EE - Escola de Engenharia
URI permanente desta comunidadehttps://rihomolog.furg.br/handle/1/512
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- ItemModelagem numérica do campo de temperatura em uma junta soldada utilizando fonte de calor volumétrica(2016) Machado, Thiago da Silva; Cunda, Luiz Antônio Bragança daA utilização dos métodos numéricos para avaliar o comportamento dos fenômenos envolvidos nos processos de soldagem tem se tornado uma forte ferramenta na área da fabricação mecânica. Apesar da complexidade desses fenômenos, os modelos computacionais atuais permitem uma ótima aproximação de resultados quando comparados a resultados experimentais. O método dos elementos finitos é a técnica mais comum utilizada para análises envolvendo processos de soldagem, que por sua vez, acoplam os efeitos térmicos, mecânicos e metalúrgicos simultaneamente. Apesar da importância da análise simultânea desses fenômenos, de modo geral, não há uma dependência entre a análise térmica, que apresenta modelos numéricos baseados nas equações da transferência de calor, e a análise estrutural. Sendo assim, as análises podem ser realizadas em sequência sem a necessidade de acoplamento. Este trabalho tem por objetivo a modelagem do campo de temperaturas em uma junta soldada utilizando fonte de calor volumétrica. No presente trabalho são apresentadas simulações numéricas de uma junta de topo, com chanfro em V, de chapas de aço AISI 304L soldadas pelo processo GMAW. As simulações foram realizadas no software ABAQUS Simulia®, onde se movimentou uma fonte de calor volumétrica através de uma chapa medindo 200 mm de comprimento, 50 mm de largura e 9,5 mm de espessura. Para fins de validação do modelo térmico proposto, foi realizado um estudo comparativo com os resultados numéricos e experimentais obtidos pelo Laboratório de Pesquisa em Engenharia da Soldagem da Universidade Federal do Rio Grande durante a execução do projeto PRONEM/FAPERGS. Neste comparativo comprovou-se a eficiência da aplicação da fonte de calor volumétrica para solução de problemas envolvendo processos de soldagem. No intuito de melhorar os resultados obtidos, foram propostas variações nos parâmetros geométricos da fonte de calor volumétrica.
- ItemImplementação do modelo de Drucker-Prager exponencial para simulação de juntas adesivas(2023) Follmann, Carlos Eduardo; Bianchi, Kleber EduardoAs juntas adesivas vêm recebendo enfoque cada vez maior na indústria. Porém o projeto destas uniões demanda o conhecimento acerca de seu comportamento mecânico, condição necessária para a modelagem numérica por elementos finitos. Cada um dos vários modelos de análise numérica requer um conjunto de parâmetros que caracterizam os materiais empregados na junta. Neste trabalho foi empregado o modelo de Drucker-Prager exponencial, o qual faz parte das ferramentas disponíveis no software Abaqus. Os parâmetros requeridos pelo modelo foram obtidos a partir de dois ensaios experimentais normatizados, de tração e de cisalhamento. Os resultados dos ensaios mecânicos revelaram um comportamento dúctil do adesivo LORD® 852. Já as análises numéricas geraram resultados conservadores.
- ItemProbabilistic analysis of reinforced concrete columns(2001) Araújo, José Milton deThe subject of this work is the probabilistic finite element analysis of reinforced concrete columns. Concrete properties are represented as homogeneous Gaussian random fields. The yield stress and position of steel reinforcement, dimensions of the column cross-section and axial load are considered as random variables. The Monte Carlo method is employed to obtain expected values and standard deviations of the rupture load. The partial safety factors method is used for columns design and structural safety is evaluated by means of the reliability index, which is obtained through simulations. The effects of main parameters on the reliability index are investigated. It is shown that the correlation length of random fields for concrete properties may have a significant effect on reliability. Therefore, simplified procedures, which do not consider spatial variations of concrete properties are inappropriate for safety analysis.
- ItemStrength properties of porous media by means of a non-linear elastic approach(2009) Maghous, Samir; Pasquali, Paulo Roberto Zanella; Santos, Leonardo Costa dos; Cunda, Luiz Antonio Bragança daThe present paper describes a formulation of macroscopic strength properties of porous media relying on the simulation of the regime o plastic flow of the solid matrix by means of an appropriate fictitious non-linear elastic law. Explicit expression for the latter is derived in the particular case of a frictional solid matrix characterized by a Drucker-Prager yield condition. The approach is thus implemented in a numerical procedure specifically devised for evaluating the yield stresses of a porous medium. The finite element solutions are therefore compared to micromechanics-based analytical expression previously developed for the yield function. The last part of the paper is devoted to the formulation of phenomenological yield function for porous media with frictional solid matrix by combining the micromechanics-based approach and fitting the finite element results.
- ItemSimulação numérica da ação de ondas sobre um dispositivo de captação de energias das ondas do tipo coluna de água oscilante(2011) Davyt, Djavan Perez; Teixeira, Paulo Roberto de Freitas; Ramalhais, Rúben dos Santos; Didier, Eric LionelNeste trabalho é analisado um dispositivo de extração de energia das ondas do tipo coluna de água oscilante sob a ação de ondas regulares de diferentes períodos. São realizadas variações no comprimento submerso da parede frontal e no comprimento da câmara. Para tal é utilizado o código numérico FLUINCO, o qual é baseado nas equações RANS e a discretização é realizada utilizando o método semi-implícito de Taylor-Galerkin de dois passos. Uma formulação lagrangeana-euleriana arbitrária (ALE) é utilizada para permitir a solução de problemas que envolvem movimentos da superfície livre. Alguns resultados são comparados com os obtidos utilizando o programa FLUENT. São apresentados a amplificação (relação entre a altura da onda incidente a e dentro da câmara), distribuição das velocidades e vetores de velocidade.
- ItemNumerical simulations of low reynolds number flows past elastically mounted cylinder(2012) Gonçalves, Rafael Almeida; Teixeira, Paulo Roberto de Freitas; Didier, Eric LionelThe vortex-induced vibration (VIV) phenomenon has drawn the attention of researchers in Engineering for several decades. An example is the riser used for petroleum exploration, in which it is subjected to marine flows that may cause oscillations due to vortex shedding. In this paper, numerical analyses of the phenomena that occur in the interaction among flows at low Reynolds numbers and elastically mounted cylinders are presented. The simulation is carried out by using the numerical model Ifeinco that uses a semi-implicit two-step Taylor-Galerkin method to discretize the Navier-Stokes equations and the arbitrary Lagrangean-Eulerian formulation to follow the cylinder motion. The rigid body motion description is calculated by using the Newmark method. Firstly, the characteristics of the vortex generation process for the fixed cylinder are analyzed. In this case, the Strouhal number, the mean drag and the RMS lift coefficients for Reynolds numbers ranging from 90 to 140 are shown. Afterwards, an analysis of a flexible supported cylinder (with a spring and a damper) in transverse direction subject to flows with Reynolds numbers ranging from 90 to 140 is carried out. The cylinder displacement and the vibration frequencies are studied; the synchronization between the vortex shedding and the vibration frequency (lock-in) is analyzed. Similar results to the experimental ones developed by Anagnostopoulos and Bearman (1992) were obtained in this study.
- ItemNumerical simulation of the interaction of a regular wave and a submerged cylinder(2009) Teixeira, Paulo Roberto de FreitasA numerical simulation of the interaction between a regular wave and an immersed horizontal cylinder, whose axis is 3-radius deep, perpendicular to the direction of the wave propagation, is presented in this paper. The numerical model uses the semi-implicit two-step Taylor- Galerkin method to integrate Navier-Stokes equations in time and space. Arbitrary lagrangean-eulerian formulation is employed to describe the free surface movement. The free surface elevations near the cylinder and in some gauges along the channel, as well the spectrum distribution, are compared with experimental ones, and good agreement is obtained. The analysis shows that the viscous effects only affect the area that is very close to the cylinder.
- ItemNumerical simulation of an oscillating water column device using a code based on Navier-Stokes equations(2013) Teixeira, Paulo Roberto de Freitas; Davyt, Djavan Perez; Didier, Eric Lionel; Ramalhais, Rúben dos SantosThe study of ways of converting ocean wave energy into a useful one and the improvement of the existing equipment are complex engineering problems and very important issues in today’s society. In this paper, the onshore oscillating water column device, in a 10 m deep channel subjected to 1 m high incident wave and wave periods from 4 s to 15 s, is investigated. The numerical analyses are carried out using Fluinco model that deals with incompressible flow problems based on the Navier-Stokes equations and employs the two-step semi-implicit Taylor-Galerkin method. An aerodynamic model is implemented in the algorithm to determine the air pressure that is imposed on the free surface. Analyses are divided into two sections. In the first section, the flow variables obtained by Fluinco and the commercial model Fluent are compared and similar results are obtained. In the second section, an investigation of the chamber geometry and turbine characteristic relation that provide the best device performance is carried out. In this case, variations in the front wall depth, the chamber length, the turbine characteristic relation and the chamber height, are made.
- ItemNumerical analysis of regular waves over an onshore oscillating water column(2010) Davyt, Djavan Perez; Teixeira, Paulo Roberto de Freitas; Ramalhais, Rúben dos Santos; Didier, Eric LionelThe potential of wave energy along coastal areas is a particularly attractive option in regions of high latitude, such as the coasts of northern Europe, North America, New Zealand, Chile and Argentina where high densities of annual average wave energy are found (typically between 40 and 100 kW/m of wave front). Power estimated in the south of Brazil is 30kW/m, creating a possible alternative of source energy in the region. There are many types and designs of equipment to capture energy from waves under analysis, such as the oscillating water column type (OWC) which has been one of the first to be developed and installed at sea. Despite being one of the most analyzed wave energy converter devices, there are few case studies using numerical simulation. In this context, the numerical analysis of regular waves over an onshore OWC is the main objective of this paper. The numerical models FLUINCO and FLUENT® are used for achieving this goal. The FLUINCO model is based on RANS equations which are discretized using the two-step semi-implicit Taylor-Galerkin method. An arbitrary lagrangean eulerian formulation is used to enable the solution of problems involving free surface movements. The FLUENT® code (version 6.3.26) is based on the finite volume method to solve RANS equations. Volume of Fluid method (VOF) is used for modeling free surface flows. Time integration is achieved by a second order implicit scheme, momentum equations are discretized using MUSCL scheme and HRIC (High Resolution Interface Capturing) scheme is used for convective term of VOF transport equation. The case study consists of a 10.m deep channel with a 10 m wide chamber at its end. One meter high waves with different periods are simulated. Comparisons between FLUINCO and FLUENT results are presented. Free surface elevation inside the chamber; velocity distribution and streamlines; amplification factor (relation between wave height inside the chamber and incident wave height); phase angle (angular difference between the wave inside and outside the chamber); and sloshing parameter to quantify it inside the chamber are analised. Finally, a discussion of the potential and limitations of each numerical model as well as the behaviour of the onshore OWC device is presented.
- ItemLinear static and dynamic analysis of thin laminated composite structures with a triangular finite element(2010) Isoldi, Liércio André; Awruch, Armando Miguel; Morsch, Inácio Benvegnu; Teixeira, Paulo Roberto de FreitasLinear static and dynamic behavior of thin laminate composite structures are analyzed in this study using the Finite Element Method (FEM). Triangular elements with three nodes and six degrees of freedom per node (three displacement and three rotation components) are used. For static analysis the equilibrium equations are solved using Pre-conditioned Gradient Conjugate Method (GCM) while the dynamic solution is performed using the classical Newmark Method. Analytical evaluation of consistent element mass matrix and determination of membrane and membrane-bending coupling element stiffness matrix in the explicit form are showed. Numerical examples are presented and compared with results obtained by other authors with different types of elements and different schemes, proving the validity and effectiveness of the developed model.