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Y M Gupta - One of the best experts on this subject based on the ideXlab platform.

  • shock compression of molybdenum single Crystals to 110 gpa elastic plastic deformation and Crystal Anisotropy
    Journal of Applied Physics, 2020
    Co-Authors: Tomoyuki Oniyama, Y M Gupta, Guruswami Ravichandran
    Abstract:

    To investigate the role of Crystal Anisotropy on the elastic–plastic deformation of BCC single Crystals at high shock stresses, molybdenum (Mo) single Crystals were shock compressed along the [100], [111], and [110] orientations at elastic impact stresses between 20 and 110 GPa. Laser interferometry was used to measure shock wave velocities and particle velocity histories. Along the [100] and [111] orientations, elastic–plastic waves (two wave structure) were observed up to 110 GPa. Along the [110] orientation, the two wave structure was observed only up to 90 GPa. The measured elastic wave amplitudes were analyzed to determine Crystal Anisotropy effects, impact stress dependence, and the activated slip systems on the Hugoniot elastic limit. The findings from our work have provided insight into the role of Crystal Anisotropy on the elastic–plastic deformation under shock compression at high stresses.

  • elastic plastic deformation of molybdenum single Crystals shocked to 12 5 gpa Crystal Anisotropy effects
    Journal of Applied Physics, 2019
    Co-Authors: A Mandal, Y M Gupta
    Abstract:

    To understand Crystal Anisotropy effects on shock-induced elastic-plastic deformation of molybdenum (Mo), results from high-purity single Crystals shocked along [110] and [111] orientations to an elastic impact stress of 12.5 GPa were obtained and compared with the [100] results previously reported [A. Mandal and Y. M Gupta, J. Appl. Phys. 121, 045903 (2017)]. Measured wave profiles showed a time-dependent response, and strong Anisotropy was observed in the elastic wave attenuation with the propagation distance, elastic limits, shock speeds, and overall structure of the wave profiles. Resolved shear stresses on {110}〈111〉 and {112}〈111〉 slip systems provided insight into the observed Anisotropy in elastic wave attenuation and elastic limits and showed that shear stresses, and not longitudinal stresses, are a better measure of strength in shocked single Crystals. Under shock compression, resolved shear stresses at elastic limits were comparable to the Peierls stress of screw dislocations in Mo. Elastic wave attenuation was rapid when shear stresses were larger than the Peierls stress. Large differences in the elastic limits under shock and quasi-static loading are likely a consequence of the large Peierls stress value for Mo. Numerically simulated wave profiles, obtained using the dislocation-based plasticity model described in the [100] work, showed good agreement with all measured wave profiles but could not differentiate between the {110}〈111〉 and {112}〈111〉 slip systems. Overall, experimental results and corresponding numerical simulations for the three Crystal orientations have provided a comprehensive insight into shock-induced elastic-plastic deformation of Mo single Crystals, including the development of a continuum material model.

  • shock compression and release of a axis magnesium single Crystals Anisotropy and time dependent inelastic response
    Journal of Applied Physics, 2017
    Co-Authors: P Renganathan, J M Winey, Y M Gupta
    Abstract:

    To gain insight into inelastic deformation mechanisms for shocked hexagonal close-packed (hcp) metals, particularly the role of Crystal Anisotropy, magnesium (Mg) single Crystals were subjected to shock compression and release along the a-axis to 3.0 and 4.8 GPa elastic impact stresses. Wave profiles measured at several thicknesses, using laser interferometry, show a sharply peaked elastic wave followed by the plastic wave. Additionally, a smooth and featureless release wave is observed following peak compression. When compared with wave profiles measured previously for c-axis Mg [Winey et al., J. Appl. Phys. 117, 105903 (2015)], the elastic wave amplitudes for a-axis Mg are lower for the same propagation distance, and less attenuation of elastic wave amplitude is observed for a given peak stress. The featureless release wave for a-axis Mg is in marked contrast to the structured features observed for c-axis unloading. Numerical simulations, using a time-dependent anisotropic modeling framework, showed tha...

  • shock compression of aluminum single Crystals to 70 gpa role of Crystalline Anisotropy
    Journal of Applied Physics, 2013
    Co-Authors: D Choudhuri, Y M Gupta
    Abstract:

    Crystalline Anisotropy effects were examined at high stresses by shock compressing Al single Crystals along ⟨100⟩, ⟨110⟩, and ⟨111⟩ orientations to peak stresses ranging from 40 to 70 GPa. Laser-interferometry was used to monitor particle velocity histories, including unloading wave profiles. A single, flat-top shock wave followed by a structured release was observed in all the experiments. Shock velocities and longitudinal sound speeds (onset of release) were also determined from the measured particle velocity histories. Within experimental uncertainty (1%–2%), the Hugoniots for the three orientations were indistinguishable, and a single longitudinal stress-density curve was fit to all peak state data. In contrast, the longitudinal sound speeds (and the resulting longitudinal elastic moduli) in the shocked state showed Crystal Anisotropy effects over the entire stress range examined (up to ∼50% density compression). The measured longitudinal elastic moduli at the highest stress represent more than a fourfold increase from the ambient value and showed continuing Anisotropy with compression. The present findings show that Hugoniots may not be the optimal measure of Crystalline Anisotropy, and even low-Anisotropy single Crystals, like Al, can manifest significant Anisotropy in elastic moduli at large shock compressions.

Olaf Eisen - One of the best experts on this subject based on the ideXlab platform.

  • seismic wave propagation in anisotropic ice part 1 elasticity tensor and derived quantities from ice core properties
    The Cryosphere, 2015
    Co-Authors: Anja Diez, Olaf Eisen
    Abstract:

    Abstract. A preferred orientation of the anisotropic ice Crystals influences the viscosity of the ice bulk and the dynamic behaviour of glaciers and ice sheets. Knowledge about the distribution of Crystal Anisotropy is mainly provided by Crystal orientation fabric (COF) data from ice cores. However, the developed anisotropic fabric influences not only the flow behaviour of ice but also the propagation of seismic waves. Two effects are important: (i) sudden changes in COF lead to englacial reflections, and (ii) the anisotropic fabric induces an angle dependency on the seismic velocities and, thus, recorded travel times. A framework is presented here to connect COF data from ice cores with the elasticity tensor to determine seismic velocities and reflection coefficients for cone and girdle fabrics. We connect the microscopic Anisotropy of the Crystals with the macroscopic Anisotropy of the ice mass, observable with seismic methods. Elasticity tensors for different fabrics are calculated and used to investigate the influence of the anisotropic ice fabric on seismic velocities and reflection coefficients, englacially as well as for the ice–bed contact. Hence, it is possible to remotely determine the bulk ice Anisotropy.

  • seismic wave propagation in anisotropic ice part 2 effects of Crystal Anisotropy in geophysical data
    The Cryosphere, 2014
    Co-Authors: Anja Diez, Olaf Eisen, Coen Hofstede, A Lambrecht, Christoph Mayer, Heinrich Miller, Daniel Steinhage, T Binder, Ilka Weikusat
    Abstract:

    We investigate the propagation of seismic waves in anisotropic ice. Two effects are important: (i) sudden changes in Crystal orientation fabric (COF) lead to englacial reflections; (ii) the anisotropic fabric induces an angle dependency on the seismic velocities and, thus, recorded travel times. Velocities calculated from the polyCrystal elasticity tensor derived for the anisotropic fabric from measured COF eigenvalues of the EDML ice core, Antarctica, show good agreement with the velocity trend determined from vertical seismic profiling. The agreement of the absolute velocity values, however, depends on the choice of the monoCrystal elasticity tensor used for the calculation of the polyCrystal properties. We make use of abrupt changes in COF as a common reflection mechanism for seismic and radar data below the firn–ice transition to determine COF-induced reflections in either data set by joint comparison with ice-core data. Our results highlight the possibility to complement regional radar surveys with local, surface-based seismic experiments to separate isochrones in radar data from other mechanisms. This is important for the reconnaissance of future ice-core drill sites, where accurate isochrone (i.e. non-COF) layer integrity allows for synchronization with other cores, as well as studies of ice dynamics considering non-homogeneous ice viscosity from preferred Crystal orientations.

Arnd Pralle - One of the best experts on this subject based on the ideXlab platform.

  • model driven optimization of magnetic Anisotropy of exchange coupled core shell ferrite nanoparticles for maximal hysteretic loss
    Chemistry of Materials, 2015
    Co-Authors: Qian Zhang, Rahul Munshi, Iñaki Orue, Beatriz Pelaz, Katharina Ines Gries, Wolfgang J. Parak, Pablo Del Pino, Idoia Castellanosrubio, Arnd Pralle
    Abstract:

    This study provides a guide to maximizing hysteretic loss by matching the design and synthesis of superparamagnetic nanoparticles to the desired hyperthermia application. The maximal heat release from magnetic nanoparticles to the environment depends on intrinsic properties of magnetic nanoparticles (e.g., size, magnetization, and magnetic Anisotropy) and extrinsic properties of the applied fields (e.g., frequency and field strength). Often, the biomedical hyperthermia application limits flexibility in settings of many parameters (e.g., nanoparticle size and mobility, field strength, and frequency). We show that core–shell nanoparticles combining a soft (Mn ferrite) and a hard (Co ferrite) magnetic material form a system in which the effective magnetic Anisotropy can be easily tuned independently of the nanoparticle size. A theoretical framework to include the Crystal Anisotropy contribution of the Co ferrite phase to the nanoparticle’s total Anisotropy is developed. The experimental results confirm that ...

  • Model Driven Optimization of Magnetic Anisotropy of Exchange-Coupled Core–Shell Ferrite Nanoparticles for Maximal Hysteretic Loss
    2015
    Co-Authors: Qian Zhang, Idoia Castellanos-rubio, Rahul Munshi, Iñaki Orue, Beatriz Pelaz, Katharina Ines Gries, Wolfgang J. Parak, Pablo Del Pino, Arnd Pralle
    Abstract:

    This study provides a guide to maximizing hysteretic loss by matching the design and synthesis of superparamagnetic nanoparticles to the desired hyperthermia application. The maximal heat release from magnetic nanoparticles to the environment depends on intrinsic properties of magnetic nanoparticles (e.g., size, magnetization, and magnetic Anisotropy) and extrinsic properties of the applied fields (e.g., frequency and field strength). Often, the biomedical hyperthermia application limits flexibility in settings of many parameters (e.g., nanoparticle size and mobility, field strength, and frequency). We show that core–shell nanoparticles combining a soft (Mn ferrite) and a hard (Co ferrite) magnetic material form a system in which the effective magnetic Anisotropy can be easily tuned independently of the nanoparticle size. A theoretical framework to include the Crystal Anisotropy contribution of the Co ferrite phase to the nanoparticle’s total Anisotropy is developed. The experimental results confirm that this framework predicts the hysteretic heating loss correctly when including nonlinear effects in an effective susceptibility. Hence, we provide a guide on how to characterize the magnetic Anisotropy of core–shell magnetic nanoparticles, model the expected heat loss, and thereby synthesize tuned nanoparticles for a particular biomedical application

Anja Diez - One of the best experts on this subject based on the ideXlab platform.

  • seismic wave propagation in anisotropic ice part 1 elasticity tensor and derived quantities from ice core properties
    The Cryosphere, 2015
    Co-Authors: Anja Diez, Olaf Eisen
    Abstract:

    Abstract. A preferred orientation of the anisotropic ice Crystals influences the viscosity of the ice bulk and the dynamic behaviour of glaciers and ice sheets. Knowledge about the distribution of Crystal Anisotropy is mainly provided by Crystal orientation fabric (COF) data from ice cores. However, the developed anisotropic fabric influences not only the flow behaviour of ice but also the propagation of seismic waves. Two effects are important: (i) sudden changes in COF lead to englacial reflections, and (ii) the anisotropic fabric induces an angle dependency on the seismic velocities and, thus, recorded travel times. A framework is presented here to connect COF data from ice cores with the elasticity tensor to determine seismic velocities and reflection coefficients for cone and girdle fabrics. We connect the microscopic Anisotropy of the Crystals with the macroscopic Anisotropy of the ice mass, observable with seismic methods. Elasticity tensors for different fabrics are calculated and used to investigate the influence of the anisotropic ice fabric on seismic velocities and reflection coefficients, englacially as well as for the ice–bed contact. Hence, it is possible to remotely determine the bulk ice Anisotropy.

  • seismic wave propagation in anisotropic ice part 2 effects of Crystal Anisotropy in geophysical data
    The Cryosphere, 2014
    Co-Authors: Anja Diez, Olaf Eisen, Coen Hofstede, A Lambrecht, Christoph Mayer, Heinrich Miller, Daniel Steinhage, T Binder, Ilka Weikusat
    Abstract:

    We investigate the propagation of seismic waves in anisotropic ice. Two effects are important: (i) sudden changes in Crystal orientation fabric (COF) lead to englacial reflections; (ii) the anisotropic fabric induces an angle dependency on the seismic velocities and, thus, recorded travel times. Velocities calculated from the polyCrystal elasticity tensor derived for the anisotropic fabric from measured COF eigenvalues of the EDML ice core, Antarctica, show good agreement with the velocity trend determined from vertical seismic profiling. The agreement of the absolute velocity values, however, depends on the choice of the monoCrystal elasticity tensor used for the calculation of the polyCrystal properties. We make use of abrupt changes in COF as a common reflection mechanism for seismic and radar data below the firn–ice transition to determine COF-induced reflections in either data set by joint comparison with ice-core data. Our results highlight the possibility to complement regional radar surveys with local, surface-based seismic experiments to separate isochrones in radar data from other mechanisms. This is important for the reconnaissance of future ice-core drill sites, where accurate isochrone (i.e. non-COF) layer integrity allows for synchronization with other cores, as well as studies of ice dynamics considering non-homogeneous ice viscosity from preferred Crystal orientations.

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

  • model driven optimization of magnetic Anisotropy of exchange coupled core shell ferrite nanoparticles for maximal hysteretic loss
    Chemistry of Materials, 2015
    Co-Authors: Qian Zhang, Rahul Munshi, Iñaki Orue, Beatriz Pelaz, Katharina Ines Gries, Wolfgang J. Parak, Pablo Del Pino, Idoia Castellanosrubio, Arnd Pralle
    Abstract:

    This study provides a guide to maximizing hysteretic loss by matching the design and synthesis of superparamagnetic nanoparticles to the desired hyperthermia application. The maximal heat release from magnetic nanoparticles to the environment depends on intrinsic properties of magnetic nanoparticles (e.g., size, magnetization, and magnetic Anisotropy) and extrinsic properties of the applied fields (e.g., frequency and field strength). Often, the biomedical hyperthermia application limits flexibility in settings of many parameters (e.g., nanoparticle size and mobility, field strength, and frequency). We show that core–shell nanoparticles combining a soft (Mn ferrite) and a hard (Co ferrite) magnetic material form a system in which the effective magnetic Anisotropy can be easily tuned independently of the nanoparticle size. A theoretical framework to include the Crystal Anisotropy contribution of the Co ferrite phase to the nanoparticle’s total Anisotropy is developed. The experimental results confirm that ...

  • Model Driven Optimization of Magnetic Anisotropy of Exchange-Coupled Core–Shell Ferrite Nanoparticles for Maximal Hysteretic Loss
    2015
    Co-Authors: Qian Zhang, Idoia Castellanos-rubio, Rahul Munshi, Iñaki Orue, Beatriz Pelaz, Katharina Ines Gries, Wolfgang J. Parak, Pablo Del Pino, Arnd Pralle
    Abstract:

    This study provides a guide to maximizing hysteretic loss by matching the design and synthesis of superparamagnetic nanoparticles to the desired hyperthermia application. The maximal heat release from magnetic nanoparticles to the environment depends on intrinsic properties of magnetic nanoparticles (e.g., size, magnetization, and magnetic Anisotropy) and extrinsic properties of the applied fields (e.g., frequency and field strength). Often, the biomedical hyperthermia application limits flexibility in settings of many parameters (e.g., nanoparticle size and mobility, field strength, and frequency). We show that core–shell nanoparticles combining a soft (Mn ferrite) and a hard (Co ferrite) magnetic material form a system in which the effective magnetic Anisotropy can be easily tuned independently of the nanoparticle size. A theoretical framework to include the Crystal Anisotropy contribution of the Co ferrite phase to the nanoparticle’s total Anisotropy is developed. The experimental results confirm that this framework predicts the hysteretic heating loss correctly when including nonlinear effects in an effective susceptibility. Hence, we provide a guide on how to characterize the magnetic Anisotropy of core–shell magnetic nanoparticles, model the expected heat loss, and thereby synthesize tuned nanoparticles for a particular biomedical application