The Experts below are selected from a list of 4449 Experts worldwide ranked by ideXlab platform
Erwan Verron - One of the best experts on this subject based on the ideXlab platform.
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Fatigue damage in carbon black filled natural rubber under uni- and multiaxial loading conditions
International Journal of Fatigue, 2013Co-Authors: Jean-benoit Le Cam, Bertrand Huneau, Erwan VerronAbstract:This paper deals with fatigue damage in carbon black filled natural rubber under uni- and multiaxial loading conditions. Fatigue damage is described at both the macroscopic (mechanical) scale and the microscopic (material) scale. The different fatigue damages observed at the macroscopic scale are presented according to the prescribed loading conditions. At this scale, five elementary fatigue damage patterns are defined, three correspond to external macroscopic cracks and two correspond to internal macroscopic cracks. These elementary fatigue damage patterns are investigated at the microscopic scale by distinguishing crack initiation and crack growth. Results show that the cracks initiate from microstructural defects, whose mean diameter does not exceed 400 mu m and that crack initiation at the macroscopic scale corresponds to crack growth at the microscopic scale, which validates recent energetic approaches adopted to predict fatigue crack initiation in rubbers. The morphology of fracture surfaces exhibits two types of features: wrenchings and fatigue Striations. In particular, results highlight that several shapes of fatigue Striations can form, depending on the loading conditions, and that several mechanisms of fatigue Striation formation could come into play.
A J Lichtenberg - One of the best experts on this subject based on the ideXlab platform.
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multi mode ionization instability induced Striations in rf driven he h2o atmospheric pressure plasma app discharges
Physics of Plasmas, 2019Co-Authors: E Kawamura, M A Lieberman, A J LichtenbergAbstract:Previously [E. Kawamura et al., Plasma Sources Sci. Technol. 25, 054009 (2016) and E. Kawamura et al., J. Phys. D: Appl. Phys. 50, 145204 (2017)], one dimensional (1D) particle-in-cell (PIC) simulations of 1 to 4 mm gap, He/2%H2O atmospheric pressure plasma discharges showed an ionization instability resulting in bulk Striations. Assuming that the ionization rate coefficient Kiz is related to the root mean square electric field E by Kiz ∝ Eq, a Striation theory showed that q 0, implying that nonlocal electron kinetics are required for the instability. Wider gaps can fit in a wider range of wavelengths, resulting in multi-mode Striations. Previously, we assumed a single mean q value for each discharge, and did not calculate q for each mode separately. Here, we develop a wavelength resolved global Striation model and apply it to 1D PIC simulations of 4 mm gap discharges with input currents Jrf = 0.04 to 0.30 A/cm2. We first examine a base case at 0.23 A/cm2 and observe a mixture of unstable modes within a window of wavelengths λ. At shorter λ, the modes are suppressed by diffusion. At longer λ, we observe a transition to locality in which q becomes less negative with increasing λ, approaching its local positive value and stabilizing the modes. The window of unstable modes shifts to shorter λ with increasing Jrf, causing the modes to be suppressed by diffusion at higher Jrf. At lower Jrf, the decrease in bulk plasma density with decreasing Jrf suppresses the Striations.Previously [E. Kawamura et al., Plasma Sources Sci. Technol. 25, 054009 (2016) and E. Kawamura et al., J. Phys. D: Appl. Phys. 50, 145204 (2017)], one dimensional (1D) particle-in-cell (PIC) simulations of 1 to 4 mm gap, He/2%H2O atmospheric pressure plasma discharges showed an ionization instability resulting in bulk Striations. Assuming that the ionization rate coefficient Kiz is related to the root mean square electric field E by Kiz ∝ Eq, a Striation theory showed that q 0, implying that nonlocal electron kinetics are required for the instability. Wider gaps can fit in a wider range of wavelengths, resulting in multi-mode Striations. Previously, we assumed a single mean q value for each discharge, and did not calculate q for each mode separately. Here, we develop a wavelength resolved global Striation model and apply it to 1D PIC simulations of 4 mm gap discharges with input currents Jrf = 0.04 to 0.30 A/cm2. We first ex...
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ionization instability induced Striations in low frequency and pulsed he h2o atmospheric pressure plasmas
Physics of Plasmas, 2018Co-Authors: E Kawamura, M A Lieberman, A J LichtenbergAbstract:In previous work [Kawamura et al., Plasma Sources Sci. Technol. 25, 054009 (2016)] and [Kawamura et al., J. Phys. D: Appl. Phys. 50, 145204 (2017)], 1D kinetic particle-in-cell (PIC) simulations of narrow gap (1 to 4 mm), high frequency (27 MHz) or dc-driven, He/2%H2O atmospheric pressure plasmas (APPs) showed an ionization instability resulting in standing Striations (spatial oscillations) in the bulk plasma. We developed a steady-state Striation theory which showed that the Striations are due to non-local electron kinetics. In both the high frequency and dc-driven cases, the equilibrium electron density n0 in the plasma bulk was stationary. In this work, we first conduct 1D PIC simulations of a 1 mm gap He/2%H2O APP, driven by a sinusoidal current at a low frequency of f = 50 kHz such that ω = 2πf is well below the ionization frequency νiz. In this case, n0 varies with time, and we observe a time-varying instability which quasistatically depends on n0(t). At each phase of the rf cycle, the discharge res...
Jean-benoit Le Cam - One of the best experts on this subject based on the ideXlab platform.
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Fatigue damage in carbon black filled natural rubber under uni- and multiaxial loading conditions
International Journal of Fatigue, 2013Co-Authors: Jean-benoit Le Cam, Bertrand Huneau, Erwan VerronAbstract:This paper deals with fatigue damage in carbon black filled natural rubber under uni- and multiaxial loading conditions. Fatigue damage is described at both the macroscopic (mechanical) scale and the microscopic (material) scale. The different fatigue damages observed at the macroscopic scale are presented according to the prescribed loading conditions. At this scale, five elementary fatigue damage patterns are defined, three correspond to external macroscopic cracks and two correspond to internal macroscopic cracks. These elementary fatigue damage patterns are investigated at the microscopic scale by distinguishing crack initiation and crack growth. Results show that the cracks initiate from microstructural defects, whose mean diameter does not exceed 400 mu m and that crack initiation at the macroscopic scale corresponds to crack growth at the microscopic scale, which validates recent energetic approaches adopted to predict fatigue crack initiation in rubbers. The morphology of fracture surfaces exhibits two types of features: wrenchings and fatigue Striations. In particular, results highlight that several shapes of fatigue Striations can form, depending on the loading conditions, and that several mechanisms of fatigue Striation formation could come into play.
E Kawamura - One of the best experts on this subject based on the ideXlab platform.
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multi mode ionization instability induced Striations in rf driven he h2o atmospheric pressure plasma app discharges
Physics of Plasmas, 2019Co-Authors: E Kawamura, M A Lieberman, A J LichtenbergAbstract:Previously [E. Kawamura et al., Plasma Sources Sci. Technol. 25, 054009 (2016) and E. Kawamura et al., J. Phys. D: Appl. Phys. 50, 145204 (2017)], one dimensional (1D) particle-in-cell (PIC) simulations of 1 to 4 mm gap, He/2%H2O atmospheric pressure plasma discharges showed an ionization instability resulting in bulk Striations. Assuming that the ionization rate coefficient Kiz is related to the root mean square electric field E by Kiz ∝ Eq, a Striation theory showed that q 0, implying that nonlocal electron kinetics are required for the instability. Wider gaps can fit in a wider range of wavelengths, resulting in multi-mode Striations. Previously, we assumed a single mean q value for each discharge, and did not calculate q for each mode separately. Here, we develop a wavelength resolved global Striation model and apply it to 1D PIC simulations of 4 mm gap discharges with input currents Jrf = 0.04 to 0.30 A/cm2. We first examine a base case at 0.23 A/cm2 and observe a mixture of unstable modes within a window of wavelengths λ. At shorter λ, the modes are suppressed by diffusion. At longer λ, we observe a transition to locality in which q becomes less negative with increasing λ, approaching its local positive value and stabilizing the modes. The window of unstable modes shifts to shorter λ with increasing Jrf, causing the modes to be suppressed by diffusion at higher Jrf. At lower Jrf, the decrease in bulk plasma density with decreasing Jrf suppresses the Striations.Previously [E. Kawamura et al., Plasma Sources Sci. Technol. 25, 054009 (2016) and E. Kawamura et al., J. Phys. D: Appl. Phys. 50, 145204 (2017)], one dimensional (1D) particle-in-cell (PIC) simulations of 1 to 4 mm gap, He/2%H2O atmospheric pressure plasma discharges showed an ionization instability resulting in bulk Striations. Assuming that the ionization rate coefficient Kiz is related to the root mean square electric field E by Kiz ∝ Eq, a Striation theory showed that q 0, implying that nonlocal electron kinetics are required for the instability. Wider gaps can fit in a wider range of wavelengths, resulting in multi-mode Striations. Previously, we assumed a single mean q value for each discharge, and did not calculate q for each mode separately. Here, we develop a wavelength resolved global Striation model and apply it to 1D PIC simulations of 4 mm gap discharges with input currents Jrf = 0.04 to 0.30 A/cm2. We first ex...
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ionization instability induced Striations in low frequency and pulsed he h2o atmospheric pressure plasmas
Physics of Plasmas, 2018Co-Authors: E Kawamura, M A Lieberman, A J LichtenbergAbstract:In previous work [Kawamura et al., Plasma Sources Sci. Technol. 25, 054009 (2016)] and [Kawamura et al., J. Phys. D: Appl. Phys. 50, 145204 (2017)], 1D kinetic particle-in-cell (PIC) simulations of narrow gap (1 to 4 mm), high frequency (27 MHz) or dc-driven, He/2%H2O atmospheric pressure plasmas (APPs) showed an ionization instability resulting in standing Striations (spatial oscillations) in the bulk plasma. We developed a steady-state Striation theory which showed that the Striations are due to non-local electron kinetics. In both the high frequency and dc-driven cases, the equilibrium electron density n0 in the plasma bulk was stationary. In this work, we first conduct 1D PIC simulations of a 1 mm gap He/2%H2O APP, driven by a sinusoidal current at a low frequency of f = 50 kHz such that ω = 2πf is well below the ionization frequency νiz. In this case, n0 varies with time, and we observe a time-varying instability which quasistatically depends on n0(t). At each phase of the rf cycle, the discharge res...
Bertrand Huneau - One of the best experts on this subject based on the ideXlab platform.
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Fatigue damage in carbon black filled natural rubber under uni- and multiaxial loading conditions
International Journal of Fatigue, 2013Co-Authors: Jean-benoit Le Cam, Bertrand Huneau, Erwan VerronAbstract:This paper deals with fatigue damage in carbon black filled natural rubber under uni- and multiaxial loading conditions. Fatigue damage is described at both the macroscopic (mechanical) scale and the microscopic (material) scale. The different fatigue damages observed at the macroscopic scale are presented according to the prescribed loading conditions. At this scale, five elementary fatigue damage patterns are defined, three correspond to external macroscopic cracks and two correspond to internal macroscopic cracks. These elementary fatigue damage patterns are investigated at the microscopic scale by distinguishing crack initiation and crack growth. Results show that the cracks initiate from microstructural defects, whose mean diameter does not exceed 400 mu m and that crack initiation at the macroscopic scale corresponds to crack growth at the microscopic scale, which validates recent energetic approaches adopted to predict fatigue crack initiation in rubbers. The morphology of fracture surfaces exhibits two types of features: wrenchings and fatigue Striations. In particular, results highlight that several shapes of fatigue Striations can form, depending on the loading conditions, and that several mechanisms of fatigue Striation formation could come into play.
