C��lculo del asiento el��stico tridimensional de cimentaciones de rigidez variable en terrenos con una capa r��gida inclinada

Las f��rmulas basadas en la teor��a de la elasticidad son ampliamente utilizadas para el c��lculo de asientos de cimentaciones, ya que la totalidad de la normativa geot��cnica recomienda su empleo. No obstante, estos m��todos no cubren todas las situaciones geot��cnicamente posibles ya que frecuentemente las condiciones geol��gicas son complejas. En este trabajo se analiza la influencia de la presencia de una capa r��gida inclinada en los asientos el��sticos de una cimentaci��n superficial. Para ello se han resuelto 273 modelos tridimensionales no lineales de elementos finitos, variando los par��metros clave del problema: la inclinaci��n y la profundidad de la capa r��gida y la rigidez de la cimentaci��n. Finalmente, se ha realizado un an��lisis estad��stico de los resultados de los modelos y se ha propuesto una f��rmula que puede ser utilizada en el c��lculo de asientos por m��todos el��sticos, para tener en consideraci��n la presencia de una capa r��gida inclinada en profundidad.

An��lisis computacional del comportamiento termo-mec��nico de materiales con aplicaci��n a la industria automotriz

Para la supervivencia de cualquier industria en un mercado cada vez m��s competitivo resulta esencial mejorar la calidad del producto y reducir costos. Como parte de esa tendencia, el proceso de dise��o, tanto de bienes como de procesos de manufactura, debe ser confiable e insumir el menor tiempo posible para permitir agilidad y eficacia en los cambios y las innovaciones que requiere el mercado. Es necesario abandonar los procesos de desarrollo basados en largas y costosas secuencias de prueba y error y reemplazarlos por procedimientos m��s cortos y eficientes. Las herramientas inform��ticas y los modelos computacionales han contribuido en gran medida a lograr dicho objetivo. Estos m��todos son cada vez m��s utilizados en industrias tan importantes como la automotriz o la de maquinaria y equipamiento agr��cola, ambas de relevante importancia en la actividad econ��mica de nuestra provincia. En las mencionadas industrias, con la intenci��n de mejorar las prestaciones del producto, de reducir costos de mantenimiento para igual prestaci��n y, sobre todo, con el objetivo de disminuir el peso total del veh��culo, factor importante en relaci��n con el ahorro de combustible, es habitual la sustituci��n de algunos materiales tradicionalmente utilizados por otros con mejor relaci��n prestaci��n/costo y prestaci��n/peso. Dentro de este grupo de nuevos materiales que se emplean en la industria automotriz se encuentran los compuestos, las aleaciones ligeras y la fundici��n d��ctil, los cuales han estado substituyendo al acero o a la fundici��n gris en algunas piezas. La meta de esta investigaci��n es generar modelos computacionales multiescala de: a) el proceso de tratamiento t��rmico de austemperizado de la fundici��n d��ctil, b) el comportamiento mec��nico de elementos de fundici��n d��ctil y c) el comportamiento mec��nico de material compuesto de matriz epoxi y fibra de vidrio con da��o higrot��rmico. Se usar��n simulaciones acopladas de meso y macromec��nica. El principal postulado es que la representaci��n de la mesomec��nica del material acoplada a la macromec��nica conduce a resultados que mejoran las predicciones con respecto a modelos planteados s��lo a nivel macrosc��pico. El dominio macrosc��pico se representar�� con elementos finitos y en ese nivel se resolver��n problemas t��rmicos y mec��nicos. En la mesoescala se emplear��n leyes fenomenol��gicas para el aspecto metal��rgico del austemperizado y elementos finitos para el an��lisis del comportamiento micromec��nico de la fundici��n d��ctil y del material compuesto. Los productos resultantes de la investigaci��n ser��n software y metodolog��as que puedan ser utilizadas en la mejora del dise��o de piezas de fundici��n d��ctil y de materiales compuestos y en el ajuste del tratamiento de austemperizado de la fundici��n d��ctil que permita obtener la microestructura requerida. Desde un punto de vista acad��mico y en relaci��n con la tem��tica planteada en el proyecto, tres integrantes llevar��n a cabo sus estudios doctorales y se publicar��n resultados en revistas internacionales

Avalia����o t��rmica provocada pela fura����o no tecido ��sseo

Este trabalho tem como objetivo avaliar o efeito da temperatura no osso devido ao aquecimento provocado pelo processo de fura����o. Foram realizadas visitas a duas cl��nicas para acompanhamento da t��cnica de implantologia dent��ria e recolhidas imagens termogr��ficas para a leitura da temperatura gerada na broca ap��s o processo de fura����o. Na coloca����o de implantes dent��rios por exemplo, as vari��veis que interferem no processo de fura����o do osso s��o: a velocidade, o material, o di��metro, o comprimento e a geometria da ponta da broca. Com este trabalho pretende-se verificar, experimental e numericamente, as vari��veis que interferem no aquecimento da estrutura ��ssea. Para isso, s��o utilizados materiais comp��sitos com caracter��sticas similares ao osso cortical e trabecular. A metodologia apresentada revela-se ��til e diferenciadora de outros trabalhos, pois s��o utilizados materiais com caracter��sticas similares aos materiais in vivo. Os m��todos experimentais utilizados em laborat��rio s��o baseados nas t��cnicas de termografia e termopares durante a fura����o dos diferentes materiais. Paralelamente, s��o utilizados modelos te��ricos num��ricos, com o recurso �� t��cnica de elementos finitos, para a discuss��o de resultados. Ap��s a elabora����o do trabalho conclui-se que a temperatura na broca �� superior �� temperatura no osso e aumenta consoante a estrutura do material, isto ��, se o material possuir cavidades na sua estrutura a temperatura na broca n��o �� t��o elevada como no material compacto.

An��lise num��rica de dutos enterrados sujeitos a eleva����o e recalque localizado

Problems associated to longitudinal interactions in buried pipelines are characterized as three-dimensional and can lead to different soil-pipe issues. Despite the progress achieved in research on buried pipelines, little attention has been given to the three-dimensional nature of the problem throughout the last decades. Most of researches simplify the problem by considering it in plane strain condition. This dissertation aims to present a study on the behavior of buried pipelines under local settlement or elevation, using three-dimensional simulations. Finite element code Plaxis 3D was used for the simulations. Particular aspects of the numerical modeling were evaluated and parametric analyzes were performed, was investigated the effects of soil arching in three-dimensional form. The main variables investigated were as follows: relative density, displacement of the elevation or settlement zone, elevated zone size, height of soil cover and pipe diameter/thickness ratio. The simulations were performed in two stages. The first stage was involved the validation of the numerical analysis using the physical models put forward by Costa (2005). In the second stage, numerical analyzes of a full-scale pipeline subjected to a localized elevation were performed. The obtained results allowed a detailed evaluation of the redistribution of stresses in the soil mass and the deflections along the pipe. It was observed the reduction of stresses in the soil mass and pipe deflections when the height of soil cover was decreased on regions of the pipe subjected to elevation. It was also shown for the analyzed situation that longitudinal thrusts were higher than vi circumferential trusts and exceeded the allowable stresses and deflections. Furthermore, the benefits of minimizing stress with technical as the false trench, compressible cradle and a combination of both applied to the simulated pipeline were verified

Estudo de um sistema de frenagem eletromagn��tica empregando correntes parasitas

This work deals with the analytical, computational and experimental study of phenomena related to the Eddy current induction in low permeability means for embedded electromagnetic braking systems applications. The phenomena of forces generation in opposing to the variation of stationary magnetic flux produced by DC power supplies, set in motion by the application of an external propulsive force are addressed. The study is motivated by search for solving the problem of speed control of PIGs used to verifying and maintaining pipelines, and is led based on the analytical models synthesis, validated by means of computer simulations in Finite Elements environment, provided by engineering support software; and with experimental tests conducted under controlled laboratory conditions. Finally, a damping systems design methodology based on analyzes results conducted throughout the study is presented

An��lise do fluxo d�����gua na barragem Engenheiro Armando Ribeiro Gon��alves - A��u/RN

The solution of partial differential equation of seepage problems is difficult to find analytically, especially for situations that involve great complexity. To overcome this problem, software based on finite differences and finite elements are usually used. This work presents the use of a finite element software, the GEO5, to solve the seepage problem at a dam of very complex section, the dam Eng. Armando Ribeiro Gon��alves, which at the end of its construction suffered rupture of the upstream slope at the central dam and then went through a process of reconstruction and auscultation. The analyses were performed for the operating condition of the reservoir, with an established flow. A numerical model was developed based on the level readings of the reservoir water and their piezometric readings as a proposal for the evaluation and future behavior prediction of the dam on established flow conditions. The use of constitutive models with the aid of computer systems is reflected in a way to predict future risk situations so they can be prevented

Modelagem computacional para avalia����o da intera����o entre pain��is de alvenaria e estrutura de suporte em concreto armado

The developed study proposes a new computer modeling efficient and easy to apply in usual project situations to evaluate the interaction between masonry panels and support structure. The proposed model simulates the behavior of the wall exclusively using frame finite elements, thus compounding an equivalent frame. The validation was performed in two ways: firstly, through the analysis of various panels of generic plans, comparing the results obtained from equivalent frame model with the ones from a reference model, which uses shell finite elements in discretization of the walls�� and in a second step, comparing with the results of the experimental model of Rosenhaupt. The analyzes considered the linear elastic behavior for materials and consisted basically in the evaluation of vertical displacements and efforts in support beams, and tensions at the base of walls. Was also evaluated, from flat and threedimensional modeling of some walls from a real project, important aspects of the wall-beam interaction, e.g.: the presence of openings of doors and windows, arranged in any position�� conditions of support and linking of beams�� interference of moorings between walls�� and consideration of wind action. The analysis of the achieved results demonstrated the efficiency of the proposed modeling, since they have very similar aspects in the distribution of stresses and efforts, always with intensities slightly larger than those of the reference and experimental models.

A influ��ncia do amortecimento viscoel��stico na estabilidade aeroel��stica de pain��is aeron��uticos

Since the creation of supersonic vehicles, during the Second World War, the engineers have given special attention to the interaction between the aerodynamic efforts and the structures of the aircrafts due to a highly destructive phenomenon called flutter in aeronautical panel. Flutter in aeronautical panels is a self-excited aeroelastic phenomenon, which can occurs during supersonic flights due to dynamic instability of inertia, elastic and aerodynamic forces of the system. In the flutter condition, when the critical aerodynamic pressure is reached, the vibration amplitudes of the panel become dynamically unstable and increase exponentially with time, affecting significantly the fatigue life of the existing aeronautical components. Thus, in this paper, the interest is to investigate the possibility of reducing the effects of the supersonic aeroelastic instability of rectangular plates by applying passive constrained viscoelastic layers. The rationale for such study is the fact that as the addition of viscoelastic materials provides decreased vibration amplitudes it becomes important to quantify the suppression of plate flutter coalescence modes that can be obtained. Moreover, despite the fact that much research on the suppression of panel flutter has been carried out by using passive, semi-active and active control techniques, very few of them are adapted to deal with the problem of estimating the flutter speeds of viscoelastic systems, since they must conveniently account for the frequency- and temperature-dependent behavior of the viscoelastic material. In this context, two different model of viscoelastic material are developed and applied to the model of sandwich plate by using finite elements. After the presentation of the theoretical foundations of the methodology, the description of a numerical study on the flutter analysis of a three-layer sandwich plate is addressed.

Avalia����o comparativa da remodela����o ��ssea periimplantar em implantes com jun����o cone-morse e hex��gono externo: estudo cl��nico randomizado controlado, duplo cego, boca dividida

Background: Several theories, such as the biological width formation, the inflammatory reactions due to the implant-abutment microgap contamination, and the periimplant stress/strain concentration causing bone microdamage accumulation, have been suggested to explain early periimplant bone loss. However, it is yet not well understood to which extent the implant-abutment connection type may influence the remodeling process around dental implants. Aim: to evaluate clinical, bacteriological, and biomechanical parameters related to periimplant bone loss at the crestal region, comparing external hexagon (EH) and Morse-taper (MT) connections. Materials and methods: Twelve patients with totally edentulous mandibles received four custom made �� 3.8 x 13 mm implants in the interforaminal region of the mandible, with the same design, but different prosthetic connections (two of them EH or MT, randomly placed based on a split-mouth design), and a immediate implant- supported prosthesis. Clinical parameters (periimplant probing pocket depth, modified gingival index and mucosal thickness) were evaluated at 6 sites around the implants, at a 12 month follow-up. The distance from the top of the implant to the first bone-to-implant contact ��� IT-FBIC was evaluated on standardized digital peri-apical radiographs acquired at 1, 3, 6 and 12 months follow-up. Samples of the subgingival microbiota were collected 1, 3 and 6 months after implant loading. DNA were extracted and used for the quantification of Tanerella forsythia, Porphyromonas gingivalis, Aggragatibacter actinomycetemcomitans, Prevotella intermedia and Fusobacterium nucleatum. Comparison among multiple periods of observation were performed using repeated-measures Analysis of Variance (ANOVA), followed by a Tukey post-hoc test, while two-period based comparisons were made using paired t- test. Further, 36 computer-tomographic based finite element (FE) models were accomplished, simulating each patient in 3 loading conditions. The results for the peak EQV strain in periimplant bone were interpreted by means of a general linear model (ANOVA). Results: The variation in periimplant bone loss assessed by means of radiographs was significantly different between the connection types (P<0.001). Mean IT-FBIC was 1.17��0.44 mm for EH, and 0.17��0.54 mm for MT, considering all evaluated time periods. All clinical parameters presented not significant differences. No significant microbiological differences could be observed between both connection types. Most of the collected samples had very few pathogens, meaning that these regions were healthy from a microbiological point of view. In FE analysis, a significantly higher peak of EQV strain (P=0.005) was found for EH (mean 3438.65 �����) compared to MT (mean 840.98 �����) connection. Conclusions: Varying implant-abutment connection type will result in diverse periimplant bone remodeling, regardless of clinical and microbiological conditions. This fact is more likely attributed to the singular loading transmission through different implant-abutment connections to the periimplant bone. The present findings suggest that Morse-taper connection is more efficient to prevent periimplant bone loss, compared to an external hexagon connection.

Strength of the Iberian intraplate lithosphere: Cenozoic deformations and seismicity

Previous studies about the strength of the lithosphere in the Iberia centre fail to resolve the depth of earthquakes because of the rheological uncertainties. Therefore, new contributions are considered (the crustal structure from a density model) and several parameters (tectonic regime, mantle rheology, strain rate) are checked in this paper to properly examine the role of lithospheric strength in the intraplate seismicity and the Cenozoic evolution. The strength distribution with depth, the integrated strength, the effective elastic thickness and the seismogenic thickness have been calculated by a finite element modelling of the lithosphere across the Central System mountain range and the bordering Duero and Madrid sedimentary basins. Only a dry mantle under strike-slip/extension and a strain rate of 10-15 s-1, or under extension and 10-16 s-1, causes a strong lithosphere. The integrated strength and the elastic thickness are lower in the mountain chain than in the basins. These anisotropies have been maintained since the Cenozoic and determine the mountain uplift and the biharmonic folding of the Iberian lithosphere during the Alpine deformations. The seismogenic thickness bounds the seismic activity in the upper���middle crust, and the decreasing crustal strength from the Duero Basin towards the Madrid Basin is related to a parallel increase in Plio���Quaternary deformations and seismicity. However, elasto���plastic modelling shows that current African���Eurasian convergence is resolved elastically or ductilely, which accounts for the low seismicity recorded in this region.

Experimentaci��n, simulaci��n y an��lisis de artefactos improvisados-proyectiles formados por explosi��n

Dentro de los artefactos explosivos improvisados se encuentran aquellos que generan proyectiles formados por explosi��n, penetradores de blindajes y sistemas acorazados, como los utilizados por grupos insurgentes contra las fuerzas aliadas en zona de operaciones. El objeto de este estudio es reproducir y entender el comportamiento de dichos artefactos explosivos improvisados capaces de generar proyectiles de alta velocidad y gran capacidad de penetraci��n. La comprensi��n de su comportamiento permitir�� mejorar el conocimiento sobre ellos, y por ende, combatirlos de forma m��s eficaz. Para ello se han realizado los ensayos correspondientes, obteni��ndose las primeras caracterizaciones de proyectiles formados por explosi��n construidos de manera artesanal, tal y como har��a un terrorista. Adem��s, se han creado los modelos num��ricos correspondientes a cada ensayo, que simulan todo el evento desde su inicio hasta el impacto en el objetivo, recorriendo todos los pasos intermedios. Se han ensayado 3 configuraciones y posteriormente se han simulado, usando el software de an��lisis por elementos finitos, LS-DYNA, con una configuraci��n 2D axisim��trica, con mallados lagrangianos. Los resultados obtenidos por el modelo han alcanzado un alto grado de precisi��n con relaci��n a los datos experimentales. A partir de aqu�� se puede concluir que los artefactos explosivos improvisados-proyectiles formados por explosi��n son una seria amenaza, y que los modelos generados permitir��n conocer y ahorrar costes en la lucha contra esta amenaza, y por ende contra el terrorismo, al disponer de un enfoque hol��stico de la amenaza, y finalmente reducir los costes de la experimentaci��n.

Algoritmos de otimiza����o e o problema inverso aplicados �� identifica����o de danos estruturais com o uso do MEF

Disserta����o (mestrado)���Universidade de Bras��lia, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2015.

Valida����o num��rica de leis coesivas triangulares para previs��o de resist��ncia de juntas adesivas em tra����o e corte puros

As liga����es adesivas surgiram pela necessidade de se encontrar formas de unir componentes, por vezes de materiais distintos, atrav��s de t��cnicas mais vantajosas. Atualmente, qualquer estrutura deve ser resistente, robusta e leve, o que amplificou o interesse industrial e investiga����o nas liga����es adesivas, principalmente na melhoria das propriedades de resist��ncia e fratura de materiais. Desta forma, nos ��ltimos anos, a utiliza����o de juntas adesivas em aplica����es industriais tem aumentando gradualmente, substituindo alguns m��todos de liga����o tradicionais, por apresentarem vantagens, tais como redu����o de concentra����o de tens��es, reduzido peso e facilidade de processamento/fabrico. Em qualquer ��rea da ind��stria, a aplica����o em larga escala de uma determinada t��cnica de liga����o sup��e que est��o dispon��veis ferramentas confi��veis para o projeto e previs��o da rotura. Neste ��mbito, os Modelos de Dano Coesivo (MDC) s��o uma ferramenta fundamental, apesar de ser necess��rio estimar as leis coesivas do adesivo �� tra����o e corte para entrada nos modelos num��ricos. Nesta disserta����o o trabalho experimental consistiu no tratamento de dados com vista �� obten����o de GIc e GIIc, com a devida compara����o de diferentes m��todos de redu����o, bem como potencialidades e limita����es dos mesmos. �� realizada uma compara����o dos tr��s adesivos: Araldite�� AV138, Araldite�� 2015 e SikaForce�� 7752. Neste trabalho estudou-se tamb��m numericamente a adequa����o de leis coesivas triangulares na previs��o no comportamento de juntas adesivas, nomeadamente nas curvas for��adeslocamento (P-���) de ensaios Double-Cantilever Beam para caracteriza����o �� tra����o e ensaios End-Notched Flexure para carateriza����o ao corte. Os ensaios foram simulados numericamente pelo software ABAQUS��, recorrendo ao M��todo de Elementos Finitos (MEF) e um MDC triangular, com o intuito de estimar a lei coesiva de cada um dos adesivos. Para os adesivos Araldite��AV138 e Araldite��2015, �� tra����o e ao corte, a lei triangular previu o comportamento do adesivo com alguma razoabilidade. Para a previs��o da resist��ncia do adesivo SikaForce�� 7752, a lei triangular n��o se ajustou convenientemente nem �� tra����o nem ao corte. Considera-se que, para este adesivo, uma lei trapezoidal �� a que melhor se adequa, devido �� ductilidade do mesmo.

Estudo experimental e num��rico de juntas adesivas em T com aderentes de alum��nio

Nos dias de hoje, a liga����o adesiva de estruturas complexas que n��o poderiam ou n��o seriam t��o f��ceis de ser fabricadas numa s�� pe��a �� cada vez mais usual. As juntas adesivas t��m vindo a substituir muitos outros m��todos de liga����o, como por exemplo liga����es aparafusadas, rebitas ou soldadas, devido ��s vantagens de facilidade na sua fabrica����o, resist��ncia superior e capacidade de unir materiais diferentes. Por esta raz��o as juntas adesivas t��m vindo a ser aplicadas cada vez mais em v��rias industrias como aeroespacial, aeron��utica, autom��vel, naval e cal��ado. O tipo de adesivo a usar em determinada aplica����o �� principalmente escolhido consoante as suas caracter��sticas mec��nicas e o tipo de resposta pretendida ��s solicita����es impostas. Como exemplo de adesivo resistente e fr��gil existe o Araldite�� AV138. Por outro lado, o adesivo Araldite�� 2015 �� menos resistente, mas apresenta maior ductilidade e flexibilidade. Al��m dos adesivos Araldite�� comerciais, existem adesivos de poliuretano que combinam caracter��sticas de elevada resist��ncia com caracter��sticas de grande ductilidade e flexibilidade, como por exemplo o Sikaforce�� 7752. Esta disserta����o tem como objetivo estudar experimentalmente e numericamente, atrav��s de modelos de dano coesivo (MDC), o comportamento de diferentes configura����es de junta em T quando sujeitas a solicita����es de arrancamento. Consideram-se os adesivos anteriormente mencionados para testar as juntas sob diferentes tipos de adesivos. A junta em T �� constitu��da por 2 aderentes em L de alum��nio e um aderente base tamb��m em alum��nio, unidos por uma camada de adesivo. Experimentalmente �� feito um estudo da resist��ncia da junta com a varia����o da espessura dos aderentes em L (tP2). Com a an��lise num��rica s��o estudadas as distribui����es de tens��es, evolu����o do dano, modos de rotura e resist��ncia. Al��m disso, realizou-se um estudo num��rico da exist��ncia ou n��o de adesivo de preenchimento na zona da curvatura dos aderentes em L nas tens��es e na resist��ncia da junta. Mostrouse que a varia����o da geometria nos aderentes em L, a presen��a de adesivo de preenchimento e o tipo de adesivo t��m uma influ��ncia direta na resist��ncia de junta. Os ensaios experimentais validaram os resultados num��ricos e permitiram concluir que os MDC s��o uma t��cnica precisa para o estudo das geometrias das juntas em T.

Modelagem da propaga����o sonora em dutos : abordagem matem��tica no dom��nio da frequ��ncia e do tempo utilizando transformada de laplace

Disserta����o (mestrado)���Universidade de Bras��lia, Faculdade UnB Gama, Faculdade de Tecnologia, Programa de P��s-gradua����o em Integridade de Materiais da Engenharia, 2016.