FEM Ограничение перемещения
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| Расположение в меню |
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| 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.
The FEM displacement task panel
Применение
- There are several ways to invoke the command:
- Press the
Displacement Boundary Condition button
- Select the Model → Mechanical Boundary Conditions and Loads →
Displacement Boundary Condition option from the menu.
- Press the
- Press the Add button.
- In the 3D View select the object the boundary condition should be applied to, which can be a vertex, edge, or face (but all the selected objects have to be of the same type). To remove objects from the list, press the Remove button and click on them.
- Check the boxes next to the degrees of freedom that you want to use. By default, they are set to zero (fixed) but any value (introduced in 0.21: or a formula for Elmer) can be specified. Rotations make sense only for beam and shell elements.
Formulas
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
Properties
- ДанныеEnable Amplitude - introduced in 1.1: Enables the use of CalculiX's amplitude for the time variation of the displacement boundary condition. At a given time, magnitude of the boundary condition is multiplied by the amplitude value corresponding to that time. Linear interpolation is used between the specified values. Constant values are used outside of the specified range.
- ДанныеAmplitude Values - introduced in 1.1: Amplitude table in the following format:
time_1, amplitude_value_1 …
- Default is linear increase from 0% at t=0 to 100% at t=1:
0, 0 1, 1
Примечания
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 Material, Fluid Material, Non-Linear Mechanical Material, Reinforced Material (Concrete); Material Editor
- Element Geometry: Beam Cross Section, Beam Rotation, Shell Plate Thickness, Fluid Section for 1D Flow
- Electromagnetic Boundary Conditions: Electrostatic Potential Boundary Condition, Current Density Boundary Condition, Magnetization Boundary Condition, Electric Charge Density
- Fluid Boundary Conditions: Initial Flow Velocity Condition, Initial Pressure Condition, Flow Velocity Boundary Condition
- Geometrical Analysis Features: Plane Multi-Point Constraint, Section Print Feature, Local Coordinate System
- Mechanical Boundary Conditions and Loads: Fixed Boundary Condition, Rigid Body Constraint, Displacement Boundary Condition, Contact Constraint, Tie Constraint, Spring Boundary Condition, Force Load, Pressure Load, Centrifugal Load, Gravity Load
- Thermal Boundary Conditions and Loads: Initial Temperature, Heat Flux Load, Temperature Boundary Condition, Body Heat Source
- Overwrite Constants: Constant Vacuum Permittivity
- Mesh: Mesh From Shape by Netgen, Mesh From Shape by Gmsh, Mesh Boundary Layer, Mesh Refinement, Mesh Group, Erase Elements, FEM Mesh to Mesh
- Solve: Solver CalculiX, Solver Elmer, Solver Mystran, Solver Z88; Mechanical Equations: Elasticity Equation, Deformation Equation; Electromagnetic Equations: Electrostatic Equation, Electricforce Equation, Magnetodynamic Equation, Magnetodynamic 2D Equation, Static Current Equation; Flow Equation, Flux Equation, Heat Equation, Solver Job Control, Run Solver
- Results: Purge Results, Show Result, Apply Changes to Pipeline, Post Pipeline From Result, Pipeline Branch, Warp Filter, Scalar Clip Filter, Function Cut Filter, Region Clip Filter, Contours Filter, Glyph Filter, Line Clip Filter, Stress Linearization Plot, Data at Point Clip Filter, Calculator Filter; Filter Functions: Plane, Sphere, Cylinder, Box; Data Visualizations: Create Lineplot, Create Histogram, Create Table
- Utilities: Clipping Plane on Face, Remove All Clipping Planes, FEM Examples; Clear FEM Mesh, Display Mesh Info
- Additional: Preferences; FEM Install, FEM Mesh, FEM Solver, FEM CalculiX, FEM Concrete; FEM Element Types
- Начинающим
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