JOURNALS

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• A methodology for analysis of fluid structure interaction accouting for free surface waves

  E. Oñate, J. García-Espinosa

  (1999). Research Report, Nº PI166

  
  

  Abstract

  A stabilized semi-implicit frictional step finite element method for solving coupled fluid-structure interaction problems involving free surface waves is presented. The stabilized equations are derived at a differential level via a finite element calculus procedure. A new mesh updating technique based on solving a fictitious elastic problem on the moving mesh is described. One example of the efficiency of the stabilized semi-implicit algorithm for the coupled solution of fluid-structure interaction problems is presented.

  Abstract
  A stabilized semi-implicit frictional step finite element method for solving coupled fluid-structure interaction problems involving free surface waves is presented. The stabilized [...]

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• A finite point method for incompressible flow problems

  E. Oñate, C. Sacco, S. Idelsohn

  (1999). Research Report, Nº PI167

  
  

  Abstract

  A stabilized finite point method (FPM) for meshless analysis of incompressible fluid flow problems is presented. The stabilization approach is based in the finite increment calculus (FIC) procedure developed by Oñate. An enhanced fractional step procedure allowing the semi-implicit numerical solution of incompressible fluids using the FPM is described. Examples of application of the stabilized FPM to the solution of two incompressible flow problems are presented.  

  Abstract
  A stabilized finite point method (FPM) for meshless analysis of incompressible fluid flow problems is presented. The stabilization approach is based in the finite increment [...]

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• New rotation free shell triangle for crash-worthiness analysis in parallel PC networks

  E. Oñate, F. Zárate, X. Plana, L. Neamtu

  (1999). Research Report, Nº PI168

  
  

  Abstract

  A new three node shell triangular element with translational degree of freedom as the only modal variables is presented. The element formulation is based on combining a standard linear finite element interpolation with a cell centered finite volume scheme. Details of the implementation of the element in an explicit dynamic code operating in parallel on networks of PC’s are presented. The efficiency and applicability of the new rotation free shell triangle is shown in the solution of some contact/impact and crash-worthiness problem.  

  Abstract
  A new three node shell triangular element with translational degree of freedom as the only modal variables is presented. The element formulation is based on combining a standard [...]

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• Formulación de elementos finitos estabilizada para problemas de transporte convectivo y flujo incompresible mediante técnicas de cálculo finitesimal

  E. Oñate

  (1999). Research Report, Nº PI169

  
  

  Abstract

  El trabajo muestra que los términos de estabilización para la solución por el MEF de problemas de transporte convectivo y de flujo incompresible, pueden obtenerse de manera natural utilizando aproximaciones de mayor orden en las ecuaciones de balance en un dominio finito. Este procedimiento de cálculo finitesimal permite reinterpretar muchos algoritmos de elementos finitos estabilizados utilizando en la práctica y proporciona también una expresión para calcular los parámetros de estabilización.

  Abstract
  El trabajo muestra que los términos de estabilización para la solución por el MEF de problemas de transporte convectivo y de flujo incompresible, pueden [...]

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• EMANT: Programa de análisis de problemas electrotécnicos mediante el método de los elementos finitos

  J. Mora, J. Canet, E. Oñate, C. Sacco, L. Martínez

  (1999). Research Report, Nº PI177

  
  

  Abstract

  La sencillez conceptual de la electrostática esconde todo un abanico de aplicaciones industriales que precisa de herramientas de cálculo numérico para su optimización. En particular, el diseño de aisladores para sistemas de alta tensión o de las cámaras de tratamiento de alimentos implica una cuidadosa elección de la geometría del sistema y materiales empleados. A la ayuda que supone el conocimiento de la distribución de los campos eléctricos asociados a cada prototipo desde el punto de vista de prestaciones del equipo (homogeneidad de campo, minimización de puntos triples), se añade la interesante posibilidad de contribuir a la comprensión del fenómeno físico (cómo se alteran los alimentos al aplicar un campo eléctrico intenso). Se recoge en las siguientes líneas la formulación desarrollada para escribir un código de resolución de problemas electrostáticos mediante el método de los elementos finitos, no tanto como nuevo problema sino como transición desde otras disciplinas como son la mecánica o transferencia de calor.

  Abstract
  La sencillez conceptual de la electrostática esconde todo un abanico de aplicaciones industriales que precisa de herramientas de cálculo numérico para [...]

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• An anisotropic elastoplastic constitutive model for large deformation analysis of fibre reinforced composites

  E. Car, S. Oller, E. Oñate

  (1999). Research Report, Nº PI178

  
  

  Abstract

  In this work a generalized anisotropic elastoplastic constitutive model in large deformation is presented. It is used for the analysis of fiber-reinforced composite materials in the frame of the finite element method. Mixing theory is applied to simulate the behavior of the composite material.  The elastic anisotropic behavior  is simulated with classical elasticity theory, while that of a non-proportional anisotropic solid is simulated by means of the proposed generalized anisotropic elastoplastic model. The  approach assumes the existence of a real anisotropic space and of a fictitious isotropic space where a mapped fictitious problem is solved. Both spaces are related by means of a linear transformation using a fourth order  tensor incorporating complete information on the real anisotropic material. Details of the numerical implementations of the model into a non-linear, large deformations finite element solution scheme are provided. Examples of application showing the performance of the model for the analysis of fiber-reinforced composite materials are given.

  Abstract
  In this work a generalized anisotropic elastoplastic constitutive model in large deformation is presented. It is used for the analysis of fiber-reinforced composite [...]

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• Numerical aerodynamic analysis of large buildings using a finite element model with application to a telescope building

  R. Codina, C. Morton, E. Oñate, O. Soto

  (1999). Research Report, Nº PI181

  
  

  Abstract

  Presents a numerical strategy for the aerodynamic analysis of large buildings, with an application to the simulation of the air flow within a telescope building. The finite element formulation is presented first, and then the methodology followed to obtain significant data from the calculations is described. The quality of the ventilation of the building is defined by the average residence times, and the feasibility of this ventilation by the actions created on the instruments and the general flow pattern.

  Abstract
  Presents a numerical strategy for the aerodynamic analysis of large buildings, with an application to the simulation of the air flow within a telescope building. The finite [...]

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• A finite element method for fluid-structure interaction with surface waves using a finite calculus formulation

  E. Oñate, J. García-Espinosa

  (2000). Research Report, Nº PI180

  
  

  Abstract

  A stabilized semi-implicit step finite element method for solving coupled fluid-structure interaction problems involving free surface waves is presented. The stabilized governing equations for the viscous fluid and the free surface are derived at a differential level via finite increment calculus procedure. A mesh updating technique based on solving a fictitious elastic problem on the moving mesh is described. Examples of the efficiency of the stabilized semi-implicit algorithm for the analysis of fluid-structure interaction problems in totally or partially submerged bodies is presented.  

  Abstract
  A stabilized semi-implicit step finite element method for solving coupled fluid-structure interaction problems involving free surface waves is presented. The stabilized governing [...]

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• Stabilization techniques for finite element analysis of convection-diffusion problems

  E. Oñate, M. Manzan

  (2000). Research Report, Nº PI183

  
  

  Abstract

  The accurate solution of convection type problems on practical grids has been ever a challenging issue, and invariably some sort of stabilization is needed in order to get a physical solution. This has pushed researchers to develop various stabilization algorithms used in every day practice by numerical analysts. In this chapter some methods are presented along with a new finite increment calculus approach to obtain the different algorithms using higher order conservation equations.

  Abstract
  The accurate solution of convection type problems on practical grids has been ever a challenging issue, and invariably some sort of stabilization is needed in order to get [...]

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• The Monte Carlo method. Application to the stochastic analysis of sheet stamping processes

  J. Hurtado, F. Zárate, E. Oñate

  (2000). Research Report, Nº PI184

  
  

  Abstract

  Stochastic Mechanics is a rapidly growing area of research, whose importance is being recognized not only in academic circles but also in industrial practice. This is no doubt due to the fact that most structural properties and loads are either random or uncertain. The first term refers to a natural chaotic variation of the parameter, while the second is associated to the human lack of knowledge about it. Both kinds of unpredictability work together in rendering doubtful the results of a (usually single) deterministic mechanical analysis. When thinking about the randomness and uncertainty linked to all physical parameters and phenomena a big question mark closes the large list of numbers produced by a finite element calculation. In Stochastic Mechanics there are several techniques to analyse the natural scatter of strains and stresses caused by the dispersion in the given loads and/or the structural parameters. The most general one is the Monte Carlo method. However, it must be recognized that is as well the most costly in computational terms. Nevertheless, this cost has becoming feasible with the advance in Computer Science, specially with the advent of parallel computing, due to the fact that a Monte Carlo calculation is intrinsically a task that can be performed in parallel. The present report is intended to provide the reader an introduction to the Monte Carlo method in the context of Computational Mechanics. The technique is applied to the analysis of the uncertainty spread in a stamping process. The first chapter summarises the Monte Carlo method and its theoretical backgrounds. The second chapter is devoted to the case study, namely, the stochastic analysis of a square cup deep drawing problem. Finally, the basic equations governing the mechanical modelling of the stamping process are summarized in the appendix.

  Abstract
  Stochastic Mechanics is a rapidly growing area of research, whose importance is being recognized not only in academic circles but also in industrial practice. This is no doubt [...]

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