, J. ShirokofAbstract:Laser shock processing is a good candidate for surface industry due to its rapid processing, localized ablation, and precision of operation. In the current study, laser shock processing of steel was considered. The numerical solutions for temperature rise and Recoil Pressure development across the interface of the ablating front and solid are presented. The propagation of elastic-plastic waves in the solid due to Recoil Pressure loading at the surface is analyzed and numerical solution for the wave propagation was obtained. An experiment was conducted to ablate the steel surfaces for shock processing. Scanning electron microscopy was carried out to examine the ablated surfaces shock processing while transmission electron microscopy was conducted to obtain dislocation densities after the shock processing. It was found that surface hardness of the workpiece increased in the order of 1.8 times of the base material hardness, and the dislocation was the main source of the shock hardening in the region affected by laser shock processing.
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Laser-shock processing of steel
Journal of Materials Processing Technology, 2003Co-Authors: 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.
Bekir Sami Yilbas - One of the best experts on this subject based on the ideXlab platform.
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Flexural Motion Due to Laser Heating Applications
Materials Forming Machining and Tribology, 2014Co-Authors: Bekir Sami Yilbas, Iyad Al-zaharnah, Ahmet Z. SahinAbstract:Laser evaporative heating of solid surfaces involves phase change process and Recoil Pressure generation in between the vapor and liquid phases. Recoil Pressure remains high during a short period of time, which in turn causes mechanical vibration of the body irradiated by a laser beam. When the body resembles a cantilever arrangement and if the laser radiation takes place at the free end of the cantilever beam, the body undergoes a flexural motion. Depending on the laser pulse intensity and duration, the displacement characteristics of the cantilever beam provide information on the mechanical properties of the irradiated beam. In this chapter, laser pulse heating is formulated and thermal stress developed in the heated region is analyzed. In addition, flexural behavior of the cantilever beam is presented in detail.
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Laser evaporative heating of surface: simulation of flow field in the laser produced cavity
Journal of Physics D: Applied Physics, 2006Co-Authors: Bekir Sami Yilbas, S B MansoorAbstract:Laser heating of steel surface is considered and phase change process during laser heating pulse is simulated. A two-dimensional axisymmetric heating situation is considered when modelling the physical processes involved. The flow field generated in the cavity due to an evaporating front is modelled numerically using a control volume approach. Recoil Pressure developed in the cavity is computed. A turbulence model is accommodated to account for the turbulence in the evaporating vapour front. It is found that the size of the mushy zone across the liquid–solid interface is smaller than that corresponding to the vapour–liquid interface. The evaporating front emanating from the cavity generates a complex flow structure in the cavity, in which case, high velocity expanding jet is developed in the region close to the cavity wall. Recoil Pressure attains high values in the early heating periods due to rapid evaporation of the cavity surface.
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Plastic Deformation of Steel Surface Due to Laser Shock Processing
Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture, 2006Co-Authors: Bekir Sami Yilbas, Abul Fazal M. Arif, Mohammed A. GondalAbstract:AbstractLaser shock processing improves the properties of metallic surfaces, such as microhardness, through increased dislocation density. In the present study, laser shock processing of steel surfaces is considered. The Recoil Pressure developed across the vapour-solid interface is formulated and the temporal and spatial distributions of Recoil Pressure are computed. The stress wave generated owing to impacting force of Recoil Pressure and the plastic deformation in the substrate materials are computed. An experiment, in which an Nd:YAG laser is employed to irradiate the workpiece surface, is conducted to compare the predictions. Morphological and metallurgical changes in the laserprocessed regions are examined using scanning electron microscopy and transmission electron microscopy. It is found that the hardness of surfaces improved considerably after the shock processing owing to enhanced dislocation sites in the surface region of the substrate material. The predicted Recoil Pressure agreed well with th...
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Laser pulse heating and flexural wave generation during treatment of metallic surfaces
Journal of Materials Processing Technology, 2003Co-Authors: Bekir Sami Yilbas, S.j. HyderAbstract:Abstract Non-conduction limited laser heating of metallic surfaces results in evaporation of the surface. This, in turn, generates a Recoil Pressure across the interface between the melted and evaporated zones. Depending upon the magnitude of the Recoil Pressure, a Pressure force normal to the workpiece surface is resulted. This causes the generation of flexural waves. In the present study, closed form solution for surface temperature rise during a laser heating pulse is presented and resulting Recoil Pressure is formulated using a momentum balance across the vapor–liquid interface at the workpiece surface. The flexural wave analysis due to Pressure force is carried out for different workpiece geometric configurations. It is found that the peak value of the Recoil Pressure predicted agrees well with the previous findings and the flexural wave with amplitude of 20 μm at the workpiece center is generated. Moreover, the frequency and amplitude of flexural wave vary with workpiece geometric configuration; in this case, both ends fixed workpiece results in fast rate of damping of flexural wave amplitude.