Scipedia: Eugenio Oñate’s Book Chapters

A simple method for automatic adaption of finite element meshes to changes in the boundary shape

María Jesús Samper — Mon, 01 Jul 2019 15:58:08 +0200

A simple method to automatically update the finite element mesh of the analysis domain is proposed for cases when the shape of the domain in modified. The method considers the mesh as a fictitious elastic body subjected to prescribed displacement 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 of remeshing in the solution of shape optimization problems and reduces the number of the remeshing step in the solution of coupled fluid-structure interaction problems

A finite element method for fluid-structure interaction with surface waves

Scipedia content — Tue, 24 May 2016 18:45:02 +0200

A stabilized semi-implicit fractional 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.

Meshless analysis of incompressible flows using the Finite Point Method

María Jesús Samper — Wed, 22 May 2019 13:09:46 +0200

A stabilized finite point method (FPM) for the meshless analysis of incompressible fluid flow problems is presented. The stabilization approach is based in the finite calculus (FIC) procedure. 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 incompressible flow problems are presented.

Stabilization techniques for finite element analysis of convection-diffusion problems

María Jesús Samper — Wed, 29 May 2019 12:05:39 +0200

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.

Stochastic analysis of an impact problem

María Jesús Samper — Tue, 04 Jun 2019 11:12:10 +0200

Analysis of the structure of gothic cathedrals. Application to Barcelona cathedral

María Jesús Samper — Wed, 29 May 2019 13:52:28 +0200

The study of ancient structures composed of stone arches and vaults requires the use of specific techniques of analysis endowed with powerful procedures for the modelling of geometry, the simulation of the mechanical response of the various materials (including ashlar blocks and masonry, backings and fills) and the simulation of the structure or may have affected it through history. More specifically, those techniques must be able to reproduce the actual conditions of thrust equilibrium between the large number of curved, linear or two-dimensional members involved.

The validity of several modelling techniques with a very different level of sophistication is studied through their use in the study of a particular Gothic construction: Barcelona Cathedral. The various techniques used were developed at the school of civil engineering of the technical university of Catalonia and have already been used in the analysis of a set historical constructions, including the Basilica of San Marco (Oñate et al., 1997) and the Crypt of the Colònia Güell (Roca, 1997).

The present study of Barcelona Cathedral, now under development, is thus not only aimed at gaining a better understanding of various aspects of the resistance of Gothic constructions (and the southern and Catalan Gothic, in particular) but also at appraising the possibilities and limitations of various analytical techniques.

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

María Jesús Samper — Wed, 29 May 2019 11:58:51 +0200

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.

Efficient computational aspects for analyses of sheet stamping problems

María Jesús Samper — Tue, 04 Jun 2019 11:07:19 +0200

Efficiency and accuracy are vital for the acceptable simulation of large scale industrial sheet stamping problems. Two aspects, implemented within the explicit dynamic program STAMPACK, that effectively address this problem are described: an anisotropic plasticity material model combined with a thin shell element that contains only displacement degrees of freedom and an effective drawbead formulation based on an elastic-plastic analogy

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

María Jesús Samper — Wed, 29 May 2019 13:30:14 +0200

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

María Jesús Samper — Wed, 29 May 2019 13:20:24 +0200

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.

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

María Jesús Samper — Wed, 29 May 2019 11:49:53 +0200

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.

Enhanced prediction of structural instability points using a critical displacement method

María Jesús Samper — Tue, 04 Jun 2019 10:57:17 +0200

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

María Jesús Samper — Tue, 04 Jun 2019 10:52:48 +0200

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.

Finite elements versus finite volumes. Is there really a choice?

María Jesús Samper — Mon, 25 Nov 2019 14:51:43 +0100

The finite volume method appears to be a particular case of finite elements with a non Galerkin weighting. It is course less accurate for self adjoint problems but has some computationally useful features for first order equations involving only surface integrals. For certain problems this is a substational economy and leads to computationally useful approximations.

Numerical modelling of sheet metal forming problems

María Jesús Samper — Wed, 29 May 2019 12:58:28 +0200

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).

Finite Streifenmethode für Mindlinsche Platten und axialsymmetrische Schalen

María Jesús Samper — Wed, 29 May 2019 12:49:57 +0200

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.

Adaptive Mesh Refinement Techniques for Structural Problems

María Jesús Samper — Wed, 29 May 2019 12:41:30 +0200

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.

Fractura elastoplástica: Modelos elastoplásticos para la simulación numérica de procesos de fractura

María Jesús Samper — Mon, 01 Jul 2019 15:36:54 +0200

A finite element formulation for the geometrically non linear analysis of shells using a total lagrangian approach

María Jesús Samper — Mon, 01 Jul 2019 15:31:54 +0200

A total Lagrangian formulation for the large displacement large rotation: analysis of shells using finite elements is presented. Different expressions for the strain matrix obtained using various displacement interpolation forms are discussed and details of the obtention of the tangent stiffness matrix are given. Simplifications of the general 3D shell formulation for 2D shells are also presented together with some examples of applications.

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

María Jesús Samper — Wed, 29 May 2019 12:29:27 +0200

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.