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Merhy, Elias. "Propagation de fissure sous chargement thermomécanique cyclique anisotherme". Phd thesis, Ecole Polytechnique X, 2011. http://pastel.archives-ouvertes.fr/pastel-00658854.
Pełny tekst źródłaToitot, Denis. "Vieillissement sous chargement thermomécanique d'un matériau composite à matrice métallique". Paris, ENMP, 1991. http://www.theses.fr/1991ENMP0310.
Pełny tekst źródłaBelmahjoub, Faycal. "Comportement thermomécanique de matériaux métalliques sous divers trajets de chargement uniaxe". Montpellier 2, 1990. http://www.theses.fr/1990MON20153.
Pełny tekst źródłaPhilip, Olivier. "Structure métallique sous un chargement thermomécanique cyclique : Interaction Déformation Progressive - Fluage". Lyon, INSA, 1996. http://www.theses.fr/1996ISAL0021.
Pełny tekst źródłaThis work concerns the study of a metallic structure behaviour under a cyclic thermomechanical loading in presence of creep. Under this kind of loading, the structure may take three steady states elastic shakedown, plastic shakedown or ratchet. The security of the workmanship prescribes the conceptor to ensure that irreversible distortions remain limited as well as result stabilized after some loading cycles. For that, the conceptor may recourse either to an experimental method or to an incremental numerical approach or to simplified methods. Starting from trials of gradual distortions with creep on the model “BITUBE” and a complete characterization of the material, we test the aptitude of various viscoplastic modelisations to reproduce the actual behaviour of the structure. Then we carry out a validation of some simplified methods and we analyze their ability to integrate the creep
Michaud, Franck. "Rhéologie de panneaux composites bois/thermoplastiques sous chargement thermomécanique : aptitude au postformage". Thesis, Université Laval, 2003. http://www.theses.ulaval.ca/2003/21360/21360.pdf.
Pełny tekst źródłaThis project deals with a new type of Wood Polymer Composite (WPC) able to be post moulded. Based on wood industry processing we developed different wood/adhesive/thermoplastic fibreboards. This exploratory work leads to an innovative WPC fibreboard dedicated to structural or decorative use. In order to reach sufficient mechanical properties we managed to improve the cohesion properties. In fact, weak interfacial adhesion is a recurrent problem of all Wood/Thermoplastic products. An original coating process of MAPP onto PP fibres gave great interfacial adhesion enhancement and mechanical properties similar to MDF panels. The post thermoforming ability was measured with an original thermoforming test. These investigations, through characterisation and modelling, allowed us to determine the role of different factors and their interactions. Our post mouldable composite WPC fibreboards are porous and made-up of a fibre network which showed a complex rheological behaviour. Morphology, concentration, distribution of each components and surface interactions between them explain this behaviour.
Michaud, Franck, i Franck Michaud. "Rhéologie de panneaux composites bois/thermoplastiques sous chargement thermomécanique : aptitude au postformage". Doctoral thesis, Université Laval, 2003. http://hdl.handle.net/20.500.11794/17863.
Pełny tekst źródłaCe travail est une étude exploratoire sur la possibilité de réaliser un composite bois polymère ou WPC, rencontrant certaines exigences, notamment la post-thermoformabilité. Nous avons élaboré un panneau composite fibre de bois/thermodurcissable/thermoplastique dans la logique d’un « éco-matériau ». Ce matériau innovant est destiné à un usage structurel ou décoratif. Il est fabriqué selon un procédé de pressage à chaud d’un matelas fibreux. La problématique de l’incompatibilité d’interface entre le bois et le thermoplastique, récurrente pour bon nombre de WPC, a été résolue grâce au développement d’une technique originale d’amélioration de l’adhésion par enrobage. Les améliorations ont permis d’obtenir des caractéristiques physico-mécaniques semblables aux panneaux de densité moyenne. La composante thermoplastique nous a permis d’octroyer une aptitude de post-thermoformabilité à ce matériau. L’analyse détaillée de la composition des panneaux WPC, de leurs propriétés à différentes températures, ainsi qu’un travail de modélisation expliquent, en partie, le comportement complexe de ce nouveau WPC.
This project deals with a new type of Wood Polymer Composite (WPC) able to be post moulded. Based on wood industry processing we developed different wood/adhesive/thermoplastic fibreboards. This exploratory work leads to an innovative WPC fibreboard dedicated to structural or decorative use. In order to reach sufficient mechanical properties we managed to improve the cohesion properties. In fact, weak interfacial adhesion is a recurrent problem of all Wood/Thermoplastic products. An original coating process of MAPP onto PP fibres gave great interfacial adhesion enhancement and mechanical properties similar to MDF panels. The post thermoforming ability was measured with an original thermoforming test. These investigations, through characterisation and modelling, allowed us to determine the role of different factors and their interactions. Our post mouldable composite WPC fibreboards are porous and made-up of a fibre network which showed a complex rheological behaviour. Morphology, concentration, distribution of each components and surface interactions between them explain this behaviour.
This project deals with a new type of Wood Polymer Composite (WPC) able to be post moulded. Based on wood industry processing we developed different wood/adhesive/thermoplastic fibreboards. This exploratory work leads to an innovative WPC fibreboard dedicated to structural or decorative use. In order to reach sufficient mechanical properties we managed to improve the cohesion properties. In fact, weak interfacial adhesion is a recurrent problem of all Wood/Thermoplastic products. An original coating process of MAPP onto PP fibres gave great interfacial adhesion enhancement and mechanical properties similar to MDF panels. The post thermoforming ability was measured with an original thermoforming test. These investigations, through characterisation and modelling, allowed us to determine the role of different factors and their interactions. Our post mouldable composite WPC fibreboards are porous and made-up of a fibre network which showed a complex rheological behaviour. Morphology, concentration, distribution of each components and surface interactions between them explain this behaviour.
Michaud, Franck. "Rhéologie de panneaux composite bois/thermoplastiques sous chargement thermomécanique : aptitude au postformage". Bordeaux 1, 2003. http://www.theses.fr/2003BOR16010.
Pełny tekst źródłaThis project deals with a new type of Wood Polymer Composite (WPC) able to be post moulded. Based on wood industry processing we developed different wood/adhesive/thermoplastic fibreboards. This exploratory work leads to an innovative WPC fibreboard dedicated to structural or decorative use. In order to reach sufficient mechanical properties we managed to improve the cohesion properties. In fact, weak interfacial adhesion is a recurrent problem of all Wood/Thermoplastic products. An original coating process of MAPP onto PP fibres gave great interfacial adhesion enhancement and mechanical properties similar to MDF panels. The post thermoforming ability was measured with an original thermoforming test. These investigations, through characterisation and modelling, allowed us to determine the role of different factors and their interactions. Our post mouldable composite WPC fibreboards are porous and made-up of a fibre network which showed a complex rheological behaviour. Morphology, concentration, distribution of each components and surface interactions between them explain this behaviour
Moncel, Laurence. "Etude des mécanismes d'endommagement d'un assemblage cuivre/composite carbone-carbone sous chargement thermomécanique". Bordeaux 1, 1999. http://www.theses.fr/1999BOR10558.
Pełny tekst źródłaSbitti, Amine. "Propagation des fissures 2D et 3D planes sous chargement thermomécanique à amplitudes variables". Paris 6, 2009. http://www.theses.fr/2009PA066686.
Pełny tekst źródłaPommier, Benjamin. "Détermination de la réponse asymptotique d'une structure anélastique soumise à un chargement thermomécanique cyclique". Phd thesis, Ecole Polytechnique X, 2003. http://pastel.archives-ouvertes.fr/pastel-00004229.
Pełny tekst źródłaTaleb, Lakhdar. "Structure métallique sous un chargement thermomécanique cyclique : Effet des surcharges mécaniques de courte durée". Lyon, INSA, 1991. http://www.theses.fr/1991ISAL0038.
Pełny tekst źródłaA metallic structure submitted to a thermomechanical cyclic loading is tested and analysed about ratcheting. The effect of a short time mechanical overloads is particularly examined. From the test results a corrective factor is proposed. This factor allows to take into account the effect of temporary mechanical overloads in the aim of improving the application of a conception rule. The comparison of numerical and experimental results contributes to the validation if the models materials behaviour. In addition, interesting conclusions are given bout the performances of simplified methods of the progressive deformation expectation
Laribi, Mohamed Amine. "Caractérisation et Modélisation du comportement micromécanique des matériaux composites SMC sous chargement thermomécanique de type quasi-statique et fatigue". Thesis, Paris, ENSAM, 2018. http://www.theses.fr/2018ENAM0062/document.
Pełny tekst źródłaThe composite materials are strongly conditioned by the ability of the company to design the automotive structures under various complexes loadings such as fatigue. The aim of this thesis is to develop a multi-scale modeling coupled to a phenomenological approach in order to provide a response to the dimensioning need of structural parts subjected to cyclic loading at different temperatures of 23°C, 80°C and -30°C. By this way, the work was conducted along two main lines; firstly, an experimental investigation under monotonic and fatigue loadings. The results of this experimental study provide the necessary data for the construction of a micromechanical model which constitute the basis of the second part of this work; the predictive approaches of the fatigue lifetime for SMC composite. Thus, two hybrid, phenomenological/micromechanical, modeling approaches have been proposed. Both are based on a micromechanical modeling that allows describing the mechanical behavior of our material under monotonic loading, taking into account the microstructure and the damage phenomenon. These two predictive models require only a limited number of experimental tests and investigations but remain very reliable in their capacity to predict the lifetime of an SMC composite material under fatigue loading. The approach is validated in the case of thermomechanical sequential loadings at variable temperatures or amplitudes
Wang, Yanjun. "Fatigue Thermique à grand nombre de cycles d’un acier inoxydable austénitique : apport des mesures de champs pour l’identification du chargement et le suivi in-situ de l’endommagement". Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLN037/document.
Pełny tekst źródłaThis PhD work is devoted to the study of thermal fatigue damage of AISI 316L(N) austenitic stainless steel, a candidate material to make the primary cooling system of Sodium-cooled Fast Reators (SFRs). Initiation and propagation of crack networks can be induced by locally constrained thermal expansions or contractions of the component surface subjected to repeated thermal shocks of turbulent coolants.A campaign of high cycle thermal fatigue tests on AISI 316L(N) austenitic stainless steel has been carried out with the FLASH facility. Full field measurements have been performed to capture thermomechanical fields of monitored surfaces in thermal fatigue tests. An original procedure based on hybrid multiview correlation (HMC) uses images acquired by two visible light cameras and one infrared camera. With such a system, Lagrangian temperature fields can be measured and experimental strain or displacement fields can be used to calibrate Finite Element analyses to reproduce the thermomechanical cyclic response of the material in the region of interest. One additional benefit of the spatiotemporal synchronization of the HMC system is that the entire fatigued region has been monitored in-situ during the whole test, without interruptions, which enables crack initiation and propagation to be tracked thanks to the different modalities of the three cameras
Chatziathanasiou, Dimitrios. "Cyclic multiaxial behavior modeling of Shape Memory Alloys". Thesis, Paris, ENSAM, 2016. http://www.theses.fr/2016ENAM0015/document.
Pełny tekst źródłaNew phenomenological approaches in modeling the behavior of SMAs are needed to account for their complex response under multiaxial loading. The effect of anisotropy induces a dependence of their inelastic behavior to the direction of the loading for superelastic cases. Martensitic reorientation affects drastically material response under non-proportional loading. Repeated loading also alters certain material properties. The goal of this study is to propose a new robust thermodynamic constitutive model for SMAs with focus on equiatomic NiTi compositions to capture anisotropic martensitic transformation and reorientation of martensitic variants, always taking in mind the strong thermomechanical coupling. A new mathematical approach is introduced to account for the anisotropy of stresses and the evolution of inelastic strains during forward transformation caused by the forming conditions of SMA structures. This method is evaluated by utilizing stress-strain curves resulting from proportional loading simulated with a micromechanical model. A phenomenological thermodynamic model considering especially martensitic reorientation and exhibiting the strong thermomechanical coupling is developed. It is implemented on a numerical platform in C++, SMART, and evaluated by simulating existing non-proportional experiments. Complex structures are also simulated using Finite Element Analysis. The last part of this work concerns the experimental study of the effects of cyclic loading to the evolution of residual strain and transformation threshold of NiTi under uniaxial and biaxial testing
Chang, Xuyang. "Mesure et modélisation multiéchelle du comportement thermomécanique des alliages à mémoire de forme sous sollicitation mécanique multiaxiale". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASN009.
Pełny tekst źródłaSince their discovery, shape memory alloys (SMA) have experienced an increasing development of their industrial application (e.g medical implants, aerospace) in relation to their remarkable mechanical properties (memory effect and pseudo-elasticity). The martensitic transformation is at the heart of these properties, this type of transformation being able to be induced by a thermal loading, mechanical loading, pr a coupled thermomechanical loading (magnetic shape memory alloys are exceptions since for these alloys the magnetic loading is a third source of transformation: they will not be treated in this work). One of the major obstacles to a much more general use of these materials is a lack of robust constitutive model. Indeed, the behavior that is expected is a non-linear and generally dissipative behavior in a thermomechanical multiaxial framework. Multiscale approaches, using a set o f internal variables and potentials written at an appropriate scale can meet this challenge, with of course, the implementation of appropriate localisation and homogenization procedures. The model developed in this thesis, with a stochastic approach for the computation of the variants volume fractions (this approach can be applied to any SMA), allows a generalization of the reversible multi-scale model developed in the PhD of Anne Maynadier (2012) to an irreversible framework. An experimental test campaign was carried out in parallel with the development of the model, making it possible to identify ins intrinsic parameters and to validate it via a large number of numerical simulations. The material retained is a pseudo-elastic equiatomic NiTi. In this context, an in-situ test bench and a completely innovative identification procedure have been developed. the test bench makes it possible to combine the kinematic field measurements by digital images correlation (DIC) and phase field measurement by X-ray diffraction (XRD) simultaneously, during a uniaxial tensile test first, then during proportional and non proportional multiaxial loading tests. The kinematic field allows a continuous description of the localization phenomenon in transformation bands to be obtained; the implementation of a spatial-angular proper order decomposition (POD) method allows a robust identification of the coherent phase field with the kinematic field, and highlights interfaces and variant selection phenomena until now never reported in the literature. This multi-field comparison provides a better understanding of the band localisation phenomenon and suggest a potential track for developing a relevant structure model
Otin, Stéphane. "Lois d'endommagement incrémentales isotrope/anisotropes pour applications thermomécaniques complexes". Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2007. http://tel.archives-ouvertes.fr/tel-00341830.
Pełny tekst źródłaNsangou, Kihoulou Etienne. "Approche du comportement d'une structure métallique sous chargements thermomécaniques variables". Lyon, INSA, 1990. http://www.theses.fr/1990ISAL0065.
Pełny tekst źródła[This study concerns metallic structures under variable thermo-mechanical loadings. Such loadings could result in adaptation, accommodation or even give rise to progressive strains in the structure. An original experimental device is used to test thin cylindrical shells by applying a tensile force and a cyclic axial temperature gradient (maximum temperature of 450?c,. I. E. A maximum axial gradient of 540°c/cm). Primary mechanical _and secondary thermal overloads are applied after the structure attains a « stabilized » state. An apparatus adapted to severe thermal conditions is used to obtain informations such as the displacement field in the most loaded area of the structure while assuming axi-symetric strain. An analysis of the global and local behaviour of the structure were therefore carried out. A numerics analysis based on the INCA(CEA) code was carried out (Chaboche's model). A complete understanding of the global thermo-elastoplastic behaviour of the structure is acquired by comparing the results of the. Numerical analysis to those of the tests, for the initial cycles. An analysis of the "stabilized'' states is carried out locally by applying: - an analytical solution, - the current efficiency rule (RCCMR Juin 1985), and is then compared to the test results. ]
Hazar, Selçuk. "Theoretical and numerical analysis of fracture of shape memory alloys". Palaiseau, École nationale supérieure de techniques avancées, 2014. https://theses.hal.science/tel-01116284/document.
Pełny tekst źródłaTheoretical and numerical analysis of fracture of shape memory alloys The subject of this thesis is theoretical and numerical analysis of the fracture of SMAs. First, the size of the martensitic region surrounding the tip of an edge crack in a SMA plate is calculated analytically using the transformation function proposed by Zaki and Moumni (Zaki and Moumni, J. Mech. Phys. Sol, 2007) together with crack tip asymptotic stress equations. The transformation region is also calculated with finite elements (FE) by implementing Zaki-Moumni (ZM) model in ABAQUS through user defined material subroutine (UMAT). Transformation regions calculated analytically and computationally are compared to experimental results available in the literature (Robertson et al. , Acta Mater. , 2007). Second, fracture parameters like; Stress Intensity Factors (SIFs), J-integrals, energy release rates, crack tip opening displacements (CTODs) and T-stresses are evaluated. The objective is to understand the effect of phase transformation on fracture behavior of an edge cracked Nitinol plate under mode I loading. In the FE analysis of the edge cracked plate under mode I loading, ABAQUS is used with both ZM model, written through UMAT and built-in SMA model based on Auricchio's model (Auricchio et. Al. , Comp. Meth. Appl. Mech. Eng. , 1997). J-integrals are found to be contour dependent as a result of non-homogeneity around crack tip, therefore SIFs are directly calculated from strain energy release rate and compared to the SIFs calculated using asymptotic near-tip opening displacement field equation. Third, steady state crack growth in an SMA plate is analysed. To this end, mode I steady-state crack growth in an edge-cracked Nitinol plate is modelled using a non-local stationary method. The model is implemented in ABAQUS using ZM model by means of UMAT to determine transformation zones around the crack tip. Steady-state crack growth is first simulated without considering reverse transformation to calculate the effect of transformation on stress distribution in the wake region, and then reverse transformation is taken into account. The effect of reorientation of martensite near the crack tip as a result of non-proportional loading is also studied. The stress distribution and the phase transformation region are compared to results obtained for the case of a static crack. Finally, phase transformation region are calculated analytically around the tip of an SMA specimen under mode III loading; at first the analytical method represented by Moumni (Ziad Moumni, PhD thesis, École Nationale Des Ponts Et Chaussées, 1995) in which the material model is built based on the framework of standard materials with internal constraints (Moumni et al. Int. J. Plasticity, 2008), is revisited. Using the hodograph method, the nonlinear PDE problem is transferred to a linear boundary value problem in hodograph plane and phase transformation around the tip of a crack under mode III loading is calculated analytically. The model proposed by Moumni is improved by including the thermo-mechanical coupling. As a result of the analysis, fully coupled phase transformation region and the temperature increase due to the latent heat generation is calculated numerically around the crack tip
Attipou, Kodjo. "Étude des instabilités dans les membranes minces sous chargements thermomécaniques". Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0207/document.
Pełny tekst źródłaWrinkling is an instability phenomenon generally observed in thin structures with membrane's behavior. Those thin structures have no rigidity to flexion and are therefore used in traction. In this thesis, we developed a reduction model's technique for the modeling of wrinkling phenomenon in thin membranes. This technique, based on the double scale Fourier series, allow us to deduce from a full membrane model, a reduced membrane model that is able to take into account the global and local instability of the structure. The critical load and critical wavelength are determined analytically on one side, then numerically on the other side. Numerical exemples are conducted to validate the numerical model towards the analytical one. Numerical models studied take into account both full and reduce membrane models. The full model is simulated in Abaqus and solved numerically using the arc length method and the reduced model is implemented in Matlab and solved numerically using the asymptotic numerical method. We studied the membrane behavior under mechanical, thermal and thermo-mechanical loading. The results obtained show that the full membrane model can be replaced by the reduced one in determining critical loads and corresponding wavelengths. The gain in computation time obtained is important, due to the coarse mesh required by the reduced model. The reduced model is very sensitive to membrane's boundaries conditions and requires to have a quasi constant wavelength along the membrane width
Gu, Xiaojun. "Optimization of Shape Memory Alloy Structures with Respect to Fatigue". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLY012/document.
Pełny tekst źródłaThis thesis presents a comprehensive and effi cient structural optimization approach for shape memory alloys (SMAs) with respect to fatigue. The approach consists of three steps: First, the development of a suitable constitutive model capable of predicting, with good accuracy, the stabilized thermomechanical stress state of a SMA structure subjected to multiaxial nonproportional cyclic loading. The dependence of the saturated residual strain on temperature and loading rate is discussed. In order to overcome numerical convergence problems in situations where the phase transformation process presents little or no positivehardening, the large time increment method (LATIN) is utilized in combination with the ZM (Zaki-Moumni) model to simulate SMA structures instead of conventional incremental methods. Second, a shakedown-based fatigue criterion analogous to the Dang Van model for elastoplastic metals is derived for SMAs to predict whether a SMA structure subjected to high-cycle loading would undergo fatigue. The proposed criterion computes a fatigue factor at each material point, indicating its degree of safeness with respect to high-cycle fatigue. Third, a structural optimization approach, which can be used to improve the fatigue lifetime estimated using the proposed fatigue criterion is presented. The prospects of this work include the validation of the optimization approach with experimental data
Rouquié, Sandrine. "Vieillissement de structures composites à matrice organique soumises à des chargements thermomécaniques répétés". Poitiers, 2003. http://www.theses.fr/2003POIT2292.
Pełny tekst źródłaThe aim of this study, which is a part of the " supersonic aircraft research program" is a better understanding of damage mechanisms in composite materials submitted to cyclic variation of temperature. Thermal cycling tests performed in neutral environments (vacuum and nitrogen) and oxidative environments (air and oxygen) on various lay up of the same carbon/epoxy material revealed a significant effect of the oxygen rate on damage kinetics. Indeed the results show that a coupling between oxidation and the cyclic stresses coming from thermal variation induces a significant acceleration of matrix cracking. The use of a model of oxydation as well as the calculation of the thermal stresses made it possible to propose an experimental protocol allowing to dissociate and/or accelerate the complex phenomena involved
Gu, Xiaojun. "Optimization of Shape Memory Alloy Structures with Respect to Fatigue". Electronic Thesis or Diss., Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLY012.
Pełny tekst źródłaThis thesis presents a comprehensive and effi cient structural optimization approach for shape memory alloys (SMAs) with respect to fatigue. The approach consists of three steps: First, the development of a suitable constitutive model capable of predicting, with good accuracy, the stabilized thermomechanical stress state of a SMA structure subjected to multiaxial nonproportional cyclic loading. The dependence of the saturated residual strain on temperature and loading rate is discussed. In order to overcome numerical convergence problems in situations where the phase transformation process presents little or no positivehardening, the large time increment method (LATIN) is utilized in combination with the ZM (Zaki-Moumni) model to simulate SMA structures instead of conventional incremental methods. Second, a shakedown-based fatigue criterion analogous to the Dang Van model for elastoplastic metals is derived for SMAs to predict whether a SMA structure subjected to high-cycle loading would undergo fatigue. The proposed criterion computes a fatigue factor at each material point, indicating its degree of safeness with respect to high-cycle fatigue. Third, a structural optimization approach, which can be used to improve the fatigue lifetime estimated using the proposed fatigue criterion is presented. The prospects of this work include the validation of the optimization approach with experimental data
Ben, henni Mohamed. "Contribution à l'étude de la vibration des plaques en matériaux composites sous chargements mécanique et thermomécanique". Thesis, Reims, 2019. http://www.theses.fr/2019REIMS020.
Pełny tekst źródłaThe aim of this work is to analyze the vibration behavior of hybrid fiber composite laminates by using, on the one hand, the fourvariable high order theory taking into account the transverse shear effect for strain calculation; and on the other hand by the finite element method analysis. The equation of motion of the laminated plate is obtained using Hamilton's principle. The mathematical expressions are obtained using the Navier solution for different boundary conditions. In order to validate the proposed models, we compared our results with existing models in the literature for non-hybrid composites. The elastic moduli of the hybrid plate were calculated using the law of mixtures. Then, we studied the effects of the plate dimensions, the volume fraction, the type of fiber, the position of layers (in the case of interlayer hybridization) on the fundamental frequencies of hybrid composite plates.Since, there is no data available in the literature for hybrid composite plates, the finite element solution is used to validate the results obtained by the high order theory. The results show good accuracy of the proposed analytical solution for the prediction of the fundamental frequencies of hybrid stratified plates. Hygrothermal conditions generally degrade the rigidity of structures, we studied the effects of temperature and humidity on the stability of hybrid and non-hybrid composite plates. The results obtained for the fundamental frequencies show that the hygrothermal conditions can affect the behavior of composite plates but with a lesser effect
Merzouki, Johan. "étude des chargements thermomécaniques induits par le resserrement du trou en perçage du Ti6Al4V sous assistance cryogénique". Thesis, Paris, ENSAM, 2018. http://www.theses.fr/2018ENAM0025/document.
Pełny tekst źródłaOn account of the major economic and ecological stakes to which the aeronautic industry stakeholders had to react during the last decades, the composite mass percentage in aircrafts never stopped to increase and reached more than 50% in 2013 for the Airbus A350. Indeed, the aim always being to build lighter aircrafts, aluminum alloys (which represented more than 75% of the total mass in the 70’) were gradually replaced by other materials which were considered to have more advantageous mechanical properties to weight ratios and especially by CFRP (Carbon Fiber Reinforced Plastic). Since the CFRP/titanium alloy pair demonstrates a better thermal and electrochemical compatibility compared to the CFRP/aluminum alloy pair, the use of titanium alloys in aircraft increased as well.Therefore, many assembly cases are currently CFRP/Ti6Al4V hybrid stacks for which the goal is to be able to drill them in one shot, just as it was done for metal/metal stacks. Studies were carried out concerning hybrid stacks drilling and highlighted that the elevated temperatures during the Ti6Al4V drilling were mainly responsible for the non-fulfilment of aeronautical specifications. Based on these observations, the idea of using the cryogenic assistance emerged: cooling down the cutting area by using liquid nitrogen instead of classic modes of lubrication and cooling.Indeed, the latent heat that liquid nitrogen absorbs when it vaporizes makes it an excellent candidate to efficiently cool the cutting zone. Moreover, since it evaporates quickly at room temperature, it eliminates the need to clean the parts and to recycle the fluids while being neutral for the planet and the machine operator.This Ph.D thesis revolves around the study of cryogenic assistance effects in Ti6Al4V drilling and focuses especially on its impact on hole shrinkage. Indeed, the shape and dimensions of the drilled hole, as well as the thermomechanical loads induced by the operation depend on this little-known phenomenon. Therefore, this thesis proposes to highlight the key role of hole shrinkage in Ti6Al4V drilling and to give elements of analysis and understanding on the phenomenon, for dry and cryogenic cutting conditions
Zaki, Wael. "Modélisation thermomécanique unifiée des comportements des matériaux à mémoire de forme. Application aux chargements cycliques et à la fatigue". Phd thesis, Ecole Polytechnique X, 2006. http://pastel.archives-ouvertes.fr/pastel-00002587.
Pełny tekst źródłaChaoui, Mustapha. "Evolution de la texture d'un alliage à mémoire de forme TI-NI au cours de différents chargements thermomécaniques". Metz, 1995. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/1995/Chaoui.Mustapha.SMZ9517.pdf.
Pełny tekst źródłaWe present a study on Ti-Ni shape memory alloy (AMF) having 50% Ni. Different thermomecanic loadings were performed to know their influence on the martensitic and the austenitic states. X ray diffraction is chosen to analyse the concentration and the texture of each phase according to the loading path. Quantitative texture analysis using the vector method is applied to low symetrie material as the martensitic phase which has a monoclinic structure. We have developped a calculation method able to link orientations between the initial phase and the final one. This method allows to anticipe the texture obtained after loading and know the martensitic variants which are active during the loading process
Guo, Qiang. "Réponse thermo-mécanique des élastomères sous chargement cyclique : modélisation constitutive et expérience". Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1I023/document.
Pełny tekst źródłaEstablishing the coupling between the different inelastic phenomena, usually appearing together during the cyclic loading history, is an open issue to be addressed. The Phd report is divided into two parts. The first part is focused on filled rubbers. The effects of pre-stretch and filler content on the history-dependent cyclic response of a representative carbon-filled synthetic rubber (SBR) are qualitatively and quantitatively analyzed by using the internal state variable theory. An interpretation of the underlying physical mechanisms is proposed in which two types of dissipative network rearrangements are considered, i.e. recoverable rearrangements inducing viscoelasticity and unrecoverable rearrangements inducing damage. In order to predict the main set of inelastic fatigue effects (fatigue-induced stress-softening and hysteresis along with dissipative heating), we formulate a new thermo-viscoelastic-damage constitutive model based on the internal state variable theory. The proposed constitutive model is implemented into a finite element program and numerical applications on rubber structures are performed. The predictive capabilities of the model are verified by comparisons with our experimental observations. The second part is focused on stretch-induced crystallizable rubbers. We develop a new micro-mechanism inspired molecular chain model to describe the progressive evolution of the crystallinity degree in rubbers and the history-dependent thermo-mechanical response within the context of the thermodynamic framework. In this model, the molecular configuration of the partially crystallized single chain is analyzed and calculated by means of some statistical mechanical methods. Our approach is implemented into the micro-sphere model in the aim to introduce the crystallization-induced anisotropy and dissipation. The proposed constitutive model is then used to discuss some important aspects of the micro-mechanism and the macro-response under the equilibrium state and the non-equilibrium state involved during stretching/recovery/continuous relaxation. The model simulations are also compared to experimental data at different stretch levels and temperatures. Local fields in terms of anisotropy and dissipation are presented on illustrative numerical examples
Sridi, Ahmed. "Modélisations thermomécanique et numérique du comportement de maçonneries en briques alvéolées en terre cuite sous chargements mécanique et thermique sévères". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC047/document.
Pełny tekst źródłaOne of the major challenges of the hollow clay brick industry nowadays is to improve the fire resistance of ambitiously tall buildings, constructed with this type of bricks. The objective of our work is to develop thermo-mechanical models and related predictive numerical tools to guide the research of improved fire-performance products and therefore reduce the number of expensive experimental tests. Our main contributions are methodological. With a permanent concern of reducing the simulation costs, we establish a dialogue between observations, measurements and experimental results, on the one hand, models and simulations on the other hand. In this regard, measurements, obtained during the experimental tests we carried out, are used to progressively develop relevant models, by examining the importance of thermal phenomena (conduction, convection and radiation), by looking for the just right transfer relations (with respect to our objectives) at the multiple interfaces of the problem and by considering the phase change of bound water. After identifying the good thermo-mechanical mechanisms, we calibrate some numerical parameters by solving an inverse problem. Moreover, to efficiently help the design of new products, we employ the multi-model and multi-scale Arlequin framework to formulate, approximate and solve resulting thermo-mechanical problems. The latters include areas of thermal gradient concentrations and mechanical singularities. Our global approach implemented and tested by developing codes and enriching others, shows a real ability of our methodology to efficiently compute structures made of hollow bricks, when subjected to thermomechanical load
Agode, Kofi Edoh. "Analyse et modélisation du comportement à l’usure des outils de coupe en carbure de tungstène pour différentes teneurs en cobalt lors de l’usinage de l’alliage de titane Ti-6Al-4V". Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0141.
Pełny tekst źródłaDue to their high hardness and wear resistance, cemented carbide (WC-Co) is the main material used to manufacture machining tools and forming tooling, as well as wear parts requiring high hardness and high precision. The modification of tungsten carbide microstructure, and more particularly its cobalt content, is currently attracting the greatest interest from manufacturers to develop new grades tools with high performance, and then expand new markets.This thesis aims to study the effect of the cobalt content of carbide tools on the measured values and wear mechanisms when machining hard superalloys such as the aeronautical titanium alloys Ti-6Al-4V. Both experimental and numerical research work are devoted on one hand to the understanding of the microscopic damage mechanisms leading to the macroscopic wear of the WC-Co composite and on the other hand, to the influence of the cobalt content on the behavior of the WC-Co taking into account the mechanical-microstructure-damage coupling.On the basis of an experimental analysis, the identification of the macroscopic and microscopic physical phenomena involved at the tool/chip and tool/workpiece contact interfaces was conducted. Machining tests were firstly carried out on the tool-material couple WC-Co/Ti-6Al-4V with different cobalt contents for the tools (from 6 to 15%). In a second step, a tribological characterization of the same tool-material couple was carried out to evaluate the influence of the cobalt content and the contact conditions (sliding speed, applied force) on the friction coefficient and wear. However, the inaccessibility of the contact zones during machining and the tribological tests did not allow a complete description of the wear mechanisms observed, whether macroscopic mechanisms (adhesion, abrasion, deformation, ...), or microscopic mechanisms (cracking, damage of the WC and Co phases). The numerical simulation using finite elements (FE) proved to be a very interesting complementary tool for the analysis of these wear mechanisms.Our modeling strategy focused on the response of WC-Co at the microstructure scale for the thermomechanical loading close to that obtained by machining. The proposed model takes into account the behavior of the WC and Co phases separately and that of the interfaces WC-WC and WC-Co of the composite. This strategy allowed to study and identify parameters influencing the behavior of the microstructure from the elastic stage to the damage initiation. A good agreement was obtained between the results of the numerical behavior at the initiation of damage in the microstructure and those of the experimental observations in terms of the effects of the cobalt content in the tungsten carbide and of the applied machining conditions
Lopez, Delphine. "Comportement d’un thermoplastique renforcé de fibres de verre soumis à des chargements thermo-mécaniques". Thesis, Lorient, 2018. http://www.theses.fr/2018LORIS488/document.
Pełny tekst źródłaDiscontinuous fibers reinforced thermoplastic materials have been widely used for several years in the automotive industry. These parts must resist demanding service life conditions and must meet thermo- mechanical specifications. Indeed, structural automotive spare parts have to endure high temperatures, like a few tens of degrees Celsius, for a long duration, at least a few hours. As an example, a structural part of tailgate is subject to high mechanical loading, associated to strong temperature variations, during the validation test, regarding specifications. The purpose of this work is to improve the design of complex industrial parts, like the tailgate in quasi-static domain, by relying on numerical simulation. One of the challenges related to the use of such material, is to have a reliable virtual design of industrial parts by predicting the geometrical variations during service life conditions, and residual strain. Therefore, it is necessary to characterize and to model the thermo-mechanical behavior of the tailgate material, a polypropylene matrix reinforced with discontinuous glass fibers, with a given mass fraction of 40%
Bourgogne, Quentin. "Contribution à l’étude du comportement mécanique d’un PPS/GF40 sous différents chargements avec prise en compte des effets de l’environnement de sollicitation : étude expérimentale et modélisation multi-échelle pour application au développement de pièces automobiles". Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0181.
Pełny tekst źródłaThis thesis presents an experimental and theoretical study conducted on a PPS/GF40 and its matrix. Widely used for under-the-hood applications in the automotive industry, those materials are subjected to high temperatures and aging effects of cooling liquid. Therefore, the understanding of those phenomena is essential to design mechanical parts. Thus, an experimental campaign in the tensile mode has been carried out with different temperatures and glycol proportions in the cooling liquid, for monotonic and cyclic loadings on neat and reinforced PPS. The results of these tests allowed us to highlight some of the main physical phenomena occurring during these solicitations under tough hydro-thermal conditions. Taking into account this analysis, a visco-elasto-pseudo-viscoplastic model is proposed. Moreover, this model allows the consideration of the cooling liquid effects and its constituents by temperature/humidity equivalence. The accuracy of the model was confronted to an artificial intelligence based one, in order to study the maximal accuracy physically reachable. Finally, the evolution of the model parameters has been studied with the adjunction of short glass fibres and for specifics orientation distribution. Starting from the study of the mechanical behavior of the PPS matrix, an analytical homogenization was then performed. Differences between experimental and predicted plastic behaviors were highlighted. Finite element analyses considering inter-phase damage were done at different temperatures and for several fiber orientations so to explain differences arising between analytical approach and experimental results. This work allowed a study of the evolution of the impact of this damage on mechanical properties as a function of temperature and fiber orientation. This work led to highlight a weakening of the fiber/matrix interface for a liquid aged composite and to quantify the decrease of the interface properties. Finally, fatigue behavior of the composite is studied as a function of fiber orientation. The modeling parameters determined from the study of the monotonic behavior of the composite were taken into account to propose a prediction of the Wöhler curves as a function of temperature. The prediction of the Wöhler curves as a function of temperature being possible, a 1D model was then proposed in order to evaluate the increase of temperature due to self-heating phenomenon during fatigue loading, considering ageing consequences
Saai, Afaf. "Modèle physique de la plasticité d'un cristal métallique CFC soumis à des chargements alternés : contribution à la définition d'une modélisation multiéchelles de la mise en forme des métaux". Phd thesis, Chambéry, 2007. http://tel.archives-ouvertes.fr/tel-00335219.
Pełny tekst źródłaCette thèse est une contribution à l'établissement d'un modèle de comportement plastique destiné à être utilisé pour la simulation numérique des opérations de mise en forme. Le parti a été pris de recourir à un modèle micromécanique dont les variables sont des paramètres micro-structuraux intrinsèques comme les densités de dislocations et leurs distributions sur chaque système de glissement. Le modèle traite des chargements alternés dans un cadre physique unifié défini pour l'ensemble des équations constitutives décrivant l'écrouissage.
Au-delà de l'intérêt de définir un modèle particulier, ce travail apporte une contribution à la mise en œuvre des différentes étapes qui doivent conduire à son utilisation dans une simulation numérique macroscopique. Il s'agit de définir un protocole reproductible, plutôt indépendant du modèle considéré et exploitable pour d'autres modélisations. En particulier, des protocoles expérimentaux sont définis pour produire des données dans des conditions reproductibles. Des moyens de caractérisation récents comme l'analyse d'images dans les domaines visible et infrarouge sont utilisés pour étudier la réponse expérimentale thermomécanique de différents échantillons à caractère fortement cristallin. Ensuite, l'implantation du modèle dans un code éléments finis commercial permet d'envisager des simulations complexes qui, si elles ne s'adressent pas actuellement à des opérations d'emboutissage, comportent toutefois les ingrédients pour les traiter.
Ce travail, à l'interface de nombreux champs disciplinaires, apporte donc une contribution au développement des modèles de comportement plastique des matériaux métalliques qui porte sur l'ensemble des briques nécessaires au développement de simulations numériques utilisant des modèles à caractère physique.
Gaillard, Laura. "Comportement thermo-hydro-mécanique des agrégats d'enrobés compactés non saturés". Thesis, Strasbourg, 2019. https://publication-theses.unistra.fr/public/theses_doctorat/2019/laura_gaillard_2019_ED269.pdf.
Pełny tekst źródłaReclaimed Asphalt Pavement (RAP) comes from the demolition of pavements. Its reuse is an alternative to virgin materials, to reduce the environmental impact. The ORRAP project develops a cold recycling without binder addition, in base and subbase layers of low traffic pavements. The traffic solicitations lead to damages: the rutting and the fatigue cracking. The objective of this thesis is to study the thermo-hydro-mechanical behaviour of RAP. A series of triaxial tests was carried out at several temperatures, water contents and frequencies. The experimental work allowed to characterise permanent and resilient behaviours. Based on experimental results, the resilient behaviour was described by a first non-linear elastic analytical model, and then by a second viscoelastic analytical model. Using the discrete element method, numerical simulations with a viscoelastic contact model predicted the resilient modulus. Finally, two full scale test sections were built
"Rhéologie de panneaux composites bois/thermoplastiques sous chargement thermomécanique : aptitude au postformage". Thesis, Université Laval, 2003. http://www.theses.ulaval.ca/2003/21360/21360.pdf.
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