Metafor

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====== Glossary ======

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


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===== A =====

==== Abaqus ====

Commercial software suite for finite element analysis, usually considered as the reference in nonlinear mechanics. [[#Metafor]] deals with similar mechanical problems as [[wp>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 [[#jacobian|jacobians]]) or 
  * to simulate quasi-Eulerian problems such as stationary problems with a mesh that is almost fixed in space.


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===== 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]]


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===== C =====

==== C++ ====
{{ doc:user:bjarne-stroustrup.jpg?80|doc:user:bjarne-stroustrup.jpg}}
[[#Object-oriented]] programming language used to develop [[#Metafor]]. See also [[wp>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 [[#fe|elements]] on each node that can be in contact with, either, another deformable solid (defo-defo contact), or a [[#Contact Matrices|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, ...


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===== 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. 


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===== F =====

==== Fac ====

Name given to the **F**iles of **A**rchiving and **C**ommunication of [[#Samcef]]. By extension, [[#Metafor]] also writes facs, even if the format is different from [[#Samcef]].

==== FE ====

Finite Element. See also [[Wp>Finite_element]].

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

==== FEM ====

Finite Element Method - [[wp>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.


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===== 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 [[#fe|elements]] on the surface of a mesh (contact, pressure). Nowadays, this concept has been extended to the generation of any [[#fe|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.


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===== J =====

==== Jacobian ====

The jacobian of a [[#fe|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.


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===== 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 [[#fe|finite element]]. A mesh element can be quadrangular, triangular, ... Mesh elements are created by meshers. The user creates finite elements on mesh elements through [[#interaction|interactions]].

==== Metafor ====

Thermo-mechanical [[#fe|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 [[http://www.gdtech.eu/|GDTech]], [[http://www.crmgroup.be/|CRM]] and [[https://www.safran-aero-boosters.com/fr|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.


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===== 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.



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===== 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 [[#fe|Finite Element]] library used by [[#Metafor]]. OOfelie supplies mathematical operations, management of degrees of freedom and a database. See [[http://www.open-engineering.com/|Open Engineering]].



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===== P =====

==== Python ====

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



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===== 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...


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===== 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]].


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===== 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.



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===== 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: [[https://subversion.apache.org/|Subversion]] and [[https://git-scm.com/|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 ====

[[#FE|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.


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===== Z =====

==== Z-Mesh ====

In-house preprocessor, initially created by [[https://scholar.google.fr/citations?user=xvxfKIoAAAAJ&hl=fr|Laurent Stainer]]. "Z" stands for [[wp>Zorglub]]. It has been used as a preprocessor for Metafor until 23/03/2006.