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http://hdl.handle.net/10985/9375
The GranOO workbench, a new tool for developing discrete element simulations, and its application to tribological problems
ANDRE, Damien; CHARLES, Jean-Luc; IORDANOFF, Ivan; NEAUPORT, Jérôme
Discrete models are based on the descriptions of the physical states (e.g., velocity, position, temperature, magnetic momenta and electric potential) of a large number of discrete elements that form the media under study. These models are not based on a continuous description of the media. Thus, the models are particularly well adapted to describe the evolution of media driven by discontinuous phenomena such as multi-fracturation followed by debris flow as occurs in wear studies. Recently, the use of discrete models has been widened to face problems of complex rheological behaviors and/or multi-physical behaviors. Multi-physical problems involves complex mathematical formulations because of the combination of different families of differential equations when a continuous approach is chosen. These formulas are often much simpler to express in discrete models, in which each particle has a physical state and the evolution of that state is due to local physical interactions among particles. Since the year 2000, this method has been widely applied to the study of tribological problems including wear (Fillot et al., 2007) [1], the thermo-mechanical behavior of a contact (Richard et al., 2008) [2] and subsurface damage due to surface polishing (Iordanoff et al., 2008) [3]. Recent works have shown how this method can be used to obtain quantitative results (André et al., 2012) [4]. To assist and promote research in this area, a free platform GranOO has been developed under a C++ environment and is distributed under a free GPL license. The primary features of this platform are presented in this paper. In addition, a series of examples that illustrate the main steps to construct a reliable tribological numerical simulation are detailed. The details of this platform can be found at http://www.granoo.org.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10985/93752014-01-01T00:00:00ZANDRE, DamienCHARLES, Jean-LucIORDANOFF, IvanNEAUPORT, JérômeDiscrete models are based on the descriptions of the physical states (e.g., velocity, position, temperature, magnetic momenta and electric potential) of a large number of discrete elements that form the media under study. These models are not based on a continuous description of the media. Thus, the models are particularly well adapted to describe the evolution of media driven by discontinuous phenomena such as multi-fracturation followed by debris flow as occurs in wear studies. Recently, the use of discrete models has been widened to face problems of complex rheological behaviors and/or multi-physical behaviors. Multi-physical problems involves complex mathematical formulations because of the combination of different families of differential equations when a continuous approach is chosen. These formulas are often much simpler to express in discrete models, in which each particle has a physical state and the evolution of that state is due to local physical interactions among particles. Since the year 2000, this method has been widely applied to the study of tribological problems including wear (Fillot et al., 2007) [1], the thermo-mechanical behavior of a contact (Richard et al., 2008) [2] and subsurface damage due to surface polishing (Iordanoff et al., 2008) [3]. Recent works have shown how this method can be used to obtain quantitative results (André et al., 2012) [4]. To assist and promote research in this area, a free platform GranOO has been developed under a C++ environment and is distributed under a free GPL license. The primary features of this platform are presented in this paper. In addition, a series of examples that illustrate the main steps to construct a reliable tribological numerical simulation are detailed. The details of this platform can be found at http://www.granoo.org.A promising way to model cracks in composite using Discrete Element Method
http://hdl.handle.net/10985/9374
A promising way to model cracks in composite using Discrete Element Method
MAHEO, Laurent; DAU, Frédéric; ANDRE, Damien; CHARLES, Jean-Luc; IORDANOFF, Ivan
In this article, the Discrete Element Method (DEM) is taking advantage for the damage modeling of a composite material. At this stage of work, a Representative Elementary Volume (REV) of an unidirectional composite material modeled in 3D is considered to prove the relevance of the approach. The interest to introduce the Discrete Elements (DE) on the scale of constituents (fiber and matrix) is to be able to report local mechanisms of degradation such as the matrix micro-fissuring, the fiber/matrix debonding and the break of fiber, appropriate to this type of material. The short-term objective is to use this DEM modeling to treat locally the damages induced by an impact loading associated with a conventional Finite Element modeling beyond the damaged zone. First, the geometrical modelings of the fiber and the matrix are presented. The phase of calibration of the DE model intrinsic parameters governing the fiber and matrix behavior and the fiber/matrix interface is afterward retailed. At this stage, each constituent is assumed to be brittle elastic. Then, simulations of longitudinal and transversal tensions but also of in plane and out of plane shearing are performed on the REV using DEM. The results are discussed and compared with those known for the literature. The capacity of the present DEM to capture the crack paths is particularly highlighted.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/93742015-01-01T00:00:00ZMAHEO, LaurentDAU, FrédéricANDRE, DamienCHARLES, Jean-LucIORDANOFF, IvanIn this article, the Discrete Element Method (DEM) is taking advantage for the damage modeling of a composite material. At this stage of work, a Representative Elementary Volume (REV) of an unidirectional composite material modeled in 3D is considered to prove the relevance of the approach. The interest to introduce the Discrete Elements (DE) on the scale of constituents (fiber and matrix) is to be able to report local mechanisms of degradation such as the matrix micro-fissuring, the fiber/matrix debonding and the break of fiber, appropriate to this type of material. The short-term objective is to use this DEM modeling to treat locally the damages induced by an impact loading associated with a conventional Finite Element modeling beyond the damaged zone. First, the geometrical modelings of the fiber and the matrix are presented. The phase of calibration of the DE model intrinsic parameters governing the fiber and matrix behavior and the fiber/matrix interface is afterward retailed. At this stage, each constituent is assumed to be brittle elastic. Then, simulations of longitudinal and transversal tensions but also of in plane and out of plane shearing are performed on the REV using DEM. The results are discussed and compared with those known for the literature. The capacity of the present DEM to capture the crack paths is particularly highlighted.Méthode des éléments discrets : des problèmes multi-corps aux problèmes d’endommagement dynamique complexes.
http://hdl.handle.net/10985/8255
Méthode des éléments discrets : des problèmes multi-corps aux problèmes d’endommagement dynamique complexes.
IORDANOFF, Ivan; ANDRE, Damien; CHARLES, Jean-Luc; VIOT, Philippe
La méthode des éléments discrets est présentée comme une alternative aux approches de type mécanique des milieux continus pour aborder certains aspects liés aux problèmes dynamiques, notamment la multi fracturation de matériaux fragiles. Des exemples liés à l’usinage des composites et au surfaçage du verre sont présentés. Une extension de la méthode pour étudier le comportement des mousses est ensuite proposée et imagée par des premiers résultats.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/10985/82552011-01-01T00:00:00ZIORDANOFF, IvanANDRE, DamienCHARLES, Jean-LucVIOT, PhilippeLa méthode des éléments discrets est présentée comme une alternative aux approches de type mécanique des milieux continus pour aborder certains aspects liés aux problèmes dynamiques, notamment la multi fracturation de matériaux fragiles. Des exemples liés à l’usinage des composites et au surfaçage du verre sont présentés. Une extension de la méthode pour étudier le comportement des mousses est ensuite proposée et imagée par des premiers résultats.Discrete element method to simulate continuous material by using the cohesive beam model
http://hdl.handle.net/10985/6516
Discrete element method to simulate continuous material by using the cohesive beam model
ANDRE, Damien; IORDANOFF, Ivan; CHARLES, Jean-Luc; NEAUPORT, Jérôme
The mechanical behavior of materials is usually simulated by the continuous mechanics approach. However, simulation of non-continuous phenomena like multi fracturing is not well adapted to a continuous description. In this case, the discrete element method (DEM) is a good alternative because it naturally takes into account discontinuities. Many researchers have shown interest in this approach for wear and fracture simulation. The problem is that, while DEM is well adapted to simulate discontinuities, it is not suitable to simulate continuous behavior. In problems of wear or fracture, material is composed of continuous parts and discontinuous interfaces. The aim of the present work is to improve the ability of DEM to simulate the continuous part of the material using cohesive bond model. Continuous mechanics laws cannot be used directly within a DEM formulation. A second difficulty is that the volume between the discrete elements creates an artificial void inside thematerial. This paper proposes a methodology that tackles these theoretical difficulties and simulates, using a discrete element model, any material defined by a Young’s modulus, Poisson’s ratio and density, to fit the static and dynamic mechanical behavior of the material. The chosen cohesive beam model is shown to be robust concerning the influence of the discrete element sizes. This method is applied to a material which can be considered as perfectly elastic: fused silica.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/10985/65162012-01-01T00:00:00ZANDRE, DamienIORDANOFF, IvanCHARLES, Jean-LucNEAUPORT, JérômeThe mechanical behavior of materials is usually simulated by the continuous mechanics approach. However, simulation of non-continuous phenomena like multi fracturing is not well adapted to a continuous description. In this case, the discrete element method (DEM) is a good alternative because it naturally takes into account discontinuities. Many researchers have shown interest in this approach for wear and fracture simulation. The problem is that, while DEM is well adapted to simulate discontinuities, it is not suitable to simulate continuous behavior. In problems of wear or fracture, material is composed of continuous parts and discontinuous interfaces. The aim of the present work is to improve the ability of DEM to simulate the continuous part of the material using cohesive bond model. Continuous mechanics laws cannot be used directly within a DEM formulation. A second difficulty is that the volume between the discrete elements creates an artificial void inside thematerial. This paper proposes a methodology that tackles these theoretical difficulties and simulates, using a discrete element model, any material defined by a Young’s modulus, Poisson’s ratio and density, to fit the static and dynamic mechanical behavior of the material. The chosen cohesive beam model is shown to be robust concerning the influence of the discrete element sizes. This method is applied to a material which can be considered as perfectly elastic: fused silica.Simulation du comportement de la silice sous indentation Vickers par la méthode des elements discrets: densification et mécanismes de fissuration
http://hdl.handle.net/10985/8295
Simulation du comportement de la silice sous indentation Vickers par la méthode des elements discrets: densification et mécanismes de fissuration
JEBAHI, Mohamed; ANDRE, Damien; DAU, Frédéric; CHARLES, Jean-Luc; IORDANOFF, Ivan
The indentation response of glasses can be classified into three classes : normal, anomalous and intermediate depending on the deformation mechanism and the cracking response. Silica glass, as a typical anomalous glass, deforms primarily by densification and has a strong tendency to form cone cracks that can accompany median, radial and lateral cracks when indented with a Vickers tip. This is due to its propensity to deform elastically by resisting plastic flow. Several investigations of this anomalous behavior can be found in the literature. The present paper serves to corroborate these results numerically using the discrete element method. A new pressure-densification model involving the discrete element method (DEM) is developed that allows for a quantitative estimate of the densification under very high pressure. This model is then used to simulate the Vickers indentation response of silica glass under various indentation forces. The numerical results obtained compare favorably with past experimental results.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/82952013-01-01T00:00:00ZJEBAHI, MohamedANDRE, DamienDAU, FrédéricCHARLES, Jean-LucIORDANOFF, IvanThe indentation response of glasses can be classified into three classes : normal, anomalous and intermediate depending on the deformation mechanism and the cracking response. Silica glass, as a typical anomalous glass, deforms primarily by densification and has a strong tendency to form cone cracks that can accompany median, radial and lateral cracks when indented with a Vickers tip. This is due to its propensity to deform elastically by resisting plastic flow. Several investigations of this anomalous behavior can be found in the literature. The present paper serves to corroborate these results numerically using the discrete element method. A new pressure-densification model involving the discrete element method (DEM) is developed that allows for a quantitative estimate of the densification under very high pressure. This model is then used to simulate the Vickers indentation response of silica glass under various indentation forces. The numerical results obtained compare favorably with past experimental results.Using the discrete element method to simulate brittle fracture in the indentation of a silica glass with a blunt indenter
http://hdl.handle.net/10985/8263
Using the discrete element method to simulate brittle fracture in the indentation of a silica glass with a blunt indenter
ANDRE, Damien; JEBAHI, Mohamed; IORDANOFF, Ivan; CHARLES, Jean-Luc; NEAUPORT, Jérôme
The mechanical behavior of materials is usually simulated by a continuous mechanics approach. However, noncontinuous phenomena such as multi-fracturing cannot be accurately simulated using a continuous description. The discrete element method (DEM) naturally accounts for discontinuities and is therefore a good alternative to the continuum approach. This study continues previous work in which a DEM model was developed to quantitatively simulate an elastic material with the cohesive beam bond model. The simulation of brittle cracks is now tackled. This goal is attained by computing a failure criterion based on an equivalent hydrostatic stress. This microscopic criterion is then calibrated to fit experimental values of the macroscopic failure stress. The simulation results are compared to experimental results of indentation tests in which a spherical indenter is used to load a silica glass, which is considered to be a perfectly brittle elastic material.
This work was supported by the Conseil Régional d’Aquitaine and was conducted under the auspices of the Etude et Formation en Surfacage Optique (EFESO 2) project. The developments realized in this project were implemented in the GranOO1 project.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/82632013-01-01T00:00:00ZANDRE, DamienJEBAHI, MohamedIORDANOFF, IvanCHARLES, Jean-LucNEAUPORT, JérômeThe mechanical behavior of materials is usually simulated by a continuous mechanics approach. However, noncontinuous phenomena such as multi-fracturing cannot be accurately simulated using a continuous description. The discrete element method (DEM) naturally accounts for discontinuities and is therefore a good alternative to the continuum approach. This study continues previous work in which a DEM model was developed to quantitatively simulate an elastic material with the cohesive beam bond model. The simulation of brittle cracks is now tackled. This goal is attained by computing a failure criterion based on an equivalent hydrostatic stress. This microscopic criterion is then calibrated to fit experimental values of the macroscopic failure stress. The simulation results are compared to experimental results of indentation tests in which a spherical indenter is used to load a silica glass, which is considered to be a perfectly brittle elastic material.A quantitative discrete element model to investigate sub-surface damage due to surface polishing
http://hdl.handle.net/10985/8265
A quantitative discrete element model to investigate sub-surface damage due to surface polishing
ANDRE, Damien; IORDANOFF, Ivan; CHARLES, Jean-Luc; NEAUPORT, Jérôme
This work is a continuation of a previous study that investigated sub-surface damage in silica glass due to surface polishing. In this previous study, discrete element models have shown qualitatively good agreement with experiments. The presented work propose a model allowing quantitative results by focusing on the continuous part of the problem. Special attemption was given to the discrete element model of silica glass considered as perfectly isotropic, elastic and brittle. To validate this approach, numerical results are compared to experimental data from literature.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/10985/82652012-01-01T00:00:00ZANDRE, DamienIORDANOFF, IvanCHARLES, Jean-LucNEAUPORT, JérômeThis work is a continuation of a previous study that investigated sub-surface damage in silica glass due to surface polishing. In this previous study, discrete element models have shown qualitatively good agreement with experiments. The presented work propose a model allowing quantitative results by focusing on the continuous part of the problem. Special attemption was given to the discrete element model of silica glass considered as perfectly isotropic, elastic and brittle. To validate this approach, numerical results are compared to experimental data from literature.Modèle par éléments discrets pour l’étude du comportement dynamique d’un matériau élastique.
http://hdl.handle.net/10985/8254
Modèle par éléments discrets pour l’étude du comportement dynamique d’un matériau élastique.
ANDRE, Damien; IORDANOFF, Ivan; CHARLES, Jean-Luc; NEAUPORT, Jérome
Le comportement mécanique des matériaux est généralement simulé par des approches issues de la mécanique des milieux continus. Cependant, lorsqu’il s’agit de simuler des phénomènes de multi fissurations voir de multi fracturations, les modèles de la mécanique discrète s’avèrent mieux adaptés, car ils prennent en compte naturellement les discontinuités générées par les interfaces. La difficulté est alors de s’assurer qu’une approche par éléments discrets (DEM) permet bien de retrouver le comportement mécanique au sens de la mécanique des milieux continus. Cet article propose une méthodologie permettant, à partir des données connues du matériau à simuler (module de Young, coefficient de Poisson, célérité de propagation des ondes), de quantifier les paramètres « microscopiques » du modèle DEM.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/10985/82542011-01-01T00:00:00ZANDRE, DamienIORDANOFF, IvanCHARLES, Jean-LucNEAUPORT, JéromeLe comportement mécanique des matériaux est généralement simulé par des approches issues de la mécanique des milieux continus. Cependant, lorsqu’il s’agit de simuler des phénomènes de multi fissurations voir de multi fracturations, les modèles de la mécanique discrète s’avèrent mieux adaptés, car ils prennent en compte naturellement les discontinuités générées par les interfaces. La difficulté est alors de s’assurer qu’une approche par éléments discrets (DEM) permet bien de retrouver le comportement mécanique au sens de la mécanique des milieux continus. Cet article propose une méthodologie permettant, à partir des données connues du matériau à simuler (module de Young, coefficient de Poisson, célérité de propagation des ondes), de quantifier les paramètres « microscopiques » du modèle DEM.