SAMSAM captures, stores, indexes, preserves, and distributes digital research material.http://sam.ensam.eu:802017-06-22T12:33:46Z2017-06-22T12:33:46ZPrediction of Localized Necking Based on Crystal Plasticity: Comparison of Bifurcation and Imperfection ApproachesAKPAMA, HolanyoBEN BETTAIEB, MohamedABED-MERAIM, Faridhttp://hdl.handle.net/10985/118582017-06-22T00:16:59Z2016-10-17T00:00:00ZPrediction of Localized Necking Based on Crystal Plasticity: Comparison of Bifurcation and Imperfection Approaches
AKPAMA, Holanyo; BEN BETTAIEB, Mohamed; ABED-MERAIM, Farid
In the present work, a powerful modeling tool is developed to predict and analyze the onset of strain localization in polycrystalline aggregates. The predictions of localized necking are based on two plastic instability criteria, namely the bifurcation theory and the initial imperfection approach. In this tool, a micromechanical model, based on the self-consistent scale-transition scheme, is used to accurately derive the mechanical behavior of polycrystalline aggregates from that of their microscopic constituents (the single crystals). The mechanical behavior of the single crystals is developed within a large strain rate-independent constitutive framework. This micromechanical constitutive modeling takes into account the essential microstructure-related features that are relevant at the microscale. These microstructural aspects include key physical mechanisms, such as initial and induced crystallographic textures, morphological anisotropy and interactions between the grains and their surrounding medium. The developed tool is used to predict sheet metal formability through the concept of forming limit diagrams (FLDs). The results obtained by the self-consistent averaging scheme, in terms of predicted FLDs, are compared with those given by the more classical
full-constraint Taylor model. Moreover, the predictions obtained by the imperfection approach are systematically compared with those given by the bifurcation analysis, and it is demonstrated that the former tend to the latter in the limit of a vanishing size for the initial imperfection.
2016-10-17T00:00:00ZAKPAMA, HolanyoBEN BETTAIEB, MohamedABED-MERAIM, FaridIn the present work, a powerful modeling tool is developed to predict and analyze the onset of strain localization in polycrystalline aggregates. The predictions of localized necking are based on two plastic instability criteria, namely the bifurcation theory and the initial imperfection approach. In this tool, a micromechanical model, based on the self-consistent scale-transition scheme, is used to accurately derive the mechanical behavior of polycrystalline aggregates from that of their microscopic constituents (the single crystals). The mechanical behavior of the single crystals is developed within a large strain rate-independent constitutive framework. This micromechanical constitutive modeling takes into account the essential microstructure-related features that are relevant at the microscale. These microstructural aspects include key physical mechanisms, such as initial and induced crystallographic textures, morphological anisotropy and interactions between the grains and their surrounding medium. The developed tool is used to predict sheet metal formability through the concept of forming limit diagrams (FLDs). The results obtained by the self-consistent averaging scheme, in terms of predicted FLDs, are compared with those given by the more classical
full-constraint Taylor model. Moreover, the predictions obtained by the imperfection approach are systematically compared with those given by the bifurcation analysis, and it is demonstrated that the former tend to the latter in the limit of a vanishing size for the initial imperfection.Theoretical and numerical investigation of the impact of out-of-plane compressive stress on sheet metal formabilityBEN BETTAIEB, MohamedABED-MERAIM, Faridhttp://hdl.handle.net/10985/118572017-06-22T00:16:53Z2017-01-01T00:00:00ZTheoretical and numerical investigation of the impact of out-of-plane compressive stress on sheet metal formability
BEN BETTAIEB, Mohamed; ABED-MERAIM, Farid
In modern sheet metal forming processes, such as hydroforming and single point incremental forming, sheet metals are often subjected to out-of-plane compressive stresses in addition to traditional in-plane stresses. However, the effect of these out-of-plane stresses on the onset of plastic strain localization is not considered when classic necking criteria are used, as the latter are generally formulated based on the plane stress assumption. The main objective of the present investigation is to overcome this limitation by developing numerical tools and analytical relations that allow considering the influence of these compressive stresses on the prediction of localized necking. In the different tools developed, and for comparison purposes, finite strain versions of both the deformation theory of plasticity and the rigid-plastic flow theory are used to describe the mechanical behavior of the metal sheet. Furthermore, both the bifurcation theory and the initial imperfection approach are employed to predict the onset of strain localization. Various numerical predictions are reported to illustrate the effect of normal stress on the occurrence of localized necking in sheet metals. From these different results, it is clearly demonstrated that out-of-plane stresses may notably enhance sheet metal formability and, therefore, this property can be effectively used to avoid the initiation of early strain localization.
2017-01-01T00:00:00ZBEN BETTAIEB, MohamedABED-MERAIM, FaridIn modern sheet metal forming processes, such as hydroforming and single point incremental forming, sheet metals are often subjected to out-of-plane compressive stresses in addition to traditional in-plane stresses. However, the effect of these out-of-plane stresses on the onset of plastic strain localization is not considered when classic necking criteria are used, as the latter are generally formulated based on the plane stress assumption. The main objective of the present investigation is to overcome this limitation by developing numerical tools and analytical relations that allow considering the influence of these compressive stresses on the prediction of localized necking. In the different tools developed, and for comparison purposes, finite strain versions of both the deformation theory of plasticity and the rigid-plastic flow theory are used to describe the mechanical behavior of the metal sheet. Furthermore, both the bifurcation theory and the initial imperfection approach are employed to predict the onset of strain localization. Various numerical predictions are reported to illustrate the effect of normal stress on the occurrence of localized necking in sheet metals. From these different results, it is clearly demonstrated that out-of-plane stresses may notably enhance sheet metal formability and, therefore, this property can be effectively used to avoid the initiation of early strain localization.Localized necking predictions based on rate-independent self-consistent polycrystal plasticity: Bifurcation analysis versus imperfection approachAKPAMA, HolanyoBEN BETTAIEB, MohamedABED-MERAIM, Faridhttp://hdl.handle.net/10985/118562017-06-19T23:53:43Z2017-01-01T00:00:00ZLocalized necking predictions based on rate-independent self-consistent polycrystal plasticity: Bifurcation analysis versus imperfection approach
AKPAMA, Holanyo; BEN BETTAIEB, Mohamed; ABED-MERAIM, Farid
The present study focuses on the development of a relevant numerical tool for predicting
the onset of localized necking in polycrystalline aggregates. The latter are assumed to be representative of thin metal sheets. In this tool, a micromechanical model, based on the rate-independent self-consistent multi-scale scheme, is developed to accurately describe the mechanical behavior of polycrystalline aggregates from that of their single crystal constituents. In the current paper, the constitutive framework at the single crystal scale follows a finite strain formulation of the rate-independent theory of crystal elastoplasticity. To predict the occurrence of localized necking in polycrystalline aggregates, this micromechanical modeling is combined with two main strain localization approaches: the bifurcation analysis and the initial imperfection method. The formulation of both strain localization indicators takes into consideration the plane stress conditions to which thin metal sheets are subjected during deformation. From a numerical point of view, strain localization analysis with this crystal plasticity approach can be viewed as a strongly nonlinear problem. Hence, several numerical algorithms and techniques are developed and implemented in the aim of efficiently solving this non-linear problem. Various simulation results obtained by the application of the developed numerical tool are presented and extensively discussed. It is demonstrated from these results that the predictions obtained with the MarciniakeKuczynski procedure tend towards those yielded by the bifurcation theory, when the initial imperfection ratio tends towards zero. Furthermore, the above result is shown to be valid for both scale-transition schemes, namely the full-constraint Taylor model and self-consistent scheme.
2017-01-01T00:00:00ZAKPAMA, HolanyoBEN BETTAIEB, MohamedABED-MERAIM, FaridThe present study focuses on the development of a relevant numerical tool for predicting
the onset of localized necking in polycrystalline aggregates. The latter are assumed to be representative of thin metal sheets. In this tool, a micromechanical model, based on the rate-independent self-consistent multi-scale scheme, is developed to accurately describe the mechanical behavior of polycrystalline aggregates from that of their single crystal constituents. In the current paper, the constitutive framework at the single crystal scale follows a finite strain formulation of the rate-independent theory of crystal elastoplasticity. To predict the occurrence of localized necking in polycrystalline aggregates, this micromechanical modeling is combined with two main strain localization approaches: the bifurcation analysis and the initial imperfection method. The formulation of both strain localization indicators takes into consideration the plane stress conditions to which thin metal sheets are subjected during deformation. From a numerical point of view, strain localization analysis with this crystal plasticity approach can be viewed as a strongly nonlinear problem. Hence, several numerical algorithms and techniques are developed and implemented in the aim of efficiently solving this non-linear problem. Various simulation results obtained by the application of the developed numerical tool are presented and extensively discussed. It is demonstrated from these results that the predictions obtained with the MarciniakeKuczynski procedure tend towards those yielded by the bifurcation theory, when the initial imperfection ratio tends towards zero. Furthermore, the above result is shown to be valid for both scale-transition schemes, namely the full-constraint Taylor model and self-consistent scheme.Effect of kinematic hardening on localized necking in substrate-supported metal layersBEN BETTAIEB, MohamedABED-MERAIM, Faridhttp://hdl.handle.net/10985/118552017-06-19T23:53:48Z2017-01-01T00:00:00ZEffect of kinematic hardening on localized necking in substrate-supported metal layers
BEN BETTAIEB, Mohamed; ABED-MERAIM, Farid
Prediction of necking limits in thin substrate-supported metal layers, which are typically used as functional components in electronic devices, represents nowadays an ambitious challenge. The specific purpose of the current work is, first, to numerically investigate the effect of kinematic hardening on localized necking in a
freestanding metal layer. Second, the impact of adding a substrate layer on the ductility evolution of the resulting elastomer/metal bilayer will be analyzed. The materials in the metal and substrate layers are assumed to be isotropic, incompressible and strain-rate independent. The behavior of the metal layer is described by a rigid–plastic model with mixed (isotropic and kinematic) hardening. The isotropic hardening contribution is
modeled by the Hollomon law, while kinematic hardening is modeled by the Armstrong–Frederick law. The substrate layer is made of elastomer material whose mechanical behavior is assumed to be hyperelastic and
modeled by a neo-Hookean constitutive law. The Marciniak–Kuczynski imperfection analysis is used to predict plastic flow localization. Through various numerical simulations, the influence of kinematic hardening on localized necking as well as the impact of the addition of an elastomer layer are specifically emphasized.
Comparisons with experimental results are also carried out to assess the relevance of incorporating kinematic hardening in the constitutive modeling of freestanding metal sheets.
2017-01-01T00:00:00ZBEN BETTAIEB, MohamedABED-MERAIM, FaridPrediction of necking limits in thin substrate-supported metal layers, which are typically used as functional components in electronic devices, represents nowadays an ambitious challenge. The specific purpose of the current work is, first, to numerically investigate the effect of kinematic hardening on localized necking in a
freestanding metal layer. Second, the impact of adding a substrate layer on the ductility evolution of the resulting elastomer/metal bilayer will be analyzed. The materials in the metal and substrate layers are assumed to be isotropic, incompressible and strain-rate independent. The behavior of the metal layer is described by a rigid–plastic model with mixed (isotropic and kinematic) hardening. The isotropic hardening contribution is
modeled by the Hollomon law, while kinematic hardening is modeled by the Armstrong–Frederick law. The substrate layer is made of elastomer material whose mechanical behavior is assumed to be hyperelastic and
modeled by a neo-Hookean constitutive law. The Marciniak–Kuczynski imperfection analysis is used to predict plastic flow localization. Through various numerical simulations, the influence of kinematic hardening on localized necking as well as the impact of the addition of an elastomer layer are specifically emphasized.
Comparisons with experimental results are also carried out to assess the relevance of incorporating kinematic hardening in the constitutive modeling of freestanding metal sheets.Multi-scale experimental investigation of the viscous nature of damage in Advanced Sheet Molding Compound (A-SMC) submitted to high strain ratesSHIRINBAYAN, MohammadaliFITOUSSI, JosephBOCQUET, MichelMERAGHNI, FodilSUROWIEC, BenjaminTCHARKHTCHI, Abbashttp://hdl.handle.net/10985/118542017-06-16T23:55:46Z2017-01-01T00:00:00ZMulti-scale experimental investigation of the viscous nature of damage in Advanced Sheet Molding Compound (A-SMC) submitted to high strain rates
SHIRINBAYAN, Mohammadali; FITOUSSI, Joseph; BOCQUET, Michel; MERAGHNI, Fodil; SUROWIEC, Benjamin; TCHARKHTCHI, Abbas
This paper aims to present an experimental multi-scale analysis of quasi-static and high strain rate damage behavior of a new formulation of SMC composite (Advanced SMC). In order to study its capability to absorb energy through damage accumulation, Randomly Oriented (RO) and High oriented (HO) A-SMC composites damage has been investigated at both microscopic and macroscopic scales. A specific device has been developed in order to perform Interrupted Dynamic Tensile Tests (IDTT) which allows analyzing the evolution of the microscopic damage mechanisms occurring during rapid tensile tests. Several damage micro-mechanisms have been pointed out. The relative influences of these micro-damage events and their interactions have been related to the macroscopic damage behavior through the definition of microscopic and macroscopic damage indicators. Damage threshold and kinetic have been quantified at various strain rate for different microstructures and loading cases (RO, HO-0 and HO-90). It has been shown at both scales that increasing strain rate leads to an onset of damage initiation together with a reduction of the damage accumulation kinetic. Moreover, the influence of the fiber orientation has been studied in order to emphasize the anisotropic strain rate effect at the fiber-matrix interface scale. The latter was related to the influence of the microstructure of A-SMC composites. Finally, on the basis of the whole experimental results, the microscopic origin of the viscous nature of the damage behavior of A-SMCs composites have been discussed and related to the influence of the strain rate and microstructure.
2017-01-01T00:00:00ZSHIRINBAYAN, MohammadaliFITOUSSI, JosephBOCQUET, MichelMERAGHNI, FodilSUROWIEC, BenjaminTCHARKHTCHI, AbbasThis paper aims to present an experimental multi-scale analysis of quasi-static and high strain rate damage behavior of a new formulation of SMC composite (Advanced SMC). In order to study its capability to absorb energy through damage accumulation, Randomly Oriented (RO) and High oriented (HO) A-SMC composites damage has been investigated at both microscopic and macroscopic scales. A specific device has been developed in order to perform Interrupted Dynamic Tensile Tests (IDTT) which allows analyzing the evolution of the microscopic damage mechanisms occurring during rapid tensile tests. Several damage micro-mechanisms have been pointed out. The relative influences of these micro-damage events and their interactions have been related to the macroscopic damage behavior through the definition of microscopic and macroscopic damage indicators. Damage threshold and kinetic have been quantified at various strain rate for different microstructures and loading cases (RO, HO-0 and HO-90). It has been shown at both scales that increasing strain rate leads to an onset of damage initiation together with a reduction of the damage accumulation kinetic. Moreover, the influence of the fiber orientation has been studied in order to emphasize the anisotropic strain rate effect at the fiber-matrix interface scale. The latter was related to the influence of the microstructure of A-SMC composites. Finally, on the basis of the whole experimental results, the microscopic origin of the viscous nature of the damage behavior of A-SMCs composites have been discussed and related to the influence of the strain rate and microstructure.A new method to fabricate Fe-TiC composite using conventional sintering and steam hammerLAHOUEL, AliBOUDEBANE, SaïdIOST, AlainMONTAGNE, Alexhttp://hdl.handle.net/10985/118362017-06-13T23:53:53Z2017-01-01T00:00:00ZA new method to fabricate Fe-TiC composite using conventional sintering and steam hammer
LAHOUEL, Ali; BOUDEBANE, Saïd; IOST, Alain; MONTAGNE, Alex
The aim of this research paper is to fabricate a Fe-TiC composite by a novel and simple manufacturing method. The latter is based on two cumulative processes; a conventional sintering (transient liquid phase sintering) and a hot forging with steam hammer respectively. The blinder phase of the studied simples is varied from carbon steel to high alloy steel using alloying additive powders. The obtained outcomes showed that after the sintering process, the relative density of the performed simples is improved from 86% to 95.8% without any densification process. Otherwise, in order to ensure maximum densification and enhance in addition the solubility of the alloying additives the hot forging process is then applied. Indeed, the final obtained composite product is a TiC-strengthened steel with a relative density around 99% (about 6.5 g/cm3 of density) wherein 30% (wt.) of spherical and semi-spherical TiC particles are homogeneously distributed in the metal matrix.
2017-01-01T00:00:00ZLAHOUEL, AliBOUDEBANE, SaïdIOST, AlainMONTAGNE, AlexThe aim of this research paper is to fabricate a Fe-TiC composite by a novel and simple manufacturing method. The latter is based on two cumulative processes; a conventional sintering (transient liquid phase sintering) and a hot forging with steam hammer respectively. The blinder phase of the studied simples is varied from carbon steel to high alloy steel using alloying additive powders. The obtained outcomes showed that after the sintering process, the relative density of the performed simples is improved from 86% to 95.8% without any densification process. Otherwise, in order to ensure maximum densification and enhance in addition the solubility of the alloying additives the hot forging process is then applied. Indeed, the final obtained composite product is a TiC-strengthened steel with a relative density around 99% (about 6.5 g/cm3 of density) wherein 30% (wt.) of spherical and semi-spherical TiC particles are homogeneously distributed in the metal matrix.Influence of the Manufacturing Process of a Claw-Pole Alternator on its Stator Shape and Acoustic NoiseTAN-KIN, AntoineHAGEN, NicolasLANFRANCHI, VincentCLENET, StephaneCOOREVITS, ThierryMIPO, Jean ClaudeLEGRANGER, JeromePALLESCHI, frederichttp://hdl.handle.net/10985/118352017-06-13T23:53:52Z2017-05-25T00:00:00ZInfluence of the Manufacturing Process of a Claw-Pole Alternator on its Stator Shape and Acoustic Noise
TAN-KIN, Antoine; HAGEN, Nicolas; LANFRANCHI, Vincent; CLENET, Stephane; COOREVITS, Thierry; MIPO, Jean Claude; LEGRANGER, Jerome; PALLESCHI, frederic
This paper shows the influence of the manufacturing process of a claw-pole alternator on its acoustic noise. First, the stator welds and the assembly of the stator in the
brackets are linked to deformations of the inner diameter of the stator. Then, the influences of these deformations on the magnetic forces and the subsequent acoustic noise are investigated. Results show that the deformations caused by the
manufacturing process significantly increase the sound power level of particular orders.
2017-05-25T00:00:00ZTAN-KIN, AntoineHAGEN, NicolasLANFRANCHI, VincentCLENET, StephaneCOOREVITS, ThierryMIPO, Jean ClaudeLEGRANGER, JeromePALLESCHI, fredericThis paper shows the influence of the manufacturing process of a claw-pole alternator on its acoustic noise. First, the stator welds and the assembly of the stator in the
brackets are linked to deformations of the inner diameter of the stator. Then, the influences of these deformations on the magnetic forces and the subsequent acoustic noise are investigated. Results show that the deformations caused by the
manufacturing process significantly increase the sound power level of particular orders.Model Order Reduction of Electrical Machines with Multiple InputsFARZAM FAR, MernhazBELAHCEN, AnouarRASILO, PavoCLENET, StéphanePIERQUIN, Antoinehttp://hdl.handle.net/10985/118342017-06-13T23:53:44Z2017-03-01T00:00:00ZModel Order Reduction of Electrical Machines with Multiple Inputs
FARZAM FAR, Mernhaz; BELAHCEN, Anouar; RASILO, Pavo; CLENET, Stéphane; PIERQUIN, Antoine
In this paper, proper orthogonal decomposition method is employed to build a reduced-order model from a high-order nonlinear permanent magnet synchronous machine
model with multiple inputs. Three parameters are selected as the multiple inputs of the machine. These parameters are terminal current, angle of the terminal current, and rotation angle. To produce the lower-rank system, snapshots or instantaneous system states are projected onto a set of orthonormal basis functions with small dimension. The reduced model is then validated by comparing the vector potential, flux
density distribution, and torque results of the original model, which indicates the capability of using the proper orthogonal decomposition method in the multi-variable input problems. The developed methodology can be used for fast simulations of
the machine.
2017-03-01T00:00:00ZFARZAM FAR, MernhazBELAHCEN, AnouarRASILO, PavoCLENET, StéphanePIERQUIN, AntoineIn this paper, proper orthogonal decomposition method is employed to build a reduced-order model from a high-order nonlinear permanent magnet synchronous machine
model with multiple inputs. Three parameters are selected as the multiple inputs of the machine. These parameters are terminal current, angle of the terminal current, and rotation angle. To produce the lower-rank system, snapshots or instantaneous system states are projected onto a set of orthonormal basis functions with small dimension. The reduced model is then validated by comparing the vector potential, flux
density distribution, and torque results of the original model, which indicates the capability of using the proper orthogonal decomposition method in the multi-variable input problems. The developed methodology can be used for fast simulations of
the machine.Determination of residual stresses within submicroscopic and coherent precipitatesJÉGOU, SébastienBARRALLIER, Laurenthttp://hdl.handle.net/10985/118152017-06-09T23:53:25Z2012-01-01T00:00:00ZDetermination of residual stresses within submicroscopic and coherent precipitates
JÉGOU, Sébastien; BARRALLIER, Laurent
Technical report about experiment made in Desy Synchrotron
2012-01-01T00:00:00ZJÉGOU, SébastienBARRALLIER, LaurentTechnical report about experiment made in Desy SynchrotronNitruration des aciers de construction : génération des contraintes résiduellesBARRALLIER, LaurentJÉGOU, Sébastienhttp://hdl.handle.net/10985/118142017-06-09T23:53:30Z2017-01-01T00:00:00ZNitruration des aciers de construction : génération des contraintes résiduelles
BARRALLIER, Laurent; JÉGOU, Sébastien
Le traitement thermochimique de nitruration est un traitement de surfaces permettant d'améliorer la durée de vie en fatigue des pièces traitées. Les dernières avancées dans ce domaine permettent de relier les paramètres technologiques du procédé (temps, température, potentiel azote, composition de l’acier) aux caractéristiques mécaniques des couches nitrurées et tout particulièrement les contraintes résiduelles. La génération des contraintes est directement liée aux différents processus physicochimiques mis en jeux dans la nitruration : co-diffusion de l’azote et du carbone, transformations métallurgiques associées, variations volumiques induites, comportement mécanique local d’un matériau hétérogène, … mais également aux gradients associés et à la géométrie de la pièce mécanique.
2017-01-01T00:00:00ZBARRALLIER, LaurentJÉGOU, SébastienLe traitement thermochimique de nitruration est un traitement de surfaces permettant d'améliorer la durée de vie en fatigue des pièces traitées. Les dernières avancées dans ce domaine permettent de relier les paramètres technologiques du procédé (temps, température, potentiel azote, composition de l’acier) aux caractéristiques mécaniques des couches nitrurées et tout particulièrement les contraintes résiduelles. La génération des contraintes est directement liée aux différents processus physicochimiques mis en jeux dans la nitruration : co-diffusion de l’azote et du carbone, transformations métallurgiques associées, variations volumiques induites, comportement mécanique local d’un matériau hétérogène, … mais également aux gradients associés et à la géométrie de la pièce mécanique.