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Glossary

If you have never used a finite element software, nor learned about nonlinear mechanics, this page will help you understand Metafor specific vocabulary.

A

Abaqus

doc:user:abaqus-6-6.jpg Commercial software suite for finite element analysis, usually considered as the reference in nonlinear mechanics. Metafor deals with similar issues as ABAQUS, at a smaller scale.

A.L.E.

Arbitrary Lagrangian-Eulerian Formulation: method which allows to separate the motions of mesh and matter. The ALE is used to keep a valid mesh geometry (avoiding negative jacobians) or to simulate quasi-Eulerian problems (such as stationary rolling).

B

Bacon

Preprocessor of Samcef.

Baconnerie

Manière absurde d'introduire des données.

Battery

Also called test battery. The battery is made of all the data sets whose results are checked for each new version of Metafor.

Bfac

Binary Fac ⇒ see Fac

C

C++

doc:user:bjarne-stroustrup.jpg Object-oriented programming language used to develop Metafor. See also C++.

CAD

doc:user:modell-cad.jpg Computer Aided Design. By extension, the CAD of a test case is its geometry.

Code de calcul

Autre manière d'appeler un logiciel qui bouffe du CPU.

Contact

Interaction between two solids which models the fact that they cannot penetrate each other during the computation. Contact induces nonlinearities in the computation. The penalty method is most often used in Metafor. To handle contact, Metafor creates contacts éléments on each node that can be in contact with, either, another deformable solid (defo-defo contact), or a rigid contact matrix (also called die, rigid-defo contact).

Contact Matrices

Also called “dies” in Metal Forming. A contact matrix is a rigid geometric object (cylindrical, plane or of more complex shape) which can come into contact with the meshed part. For instance, a roll and a drawing punch may be modeled by one or more contact matrices.

Curves

When used on its own, the word “curve” must be understood as “temporal result curve”, which is a series of values extracted from the simulation at each time step, then saved in a .ascii file (usable in Matlab). For example, Metafor can plot contact forces over time, plastic strains in a section, punctual temperature …

D

Data set

Text file describing the geometry, mesh, boundary conditions and temporal integration parameters of a simulation. In Metafor, a data set is a series of commands gathered in a module and interpreted by Python.

DLL

Dynamic-link library, on Windows. Equivalent to .so files on Unix/Linux.

Metafor is made of around 20 libraries on Windows. It also depends on other librarires, such as VTK, Qt ou les BLAS. On Unix, Metafor has not yet been split into DLLs.

F

Fac

Name given to the Files of Archiving and Communication of Samcef. By extension, Metafor also writes facs, even if the format is different from Samcef.

FE

Finite Element. See also Finite_element.

In Metafor, elements are objects that compute forces and send them back to the integration algorithm.

FEM

Finite Element Method - FEM.

Fortran

Obsolete language still used by the elderly.

Franglais

Langue utilisée entre autres par Metafor (voir BFac par exemple) malgré nos efforts pour l'éviter.

FV

Finite Volume. Alternative discretization technique, in opposition with Finite Element. Finite Volumes are used to model convection with the ALE formulation.

G

GPL

GNU Public License : most widely used free software license, see site GNU. Metafor license is unfortunately not GPL.

I

Interaction

At first, an interaction was the object managing the boundary condition éléments on the surface of a mesh (contact, pressure). Nowadays, this concept has been extended to the generation of any finite element, even Volume Element.

Interpreter

Command line – see python.

Iterations

On its own, iteration means mechanical iteration of the Newton-Raphson algorithm, used at each time step to converge to the right solution.

J

Jacobian

The jacobian of a element characterizes the factor by which the volume of this element expands or shrinks between a given configuration and the reference one. It is always positive, unless the element orientation was reversed, in which case the computation cannot continue further.

L

LGPL

License derived from GPL (Lesser GPL), usually used for libraries, allowing the developer to use LGPL without having to make its code GPL. Consequently, a commercial software may use LGPL libraries. See site GNU. For example, Metafor uses Nurbs++, which is LGPL.

M

Machine

Dans le contexte de ce site, une machine n'est pas une perceuse ni un une scie électrique mais plutôt un PC ou, à la rigueur, la machine à café.

Material

A material defines the evolution of stresses with respect to strains. By extension, contact material is the name used when talking about friction laws.

Memory leak

Quite often seen when programming with an object-oriented language. It is due to allocated memory which is never freed. So solve this, destructors can be programmed or more RAM bought.

Mesh

In Metafor, the mesh geometry is simply called mesh, in opposition with the user geometry, which is the one encoded by the user in its data set.

Mesh element

In Metafor, a mesh element is the geometric part of a finite element. A mesh element can be quadrangular, triangular, … Mesh elements are created by meshers. The user applies finite elements on mesh elements through interactions.

Metafor

Thermo-mechanical Finite Element software developed in the LTAS-MN2L, taking large strains of solids into account. Initially started by J.-P. Ponthot, Metafor has grown and now gathers the contributions from all scientists in the laboratory. it is also used on a commercial way by GDTech.

Module

Python file representing either a library of objects and functions or a test case. In the latter case, the module contains the objects Domain, which must be defined by every Metafor model.

Multiphysics

Which can manage more than one field of unknown. For example, mechanical unknowns (x, y, z), temperature field T, electric and magnetic fields… In Metafor, only mechanical and thermal fields are considered.

N

Newton-Raphson

Iterative algorithm which can solve a system of nonlinear equations. In Metafor, with an implicit integration scheme, Newton's equation is solved at each time step by Newton-Raphson algorithm.

O

Object-Oriented

Programming method which consists in dividing concepts in classes, to which data and functions to process this data are associated. It is possible to program this way with every language, but it is easier with some. C++ was used in Metafor, and Python is also object-oriented.

Oo_meta

Old name of the C++ version of Metafor, when one was certain the conversion from Fortran was successful.

Oofelie

Commercial Finite Element library used by Metafor. OOfelie supplies mathematical operations, management of degrees of freedom and a database. See Open Engineering.

P

Python

Interpreted object-oriented programming language. Python is used as an interpreter (command line) by Metafor.

R

RTFM

La réponse de Luc à beaucoup de questions, RFTM, ou Read The Fucking Manual. Ironiquement, il n'y a souvent pas de Fucking Manual à lire, ou alors il n'est plus à jour, mais bon, faut pas chercher…

S

Samcef

Software initally created by the LTAS, in the University of Liège. Samtech, first spin-off of the university, has commercialized Samcef for years. In the laboratory, Samcef is used through Bacon to import complex geometry in Metafor.

T

Test case

A test case is a simulation on Metafor (see also data set and module).

Time Step

When a part experiences large strains in a quasi-static way, it is usually impossible to compute the deformed configuration with only one matrix inversion. It must be done incrementally, so the loading time is divided in several time steps. The name “time step” is used by similarity to dynamic schemes, even if, in quasi-static configurations without viscosity, time is irrelevant in the solution.

Tuple

In Python, a tuple corresponds to a ordered set of values which cannot be modified. For instance, (1, 2, 'a', “tuple”) is a tuple. A tuple can include another tuple.

V

VCS

Version Control System. Software in charge of the management of changes in Metafor source code, and the verification of the battery. VCS allows the simultaneous modification of the code by several developers, and facilitate updates and synchronization. Thanks to VCS and to a lot of work, only one version of Metafor exists today.

Volume Element

Finite Element which has a volume geometry in 3D (such as an hexaedron), and a surface geometry in 2D (such as a quadrangle). Volume elements are are a subset of elements, such as contact elements, pressure elements, shells, …

Vtk

Graphical library used by Metafor, under LGPL license.

Z

Z-Mesh

Home made preprocessor, initially created by Laurent Stainer. Z stands for Zorglub (what else could it be ?). Since the 23/03/06, it is no longer used, since the import from Bacon is directly done with Python.

doc/user/general/glossaire.1466067247.txt.gz · Last modified: 2016/06/16 10:54 by joris

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