====== Spring ======
===== Materials  =====

A spring (linear or not, with or without failure criterion) is defined is the same way as volume materials:

  materialno = materialset.define (number, type)
  materialno = materialset(number)
  materialno.put(param, value)
  materialno.depend(param, fct, Key(Lock)))
  ...

|''number'' | spring number (must be unique for all element in ''materialset'', not just for springs) |
|''type'' | type of spring (for example ''ConstantSpringMaterial'') |
|''param'' | name of the spring parameter (for example ''SPRING_FK'') |
|''value'' | value of the corresponding parameter|
|''fct'' | function which characterizes the dependency of the property (optional: no ''fct'' if no dependency) |
|''Lock'' | [[doc:user:general:locks|Lock]] which defines the dependency variable of the property (compulsory if there is a dependency) |

==== ConstantSpringMaterial ====

=== Description ===

Linear spring

=== Parameters ===
^   Name                                          ^     Metafor Code     ^  Dependency ^
| Stiffness|  ''SPRING_FK''  |  -  |
| Damping coefficient   |  ''SPRING_FC''  |  -  |
 
==== NonLinearSpringMaterial ====

=== Description ===

Nonlinear spring.

=== Parameters ===
^   Name                                          ^     Metafor Code     ^  Dependency ^
| Amplitude of the associated **stiffness force** as a function of the elongation. This force is described by the associated ''nf'' function. Careful, this function must also be described for negative elongation (compression)                      |  ''SPRING_FK''  |  ''GD''  |
| Amplitude of the associated **damping force** as a function of the elongation rate. This force is described by the associated ''nf'' function. Careful, this function must also be described for negative elongation rates         |  ''SPRING_FC''  |  ''GV''  | 

Remarks :  

  * ''SPRING_FK'' et ''SPRING_FC'' are forces and not stiffness/damping coefficient (unlike ConstantSpringMaterial)
  * the dependency is written as :
''materialset(no).depend(SPRING_FK,fct1,Field1D(TX,RE))''\\
''materialset(no).depend(SPRING_FC,fct2,Field1D(TX,GV))''

      
==== BreakingSpringMaterial ====

=== Description ===

Nonlinear spring with failure criterion.

=== Parameters ===
^   Name                                          ^     Metafor Code     ^  Dependency ^
| Stiffness|  ''SPRING_FK''  |  -  |
| Damping coefficient   |  ''SPRING_FC''  |  -  | 
| Maximal length of the spring. Above, failure appears and forces are equal to zero. This length can depend on time though ''nf''    |  ''SPRING_LMAX''  |  ''TM''  |

===== Element=====

Once the [[#Materials|material]] is defined, it must be associated to an ''[[doc:user:elements:general:def_element_properties|ElementProperties]]'':

  prp = ElementProperties(typeEl)
  prp.put(param1, value1)
  prp.depend(param1, fct1, Lock1)) #facultatif
  ...

where

|''typeEl'' | desired element (for example ''Spring[2|3]DElement'')|
|''param1''| name of the property associated to the element (for example ''MATERIAL'' to associate the desired material)|
|''value1''| value of the corresponding property |
|''fct1''| function which characterizes the dependency of the property (optional: no fct if no dependency) |
|''Lock1''| [[doc:user:general:locks|Lock]] which defines the dependency variable of the property (compulsory if there is a dependency) |

==== Spring[2|3]DElement ===

Nonlinear spring element. Associates two nodes with a stiffness. No axisymmetric correction is implemented. They must be associated with a ''[[#Interaction|FieldApplicator]]'' interaction.

=== Parameters ===
^   Name                                          ^     Metafor Code     ^  Dependency ^
| ''MATERIAL''    | Number of the spring material to consider             |  -  |
| ''STIFFMETHOD'' | Method used to compute the stiffness matrix\\ = ''STIFF_ANALYTIC'' : analytic matrix (default)\\ = ''STIFF_NUMERIC''  : numerical matrix \\ <del>Not applicable, only the numerical one exists !</del> |  -  |
| ''SPRING_LI''   | Defines the spring length "at rest" (relevant or not depending on the value of SPRING_CLI) |  |
| ''SPRING_CLI''  | Defines the way the "length at rest" (''lengthIni '') will be computed \\ assume L0 is the measured length at the end of the preprocessing (geometrical length)\\ = 0 : lengthIni = L0 (default - do not require SPRING_LI)\\ = 1 : lengthIni = SPRING_LI \\ = 2 : lengthIni = L0 * SPRING_LI \\ = 3 : lengthIni = L0 + SPRING_LI                           |  -  |

===== Interaction =====

Finally, once the ''Spring[2|3]DElement'' ''[[#Element|ElementProperties]]'' is defined, the corresponding interaction is generated with the ''FieldApplicator''. To do so, the corresponding geometric mesh element must be generated using [[doc:user:geometry:mesh:1D]]. Once done, the interaction can be defined and included in the ''interactionset'':

  app = FieldApplicator(no)
  app.push(gObject1)
  app.push(gObject2)
  ...
  app.addProperty(prp)        # association of an ElementProperties
  interactionset.add(app)     # the interaction is added in InteractionSet 

or

  app = interactionset.add(FieldApplicator(no)) #add returns a reference
  app.push(gObject1)
  app.push(gObject2)
  ...
  app.addProperty(prp)        # association of an ElementProperties
  
where 
| ''no''  | number of the ''Interaction'' (which is to say the ''FieldApplicator'') | 
|''gObject1''  | mesh geometric entity where the finite elements are applied |
| ''prp'' | [[doc:user:elements:general:def_element_properties|Properties]] of [[#spring_2_3_delement|spring elements]] to generate.|