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The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sun, 28 Feb 2021 14:02:19 GMT2021-02-28T14:02:19ZProcédé de perçage par laser : Comparaison entre des données expérimentales et une simulation 2D basée sur la méthode CNEM
http://hdl.handle.net/10985/7637
Procédé de perçage par laser : Comparaison entre des données expérimentales et une simulation 2D basée sur la méthode CNEM
GIRARDOT, Jérémie; RANC, Nicolas; SCHNEIDER, Matthieu; LORONG, Philippe; ILLOUL, Lounès; BERTHE, Laurent; FAVIER, Véronique
This work presents a numerical alternative for the laser drilling simulation problem. Using finite element method is difficult to simulate the hole propagation over time, especially because of moving boundaries due to a fast phase change and high thermal gradients. First, the physical process of the laser drilling and the modeling equations are clarified. Then a comparison between experimental data and simulation outputs regarding the laser peak power is investigated.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/76372013-01-01T00:00:00ZGIRARDOT, JérémieRANC, NicolasSCHNEIDER, MatthieuLORONG, PhilippeILLOUL, LounèsBERTHE, LaurentFAVIER, VéroniqueThis work presents a numerical alternative for the laser drilling simulation problem. Using finite element method is difficult to simulate the hole propagation over time, especially because of moving boundaries due to a fast phase change and high thermal gradients. First, the physical process of the laser drilling and the modeling equations are clarified. Then a comparison between experimental data and simulation outputs regarding the laser peak power is investigated.A promising way to model damage in composite and dry fabrics using a Discrete Element Method (DEM)
http://hdl.handle.net/10985/10234
A promising way to model damage in composite and dry fabrics using a Discrete Element Method (DEM)
DAU, Frédéric; MAHEO, Laurent; LE, Ba Danh; GIRARDOT, Jérémie
A promising way to model fracture mechanics with the use of an original Discrete Element Method (DEM) is proposed. After proving the ability of the method to capture kinetic damage induced by cracking phenomena in brittle materials such as silica [1], taking advantage of the method for composite materials applications is the main purpose of this work. This paper highlights recent developments to prove capabilities of the DEM and to give some answers to challenges : i) use the present DEM to model damage mechanisms (matrix cracking, debonding, fiber break and delamination) in a composite material ii) deal with impact applications using the DEM. All developments are made in the home made software GRANOO (GRANular Objet Oriented) [2]. The capability of the DEM to model matrix cracking, debonding and fiber break is first demonstrated on a so-called representative elementary volume (REV) made of a fiber flooded in a matrix. Modelize the REV with DEM and retrieve suitable homogenized properties is the first challenge reached. Secondly, the ability of the method to capture matrix cracking, debonding and fiber break is qualitatively demonstrated through basic static simulations performed on the REV. The ongoing developments to improve are presented. Then, the Double Cantilever Beam (DCB) test using Discrete Element (DE) is investigated. Contact cohesive laws are identified from experiments and implemented in GRANOO. Simulations of DCB test using DEM are then performed. Results are discussed and ways of improvements are proposed. Finally, the ability of the DEM to simulate impact damage on textile is pointed out. Numerical investigations are based on Ha-Minh & co. Works in [3, 4] taken for reference. The weaving is exactly reproduced with DE. The contact between yarns is naturally taken into account in the DEM. The promising results are commented and the on going developments are exposed.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10985/102342014-01-01T00:00:00ZDAU, FrédéricMAHEO, LaurentLE, Ba DanhGIRARDOT, JérémieA promising way to model fracture mechanics with the use of an original Discrete Element Method (DEM) is proposed. After proving the ability of the method to capture kinetic damage induced by cracking phenomena in brittle materials such as silica [1], taking advantage of the method for composite materials applications is the main purpose of this work. This paper highlights recent developments to prove capabilities of the DEM and to give some answers to challenges : i) use the present DEM to model damage mechanisms (matrix cracking, debonding, fiber break and delamination) in a composite material ii) deal with impact applications using the DEM. All developments are made in the home made software GRANOO (GRANular Objet Oriented) [2]. The capability of the DEM to model matrix cracking, debonding and fiber break is first demonstrated on a so-called representative elementary volume (REV) made of a fiber flooded in a matrix. Modelize the REV with DEM and retrieve suitable homogenized properties is the first challenge reached. Secondly, the ability of the method to capture matrix cracking, debonding and fiber break is qualitatively demonstrated through basic static simulations performed on the REV. The ongoing developments to improve are presented. Then, the Double Cantilever Beam (DCB) test using Discrete Element (DE) is investigated. Contact cohesive laws are identified from experiments and implemented in GRANOO. Simulations of DCB test using DEM are then performed. Results are discussed and ways of improvements are proposed. Finally, the ability of the DEM to simulate impact damage on textile is pointed out. Numerical investigations are based on Ha-Minh & co. Works in [3, 4] taken for reference. The weaving is exactly reproduced with DE. The contact between yarns is naturally taken into account in the DEM. The promising results are commented and the on going developments are exposed.Reevaluation of the diametral compression test for tablets using the flattened disc geometry
http://hdl.handle.net/10985/11248
Reevaluation of the diametral compression test for tablets using the flattened disc geometry
MAZEL, Vincent; GUERARD, Sandra; CROQUELOIS, Benjamin; KOPP, Jean-Benoit; GIRARDOT, Jérémie; DIARRA, Harona; BUSIGNIES, Virginie; TCHORELOFF, Pierre
Mechanical strength is an important critical quality attribute for tablets. It is classically measured, in the pharmaceutical field, using the diametral compression test. Nevertheless, due to small contact area between the tablet and the platens, some authors suggested that during the test, the failure could occur in tension away from the center which would invalidate the test and the calculation of the tensile strength. In this study, the flattened disc geometry was used as an alternative to avoid contact problems. The diametral compression on both flattened and standard geometries was first studied using finite element method (FEM) simulation. It was found that, for the flattened geometry, both maximum tensile strain and stress were located at the center of the tablet, which was not the case for the standard geometry. Experimental observations using digital image correlation (DIC) confirmed the numerical results. The experimental tensile strength obtained using both geometries were compared and it was found that the standard geometry always gave lower tensile strength than the flattened geometry. Finally, high-speed video capture of the test made it possible to detect that for the standard geometry the crack initiation was always away from the center of the tablet.
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/10985/112482016-01-01T00:00:00ZMAZEL, VincentGUERARD, SandraCROQUELOIS, BenjaminKOPP, Jean-BenoitGIRARDOT, JérémieDIARRA, HaronaBUSIGNIES, VirginieTCHORELOFF, PierreMechanical strength is an important critical quality attribute for tablets. It is classically measured, in the pharmaceutical field, using the diametral compression test. Nevertheless, due to small contact area between the tablet and the platens, some authors suggested that during the test, the failure could occur in tension away from the center which would invalidate the test and the calculation of the tensile strength. In this study, the flattened disc geometry was used as an alternative to avoid contact problems. The diametral compression on both flattened and standard geometries was first studied using finite element method (FEM) simulation. It was found that, for the flattened geometry, both maximum tensile strain and stress were located at the center of the tablet, which was not the case for the standard geometry. Experimental observations using digital image correlation (DIC) confirmed the numerical results. The experimental tensile strength obtained using both geometries were compared and it was found that the standard geometry always gave lower tensile strength than the flattened geometry. Finally, high-speed video capture of the test made it possible to detect that for the standard geometry the crack initiation was always away from the center of the tablet.Simulation of the laser drilling process with the Constraint Natural Element Method
http://hdl.handle.net/10985/9954
Simulation of the laser drilling process with the Constraint Natural Element Method
GIRARDOT, Jérémie; ILLOUL, Lounès; LORONG, Philippe; RANC, Nicolas; SCHNEIDER, Matthieu; BERTHE, Laurent; FAVIER, Véronique
These works present a numerical alternative to the simulation of the laser drilling process. The use of the finite element method to modeling the hole creation during a laser pulse shows difficulties in front of a moving boundary problem. This moving boundary is induced by a fast phase transformation and also by high thermal gradient. The C-NEM (Constraint Natural Element Method) was tested in order to solve these numerical difficulties and to use the high potential of this original method. The physical interaction of the laser drilling will be reminded and the chosen mathematical model will be specified. A simulation was made with the data for pure iron in order to validate the numerical choice.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/10985/99542012-01-01T00:00:00ZGIRARDOT, JérémieILLOUL, LounèsLORONG, PhilippeRANC, NicolasSCHNEIDER, MatthieuBERTHE, LaurentFAVIER, VéroniqueThese works present a numerical alternative to the simulation of the laser drilling process. The use of the finite element method to modeling the hole creation during a laser pulse shows difficulties in front of a moving boundary problem. This moving boundary is induced by a fast phase transformation and also by high thermal gradient. The C-NEM (Constraint Natural Element Method) was tested in order to solve these numerical difficulties and to use the high potential of this original method. The physical interaction of the laser drilling will be reminded and the chosen mathematical model will be specified. A simulation was made with the data for pure iron in order to validate the numerical choice.Modeling laser drilling in percussion regime using constraint natural element method
http://hdl.handle.net/10985/11714
Modeling laser drilling in percussion regime using constraint natural element method
GIRARDOT, Jérémie; LORONG, Philippe; ILLOUL, Lounès; RANC, Nicolas; SCHNEIDER, Matthieu; FAVIER, Véronique
The laser drilling process is the main process used in machining procedures on aeronautic engines, especially in the cooling parts. The industrial problematic is to reduce geometrical deviations of the holes and defects during manufacturing. The interaction between a laser beam and an absorbent metallic matter in the laser drilling regime involves thermal and hydrodynamical phenomenon. Their role on the drilling is not yet completely understood and a realistic simulation of the process could contribute to a better understanding of these phenomenon. The simulation of such process induces strong numerical difficulties. This work presents a physical model combined with the use of the original Constraint Natural Element Method to simulate the laser drilling. The physical model includes solid/liquid and liquid/vapor phase transformations, the liquid ejection and the convective and conductive thermal exchanges. It is the first time that all these phenomena are included in a modelling and numerically solved in a 2D axisymmmetric problem. Simulations results predict most of measurements (hole geometry, velocity of the liquid ejection and laser drilling velocity) without adjusting any parameters
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/117142017-01-01T00:00:00ZGIRARDOT, JérémieLORONG, PhilippeILLOUL, LounèsRANC, NicolasSCHNEIDER, MatthieuFAVIER, VéroniqueThe laser drilling process is the main process used in machining procedures on aeronautic engines, especially in the cooling parts. The industrial problematic is to reduce geometrical deviations of the holes and defects during manufacturing. The interaction between a laser beam and an absorbent metallic matter in the laser drilling regime involves thermal and hydrodynamical phenomenon. Their role on the drilling is not yet completely understood and a realistic simulation of the process could contribute to a better understanding of these phenomenon. The simulation of such process induces strong numerical difficulties. This work presents a physical model combined with the use of the original Constraint Natural Element Method to simulate the laser drilling. The physical model includes solid/liquid and liquid/vapor phase transformations, the liquid ejection and the convective and conductive thermal exchanges. It is the first time that all these phenomena are included in a modelling and numerically solved in a 2D axisymmmetric problem. Simulations results predict most of measurements (hole geometry, velocity of the liquid ejection and laser drilling velocity) without adjusting any parametersSimulation numérique du perçage laser par la méthode C-NEM
http://hdl.handle.net/10985/9956
Simulation numérique du perçage laser par la méthode C-NEM
GIRARDOT, Jérémie; ILLOUL, Lounès; LORONG, Philippe; RANC, Nicolas; SCHNEIDER, Matthieu; BERTHE, Laurent; FAVIER, Véronique
Ces travaux présentent une alternative numérique au problème de simulation du procédé de perçage par laser. L’utilisation des éléments finis pour modéliser la propagation du trou au cours du temps montre des limites face à un problème de frontières mobiles induit par un changement de phase rapide et des forts gradients thermiques. L’utilisation d’un code C-NEM a donc été testé avec comme objectif de résoudre ces difficultés numériques et d’utiliser le fort potentiel de cette méthode originale. Le principe physique du perçage laser sera rappelé et le modèle mathématique choisi pour le modéliser sera précisé. Un cas test de simulation a été réalisé avec les grandeurs physiques du fer pur afin de valider le choix du code C-NEM.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/10985/99562012-01-01T00:00:00ZGIRARDOT, JérémieILLOUL, LounèsLORONG, PhilippeRANC, NicolasSCHNEIDER, MatthieuBERTHE, LaurentFAVIER, VéroniqueCes travaux présentent une alternative numérique au problème de simulation du procédé de perçage par laser. L’utilisation des éléments finis pour modéliser la propagation du trou au cours du temps montre des limites face à un problème de frontières mobiles induit par un changement de phase rapide et des forts gradients thermiques. L’utilisation d’un code C-NEM a donc été testé avec comme objectif de résoudre ces difficultés numériques et d’utiliser le fort potentiel de cette méthode originale. Le principe physique du perçage laser sera rappelé et le modèle mathématique choisi pour le modéliser sera précisé. Un cas test de simulation a été réalisé avec les grandeurs physiques du fer pur afin de valider le choix du code C-NEM.Modeling laser drilling in percussion regime using constraint natural element method
http://hdl.handle.net/10985/10594
Modeling laser drilling in percussion regime using constraint natural element method
GIRARDOT, Jérémie; LORONG, Philippe; ILLOUL, Lounès; RANC, Nicolas; SCHNEIDER, Matthieu; FAVIER, Véronique
The laser drilling process is the main process used in machining procedures on aeronautic engines, espe- cially in the cooling parts. The industrial problematic is to reduce geometrical deviations of the holes and defects dur- ing manufacturing. The interaction between a laser beam and an absorbent metallic matter in the laser drilling regime involves thermal and hydrodynamical phenomenon. Their role on the drilling is not yet completely understood and a realistic simulation of the process could contribute to a better understanding of these phenomenon. The simula- tion of such process induces strong numerical difficulties. This work presents a physical model combined with the use of the original Constraint Natural Element Method to simulate the laser drilling. The physical model includes solid/liquid and liquid/vapor phase transformations, the liq- uid ejection and the convective and conductive thermal exchanges. It is the first time that all these phenomena are included in a modelling and numerically solved in a 2D axisymmmetric problem. Simulations results predict most of measurements (hole geometry, velocity of the liquid ejection and laser drilling velocity) without adjusting any parameters.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/105942015-01-01T00:00:00ZGIRARDOT, JérémieLORONG, PhilippeILLOUL, LounèsRANC, NicolasSCHNEIDER, MatthieuFAVIER, VéroniqueThe laser drilling process is the main process used in machining procedures on aeronautic engines, espe- cially in the cooling parts. The industrial problematic is to reduce geometrical deviations of the holes and defects dur- ing manufacturing. The interaction between a laser beam and an absorbent metallic matter in the laser drilling regime involves thermal and hydrodynamical phenomenon. Their role on the drilling is not yet completely understood and a realistic simulation of the process could contribute to a better understanding of these phenomenon. The simula- tion of such process induces strong numerical difficulties. This work presents a physical model combined with the use of the original Constraint Natural Element Method to simulate the laser drilling. The physical model includes solid/liquid and liquid/vapor phase transformations, the liq- uid ejection and the convective and conductive thermal exchanges. It is the first time that all these phenomena are included in a modelling and numerically solved in a 2D axisymmmetric problem. Simulations results predict most of measurements (hole geometry, velocity of the liquid ejection and laser drilling velocity) without adjusting any parameters.Investigation of delamination mechanisms during a laser drilling on a cobalt-base superalloy
http://hdl.handle.net/10985/8106
Investigation of delamination mechanisms during a laser drilling on a cobalt-base superalloy
GIRARDOT, Jérémie; SCHNEIDER, Matthieu; BERTHE, Laurent; FAVIER, Véronique
Temperatures in the high pressure chamber of aircraft engines are continuously increasing to improve the engine efﬁciency. As a result, constitutive materials such as cobalt and nickel-base superalloys need to be thermally protected. The ﬁrst protection is a ceramic thermal barrier coating (TBC) cast on all the hot gas-exposed structure. The second protection is provided by a cool air layer realized by the use of a thousand of drills on the parts where a cool air is ﬂowing through. The laser drilling process is used to realize these holes at acute angles. It has been shown on coated single crystal nickel-base superalloy that the laser drilling process causes an interfacial cracking (also called delamination), detected by a cross section observation. The present work aims at characterizing interfacial cracking induced by laser drilling on coated cobalt-base super alloy. On the one hand, this work attempted to quantify the crack by several microscopic observations with regards to the most signiﬁcant process parameters related as the angle beam. On the other hand, we studied the difference of the laser/ceramic and the laser/substrate interaction with real time observation by using a fast movie camera.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/81062013-01-01T00:00:00ZGIRARDOT, JérémieSCHNEIDER, MatthieuBERTHE, LaurentFAVIER, VéroniqueTemperatures in the high pressure chamber of aircraft engines are continuously increasing to improve the engine efﬁciency. As a result, constitutive materials such as cobalt and nickel-base superalloys need to be thermally protected. The ﬁrst protection is a ceramic thermal barrier coating (TBC) cast on all the hot gas-exposed structure. The second protection is provided by a cool air layer realized by the use of a thousand of drills on the parts where a cool air is ﬂowing through. The laser drilling process is used to realize these holes at acute angles. It has been shown on coated single crystal nickel-base superalloy that the laser drilling process causes an interfacial cracking (also called delamination), detected by a cross section observation. The present work aims at characterizing interfacial cracking induced by laser drilling on coated cobalt-base super alloy. On the one hand, this work attempted to quantify the crack by several microscopic observations with regards to the most signiﬁcant process parameters related as the angle beam. On the other hand, we studied the difference of the laser/ceramic and the laser/substrate interaction with real time observation by using a fast movie camera.A novel DEM approach for modeling brittle elastic media based on distinct lattice spring model
http://hdl.handle.net/10985/15000
A novel DEM approach for modeling brittle elastic media based on distinct lattice spring model
ANDRE, Damien; GIRARDOT, Jérémie; HUBERT, Cédric
The Discrete Element Method (DEM), also known as Distinct Element Method (DEM), is extensively used to study divided media such as granular materials. When brittle failure occurs in continuum such as concrete or ceramics, the considered media can be viewed as divided. In such cases, DEM offers an interesting way to study and simulate complex fracture phenomena such as crack branching, crack extension, crack deviation under coupled mode or crack lip closure with friction. The fundamental difficulty with DEM is the inability of the method to deal directly with the constitutive equations of continuum mechanics. DEM uses forcedisplacement interaction laws between particles instead of stress-strain relationships. Generally, this difficulty is bypassed by using inverse methods, also known as calibration processes, able to translate macroscopic stress-strain relationships into local force-displacement interaction laws compatible within DEM frameworks. However, this calibration process may be fastidious and really hard to manage. The presented work proposes to improve the Distinct Lattice Spring Model in order to deal with non-regular domains, by using Voronoi cells, which allows to completely fill the volume space of discrete domains. With this approach, the rotational effects must be included in the contact formulation, which enables the management of large rigid body rotations. This work also introduces a simple method to manage brittle fracture. Using non-regular domains avoids the cracks paths conditioning, and allows to reproduce quantitatively the Brazilian test, very popular in the rock mechanics community
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/10985/150002019-01-01T00:00:00ZANDRE, DamienGIRARDOT, JérémieHUBERT, CédricThe Discrete Element Method (DEM), also known as Distinct Element Method (DEM), is extensively used to study divided media such as granular materials. When brittle failure occurs in continuum such as concrete or ceramics, the considered media can be viewed as divided. In such cases, DEM offers an interesting way to study and simulate complex fracture phenomena such as crack branching, crack extension, crack deviation under coupled mode or crack lip closure with friction. The fundamental difficulty with DEM is the inability of the method to deal directly with the constitutive equations of continuum mechanics. DEM uses forcedisplacement interaction laws between particles instead of stress-strain relationships. Generally, this difficulty is bypassed by using inverse methods, also known as calibration processes, able to translate macroscopic stress-strain relationships into local force-displacement interaction laws compatible within DEM frameworks. However, this calibration process may be fastidious and really hard to manage. The presented work proposes to improve the Distinct Lattice Spring Model in order to deal with non-regular domains, by using Voronoi cells, which allows to completely fill the volume space of discrete domains. With this approach, the rotational effects must be included in the contact formulation, which enables the management of large rigid body rotations. This work also introduces a simple method to manage brittle fracture. Using non-regular domains avoids the cracks paths conditioning, and allows to reproduce quantitatively the Brazilian test, very popular in the rock mechanics communityMulti-scale foam : 3D structure/compressive behaviour relationship of agglomerated cork
http://hdl.handle.net/10985/17576
Multi-scale foam : 3D structure/compressive behaviour relationship of agglomerated cork
LE BARBENCHON, Louise; GIRARDOT, Jérémie; KOPP, Jean-Benoit; VIOT, Philippe
This study focuses on the microstructural aspects of a cork-based by-product known as agglomerated cork and its influence on the compressive mechanical behaviour. The material consists in granulates of a natural polymeric foam - cork - mixed together with a small quantity of a bio-sourced resin. Optical and scanning electron microscopy (SEM) are first used to investigate on the bead geometry and placement and interfaces arrangement. Then X-ray computed tomography allows to study the spatial arrangement of agglomerated cork microstructure and hence to complete and confirm 2D observations. 2D and 3D observations show a transverse anisotropic material which is confirmed by the mechanical tests. SEM pictures demonstrate an intricate and heterogeneous material. Microtomography confirms the presence of macroporosities between cork granulates having a mean volume around 0.1 mm 3 . Cork cell specific geometry is also confirmed. The volume of those cells lies around 10 −5 mm 3 . Finally quasi-static compression tests are run to establish a link between microstructure and mechanical behaviour thanks to digital image correlation (DIC). Cork agglomerate demonstrates strong strain localisation at its surface caused by its multi-scale structure.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/10985/175762019-01-01T00:00:00ZLE BARBENCHON, LouiseGIRARDOT, JérémieKOPP, Jean-BenoitVIOT, PhilippeThis study focuses on the microstructural aspects of a cork-based by-product known as agglomerated cork and its influence on the compressive mechanical behaviour. The material consists in granulates of a natural polymeric foam - cork - mixed together with a small quantity of a bio-sourced resin. Optical and scanning electron microscopy (SEM) are first used to investigate on the bead geometry and placement and interfaces arrangement. Then X-ray computed tomography allows to study the spatial arrangement of agglomerated cork microstructure and hence to complete and confirm 2D observations. 2D and 3D observations show a transverse anisotropic material which is confirmed by the mechanical tests. SEM pictures demonstrate an intricate and heterogeneous material. Microtomography confirms the presence of macroporosities between cork granulates having a mean volume around 0.1 mm 3 . Cork cell specific geometry is also confirmed. The volume of those cells lies around 10 −5 mm 3 . Finally quasi-static compression tests are run to establish a link between microstructure and mechanical behaviour thanks to digital image correlation (DIC). Cork agglomerate demonstrates strong strain localisation at its surface caused by its multi-scale structure.