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• Modelo constitutivo elastoplástico anisótropo en deformaciones finitas para análisis de materiales compuestos reforzados con fibras

  E. Car, S. Oller, E. Oñate

  (1998). Research Report, Nº PI139

  
  

  Abstract

  En este trabajo se presenta un modelo constitutivo elastoplástico anisótropo generalizado en deformaciones finitas para el análisis de materiales compuestos multifase utilizando el método de los elementos finitos. En la modelización del material compuesto se utiliza la teoría de mezclas en la cual se inserta el modelo constitutivo elastoplástico propuesto. El comportamiento elástico de un sólido anisótropo se simula con la teoría de la elasticidad clásica, mientras que el comportamiento no proporcional de un sólido anisótropo se simula mediante un modelo elastroplástico anisótropo en régimen de grandes deformaciones basado en una formulación isótropa equivalente. Este modelo asume la existencia de un espacio real anisótropo y de un espacio ficticio isótropo, en el cual se resuelve un problema ficticio. Ambos espacios están relacionados a través de una transformación lineal utilizando un tensor de cuarto orden que contiene la información del material real. Por último se presenta los detalles de la implementación numérica del modelo propuesto en un código de elementos finitos y ejemplos de aplicación del modelo al análisis del comportamiento lineal y no-lineal de materiales compuestos.  

  Abstract
  En este trabajo se presenta un modelo constitutivo elastoplástico anisótropo generalizado en deformaciones finitas para el análisis de materiales compuestos [...]

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• Numerical differentiation for local and global tangent operators in computational plasticity

  G. Chiandussi, G. Bugeda, E. Oñate

  (1998). Research Report, Nº PI144

  
  

  Abstract

  A simple method to automatically update the finite element mesh of the analysis domain is proposed. The method considers the mesh as a fictitious elastic body subjected to prescribed displacements at selected boundary points. The mechanical properties of each mesh element are appropriately selected in order to minimize the deformation and the distortion of the mesh elements. Different selection strategies have been used and compared in their application to simple examples. The method avoids the use of remeshing in the solution of shape optimization problems and reduces the number of remeshing steps in the solution of coupled fluid–structure interaction problems.

  Abstract
  A simple method to automatically update the finite element mesh of the analysis domain is proposed. The method considers the mesh as a fictitious elastic body subjected to [...]

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• A simple method for automatic update of finite element meshes

  G. Chiandussi, G. Bugeda, E. Oñate

  (1998). Research Report, Nº PI147

  
  

  Abstract

  A simple method to automatically update the finite element mesh of the analysis domain is proposed. The method considers the mesh as a fictitious elastic body subjected to prescribed displacements at selected boundary points. The mechanical properties of each mesh element are appropriately selected in order to minimize the deformation and the distortion of the mesh elements. Different selection strategies have been used and compared in their application to simple examples. The method avoids the use of remeshing in the solution of shape optimization problems and reduces the number of remeshing steps in the solution of coupled fluid–structure interaction problems

  Abstract
  A simple method to automatically update the finite element mesh of the analysis domain is proposed. The method considers the mesh as a fictitious elastic body subjected to [...]

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• Rotation‐free triangular plate and shell elements

  E. Oñate, F. Zárate

  (1999). Research Report, Nº PI149

  
  

  Abstract

  The paper describes how the finite element method and the finite volume method can be successfully combined to derive two new families of thin plate and shell triangles with translational degrees of freedom as the only nodal variables. The simplest elements of the two families based on combining a linear interpolation of displacements with cell centred and cell vertex finite volume schemes are presented in detail. Examples of the good performance of the new rotation‐free plate and shell triangles are given.

  Abstract
  The paper describes how the finite element method and the finite volume method can be successfully combined to derive two new families of thin plate and shell triangles with [...]

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• A stabilized finite element method for incompressible viscous flows using a finite increment calculus formulation

  E. Oñate

  (1999). Research Report, Nº PI150

  
  

  Abstract

  A stabilized finite element formulation for incompressible viscous flows is derived. The starting point are the modified Navier-Stokes equations incorporating naturally the necessary stabilization terms via a finite increment calculus (FIC) procedure. Application of the standard finite element Galerkin method to the modified differential equations leads to a stabilized discrete system of equations overcoming the numerical instabilities emanating from the advective terms and those due to the lack of compatibility between approximate velocity and pressure fields. The FIC method also provides a natural explanation for the stabilization terms appearing in all equations for both the Navier-Stokes and the simpler Stokes equations. Transient solution schemes with enhanced stabilization properties are also proposed. Finally a procedure for computing the stabilization parameters is presented.

  Abstract
  A stabilized finite element formulation for incompressible viscous flows is derived. The starting point are the modified Navier-Stokes equations incorporating naturally the [...]

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• New degrees of freedom in computational mechanics: mesh free finite point method, rotation free shell triangles and moving free meshes

  E. Oñate

  (1999). Research Report, Nº PI154

  
  

  Abstract

  The paper presents an overview of some recent developments in computational mechanics introducing new degrees of “freedom” allowing the solution of more challenging problems. First advances in the finite point method for fully mesh free solution in fluid and solid mechanics are described. Next, new rotation free shell triangles incorporating membrane and bending effects are presented. Finally, a simple method allowing free movement of meshes is described. Examples of application of all the “free” methods are given.  

  Abstract
  The paper presents an overview of some recent developments in computational mechanics introducing new degrees of “freedom” allowing the solution of more challenging [...]

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• Advances in the stabilized finite point method for structural mechanics

  E. Oñate, F. Perazzo, J. Canet

  (1999). Research Report, Nº PI164

  
  

  Abstract

  The basis of the finite point method for the fully meshless solution of structure mechanics problems is described. A new stabilization technique based on a finite increment calculus procedure is used. The efficiency and accuracy of the stabilized finite point method in the meshless analysis of simple structural problems is shown in two examples of applications.

  Abstract
  The basis of the finite point method for the fully meshless solution of structure mechanics problems is described. A new stabilization technique based on a finite increment [...]

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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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