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Xinwei Wang - One of the best experts on this subject based on the ideXlab platform.

  • phase change and stress wave in picosecond laser Material Interaction with shock wave formation
    Applied Physics A, 2013
    Co-Authors: Jingchao Zhang, Xinwei Wang
    Abstract:

    When background gas is present in pulsed laser–Material Interaction, a shock wave down to the nanoscale will emerge. The background gas will affect the phase change and explosion in the target. This study is focused on the void dynamics and stress wave in a model Material (argon crystal) under picosecond pulsed laser irradiation. Our results show that existence of ambient gas and the shock wave significantly suppresses the void formation and their lifetime. Void dynamics, including their growing rate, lifetime, and size under the influence of ambient gas are studied in detail. All the voids undergo an accelerating and decelerating process in the growth. The collapsing process is almost symmetrical to the growing process. Higher laser fluence is found to induce an obvious foamy structure. Stress wave formation and propagation, temperature contour, and target and gas atom number densities are studied to reveal the underlying physical processes. Although the Interaction of the plume with ambient gas significantly suppresses the void formation and phase explosion, no obvious effect is found on the stress wave within the target. Very interestingly, secondary stress waves resulting from re-deposition of ablated atoms and void collapse are observed, although their magnitude is much smaller than the directly laser-induced stress wave.

  • Phase change and stress wave in picosecond laser–Material Interaction with shock wave formation
    Applied Physics A, 2013
    Co-Authors: Jingchao Zhang, Xinwei Wang
    Abstract:

    When background gas is present in pulsed laser–Material Interaction, a shock wave down to the nanoscale will emerge. The background gas will affect the phase change and explosion in the target. This study is focused on the void dynamics and stress wave in a model Material (argon crystal) under picosecond pulsed laser irradiation. Our results show that existence of ambient gas and the shock wave significantly suppresses the void formation and their lifetime. Void dynamics, including their growing rate, lifetime, and size under the influence of ambient gas are studied in detail. All the voids undergo an accelerating and decelerating process in the growth. The collapsing process is almost symmetrical to the growing process. Higher laser fluence is found to induce an obvious foamy structure. Stress wave formation and propagation, temperature contour, and target and gas atom number densities are studied to reveal the underlying physical processes. Although the Interaction of the plume with ambient gas significantly suppresses the void formation and phase explosion, no obvious effect is found on the stress wave within the target. Very interestingly, secondary stress waves resulting from re-deposition of ablated atoms and void collapse are observed, although their magnitude is much smaller than the directly laser-induced stress wave.

  • Hybrid Atomistic-macroscale Modeling of Long-time Material Behavior in Nanosecond Laser-Material Interaction
    International Photonics and Optoelectronics Meetings, 2012
    Co-Authors: Lijun Zhang, Xinwei Wang
    Abstract:

    The thermo-physical properties and fundamental mechanism of laser ablation process in nanosecond laser-Material Interaction are investigated in a computational study combining molecular dynamics simulations.

  • plume splitting in pico second laser Material Interaction under the influence of shock wave
    Physics Letters A, 2009
    Co-Authors: Sobieslaw Gacek, Xinwei Wang
    Abstract:

    Abstract In this work, molecular dynamics simulations are conducted to study the physics of plume splitting in pico-second laser Material Interaction in background gas. The velocity distribution shows a clear split into two distinctive components. Detailed atom trajectory track reveals the behavior of atoms within the peaks and uncovers the mechanisms of peak formation. The observed plume velocity splitting emerges from two distinguished parts of the plume. The front peak of the plume is from the faster moving atoms and smaller particles during laser–Material ablation. This region experiences strong constraint from the ambient gas and has substantial velocity attenuation. The second (rear) peak of the plume velocity originates from the larger and slower clusters in laser-Material ablation. These larger clusters/particles experience very little constraint from the background, but are affected by the relaxation dynamics of plume and appear almost as a standing wave during the evolution. Density splitting only appears at the beginning of laser–Material ablation and quickly disappears due to spread-out of the slower moving clusters. It is found that higher ambient pressure and stronger laser fluence favor earlier plume splitting.

  • Plume splitting in pico-second laser–Material Interaction under the influence of shock wave
    Physics Letters A, 2009
    Co-Authors: Sobieslaw Gacek, Xinwei Wang
    Abstract:

    Abstract In this work, molecular dynamics simulations are conducted to study the physics of plume splitting in pico-second laser Material Interaction in background gas. The velocity distribution shows a clear split into two distinctive components. Detailed atom trajectory track reveals the behavior of atoms within the peaks and uncovers the mechanisms of peak formation. The observed plume velocity splitting emerges from two distinguished parts of the plume. The front peak of the plume is from the faster moving atoms and smaller particles during laser–Material ablation. This region experiences strong constraint from the ambient gas and has substantial velocity attenuation. The second (rear) peak of the plume velocity originates from the larger and slower clusters in laser-Material ablation. These larger clusters/particles experience very little constraint from the background, but are affected by the relaxation dynamics of plume and appear almost as a standing wave during the evolution. Density splitting only appears at the beginning of laser–Material ablation and quickly disappears due to spread-out of the slower moving clusters. It is found that higher ambient pressure and stronger laser fluence favor earlier plume splitting.

Lijun Zhang - One of the best experts on this subject based on the ideXlab platform.

  • Hybrid Atomistic-macroscale Modeling of Long-time Material Behavior in Nanosecond Laser-Material Interaction
    International Photonics and Optoelectronics Meetings, 2012
    Co-Authors: Lijun Zhang, Xinwei Wang
    Abstract:

    The thermo-physical properties and fundamental mechanism of laser ablation process in nanosecond laser-Material Interaction are investigated in a computational study combining molecular dynamics simulations.

  • hybrid atomistic macroscale modeling of long time phase change in nanosecond laser Material Interaction
    Applied Surface Science, 2008
    Co-Authors: Lijun Zhang, Xinwei Wang
    Abstract:

    Abstract In this work, large-scale hybrid atomistic-macroscale simulation is performed to study the long-time Material behavior in nanosecond laser–Material Interaction. Different phase change phenomena are studied, including solid–liquid interface speed, temperature, maximum melting depth, and ablation rate. Full solidification/epitaxial re-growth is observed within 60 ns for the laser fluence of 5 J/m2. Strong fluctuation is observed at the solid–liquid interface and surface of the molten pool. No visible super-heating is observed at the solid–liquid interface. For the laser fluences studied in this work, an almost linear relationship is observed between the ablation yield and the laser fluence, indicating weak phase explosion.

  • Dynamic Structure and Mass Penetration of Shock Wave in Picosecond Laser-Material Interaction
    Japanese Journal of Applied Physics, 2008
    Co-Authors: Lijun Zhang, Xinwei Wang
    Abstract:

    This work pioneers the atomistic modeling of the shock wave in background gas in picosecond laser-Material Interaction. It is found in the shock wave the compressed ambient gas region has a very uniform temperature distribution while the temperature decreases from the front of the plume to its end. The group velocity of atoms in the shock wave front is much smaller than the shock wave propagation speed and experiences a fast decay due to momentum exchange with the ambient gas. Strong decay of the shock wave front temperature and pressure is observed while its density features much slower attenuation. An effective mass penetration length is designed to quantitatively evaluate the mutual mass penetration between the plume and background gas. This effective mixing length grows at a rate of ~60 m/s. This fast mixing/mass penetration is largely due to the strong relative movement between the plume and the background gas. The molecular dynamics results agree well with the analytical solution in terms of relating various shock wave strengths.

  • Hybrid atomistic-macroscale modeling of long-time phase change in nanosecond laser–Material Interaction
    Applied Surface Science, 2008
    Co-Authors: Lijun Zhang, Xinwei Wang
    Abstract:

    Abstract In this work, large-scale hybrid atomistic-macroscale simulation is performed to study the long-time Material behavior in nanosecond laser–Material Interaction. Different phase change phenomena are studied, including solid–liquid interface speed, temperature, maximum melting depth, and ablation rate. Full solidification/epitaxial re-growth is observed within 60 ns for the laser fluence of 5 J/m2. Strong fluctuation is observed at the solid–liquid interface and surface of the molten pool. No visible super-heating is observed at the solid–liquid interface. For the laser fluences studied in this work, an almost linear relationship is observed between the ablation yield and the laser fluence, indicating weak phase explosion.

  • Shock Waves in Pulsed Laser Material Interaction: Internal Structure and Mass Penetration
    ASME 2008 First International Conference on Micro Nanoscale Heat Transfer Parts A and B, 2008
    Co-Authors: Lijun Zhang, Xinwei Wang
    Abstract:

    This work pioneers the atomistic modeling of the shock wave in picosecond laser-Material Interaction by simulating the Material that is irradiated with a picosecond laser pulse (11.3 ps FWHM) in a 0.25 MPa background gas. The dynamic structure and mutual mass penetration between the plume and background gas are investigated in detail. In the shock wave the compressed ambient gas region has a very uniform temperature distribution while the temperature decreases from the front of the plume to its end. The group velocity of atoms in the shock wave front is much smaller than the shock wave propagation speed and experiences a fast decay due to momentum exchange with the ambient gas. Strong decay of the shock wave front temperature and pressure is observed while its density features much slower attenuation. An effective mixing length is designed to quantitatively evaluate the mutual mass penetration between the plume and background gas. This effective mixing length grows at a rate of ∼ 60 m/s. This fast mixing/mass penetration is largely due to the strong relative movement between the plume and the background gas. The MD results agree well with the analytical solution in terms of relating various shock wave strengths.Copyright © 2008 by ASME

Sobieslaw Gacek - One of the best experts on this subject based on the ideXlab platform.

  • plume splitting in pico second laser Material Interaction under the influence of shock wave
    Physics Letters A, 2009
    Co-Authors: Sobieslaw Gacek, Xinwei Wang
    Abstract:

    Abstract In this work, molecular dynamics simulations are conducted to study the physics of plume splitting in pico-second laser Material Interaction in background gas. The velocity distribution shows a clear split into two distinctive components. Detailed atom trajectory track reveals the behavior of atoms within the peaks and uncovers the mechanisms of peak formation. The observed plume velocity splitting emerges from two distinguished parts of the plume. The front peak of the plume is from the faster moving atoms and smaller particles during laser–Material ablation. This region experiences strong constraint from the ambient gas and has substantial velocity attenuation. The second (rear) peak of the plume velocity originates from the larger and slower clusters in laser-Material ablation. These larger clusters/particles experience very little constraint from the background, but are affected by the relaxation dynamics of plume and appear almost as a standing wave during the evolution. Density splitting only appears at the beginning of laser–Material ablation and quickly disappears due to spread-out of the slower moving clusters. It is found that higher ambient pressure and stronger laser fluence favor earlier plume splitting.

  • Plume splitting in pico-second laser–Material Interaction under the influence of shock wave
    Physics Letters A, 2009
    Co-Authors: Sobieslaw Gacek, Xinwei Wang
    Abstract:

    Abstract In this work, molecular dynamics simulations are conducted to study the physics of plume splitting in pico-second laser Material Interaction in background gas. The velocity distribution shows a clear split into two distinctive components. Detailed atom trajectory track reveals the behavior of atoms within the peaks and uncovers the mechanisms of peak formation. The observed plume velocity splitting emerges from two distinguished parts of the plume. The front peak of the plume is from the faster moving atoms and smaller particles during laser–Material ablation. This region experiences strong constraint from the ambient gas and has substantial velocity attenuation. The second (rear) peak of the plume velocity originates from the larger and slower clusters in laser-Material ablation. These larger clusters/particles experience very little constraint from the background, but are affected by the relaxation dynamics of plume and appear almost as a standing wave during the evolution. Density splitting only appears at the beginning of laser–Material ablation and quickly disappears due to spread-out of the slower moving clusters. It is found that higher ambient pressure and stronger laser fluence favor earlier plume splitting.

  • Secondary shock wave in laser-Material Interaction
    Journal of Applied Physics, 2008
    Co-Authors: Sobieslaw Gacek, Xinwei Wang
    Abstract:

    In this work, the effects of shock driven process of the laser-ablated argon plume in a background gas environment are explored via molecular dynamics simulations. The primary shock wave propagation and its influence on the backward motion of the target Material are delineated. It is observed that the strong pressure gradient inside the main shock wave overcomes the forward momentum of the plume and some compressed gas, leading to backward movement and redeposition on the target surface. Reflection of the backward moving gas on the target surface results in the secondary shock wave. Detailed investigation of the secondary shock wave phenomenon is provided, which gives, for the first time, an insight into formation and evolution of the internal gaseous shock at the atomistic level.

  • Dynamics evolution of shock waves in laser–Material Interaction
    Applied Physics A, 2008
    Co-Authors: Sobieslaw Gacek, Xinwei Wang
    Abstract:

    In this work, the dynamics and internal structure of shock waves in picosecond laser–Material Interaction are explored at the atomistic level. The pressure of the shock wave, its propagation, and Interaction zone thickness between the plume and ambience are evaluated to study the effect of the laser absorption depth, ambient pressure, and laser fluence. Sound agreement is observed between the MD simulation and theoretical prediction of shock wave propagation and mass velocity. Due to the strong constraint from the compressed ambient gas, it is observed that the ablated plume could stop moving forward and mix with the ambient gas, or move backward to the target surface, leading to surface redeposition. Under smaller laser absorption depth, lower ambient pressure, or higher laser fluence, the shock wave will propagate faster and have a thicker Interaction zone between the target and ambient gas.

  • Dynamics Evolution of Shock Waves in Laser-Material Interaction
    2008 Second International Conference on Integration and Commercialization of Micro and Nanosystems, 2008
    Co-Authors: Sobieslaw Gacek, Xinwei Wang
    Abstract:

    In this work, the dynamics and internal structure of shock waves in picosecond laser–Material Interaction are explored at the atomistic level. The pressure of the shock wave, its propagation, and Interaction zone thickness between the plume and ambience are evaluated to study the effect of the laser absorption depth, ambient pressure, and laser fluence. Sound agreement is observed between the MD simulation and theoretical prediction of shock wave propagation and mass velocity. Due to the strong constraint from the compressed ambient gas, it is observed that the ablated plume could stop moving forward and mix with the ambient gas, or move backward to the target surface, leading to surface redeposition. Under smaller laser absorption depth, lower ambient pressure, or higher laser fluence, the shock wave will propagate faster and have a thicker Interaction zone between the target and ambient gas.

Sylvain Philippon - One of the best experts on this subject based on the ideXlab platform.

  • Numerical-experimental confrontation in the simulation of tool/abradable Material Interaction
    Journal of Engineering for Gas Turbines and Power, 2013
    Co-Authors: Alain Batailly, Mathias Legrand, Marion Cuny, Sylvain Philippon
    Abstract:

    In turbomachinery, depositing abradable coatings along the circumference of casings is recognized as a robust solution which combines the adjustment of operating clearances with the reduction of non-repairable damages potentially affecting the rotating blades. Accordingly, the modeling of the removal process experienced by these Materials is of growing industrial importance. Based on a numerical strategy detailed in a previous publication by the authors, the present study aims at describing the mechanical behavior of abradable coatings used within turbomachines in the context of translational high-speed Interactions with a rigid tool. The developed plastic constitutive law macroscopically capturing the abradable Material removal is first enriched to account for its strain rate dependence. Then, a sensitivity analysis with respect to a few parameters of interest is conducted and calibration of the numerical investigation with existing experimental data validates the proposed approach. Finally, the strain-rate dependence of the viscoplastic law implemented within a full numerical three-dimensional rotor/stator Interaction is addressed. Results reveal that viscoplastic terms have minor effects in turbomachinery Interactions.

Alain Batailly - One of the best experts on this subject based on the ideXlab platform.

  • Numerical-experimental confrontation in the simulation of tool/abradable Material Interaction
    Journal of Engineering for Gas Turbines and Power, 2013
    Co-Authors: Alain Batailly, Mathias Legrand, Marion Cuny, Sylvain Philippon
    Abstract:

    In turbomachinery, depositing abradable coatings along the circumference of casings is recognized as a robust solution which combines the adjustment of operating clearances with the reduction of non-repairable damages potentially affecting the rotating blades. Accordingly, the modeling of the removal process experienced by these Materials is of growing industrial importance. Based on a numerical strategy detailed in a previous publication by the authors, the present study aims at describing the mechanical behavior of abradable coatings used within turbomachines in the context of translational high-speed Interactions with a rigid tool. The developed plastic constitutive law macroscopically capturing the abradable Material removal is first enriched to account for its strain rate dependence. Then, a sensitivity analysis with respect to a few parameters of interest is conducted and calibration of the numerical investigation with existing experimental data validates the proposed approach. Finally, the strain-rate dependence of the viscoplastic law implemented within a full numerical three-dimensional rotor/stator Interaction is addressed. Results reveal that viscoplastic terms have minor effects in turbomachinery Interactions.

  • Numerical simulation of tool/abradable Material Interaction experiments
    Volume 5: Manufacturing Materials and Metallurgy; Marine; Microturbines and Small Turbomachinery; Supercritical CO2 Power Cycles, 2012
    Co-Authors: Alain Batailly, Marion Cuny, Mathias Legrand
    Abstract:

    Applying abradable coating on the casing of turbomachines has been widely recognized as a robust solution advantageously combining the adjustment of operating clearances with the reduction of potential non-repairable damages. Thus, the modeling of this Material is a growing field of investigation. Based on the numerical strategy proposed and detailed in previous publication by the same authors, the present study aims at capturing the mechanical behavior of abradable coating in the context of high speed Interaction with a rigid tool. The plastic law given is first enriched in order to take into account strain rate dependence. The sensitivity of the model regarding its main numerical parameters is assessed and highlights the role of each of these parameters. The calibration of numerical results with respect to experimental results lead to very satisfying results that confirm that the proposed strategy is well-suited for the modeling of abradable coating. Finally, the newly developped viscoplastic law is applied to a 3D rotor/stator Interaction case to determine the criticity of strain rate dependence in the case of blade/casing contact.Copyright © 2012 by ASME

  • Numerical simulation of tool/abradable Material Interaction experiments
    2012
    Co-Authors: Alain Batailly, Marion Cuny, Mathias Legrand
    Abstract:

    Applying abradable coating on the casing of turbomachines has been widely recognized as a robust solution advantageously combining the adjustment of operating clearances with the reduction of potential non-repairable damages. Thus, the modeling of this Material is a growing field of investigation. Based on the numerical strategy proposed and detailed in previous publication by the same authors, the present study aims at capturing the mechanical behavior of abradable coating in the context of high speed Interaction with a rigid tool. The plastic law given is first enriched in order to take into account strain rate dependence. The sensitivity of the model regarding its main numerical parameters is assessed and highlights the role of each of these parameters. The calibration of numerical results with respect to experimental results lead to very satisfying results that confirm that the proposed strategy is well-suited for the modeling of abradable coating. Finally, the newly developped viscoplastic law is applied to a 3D rotor/stator Interaction case to determine the criticity of strain rate dependence in the case of blade/casing contact.