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• Structural analysis and durability assesment of historical constructions using a finite element damage model

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

  (1997). Structural Analysis of Historical Constructions I, P. Roca, J.L. González, A.R. Marí and E. Oñate (Eds.), CIMNE, Barcelona, Spain

  
  

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• Prediction of elastic springback deffects in sheet stamping processes using finite element methods

  E. Oñate, J. Rojek

  (1997). Advanced Methods in Materials Processing Defects, Elsevier

  
  

  Abstract

  Undesiderable spring-back induced deformations are one of the cause for rejection of many stamped sheet parts. The paper presents the alternatives for predicting spring-back defects in the context of the most popular finite element (FE) formulations based on rigid-plastic and elasto-plastic material models, quasistatic (implicit) and explicit dynamic algorithms. Examples showing the possibilities and efficiency of the different FE procedures are also given.

  Abstract
  Undesiderable spring-back induced deformations are one of the cause for rejection of many stamped sheet parts. The paper presents the alternatives for predicting spring-back [...]

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• Numerical modelling of sheet metal forming problems

  E. Oñate, C. Agelet de Saracibar

  (1991). Numerical Modelling of Material Deformations Processes, C. Sturgess et al (Eds.), Springer Verlag, London

  
  

  Abstract

  Stamping of sheet-metal parts by means of punches and dies is a standard manufacturing process. However, despite its broad application in industry, the design of forming processes is still largely based on experimental techniques, such as the use of circular grid systems (Keeler 1968) or forming limit diagrams (Hecker 1973, Keeler 1974).

  Abstract
  Stamping of sheet-metal parts by means of punches and dies is a standard manufacturing process. However, despite its broad application in industry, the design of forming processes [...]

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• Finite Streifenmethode für Mindlinsche Platten und axialsymmetrische Schalen

  E. Oñate, B. Suárez, E. Hinton

  (1990). Finite Elemente Programme für Platten und Schalen, Springer-Verlag, Berlin, Germany

  
  

  Abstract

  Viele Konstruktionen besitzen konstante geometrische Eigenschaften entlang einer bestimmten Richtung. Derartige prismatische Strukturen sind bei Platten weit verbreitet, bei denen der Querschnitt der Platte in Längsrichtung oft konstant bleibt. Bei axialsymmetrischen Schalen bleibt der Querschnitt der Schale in Umfangsrichtung ebenfalls konstant (siehe Bild 2.1). Falls die Materialeigenschaften der Struktur ebenfalls in der gleichen Richtung konstant sind, kann die Berechnung durch eine Kombination der Methode der finiten Elemente und Fourierreihenentwicklung vereinfacht werden, um das transversale und longitudinale Verhalten zu erfassen.

  Abstract
  Viele Konstruktionen besitzen konstante geometrische Eigenschaften entlang einer bestimmten Richtung. Derartige prismatische Strukturen sind bei Platten weit verbreitet, bei [...]

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• Adaptive Mesh Refinement Techniques for Structural Problems

  E. Oñate, J. Castro

  (1990). The Finite Element Method in the 1990's, E. Oñate et al (Eds.), CIMNE/Springer Verlag

  
  

  Abstract

  In this paper some adaptive mesh refinement (AMR) strategies for finite element analysis of structural problems are discussed. Two mesh optimality criteria based on the equal distribution of: (a) the global error, and (b) the specific error over the elements are studied. It is shown that the correct evaluation of the rate of convergence of the different error norms involved in the AMR procedures is essential to avoid oscillations in the refinement process. The behaviour of the different AMR strategies proposed is compared in the analysis of some structural problems.

  Abstract
  In this paper some adaptive mesh refinement (AMR) strategies for finite element analysis of structural problems are discussed. Two mesh optimality criteria based on the equal [...]

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• Finite element analysis of sheet metal forming problems using a viscous voided shell formulation

  E. Oñate, C. Agelet de Saracibar

  (1988). Modelling of Metal Forming Processes, J.L. Chenot y E. Oñate (Eds.), Kluwer Academic Publisher, pp. 163-178

  
  

  Abstract

  A formal analogy between the equations of pure plastic and viscoplastic flow theory for void containing metals and those of standard non linear elasticity is presented. It is shown how by direct simplifications of the general equations, the standard incompressible flow expressions for non voided metals are obtained. The general formulation is particularized for the analysis of sheet metal forming problems and details of the viscous voided shell and membrane formulations for dealing with the axisymmetric case are given. Finally, some examples of applications of pure and hemispherical stretching and deep drawing of a circular sheet axe presented.

  Abstract
  A formal analogy between the equations of pure plastic and viscoplastic flow theory for void containing metals and those of standard non linear elasticity is presented. It [...]

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

  E. Oñate, M. Manzan

  (2000). Convection Heat Transfer, B. Sundén and G. Comini (Eds.), WIT Press, Southampton, United Kingdom

  
  

  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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• An alpha-adaptive approach for stabilized finite element solution of advective-diffusive problems with sharp gradients

  E. Oñate, J. García-Espinosa, S. Idelsohn

  (1998). New Advances in Adaptive Computational Methods in Mechanics, P. Ladeveze and J.T. Oden (Eds.), Elsevier

  
  

  Abstract

  In this paper the FIC method is used as the basis for a new “alpha-adaptive” procedure (where alpha denotes the stabilization parameters) for obtaining stable solution in advective-diffusive problems where arbitrary sharp transverse gradients are present. The new stabilization thechnique can be viewed as an alternative class of adaptive methods where the numerical solution is enhanced by searching “adaptively” the optimal value of the streamline and transverse (crosswing) stabilization parameters while keeping the mesh and the finite element approximation unchanged. Indeed the basic alpha-adaptive process can be enhanced by combining it with standard h, p or hp adaptive schemes. In the first part of the paper the basis of the FIC stabilized method for advectivediffusive problems are explained. Next the algorithm for computing the streamline and transverse stabilization parameters via the new “alpha-adaptive” procedure is described. Finally, the efficiency and accuracy of the new approach are shown in two examples of application.

  Abstract
  In this paper the FIC method is used as the basis for a new “alpha-adaptive” procedure (where alpha denotes the stabilization parameters) for obtaining stable [...]

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• Possibilities of parallel computing in the finite element analysis of industrial forming processes

  E. Oñate

  (1997). Vector and Parallel Processing - VECPAR'96, Palma J.M.L.M., Dongarra J. (eds) Vector and Parallel Processing — VECPAR'96. VECPAR Lecture Notes in Computer Science, vol. 1215, pp 258-294, Springer, Berlin, Heidelberg

  
  

  Abstract

  The paper presents an overview of the possibilities of parallel computing for the analysis of industrial forming processes using the finite element method. The theoretical and computational aspects of the various finite element formulations are presented in some detail as well as the different strategies for parallehzation of the solver, the mesh generation, the error simulation and the mesh adaption modules. Some examples of parallel analysis of powder compaction and sheet stamping processes using parallel finite element codes developed at CIMNE are finally presented.

  Abstract
  The paper presents an overview of the possibilities of parallel computing for the analysis of industrial forming processes using the finite element method. The theoretical [...]

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• Uso de analogías eléctricas para entender patologías cardiovasculares

  S. Bonilla, E. Soudah

  Monograph CIMNE (2018). M182

  
  

  Abstract

  Through the interconnection of electrical elements such as a resistor, inductor and capacitor, has been developed a reduced-order model of the arterial system capable of describing the behaviour of blood flow. In this modelling, the different differential equations that describe the behaviour of this system are represented implicitly. This allows us to obtain quickly and regulate the performance of the joint model, both in normal physiological conditions and in pathological situations, which makes it a useful tool for teaching or research in cardiovascular physiology. It was implemented two different arterial models, an elastic model and a viscoelastic model, with the aim of analysing the flow and blood pressure that could occur under different physiological conditions. In order to analyse both models, it was contrasted using different orders of elasticity, the pathology of aortic dissection was studied and the results were compared qualitatively with similar solutions observed in the literature. In order to perform these simulations, it was implemented in Matlab a code for solving ordinary differential equations (DAE).

  Abstract
  Through the interconnection of electrical elements such as a resistor, inductor and capacitor, has been developed a reduced-order model of the arterial system capable of describing [...]

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