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• Derivation of the secant stiffness matrix for non linear finite element analysis of solids and trusses

  E. Oñate

  (1994). Research Report, Nº PI49

  
  

  Abstract

  In this paper the general non symmetric parametric form of the incremental secant stiffness matrix for nonlinear analysis of solids using the finite element method is derived. A convenient symmetric expression for a particular value of the parameters is obtained. The geometrically nonlinear formulation is based on a Generalized Lagrangian approach. Detailed expressions of all the relevant matrices involved in the analysis 3D solids are obtained. The possibilities of application of the secant stiffness matrix for nonlinear structural problems including stability, bifurcation and limit load analysis are also discussed. Examples of application are given for the nonlinear analysis of pin joined frames.  

  Abstract
  In this paper the general non symmetric parametric form of the incremental secant stiffness matrix for nonlinear analysis of solids using the finite element method is derived. [...]

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• 3D finite element computations for viscous aerodynamic flows around automobiles

  T. Fischer, J. Canet, O. Fruitos, E. Oñate

  (1994). Research Report, Nº PI50

  
  

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• Petrov-Galerkin methods for the transient advective-diffusive equation with sharp gradients

  S. Idelsohn, J. Heinrich, E. Oñate

  (1994). Research Report, Nº PI51

  
  

  Abstract

  A Petrov–Galerkin formulation based on two different perturbations to the weighting functions is presented. These perturbations stabilize the oscillations that are normally exhibited by the numerical solution of the transient advective–diffusive equation in the vicinity of sharp gradients produced by transient loads and boundary layers. The formulation may be written as a generalization of the Galerkin Least‐Square method.

  Abstract
  A Petrov–Galerkin formulation based on two different perturbations to the weighting functions is presented. These perturbations stabilize the oscillations that are normally [...]

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• A review of some finite element families for thick and thin plate and shell analysis

  E. Oñate

  (1994). Research Report, Nº PI53

  
  

  Abstract

  This paper describes a number of triangular and quadrilateral plate and Shell elements derived via Reissner-Mindlin plate theory and mixed interpolation. It shown how by introducing the adequate constrains the original thick plate element evolve into DK forms adequate for this situations only. This evolution process allows to revisite some classical elements like the Morley triangle and also to derive simple plate and shell triangles and quadrilates with only translational degrees of freedom as nodal variables.

  Abstract
  This paper describes a number of triangular and quadrilateral plate and Shell elements derived via Reissner-Mindlin plate theory and mixed interpolation. It shown how by introducing [...]

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• Adaptive finite element computations of hypersonic inviscid flows around a double ellipsoid.

  T. Fischer, E. Oñate

  (1995). Research Report, Nº PI60

  
  

  Abstract

  This report documents the potential capabilities of adaptive inviscid flow calculations on unstructured meshes in three dimensions using the finite element method. The finite element formulation of the compressible Euler and Navier-Stokes equations is based on a two-step explicit Taylor-Galerkin scheme. Adaptive remeshing is applied to enhance the numerical solution in the vicinity the shocks. Particular emphasis is put on the generation of unstructured tetrahedral meshes as well as in the discussion of estimating the error in the numerical solution. Finally, an application to a well-known 3D high speed flow problem is shown where adaptive remeshing techniques become essential to keep the computational cost within reasonable limits. Its results are compared to some seemingly best reference solutions using other algorithms.    

  Abstract
  This report documents the potential capabilities of adaptive inviscid flow calculations on unstructured meshes in three dimensions using the finite element method. The finite [...]

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• PARAMESH. Two dimensional unstructured parallel mesh generation program

  J. Mestres, E. Oñate, G. Bugeda

  (1995). Research Report, Nº PI61

  
  

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• Finite point methods in computational mechanics

  E. Oñate, S. Idelsohn, O. Zienkiewicz

  (1995). Research Report, Nº PI67

  
  

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• Simulación del choque de vehículos por el método de los elementos finitos. Programa "SIMPACT"

  J. Rojek, E. Oñate, J. Canet

  (1995). Research Report, Nº PI71

  
  

  Abstract

  En este trabajo se presentan las principales características del programa de ordenador “SIMPACT” desarrollado en el Centro Internacional de Métodos Numéricos en Ingeniería de Barcelona para la simulación numérica de problemas de impacto y choque de vehículos. El programa se basa en una formulación de elementos finitos de lámina no lineal incorporando también elementos de sólido y de viga para modelar correctamente todos los componentes resistente típicos de estructuras de vehículos. El programa permite la utilización de algoritmos de integración en el tiempo explícitos incluyendo además modelos constitutivos para materiales compuestos. Los ejemplos que se presentan muestran la aplicación del programa a la deformación de una puerta sometida a un ensayo penetración lateral, el choque frontal de un prototipo de vehículo industrial, y el vuelco de una cabina de autobús.

  Abstract
  En este trabajo se presentan las principales características del programa de ordenador “SIMPACT” desarrollado en el Centro Internacional de Métodos [...]

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• Análisis de procesos de conformado de metales por el método de los elementos finitos. Posibilidades y perspectivas.

  E. Oñate

  (1995). Research Report, Nº PI72

  
  

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• Structural analysis and durability assessment of historical construction using a finite element damage model

  E. Oñate, A. Hanganu, A. Barbat, S. Oller, R. Vitaliani, A. Saetta, R. Scotta

  (1995). Research Report, Nº PI73

  
  

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