https://hal.archives-ouvertes.fr/hal-01513346/document

Isogeometric analysis : CAD, finite elements, NURBS, exact geometry and mesh refinement

Large linear systems of saddle point type arise in a wide variety of applications throughout computational science and engineering. Due to their indefiniteness and often poor spectral properties, such linear systems represent a significant challenge for solver developers. In recent years there has been a surge of interest in saddle point problems, and numerous solution techniques have been proposed for this type of system. The aim of this paper is to present and discuss a large selection of solution methods for linear systems in saddle point form, with an emphasis on iterative methods for large and sparse problems.

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Numerical solution of saddle point problems

Introduction to linear and nonlinear programming

IN two previous notes1, Prof. Max Born and I have shown that one can obtain a theory of superconductivity by taking account of the fact that the interaction of the electrons with the ionic lattice is appreciable only near the boundaries of Brillouin zones, and particularly strong near the corners of these. This leads to the criterion that the metal should be superconductive if a set of corners of a Brillouin zone is lying very near the Fermi surface, considered as a sphere, which limits the region in the momentum space completely filled with electrons.

On the theory of superconductivity

This paper describes modern techniques used to solve contact problems within Computational Mechanics. On the basis of a continuum description of contact, the mathematical structure of the contact formulation for finite element methods is derived. Emphasis is also placed on the constitutive behavior at the contact interface for normal and tangential (frictional) contact. Furthermore, different discretization schemes currently applied to solve engineering problems are formulated for small and finite strain problems. These include isoparametric interpolations, node-to-segment discretizations and also mortar and Nitsche techniques. Furthermore, several algorithms related to spatial contact search and fulfillment of the inequality constraints at the contact interface are discussed. Here, especially the penalty and Lagrange multiplier schemes are considered and also SQP- and linear-programming methods are reviewed.


Keywords:

contact mechanics;
friction;
penalty method;
Lagrange multiplier method;
contact algorithms;
finite element method;
finite deformations;
discretization methods

Computational Contact Mechanics

This contribution is concerned with finite-element-formulation of rolling contact problems. For this, first the theoretical background of continuum mechanics and contact kinematics is given for steady and non-steady rolling processes. This includes remarks on the implementation of time-dependent materials.

Finite Element Methods for Rolling Contact

Abstract The virtual element method has been developed over the last decade and applied to problems in solid mechanics. Different formulations have been used regarding the order of ansatz, stabilization of the method and applied to a wide range of problems including elastic and inelastic materials and fracturing processes. This paper is concerned with formulations of virtual elements for higher gradient elastic theories of solids using the possibility, inherent in virtual element methods, of formulating C 1 -continuous ansatz functions in a simple and efficient way. 

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Virtual element formulation for gradient elasticity

Objectives: In this textbook about the Mechanics of Materials we investigate the stressing and the deformations of elastic structures subjected to applied loads. In the first chapter we will restrict ourselves to the simplest structural members, namely, bars under tension or compression.

Tension and Compression in Bars

Computational Mechanics has many applications in engineering. Its range of application has been enlarged widely in the last decades. Still new developments are made to which a new discretization scheme belongs: the virtual element method (VEM). Despite being only few years under development the application range of VEM in engineering includes formulations for linear and nonlinear material responses. In this contribution the focus is on fracture mechanics. Especially the treatment of crack propagation will be discussed where VEM has some advantages. The performance of the formulation is underlined by means of representative examples.

Peter Wriggers

Papers

Finite Element Methods for Rolling Contact

Virtual element formulation for gradient elasticity

Tension and Compression in Bars

Treatment of Brittle Fracture in Solids with the Virtual Element Method

On numerical analysis of thermomechanical contact problems