Submitted by Erika Demachki (erikademachki@gmail.com) on 2014-10-21T20:53:51Z No. of bitstreams: 5 Dissertação - Ana Larissa dal Piva Argenta - 2013 - Parte 01.pdf: 20230731 bytes, checksum: 56aa4f90641e87e6081a5e3e9319bd24 (MD5) Dissertação - Ana Larissa dal Piva Argenta - 2013 - Parte 02.pdf: 10802505 bytes, checksum: 4e34e2a114366cce38898dda48f31144 (MD5) Dissertação - Ana Larissa dal Piva Argenta - 2013 - Parte 03.pdf: 14680983 bytes, checksum: e7a40859c186d5c2130a3debfec64edd (MD5) Dissertação - Ana Larissa dal Piva Argenta - 2013 - Parte 04.pdf: 11913507 bytes, checksum: 73e7928267b0b902da703843e18b2919 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Jaqueline Silva (jtas29@gmail.com) on 2014-10-22T19:05:17Z (GMT) No. of bitstreams: 5 Dissertação - Ana Larissa dal Piva Argenta - 2013 - Parte 01.pdf: 20230731 bytes, checksum: 56aa4f90641e87e6081a5e3e9319bd24 (MD5) Dissertação - Ana Larissa dal Piva Argenta - 2013 - Parte 02.pdf: 10802505 bytes, checksum: 4e34e2a114366cce38898dda48f31144 (MD5) Dissertação - Ana Larissa dal Piva Argenta - 2013 - Parte 03.pdf: 14680983 bytes, checksum: e7a40859c186d5c2130a3debfec64edd (MD5) Dissertação - Ana Larissa dal Piva Argenta - 2013 - Parte 04.pdf: 11913507 bytes, checksum: 73e7928267b0b902da703843e18b2919 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-10-22T19:05:17Z (GMT). No. of bitstreams: 5 Dissertação - Ana Larissa dal Piva Argenta - 2013 - Parte 01.pdf: 20230731 bytes, checksum: 56aa4f90641e87e6081a5e3e9319bd24 (MD5) Dissertação - Ana Larissa dal Piva Argenta - 2013 - Parte 02.pdf: 10802505 bytes, checksum: 4e34e2a114366cce38898dda48f31144 (MD5) Dissertação - Ana Larissa dal Piva Argenta - 2013 - Parte 03.pdf: 14680983 bytes, checksum: e7a40859c186d5c2130a3debfec64edd (MD5) Dissertação - Ana Larissa dal Piva Argenta - 2013 - Parte 04.pdf: 11913507 bytes, checksum: 73e7928267b0b902da703843e18b2919 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2013-06-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Circular cylindrical shells are widely used structures in several engineering areas and have great capacity to withstand both axial and lateral loads. However, they may present a complex dynamic behavior. Thus, a detailed study of the behavior of cylindrical shells subjected to different loading and support conditions as well as the influence of material characteristics and geometric relations evaluation is justified. In this work the influence of geometry and orthotropy on the nonlinear dynamic behavior of orthotropic simply supported cylindrical shells subjected to both axial and lateral time depending loads is studied. To model the shell, the Donnell nonlinear shallow shell theory, neglecting the effects of shear deformations, is used. It is considered the shell in three different situations: empty, filled with static fluid and subjected to internal flow of incompressible and non-viscous fluid, whose motion is isentropic and irrotational. The radial displacements are described as an expansion with eight degrees of freedom which satisfies the boundary conditions. The Galerkin method is applied to obtain a set of nonlinear equations of motion, which are in turn solved by the Runge-Kutta method. A detailed analysis is performed to study the influence of material orthotropy and geometric relations such as length-radio (L/R) and radio-thickness (R/h) on the natural frequencies, critical loads, critical flow velocities, post-critical paths, frequency-amplitude relations, instability boundaries, bifurcation diagrams and resonance curves. Obtained results display the strong influence of both material orthotropy and geometric relations on the linear and nonlinear behavior of the shells and, depending on these characteristics, the shell can display softening or hardening behavior. / Cascas cilíndricas são estruturas com diversas aplicações em várias áreas da engenharia e têm grande capacidade para resistir a carregamentos axiais e a pressões laterais. Entretanto, são estruturas que podem apresentar um complexo comportamento dinâmico. Assim, um estudo detalhado do comportamento das cascas cilíndricas submetidas a diferentes condições de carregamento bem como a avaliação da influência do material e da geometria se justifica plenamente. Este trabalho tem como objetivo estudar a influência da ortotropia do material e da geometria no comportamento dinâmico não linear das cascas cilíndricas ortotrópicas simplesmente apoiadas e submetidas a carregamentos axiais e laterais variáveis com o tempo. Para modelar a casca é utilizada a teoria não linear de Donnell para cascas abatidas desprezando-se os efeitos das deformações cisalhantes. Considera-se a casca em três situações distintas: vazia, preenchida com fluido estático e submetida ao escoamento interno de fluido incompressível e não viscoso, cujo movimento é isentrópico e irrotacional. O deslocamento radial da casca é descrito, de maneira geral, por uma expansão com oito graus de liberdade que satisfaz as condições de contorno. O método de Galerkin é utilizado para obter o sistema discreto de equações diferencias não lineares de movimento, que são resolvidas através do método de Runge-Kutta de quarta ordem. Uma análise detalhada é realizada visando observar a influência das características do material e das relações geométricas comprimento-raio (L/R) e raio-espessura (R/h) nas frequências naturais, cargas críticas, velocidades críticas do fluido bem como nos caminhos pós-críticos, relações frequência-amplitude, fronteiras de instabilidade, diagramas de bifurcação e curvas de ressonância das cascas. Os resultados obtidos permitem observar a forte influência que a geometria e as propriedades dos materiais exercem no comportamento linear e não linear das cascas cilíndricas ortotrópicas e, dependendo de certas características, verifica-se que a casca pode ter comportamentos com ganho ou perda de rigidez.

In this work, we study the coupled dispersion characteristics of three distinct structural-acoustic waveguides, namely: -(1) a two-dimensional waveguide, (2) a fluid-filled circular cylindrical shell and (3)a fluid-filledelliptic cylindrical shell. Our primary interest is in finding coupled wavenumbers as functions of the fluid-structure coupling parameter(µ). Using the asymptotic solution methodology, we find the coupled wavenumbers as perturbations over the uncoupled wavenumbers of the component systems (the structure and the fluid). The asymptotic method provides us with analytical expressions of the coupled wavenumbers for small and large values of µ. The dispersion curves obtained from these extreme values of µ help in predicting the nature of the continuous transition of the wavenumber branches over the entire range of µ. Since the coupled wavenumbers are obtained as perturbations over the uncoupled wavenumbers, the perturbation term characterizes the effect of one medium over the other in terms of additional mass or stiffness. As is common in asymptotic methods, a particular form of the asymptotic expansion remains valid over a certain frequency range only. Hence, different scalings of the asymptotic parameter are used for different frequency ranges. In this regard, the method adopted uses principles of Matched Asymptotic Expansion (MAE). As mentioned above, we begin the study with a two-dimensional structural acoustic waveguide. Depending on the boundary condition at the top-edge of the fluid-layer (rigid or pressure-release), two cases are separately analyzed. In both these cases, only a single perturbation parameter (µ) is used. This is followed by the study of the axisymmetric mode vibration of a fluid-filled circular cylindrical shell. Here, in addition to , we include the Poisson’s ratio as another asymptotic parameter. The next problem studied is the beam mode (n =1)vibration of the same fluid-filled circular cylindrical shell. Here, the frequency is used as an asymptotic parameter (in addition to ) and the derivations proceed in two separate parts, one for the high frequency and the other for the low frequency. Having completed the n = 0 and n = 1 modes of the cylindrical shell, the higher order shell modes are studied using the simpler shallow shell theory. For the final system, viz., the elliptic cylindrical shell, another asymptotic parameter in the form of the eccentricity of the cross-section is used. Having derived the analytical expressions for the coupled wavenumbers and obtained the dispersion curves, a unified behavior of structural-acoustic systems is found to emerge. In all these systems, for small , the coupled wavenumbers are close to the in vacuo structural wavenumber and the wavenumbers of the rigid-walled acoustic duct. The measure of closeness is quantified by . As µ increases, these wavenumber branches get shifted continuously till for large µ, the coupled wavenumber branches are better identified as perturbations to the wavenumbers of the pressure-release acoustic duct. At the coincidence region, the coupled structural wavenumber branch transits to the coupled acoustic wavenumber branchand vice-versa. As a result, at coincidence frequencies, while the uncoupled wavenumber branches intersect, due to the coupling, there is no longer an intersection. These common characteristics are shared amongst all the systems despite the difference in geometries. This suggests that the above discussed features capture the essential physics of sound-structure coupling in waveguides.This workthus presents a novel unified view-point to the topic. Along the way, some additional novel studies are conducted which do contribute to the completeness of the work. The free wavenumbers determined from the asymptotic expressions are usedto calculate the forced response of the two-dimensional waveguide due to a δ forcing. Using this analysis, we are able to come up with a novel explanation of the observation that with coupling the dispersion curves cannot intersect. Additionally, the effect of bulk flow in the acoustic fluid is also comprehensively studied for the easier case of the two-dimensional waveguide. Further, the well-known universal dispersion relation for the higher order circumferential modes of the in vacuo circular cylindrical shell is re-derived using a simpler method.

The made-up software let to construct the cylindrical shell with composition in laminate by chosen test (reinforcement’s corner, number of shells), also it offer to simulate a reliability of construction and to optimise it by chosen in statistic parameters. Shell’s parameters can be evaluated like episodic variables, which are modulated with Monte - Carlo method. There is given opportunity to evaluate construction’s reliability: of the supposition that distribution of strain at shell is known, construction can be optimised when we are minimizing mass. If we want to show construction’s distribution of limitary state in dotted chart, we have to model strain’s value in every Monte – Carlo step. It is computed factors, which have influence for shell’s strain in construction’s stability. In such succession of operations is controlled the reliability of model’s evaluation. There are analysed parameters, which have the biggest influence for strain at shell. Studied the minimal shell’s mass fluctuation in dependence with dispersion and also parameter’s, of construction strain, overtop probability.

Submitted by Cláudia Bueno (claudiamoura18@gmail.com) on 2015-10-22T19:24:12Z No. of bitstreams: 2 Dissertação - Roger Otávio Pires Montes - 2015.pdf: 8169771 bytes, checksum: e580ffb280dfa5136f41ab38cf0aec4e (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-10-23T11:04:48Z (GMT) No. of bitstreams: 2 Dissertação - Roger Otávio Pires Montes - 2015.pdf: 8169771 bytes, checksum: e580ffb280dfa5136f41ab38cf0aec4e (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-10-23T11:04:48Z (GMT). No. of bitstreams: 2 Dissertação - Roger Otávio Pires Montes - 2015.pdf: 8169771 bytes, checksum: e580ffb280dfa5136f41ab38cf0aec4e (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-05-25 / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / This master’s thesis analyses the free and forced nonlinear vibrations of a simply supported functionally graded cylindrical shell which the material’s properties are described by gradient’s law along the shell’s thickness. The nonlinear equations of motion are obtained using nonlinear theories Donnell and Sanders, where the field displacements and field strain of nonlinear Donnell’s shallow shell theory is obtained as a simplification of the nonlinear Sanders’s formulation. The effects of the internal fluid, that is incompressible, irrotational and inviscid and it has been described as a potential velocity to consider the fluid-structure interaction, and the influence of a thermal field in the nonlinear dynamic behavior of the functionally graded cylindrical shell will be investigated. It is developed a low-dimensional model, wherein the shell of the system equilibrium equations is solved by an analytical procedure, which yields the longitudinal and circumferential displacement field as a function of transverse displacement, satisfying the boundary conditions problem. The determination of transverse displacement is obtained by the perturbation techiniques, which enables the achievement of the main nonlinear modes that should be present in the displacement fields of the functionally grade cylindrical shell. To analyze the nonlinear free vibration, it is applied the Galerkin-Urabe method to obtain the system of non-linear algebraic equations, and then resolved by the Newton-Raphson method. The results show the influence of functional gradation, geometry, the effect of the internal fluid, considering a fluid-filled shell, and the thermal action of the nonlinear free vibrations of the shell by the frequency-amplitude relations. Finally, a parametric analysis to study the nonlinear forced vibrations of the cylindrical shell subjected to a harmonic loading side for some geometric relations is conducted. In this case the system of ordinary differential equations of second order in time is obtained from the application of the Galerkin method and integrated over time from the Runge-Kutta fourth order method. The results evaluates the influence of the internal fluid and the thermal effects in the nonlinear oscillation of functionally graded cylindrical shell, using the resonances’ curves, the basins’ attraction, time responses and the phase portraits. / Nesta dissertação são analisadas as vibrações, livres e forçadas, não lineares de uma casca cilíndrica simplesmente apoiada feita com um material com gradação funcional, que as propriedades dos materiais constituintes são descritas por determinadas leis de gradação ao longo da espessura. As equações não lineares de movimento são obtidas utilizando-se as teorias não lineares de Donnell e de Sanders, sendo que os campos de deslocamentos e as deformações referentes à teoria não linear de Donnell para cascas abatidas podem ser obtidos como uma simplificação da formulação não linear de Sanders. Serão investigados os efeitos da presença de um fluido interno, incompressível, não viscoso e irrotacional, sendo descrito a partir de um potencial de velocidade, considerando a interação fluido-estrutura, além da influência de um campo térmico no comportamento dinâmico não linear da casca cilíndrica com gradação funcional. É desenvolvido um modelo de baixa dimensão, em que o sistema de equações de equilíbrio da casca é resolvido através de um procedimento analítico, o qual permite obter os campos de deslocamento axial e circunferencial em função dos deslocamentos transversais, além de atender as condições de contorno do problema. A determinação dos deslocamentos transversais é feita a partir do método da perturbação, o qual possibilita a obtenção dos principais modos não lineares que devem estar presentes nos campos de deslocamentos da casca cilíndrica. Para analisar as vibrações livres não lineares, aplica-se o método de Galerkin-Urabe para se obter o sistema de equações algébricas não lineares, sendo, em seguida, resolvido a partir do método de Newton-Raphson. Os resultados mostram a influência da gradação funcional, da geometria, do efeito do fluido interno, considerando uma casca totalmente preenchida, e da ação térmica nas vibrações livres não lineares da casca por meio das relações frequência-amplitude. Por fim, é feita uma análise paramétrica das vibrações forçadas não lineares da casca cilíndrica submetida a um carregamento lateral harmônico para algumas relações geométricas. Neste caso o sistema de equações diferenciais ordinárias de segunda ordem no tempo é obtido a partir da aplicação do método de Galerkin e integrado ao longo do tempo a partir do método de Runge-Kutta de quarta ordem. Da mesma forma avalia-se a influência do fluido interno e dos efeitos térmicos nas oscilações não lineares da casca cilíndrica com gradação funcional, utilizando-se as curvas de ressonância, as bacias de atração, as respostas no tempo e os planos fase.

De nombreuses structures spatiales telles que les lanceurs sont équipées d’une mousse de protection thermique. Cette couche de matériau extrêmement léger présente d’excellentes propriétés d’isolation thermique mais des caractéristiques mécaniques très faibles. Il est ici proposé d’analyser le comportement au flambage de ce type de construction où une fine et légère structure, coque cylindrique en aluminium avec un ratio R/t de 665, est recouverte par une épaisse couche de mousse de faible densité. Afin d'évaluer l'effet du comportement au flambage de ce type de coque multicouche, des essais expérimentaux et numériques sont réalisés sur des cylindres faiblement pressurisés soumis à du cisaillement et de la flexion. Ce cas de charge représente la configuration « cas sol », d’un lanceur sur le pas de tir, dans l’attente du lancement, et soumis à des charges mécaniques extrêmes générées par le vent. / Many space structures such as launchers are equipped with a thermal foam protection barrier. This layer, of extremely light material generally exhibits excellent properties of heat insulation but very weak mechanical characteristics. This study is devoted to the analysis of the buckling behavior of this hybrid wall construction where the skin of a very thin light-weight structure, an aluminum cylindrical shell with an R/t ratio of about 665, is coated with a thick layer of foam with a low material density. To gauge the effect on the buckling behavior of this kind of multilayered shells, experimental and numerical tests are conducted on slightly pressurized cylindrical shells submitted to shear load. This load configuration represents the case of a rocket on the launching pad, waiting to be launched, and submitted to mechanical loads induced by the wind.

Induced vibrations due to tire-pavement interaction are one of the main sources of vehicle exterior noise, especially near highways and main roads where traveling speeds are above 50 kph. Its dominant spectral content is approximately within 500-1500 Hz. However, accurate prediction tools within this frequency range are not available. Current methods rely on structural modeling of the complete tire using finite elements and modal expansion approaches that are accurate only at low frequencies. Therefore, alternative physically-based models need to be developed. This work proposes a new approach that incorporates wave behavior along the tire's circumferential direction, while modes are assumed along its transversal direction. The formulation for new infinite plate and cylindrical shell structural models of a tire is presented. These are capable of accounting for orthotropic material properties, different structural parameters between the belt and sidewalls, inflation pressure, and rotation of the tire. In addition, a new contact model between the pavement and the tire is developed presented. The excitation of the tire due to the impact of the tread-pattern blocks in the contact patch region is characterized and coupled to the structure of the tire. Finally, a Boundary Element Method is implemented in order to compute the vibration-induced noise produced by the tire. All the modeling components are combined in a single prediction tool named Wave Pro Tire. Lastly, simulated responses and validation cases are presented in terms of harmonic responses, Frequency Response Functions (FRF), and produced noise. / Doctor of Philosophy / Induced vibrations due to tire-pavement interaction are one of the main sources of vehicle exterior noise, especially near highways and main roads where traveling speeds are above 50 kph. Accurate prediction tools are not currently available. Therefore, new physically based models need to be developed. This work proposes a new approach to model the tire’s structure with a formulation that accounts for multiple physical phenomena. In addition, a model that simulates the contact between the pavement and the tire’s tread is presented. Finally, the vibrations are coupled to the produced noise in a single prediction tool named Wave Pro Tire. This work also includes simulated responses and validation cases.

Submitted by Cássia Santos (cassia.bcufg@gmail.com) on 2015-03-27T12:06:51Z No. of bitstreams: 2 Dissertação - Vitor Escher Martins - 2014.pdf: 13588446 bytes, checksum: 9cceb42b5d24095bc392dc37f17c9386 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-03-27T15:28:00Z (GMT) No. of bitstreams: 2 Dissertação - Vitor Escher Martins - 2014.pdf: 13588446 bytes, checksum: 9cceb42b5d24095bc392dc37f17c9386 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-03-27T15:28:00Z (GMT). No. of bitstreams: 2 Dissertação - Vitor Escher Martins - 2014.pdf: 13588446 bytes, checksum: 9cceb42b5d24095bc392dc37f17c9386 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2014-06-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Over the years, fiber-reinforced composite laminated shells have been widely used as structural components in several engineering areas and industrial applications. These structures can been subjected to extreme working conditions, either by a fluid structure interaction or even by both dynamic external load and thermal load that provides additional compressive stresses acting along the shell. In the present work, the nonlinear dynamic behavior and stability of fluid-filled laminated cylindrical shells under both thermal and lateral loads is investigated. To model the shell the nonlinear Amabili-Reddy Higher-Order Shear Deformation Theory is applied, the hydrodynamic pressure of the fluid is model by the potential flow theory and a linear temperature distribution is proposed along the thickness of the shells. Classical shells theories, which neglect shear deformation and rotary inertia, give inaccurate analysis results for moderately thick laminated shells. Due to this limitation, higher-order shear deformation theories can represent better the kinematics behavior and can yield more accurate interlaminar stress.To discretize the shell a 23 d.o.f. displacement field is used containing the axial, circumferential, lateral displacements, rotations as well as the coefficients to consider the shear effect. The Ritz method is applied in order to obtain a set of nonlinear ordinary differential equations of motions, which are in turn solved by the Runge-Kutta method. The obtained resonance curves and bifurcation diagrams show the great influence of both laminated material and the temperature on the nonlinear behavior of the shells. / Ao longo dos anos cascas cilíndricas laminadas reforçadas com fibras têm sido amplamente utilizadas como componentes estruturais em diversas áreas da engenharia e aplicações industriais. Durante sua vida operacional, essas estruturas são constantemente submetidas às extremas condições de trabalho, seja em função da interação fluido- estrutura, cargas externas dinâmicas ou mesmo por cargas térmicas que produzem tensões adicionais de compressão sobre a superfície da casca. Neste trabalho será investigado o comportamento dinâmico não linear de cascas cilíndricas laminadas com a presença de um meio fluido em repouso no interior da casca, além de se estudar a influência de esforços laterais dinâmicos solicitantes, juntamente com a variações de temperatura. A teoria de Amabili-Reddy de deformação por cisalhamento de ordem superior é utilizada para modelar o comportamento mecânico dos esforços e deformações da casca, garantindo assim, uma melhor distribuição das tensões interlaminares, ou seja, ao longo de sua direção radial. A análise é realizada para cascas simplesmente apoiadas, em que são consideradas três expansões de deslocamento, respectivamente nas direções longitudinal, circunferencial e radial, além de duas expansões para as rotações da linha neutra nos planos xz z, discretizando o problema em 23 graus de liberdade. O método de Ritz é aplicado para a obtenção do sistema de equações de movimento não linear (EDO), além do método de Runge-Kutta de 4º Ordem e o método de Força Bruta que são utilizados para se investigar o comportamento dinâmico das análises em questão.

Cette étude vise à analyser la coque qui est en contact avec un matériau qui la confine, et qu’elle subite une pression latérale externe. Les conditions de contact entre les deux corps, frottant ou pas, la rigidité du confinement ainsi que les conditions de chargement, la pression qui peut être directement appliquée à la coque comme elle peut être induite par le matériau de confinement qui par retrait ou retreint ou convergence radiale induit des contraintes, ceux sont là les paramètres qui nous paraissent essentiels à jauger pour la problématique du flambage avec contact d’une coque sous pression externe. Une campagne expérimentale où plusieurs configurations de confinement sont considérées. La nature du milieu extérieur associé au confinement et donc sa rigidité, le type de confinement, discret ou locale au bien total (surface entière de la coque), sont évalués. Une instrumentation adéquate, couplant des mesures ponctuelles et de champ nous a permis de correctement mettre en exergue la phénoménologie. Les simulations numériques par éléments finis à l’aide du code de calcul Abaqus/Standard 6.12-3 intègrent les différentes non linéarité mise en musique dans ce problème, les grands déplacements et rotations du fait du flambage, la non linéarité matériau. Ces travaux montrent que même pour un confinement externe avec une très faible rigidité de membrane, comme pour le sable ou le polystyrène expansé, un gain important de capacité portante est observé, le flambage est retardé. L’augmentation est substantielle dans le cas d’un confinement total, non négligeable et consistante dans le cas d’un confinement local. Nous avons aussi constaté que la charge de flambage et le mode associé dépendent de la configuration de contact, notamment de la rigidité à la flexion du confinement. / Motivated by practical engineering applications, thin-walled cylindrical shells are widely used as structural elements. Because of their low flexural strength, these structures are very sensitive to buckling when exposed to external pressur. Conventional stiffening which makes it possible to improve the bearing capacity is to add stiffening rings connected by axial stiffeners or axial stiffeners. In these configurations the stiffening elements are an integral part of the structure with a continuity of material. One can ask the question of the effect of contiguous but non-continuous adjacent external structures ensuring total or local surface external contact. These are real configurations, such as those of buried pipelines, pipelines, or the case of insulated structures. This study aims to analyze these cases where the shell is in contact with a material which confines it, and that it undergoes an external lateral pressure. The contact conditions between the two bodies, whether rubbing or not, the stiffness of the confinement as well as the loading conditions, the pressure which can be directly applied to the shell as it may be induced by the confinement material which by withdrawal or shrinkage or Radial convergence induces stresses, these are the parameters that we consider essential for gauging the problem of buckling with contact of an external pressure shell. To answer these questions, we conducted an experimental campaign where several configurations of confinement are considered. The nature of the external environment associated with the confinement and therefore its rigidity, the type of confinement, discrete local or the total property (entire surface of the shell), are evaluated. Appropriate instrumentation, coupling point and field measurements, has allowed us to correctly highlight the phenomenology. Numerical modeling is also carried out using finite element method by Abaqus/Standard 6.12-3 code. Numerical simulations integrate the different nonlinearities in this problem, large displacements and rotations due to buckling, nonlinearity material, in some cases the buckling is plastic, but also the nonlinearity induced by an evolutionary contact. The modeling is carried out in 2D and 3D mesh, and in the latter case either by means of shell elements or by massive elements, the first aim being to corroborate the experimental observations more or less precisely. This work shows that even for external confinement with very low membrane rigidity, as for sand or expanded polystyrene, a significant gain in bearing capacity is observed, the buckling is delayed. The increase is substantial in the case of a total confinement which is not negligible and consistent in the case of local confinement. We have also found that the buckling load and the associated mode depend on the contact configuration, in particular the flexural rigidity of the confinement.

Diploma thesis is fucused on strength calculation of the heat exchanger according to ČSN EN 13 445. Introductory part introduce problems with the design of heat exchangers. In other parts there are a strength calculation of the heat exchanger according to ČSN EN 13 445, the results of the analysis with their appreciation. Annexes included output logs from the program Sant 'Ambrogio, and drawings documentation.

The thesis contains information about the design of pressure vessels and describes their individual parts. It is mentioned production of individual parts and the process including assembly parts in one unit. The thesis includes options of control and testing of pressure vessels. It is described kinds of built-ins of distillation column and the basic principles and types of distillation. It is created stress analysis of pressure vessels parts according to ČSN EN 13 445 – 3, and also stress analysis of the selected part of column by using FEM. Mechanical drawing of distillation column is part of the thesis.