FEM ConstraintDisplacement/ru: Difference between revisions

From FreeCAD Documentation
(Updating to match new version of source page)
(Updating to match new version of source page)
 
(6 intermediate revisions by the same user not shown)
Line 1: Line 1:
<languages/>
<languages/>

{{Docnav/ru
{{Docnav/ru
|[[FEM_ConstraintFixed/ru|Constraint fixed]]
|[[FEM_ConstraintFixed/ru|Constraint fixed]]
Line 23: Line 24:
==Описание==
==Описание==


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


<span id="Usage"></span>
<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}}.
# Press the {{Button|[[Image:FEM_ConstraintDisplacement.svg|16px]] [[FEM_ConstraintDisplacement|Displacement boundary condition]]}} button or select the menu {{MenuCommand|Model → Mechanical boundary conditions and loads → [[Image:FEM_ConstraintDisplacement.svg|16px]] Displacement boundary condition}}.
# 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 boundary condition should be applied to, which can be a vertex (corner), edge, or face.
# Press the {{Button|Add}} button.
# Press the {{Button|Add}} button.
# Uncheck ''Unspecified'' to activate the necessary fields for edition.
# Uncheck ''Unspecified'' to activate the necessary fields for editing.
# Set the values or ({{Version|0.21}}) specify a formula for the displacements.
# Set the values or ({{Version|0.21}}) specify a formula for the displacements.


Line 60: Line 61:
===Rotations===
===Rotations===


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


If for example a face should be rotated according to this condition:
If for example a face should be rotated according to this condition:
Line 88: Line 89:


For the [[Image:FEM_SolverCalculixCxxtools.svg|32px]] [[FEM_SolverCalculixCxxtools|solver CalculiX]]:
For the [[Image:FEM_SolverCalculixCxxtools.svg|32px]] [[FEM_SolverCalculixCxxtools|solver CalculiX]]:
* The constraint uses the *BOUNDARY card.
* This tool 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
Line 104: Line 105:
{{FEM Tools navi{{#translation:}}}}
{{FEM Tools navi{{#translation:}}}}
{{Userdocnavi{{#translation:}}}}
{{Userdocnavi{{#translation:}}}}
{{clear}}

Latest revision as of 16:12, 16 November 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 boundary condition for a prescribed displacement of a selected object for specified degrees of freedom.

Применение

  1. Press the Displacement boundary condition button or select the menu Model → Mechanical boundary conditions and loads → Displacement boundary condition.
  2. In the 3D view select the object the boundary condition 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 editing.
  5. Set the values or (introduced in version 0.21) specify a formula for the displacements.

Formulas

introduced in version 0.21

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 given 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 boundary condition. 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) refers to the first coordinate x
  • pi denotes and was added so that after a rotation of 180° is performed

Примечания

For the solver CalculiX: