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Suzanne Degallaix - One of the best experts on this subject based on the ideXlab platform.
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polycrystalline modeling of the cyclic hardening softening behavior of an austenitic ferritic stainless steel
Mechanics of Materials, 2010Co-Authors: Pierre Evrard, Véronique Aubin, I Alvarezarmas, Suzanne DegallaixAbstract:As other metallic materials, in low-cycle fatigue, duplex stainless steels (DSS) exhibit a cyclic hardening, followed by a cyclic softening, before stabilization of the stress. In order to simulate the cyclic hardening/softening curves in low-cycle fatigue of an austenitic–ferritic or duplex stainless steel (DSS), a new polycrystalline model is proposed. The polycrystalline model developed by Cailletaud (1992) and Pilvin (1990) and modified by Hoc and Forest (2001) was previously extended in Evrard et al. (2008) in order to take into account the bi-phased character of the DSS. This model correctly accounts for the cyclic hardening, but it is not able to simulate the cyclic softening, consequently, stresses at the stabilized state are overestimated. TEM observations of the dislocation structures built during a cyclic uniaxial tension/compression Test show that, during the cyclic hardening, planar arrangements are observed in austenitic grains and no significant evolution is observed during the subsequent cyclic softening and stabilization stage. On the contrary, in ferritic grains, dislocations are homogeneously distributed during cyclic hardening, and the microstructure evolves during the subsequent cyclic softening and stabilization stage. Dislocation structures build progressively, consisting of hard zones or walls, separated by soft zones or channels. We propose to model the cyclic softening through dislocation structure evolution within ferritic grains. The single crystal law used by Hoc and Forest (2001) is modified in order to take into account the heterogeneous distribution of dislocations in the ferrite. Numerical simulations are compared with experimental data. A good agreement is observed between experimental and calculated hardening/softening curves and stabilized hysteresis loops.
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Polycrystalline modeling of the cyclic hardening/softening behavior of an austenitic–ferritic stainless steel
Mechanics of Materials, 2010Co-Authors: Pierre Evrard, Iris Alvarez-armas, Véronique Aubin, Suzanne DegallaixAbstract:As other metallic materials, in low-cycle fatigue, duplex stainless steels (DSS) exhibit a cyclic hardening, followed by a cyclic softening, before stabilization of the stress. In order to simulate the cyclic hardening/softening curves in low-cycle fatigue of an austenitic–ferritic or duplex stainless steel (DSS), a new polycrystalline model is proposed. The polycrystalline model developed by (Cailletaud, 1992) and (Pilvin, 1990) and modified by Hoc and Forest (2001) was previously extended in Evrard et al. (2008) in order to take into account the bi-phased character of the DSS. This model correctly accounts for the cyclic hardening, but it is not able to simulate the cyclic softening, consequently, stresses at the stabilized state are overestimated. TEM observations of the dislocation structures built during a cyclic uniaxial tension/compression Test show that, during the cyclic hardening, planar arrangements are observed in austenitic grains and no significant evolution is observed during the subsequent cyclic softening and stabilization stage. On the contrary, in ferritic grains, dislocations are homogeneously distributed during cyclic hardening, and the microstructure evolves during the subsequent cyclic softening and stabilization stage. Dislocation structures build progressively, consisting of hard zones or walls, separated by soft zones or channels. We propose to model the cyclic softening through dislocation structure evolution within ferritic grains. The single crystal law used by Hoc and Forest (2001) is modified in order to take into account the heterogeneous distribution of dislocations in the ferrite. Numerical simulations are compared with experimental data. A good agreement is observed between experimental and calculated hardening/softening curves and stabilized hysteresis loops.
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Yield Surface and Complex Loading Path Simulation of a Duplex Stainless Steel Using a Bi-Phase Polycrystalline Model
Materials Science Forum, 2008Co-Authors: Pierre Evrard, Véronique Aubin, Suzanne Degallaix, Djimedo KondoAbstract:In order to model the elasto-viscoplastic behaviour of an austenitic-ferritic stainless steel, the model initially developed by Cailletaud-Pilvin [1] [2] and used for modeling single-phase polycrystalline steel is extended in order to take into account the bi-phased character of a duplex steel. Two concentration laws and two local constitutive laws, based on the crystallographic slips and the dislocation densities, are thus simultaneously considered. The model parameters are identified by an inverse method. Simple Tests among which tension Test at constant strain rate and at different strain rates and uniaxial Tension-Compression Test are used during the identification step. The predictive capabilities of the polycrystalline model are Tested for non-proportional loading paths. It is shown that the model reproduces the over-hardening experimentally observed for this kind of loading paths. Then, yield surfaces are simulated during a uniaxial Tension-Compression Test: it is shown that the distortion (i.e. plastic anisotropy induced by loading path) is correctly described.
Pierre Evrard - One of the best experts on this subject based on the ideXlab platform.
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polycrystalline modeling of the cyclic hardening softening behavior of an austenitic ferritic stainless steel
Mechanics of Materials, 2010Co-Authors: Pierre Evrard, Véronique Aubin, I Alvarezarmas, Suzanne DegallaixAbstract:As other metallic materials, in low-cycle fatigue, duplex stainless steels (DSS) exhibit a cyclic hardening, followed by a cyclic softening, before stabilization of the stress. In order to simulate the cyclic hardening/softening curves in low-cycle fatigue of an austenitic–ferritic or duplex stainless steel (DSS), a new polycrystalline model is proposed. The polycrystalline model developed by Cailletaud (1992) and Pilvin (1990) and modified by Hoc and Forest (2001) was previously extended in Evrard et al. (2008) in order to take into account the bi-phased character of the DSS. This model correctly accounts for the cyclic hardening, but it is not able to simulate the cyclic softening, consequently, stresses at the stabilized state are overestimated. TEM observations of the dislocation structures built during a cyclic uniaxial tension/compression Test show that, during the cyclic hardening, planar arrangements are observed in austenitic grains and no significant evolution is observed during the subsequent cyclic softening and stabilization stage. On the contrary, in ferritic grains, dislocations are homogeneously distributed during cyclic hardening, and the microstructure evolves during the subsequent cyclic softening and stabilization stage. Dislocation structures build progressively, consisting of hard zones or walls, separated by soft zones or channels. We propose to model the cyclic softening through dislocation structure evolution within ferritic grains. The single crystal law used by Hoc and Forest (2001) is modified in order to take into account the heterogeneous distribution of dislocations in the ferrite. Numerical simulations are compared with experimental data. A good agreement is observed between experimental and calculated hardening/softening curves and stabilized hysteresis loops.
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Polycrystalline modeling of the cyclic hardening/softening behavior of an austenitic–ferritic stainless steel
Mechanics of Materials, 2010Co-Authors: Pierre Evrard, Iris Alvarez-armas, Véronique Aubin, Suzanne DegallaixAbstract:As other metallic materials, in low-cycle fatigue, duplex stainless steels (DSS) exhibit a cyclic hardening, followed by a cyclic softening, before stabilization of the stress. In order to simulate the cyclic hardening/softening curves in low-cycle fatigue of an austenitic–ferritic or duplex stainless steel (DSS), a new polycrystalline model is proposed. The polycrystalline model developed by (Cailletaud, 1992) and (Pilvin, 1990) and modified by Hoc and Forest (2001) was previously extended in Evrard et al. (2008) in order to take into account the bi-phased character of the DSS. This model correctly accounts for the cyclic hardening, but it is not able to simulate the cyclic softening, consequently, stresses at the stabilized state are overestimated. TEM observations of the dislocation structures built during a cyclic uniaxial tension/compression Test show that, during the cyclic hardening, planar arrangements are observed in austenitic grains and no significant evolution is observed during the subsequent cyclic softening and stabilization stage. On the contrary, in ferritic grains, dislocations are homogeneously distributed during cyclic hardening, and the microstructure evolves during the subsequent cyclic softening and stabilization stage. Dislocation structures build progressively, consisting of hard zones or walls, separated by soft zones or channels. We propose to model the cyclic softening through dislocation structure evolution within ferritic grains. The single crystal law used by Hoc and Forest (2001) is modified in order to take into account the heterogeneous distribution of dislocations in the ferrite. Numerical simulations are compared with experimental data. A good agreement is observed between experimental and calculated hardening/softening curves and stabilized hysteresis loops.
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Yield Surface and Complex Loading Path Simulation of a Duplex Stainless Steel Using a Bi-Phase Polycrystalline Model
Materials Science Forum, 2008Co-Authors: Pierre Evrard, Véronique Aubin, Suzanne Degallaix, Djimedo KondoAbstract:In order to model the elasto-viscoplastic behaviour of an austenitic-ferritic stainless steel, the model initially developed by Cailletaud-Pilvin [1] [2] and used for modeling single-phase polycrystalline steel is extended in order to take into account the bi-phased character of a duplex steel. Two concentration laws and two local constitutive laws, based on the crystallographic slips and the dislocation densities, are thus simultaneously considered. The model parameters are identified by an inverse method. Simple Tests among which tension Test at constant strain rate and at different strain rates and uniaxial Tension-Compression Test are used during the identification step. The predictive capabilities of the polycrystalline model are Tested for non-proportional loading paths. It is shown that the model reproduces the over-hardening experimentally observed for this kind of loading paths. Then, yield surfaces are simulated during a uniaxial Tension-Compression Test: it is shown that the distortion (i.e. plastic anisotropy induced by loading path) is correctly described.
Pierre Suquet - One of the best experts on this subject based on the ideXlab platform.
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a model reduction approach to the micromechanical analysis of polycrystalline materials
Computational Mechanics, 2016Co-Authors: Jeanclaude Michel, Pierre SuquetAbstract:The present study is devoted to the extension to polycrystals of a model-reduction technique introduced by the authors, called the nonuniform transformation field analysis (NTFA). This new reduced model is obtained in two steps. First the local fields of internal variables are decomposed on a reduced basis of modes as in the NTFA. Second the dissipation potential of the phases is replaced by its tangent second-order (TSO) expansion. The reduced evolution equations of the model can be entirely expressed in terms of quantities which can be pre-computed once for all. Roughly speaking, these pre-computed quantities depend only on the average and fluctuations per phase of the modes and of the associated stress fields. The accuracy of the new NTFA-TSO model is assessed by comparison with full-field simulations on two specific applications, creep of polycrystalline ice and response of polycrystalline copper to a cyclic Tension-Compression Test. The new reduced evolution equations is faster than the full-field computations by two orders of magnitude in the two examples.
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A model-reduction approach to the micromechanical analysis of polycrystalline materials
Computational Mechanics, 2016Co-Authors: Jeanclaude Michel, Pierre SuquetAbstract:The present study is devoted to the extension to polycrystals of a model-reduction technique introduced by the authors, called the Nonuniform Transformation Field Analysis (NTFA). This new reduced model is obtained in two steps. First the local fields of internal variables are decomposed on a reduced basis of modes as in the NTFA. Second the dissipation potential of the phases is replaced by its tangent second-order (TSO) expansion. Thanks to the second approximation the reduced evolution equations of the model can be entirely expressed in terms of quantities which can be pre-computed once for all. Roughly speaking, these pre-computed quantities depend only on the average and fluctuations per phase of the modes and of the associated stress fields. The accuracy of the new NTFA-TSO model is assessed by comparison with full-field simulations on two specific applications, creep of polycrystalline ice and response of polycrystalline copper to a cyclic Tension-Compression Test. The new reduced evolution equations is faster than the full-field computations by two orders of magnitude in the two examples.
Véronique Aubin - One of the best experts on this subject based on the ideXlab platform.
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polycrystalline modeling of the cyclic hardening softening behavior of an austenitic ferritic stainless steel
Mechanics of Materials, 2010Co-Authors: Pierre Evrard, Véronique Aubin, I Alvarezarmas, Suzanne DegallaixAbstract:As other metallic materials, in low-cycle fatigue, duplex stainless steels (DSS) exhibit a cyclic hardening, followed by a cyclic softening, before stabilization of the stress. In order to simulate the cyclic hardening/softening curves in low-cycle fatigue of an austenitic–ferritic or duplex stainless steel (DSS), a new polycrystalline model is proposed. The polycrystalline model developed by Cailletaud (1992) and Pilvin (1990) and modified by Hoc and Forest (2001) was previously extended in Evrard et al. (2008) in order to take into account the bi-phased character of the DSS. This model correctly accounts for the cyclic hardening, but it is not able to simulate the cyclic softening, consequently, stresses at the stabilized state are overestimated. TEM observations of the dislocation structures built during a cyclic uniaxial tension/compression Test show that, during the cyclic hardening, planar arrangements are observed in austenitic grains and no significant evolution is observed during the subsequent cyclic softening and stabilization stage. On the contrary, in ferritic grains, dislocations are homogeneously distributed during cyclic hardening, and the microstructure evolves during the subsequent cyclic softening and stabilization stage. Dislocation structures build progressively, consisting of hard zones or walls, separated by soft zones or channels. We propose to model the cyclic softening through dislocation structure evolution within ferritic grains. The single crystal law used by Hoc and Forest (2001) is modified in order to take into account the heterogeneous distribution of dislocations in the ferrite. Numerical simulations are compared with experimental data. A good agreement is observed between experimental and calculated hardening/softening curves and stabilized hysteresis loops.
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Polycrystalline modeling of the cyclic hardening/softening behavior of an austenitic–ferritic stainless steel
Mechanics of Materials, 2010Co-Authors: Pierre Evrard, Iris Alvarez-armas, Véronique Aubin, Suzanne DegallaixAbstract:As other metallic materials, in low-cycle fatigue, duplex stainless steels (DSS) exhibit a cyclic hardening, followed by a cyclic softening, before stabilization of the stress. In order to simulate the cyclic hardening/softening curves in low-cycle fatigue of an austenitic–ferritic or duplex stainless steel (DSS), a new polycrystalline model is proposed. The polycrystalline model developed by (Cailletaud, 1992) and (Pilvin, 1990) and modified by Hoc and Forest (2001) was previously extended in Evrard et al. (2008) in order to take into account the bi-phased character of the DSS. This model correctly accounts for the cyclic hardening, but it is not able to simulate the cyclic softening, consequently, stresses at the stabilized state are overestimated. TEM observations of the dislocation structures built during a cyclic uniaxial tension/compression Test show that, during the cyclic hardening, planar arrangements are observed in austenitic grains and no significant evolution is observed during the subsequent cyclic softening and stabilization stage. On the contrary, in ferritic grains, dislocations are homogeneously distributed during cyclic hardening, and the microstructure evolves during the subsequent cyclic softening and stabilization stage. Dislocation structures build progressively, consisting of hard zones or walls, separated by soft zones or channels. We propose to model the cyclic softening through dislocation structure evolution within ferritic grains. The single crystal law used by Hoc and Forest (2001) is modified in order to take into account the heterogeneous distribution of dislocations in the ferrite. Numerical simulations are compared with experimental data. A good agreement is observed between experimental and calculated hardening/softening curves and stabilized hysteresis loops.
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Yield Surface and Complex Loading Path Simulation of a Duplex Stainless Steel Using a Bi-Phase Polycrystalline Model
Materials Science Forum, 2008Co-Authors: Pierre Evrard, Véronique Aubin, Suzanne Degallaix, Djimedo KondoAbstract:In order to model the elasto-viscoplastic behaviour of an austenitic-ferritic stainless steel, the model initially developed by Cailletaud-Pilvin [1] [2] and used for modeling single-phase polycrystalline steel is extended in order to take into account the bi-phased character of a duplex steel. Two concentration laws and two local constitutive laws, based on the crystallographic slips and the dislocation densities, are thus simultaneously considered. The model parameters are identified by an inverse method. Simple Tests among which tension Test at constant strain rate and at different strain rates and uniaxial Tension-Compression Test are used during the identification step. The predictive capabilities of the polycrystalline model are Tested for non-proportional loading paths. It is shown that the model reproduces the over-hardening experimentally observed for this kind of loading paths. Then, yield surfaces are simulated during a uniaxial Tension-Compression Test: it is shown that the distortion (i.e. plastic anisotropy induced by loading path) is correctly described.
Cedric Sauzeat - One of the best experts on this subject based on the ideXlab platform.
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Characterization of Asphalt Mixes Behaviour from Dynamic Tests and Comparison with Conventional Cyclic Tension–Compression Tests
Applied Sciences, 2018Co-Authors: Jean-claude Carret, Herve Di Benedetto, Cedric SauzeatAbstract:In the presented research, conventional cyclic tension–compression Tests and dynamic Tests were performed on two types of asphalt mixes (AM). For the tension–compression Tests, the complex modulus was obtained from the measurements of the axial stress and axial strain. For the dynamic Tests, an automated impact hammer equipped with a load cell and an accelerometer were used to obtain the frequency response functions (FRFs) of the specimens at different temperatures. Two methods were proposed to back-calculate the complex modulus from the FRFs at each temperature: one using the 2S2P1D (two springs, two parabolic elements and one dashpot) model and the other considering a constant complex modulus. Then, a 2S2P1D linear viscoelastic model was calibrated to simulate the global linear viscoelastic behaviour back calculated from each of the proposed methods of analysis for the dynamic Tests, and obtained from the tension–compression Test results. The two methods of analysis of dynamic Tests gave similar results. Calibrations from the tension–compression and dynamic Tests also show an overall good agreement. However, the dynamic Tests back analysis gave a slightly higher value of the norm of the complex modulus and a lower value of the phase angle compared to the tension–compression Test data. This result may be explained by the nonlinearity of AM (strain amplitude is at least 100 times smaller for dynamic Tests) and/or by ageing of the materials during the period between the tension–compression and the dynamic Tests.
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Linear Viscoelastic Behaviour of Geogrids Interface within Bituminous Mixtures
KSCE Journal of Civil Engineering, 2018Co-Authors: Reuber Freire, Cedric Sauzeat, Herve Di Benedetto, Simon Pouget, Didier LesueurAbstract:Recently, the use of geogrids as bituminous pavements reinforcement has increased in pavements construction and rehabilitation, mainly to avoid reflective cracking. One major research topic is to characterize the mechanical behaviour of actual reinforced pavement structures, from laboratory experimentation and take it into account for the design. This paper aims at presenting a methodology for the determination of the Interface Linear Viscoelastic (LVE) behaviour of specimens reinforced with geogrids. This method is based on a Tension-Compression Test on cylindrical sample, classically used for complex modulus Tests. A geogrid produced by Texinov was glued with tack coat, which constitute the studied interface. This geogrid is composed by fiberglass filaments and polyester veil, both coated with emulsion. Axial cyclic Tests at controlled strain mode of loading (Tension-Compression) were performed on the same bituminous mixtures samples with and without geogrid. The experimental data was fitted using the 2 Springs, 2 Parabolic Elements and 1 Dashpot (2S2P1D) model both for the mixtures and for the interface. The results indicate that the proposed methodology can successfully provide the interface LVE behaviour.
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Analysis and modeling of 3D complex modulus Tests on hot and warm bituminous mixtures
Mechanics of Time-Dependent Materials, 2015Co-Authors: Nguyen Hoang Pham, Cedric Sauzeat, Hervé Di benedetto, Juan A. González-león, Gilles Barreto, Aurélia Nicolaï, Marc JakubowskiAbstract:This paper presents the results of laboratory Testing of hot and warm bituminous mixtures containing Reclaimed Asphalt Pavement (RAP). Complex modulus measurements, using the tension–compression Test on cylindrical specimens, were conducted to determine linear viscoelastic (LVE) behavior. Sinusoidal cyclic loadings, with strain amplitude of approximately 50⋅10^−6, were applied at several temperatures (from −25 to +45 °C) and frequencies (from 0.03 Hz to 10 Hz). In addition to axial stresses and strains, radial strains were also measured. The complex modulus E ^∗ and complex Poisson’s ratios ν ^∗ were then obtained in two perpendicular directions. Measured values in these two directions do not indicate anisotropy on Poisson’s ratio. The time-temperature superposition principle (TTSP) was verified with good approximation in one-dimensional (1D) and three-dimensional (3D) conditions for the same values of shift factor. Experimental results were modeled using the 2S2P1D model previously developed at the University of Lyon/ENTPE. In addition, specific analysis showed that eventual damage created during complex modulus Test is very small and is equivalent to the effect of an increase of temperature of about 0.25 °C.
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Analysis and modeling of 3D complex modulus Tests on hot and warm bituminous mixtures
Mechanics of Time-Dependent Materials, 2015Co-Authors: Nguyen Hoang Pham, Cedric Sauzeat, Hervé Di benedetto, Juan A. González-león, Gilles Barreto, Aurélia Nicolaï, Marc JakubowskiAbstract:This paper presents the results of laboratory Testing of hot and warm bituminous mixtures containing Reclaimed Asphalt Pavement (RAP). Complex modulus measurements, using the tension–compression Test on cylindrical specimens, were conducted to determine linear viscoelastic (LVE) behavior. Sinusoidal cyclic loadings, with strain amplitude of approximately 50⋅10^−6, were applied at several temperatures (from −25 to +45 °C) and frequencies (from 0.03 Hz to 10 Hz). In addition to axial stresses and strains, radial strains were also measured. The complex modulus E ^∗ and complex Poisson’s ratios ν ^∗ were then obtained in two perpendicular directions. Measured values in these two directions do not indicate anisotropy on Poisson’s ratio. The time-temperature superposition principle (TTSP) was verified with good approximation in one-dimensional (1D) and three-dimensional (3D) conditions for the same values of shift factor. Experimental results were modeled using the 2S2P1D model previously developed at the University of Lyon/ENTPE. In addition, specific analysis showed that eventual damage created during complex modulus Test is very small and is equivalent to the effect of an increase of temperature of about 0.25 °C.
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Comparing Linear Viscoelastic Properties of Asphalt Concrete Measured by Laboratory Seismic and Tension–Compression Tests
Journal of Nondestructive Evaluation, 2014Co-Authors: Anders Gudmarsson, Nouffou Tapsoba, Cedric Sauzeat, Herve Di Benedetto, Nils Ryden, Björn BirgissonAbstract:Seismic measurements and conventional cyclic loading have been applied to a cylindrical asphalt concrete specimen to compare the complex modulus and complex Poisson’s ratio between the two Testing methods. The seismic moduli and Poisson’s ratio have been characterized by optimizing finite element calculated frequency response functions to measurements performed at different temperatures. An impact hammer and an accelerometer were used to measure the frequency response functions of the specimen which was placed on soft foam for free boundary conditions. The cyclic loading was performed by applying both tension and compression to the specimen while measuring the displacements in the axial and radial direction. The Havriliak–Negami and the 2S2P1D model have been used to estimate master curves of the complex modulus and complex Poisson’s ratio from the seismic and the tension–compression Tests. The seismic measurements performed at a lower strain level than the tension–compression Test give a higher absolute value of the complex moduli (e.g. $${\sim }12\,\%$$ ∼ 12 % at 100 Hz) and a lower phase angle compared to the tension–compression results.