/FRICTION
Block Format Keyword Specific contact friction between groups of parts or two parts. This friction definition overwrites the friction model defined in the contact interface for the defined set of interfaces.
This friction model is compatible with contact interfaces: TYPE7, TYPE11, TYPE19, TYPE24 and TYPE25.
Format
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
/FRICTION/fric_ID/unit_ID | |||||||||
friction_title | |||||||||
Ifric | Ifiltr | Xfreq | Iform |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
C1 | C2 | C3 | C4 | C5 | |||||
C0 | Fric | VISF |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
grpart_ID1 | grpart_ID2 | part_ID1 | part_ID2 | Idir | |||||
C1 | C2 | C3 | C4 | C5 | |||||
C6 | Fric | VISF |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
C1 | C2 | C3 | C4 | C5 | |||||
C6 | Fric | VISF |
Definitions
Field | Contents | SI Unit Example |
---|---|---|
fric_ID | Friction
identifier (Integer, maximum 10 digits) |
|
unit_ID | Unit Identifier (Integer, maximum 10 digits) |
|
friction_title | Friction model
title (Character, maximum 100 characters) |
|
Ifric | Friction formulation flag.
1
(Integer) |
|
Ifiltr | Friction filtering flag.
5
(Integer) |
|
Xfreq | Filtering
coefficient. This coefficient should have a value between 0 and 1. Default = 1.0 (Real) |
|
Iform | Friction penalty
formulation type. 6
(Integer) |
|
C1 | Friction law
coefficient. (Real) |
|
C2 | Friction law
coefficient. (Real) |
|
C3 | Friction law
coefficient. (Real) |
|
C4 | Friction law
coefficient. (Real) |
|
C5 | Friction law
coefficient. (Real) |
|
C6 | Friction law
coefficient. (Real) |
|
Fric | Coulomb
friction. (Real) |
|
VISF | Critical damping
coefficient on interface friction. 4 Default = 1.0 (Real) |
|
grpart_ID1 | Part group identifier.
/GRPART for the first
set. (Integer) |
|
grpart_ID2 | Part group identifier
/GRPART for the second
set. (Integer) |
|
part_ID1 | Part identifier
1. Ignored if grpart_ID1 is defined. (Integer) |
|
part_ID2 | Part identifier
2. Ignored if grpart_ID2 is defined. (Integer) |
|
Idir | Orthotropic friction flag
for a couple of parts.
(Integer) |
Comments
- The friction defined in /FRICTION overrides any friction defined in the contact interface.
- Default values listed in the first section are used for any parts whose friction is not specifically defined in the repeating section using grpart_ID1, grpart_ID2, part_ID1, and part_ID2.
- If friction between parts is defined more than one time in the model, the friction defined in the last position are used.
- The friction value
is defined.
- Ifric = 0 (Coulomb friction):
(1) - Ifric = 1 (Generalized Viscous Friction law):
(2) Where,- Pressure of the normal force on the master segment
- Tangential velocity of the slave node
- Ifric = 2 (Modified Darmstad law):
(3) Where,- Pressure of the normal force on the master segment
- Tangential velocity of the slave node
-
- Ifric = 3 (Renard law):
(4) (5) (6)
Where,- First critical velocity must be different to 0 ( ).
- First critical velocity must be less than the second critical velocity .
- The static friction coefficient and the dynamic friction coefficient , must be less than the maximum friction ( and ).
- The minimum friction coefficient must be less than the static friction coefficient and the dynamic friction coefficient ( and ).
Table 1. Units of Friction Formulation Ifric Fric C1 C2 C3 C4 C5 C6 1 2 3 - Ifric = 3 (Renard law):
- Ifric = 0 (Coulomb friction):
- Friction filteringIf Ifiltr ≠ 0, the tangential forces are smoothed using a filter:
(7) Where, α coefficient is calculated from:- If Ifiltr = 1: , simple numerical filter
- If Ifiltr = 2: , standard -3dB filter, with , and T = filtering period
- If Ifiltr = 3: , standard -3dB filter, with Xfreq = cutting frequency
The filtering coefficient Xfreq should have a value between 0 and 1.
- Friction penalty formulation Iform:
- If Iform = 1 (default) viscous formulation, the friction
forces are:
(8) While an adhesion force is computed as:(9) - If Iform = 2, stiffness formulation, the friction forces
are:
(10) While an adhesion is computed as:(11) Where, is the contact tangential velocity.
Iform = 2 is recommended for implicit and low speed impact explicit analysis.
- If Iform = 1 (default) viscous formulation, the friction
forces are:
- Orthotropic friction for shell
elements, if Idir = 1.
- Two sets of friction coefficients must be defined after the line that contains Idir
- The orthotropic directions are defined only on the master contact surface
- The 2 ways to define the orthotropic friction direction
- Use the orthotropic direction from the shell element as defined
in /PROP/TYPE9,
/PROP/TYPE10,
/PROP/TYPE11,
/PROP/TYPE17,
/PROP/TYPE51, or
/PROP/PCOMPP.
Direction 1 from element.
Direction 2 is orthogonal to Direction 1 in the segment plane.
- Use Direction 1 defined from the vector and angle defined in /FRIC_ORIENT.
- Use the orthotropic direction from the shell element as defined
in /PROP/TYPE9,
/PROP/TYPE10,
/PROP/TYPE11,
/PROP/TYPE17,
/PROP/TYPE51, or
/PROP/PCOMPP.
- Not supported for solid element, beam, truss or spring elements or edge to edge contact.