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• A large strain plasticity model for anisotropic materials - composite material application

  E. Car, S. Oller, E. Oñate

  International Journal of Plasticity (2001). Vol. 17 (11), pp. 1437-1463

  
  

  Abstract

  In this work a generalized anisotropic model in large strains based on the classical isotropic plasticity theory is presented. The anisotropic theory is based on the concept of mapped tensors from the anisotropic real space to the isotropic fictitious one. In classical orthotropy theories it is necessary to use a special constitutive law for each material. The proposed theory is a generalization of classical theories and allows the use of models and algorithms developed for isotropic materials. It is based on establishing a one-to-one relationship between the behavior of an anisotropic real material and that of an isotropic fictitious one. Therefore, the problem is solved in the isotropic fictious space and the results are transported to the real field. This theory is applied to simulate the behavior of each material in the composite. The whole behavior of the composite is modeled by incorporating the anisotropic model within a model based on a modified mixing theory.

  Abstract
  In this work a generalized anisotropic model in large strains based on the classical isotropic plasticity theory is presented. The anisotropic theory is based on the concept [...]

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• Optimización de embarcaciones de recreo mediante la utilización de un código CFD

  M. López-Rodríguez, J. García-Espinosa, E. Oñate

  Ingeniería Naval (2001). Vol. 784, pp. 122-130

  
  

  Abstract

  En la actualidad las más avanzadas técnicas para diseño naval ya no se restringen sólo a proyectos de alto coste; si no que también ahora son de aplicación en el campo de las embarcaciones de recreo y turísticas, dando con ello un valor añadido al proyecto final. La utilización de un código CFD para el mayor conocimiento del comportamiento hidrodinámico de las embarcaciones de recreo y turísticas es de una gran utilidad debido a las complejidades que en el diseño de estas se presentan. Estas herramientas nos van a proporcionar una serie de datos como sustentación lateral en las embarcaciones de vela o interacción entre cascos en catamaranes con deriva lateral, que de otra forma nunca pudieran conocerse. Los resultados hidrodinámicos obtenidos nos sirven para comparar las diferentes alternativas, y para además obtener unos valores que directamente son usados para la predicción de velocidad de la embarcación, que más tarde se verán refrendadas por las pruebas de mar. La utilización de técnicas CFD, basadas en el método de los elementos finitos, para la resolución de las ecuaciones de Reynolds (RANSE), incluyendo efectos de superficie libre, hace que todo esto sea posible. En este trabajo se presentan diversos resultados de aplicación del código CFD SHYNE a varias embarcaciones deportivas y de recreo. SHYNE está basado en la técnica del Cálculo Finitesimal para la integración de las ecuaciones de Reynolds.

  Abstract
  En la actualidad las más avanzadas técnicas para diseño naval ya no se restringen sólo a proyectos de alto coste; si no que también ahora [...]

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• ED-Elas2D: An Educational Program for Computer-aided Training in Structural Analysis Using the Finite Element Method

  B. Suarez, E. Blanco, L. Gil, P. Zapata, E. Oñate

  European Journal of Engineering Education (1998). Vol. 23 (2), pp. 243-254

  
  

  Abstract

  In this paper, a methodology for computer-aided training of structural problems by the finite element method is presented. The resulting educational program, named ED-Elas2D, has been developed by a group of researchers at the School of Civil Engineering at the Technical University of Catalonia (UPC) in Barcelona, UPC. The program combines the standard concept which appears in the traditional teaching of finite element methods for structural analysis, such as the introduction to the basic structural theory, data definition (pre-processor), description of the analysis procedure (processor) and interpretation of results (post-processor). The program is addressed to both students who enrol in the study on finite element methods and to academic and technical staff in universities and companies who wish to update their knowledge of finite element techniques. The educational program ED-Elas2D works in the Windows system and it is characterized by its interactivity and graphic utilities.

  Abstract
  In this paper, a methodology for computer-aided training of structural problems by the finite element method is presented. The resulting educational program, named ED-Elas2D, [...]

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• A finite element model for thermomechanical analysis in casting processes

  D. Celentano, S. Oller, E. Oñate

  Journal of Physique IV (1993). Vol. 3 (C7), pp. 1171-1180

  
  

  Abstract

  This paper summarizes the recent work of the authors in the numerical simulation of casting processes. In particular, a coupled thermomechanical model to simulate the solidification problem in casting has been developed [7,8,9]. The model, based on a general isotropic thermoelasto-plasticity theory and formulated in a macroscopical point of view, includes generalized phase-change effects and considers the different thermomechanical behaviour of the solidifying material during its evolution from liquid to solid. For this purpose, a phase-change variable, plastic evolution equations and a temperature-dependent material constitutive law have been defined. Some relevant aspects of this model are presented here. Full thermomechanical coupling terms have been considered as well as variable thermal and mechanical boundary conditions : the first are due to air gap formation, while the second involve a contact formulation. Particular details concerning the numerical implementation of this model are also mentioned. An enhanced staggered scheme, used to solve the highly non-linear fully coupled finite element equations, is proposed. Furthermore, a proper convergence criterion to stop the iteration process is adopted and, although the quadratic convergence of Newton-Rapshon's method is not achieved, several numerical experiments demonstrate reasonable convergence rates [9]. Finally, an experimental cylindrical casting test problem, including phase-change phenomena, temperature-dependent constitutive properties and contact effects, is analyzed. Numerical results are compared with some laboratory measurements.

  Abstract
  This paper summarizes the recent work of the authors in the numerical simulation of casting processes. In particular, a coupled thermomechanical model to simulate the solidification [...]

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• Análisis no lineal de tanques criogénicos bajo cargas térmicas

  J. Oliver, E. Oñate, J. Peraire, R. Chueca

  Hormigón y Acero (1985). Vol. 155, pp. 99-123

  
  

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• La formulación del flujo viscoplástico y sus diversas aplicaciones prácticas por el método de los elementos finitos

  E. Oñate

  Revista de Obras Públicas (1980). Vol. 127 (3178), pp. 115-129

  
  

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• Diseño óptimo de vasijas de presión usando el método de los elementos finitos y un optimizador no lineal

  J. Middleton, E. Oñate

  ETSIIT (1977). Vol. 11, pp. 309-325

  
  

  Abstract

  Se presenta un esquema de diseño para vasijas de presión metálicas de manera que se minimice la tensión tangencial en la vasija . La geometría final se establece mediante un procedimiento iterativo que optimiza un modelo matemático que expresa la  variación de la tensión tangencial en la vasija. Los parámetros del modelo se calculan para cada interacción a partir de los valores de las tensiones tangenciales en la vasija, determinados por el método de los elementos finitos.

  Abstract
  Se presenta un esquema de diseño para vasijas de presión metálicas de manera que se minimice la tensión tangencial en la vasija . La geometría [...]

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• Efficient aeroelastic analysis of inflatable structures using enhanced potential flow aerodynamics

  E. Ortega, R. Flores, E. Cuartero, E. Oñate

  Journal of Fluids and Structures (2019). Vol. 90, pp. 230-245

  
  

  Abstract

  An efficient method for the aeroelastic analysis of wind effects on inflatable structures is presented. The solution scheme is staggered and uses an explicit finite-element structural solver and potential flow aerodynamics. In order to take into account the essential features of the flow around blunt-shaped structures, a physics-based correction of the inviscid solution is proposed. The procedure involves automatic prediction of the detached flow areas (using Stratford’s criterion) and an empirical modification of the calculated pressure field intended to match the real viscous behavior. Several validation benchmarks and a realistic application example are presented. The results show the capability of the model to predict the wind loads on the structure with sufficient accuracy and low computational cost, making it possible to use aeroelastic analysis for routine calculation of inflatable structures.

  Abstract
  An efficient method for the aeroelastic analysis of wind effects on inflatable structures is presented. The solution scheme is staggered and uses an explicit finite-element [...]

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• Cimne & Complas 30 Years - 1987 - 2017

  E. Oñate

  Videos of Plenary Lectures presented at the XIV International Conference on Computational Plasticity (COMPLAS 2017).

  
  

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• Posibilidades de los ordenadores personales en el cálculo de estructuras por el método de los elementos finitos

  E. Oñate, Á. Gaona, J. Oliver, B. Suarez

  Revista de Obras Públicas (1983). Vol. 130 (3212), pp. 231-248

  
  

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