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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.Discrete Element Method, a Tool to Investigate Complex Material Behaviour in Material Forming
http://hdl.handle.net/10985/8256
Discrete Element Method, a Tool to Investigate Complex Material Behaviour in Material Forming
IORDANOFF, Ivan; ILIESCU, Daniel; CHARLES, Jean-Luc; NEAUPORT, Jérôme
Discrete Model is based on the description of the physical state (velocity, position, temperature, magnetic moment, electric potential ..) of a large number of discrete elements that form the media to be studied. It is not based on a continuous description of the media. Then, it is particularly well adapted to describe media evolution driven by discontinuous phenomena : - multi fracturation problems like abrasion process and composite machining, - description of multi fracturation followed by debris flow like wear study Recently, the use of discrete model has been widened to face problem encountered with complex rheological behavior and/or multi-physical behavior. Multi-physical problems face complex mathematical formulation because of the mixing of different families of differential equations when continuous approach is chosen. With the discrete model, each particle has a physical state and state evolution is due to local physical particle interaction: it is often much simple to write. Some attempt to study complex multi-physical problems has been recently presented: - thermal study of a contact and how dissymmetry appears in an apparently symmetrical problem, - study of Friction Stir Welding. This work outlines how discrete element model can be a useful tool in the simulation of material forming. Example is given on abrasion process and machining of composite.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10985/82562010-01-01T00:00:00ZIORDANOFF, IvanILIESCU, DanielCHARLES, Jean-LucNEAUPORT, JérômeDiscrete Model is based on the description of the physical state (velocity, position, temperature, magnetic moment, electric potential ..) of a large number of discrete elements that form the media to be studied. It is not based on a continuous description of the media. Then, it is particularly well adapted to describe media evolution driven by discontinuous phenomena : - multi fracturation problems like abrasion process and composite machining, - description of multi fracturation followed by debris flow like wear study Recently, the use of discrete model has been widened to face problem encountered with complex rheological behavior and/or multi-physical behavior. Multi-physical problems face complex mathematical formulation because of the mixing of different families of differential equations when continuous approach is chosen. With the discrete model, each particle has a physical state and state evolution is due to local physical particle interaction: it is often much simple to write. Some attempt to study complex multi-physical problems has been recently presented: - thermal study of a contact and how dissymmetry appears in an apparently symmetrical problem, - study of Friction Stir Welding. This work outlines how discrete element model can be a useful tool in the simulation of material forming. Example is given on abrasion process and machining of composite.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.The GranOO workbench, a new tool for developing discrete element simulations, and its application to tribological problems
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.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.