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The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sun, 12 Feb 2023 16:05:51 GMT2023-02-12T16:05:51ZEvolution of residual stress in the diffusion zone of a model Fe-Cr-C alloy during nitriding
http://hdl.handle.net/10985/10954
Evolution of residual stress in the diffusion zone of a model Fe-Cr-C alloy during nitriding
JEGOU, Sébastien; BARRALLIER, Laurent; KUBLER, Régis; SOMERS, Marcel
Development and evolution of compressive residual stress during nitriding treatment are studied. A model carbon iron-based alloy Fe-3wt.%Cr-0.35wt.%C was nitrided in gas at 550 °C for different times. Microstructural investigation indicated an influence of the transformation and the associated carbon diffusion on the in-situ relaxation of residual stress induced by nitride precipitation. The transformation of initially present carbides into nitrides and the associated carbon accumulation ahead of the nitriding front is particularly taken into account. The distribution of residual stress in the nitrided case was predicted with a self-consistent mechanical model, using the volume changes associated with the phase transformations. To this end the nitrogen and carbon concentration distributions were converted into the equilibrium phase fractions of carbides and nitrides. An excellent correlation was obtained between experimental (X-ray diffraction analysis) and, thus, calculated independent residual stress distributions in the ferrite matrix.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/10985/109542011-01-01T00:00:00ZJEGOU, SébastienBARRALLIER, LaurentKUBLER, RégisSOMERS, MarcelDevelopment and evolution of compressive residual stress during nitriding treatment are studied. A model carbon iron-based alloy Fe-3wt.%Cr-0.35wt.%C was nitrided in gas at 550 °C for different times. Microstructural investigation indicated an influence of the transformation and the associated carbon diffusion on the in-situ relaxation of residual stress induced by nitride precipitation. The transformation of initially present carbides into nitrides and the associated carbon accumulation ahead of the nitriding front is particularly taken into account. The distribution of residual stress in the nitrided case was predicted with a self-consistent mechanical model, using the volume changes associated with the phase transformations. To this end the nitrogen and carbon concentration distributions were converted into the equilibrium phase fractions of carbides and nitrides. An excellent correlation was obtained between experimental (X-ray diffraction analysis) and, thus, calculated independent residual stress distributions in the ferrite matrix.Micromechanical behavior of UO2: crystalline anisotropy and associated internal stressezs in polycrystals
http://hdl.handle.net/10985/7638
Micromechanical behavior of UO2: crystalline anisotropy and associated internal stressezs in polycrystals
SOULACROIX, Julian; MICHEL, Bruno; GATT, Jean-Marie; KUBLER, Régis; BARRALLIER, Laurent
Uranium dioxide is the standard nuclear fuel for pressurized water reactors in France. This ceramic is manufactured by sintering. The standard shape for use in nuclear reactor is a small cylinder, also called “pellet”, which measures about 8mm in diameter and 12mm in height. These pellets are then stacked into a zirconium alloy cladding, forming a rod. The fuel rods are then assembled together and these assemblies are put in the nuclear core. The mechanical behavior of the nuclear fuel during operation depends on the mechanical state of the rod (pellet and cladding), which can be related to other phenomena taking place during irradiation. A first step in the modeling approach is to study the mechanical behavior of non irradiated uranium oxide. For a temperature higher than about 1000°C and for a strain rate higher than about 1.10/6s/1, this material can be plastically deformed by a dislocation glide mechanism. For lower strain rate, the deformation mechanism is a diffusional process (see[6] for a complete map of the different deformations mechanisms in UO2). In this paper, we study the effect of the plastic anisotropy on the kinematic hardening of UO2. Our work is based on a microscopic approach and our results suggest that the kinematic hardening effect can be explained by the intergranular interaction between neighbor grains. An evaluation of this behavior was made using a crystal plasticity constitutive model and a polycrystalline aggregate.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/76382013-01-01T00:00:00ZSOULACROIX, JulianMICHEL, BrunoGATT, Jean-MarieKUBLER, RégisBARRALLIER, LaurentUranium dioxide is the standard nuclear fuel for pressurized water reactors in France. This ceramic is manufactured by sintering. The standard shape for use in nuclear reactor is a small cylinder, also called “pellet”, which measures about 8mm in diameter and 12mm in height. These pellets are then stacked into a zirconium alloy cladding, forming a rod. The fuel rods are then assembled together and these assemblies are put in the nuclear core. The mechanical behavior of the nuclear fuel during operation depends on the mechanical state of the rod (pellet and cladding), which can be related to other phenomena taking place during irradiation. A first step in the modeling approach is to study the mechanical behavior of non irradiated uranium oxide. For a temperature higher than about 1000°C and for a strain rate higher than about 1.10/6s/1, this material can be plastically deformed by a dislocation glide mechanism. For lower strain rate, the deformation mechanism is a diffusional process (see[6] for a complete map of the different deformations mechanisms in UO2). In this paper, we study the effect of the plastic anisotropy on the kinematic hardening of UO2. Our work is based on a microscopic approach and our results suggest that the kinematic hardening effect can be explained by the intergranular interaction between neighbor grains. An evaluation of this behavior was made using a crystal plasticity constitutive model and a polycrystalline aggregate.Residual stress field prediction and fatigue post processing for shot peened mechanical parts with complex geometry
http://hdl.handle.net/10985/14737
Residual stress field prediction and fatigue post processing for shot peened mechanical parts with complex geometry
GELINEAU, Maxime; BARRALLIER, Laurent; ROUHAUD, Emmanuelle; KUBLER, Régis; PUYDT, Quentin; BADREDDINE, Jawad; MAUDUIT, Clément; WEBER, Bastien
Even when properly controlled, shot peening treatment may induce a complex residual stresses (RS) field depending on the geometry of the treated part. Hence, among the variables which affect the fatigue behaviour of shot peened components, the geometry could play a major role. The more widespread method for predicting RS after shot peening consists in modelling the process by simulating the impacts between the shot and the treated part. When the geometry become complex, this method is not consistent with industrial constraints in terms of computing time. Thus the need is to develop a methodology in order to generate the RS field into a shot peened mechanical part with complex non flat geometries, and consequently predict the lifetime in a high cycle fatigue (HCF) regime.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/147372017-01-01T00:00:00ZGELINEAU, MaximeBARRALLIER, LaurentROUHAUD, EmmanuelleKUBLER, RégisPUYDT, QuentinBADREDDINE, JawadMAUDUIT, ClémentWEBER, BastienEven when properly controlled, shot peening treatment may induce a complex residual stresses (RS) field depending on the geometry of the treated part. Hence, among the variables which affect the fatigue behaviour of shot peened components, the geometry could play a major role. The more widespread method for predicting RS after shot peening consists in modelling the process by simulating the impacts between the shot and the treated part. When the geometry become complex, this method is not consistent with industrial constraints in terms of computing time. Thus the need is to develop a methodology in order to generate the RS field into a shot peened mechanical part with complex non flat geometries, and consequently predict the lifetime in a high cycle fatigue (HCF) regime.Calculs Éléments Finis à l’échelle des grains depuis des données EBSD
http://hdl.handle.net/10985/18497
Calculs Éléments Finis à l’échelle des grains depuis des données EBSD
DEPRIESTER, Dorian; KUBLER, Régis
For the sake of understanding the behaviour of a polycrystal at its grain scale, Finite Element (FE) numerical simulations can be performed, taking into account the physical properties of each grain. Those simulations must take into account the phase heterogeneities, the local anisotropies and the crystalline orientations as well. In addition, the actual grain morphologies must be well described in order to model localization phenomena. An algorithm, named MTEX2Gmsh, is proposed to automatically generate an EF mesh from EBSD data. The resulting mesh gives smooth and accurate descriptions of the grain boundaries together with reduced Degrees of Freedom (DoF), hence limited computational times. Using this algorithm, the fragile-elastic behaviour of a ceramic and micro-plasticity phenomena in a nitrided steel are studied as application cases. The latter is based on a crystal-plasticity model for the ferrite phase.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/10985/184972019-01-01T00:00:00ZDEPRIESTER, DorianKUBLER, RégisFor the sake of understanding the behaviour of a polycrystal at its grain scale, Finite Element (FE) numerical simulations can be performed, taking into account the physical properties of each grain. Those simulations must take into account the phase heterogeneities, the local anisotropies and the crystalline orientations as well. In addition, the actual grain morphologies must be well described in order to model localization phenomena. An algorithm, named MTEX2Gmsh, is proposed to automatically generate an EF mesh from EBSD data. The resulting mesh gives smooth and accurate descriptions of the grain boundaries together with reduced Degrees of Freedom (DoF), hence limited computational times. Using this algorithm, the fragile-elastic behaviour of a ceramic and micro-plasticity phenomena in a nitrided steel are studied as application cases. The latter is based on a crystal-plasticity model for the ferrite phase.Perforation of aluminium alloy thin plates
http://hdl.handle.net/10985/17023
Perforation of aluminium alloy thin plates
ANTOINAT, Léonard; KUBLER, Régis; BAROU, Jean-Luc; VIOT, Philippe; BARRALLIER, Laurent
Low velocity perforation of aeronautical aluminium alloy sheets 2024 T3 is studied in this paper. After a literature review on recent experiments and models of plate's perforation, experimental results for 2 thicknesses (2 mm and 4 mm) of plates are presented. Perforation tests are performed with an instrumented drop test. The striker has a large diameter and a conical shape nose. Two models for perforation are presented and calibrated to bring a better understanding of the experiments. The first one is an analytical model based on an energetic approach. The second one is a numerical shell Finite Element FE model. A Johnson Cook phenomenological behaviour law of the plate's material is implemented in the finite element code Abaqus/Explicit. The velocity, the evolution of the impact force, the absorbed energy and the cracks' propagation are analysed.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/170232015-01-01T00:00:00ZANTOINAT, LéonardKUBLER, RégisBAROU, Jean-LucVIOT, PhilippeBARRALLIER, LaurentLow velocity perforation of aeronautical aluminium alloy sheets 2024 T3 is studied in this paper. After a literature review on recent experiments and models of plate's perforation, experimental results for 2 thicknesses (2 mm and 4 mm) of plates are presented. Perforation tests are performed with an instrumented drop test. The striker has a large diameter and a conical shape nose. Two models for perforation are presented and calibrated to bring a better understanding of the experiments. The first one is an analytical model based on an energetic approach. The second one is a numerical shell Finite Element FE model. A Johnson Cook phenomenological behaviour law of the plate's material is implemented in the finite element code Abaqus/Explicit. The velocity, the evolution of the impact force, the absorbed energy and the cracks' propagation are analysed.Semi phenomenological modelling of the behavior of TRIP steels
http://hdl.handle.net/10985/8336
Semi phenomenological modelling of the behavior of TRIP steels
KUBLER, Régis; BERVEILLER, Marcel; BUESSLER, Pascal
A new semi-phenomenological model is developed based on a mean-field description of the TRIP behavior for the simulation of multiaxial loads. This model intends to reduce the number of internal variables of crystalline models that cannot be used for the moment in metal forming simulations. Starting from local and crystallographic approaches, the mean-field approach is obtained at the phase level with the concept of Mean Instantaneous Transformation Strain (MITS) accompanying martensitic transformation. Within the framework of the thermodynamics of irreversible processes, driving forces, martensitic volume fraction evolution and an expression of the TRIP effect are determined for this new model. A classical self-consistent scheme is used to model the behavior of multiphased TRIP steels. The model is tested for cooling at constant loads and for multiaxial loadings at constant temperatures. The predictions reproduce the increase in ductility, the dynamic softening effect and the multiaxial behavior of a multiphased TRIP steel
The authors are grateful to ArcelorMittal R&D for supporting this research.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/10985/83362011-01-01T00:00:00ZKUBLER, RégisBERVEILLER, MarcelBUESSLER, PascalA new semi-phenomenological model is developed based on a mean-field description of the TRIP behavior for the simulation of multiaxial loads. This model intends to reduce the number of internal variables of crystalline models that cannot be used for the moment in metal forming simulations. Starting from local and crystallographic approaches, the mean-field approach is obtained at the phase level with the concept of Mean Instantaneous Transformation Strain (MITS) accompanying martensitic transformation. Within the framework of the thermodynamics of irreversible processes, driving forces, martensitic volume fraction evolution and an expression of the TRIP effect are determined for this new model. A classical self-consistent scheme is used to model the behavior of multiphased TRIP steels. The model is tested for cooling at constant loads and for multiaxial loadings at constant temperatures. The predictions reproduce the increase in ductility, the dynamic softening effect and the multiaxial behavior of a multiphased TRIP steelShot peening analysis on trip780 steel exhibiting martensitic transformation
http://hdl.handle.net/10985/13475
Shot peening analysis on trip780 steel exhibiting martensitic transformation
GUIHEUX, Romain; BERVEILLER, Sophie; KUBLER, Régis; BOUSCAUD, Denis; PATOOR, Etienne; PUYDT, Quentin; OSMOND, Pierre; WEBER, Bastien
The microstructure and mechanical fields were studied on a cold-rolled TRIP 780 steel after conventional shot peening, and with or without pre-strain; for the first time, results were compared to numerical simulations at the phase scale. 1. The pre-strain does not affect residual stresses in the different phases nor the affected depth but it shifts the austenite fraction value towards lower values. 2. All the constituents were found in compression; the maximum value reached in the austenite was -800 MPa while around -500 MPa in the BCC phases. 3. The stress variations are maximum in the zone affected by the martensitic transformation.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/134752017-01-01T00:00:00ZGUIHEUX, RomainBERVEILLER, SophieKUBLER, RégisBOUSCAUD, DenisPATOOR, EtiennePUYDT, QuentinOSMOND, PierreWEBER, BastienThe microstructure and mechanical fields were studied on a cold-rolled TRIP 780 steel after conventional shot peening, and with or without pre-strain; for the first time, results were compared to numerical simulations at the phase scale. 1. The pre-strain does not affect residual stresses in the different phases nor the affected depth but it shifts the austenite fraction value towards lower values. 2. All the constituents were found in compression; the maximum value reached in the austenite was -800 MPa while around -500 MPa in the BCC phases. 3. The stress variations are maximum in the zone affected by the martensitic transformation.Damping Capacity of Ti–Nb Shape Memory Alloys Evaluated Through DMA and Single-Impact Tests
http://hdl.handle.net/10985/22881
Damping Capacity of Ti–Nb Shape Memory Alloys Evaluated Through DMA and Single-Impact Tests
ELMAY, Wafa; PELTIER, Laurent; GABRION, X.; KUBLER, Régis; PIOTROWSKI, Boris; LAHEURTE, Pascal; BERVEILLER, Sophie
The present work deals with the study of the damping capacity of b-metastable Ti–(24–26) Nb alloys. In this work, several methods have been used to characterize this damping. The impact tests were carried out using two test benches: high-speed impacts were carried out using a vertical ﬁring pressure gun and low-velocity impacts were studied with a bullet drop test. In addition, an original approach of a dynamic mechanical analysis (DMA) is proposed in order to obtain more in-depth understanding of the relationship between microstructure, deformation mechanisms, and damping capacity. The specimens are studied at different microstructure states: single β, dual-phase β + α″, and martensitic phase. A correlation is established between the evolution of the damping factor as function of the applied strain and the occurrence of the corresponding deformation mechanisms. The stress-in-duced martensite mechanism contributes to the improvement of the damping factor.The highest damping capacity is observed for the dual-phase specimen (β + α″). It is shown that the contribution of both the reorientation martensite variants and stress-induced martensitic transformation lead to a damping capacity higher than a single deformation mechanism one.
Tue, 01 Nov 2022 00:00:00 GMThttp://hdl.handle.net/10985/228812022-11-01T00:00:00ZELMAY, WafaPELTIER, LaurentGABRION, X.KUBLER, RégisPIOTROWSKI, BorisLAHEURTE, PascalBERVEILLER, SophieThe present work deals with the study of the damping capacity of b-metastable Ti–(24–26) Nb alloys. In this work, several methods have been used to characterize this damping. The impact tests were carried out using two test benches: high-speed impacts were carried out using a vertical ﬁring pressure gun and low-velocity impacts were studied with a bullet drop test. In addition, an original approach of a dynamic mechanical analysis (DMA) is proposed in order to obtain more in-depth understanding of the relationship between microstructure, deformation mechanisms, and damping capacity. The specimens are studied at different microstructure states: single β, dual-phase β + α″, and martensitic phase. A correlation is established between the evolution of the damping factor as function of the applied strain and the occurrence of the corresponding deformation mechanisms. The stress-in-duced martensite mechanism contributes to the improvement of the damping factor.The highest damping capacity is observed for the dual-phase specimen (β + α″). It is shown that the contribution of both the reorientation martensite variants and stress-induced martensitic transformation lead to a damping capacity higher than a single deformation mechanism one.MODELISATION DES CONTRAINTES RESIDUELLES
http://hdl.handle.net/10985/18004
MODELISATION DES CONTRAINTES RESIDUELLES
KUBLER, Régis
Dans cette partie de cours, nous présentons la modélisation des contraintes résiduelles à partir d’une déformation libre de contraintes (« Eigenstrain »). Pour rendre la déformation totale compatible, cette « eigenstrain » est accommodée par une déformation élastique. A partir des équations de la mécanique des milieux continus (comportement, équilibre, compatibilités, conditions aux limites de la structure), nous regardons comment générer un profil de contraintes résiduelles dans une structure. Différentes approches de simulation des contraintes résiduelles sont présentées. Ces simulations peuvent être un point de départ d’autres simulations devant tenir compte des contraintes résiduelles initiales. Nous présentons aussi des travaux et méthodes pour descendre les échelles jusqu’à l’échelle de la microstructure.
Wed, 01 Jan 2020 00:00:00 GMThttp://hdl.handle.net/10985/180042020-01-01T00:00:00ZKUBLER, RégisDans cette partie de cours, nous présentons la modélisation des contraintes résiduelles à partir d’une déformation libre de contraintes (« Eigenstrain »). Pour rendre la déformation totale compatible, cette « eigenstrain » est accommodée par une déformation élastique. A partir des équations de la mécanique des milieux continus (comportement, équilibre, compatibilités, conditions aux limites de la structure), nous regardons comment générer un profil de contraintes résiduelles dans une structure. Différentes approches de simulation des contraintes résiduelles sont présentées. Ces simulations peuvent être un point de départ d’autres simulations devant tenir compte des contraintes résiduelles initiales. Nous présentons aussi des travaux et méthodes pour descendre les échelles jusqu’à l’échelle de la microstructure.Resolution of the Wicksell's equation by Minimum Distance Estimation
http://hdl.handle.net/10985/17597
Resolution of the Wicksell's equation by Minimum Distance Estimation
DEPRIESTER, Dorian; KUBLER, Régis
The estimation of the grain size in granular materials is usually performed by 2Dobservations. Unfolding the grain size distribution from apparent 2D sizes is commonly referred as the corpuscle problem. For spherical particles, the distribution of the apparent size can be related to that of the actual size thanks to the Wicksell’s equation. The Saltikov method, which is based on Wicksell’s equation, is the most widely used method for resolving corpuscle problems. This method is recursive and works on the finite histogram of the grain size. In this paper, we propose an algorithm based on a minimizing procedure to numerically solve the Wicksell’s equation, assuming a parametric model for the distribution (e.g. lognormal distribution). This algorithm is applied on real material and the results are compared to those found using Saltikov or Saltikov-basedstereology techniques. A criterion is proposed for choosing the number of bins in the Saltikov method. The accuracy of the proposed algorithm, depending on the sample size, is studied.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/10985/175972019-01-01T00:00:00ZDEPRIESTER, DorianKUBLER, RégisThe estimation of the grain size in granular materials is usually performed by 2Dobservations. Unfolding the grain size distribution from apparent 2D sizes is commonly referred as the corpuscle problem. For spherical particles, the distribution of the apparent size can be related to that of the actual size thanks to the Wicksell’s equation. The Saltikov method, which is based on Wicksell’s equation, is the most widely used method for resolving corpuscle problems. This method is recursive and works on the finite histogram of the grain size. In this paper, we propose an algorithm based on a minimizing procedure to numerically solve the Wicksell’s equation, assuming a parametric model for the distribution (e.g. lognormal distribution). This algorithm is applied on real material and the results are compared to those found using Saltikov or Saltikov-basedstereology techniques. A criterion is proposed for choosing the number of bins in the Saltikov method. The accuracy of the proposed algorithm, depending on the sample size, is studied.