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Latest revision as of 20:48, 26 May 2024
FEM RandbedingungVerschiebung |
Menüeintrag |
---|
Modell → Mechanische Randbedingungen und Belastungen → Randbedingung Verschiebung |
Arbeitsbereich |
FEM |
Standardtastenkürzel |
Keiner |
Eingeführt in Version |
- |
Siehe auch |
FEM-Anleitung |
Beschreibung
Erstellt eine FEM-Randbedingungn für eine festgelegte Verschiebung (Auslenkung) eines ausgewählten Objekts für bestimmte Freiheitsgrade.
Anwendung
- Die Schaltfläche Randbedingung Verschiebung drücken oder den Menüeintrag Modell → Mechanische Randbedingungen und Belastungen → Randbedingung Verschiebung auswählen.
- In der 3D-Ansicht das Objekt auswählen, dem die Randbedingung zugeordnet werden soll; dies kann ein Knoten (Ecke), eine Kante, oder eine Fläche sein.
- Die Schaltfläche Hinzufügen drücken.
- Das Deaktivieren von Unspecified aktiviert die erforderlichen Felder zum Bearbeiten.
- Die Werte anpassen oder (eingeführt mit Version 0.21) eine Formel für die Versatzwerte festlegen.
Formeln
Allgemein
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
Drehungen
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
Hinweise
For the solver CalculiX:
- 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
- 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
- Materials: Solid, Fluid, Nonlinear mechanical, Reinforced (concrete); Material editor
- Element geometry: Beam (1D), Beam rotation (1D), Shell (2D), Fluid flow (1D)
Constraints
- Electromagnetic: Electrostatic potential, Current density, Magnetization
- Geometrical: Plane rotation, Section print, Transform
- Mechanical: Fixed, Displacement, Contact, Tie, Spring, Force, Pressure, Centrif, Self weight
- Thermal: Initial temperature, Heat flux, Temperature, Body heat source
- Overwrite Constants: Constant vacuum permittivity
- Solve: CalculiX Standard, Elmer, Mystran, Z88; Equations: Deformation, Elasticity, Electrostatic, Electricforce, Magnetodynamic, Magnetodynamic 2D, Flow, Flux, Heat; Solver: Solver control, Solver run
- Results: Purge, Show; Postprocessing: Apply changes, Pipeline from result, Warp filter, Scalar clip filter, Function cut filter, Region clip filter, Contours filter, Line clip filter, Stress linearization plot, Data at point clip filter, Filter function plane, Filter function sphere, Filter function cylinder, Filter function box
- Additional: Preferences; FEM Install, FEM Mesh, FEM Solver, FEM CalculiX, FEM Concrete; FEM Element Types
- Erste Schritte
- Installation: Herunterladen, Windows, Linux, Mac, Zusätzliche Komponenten, Docker, AppImage, Ubuntu Snap
- Grundlagen: Über FreeCAD, Graphische Oberfläche, Mausbedienung, Auswahlmethoden, Objektname, Voreinstellungseditor, Arbeitsbereiche, Dokumentstruktur, Objekteigenschaften, FreeCAD unterstützen, Spenden
- Hilfe: Anleitungen, Videoanleitungen
- Arbeitsbereiche: Std Base, Arch, Assembly, BIM, CAM, Draft, FEM, Inspection, Material, Mesh, OpenSCAD, Part, PartDesign, Points, Reverse Engineering, Robot, Sketcher, Spreadsheet, Surface, TechDraw, Test Framework