http://hdl.handle.net/10985/13599 Fri, 17 Apr 2026 09:57:10 GMT 2026-04-17T09:57:10Z https://sam.ensam.eu:443/bitstream/id/7bdeb98f-f13e-4eae-aa72-e2e1110f2c09/ http://hdl.handle.net/10985/13599 http://hdl.handle.net/10985/11186 Torsional Vibrations of Fluid-Filled Multilayered Transversely Isotropic Finite Circular Cylinder ABASSI, Wafik; RAZAFIMAHERY, Fulgence; EL BAROUDI, Adil An analytical and numerical study for the torsional vibrations of viscous fluid-filled three-layer transversely isotropic cylinder is presented in this paper. The equations of motion of solid and fluid are respectively formulated using the constitutive equations of a transversely isotropic cylinder and the constitutive equations of a viscous fluid. The analytical solution of the frequency equation is obtained using the boundary conditions at the free surface of the solid layer and the boundary conditions at the fluid–solid interface. The frequency equation is deduced and analytically solved using the symbolic Software Mathematica. The finite element method using Comsol Multiphysics Software results are compared with present method for validation and an acceptable match between them were obtained. It is shown that the results from the proposed method are in good agreement with numerical solutions. The influence of fluid dynamic viscosity is thoroughly analyzed and the effect of the isotropic properties on the natural frequencies is also investigated. Fri, 01 Jan 2016 00:00:00 GMT http://hdl.handle.net/10985/11186 2016-01-01T00:00:00Z ABASSI, Wafik RAZAFIMAHERY, Fulgence EL BAROUDI, Adil An analytical and numerical study for the torsional vibrations of viscous fluid-filled three-layer transversely isotropic cylinder is presented in this paper. The equations of motion of solid and fluid are respectively formulated using the constitutive equations of a transversely isotropic cylinder and the constitutive equations of a viscous fluid. The analytical solution of the frequency equation is obtained using the boundary conditions at the free surface of the solid layer and the boundary conditions at the fluid–solid interface. The frequency equation is deduced and analytically solved using the symbolic Software Mathematica. The finite element method using Comsol Multiphysics Software results are compared with present method for validation and an acceptable match between them were obtained. It is shown that the results from the proposed method are in good agreement with numerical solutions. The influence of fluid dynamic viscosity is thoroughly analyzed and the effect of the isotropic properties on the natural frequencies is also investigated. http://hdl.handle.net/10985/11185 Vibration Analysis of Euler-Bernoulli Beams Partially Immersed in a Viscous Fluid ABASSI, Wafik; RAZAFIMAHERY, Fulgence; EL BAROUDI, Adil The vibrational characteristics of a microbeam are well known to strongly depend on the fluid in which the beam is immersed. In this paper, we present a detailed theoretical study of the modal analysis of microbeams partially immersed in a viscous fluid. A fixed-free microbeamvibrating in a viscous fluid is modeled using the Euler-Bernoulli equation for the beams.The unsteady Stokes equations are solved using a Helmholtz decomposition technique in a two-dimensional plane containing the microbeams cross sections.The symbolic softwareMathematica is used in order to find the coupled vibration frequencies of beams with two portions. The frequency equation is deduced and analytically solved.The finite element method using ComsolMultiphysics software results is compared with present method for validation and an acceptable match between them was obtained. In the eigenanalysis, the frequency equation is generated by satisfying all boundary conditions. It is shown that the present formulation is an appropriate and new approach to tackle the problem with good accuracy. Fri, 01 Jan 2016 00:00:00 GMT http://hdl.handle.net/10985/11185 2016-01-01T00:00:00Z ABASSI, Wafik RAZAFIMAHERY, Fulgence EL BAROUDI, Adil The vibrational characteristics of a microbeam are well known to strongly depend on the fluid in which the beam is immersed. In this paper, we present a detailed theoretical study of the modal analysis of microbeams partially immersed in a viscous fluid. A fixed-free microbeamvibrating in a viscous fluid is modeled using the Euler-Bernoulli equation for the beams.The unsteady Stokes equations are solved using a Helmholtz decomposition technique in a two-dimensional plane containing the microbeams cross sections.The symbolic softwareMathematica is used in order to find the coupled vibration frequencies of beams with two portions. The frequency equation is deduced and analytically solved.The finite element method using ComsolMultiphysics software results is compared with present method for validation and an acceptable match between them was obtained. In the eigenanalysis, the frequency equation is generated by satisfying all boundary conditions. It is shown that the present formulation is an appropriate and new approach to tackle the problem with good accuracy. http://hdl.handle.net/10985/23025 On the nucleation of deformation twins at the early stages of plasticity ABDOLVAND, Hamidreza; LOUCA, Karim; MAREAU, Charles; MAJKUT, Marta; WRIGHT, Jonathan Understanding the deformation mechanisms of hexagonal close-packed (HCP) polycrystals at the grain scale is crucial for developing both macro and micro scale predictive models. Slip and twinning are the two main deformation mechanisms of HCP polycrystals at room temperature. In this paper, the development of grain-level stress tensors during nucleation and growth of twins is investigated. A pure zirconium specimen with HCP crystals is deformed in-situ while the centre-of-mass, orientation, elastic strain, and stress of individual grains are measured by three-dimensional synchrotron X-ray diffraction (3D-XRD). The observed microstructure is subsequently imported into a crystal plasticity finite element (CPFE) model to simulate the deformation of the polycrystal. The evolution of stress in twin-parent pairs at the early stages of plasticity, further into plasticity zone, and unload is studied. It is shown that twins do not relax very much at the nucleation step, but the difference between the measured stress in the twin and parent increases further into plastic zone where twins relax. While at the early stages of plasticity all six twin variants are active, a slightly better estimation of active variants is obtained using the measured grain-resolved stress tensors. Mon, 20 Jul 2020 00:00:00 GMT http://hdl.handle.net/10985/23025 2020-07-20T00:00:00Z ABDOLVAND, Hamidreza LOUCA, Karim MAREAU, Charles MAJKUT, Marta WRIGHT, Jonathan Understanding the deformation mechanisms of hexagonal close-packed (HCP) polycrystals at the grain scale is crucial for developing both macro and micro scale predictive models. Slip and twinning are the two main deformation mechanisms of HCP polycrystals at room temperature. In this paper, the development of grain-level stress tensors during nucleation and growth of twins is investigated. A pure zirconium specimen with HCP crystals is deformed in-situ while the centre-of-mass, orientation, elastic strain, and stress of individual grains are measured by three-dimensional synchrotron X-ray diffraction (3D-XRD). The observed microstructure is subsequently imported into a crystal plasticity finite element (CPFE) model to simulate the deformation of the polycrystal. The evolution of stress in twin-parent pairs at the early stages of plasticity, further into plasticity zone, and unload is studied. It is shown that twins do not relax very much at the nucleation step, but the difference between the measured stress in the twin and parent increases further into plastic zone where twins relax. While at the early stages of plasticity all six twin variants are active, a slightly better estimation of active variants is obtained using the measured grain-resolved stress tensors. http://hdl.handle.net/10985/10264 Kinetic Theory Microstructure Modeling in Concentrated Suspensions ABISSET-CHAVANNE, Emmanuelle; MEZHER, Rabih; LE CORRE, Steven; AMMAR, Amine; CHINESTA SORIA, Francisco When suspensions involving rigid rods become too concentrated, standard dilute theories fail to describe their behavior. Rich microstructures involving complex clusters are observed, and no model allows describing its kinematics and rheological effects. In previous works the authors propose a first attempt to describe such clusters from a micromechanical model, but neither its validity nor the rheological effects were addressed. Later, authors applied this model for fitting the rheological measurements in concentrated suspensions of carbon nanotubes (CNTs) by assuming a rheo-thinning behavior at the constitutive law level. However, three major issues were never addressed until now: (i) the validation of the micromechanical model by direct numerical simulation; (ii) the establishment of a general enough multi-scale kinetic theory description, taking into account interaction, diffusion and elastic effects; and (iii) proposing a numerical technique able to solve the kinetic theory description. This paper focuses on these three major issues, proving the validity of the micromechanical model, establishing a multi-scale kinetic theory description and, then, solving it by using an advanced and efficient separated representation of the cluster distribution function. These three aspects, never until now addressed in the past, constitute the main originality and the major contribution of the present paper. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/10264 2013-01-01T00:00:00Z ABISSET-CHAVANNE, Emmanuelle MEZHER, Rabih LE CORRE, Steven AMMAR, Amine CHINESTA SORIA, Francisco When suspensions involving rigid rods become too concentrated, standard dilute theories fail to describe their behavior. Rich microstructures involving complex clusters are observed, and no model allows describing its kinematics and rheological effects. In previous works the authors propose a first attempt to describe such clusters from a micromechanical model, but neither its validity nor the rheological effects were addressed. Later, authors applied this model for fitting the rheological measurements in concentrated suspensions of carbon nanotubes (CNTs) by assuming a rheo-thinning behavior at the constitutive law level. However, three major issues were never addressed until now: (i) the validation of the micromechanical model by direct numerical simulation; (ii) the establishment of a general enough multi-scale kinetic theory description, taking into account interaction, diffusion and elastic effects; and (iii) proposing a numerical technique able to solve the kinetic theory description. This paper focuses on these three major issues, proving the validity of the micromechanical model, establishing a multi-scale kinetic theory description and, then, solving it by using an advanced and efficient separated representation of the cluster distribution function. These three aspects, never until now addressed in the past, constitute the main originality and the major contribution of the present paper. http://hdl.handle.net/10985/10059 A new methodology for designing heat treated components in fatigue ABRIVARD, Benjamin; DELHAYE, Philippe; MOREL, Franck; PESSARD, Etienne This study is dedicated to the effect of the heat treatment on the fatigue strength of an automobile rear axle beam and aims to propose a suitable and reliable methodology for the fatigue design. The rear axle beam is made of sheet metal (22MnB5); the microstructure is initially ferrito-pearlitic before the heat treatment and is martensitic after. A vast experimental campaign has been undertaken to investigate the behaviour, and more specially, the fatigue damage mechanisms observed for both treated and non-treated material, under different loading conditions: tension and shear test with different load ratios. In order to test the sheet metal in shear an original fatigue test apparatus is used. A probabilistic approach using the weakest link concept is introduced to model the fatigue behaviour. This approach leads naturally to a probabilistic Kitagawa type diagram, which in this case explains the relationship between the influence of the heat treatment and the microstructural heterogeneities. Integrate in a numerical model, this methodology permit to predict the effect of a local heat treatment on the fatigue strength of the components. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/10059 2013-01-01T00:00:00Z ABRIVARD, Benjamin DELHAYE, Philippe MOREL, Franck PESSARD, Etienne This study is dedicated to the effect of the heat treatment on the fatigue strength of an automobile rear axle beam and aims to propose a suitable and reliable methodology for the fatigue design. The rear axle beam is made of sheet metal (22MnB5); the microstructure is initially ferrito-pearlitic before the heat treatment and is martensitic after. A vast experimental campaign has been undertaken to investigate the behaviour, and more specially, the fatigue damage mechanisms observed for both treated and non-treated material, under different loading conditions: tension and shear test with different load ratios. In order to test the sheet metal in shear an original fatigue test apparatus is used. A probabilistic approach using the weakest link concept is introduced to model the fatigue behaviour. This approach leads naturally to a probabilistic Kitagawa type diagram, which in this case explains the relationship between the influence of the heat treatment and the microstructural heterogeneities. Integrate in a numerical model, this methodology permit to predict the effect of a local heat treatment on the fatigue strength of the components. http://hdl.handle.net/10985/7514 The Effect of microstructural heterogeneities on the fatigue behaviour of 22MnB5 sheet steel ABRIVARD, Benjamin; PESSARD, Etienne; MOREL, Franck; DELHAYE, Philippe; GERIN, Benjamin This work deals with the effect of heat treatment on the fatigue strength of a rear axial beam and aims to propose a methodology suitable and reliable for fatigue design. The rear axial beam is made of sheet metal (22MnB5); the initial microstructure is ferrito-pearlitic and martensitic after the treatment. A vast experimental campaign has been undertaken to investigate the behaviour and more specially the fatigue damage mechanisms observed (with material treated and no treated) under different loading conditions: tension and shear test with different load ratios. To test a sheet on shearing an original test is also used. SEM observations of fatigue failure surfaces, for both heat treated and nontreated specimens, show that the fatigue cracks initiate from inclusions for the specimens loaded in tension. The experiments show that the damage mechanism depends on the applied loading condition: for shear loadings no inclusions are observed at the crack initiation site. A probabilistic approach using the weakest link concept is used to model the fatigue. This approach leads naturally to a probabilistic Kitagawa type diagram, which in this case explains the relationship between the influence of the heat treatment and the microstructural heterogeneities. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/7514 2013-01-01T00:00:00Z ABRIVARD, Benjamin PESSARD, Etienne MOREL, Franck DELHAYE, Philippe GERIN, Benjamin This work deals with the effect of heat treatment on the fatigue strength of a rear axial beam and aims to propose a methodology suitable and reliable for fatigue design. The rear axial beam is made of sheet metal (22MnB5); the initial microstructure is ferrito-pearlitic and martensitic after the treatment. A vast experimental campaign has been undertaken to investigate the behaviour and more specially the fatigue damage mechanisms observed (with material treated and no treated) under different loading conditions: tension and shear test with different load ratios. To test a sheet on shearing an original test is also used. SEM observations of fatigue failure surfaces, for both heat treated and nontreated specimens, show that the fatigue cracks initiate from inclusions for the specimens loaded in tension. The experiments show that the damage mechanism depends on the applied loading condition: for shear loadings no inclusions are observed at the crack initiation site. A probabilistic approach using the weakest link concept is used to model the fatigue. This approach leads naturally to a probabilistic Kitagawa type diagram, which in this case explains the relationship between the influence of the heat treatment and the microstructural heterogeneities. http://hdl.handle.net/10985/11342 The effect of machining defects on the fatigue behaviour of the Al7050 alloy ABROUG, Foued; PESSARD, Etienne; GERMAIN, Guénaël; MOREL, Franck; CHOVE, Etienne During the High Speed Machining (HSM) of aircraft components, geometrical defects, such as mismatches or chatters, can be created. To obtain a high surface quality, an expensive manual grinding operation is systematically done to remove these defects. The aim of this study is to identify the impact of HSM defects on the fatigue behaviour of the aluminium alloy Al7050. After listing and reproducing the most frequently observed surface defects, fatigue tests are conducted under fully reversed plane bending loads. Investigations carried out in previous work showed that residual stresses and the strain hardening introduced by machining under these conditions can be neglected. Therefore, only the geometric aspect of the surface integrity is considered in this study. The results show that the fatigue strength decreases only when the surface roughness is significantly degraded. It is also pointed out that manual grinding allows the effect of the machining defects to be removed from the fatigue behaviour. In order to predict the influence of the surface condition on the fatigue behaviour, a numerical approach based on the real surface topology is also developed. Crack initiation sites that are numerically identified are in agreement with experimental results. Numerical simulation results are compared to the predictions of different fatigue criteria from the literature and discussed over a wide range of surface defects. Fri, 01 Jan 2016 00:00:00 GMT http://hdl.handle.net/10985/11342 2016-01-01T00:00:00Z ABROUG, Foued PESSARD, Etienne GERMAIN, Guénaël MOREL, Franck CHOVE, Etienne During the High Speed Machining (HSM) of aircraft components, geometrical defects, such as mismatches or chatters, can be created. To obtain a high surface quality, an expensive manual grinding operation is systematically done to remove these defects. The aim of this study is to identify the impact of HSM defects on the fatigue behaviour of the aluminium alloy Al7050. After listing and reproducing the most frequently observed surface defects, fatigue tests are conducted under fully reversed plane bending loads. Investigations carried out in previous work showed that residual stresses and the strain hardening introduced by machining under these conditions can be neglected. Therefore, only the geometric aspect of the surface integrity is considered in this study. The results show that the fatigue strength decreases only when the surface roughness is significantly degraded. It is also pointed out that manual grinding allows the effect of the machining defects to be removed from the fatigue behaviour. In order to predict the influence of the surface condition on the fatigue behaviour, a numerical approach based on the real surface topology is also developed. Crack initiation sites that are numerically identified are in agreement with experimental results. Numerical simulation results are compared to the predictions of different fatigue criteria from the literature and discussed over a wide range of surface defects. http://hdl.handle.net/10985/16575 HCF of AA7050 alloy containing surface defects: Study of the statistical size effect ABROUG, Foued; PESSARD, Etienne; GERMAIN, Guénaël; MOREL, Franck This work investigates the effect of artificial surface defects on the fatigue limit of a 7050 Aluminum alloy (AlZn6CuMgZr). A large fatigue testing campaign under fully reversed plane bending loading is undertaken on specimen with artificial surface hemispherical defects. The defect number was varied from 1 to 44 defects per specimen and the diameter size ranged from 60 μm to 800 μm. The test results allow the characterization of both the defect effect and scale effect on the fatigue behavior of the material. A probabilistic approach based on the weakest link concept together with a fatigue crack initiation criterion are used to account for the stress distribution and the size of the highly stressed volume. This approach leads to a probabilistic Kitagawa-Takahashi type diagram, which in this case explains the relationship between the defect size and the scale effect on the fatigue strength. The predictions show good agreement with the experimental results and illustrate the importance of taking the scale effect into account when designing components containing different surface defects types or roughness patterns. Mon, 01 Jan 2018 00:00:00 GMT http://hdl.handle.net/10985/16575 2018-01-01T00:00:00Z ABROUG, Foued PESSARD, Etienne GERMAIN, Guénaël MOREL, Franck This work investigates the effect of artificial surface defects on the fatigue limit of a 7050 Aluminum alloy (AlZn6CuMgZr). A large fatigue testing campaign under fully reversed plane bending loading is undertaken on specimen with artificial surface hemispherical defects. The defect number was varied from 1 to 44 defects per specimen and the diameter size ranged from 60 μm to 800 μm. The test results allow the characterization of both the defect effect and scale effect on the fatigue behavior of the material. A probabilistic approach based on the weakest link concept together with a fatigue crack initiation criterion are used to account for the stress distribution and the size of the highly stressed volume. This approach leads to a probabilistic Kitagawa-Takahashi type diagram, which in this case explains the relationship between the defect size and the scale effect on the fatigue strength. The predictions show good agreement with the experimental results and illustrate the importance of taking the scale effect into account when designing components containing different surface defects types or roughness patterns. http://hdl.handle.net/10985/16579 The influence of machined topography on the HCF behaviour of the Al7050 alloy ABROUG, Foued; PESSARD, Etienne; GERMAIN, Guénaël; MOREL, Franck; CHOVE, Etienne The aim of this study is to identify the impact of High Speed Machining defects on the fatigue behaviour of the Al7050 aluminium alloy. A vast experimental campaign under fully reversed plane bending loads containing different surface states has been undertaken to characterize the effect of the surface topography on the fatigue behaviour. The results show that the fatigue strength decreases only when the surface roughness is significantly degraded. It is also pointed out that manual grinding eliminates the effect of the machining defects on the fatigue behaviour. In order to predict the influence of the surface condition on the fatigue behaviour, a numerical approach based on the real surface topology has been developed. It is shown that the numerically identified crack initiation sites are in agreement with the experimental results. A probabilistic approach based on the weakest link concept, associated with the definition of a stress based crack initiation threshold has been integrated in a FE model. This approach leads naturally to a probabilistic Kitagawa type diagram, which in this case explains the relationship between the size defect and the scale effect on the fatigue strength. Mon, 01 Jan 2018 00:00:00 GMT http://hdl.handle.net/10985/16579 2018-01-01T00:00:00Z ABROUG, Foued PESSARD, Etienne GERMAIN, Guénaël MOREL, Franck CHOVE, Etienne The aim of this study is to identify the impact of High Speed Machining defects on the fatigue behaviour of the Al7050 aluminium alloy. A vast experimental campaign under fully reversed plane bending loads containing different surface states has been undertaken to characterize the effect of the surface topography on the fatigue behaviour. The results show that the fatigue strength decreases only when the surface roughness is significantly degraded. It is also pointed out that manual grinding eliminates the effect of the machining defects on the fatigue behaviour. In order to predict the influence of the surface condition on the fatigue behaviour, a numerical approach based on the real surface topology has been developed. It is shown that the numerically identified crack initiation sites are in agreement with the experimental results. A probabilistic approach based on the weakest link concept, associated with the definition of a stress based crack initiation threshold has been integrated in a FE model. This approach leads naturally to a probabilistic Kitagawa type diagram, which in this case explains the relationship between the size defect and the scale effect on the fatigue strength. http://hdl.handle.net/10985/16560 A probabilistic approach to study the effect of machined surface states on HCF behavior of a AA7050 alloy ABROUG, Foued; PESSARD, Etienne; GERMAIN, Guénaël; MOREL, Franck The aim of this study is to understand the impact of periodic surface micro-geometry patterns (obtained by High Speed Machining process) on the fatigue behavior of the AA7050 aluminium alloy and to define a proper defect acceptability criterion. It must be able to account for a large range of surface defects and of component sizes and geometries (wings, brackets, frames, etc.). A vast experimental campaign under fully reversed plane bending loads containing different surface states has been undertaken to characterize the effect of the surface topography on the fatigue behavior. The results show that the fatigue strength decreases when the surface roughness is significantly degraded. In order to predict the influence of the surface condition on the fatigue behavior, a numerical approach based on the real surface topology has been developed. It is shown that the numerically identified crack initiation sites are in agreement with the experimental results. A probabilistic approach based on the weakest link concept, associated with the definition of a stress based crack initiation threshold has been integrated in a FE model. This approach leads to a probabilistic diagram inspired from the Kitagawa type diagram, which explains the relationship between the surface and the scale effect on the fatigue strength. Mon, 01 Jan 2018 00:00:00 GMT http://hdl.handle.net/10985/16560 2018-01-01T00:00:00Z ABROUG, Foued PESSARD, Etienne GERMAIN, Guénaël MOREL, Franck The aim of this study is to understand the impact of periodic surface micro-geometry patterns (obtained by High Speed Machining process) on the fatigue behavior of the AA7050 aluminium alloy and to define a proper defect acceptability criterion. It must be able to account for a large range of surface defects and of component sizes and geometries (wings, brackets, frames, etc.). A vast experimental campaign under fully reversed plane bending loads containing different surface states has been undertaken to characterize the effect of the surface topography on the fatigue behavior. The results show that the fatigue strength decreases when the surface roughness is significantly degraded. In order to predict the influence of the surface condition on the fatigue behavior, a numerical approach based on the real surface topology has been developed. It is shown that the numerically identified crack initiation sites are in agreement with the experimental results. A probabilistic approach based on the weakest link concept, associated with the definition of a stress based crack initiation threshold has been integrated in a FE model. This approach leads to a probabilistic diagram inspired from the Kitagawa type diagram, which explains the relationship between the surface and the scale effect on the fatigue strength.