FEM ConstraintDisplacement/ru: Difference between revisions

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<span id="Description"></span>
==Описание==
==Описание==


Creates a FEM constraint for a prescribed displacement of a selected object for a specified degree of freedom.
Creates a FEM constraint for a prescribed displacement of a selected object for a specified degree of freedom.


<span id="Usage"></span>
==Применение==
==Применение==


# Either press the button {{Button|[[Image:FEM_ConstraintDisplacement.svg|16px]] '''FEM FEM_ConstraintDisplacement'''}} or select the menu {{MenuCommand|Model → Mechanical Constraints → [[Image:FEM_ConstraintDisplacement.svg|16px]] Constraint displacement}}.
# There are several ways to invoke the command:
#* Press the {{Button|[[Image:FEM_ConstraintDisplacement.svg|16px]] [[FEM_ConstraintDisplacement|FEM ConstraintDisplacement]]}} button.
#* Select the {{MenuCommand|Model → Mechanical Constraints → [[Image:FEM_ConstraintDisplacement.svg|16px]] Constraint displacement}} option from the menu.
# In the [[3D_view|3D view]] select the object the constraint should be applied to, which can be a vertex (corner), edge, or face.
# In the [[3D_view|3D view]] select the object the constraint should be applied to, which can be a vertex (corner), edge, or face.
# Press the {{Button|Add}} button.
# Choose a degree of freedom or prescribe a displacement.
# Uncheck ''Unspecified'' to activate the necessary fields for edition.
# Set the values or ({{Version|1.0}}) specify a formula for the displacements.


==Formulas==

{{Version|1.0}}

===General===

For the [[Image:FEM_SolverElmer.svg|32px]] [[FEM_SolverElmer|solver Elmer]] it is possible to define the displacement as a formula. In this case the solver sets the displacement according to the give formula variable.

Take for example the case that we want to perform a [[FEM_SolverElmer_SolverSettings#Timestepping|transient analysis]]. For every time step the displacement <math>d</math> should be increased by 6 mm:

<math>\quad
d(t)=0.006\cdot t
</math>

enter this in the ''Formula'' field:</br>
{{incode| Variable "time"; Real MATC "0.006*tx"}}

This code has the following syntax:
* the prefix ''Variable'' specifies that the displacement is not a constant but a variable
* the variable is the current time
* the displacement values are returned as ''Real'' (floating point) values
* ''MATC'' is a prefix for the Elmer solver indicating that the following code is a formula
* ''tx'' is always the name of the variable in ''MATC'' formulas, no matter that ''tx'' in our case is actually ''t''

===Rotations===

Elmer only uses the '''Displacement *''' fields of the constraint. To define rotations, we need a formula.

If for example a face should be rotated according to this condition:

<math>\quad
\begin{align}
d_{x}(t)= & \left(\cos(\phi)-1\right)x-\sin(\phi)y\\
d_{y}(t)= & \left(\cos(\phi)-1\right)y+\sin(\phi)x
\end{align}
</math>

then we need to enter for '''Displacement x'''</br>
{{incode| Variable "time, Coordinate"
Real MATC "(cos(tx(0)*pi)-1.0)*tx(1)-sin(tx(0)*pi)*tx(2)}}

and for '''Displacement y'''</br>
{{incode| Variable "time, Coordinate"
Real MATC "(cos(tx(0)*pi)-1.0)*tx(2)+sin(tx(0)*pi)*tx(1)}}

This code has the following syntax:
* we have 4 variables, the time and all possible coordinates (x, y z)
* ''tx'' is a vector, ''tx(0)'' refers to the first variable, the time while ''tx(1)'' is the first coordinate ''x''
* ''pi'' denotes <math>\pi</math> and was added so that after <math>t=1\rm\, s</math> a rotation of 180° is performed

<span id="Notes"></span>
==Примечания==
==Примечания==


For the [[Image:FEM_SolverCalculixCxxtools.svg|32px]] [[FEM_SolverCalculixCxxtools|solver CalculiX]]:
* The constraint uses the *BOUNDARY card in CalculiX.
* The constraint uses the *BOUNDARY card.
* Fixing a degree of freedom is explained at http://web.mit.edu/calculix_v2.7/CalculiX/ccx_2.7/doc/ccx/node164.html
* Fixing a degree of freedom is explained at http://web.mit.edu/calculix_v2.7/CalculiX/ccx_2.7/doc/ccx/node164.html
* Prescribing a displacement for a degree of freedom is explained at http://web.mit.edu/calculix_v2.7/CalculiX/ccx_2.7/doc/ccx/node165.html
* Prescribing a displacement for a degree of freedom is explained at http://web.mit.edu/calculix_v2.7/CalculiX/ccx_2.7/doc/ccx/node165.html

Revision as of 10:45, 1 April 2023

Other languages:

FEM ConstraintDisplacement

Системное название
FEM ConstraintDisplacement
Расположение в меню
Model → Mechanical Constraints → Constraint displacement
Верстаки
FEM
Быстрые клавиши
Нет
Представлено в версии
-
См. также
FEM tutorial

Описание

Creates a FEM constraint for a prescribed displacement of a selected object for a specified degree of freedom.

Применение

  1. Either press the button FEM FEM_ConstraintDisplacement or select the menu Model → Mechanical Constraints → Constraint displacement.
  2. In the 3D view select the object the constraint should be applied to, which can be a vertex (corner), edge, or face.
  3. Press the Add button.
  4. Uncheck Unspecified to activate the necessary fields for edition.
  5. Set the values or (introduced in version 1.0) specify a formula for the displacements.

Formulas

introduced in version 1.0

General

For the solver Elmer it is possible to define the displacement as a formula. In this case the solver sets the displacement according to the give formula variable.

Take for example the case that we want to perform a transient analysis. For every time step the displacement should be increased by 6 mm:

enter this in the Formula field:
Variable "time"; Real MATC "0.006*tx"

This code has the following syntax:

  • the prefix Variable specifies that the displacement is not a constant but a variable
  • the variable is the current time
  • the displacement values are returned as Real (floating point) values
  • MATC is a prefix for the Elmer solver indicating that the following code is a formula
  • tx is always the name of the variable in MATC formulas, no matter that tx in our case is actually t

Rotations

Elmer only uses the Displacement * fields of the constraint. To define rotations, we need a formula.

If for example a face should be rotated according to this condition:

then we need to enter for Displacement x
Variable "time, Coordinate" Real MATC "(cos(tx(0)*pi)-1.0)*tx(1)-sin(tx(0)*pi)*tx(2)

and for Displacement y
Variable "time, Coordinate" Real MATC "(cos(tx(0)*pi)-1.0)*tx(2)+sin(tx(0)*pi)*tx(1)

This code has the following syntax:

  • we have 4 variables, the time and all possible coordinates (x, y z)
  • tx is a vector, tx(0) refers to the first variable, the time while tx(1) is the first coordinate x
  • pi denotes and was added so that after a rotation of 180° is performed

Примечания

For the solver CalculiX: