/INTER/TYPE23
Block Format Keyword Defines a contact interface for airbag fabrics, modeling contact between a main surface and a secondary surface which are supposed to belong to an airbag.
This is a soft penalty contact which can deal with penetrations and intersections often coming in the folded airbag mesh. This interface can be used for self-impacting.
Format
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
/INTER/TYPE23/inter_ID/unit_ID | |||||||||
inter_title | |||||||||
surf_IDs | surf_IDm | Istf | Igap | Ibag | Idel | ||||
Fscalegap | Gapmax | Fpenmax | |||||||
Stmin | Stmax | ||||||||
Stfac | Fric | Gapmin | Tstart | Tstop | |||||
IBC | Inacti | VISs | Bumult | ||||||
Ifric | Ifiltr | Xfreq |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
C1 | C2 | C3 | C4 | C5 |
(1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) |
---|---|---|---|---|---|---|---|---|---|
C6 | |||||||||
Blank | |||||||||
Blank | |||||||||
Blank |
Definition
Field | Contents | SI Unit Example |
---|---|---|
inter_ID | Interface identifier. (Integer, maximum 10 digits) |
|
unit_ID | Unit Identifier. (Integer, maximum 10 digits) |
|
inter_title | Interface title. (Character, maximum 100 characters) |
|
surf_IDs | Secondary surface
identifier. (Integer) |
|
surf_IDm | Main surface
identifier. (Integer) |
|
Istf | Stiffness definition flag.
(Integer) |
|
Igap | Gap/element option flag. 3
(Integer) |
|
Ibag | Airbag vent holes closure flag in case
of contact.
(Integer) |
|
Idel | Node deletion flag.
(Integer) |
|
Fscalegap | Gap scale factor. Default = 1.0 (Real) |
|
Gapmax | Maximum gap.
(Real) |
|
Fpenmax | Maximum fraction of initial penetration.
4 (Real) |
|
Stmin | Minimum stiffness. (Real) |
|
Stmax | Maximum stiffness. Default = 1030 (Real) |
|
Stfac | Interface stiffness (if Istf = 1). Default set to 0.0 (Real) |
|
Stiffness scale factor for the interface
(if Istf = 0). Default = 1.0 (Real) |
||
Fric | Coulomb friction. (Real) |
|
Gapmin | Minimum gap for impact
activation. (Real) |
|
Tstart | Start time. (Real) |
|
Tstop | Time for temporary
deactivation. (Real) |
|
IBC | Deactivation flag of boundary conditions
at impact. (Boolean) |
|
Inacti | Stiffness deactivation flag of stiffness
in case of initial penetrations. 4
(Integer) |
|
VISs | Critical damping coefficient on
interface stiffness. Default set to 1.0 (Real) |
|
Bumult | Sorting factor. 5
6
Default set to 0.20 (Real) |
|
Ifric | Friction formulation flag. 8
9
(Integer) |
|
Ifiltr | Friction filtering flag. 10
(Integer) |
|
Xfreq | Filtering coefficient. A value should be between 0 and 1. (Real) |
|
C1 - C6 | (Optional) Friction law
coefficient. (Real) |
See Table 1 |
Flags for Deactivation of Boundary Conditions: IBC
(1)-1 | (1)-2 | (1)-3 | (1)-4 | (1)-5 | (1)-6 | (1)-7 | (1)-8 | (1)-9 | (1)-10 |
---|---|---|---|---|---|---|---|---|---|
IBCX | IBCY | IBCZ |
Definition
Field | Contents | SI Unit Example |
---|---|---|
IBCX | Deactivation flag of X boundary
condition at impact.
(Boolean) |
|
IBCY | Deactivation flag of Y boundary
condition at impact.
(Boolean) |
|
IBCZ | Deactivation flag of Z boundary
condition at impact.
(Boolean) |
Comments
- For contact stiffness:
if Istf = 0.
While,
is an equivalent nodal stiffness of the secondary component computed as:
when node is connected to a shell element.
Where,- Young's modulus
- Bulk modulus of the secondary component
- Shell thickness
- Solid element volume
- If Gapmin is not specified or set to zero, a default value is computed as the minimum of (average thickness of the secondary shell elements).
- If Igap = 1, variable gap is
computed as:
(1) While,
gs: secondary node gap:
with is the largest thickness of the shell elements connected to the secondary node.
If the secondary node is connected to multiple shells, the largest computed secondary gap is used.
The variable gap is always at least equal to Gapmin.
- Inacti = 6 is recommended, in
order to avoid numerical (high frequency) effects into the interface before inflation.
If Inacti = 5 or 6 and if Fpenmax is not equal to zero, nodes stiffness is deactivated if:
(2) - The sorting factor, Bumult is used to speed up the sorting algorithm.
- The sorting factor Bumult is machine dependent.
- One node can belong to the two surfaces at the same time.
- For friction formulation
- If the friction flag Ifric = 0 (default), the old
static friction formulation is used:
with ( is Coulomb friction coefficient).
- For flag Ifric > 0, new friction
models are introduced. In this case, the friction coefficient is set by a function
Where,
- Pressure of the normal force on the main segment
- Tangential velocity of the secondary node relative to the main segment
- If the friction flag Ifric = 0 (default), the old
static friction formulation is used:
- Currently, the coefficients C1 through C6 are used to define a variable friction
coefficient
for new friction formulations.The following formulations are available:
- Ifric = 1 (generalized
viscous friction law):
(3) - Ifric = 2 (Modified
Darmstad law):
(4) - Ifric = 3 (Renard law):
if
if
if
Where, - First critical velocity must be different to 0 ( ).
- First critical velocity must be lower than the second critical velocity ( ).
- The static friction coefficient and the dynamic friction coefficient , must be lower than the maximum friction ( and ).
- The minimum friction coefficient
Table 1. Units for Friction Formulations Ifric Fric C1 C2 C3 C4 C5 C6 1 2 3 - Ifric = 1 (generalized
viscous friction law):
- Friction filteringIf Ifiltr ≠ 0, the tangential forces are smoothed using a filter:
(5) Where,- Filtered tangential force
- Calculated tangential force at time before filtering
- Filtered tangential force at the previous time step
- Current simulation time
- Current simulation time step
- Filtering coefficient
- The type of friction penalty formulation is
based on the incremental stiffness formulation:The friction forces are:
(6) While an adhesion force is computed as:
with
Where, is the tangential velocity of the secondary node relative to the main segment.