FEM: Vincolo contatto
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| Modello → Vincoli meccanici → Vincolo contatto |
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Descrizione
Crea un vincolo FEM di contatto tra 2 superfici.
The FEM contact task panel
Utilizzo
Contact example - rigid cube pressed against and sliding on a deformable block. Without contact definition, those two parts wouldn't "see" each other.
Limitazioni
- Il vincolo contatto può essere applicato solo a due facce.
- Sviluppo per più contatti contemporaneamente: https://forum.freecad.org/viewtopic.php?f=18&t=15699&start=130#p303275
Properties
- DatiSlope: Contact stiffness.
- DatiAdjust - introduced in 1.0: Node clearance adjustment limit.
- DatiFriction - introduced in 1.0: Enable frictional contact.
- DatiFriction Coefficient: Coefficient of friction.
- DatiStick Slope - introduced in 1.0: Stick slope.
- DatiEnable Thermal Contact - introduced in 1.1: Enable thermal contact.
- DatiThermal Contact Conductance - introduced in 1.1: Thermal contact conductance [mW/(mm^2*K)] specified as a list in the following format (contact pressure and temperature dependency can be skipped and only one entry provided to define a constant gap conductance):
conductance_1, contact_pressure_1, temperature_1 …
- DatiSurface Behavior - introduced in 1.1: Contact behavior in the normal direction:
- Linear - default behavior with the specified stiffness
- Hard - hard contact (default constants calculated by the solver)
- Tied - tied (bonded) contact, requires non-zero friction
Notes
Tips for modeling
Note
Alcuni consigli su come modellare
- Da https://forum.freecad.org/viewtopic.php?f=18&p=340874#p340494
- Meglio utilizzare elementi lineari altrimenti i calcoli richiedono molto tempo
- assegnazione master/slave:
- La superfici più grande dovrebbe fungere da superficie principale.
- Se le superfici hanno dimensioni simili, la superficie del corpo più rigido dovrebbe fungere da superficie principale.
- Se le superfici hanno dimensioni e rigidità simili, la superficie con la maglia più grossolana dovrebbe fungere da superficie principale.
CalculiX
CalculiX
- La rigidezza del contatto dovrebbe essere 10 volte il modulo di Young del materiale per avere un contatto forte. Più alto è il valore di rigidezza di contatto, più è forte il contatto tra le superfici.
- La faccia secondaria è la faccia che penetra nella faccia principale, e subisce quindi una deformazione maggiore.
- Il vincolo contatto utilizza la *CONTACT PAIR card in CalculiX. Il vincolo usa il metodo Face-to-Face penalty e la formulazione del contatto è spiegata in dettaglio in http://web.mit.edu/calculix_v2.7/CalculiX/ccx_2.7/doc/ccx/node112.html
- Panoramica per diversi tipi di contatto: https://forum.freecad.org/viewtopic.php?f=18&t=15699&start=90#p188736
- Ulteriori informazioni interessanti:
- Un esempio molto dettagliato di contatto CalculiX. (link)
- Un esempio molto interessante nel subforum tedesco. (link)
- 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
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- 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
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