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John K. Dukowicz - One of the best experts on this subject based on the ideXlab platform.
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An Elastic–Viscous–Plastic Model for Sea Ice Dynamics
Journal of Physical Oceanography, 1997Co-Authors: Elizabeth C. Hunke, John K. DukowiczAbstract:The standard Model for sea ice dynamics treats the ice pack as a visco‐Plastic material that flows Plastically under typical stress conditions but behaves as a linear viscous fluid where strain rates are small and the ice becomes nearly rigid. Because of large viscosities in these regions, implicit numerical methods are necessary for time steps larger than a few seconds. Current solution methods for these equations use iterative relaxation methods, which are time consuming, scale poorly with mesh resolution, and are not well adapted to parallel computation. To remedy this, the authors developed and tested two separate methods. First, by demonstrating that the viscous‐Plastic rheology can be represented by a symmetric, negative definite matrix operator, the much faster and better behaved preconditioned conjugate gradient method was implemented. Second, realizing that only the response of the ice on timescales associated with wind forcing need be accurately resolved, the Model was modified so that it reduces to the viscous‐Plastic Model at these timescales, whereas at shorter timescales the adjustment process takes place by a numerically more efficient elastic wave mechanism. This modification leads to a fully explicit numerical scheme that further improves the Model’s computational efficiency and is a great advantage for implementations on parallel machines. Furthermore, it is observed that the standard viscous‐Plastic Model has poor dynamic response to forcing on a daily timescale, given the standard time step (1 day) used by the ice Modeling community. In contrast, the explicit discretization of the elastic wave mechanism allows the elastic‐viscous‐Plastic Model to capture the ice response to variations in the imposed stress more accurately. Thus, the elastic‐viscous‐Plastic Model provides more accurate results for shorter timescales associated with physical forcing, reproduces viscous‐Plastic Model behavior on longer timescales, and is computationally more efficient overall.
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an elastic viscous Plastic Model for sea ice dynamics
Journal of Physical Oceanography, 1997Co-Authors: Elizabeth C. Hunke, John K. DukowiczAbstract:The standard Model for sea ice dynamics treats the ice pack as a visco‐Plastic material that flows Plastically under typical stress conditions but behaves as a linear viscous fluid where strain rates are small and the ice becomes nearly rigid. Because of large viscosities in these regions, implicit numerical methods are necessary for time steps larger than a few seconds. Current solution methods for these equations use iterative relaxation methods, which are time consuming, scale poorly with mesh resolution, and are not well adapted to parallel computation. To remedy this, the authors developed and tested two separate methods. First, by demonstrating that the viscous‐Plastic rheology can be represented by a symmetric, negative definite matrix operator, the much faster and better behaved preconditioned conjugate gradient method was implemented. Second, realizing that only the response of the ice on timescales associated with wind forcing need be accurately resolved, the Model was modified so that it reduces to the viscous‐Plastic Model at these timescales, whereas at shorter timescales the adjustment process takes place by a numerically more efficient elastic wave mechanism. This modification leads to a fully explicit numerical scheme that further improves the Model’s computational efficiency and is a great advantage for implementations on parallel machines. Furthermore, it is observed that the standard viscous‐Plastic Model has poor dynamic response to forcing on a daily timescale, given the standard time step (1 day) used by the ice Modeling community. In contrast, the explicit discretization of the elastic wave mechanism allows the elastic‐viscous‐Plastic Model to capture the ice response to variations in the imposed stress more accurately. Thus, the elastic‐viscous‐Plastic Model provides more accurate results for shorter timescales associated with physical forcing, reproduces viscous‐Plastic Model behavior on longer timescales, and is computationally more efficient overall.
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An elastic-viscous-Plastic Model for sea ice dynamics
1996Co-Authors: Elizabeth C. Hunke, John K. DukowiczAbstract:The standard Model for sea ice dynamics treats the ice pack as a viscous-Plastic material that flows Plastically under typical stress conditions but behaves as a linear viscous fluid where strain rates are small and the ice becomes nearly rigid. Because of large viscosities in these regions, implicit numerical methods are necessary for timesteps larger than a few seconds. Current solution methods for these equations use iterative relaxation methods, which are time consuming, scale poorly with mesh resolution, and are not well adapted to parallel computation. To remedy this, we have developed and tested two separate methods. First, by demonstrating that the viscous-Plastic rheology can be represented by a symmetric, negative definite matrix operator, we have implemented the faster and better behaved preconditioned conjugate gradient method. Second, realizing that only the response of the ice on time scales associated with wind forcing need be accurately resolved, we have modified the Model to reduce to the viscous-Plastic Model at these time scales; at shorter time scales the adjustment process takes place by a numerically efficient elastic wave mechanism. This modification leads to a fully explicit numerical scheme which further improves the computational efficiency and is an advantage for implementations on parallel machines. Furthermore, we observe that the standard viscous-Plastic Model has poor dynamic response to forcing on a daily time scale, given the standard time step (1 day) used by the ice Modeling community. In contrast, the explicit discretization of the elastic wave mechanism allows the elastic-viscous-Plastic Model to capture the ice response to variations in the imposed stress more accurately. Thus, the elastic-viscous-Plastic Model provides more accurate results for shorter time scales associated with physical forcing, reproduces viscous-Plastic Model behavior on longer time scales, and is computationally more efficient. 49 refs., 13 figs., 6 tabs.
Pierre-yves Hicher - One of the best experts on this subject based on the ideXlab platform.
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Equations of pressuremeter curve with an elastic strain-softening Plastic Model
2018Co-Authors: Christophe Dano, Pierre-yves HicherAbstract:We propose analytical expressions of the pressuremeter curve that generalise previous equations found in the literature. We consider a linear elastic Plastic Model with strain-softening, assuming a Mohr-Coulomb yield surface. The softening behaviour affects either the cohesion or the friction angle. Three parameters are required to describe the softening behaviour. We finally show the effect of each of these three parameters on the pressuremeter curve.
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A two yielding surface elasto-Plastic Model with consideration of grain breakage
2010Co-Authors: Christophe Dano, Pierre-yves HicherAbstract:An elasto-Plastic Model with two yield surfaces has been developed for the simulation of granular materials with consideration of grain ruptures. Grain breakage is induced by deviatoric as well as isotropic stresses. One yield function is based on a Mohr-Coulomb criterion with a hyperbolic hardening function of the Plastic deviatoric strain. A second yield function is introduced to describe the Plastic behaviour under compression, in which a hardening function of the Plastic volumetric strain is introduced. The main assumption of this Model is that, upon loading, the position of the critical state changes as a consequence of grain breakage. The effect of the grain size distribution is introduced in the relationship between the void ratio at critical state and the mean effective stress. Triaxial and oedometer tests have been performed on crushable granular materials. Comparison of experimental results and numerical simulations shows that the new Model can reproduce with good accuracy the behaviour of granular materials subjected to grain ruptures during mechanical loading.
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an elasto Plastic Model for granular materials with microstructural consideration
International Journal of Solids and Structures, 2005Co-Authors: Ching S Chang, Pierre-yves HicherAbstract:Abstract In this paper, we have extended the granular mechanics approach to derive an elasto-Plastic stress–strain relationship. The deformation of a representative volume of the material is generated by mobilizing particle contacts in all orientations. Thus, the stress–strain relationship can be derived as an average of the mobilization behavior of these local contact planes. The local behavior is assumed to follow a Hertz–Mindlin’s elastic law and a Mohr–Coulomb’s Plastic law. Essential features such as continuous displacement field, inter-particle stiffness, and fabric tensor are discussed. The predictions of the derived stress–strain Model are compared to experimental results for sand under both drained and undrained triaxial loading conditions. The comparisons demonstrate the ability of this Model to reproduce accurately the overall mechanical behavior of granular media and to account for the influence of key parameters such as void ratio and mean stress. A part of this paper is devoted to the study of anisotropic specimens loaded in different directions, which shows the Model capability of considering the influence of inherent anisotropy on the stress–strain response under a drained triaxial loading condition.
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Identification of the parameters of an elasto-Plastic Model with strain-softening by inverse analysis of pressuremeter tests
2002Co-Authors: Christophe Dano, Pierre-yves HicherAbstract:In this paper, we present a procedure for the identification of the parameters of constitutive Models from in situ pressuremeter tests. We first develop a semi-analytical solution of the pressuremeter curve using a linear elastic perfectly Plastic Model with a post-peak strain-softening and a small strain hypothesis. More usual expressions of the pressuremeter curve are then deduced. These expressions have been implemented in a commercial software. Finally, we show the effect of the softening and of the strain level hypothesis on the values of the friction angle obtained by optimisation computations using a Gauss-Newton algorithm.
Elizabeth C. Hunke - One of the best experts on this subject based on the ideXlab platform.
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An Elastic–Viscous–Plastic Model for Sea Ice Dynamics
Journal of Physical Oceanography, 1997Co-Authors: Elizabeth C. Hunke, John K. DukowiczAbstract:The standard Model for sea ice dynamics treats the ice pack as a visco‐Plastic material that flows Plastically under typical stress conditions but behaves as a linear viscous fluid where strain rates are small and the ice becomes nearly rigid. Because of large viscosities in these regions, implicit numerical methods are necessary for time steps larger than a few seconds. Current solution methods for these equations use iterative relaxation methods, which are time consuming, scale poorly with mesh resolution, and are not well adapted to parallel computation. To remedy this, the authors developed and tested two separate methods. First, by demonstrating that the viscous‐Plastic rheology can be represented by a symmetric, negative definite matrix operator, the much faster and better behaved preconditioned conjugate gradient method was implemented. Second, realizing that only the response of the ice on timescales associated with wind forcing need be accurately resolved, the Model was modified so that it reduces to the viscous‐Plastic Model at these timescales, whereas at shorter timescales the adjustment process takes place by a numerically more efficient elastic wave mechanism. This modification leads to a fully explicit numerical scheme that further improves the Model’s computational efficiency and is a great advantage for implementations on parallel machines. Furthermore, it is observed that the standard viscous‐Plastic Model has poor dynamic response to forcing on a daily timescale, given the standard time step (1 day) used by the ice Modeling community. In contrast, the explicit discretization of the elastic wave mechanism allows the elastic‐viscous‐Plastic Model to capture the ice response to variations in the imposed stress more accurately. Thus, the elastic‐viscous‐Plastic Model provides more accurate results for shorter timescales associated with physical forcing, reproduces viscous‐Plastic Model behavior on longer timescales, and is computationally more efficient overall.
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an elastic viscous Plastic Model for sea ice dynamics
Journal of Physical Oceanography, 1997Co-Authors: Elizabeth C. Hunke, John K. DukowiczAbstract:The standard Model for sea ice dynamics treats the ice pack as a visco‐Plastic material that flows Plastically under typical stress conditions but behaves as a linear viscous fluid where strain rates are small and the ice becomes nearly rigid. Because of large viscosities in these regions, implicit numerical methods are necessary for time steps larger than a few seconds. Current solution methods for these equations use iterative relaxation methods, which are time consuming, scale poorly with mesh resolution, and are not well adapted to parallel computation. To remedy this, the authors developed and tested two separate methods. First, by demonstrating that the viscous‐Plastic rheology can be represented by a symmetric, negative definite matrix operator, the much faster and better behaved preconditioned conjugate gradient method was implemented. Second, realizing that only the response of the ice on timescales associated with wind forcing need be accurately resolved, the Model was modified so that it reduces to the viscous‐Plastic Model at these timescales, whereas at shorter timescales the adjustment process takes place by a numerically more efficient elastic wave mechanism. This modification leads to a fully explicit numerical scheme that further improves the Model’s computational efficiency and is a great advantage for implementations on parallel machines. Furthermore, it is observed that the standard viscous‐Plastic Model has poor dynamic response to forcing on a daily timescale, given the standard time step (1 day) used by the ice Modeling community. In contrast, the explicit discretization of the elastic wave mechanism allows the elastic‐viscous‐Plastic Model to capture the ice response to variations in the imposed stress more accurately. Thus, the elastic‐viscous‐Plastic Model provides more accurate results for shorter timescales associated with physical forcing, reproduces viscous‐Plastic Model behavior on longer timescales, and is computationally more efficient overall.
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An elastic-viscous-Plastic Model for sea ice dynamics
1996Co-Authors: Elizabeth C. Hunke, John K. DukowiczAbstract:The standard Model for sea ice dynamics treats the ice pack as a viscous-Plastic material that flows Plastically under typical stress conditions but behaves as a linear viscous fluid where strain rates are small and the ice becomes nearly rigid. Because of large viscosities in these regions, implicit numerical methods are necessary for timesteps larger than a few seconds. Current solution methods for these equations use iterative relaxation methods, which are time consuming, scale poorly with mesh resolution, and are not well adapted to parallel computation. To remedy this, we have developed and tested two separate methods. First, by demonstrating that the viscous-Plastic rheology can be represented by a symmetric, negative definite matrix operator, we have implemented the faster and better behaved preconditioned conjugate gradient method. Second, realizing that only the response of the ice on time scales associated with wind forcing need be accurately resolved, we have modified the Model to reduce to the viscous-Plastic Model at these time scales; at shorter time scales the adjustment process takes place by a numerically efficient elastic wave mechanism. This modification leads to a fully explicit numerical scheme which further improves the computational efficiency and is an advantage for implementations on parallel machines. Furthermore, we observe that the standard viscous-Plastic Model has poor dynamic response to forcing on a daily time scale, given the standard time step (1 day) used by the ice Modeling community. In contrast, the explicit discretization of the elastic wave mechanism allows the elastic-viscous-Plastic Model to capture the ice response to variations in the imposed stress more accurately. Thus, the elastic-viscous-Plastic Model provides more accurate results for shorter time scales associated with physical forcing, reproduces viscous-Plastic Model behavior on longer time scales, and is computationally more efficient. 49 refs., 13 figs., 6 tabs.
Erdin Ibraim - One of the best experts on this subject based on the ideXlab platform.
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Elasto-Plastic Model for sand including time effect
Geotechnique Letters, 2016Co-Authors: Bogdan Cazacliu, Erdin IbraimAbstract:Time effects on granular soils have been observed in the laboratory and by in-situ tests, but these cannot be reproduced by classical elasto-Plastic Models. To address these concerns, existing specific Modelling approaches were based on the theory of viscoPlasticity formulated by Perzyna or on a viscous evanescent relationship. This work explores an alternative elasto-Plastic Modelling framework formulated in a multiaxial structure space. The proposed elasto-Plastic Model is associated with a thixotropic-type framework through the use of a structure parameter, the evolution of which illustrates the competition between two effects: the time-dependent tendency of the granular system to reach its stable configuration – restructuration – and its destructuration under external perturbations. The structure parameter is linked to the existence of a stress-dependent target structure towards which the current granular material structure evolves. The timescale is explicitly introduced by postulating a rate for this...
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Elasto-Plastic Model for sand including time effects
Géotechnique Letters, 2016Co-Authors: Bogdan Cazacliu, Erdin IbraimAbstract:Time effects on granular soils have been observed in the laboratory and by in-situ tests, but these cannot be reproduced by classical elasto-Plastic Models. To address these concerns, existing specific Modelling approaches were based on the theory of viscoPlasticity formulated by Perzyna or on a viscous evanescent relationship. This work explores an alternative elasto-Plastic Modelling framework formulated in a multiaxial structure space. The proposed elasto-Plastic Model is associated with a thixotropic-type framework through the use of a structure parameter, the evolution of which illustrates the competition between two effects: the time-dependent tendency of the granular system to reach its stable configuration - restructuration - and its destructuration under external perturbations. The structure parameter is linked to the existence of a stress-dependent target structure towards which the current granular material structure evolves. The timescale is explicitly introduced by postulating a rate for this structure evolution. The Modelling of the material behaviour has shown good similarities with the response of granular soils observed in monotonic loading, as well as during creep and variable strain rate loading experiments.
Tingting Jiang - One of the best experts on this subject based on the ideXlab platform.
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an elasto visco Plastic Model based on stress functions for deformation and damage of water saturated rocks during the freeze thaw process
Construction and Building Materials, 2020Co-Authors: Chunyang Zhang, Yixian Wang, Tingting JiangAbstract:Abstract Rocks can be used as building materials. In this study, based on the effect of freeze-thaw cycles (FTC) on the properties of water-saturated rocks and the theory of rheology, an elasto-visco-Plastic Model based on stress functions is proposed, which consists of the elastic, viscoelastic and viscoPlastic subModels. The elastic strain shows obvious time dependence and is different from the traditional one in the theory of creep. Although the Kelvin Model can be used to fit the relationship between elastic strain and time during the freezing process, but not suitable for thawing process. A threshold element obtained by improving the classical Plastic element in rheology is applied to improve the Kelvin Model to simulate the viscoelastic behavior of rocks, which only has the action of a valve without any Plastic flow and does not work during the thawing process. The viscoelastic strain will be generated after the frost heave stress is greater than σ f t ev , after thawing, it will not recover until time tends to infinity. The viscoPlastic strain will be developed when the frost heave stress exceeds σ f t vp , which can be divided into two substages during the freezing process, namely the substages of stress growth ( t vp ⩽ t ⩽ t cf ) and stress constancy ( t cf ⩽ t ⩽ t n ). The viscoPlastic strain will continue to develop until the frost heave stress is reduced to σ f t vp after thawing. Thus it can be seen that the characteristics of viscoPlastic strain show a unique process of damage development of water-saturated rocks during the freeze-thaw (FT) process. Finally, the Model is simplified by a piecewise linear function and adopted to fit the strain-time data of water-saturated red sandstone samples during the freezing process.
