Literatura académica sobre el tema "Propriétés viscoplastiques"
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Tesis sobre el tema "Propriétés viscoplastiques"
El-Houdaigui, Fouad. "Problèmes d'homogénéisation pour des matériaux hétérogènes viscoplastiques". Metz, 2001. http://docnum.univ-lorraine.fr/public/UPV-M/Theses/2001/El_Houdaigui.Fouad.SMZ0118.pdf.
Texto completoAn extension of the Eshelby problem for non-linear viscous materials is considered. An ellipsoidal heterogeneity is embedded in an infinite matrix. The material properties are assumed to be uniform within the ellipsoid and in the matrix. The problem of determining the average strain rate in the ellipsoid terms of the overall applied strain rate is solved in an approximate way. The method is based on the non-incremental tangent formulation of the non-linear matrix behavior (Molinari, A. , Canova, G. R. , Ahzi, S. , 1987. A self consistent approach of the large deformation polyctristal plasticity. Acta Metall. 35, 2983-2994). In the present work this approximate solution is verified with a good agreement by comparing to the finite element calculations for various inclusion and loading conditions. The differential scheme is using the obtained behavior of the composite depends on which phase is considered to be constituted by the inclusions. This is become the interaction is different between the inclusion and the matrix when they are exchanged. Results will be given for both cases in the applications part
Briottet, Laurent. "Etude théorique de l'évolution du comportement de matériaux viscoplastiques endommages". Paris, ENMP, 1994. http://www.theses.fr/1994ENMP0482.
Texto completoSkalski, Pawel. "Analyse des propriétés viscoplastiques du fluide magnétorhéologique dans des conditions de travail d'un amortisseur". Phd thesis, Université d'Orléans, 2011. http://tel.archives-ouvertes.fr/tel-00623116.
Texto completoSkalski, Pawell. "Analyse des propriétés viscoplastiques du fluide magnétorhéologique dans des conditions de travail d'un amortisseur". Thesis, Orléans, 2011. http://www.theses.fr/2011ORLE2003/document.
Texto completoThe main goal of this dissertation is a mathematical description and an analysis of viscoplasticproperties of magnetorheological fluid, in operational conditions of the damper’s work, as well as the determining the optimum, in view of indicated values of parameters, size of the gap for the MR fluid to flow, in these devices. A detailed analysis of literature was made. The scope of research work has been limited to two types of magnetorheological devices: the shock absorber LORD RD 1005-3 and the MR damper prototype T-MR SiMR -132 DG. On the basis of performed experiments, it has been estimated i.e.: conventional yield point and the maximum shear stress of analyzed MR fluid, including variable shear rate, intensity of current flowing in a solenoid, liquid’s temperature and the gap height. Identified viscoplastic models were used to develop a simulation that verifies the proposed mathematical model which describes the behaviour of MR fluid in operating gap of machine’s head, with data derived from performed experiments
Zeng, Tao. "Modélisation multi-échelle des comportements plastiques et viscoplastiques des géomatériaux polycristallins". Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10099/document.
Texto completoMost geomaterials are heterogeneous material at different scales. The macroscopic mechanical behavior of these materials depends directly on the mineralogical composition and microstructure as well as their evolution. The present study makes a simple trial to extend the most widely used polycrystalline model in metallography to a typical quasi-brittle geological material--granite. The standard yield criterion and plastic potential are modified to consider the main mechanical features of geomaterial, e.g. pressure sensitivity and plastic dilatancy. The full self-consistent model firstly proposed by Hill is adopted to relate the local fields and overall ones. And the macro response of polycrystal is determined by the classical homogenization process. The numerical implementation of local and macro stress update procedure are given and the possible difficulties encountered are pointed out. The identification of seven micromechanical parameters is briefly described. The validity of the developed model is checked through the comparisons between model's predictions and experimental data on both conventional and true triaxial compression tests, respectively
Picart, Philippe. "Contribution à la résolution numérique des problèmes élasto-plastiques et élasto-viscoplastiques en transformations finies". Valenciennes, 1986. https://ged.uphf.fr/nuxeo/site/esupversions/c0aa3577-2ebe-4da6-82da-563b9f60f2ea.
Texto completoNicaise, Nicolas. "Effets de longueur interne sur les propriétés effectives des polycristaux métalliques : applications aux aciers". Thesis, Metz, 2009. http://www.theses.fr/2009METZ045S/document.
Texto completoThe objective of this work is to study the effects of internal lengths, as the grain size on the mechanical behavior of IF steels with micromechanical models. After a literature review about different length scale effects observed in plasticity (grain size effects...) and existing scale transition methods, this work is divided into three steps. First of all, a self-consistent scheme written for heterogeneous elastic-viscoplastic materials is used to study the grain size dispersion effects on the mechanical behavior of polycrystalline aggregates, ignoring the heterogeneities of crystallographic orientations. These effects are as important as those due to the average grain size and crystallographic texture. In a second time, the same transition scale scheme is used to study the combined effects of grain size dispersion and crystallographic orientation. It appears that the effect of the grain size dispersion is larger than the effect of crystallographic texture on the tensile behavior. The third step is to develop new approaches with non-uniform plastic deformation inside the grain, in order to capture the effects of grain size through new interaction laws. Thus, two different models are proposed : a “discrete” one, considering dislocation distributions constrained by grain boundaries, and, an “averaged” one, accounting for plastic strain gradient in the region close to grain boundaries. These new approaches allow to reproduce the grain size effects observed on the mechanical behavior of metallic materials, in particular for IF steels
Rmili, Yosra. "ÉTUDE DE LA DILATANCE DE REYNOLDS DU BÉTON ET DE SON EFFET SUR LA FORMATION DE LA COUCHE DE LUBRIFICATION DANS LES TUYAUX DE POMPAGE". Electronic Thesis or Diss., CY Cergy Paris Université, 2024. http://www.theses.fr/2024CYUN1283.
Texto completoConcrete pumping process is important in the construction sector, facilitating the transport of fresh concrete to the casting site, even in difficult-to-access areas. This technique enables the achievement of considerable heights and distances. However, this process presents challenges. Therefore, accurately predicting the pumpability of concrete appears to be essential. Indeed, concrete pumpability relies on its rheological properties and its ability to form a lubrication layer (LL) during its flow through pipes. Accordingly, it is worthy to mention that mastering the rheology of concrete and understanding the characteristics of the LL is important, especially considering that the mechanisms of LL formation remain not well understood.This project focuses on investigating Reynolds dilatancy (RD), a potential mechanism involved in LL formation, and aims to highlight the key parameters governing it. The first part of the study introduces the development of a new method to assess shear-induced variations (RD) at free-surface flow. This method, although more reliable for conventional vibrated concrete (CVC), it does not fully explore this mechanism. Consequently, a new empirical device, the CRD-Test, was designed to evaluate the RD of self-compacting concrete (SCC) subjected to various scenarios under free-surface and pressurized conditions, simulating real casting and pumping processes. In this second part of the study, SCC is considered as a biphasic mixture of coarser particles (> 1.25 mm) in a fluid matrix of fine mortar (< 1.25 mm). Moreover, the new experimental device, named CRD-Test, offers wide range of shear and pressure levels. It is based on a modified coaxial cylinder tribometer, with a rotational speed ranging from 0 to 3 rps, and an air pressure regulator from 0 to 300 kPa. The RD phenomenon is manifested by fluctuations in lateral pressure measured at the outer cylinder of this apparatus and it was investigated through new indices.Experimental results reveal that RD values were found to be in good agreement with the workability and design parameters of the investigated concrete mixtures. Concrete with low fluidity values exhibited high RD indices under both free-surface and pressurized shear conditions. Furthermore, a biphasic approach highlights correlations between RD and the characteristics of aggregates with a diameter greater than 1.25 mm, as well as the viscoplastic characteristics of the fine mortar (i.e., the suspending phase). Moreover, RD results are mainly affected by the relative packing density of coarse aggregate during pumping process. Finally, Reynold values were in good agreement with flow regime characteristics, particle dynamics, and shear-induced particle migration indices. According to established correlations, dynamic segregation can significantly influence the mechanisms of LL formation during concrete pumping at low shear rates, illustrating the importance of Reynolds dilatancy in this process. However, at higher shear rates, dynamic segregation has been observed to negatively impact RD values, thereby increasing the risk of blockage during concrete pumping
Barick, Mohamed Cheikh. "Identification des propriétés viscoélastique-viscoplastique des matériaux par la nanoindentation instrumentée". Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCD004.
Texto completoInstrumented nanoindentation is a popular technique to extract the material properties from the measured load-displacement curves. However, the uniqueness and the intrinsic character of the estimated material parameters remain open issues, particularly when viscous phenomena are exhibited. In this thesis, a constitutive viscoelastic-viscoplastic (VEVP) behavior law is implemented in the finite element software ANSYS through a subroutine UMAT with a viscoelastic-plastic (VEP) particular case. The viscoelastic (VE) was treated using the behavior law available in ANSYS. The goal is to extract reliable and intrinsic properties by nanoindentation. In this context, series of nanoindentation experimental tests are carried out on the polypropylene (PP) in displacement-controlled mode using cube corner and Berkovich indenter tips. The Finite Element Model Updating (FEMU) shows that the identification of intrinsic VE properties of PP from single experimental nanoindentation test performed at 1000 nm/min is not possible. In order to quantify the richness of the information contained in the nanoindentation test, an identifiability index (I-index) based on the numerical conditioning of the inverse problem is used. The effect of nanoindentation depth rate, loading type (triangular, trapezoidal, exponential and sinusoidal) and apex angle is numerically investigated using this I-index in the VE case. We show a correlation between the identifiability results and the energy dissipated by the material. Several combinations of nanoindentation triangular tests and indenter tip angles are also investigated. We show that a dual nanoindentation method (cube corner and Berkovich) with triangular load-unload tests is an interesting combination to reliably extract all the VE parameters. The updating process using dual nanoindentation experimental tests conducted at 500 nm/min with cube corner and Berkovich indenter tips shows that under nanoindentation the PP is not only deformed in the VE domain.The investigation of the PP behavior is extended by including viscoplasticity in the behavior law. The updating process of the VEVP behavior law leads to multiple solutions for the values of the behavior parameters. The identifiability analysis carried out using this behavior shows that the identification of the material parameters from this dual nanoindentation data is impossible. We also carried out an updating process and identifiability analysis with the VEP behavior law. The obtained results show that the identification of the VEP parameters is difficult.These results pave the way for the design of a combination of nanoindentation tests based on this I-index to guarantee the uniqueness and the intrinsic character of the extracted properties
Joëssel, Louis. "Modélisation micromécanique du comportement viscoplastique d'un polycristal poreux : application à un acier inoxydable austénitique irradié". Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0402.
Texto completoAustenitic stainless steels employed as internals in pressurized water reactor vessels may nucleate intragranluar voids when exposed to prolonged irradiation and high temperature. The voids, almost spherical in shape, modify the mechanical behavior of the material. This work explores three different approaches in order to model viscoplasticity of voided single crystals. The first approach consists in idealizing the voided crystal as a hollow sphere assemblage made of crystalline material. The second approach consists in idealizing the voided crystal as a sequential laminate of infinite rank obeying an isotropic lamination sequence. The third approach consists in idealizing the voided crystal as a periodic medium with a complex unit cell, and computing the mechanical fields numerically via a Fast Fourier Transform algorithm. Then, the estimates for porous single crystals are used to model the viscoplasticity of voided polycrystals via a double up scaling process. Finally, in order to apply the present model to an irradiated austenitic stainless steel, the constitutive material parameters are identified with numerical simulations on periodic unit cells where locally the constitutive behavior is described by a phenomenological model especially devoted to this irradiated austenitic stainless steel, taking account of the evolution of irradiation defects. As a general rule, this work aims at delivering innovative, high-performance modeling tools, applicable to a wide variety of crystalline materials together with irradiated austenitic stainless steels