This master's thesis deals with stress analysis and optimalization frame of the self- loading package transporter. It consists the analysis of original frame, the proposed changes and analysis of new frame.

This master’s thesis deals with VUT 081 Kondor composite fuselage design and control system layout design. Load computation and selection of critical load cases are made. Principal inner surfaces of the fuselage are designed with respect to basic ergonomic requirements of the crew. Construction materials are chosen and a layup of composite materials is performed. Fuselage FEM model is made in MSC Patran/Nastran system and the structure-strength analysis is given for chosen load cases.

This Master´s thesis describes the design of composite horizontal tail of VUT 100 aircraft. Load calculation and selection of the critical load cases is performed. Internal structure of stabilizer and right elevator is designed. Construction materials are chosen and the structure of the composite materials is proposed. FEM models of stabilizer and the right elevator are created in MSC Patran system and consequently the strength test of the models for the selected load cases is executed using MSC Nastran software and COMPOST.

The presented Master Thesis is focused on the structural analysis of the proximal femur on which the Proximal Femoral Nail (PFN) and Proximal Femoral Tele-Screw (PFT) systems are applied. These systems are used for a treatment of the intertrochanteric and femoral neck fractures. However, in some cases a loss of stability of the systems may be expected. The presented thesis describes a development of numerical models in which stress distribution of implants and strain distribution of bone tissue are compared. Numerical models were created from real objects. The model of femur geometry was created by using the Computed Tomography (CT). Boundary conditions of the model were estimated from the force equilibrium of the lower limb. All numerical models were processed in the commercial package ANSYS Workbench v15.0. It is shown that the hip screws of the PFN system result in lower equivalent stresses than the screws of the PFT system. Maximal strains of the bone tissue, when using the PFN system, are situated near the fracture, close the hip screw thread. For the PFT system, the maximal strains are only near the area of fracture.

Cette thèse a pour but le développement d'un modèle constitutif hydromécanique prenant en compte le couplage de l'endommagement et de la plasticité dans les géomatériaux non-saturés. Le couplage de ce modèle avec les transferts hydrauliques est rendu possible par son implémentation dans le code aux éléments finis $Theta$-Stock. Un algorithme local a été développé spécifiquement dans ce but. Des problèmes hydromécaniques complètement couplés, tels que la création de la zone endommagée par excavation autour d'un tunnel ou la création d'un endommagement de dessiccation et d'humidification ont été simulés. Une contrainte doublement effective incorporant les effets de la succion et de l'endommagement (considéré isotrope) a été définie en s'appuyant sur des bases thermodynamiques. Cette approche a l'avantage de considérer une unique variable de contrainte étant thermodynamiquement conjuguée aux déformations élastiques. Une formulation hyperélastique dépendante de la pression de confinement est utilisée pour décrire le comportement dans le domaine élastique. L'évolution des rigidités élastiques avec l'endommagement est comparée en considérant deux hypothèses : le principe des déformations équivalentes et le principe de l'énergie élastique équivalente. L'hypothèse d'équivalence des déformations permet d'introduire la contrainte doublement effective dans les équations de plasticité et ainsi de coupler plasticité et endommagement. Les équations de plasticité sont dérivées du modèle de Barcelone (Alonso extit{et al.}, 1990), lui même basé sur le modèle de Cam-Clay. Deux critères distincts d'endommagement et de plasticité sont définis qui peuvent être activés aussi bien indépendamment que simultanément. Les surfaces de charges étant exprimées en fonction de la contrainte effective et de la succion, elles évoluent automatiquement en fonction de la succion et de l'endommagement dans l'espace des contraintes totales. Cela permet de représenter la transition d'un comportement ductile vers un comportement fragile lorsque le matériau est asséché. Un algorithme local explicite a été développé pour gérer le couplage des deux phénomènes dissipatifs. L'implémentation du modèle constitutif dans le code aux éléments finis $Theta$-Stock permet l'étude de problèmes hydromécaniques complètement couplés, les lois de transfert dépendant elles aussi de l'état de saturation du matériau. Ce modèle a d'abord été appliqué à la simulation du développement de micro-fissures lors du séchage d'une éprouvette. L'apparition de l'endommagement est expliquée principalement par le gradient de pression très important créé à la surface de l'échantillon lorsqu'on applique une forte variation de succion. Enfin, un problème à échelle réelle est simulé. L'excavation d'un tunnel, la désaturation du sol environnant dû à la ventilation, ainsi que la création de la zone endommagée par excavation sont étudiés. L'étendue des zones l'endommagement et de déformations plastiques autour du tunnel est étudiée / This thesis work objective is the development of a hydro-mechanical constitutive model which accounts for damage-plasticity couplings in unsaturated geomaterials. The coupling of this model with hydraulic transfers is made possible by its implementation into the Finite Element code Theta-Stock. In order to achieve this implementation, a specific stress-point algorithm has been developed. Fully coupled hydro-mechanical problems have been simulated, such as the creation of the Excavation Damaged Zone around a tunnel and the initiation of damage due to desiccation and humidification. A double effective stress incorporating both the effect of suction and damage (assumed isotropic) is defined based on thermodynamical considerations. The advantage of this approach is that it results in a unique stress variable being thermodynamically conjugated to elastic strains. A pressure-dependent hyperelastic formulation is used to describe the behaviour inside the elastic domain. The evolution of elastic rigidities with damage is then studied. Two hypotheses are compared, the principle of strain equivalence and the principle of equivalent energy. Coupling between damage and plasticity phenomena is achieved by following the principle of strain equivalence and incorporating the effective stress into plasticity equations. The plasticity framework is based on the Barcelona Basic Model (Alonso extit{et al.}, 1990), itself based on the Cam-Clay model. Two distinct criteria are defined for damage and plasticity, which can be activated either independently or simultaneously. Their formulation in terms of effective stress and suction allows them to evolve in the total stress space with suction and damage changes. This leads to a direct coupling between damage and plasticity and allows the model to capture the ductile/brittle behaviour transition occurring when clays are drying. A specific explicit algorithm has been developed to handle the association of the two dissipative phenomena. The implementation of the constitutive model into the Finite Element code Theta-Stock allowed for the simulation of fully coupled hydro-mechanical problems. The hydraulic transfer laws also consider the saturation state. This fully coupled model is first applied to simulate the development of micro-cracks during desiccation of a soil sample. Damage initiation is explained mainly by the important pressure gradient appearing at the boundary when applying a high suction change. Finally, a full-scale problem is simulated. The excavation of a tunnel, the desaturation of the surrounding soil and the creation of the excavation damaged zone are studied

In order to prepare modern finite element analysis a program for the efficient parallel generation of tetrahedral meshes in a wide class of three dimensional domains having a generalized cylindric shape is presented. The applied mesh generation strategy is based on the decomposition of some 2D-reference domain into single con- nected subdomains by means of its triangulations the tetrahedral layers are built up in parallel. Adaptive grid controlling as well as nodal renumbering algorithms are involved. In the paper several examples are incorporated to demonstrate both program's capabilities and the handling with.

Some boundary value problems yield anisotropic solutions, e.g. solutions with boundary layers. If such problems are to be solved with the finite element method (FEM), anisotropically refined meshes can be advantageous. In order to construct these meshes or to control the error one aims at reliable error estimators. For \emph{isotropic} meshes many estimators are known, but they either fail when used on \emph{anisotropic} meshes, or they were not applied yet. For rectangular (or cuboidal) anisotropic meshes a modified error estimator had already been found. We are investigating error estimators on anisotropic tetrahedral or triangular meshes because such grids offer greater geometrical flexibility. For the Poisson equation a residual error estimator, a local Dirichlet problem error estimator, and an $L_2$ error estimator are derived, respectively. Additionally a residual error estimator is presented for a singularly perturbed reaction diffusion equation. It is important that the anisotropic mesh corresponds to the anisotropic solution. Provided that a certain condition is satisfied, we have proven that all estimators bound the error reliably.

The permeability of rocks has a critical influence on their fluid transport response in critical geo-environmental applications, such as pollutant transport or underground storage of hazardous nuclear waste. In such processes, the materials microstructure may be altered as a result of various stimuli, thereby impacting the fluid transfer properties. Stress or strain state modifications are one of the main causes for such evolutions. To numerically address this concern, an integrated and automated numerical tool was developed and illustrated on subsets of microCT scans of a Vosges sandstone (i) to explore the links between the pore space properties and the corresponding macroscopic transfer properties, with (ii) an incorporation of the microstructural alterations associated with stress state variations by using a realistic image-based representation of the microstructural morphology. The ductile mechanical deformation behavior under high confining pressures at the scale of the microstructure, inducing pore closures by local plastifications, was modelled using finite elements simulations with a non-linear elastoplastic law, allowing to take into account the redistribution of local stresses. These simulations require robust discretization tools to capture the complex geometry of the porous network and the corresponding solid boundaries of the heterogeneous microstructural geometries. To achieve this, an integrated approach for the conformal discretization of complex implicit geometries based on signed distance fields was developed, producing high quality meshes from both imaging techniques and computational RVE generation methodologies. This conforming discretization approach was compared with an incompatible mode-based framework using a non conforming approach. This comparison highlighted the complementarity of both methods, the former capturing the effect of more detailed geometrical features, while the latter is more flexible as it allows using the same (non conforming) mesh for potentially variable geometries.The evolution of permeability was evaluated at different confining pressure levels using the Lattice-Bolzmann method. This uncoupled solid-fluid interaction made it possible to study the combined influence on the permeability, porosity and the pores size distribution of the pore space morphology and the solid skeleton constitutive law parameters during loading and unloading conditions. The results highlight the need to consider elastoplastic laws and heterogeneities in the rock model to simulate the ductile behavior of rocks at high confining pressures leading to significant permeability alterations under loading, and irreversible alterations under loading/unloading cycles induced by progressive pore closures.The proposed methodology is designed to be flexible thanks to the interfacing with 'classical' discretization approaches and can be easily readapted to other contexts given the block approach. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

Cette thèse est consacrée à l'étude des équations du Darcy Brinkman Forchheimer (DBF) avec des conditions aux limites non standards. Nous montrons d'abord l'existence de différents type de solutions (faible, forte) correspondant au problème DBF stationnaire dans un domaine simplement connexe avec des conditions portants sur la composante normale du champ de vitesse et la composante tangentielle du tourbillon. Ensuite, nous considérons le système Brinkman Forchheimer (BF) avec des conditions sur la pression dans un domaine non simplement connexe. Nous prouvons que ce problème est bien posé ainsi que l'existence de la solution forte. Nous établissons la régularité de la solution dans les espaces L^p pour p >= 2.L'étude et l'approximation du problème DBF non stationnaire est basée sur une approche pseudo-compressibilité. Une estimation d'erreur d'ordre deux est établie dans le cas o\`u les conditions aux limites sont de types Dirichlet ou Navier.Enfin, une méthode d'éléments finis Galerkin Discontinue est proposée et la convergence établie concernant le problème DBF linéarisé et le système DBF non linéaire avec des conditions aux limites non standard. / This thesis is devoted to Darcy Brinkman Forchheimer (DBF) equations with a non standard boundary conditions. We prove first the existence of different type of solutions (weak, strong) of the stationary DBF problem in a simply connected domain with boundary conditions on the normal component of the velocity field and the tangential component of the vorticity. Next, we consider Brinkman Forchheimer (BF) system with boundary conditions on the pressure in a non simply connected domain. We prove the well-posedness and the existence of a strong solution of this problem. We establish the regularity of the solution in the L^p spaces, for p >= 2.The approximation of the non stationary DBF problem is based on the pseudo-compressibility approach. The second order's error estimate is established in the case where the boundary conditions are of type Dirichlet or Navier. Finally, the finite elements Galerkin Discontinuous method is proposed and the convergence is settled concerning the linearized DBF problem and the non linear DBF system with a non standard boundary conditions.

Ce travail porte sur le couplage des déformations d'une bulle avec son sillage et sa trajectoire dans plusieurs configurations. Un formalisme de type eulérien-lagrangien permet d'écrire le problème sur un domaine mouvant faiblement déformé par rapport à la configuration de référence. Grâce à cette approche, il est possible d'étudier dans un cadre linéaire le couplage entre les déformations d'une bulle et les effets hydrodynamiques. En appliquant ce formalisme, on peut dans un premier temps calculer l'écoulement de base autour de la bulle et sa géométrie d'équilibre, et dans un second temps développer une approche de stabilité globale prédisant les seuils d'instabilité et les propriétés des modes d'oscillation. Afin de développer cette méthode, des résultats sur les oscillations linéaires de bulles et de gouttes dans un fluide au repos et sans influence de la gravité sont tout d'abord présentés et comparés à des résultats théoriques existants. Puis, le principe du formalisme eulérien-lagrangien est illustré en prenant pour problème modèle l'équation de la chaleur formulée sur un domaine arbitrairement déformé. Ce principe est ensuite appliqué aux équations de Navier-Stokes, aboutissant à une version linéarisée autour d'un domaine de référence incluant de manière complète les couplages entre déformations de la géométrie et perturbations de l'écoulement. On met en oeuvre sur le système obtenu une méthode itérative de Newton donnant accès à l'état de base, c'est-à-dire à l'écoulement stationnaire autour de la bulle et à sa forme d'équilibre. Ce même système permet par la suite d'effectuer une analyse de stabilité globale de l'écoulement autour d'une bulle qui se déforme. L'algorithme développé est d'abord appliqué au cas d'une bulle piégée dans un écoulement d'étirement, permettant de décrire des formes d'équilibre dans des régimes stables et instables. Le cas de la bulle en ascension dans un fluide pur est ensuite abordé. Une étude paramétrique est conduite, couvrant une vaste gamme de liquides allant de l'eau pure à des huiles de silicone très visqueuses. Les états de base calculés par la méthode de Newton ainsi que les seuils d'instabilité des sillages sont en bon accord avec les résultats expérimentaux. Dans les cas des liquides très peu visqueux, notre approche décrit de manière plus précise les effets visqueux dans les couches limites et donne des résultats plus satisfaisants que les approches numériques existantes. Elle confirme par ailleurs que la déformation de la bulle joue un rôle mineur dans ces gammes de paramètres. Pour les liquides plus visqueux en revanche, on observe un couplage plus fort entre déformation et sillage. / This works deals with the coupling between time-dependent deformation, wake dynamics and path characteristics of a gas bubble in different configurations. An Eulerian-Lagrangian formalism is sought to formulate this problem in a moving domain having a small deformation compared to the reference configuration. This approach allows us to study the linear coupling between bubble deformations and hydrodynamic effects. This formalism makes it possible to first compute the base flow around a bubble and the corresponding steady shape, then to develop a global stability approach aimed at predicting the threshold of path instability and the properties of bubble oscillation modes. To develop this method, we first compute the linear oscillations of bubbles and drops in a quiescent fluid without gravity and compare them to existing theory. Then, the premise of the Eulerian-Lagrangian formalism is illustrated using a model equation, namely the heat equation written in an arbitrarily deformed domain. The same formalism is applied to the NavierStokes equations, yielding a linearized version of these equations in the neighbourhood of a reference domain, including the two-way coupling between shape deformations and perturbations of the base flow. With this system of equations at hand, we implement a Newton method that provides the steady state, i.e. the base flow around the bubble and its geometry. The same system allows us to carry out a global stability analysis of the flow past a deformable bubble. We first consider the situation where the bubble is trapped in a straining flow, for which we compute stable and unstable equilibrium shapes. We finally tackle the case of a buoyancy-driven bubble rising in a pure liquid. A parametric study is carried out over a wide range of liquids, from pure water to high-viscosity silicon oils. Steady states computed with the Newton method and instability thresholds are found to be in good agreement with experimental observations. For low-viscosity fluids, our approach captures the viscous effects that take place in the boundary layer better than existing computational approaches, yielding predictions for the onset of path instability in better agreemnt with observations. Furthermore, it confirms that time-dependent bubble deformations play a minor part for such liquids. In contrast, a stronger coupling between shape and path instabilities is observed in high-viscosity fluids