Submitted by Cláudia Bueno (claudiamoura18@gmail.com) on 2015-10-27T18:16:56Z No. of bitstreams: 2 Dissertação - Renato de Sousa e Silva - 2015.pdf: 7212801 bytes, checksum: 41d5a93b0ae749a6418b871cd4fea683 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-10-28T14:29:10Z (GMT) No. of bitstreams: 2 Dissertação - Renato de Sousa e Silva - 2015.pdf: 7212801 bytes, checksum: 41d5a93b0ae749a6418b871cd4fea683 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-10-28T14:29:10Z (GMT). No. of bitstreams: 2 Dissertação - Renato de Sousa e Silva - 2015.pdf: 7212801 bytes, checksum: 41d5a93b0ae749a6418b871cd4fea683 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-06-12 / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / Structural elements with large deformation capacity as hyperelastic membranes are gaining prominence in several engineering branches and have applications in biomechanics, thus the study of the dynamic behavior of hyperelastic structures is very important to minimize effects as the loss of the stability and undesirable vibrations. In this paper the elasticity theory for large deformations in the development of membrane theory, in order to investigate the linear and nonlinear dynamic behavior of hyperelastic membrane is used. A rectangular membrane composed of an elastomeric material, isotropic, homogeneous, incompressible and consisting of neo-Hookeano, Mooney-Rivlin and Yeoh models is considered. To model the membrane, the energy and work of external forces are used together with the application of the Hamilton on the Lagrange function. The Galerkin method is applied to obtain a discretized system of nonlinear Partial Differential Equations (PDE) and the Runge-Kutta method of 4th order is used to obtain its time response. Finally, the Brute Force and Continuation methods are applied to investigate the nonlinear dynamic behavior of the membrane. A parametric analysis is carried out looking to evaluate the influence of the material, geometry and initial tensions on the natural frequencies of the membrane. It is noted that increasing the size of a tensioned membrane, it is also increased the natural frequency for a given amplitude, and increasing the strength of a pre-tensioned membrane, the smaller the value of the frequency in relation to a range. Small differences are perceived in the behavior of the membrane for the three constitutive models of material, which are calibrated to represent the same material. Moreover, the main bifurcations of the analyzed membranes are of cyclic bending type, known as saddle-node bifurcation. / Elementos estruturais com grande capacidade de deformação como membranas hiperelásticas vêm ganhando destaque em diversas áreas da engenharia e têm várias aplicações na biomecânica, assim, o estudo do comportamento dinâmico de estruturas hiperelásticas é de grande importância visando minimizar os efeitos, como à perda de estabilidade e vibrações indesejáveis. No presente trabalho é utilizada a teoria da elasticidade para grandes deformações no desenvolvimento da teoria de membranas com o objetivo de investigar o comportamento dinâmico linear e não linear de membranas hiperelásticas. Considera-se a membrana retangular composta por um material elastomérico, isotrópico, homogêneo, incompressível e descrito pelos modelos constitutivos de neo-Hookeano, Mooney-Rivlin e Yeoh. Para obter as equações de equilíbrio estático e dinâmico da estrutura são utilizadas as energias e trabalhos atuantes, bem como o princípio de Hamilton aplicado na função de Lagrange. O Método de Galerkin é utilizado para discretizar as Equações Diferenciais Parciais (EDP) em um sistema de Equações Diferenciais Ordinárias (EDO). Para resolver esse sistema, utiliza-se o Método de Runge-Kutta de quarta ordem e utiliza-se o Método da Força Bruta e o Método da Continuação para investigar o comportamento dinâmico da membrana. É realizada uma análise paramétrica visando avaliar a influência do material e da geometria da membrana nas frequências naturais e nas tensões inicias. Constata-se que as bifurcações das membranas analisadas são do tipo Dobra Cíclica, conhecida como Nó-Sela. Além de verificar que quanto menor o nível de tração, maior será a não linearidade da curva de frequênciaamplitude da membrana e que há leves divergências no comportamento da membrana em relação aos três modelos constitutivos do material adotados.

Elastomer seals are used in a variety of industries that require flow isolation. The characterization of the behavior of these seals remains largely unexplored and hence, this study is focused on simulating and validating the axial-compressive behavior of an annular rubber seal constrained concentrically in a pipe. The elastomer material composing the seal, was experimentally characterized for its mechanical, frictional, and viscoelastic properties and modelled using models developed by Yeoh, Thirion, and Prony respectively. A 2D axisymmetric finite-element model was developed using ANSYS 16 and used alongside the material models to simulate an axial load versus displacement curve, a contact pressure distribution, and a pipe hoop strain gradient. The results for quasi-static loading and viscoelastic effects agreed within 7% and 18% of the experimental results, respectively. It was observed that pipe geometry, rubber chemistry, frictional properties, and viscoelastic effects have significant effect on the compressive behavior of the seal. / October 2016

Att implementera ett beslutsstöd i en organisation är en resurskrävande och komplicerad uppgift där problem ofta uppstår. Syftet med denna studie är därför att identifiera de kritiska framgångsfaktorer som ideella organisationer bör ta hänsyn till när de implementerar ett beslutsstöd. Studien har genomförts med hjälp av intervjuer med ideella organisationer i välgörenhetssektorn. Erhållen empiri har analyserats utifrån Yeoh and Koronios Model of critical success factors for BI systems som ansats. Vår studie redogör hur och om Yeoh och Koronios (2010) faktorer har kommit att spela en betydande roll för de organisationer vi intervjuat. Resultatet av studien redovisar en uppsättning kritiska framgångsfaktorer vi lyckas identifiera i relation till vår ansats. Vi redovisar även vilka specifika framgångsfaktorer vi kunnat identifiera för ideella organisationer.

There is a high demand for implementing simulations in the design and product devel-opment processes, avoiding the execution of costly tests on prototypes and giving thechance of discarding unsuitable designs, as well as exploring possible ones without much cost added.This project assignment is to find a suitable way to simulate drop tests on two typesof PMMA sheets, a material widely used on luminaire covers. Therefore, it becomesnecessary to study the mechanical behavior of these materials, using experimental tests,in order to calibrate the material models used in the simulations.During the experimental testing, common polymer behaviors were found on the twostudied materials, such as rate dependence, non-linear elasticity, viscoelasticity and vis-coplasticy. Behaviors which presented several challenges regarding the choice and cali-bration of the material models.The two di?erent polymers were calibrated for the simulations using two di?erentmaterial models. An elastic-plastic (Drucker Prager Plasticity) model was used for oneof the materials, whereas an hyperelastic-viscoelastic model was used for the other one.Finally, several drop tests simulations were conducted and compared with experimentaltests

This thesis deals with problems of biomechanics of soft tissues, namely of stress-strain analysis of abdominal aortic aneurysm (AAA). The introduction describes briefly the possibility of aneurysm occurrence with a focus on an aneurysm in the abdominal aorta.

This thesis deals with problems of biomechanics of soft tissues, namely of stress-strain analysis of abdominal aortic aneurysm (AAA). The introduction describes briefly the possibility of aneurysm occurrence with a focus on an aneurysm in the abdominal aorta.