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Large Deformation Analysis Of Flexible Multibody SystemsTuzun, Aydin 01 September 2012 (has links) (PDF)
Large displacement and large strain problems of mechanical systems can be solved mainly by four methods. These are Floating Frame of Reference, Incremental Finite Element, Large Rotation Vector and Absolute Nodal Coordinate Formulations (ANCF). Due to exact rigid body representation, simple mass matrix structure and non-incremental formulation, ANCF is more convenient in analyzing flexible multibody systems. However, it is limited to problems with regular boundaries, currently.
The aim of the thesis is to improve the current ANCF in order to handle various problems with irregular boundaries. For this purpose, firstly meshfree ANCF has been developed to analyze flexible multibody systems. Verification of the developed meshfree formulation has been performed for beam type structures and accurate results have been obtained. Then, &ldquo / ANCF with Virtual Element Mapping Method&rdquo / has been proposed to overcome the boundary problems of the current formulations. The proposed method has been implemented to plane stress, plane strain, plate/shell and 3D solid finite elements. Verification of the proposed method has been performed by using the patch test problems available in the literature. Besides, it has been verified by various flexible multibody problems with large deformations. Additionally, shape function polynomials for thin plate assumption have been derived.
It is observed that developed formulations and methods can be useful not only for flexible multibody systems but also for structural mechanics problems subjected to large deformations and/or rotations. The proposed methods and formulations are more efficient than the current formulations in the literature due to extended shape limits of finite elements.
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On the Experimental Determination of Damping of Metals and Calculation of Thermal Stresses in Solidifying ShellsÅberg, Jonas January 2006 (has links)
This thesis explores experimentally and theoretically two different aspects of the properties and behaviour of metals: their ability to damp noise and their susceptibility to crack when solidifying. The first part concerns intrinsic material damping, and is motivated by increased demands from society for reductions in noise emissions. It is a material’s inherent ability to reduce its vibration level, and hence noise emission, and transform its kinetic energy into a temperature increase. To design new materials with increased intrinsic material damping, we need to be able to measure it. In this thesis, different methods for measurement of the intrinsic damping have been considered: one using Fourier analysis has been experimentally evaluated, and another using a specimen in uniaxial tension to measure the phase-lag between stress and strain has been improved. Finally, after discarding these methods, a new method has been developed. The new method measures the damping properties during compression using differential calorimetry. A specimen is subjected to a cyclic uniaxial stress to give a prescribed energy input. The difference in temperature between a specimen under stress and a non-stressed reference sample is measured. The experiments are performed in an insulated vacuum container to reduce convective losses. The rate of temperature change, together with the energy input, is used as a measure of the intrinsic material damping in the specimen. The results show a difference in intrinsic material damping, and the way in which it is influenced by the internal structure is discussed. The second part of the thesis examines hot cracks in solidifying shells. Most metals have a brittle region starting in the two-phase temperature range during solidification and for some alloys this region extends as far as hundreds of degrees below the solidus temperature. To calculate the risk of hot cracking, one needs, besides knowledge of the solidifying material’s ability to withstand stress, knowledge of the casting process to be able to calculate the thermal history of the solidification, and from this calculate the stress. In this work, experimental methods to measure and evaluate the energy transfer from the solidifying melt have been developed. The evaluated data has been used as a boundary condition to numerically calculate the solidification process and the evolving stress in the solidifying shell. A solidification model has been implemented using a fixed-domain methodology in a commercial finite element code, Comsol Multiphysics. A new solidification model using an arbitrary Lagrange Eulerian (ALE) formulation has also been implemented to solve the solidification problem for pure metals. This new model explicitly tracks the movement of the liquid/solid interface and is much more effective than the first model. / QC 20100929
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Pretreatment Of Peanut Shells For Co-production Of Glucose And Concrete AdmixtureTatli, Emre 01 February 2013 (has links) (PDF)
This thesis work aims the ionic liquid pretreatment of peanut shells for co-production of
glucose as fermentable sugar and lignin, considering a multi product perspective. The
effects of ionic liquid type and pretreatment time period on the sugar and lignin yields
were investigated, as the particle size and temperature parameters were determined in the
preliminary studies. Peanut shells were pretreated at constant temperature, 150 oC, for 5,
15 and 30 minutes with 1-ethyl-3-methylimidazolium acetate and for 15, 30 and 60
minutes with 1-ethyl-3-methylimidazolium chloride. The pretreated peanut shells were
then subjected to enzymatic hydrolysis in order to produce fermentable sugars, mostly,
glucose. The solid residue obtained upon enzymatic hydrolysis was analyzed in terms of
lignin quantity. 1-ethyl-3-methylimidazolium acetate pretreatment for 15 minutes resulted
in the maximum reducing sugar and lignin yields / 28 g of reducing sugar and 20 g of solid
residue with 70% lignin were obtained per 100 g of peanut shells. Higher pretreatment
time resulted in lower yields. Moreover, no optimal time period for 1-ethyl-3-
methylimidazolium chloride pretreatment was obtained, since reducing sugar and lignin
yields increased as the time period increased. Also all reducing sugar and lignin yields
were lower than that obtained with 1-ethyl-3-methylimidazolium acetate. Lignin obtained
upon enzymatic hydrolysis of 1-ethyl-3-methylimidazolium acetate pretreated peanut
shells were characterized by SEM, FTIR, TGA and XRD analyses, which also showed the
morphological and structural effects of pretreatment and enzymatic hydrolysis on peanut
shells / and used as concrete admixture, which increased the flow of the concrete by 6%.
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Compliant shell mechanismsSeereeram, Videsh Ramjas January 2012 (has links)
No description available.
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Computational and analytical modelling of composite structures based on exact and higher order theories.Tabakov, Pavel. January 1995 (has links)
The objective of the present study is the computational and analytical modelling of
a stress and strain state of the composite laminated structures.
The exact three dimensional solution is derived for laminated anisotropic thick cylinders
with both constant and variable material properties through the thickness of a
layer. The governing differential equations are derived in a such form that to satisfy
the stress functions and are given for layered cylindrical shell with open ends. The
solution then extended to the laminated cylindrical shells with closed ends, that is
to pressure vessels.
Based on the accurate three-dimensional stress analysis an approach for the optimal
design of the thick pressure vessels is formulated. Cylindrical pressure vessels are
optimised taking the fibre angle as a design variable to maximise the burst pressure.
The effect of the axial force on the optimal design is investigated. Numerical results
are given for both single and laminated (up to five layers) cylindrical shells. The
maximum burst pressure is computed using the three-dimensional interactive Tsai-:
Wu failure criterion, which takes into account the influence of all stress components
to the failure. Design optimisation of multilayered composite pressure vessels are
based on the use of robust multidimensional methods which give fast convergence.
Transverse shear and normal deformation higher-order theory for the solution of dynamic
problems of laminated plates and shells is studied. The theory developed is
based on the kinematic hypotheses which are derived using iterative technique. Dynamic
effects, such as forces of inertia and the direct influence of external loading on
the stress and strain components are included at the initial stage of derivation where
kinematic hypotheses are formulated. The proposed theory and solution methods
provide a basis for theoretical and applied studies in the field of dynamics and statics
of the laminated shells, plates and their systems, particularly for investigation of
dynamic processes related to the highest vibration forms and wave propagation, for
optimal design etc.
Geometrically nonlinear higher-order theory of laminated plates and shells with
shear and normal deformation is derived. The theory takes into account both transverse
shear and normal deformations. The number of numerical results are obtained
based on the nonlinear theory developed. The results illustrate importance of the
influence of geometrical nonlinearity, especially, at high levels of loading and in case
when the laminae exhibit significant differences in their elastic properties. / Thesis (Ph.D.)-University of Natal, Durban, 1995.
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Δημιουργία ευφυούς συστήματος διάγνωσης παθήσεων του προστάτηΤσιμάρα, Μαρία 03 May 2010 (has links)
Σκοπός της παρούσας εργασίας ήταν η δημιουργία ενός ευφυούς συστήματος για τη διάγνωση νοσημάτων του προστάτη αδένα με βάση σημεία και συμπτώματα που διαπιστώνονται σε έναν ασθενή όπως καταγράφονται κατά την κλινική του εξέταση.
Τα βασικά σημεία της εργασίας είναι τα εξής: αρχικά παράγεται το μοντέλο της διαγνωστικής στρατηγικής που ακολουθείται για τη διάγνωση των συγκεκριμένων παθήσεων και στη συνέχεια γίνεται εκμαίευση της διαγνωστικής γνώσης από ειδικούς ή/και από εμπειρικά δεδομένα. Η διαδικασία και η γνώση αναπαρίστανται με χρήση υβριδικών μεθόδων αναπαράστασης και με τη χρήση ασάφειας ή/και αβεβαιότητας, η οποία είναι εγγενής σε τέτοια διαγνωστικά συστήματα.
Το σύστημα αναπτύχθηκε με τέτοια εργαλεία που δίνουν την δυνατότητα στέγασής του σε ιστότοπο ώστε να χρησιμοποιηθεί ως ειδικός συμβουλευτικός οδηγός από ενδιαφερομένους μη ειδικούς ιατρούς & από ασθενείς καθώς και από φοιτητές υγειονομικών σχολών για εκπαιδευτική χρήση. Το σύστημα περιέχει γνώση εμπειρογνωμόνων σε συνδυασμό με στοιχεία πλούσιας βιβλιογραφικής αναζήτησης και μελέτης. Τέλος πραγματοποιήθηκε επικύρωση των αποτελεσμάτων μέσα από μια τυχαιοποιημένη κλινική έρευνα.
Η υλοποίηση του συστήματος μας στηρίζεται σε ένα ειδικό κέλυφος δημιουργίας ευφυών συστημάτων και σε εργαλεία μεθόδων μηχανικής μάθησης. Επίσης, υλοποιούνται δύο εκδοχές (Hirofilos Ι & ΙΙ) και γίνεται σύγκριση των απο-τελεσμάτων. Αναγνωρίστηκε η σαφής υπεροχή του Hirofilos ΙΙ που αναπτυχθηκε με σύστημα μηχανικής εκμάθησης και με δυνατότητα διαχρονικής αναβάθμισης. / During making this project our concern was the creation of a new expert system for diagnosis prostate disease depending on the clinical status of a patient as these are identified during medical examination. The main points were as follows: First has been constructed a diagnosis process model which was followed by the diagnosis for the most common prostate diseases. Secondly was implemented extracting of the medical knowledge based on specialists or/and experimental data. The whole process and the medical Knowledge will be developed using hybrid methods of representation and having the partcipation of such saying fuzziness or inaccuracy, that is innate in that kind of intelligent decision-support. The new intelligent system is already accommodated on a hospital server and is used as a decision-support system, as well as an e-learning platform for medical students. For the implementation of the new system have been used an expert system shell and knowledge engineering tools.
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'n Museologiese ondersoek na die mens se benutting van die mollusk (skulp en skulpdier) in geselekteerde kunsvorme, vir die doel van die ontwerp van 'n uitstallingConradie-Faul, Jacqueline 03 1900 (has links)
Thesis (MA)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The aim of this study is to investigate man's use of the mollusk within selected art forms,
and to use the research results to design a contemporary museum exhibition, relevant
within a South African context.
Two sections are presented. In section A the selected art forms, fine arts, architecture,
furniture design, masks and music and other sound instruments are thoroughly investigated
to determine in what way the mollusk/shell is used in or on these art forms. A large
number of figures are included to illustrate the available examples, and to aid the reader in
the visualization of these applications.
In section B a design solution is presented, based on the research results of section A. The
compilation of an exhibition team and the whole design process, from the choice of an
exhibition theme to the evaluation of the exhibition, is investigated. The exhibition
designer plays the important role of interpreting the research results and to compile a
design solution.
A wide variety of exhibition techniques are recommended for the design solution,
including theatre productions, special lighting and sound effects, demonstrations and tours.
A number of figures are included, where photos taken during the museum visitations and
design sketches provide further insight into the design solution.
From the research results it was noted that an educational subject such as the mollusk/shell,
can be made timely and attractive for the museum visitor by the use of creative,
contemporary and relative exhibition techniques. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie is om die mens se benutting van die mollusk in geselekteerde
kunsvorme te ondersoek en om die navorsingsresultate te gebruik om 'n eietydse en
kreatiewe museumuitstalling, relevant binne die Suid-Afrikaanse konteks, te ontwerp.
Twee afdelings word aangebied. In afdeling A word die geselekteerde kunsvorme,
beeldende kunste, argitektuur, meubeIkuns, maskers en musiek- en ander kIankinstrumente
deeglik ondersoek om vas te stel op watter wyse die mollusk/skulp daarin of daarop
gebruik word. 'n Groot aantal figure word ingesluit om die beskikbare voorbeelde te
illustreer en op so 'n wyse visuaIisasie vir die leser te vergemaklik.
In afdeling B word 'n ontwerpoplossing aangebied, gebaseer op die navorsingsresultate
van afdeling A Die samestelling van 'n uitstalspan en die hele ontwerpproses, vanaf die
keuse van 'n uitstalterna tot die evaluering van die uitstalling, word ondersoek. Die
uitstaIontwerper vertolk die belangrike rol om die navorsingsresultate te interpreteer en 'n
ontwerpoplossing daaruit saam te stel.
'n Groot verskeidenheid uitstaltegnieke word vir die ontwerpoplossing aanbeveel, wat
onder meer teateraanbiedings, spesiale beligting- en klankeffekte, demonstrasies en toere
insluit. 'n Verskeidenheid figure word ingesluit waar foto's, geneem tydens die ter plaatse
ondersoeke, en ontwerpsketse 'n aanduiding van die ontwerpoplossing gee.
Uit die navorsingsresultate kon daar vasgestel word dat 'n opvoedkundige onderwerp soos
die mollusk/skulp, deur die gebruik van kreatiewe, eietydse en relevante uitstaltegnieke, vir
die museumbesoeker aktueel en aantreklik gemaak kan word.
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[en] STABILITY ANALYSIS OF LAMINATED COMPOSITE CYLINDRICAL SHELLS AND PANELSSTABILITY ANALYSIS OF LAMINATED COMPOSITE CYLINDRICAL SHELLS AND PANELS / [es] INESTABILIDAD DE CORTEZAS Y PANELES CILÍNDRICOS LAMINADOS DE MATERIALES COMPUESTOS / [pt] INSTABILIDADE DE CASCAS E PAINÉIS CILÍNDRICOS LAMINADOS DE MATERIAIS COMPÓSITOSROMAN AUGUSTO ARCINIEGA ALEMAN 14 September 2001 (has links)
[pt] Este trabalho apresenta um estudo do comportamento não-
linear e instabilidade de cascas e painéis cilíndricos
laminados de materiais compósitos. Com esta finalidade é
desenvolvida uma formulação de alta ordem de deformação
cisalhante que leva en conta estes efeitos nas relações
deformação-deslocamento. O comportamento da casca é
descrito por uma consistente teoria não-linear para cascas
laminadas que considera pequenas deformações e rotações
moderadas e incorpora automaticamente o efeito das
deformações cisalhantes. O modelo de bifurcação clássico é
utilizado para estudar a estabilidade da casca compósita. O
comportamento pós-crítico é examinado a partir de uma
solução modal obtida com técnicas de perturbação. Em ambos
os casos aplica-se o método de Rayleigh-Ritz para
discretizar o sistema de equações diferenciais de
equilíbrio em um sistema de equações algébricas. O método
de Newton-Raphson é empregado na resolução das equações não-
lineares de equilíbrio do caminho pós-crítico e na obtenção
do caminho fundamental da estrutura imperfeita. A
implementação numérica (em álgebra simbólica) é feita
utilizando a linguagem de programação Maple V release 3.
É então desenvolvido um estudo paramétrico com o objetivo
de determinar a influência dos parâmetros geométricos e das
características próprias do laminado (número de lâminas e
orientação das fibras) na resposta crítica e pós-crítica da
casca compósita para dois tipos de carregamento, a saber:
pressão lateral e compressão axial. É analisado, também, o
grau de sensibilidade às imperfeições geométricas destas
estruturas. São apresentadas comparações dos resultados
teóricos aqui obtidos com outros existentes na literatura
com o objetivo de demonstrar a confiabilidade da formulação
e metodologia numérica aqui desenvolvidas. / [en] The purpose of the present work is to study the non-linear
behaviour and instability of laminated composite
cylindrical shells and panels under axial and pressure
loading. The analysis is performed within a refined non-
linear theory for composite laminated shells incorporating
the effects of transverse shear and the geometric
imperfections. The classical bifurcation theory is used to
analyze the critical behavior of the shell. To examine the
post-critical behavior of the shell, a modal solution based
on the basic ideas of Koiter`s theory is deduced and the
Rayleigh-Ritz method together with the Newton-Raphson
strategy are used to solve the non-linear equilibrium
problem and plot either the post-critical path or the non-
linear equilibrium path of the imperfect shell. The
analytical and numerical procedures were performed by the
use of the symbolic algebra package Maple V release 3.
The influence played by the geometrical parametrs of the
shell and physical parameters of the composite laminate,
such as stacking sequences and fiber orientation in each
lamina, on the critical and post-critical behavior of the
shell is examined and a series of conclusions are outlined.
The imperfection sensitivity of these shells is also
analyzed. Comparisons of the present results with those
obtained by other theories and experiments are found to be
satisfactory and show the validity of the present
methodology. / [es] Este trabajo presenta un estudio de la inestabilidad y
comportamiento no lineal y la inestabilidad de cortezas y
paneles cilíndricos laminados de materiales compuestos. Con
esta finalidad se desarrolla una formulación de alta orden
de deformación cisallante que considera estos hechos en las
relaciones deformación desplazamiento. EL comportamiento de
la corteza se describe a través de una consistente teoría
no lineal para cascas laminadas. Esta teoría considera
pequeñas deformaciones y rotaciones moderadas e incorpora
automáticamente las deformaciones cisallantes. El modelo de
bifurcación clásico se utiliza para estudiar la estabilidad
de la corteza. El comportamiento poscrítico se examina a
partir de una solución modal obtenida con técnicas de
perturbación. En ambos casos se aplica el método de
Rayleigh Ritz para discretizar el sistema de ecuaciones
diferenciales de equilibrio en un sistema de ecuaciones
algébraicas. El método de Newton Raphson es utilizado en la
resolución de las ecuaciones no lineares de equilibrio del
camino postcrítico y en la obtención del camino fundamental
de la extructura imperfecta. La implementación numérica (en
álgebra simbólica) se realiza utilizando el lenguaje de
programación Maple V release 3. Con el objetivo de
determinar la influencia de los parámetros geométricos y de
las características proprias del laminado en la respuesta
crítica y postcrítica de la casca compósita, se realiza un
estudio paramétrico para para dos tipos de carga: presión
lateral y compresión axial. Se analiza también, el grado de
sensibilidad a las imperfeiciones geométricas de estas
extructuras. Finalmente, y con el objetivo de demostrar la
confiabilidad de la formulación y la metodología numérica
aqui desarrolladas, se comparan los resultados teóricos
obtenidos con los reportados en la literatura.
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[en] INFLUENCE OF INITIAL GEOMETRIC IMPERFECTIONS ON THE INTERNAL RESONANCES AND NON-LINEAR VIBRATIONS OF THIN-WALLED CYLINDRICAL SHELLS / [pt] INFLUÊNCIA DE IMPERFEIÇÕES GEOMÉTRICAS INICIAIS NAS RESSONÂNCIAS INTERNAS E VIBRAÇÕES NÃO LINEARES DE CASCAS CILÍNDRICAS ESBELTASLARA RODRIGUES 30 November 2018 (has links)
[pt] A análise das ressonâncias internas em sistemas estruturais contínuos é uma das principais áreas de pesquisa no campo da dinâmica não linear. A ressonância interna entre dois modos de vibração ocorre quando a proporção de suas frequências naturais é um número inteiro. De particular importância, devido à sua influência na resposta estrutural, é a ressonância interna 1:1, geralmente associada às simetrias do sistema, a ressonância interna 1:2, devida às não linearidades quadráticas e a ressonância 1:3 decorrente de não linearidades cúbicas. A ressonância interna permite a transferência de energia entre os modos de vibração relacionados, levando geralmente a novos fenômenos com profunda influência sobre a estabilidade da resposta dinâmica. As cascas de revolução geralmente exibem ressonâncias internas devido à inerente simetria circunferencial e um denso espectro de frequência em sua faixa de frequências mais baixas. Isso pode levar não apenas a ressonâncias internas do tipo m:n, mas a múltiplas ressonâncias internas. Nesta tese é realizada a análise de múltiplas ressonâncias internas em cascas cilíndricas delgadas, em particular as ressonâncias internas de 1:1:1:1 e 1:1:2:2 são investigadas em detalhes, um tópico pouco explorado na literatura técnica. A investigação de ressonâncias internas em sistemas contínuos geralmente é realizada usando modelos discretos de baixa dimensão. Embora alguns trabalhos anteriores tenham investigado ressonâncias internas do tipo m:n em cascas cilíndricas, muitos resultados não são consistentes, uma vez que os modelos discretos derivados não consideram os acoplamentos modais devido a não linearidades quadráticas e cúbicas. Aqui, usando um procedimento de perturbação, expansões modais consistentes são derivadas para um número arbitrário de modos de interação, levando a modelos de baixa dimensão confiáveis. A precisão desses modelos é corroborada usando o método Karhunen-Loève. Finalmente, é bem sabido que pequenas imperfeições geométricas da ordem da espessura da casca têm uma forte influência na sua resposta não linear. No entanto, sua influência nas ressonâncias internas, instabilidade dinâmica e transferência de energia é desconhecida. Assim, a influência de diferentes tipos de imperfeição modal é devidamente considerada na presente análise. Utilizando os modelos discretos aqui derivados, é apresentada uma análise detalhada das bifurcações, utilizando técnicas de continuação e o critério de estabilidade de Floquet, esclarecendo a importância das ressonâncias internas nas vibrações não lineares e instabilidades de cascas cilíndricas. Os resultados também confirmam que a forma e a magnitude das imperfeições geométricas iniciais têm uma influência profunda nos resultados, permitindo ou impedindo a transferência de energia entre os modos ressonantes considerados. / [en] The analysis of internal resonances in continuous structural systems is one of the main research areas in the field of nonlinear dynamics. Internal resonance between two vibration modes occur when the ratio of their natural frequencies in an integer number. Of particular importance, due to its influence on the structural response, is the 1:1 internal resonance, usually associated with system symmetries, the 1:2 internal resonance, due to quadratic nonlinearities, and the 1:3 resonance arising from cubic nonlinearities. The internal resonance enables the energy transfer between the related vibration modes, leading usually to new phenomena with profound influence on the stability of the dynamic response. Shells of revolution usually exhibit internal resonances due to the inherent circumferential symmetry and a dense frequency spectrum in their lower frequency range. This may lead not only to m:n internal resonances, but also multiple internal resonances. In this thesis, the analysis of multiple internal resonances in slender cylindrical shells is conducted, in particular 1:1:1:1 and 1:1:2:2 internal resonances are investigated in detail, a topic rarely found in the technical literature. The investigation of internal resonances in continuous systems is usually conducted using low dimensional discrete models. Although some previous works have investigated m:n internal resonances in cylindrical shells, many results are not consistent since the derived discrete models do not consider the modal couplings due to quadratic and cubic nonlinearities. Here, using a perturbation procedure, consistent modal expansions are derived for an arbitrary number of interacting modes, leading to reliable low dimensional models. The accuracy of these models is corroborated using the Karhunen-Loève method. Finally, it is well known that small geometric imperfections of the order of the shell thickness has a strong influence on the shell nonlinear response. However, their influence on internal resonances, dynamic instability and energy transfer is largely unknown. Thus, the influence of different types of modal imperfection is properly considered in the present analysis. Using the derived discrete models, a detail bifurcation analysis, using continuation techniques and Floquet stability criterion, is presented, clarifying the importance of internal resonances on the nonlinear vibrations and instabilities of cylindrical shells. The results also confirm that the form and magnitude of initial geometric imperfections has a profound influence on the results enabling or preventing the energy transfer among the considered resonant modes.
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Um elemento finito de tubo tridimensional para análise geometricamente não linear de dutos / A threedimensional pipe finite element for geometric nonlenear analysesMachado, Alexandre Cunha 03 April 2006 (has links)
In transport of fluids or even as structural elements, cylindrical shells are widely
used in several segments of structure engineering. The understanding of the behavior of
this type of structure along a trajectory of equilibrium resultant of a description of
historical loading of different natures and, consequently, is important in the definition of
the real load capacity of the ducts. In this work, a finite element for geometric and threedimensional
nonlinear analyses of pipes is developed. Taking into account the nature of
the analysis, proper measure of tension and deformation that are compatible with states
of large deformations and displacements are studied. The Total Lagrangean formulation
is adopted, but the constitutive relationships used are linear. The developed
computational implementation uses a three-dimensional finite element of pipe with 2 or
3 nodes, compatible with the state of great deformations and displacements, and, also,
incorporating the movements of rigid body of the structure.In order to map the
nonlinear trajectories of equilibrium, using some methodologies proposed in the
literature, a structure of Object-Oriented Programming is used. It allows the application
of different techniques of incremental and iterative analysis integrated to the
implementation of the aforementioned finite elements.Aiming to validate the
formulation, the results obtained by using the program here developed are evaluated
through their comparison with analytical solutions and previously published results. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / No transporte de fluidos ou mesmo como elementos estruturais as cascas
cilíndricas são largamente utilizadas em diversos segmentos da engenharia civil. A
compreensão do comportamento desse tipo de estrutura ao longo de uma trajetória de
equilíbrio resultante de um histórico de carregamento de diferentes naturezas é
importante na definição da real capacidade portante dos dutos. Neste trabalho,
desenvolve-se um elemento finito para análises geometricamente não lineares
tridimensionais de tubos. Levando-se em consideração a natureza da análise, são
estudadas medidas adequadas de tensão e deformação, compatíveis com regimes de
grandes deformações e deslocamentos. A formulação Lagrangeana Total é adotada, mas
as relações constitutivas utilizadas são lineares. A implementação computacional
desenvolvida emprega um elemento finito tridimensional de tubo com 2 ou 3 nós,
compatível com o regime de grandes deformações e deslocamentos, incorporando,
também, os movimentos de corpo rígido da estrutura. Com o objetivo de mapear as
trajetórias não lineares de equilíbrio, utilizando-se algumas metodologias propostas na
literatura, é usada uma estrutura de programação orientada a objetos, permitindo a
aplicação de diferentes técnicas de análise incremental e iterativa integradas à
implementação de elementos finitos supracitada. Visando validar a formulação, os
resultados obtidos no programa desenvolvido são avaliados através da comparação com
soluções analíticas e outras análises numéricas disponíveis na literatura.
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