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--- doc:user:conditions:displacements [2015/01/08 11:23] – boman
+++ doc:user:conditions:displacements [2015/01/08 16:18] – boman
@@ Line 1: / Line 1: @@
 ====== Prescribed Displacements ======
-===== Fixed displacements =====
+===== Basic usage =====
 {{:doc:user:ico-beginner.png?40 |Beginner}}
-A displacement is imposed to a set of nodes with an evolution function and the object ''LoadingSet'':
+A displacement can be prescribed to a set of nodes with an evolution function and the object ''LoadingSet'':
-  loadingset.define(gObject, field, ampl, fct , incr)
+  loadingset.define(target, field, ampl=0.0, fct=None,
-  loadingset.define(gObject, field, ampl, fctMultiChamps , fieldList, incr)
+                    incr=INCREMENTAL_LOAD)
-|''gObject'' | meshed geometric entity where the displacement is imposed |
+  loadingset.define(target, field, ampl, fctMulti, fieldList,
-|''field''   | variable to be fixed|
+                    incr=INCREMENTAL_LOAD)
-|''ampl''   | amplitude |
+with
-|''fct''    | [[doc:user:general:fonctions]] (temporal dependency) |
+|< 100% 8em - - >|
-|''fctMultiChamps ''    | [[doc:user:general:fonctions]] (spatiotemporal dependency) |
+|''target''          | ''GObject''  | meshed geometric entity where the displacement is prescribed |
-|''fieldList''    | list of dependency fields  |
+|''field''           | ''Field1D''  | variable to be prescribed              |
-|''incr'' (optional)| = ''INCREMENTAL_LOAD'' : incremental (default)\\ = ''TOTAL_LOAD'' : total (useful to apply initial displacement or for unreliable integration schemes)|
+|''ampl''            | ''float''    | amplitude                              |
+|''fct''             | ''[[doc:user:general:fonctions|Function]]'' | function for time dependence |
+|''fctMulti'' {{:doc:user:ico-advanced.png?18|Advanced}}        | ''[[doc:user:general:fonctions|Function]]'' | (spatiotemporal dependency) |
+|''fieldList'' {{:doc:user:ico-advanced.png?18|Advanced}}       |              | list of dependency fields  |
+|''incr'' {{:doc:user:ico-advanced.png?18|Advanced}}            | ''enum''     | = ''INCREMENTAL_LOAD'' : incremental (default)\\ = ''TOTAL_LOAD'' : total (useful to apply initial displacement or for unreliable integration schemes)|
 The displacement is then given by
-  * INCREMENTAL_LOAD:  ''u(t1) = u(t0) + ampl * (fct(t1)-fct(t0))''
+  * ''INCREMENTAL_LOAD'':  ''u(t1) = u(t0) + ampl * (fct(t1)-fct(t0))''
-  * TOTAL_LOAD:        ''u(t) = ampl * fct(t)''
+  * ''TOTAL_LOAD'':        ''u(t) = ampl * fct(t)''
-  loadingset.define(gObject, field, ampl, incr)
+__Example:__ FIXME
-|''gObject'' | meshed geometric entity where the displacement is imposed |
+\\
-|''field''   | variable to be fixed |
-|''ampl''   | amplitude  = 0 by default |
-|''incr'' (optional)| = ''INCREMENTAL_LOAD'' : incremental (default) |
-|           |= ''TOTAL_LOAD'' : total (to set a non zero value or to set a remeshed configuration with respect to the origin)|
-Careful, it is not allowed to have a non zero amplitude in incremental. It would lead to a ''FATAL_ERROR''.
+=====  Activation/Deactivation of boundary conditions =====
+{{:doc:user:ico-advanced.png?40 |Advanced}}
+Prescribed displacements can be added or removed during the computation.
-Default value are used to fix nodes quite easily :
+It is useful to add some prescribed displacements for example when we want to avoid numerical vibrations or rigid body modes. Conversely, it is sometimes useful to drive a workpiece to a desired position, then to remove the prescribed displacements and let the workpiece deform freely.
-  loadingset.define(gObject, field)
+For any calculation, the simulation time is automatically divided into several stages (''Stage'' objects) using the ''setNextTime()'' method of the ''[[doc:user:integration:general:time_step|TimeStepManager]]''.
+For each stage, it is possible to activate (''activate()'') and deactivate (''deactivate()'') any ''Loading'' (including prescribed displacements).
-=====  Dynamic fixed displacements =====
+After the configuration of the ''[[doc:user:integration:general:time_step|TimeStepManager]]'', all the defined stages can be retrieved using:
-{{:doc:user:ico-advanced.png?40 |Advanced}}
-Fixed displacements can be added or removed during the computation. It is useful to avoid numerical vibrations or rigid body modes.
-Time is divided into stages using ''setNextTime'' (see [[doc:user:integration:general:time_step|TimeStepManager]]). Then it is possible to activate (''activate'') and deactivate (''deactivate'') loads for each stage.
+  stages = metafor.getStageManager()
-All these stages can be retrieved using (commands on the [[doc:user:integration:general:time_step|TimeStepManager]] must be done already):
+==== Example ====
-  stages = metafor.getStageManager()
-Example : definition of a load on curve #4 and deactivation during stage #1 (corresponding to the second stage since numbers starts with 0):
+Definition of a prescribed displacement on ''Curve'' #4 and deactivation during stage #1 (corresponding to the second stage since numbering starts with 0):
-  load1 = loadingset.define(curveset(4), Field1D(TY,RE),  1.0, fct2)
+  load1 = loadingset.define(curveset(4), Field1D(TY,RE), 1.0, fct2)
   load1.deactivate(stages[1])
-Definition of a load on curve #1, deactivated during stage #1 and activated for the next ones:
+Definition of a load on ''Curve'' #1, deactivated during stage #1 and activated for the next ones:
-  load2 = loadingset.define(curveset(1), Field1D(TY,RE),  -0.1, fct1)
+  load2 = loadingset.define(curveset(1), Field1D(TY,RE), -0.1, fct1)
   load2.deactivate(stages[0])
   load2.activate(stages[1])
-These two loads are represented schematically as :
+These two loads are represented schematically as:
 |          ^  load1  ^  load2  ^
-^ phase #0 |  ACTIVE    |  INACTIVE |
+^ stage #0 |  ACTIVE    |  INACTIVE  |
-^ phase #1 |  INACTIVE  |  ACTIVE   |
+^ stage #1 |  INACTIVE  |  ACTIVE    |
-^ phase #2 |  INACTIVE  |  ACTIVE   |
+^ stage #2 |  INACTIVE  |  ACTIVE    |
-:!: Order of operations :
+<note important>Order of operations: Activation surpasses deactivation: A node can indeed be part of two entities, one activated, one deactivated. But the operation of deactivation will be done first, then the activation, so such a node will be activated.</note>
-      "Activation surpasses deactivation"
-A node can indeed be part of two entities, one activated, one deactivated. But the operation of deactivation will be done first, then the activation, so such a node will be activated.