# Metafor

ULiege - Aerospace & Mechanical Engineering

### Site Tools

doc:user:general:glossaire

# 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

Commercial software suite for finite element analysis, usually considered as the reference in nonlinear mechanics. Metafor deals with similar mechanical problems as ABAQUS.

### ALE

Arbitrary Lagrangian-Eulerian formalism: method which separates the motions of mesh and the material. The ALE can be used:

• to keep a valid mesh throughout the simulation of very large deformations (avoiding negative jacobians) or
• to simulate quasi-Eulerian problems such as stationary problems with a mesh that is almost fixed in space.

## B

### Bacon

Meat product prepared from cured pork, or preprocessor of Samcef.

### Baconnerie

Absurd way to write an input file.

### Battery

Also called the “test battery”. It is actually a test suite made of more than 2000 input files that are checked for each new version of Metafor. It is also an interesting source of examples for people who want to learn how to use Metafor. The main folder of the battery is apps.

### Bfac

Binary Fac ⇒ see Fac

## C

### C++

Object-oriented programming language used to develop Metafor. See also C++.

### 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 elements on each node that can be in contact with, either, another deformable solid (defo-defo contact), or a rigid contact tool (rigid-defo contact).

### Contact Matrices

Also called “contact tools” in metal forming. A contact matrix is a perfectly rigid geometric object (a cylinder, a plane, …) which can come into contact with a mesh. For instance, a drawing punch or a blankholder may be modeled by a contact matrix.

### Curves

When used on its own, the word “curve” must be understood as “history curve”, which is a series of values extracted from the simulation at each time step, then saved in a text file with a .ascii extension. For example, Metafor can build curves for contact forces over time, plastic strains in a section, nodal temperatures, …

## D

### 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 time integration algorithm.

### FEM

Finite Element Method - FEM.

### Fortran

Obsolete programming language still used by many commercial finite element codes.

### FV

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

## I

### Input file

Text file describing the geometry, mesh, boundary conditions and time integration parameters of a simulation. In Metafor, an input file is a series of Python commands gathered in a module.

### Interaction

At first, an interaction was the object managing the boundary condition elements 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 an equilibrated 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 inverted or distorted, in which case the computation cannot continue further.

## M

### Machine

In the context of this website, a “machine” is neither a power saw nor a pneumatic drill but rather a PC or sometimes a coffee machine.

### Material

A material is the implementation of a constitutive law which defines the evolution of stresses with respect to strains. By extension, a 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 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 creates 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 become bigger and bigger and now gathers the contributions from all researchers in the laboratory. It is also used on a commercial way by GDTech, CRM and Safran Aero Boosters.

### 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 time integration scheme, The balance of forces is solved at each time step by a Newton-Raphson algorithm.

## O

### Object-Oriented

Programming method which consists in dividing concepts in objects. C++ and Python are both object-oriented languages.

### oo_meta

Old name of the C++ version of Metafor, when the translation from Fortran was not yet fully performed.

### 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. Two VCS are used today for Metafor: Subversion and git. these VCS allow the simultaneous modification of the source code by several developers, and facilitate updates and synchronization. Thanks to the 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 or a tetrahedron), and a surface geometry in 2D (such as a quadrangle or a triangle). Volume elements are a subset of “elements”. Other types of elements include contact elements, pressure elements, shells, …

### VTK

Graphical library for displaying 2D/3D meshes and results in the graphical user interface of Metafor.

## Z

### Z-Mesh

In-house preprocessor, initially created by Laurent Stainer. “Z” stands for Zorglub. It has been used as a preprocessor for Metafor until 23/03/2006.

doc/user/general/glossaire.txt · Last modified: 2017/10/25 11:51 by boman