Airbag Internal Contacts
External and internal airbag components including inter-chamber voids and void components used for vents should not have any geometrical intersections.
A combination of /INTER/TYPE7 and /INTER/TYPE11 contact should be used to represent internal airbag contact.
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/INTER/TYPE7/666700001
Airbag Selfcontact - 666700001
# Slav_id Mast_id Istf Ithe Igap Ibag Idel Icurv Iadm
666100103 666100101 4 0 0 1 0 0 0
# GAP_SCALE GAP_MAX Fpenmax
0 0 0
# STMIN STMAX %MESH_SIZE dtmin
1 1E30 0 0
# STFAC FRIC GAP_MIN Tstart Tstop
1 0 1 0 0
# I_BC INACTI VIS_S VIS_F BUMULT
000 6 0 0 0
# Ifric Ifiltr Xfreq Iform
0 0 0 2
/SURF/PART/666100101
Airbag External Surface by Part - 666100101
666000001 666000002 666000003 666000004 666000005 666000006 666000007 666000008 666000009 666000013
666000014 666000015 666000016 666000017 666000018 666000201 666000202 666000203
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- All external and internal fabric components including inter-chamber voids and void components for vents should be defined in a self-contact where the components are listed as secondary nodes and main surfaces
- Istf=4 provides correct contact stiffness
- Ibag=1 provides vent closure due to contact
- Stmin=1KN/mm limits smallest contact stiffness
- Gapmin=1mm provides a smooth increase of contact force as secondary nodes are approaching main segment
- Friction is set to 0
- Inacti=6 deactivates initial penetrations
Initial penetration can be checked with HyperCrash's penetrations checker. The airbag model should be depenetrated up to the physical thickness of airbag fabric. For example, if the thickness of airbag fabric is 0.3mm, the airbag should be depenetrated to 30% of Gapmin = 1 value.
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/INTER/TYPE11/666800001
Airbag Selfcontact Edge - 666800001
# Slav_id Mast_id I_stf I_gap Multimp Idel
666100102 666100102 4 0 0 0
# STmin STmax MESH_SIZE dtmin Iform Sens_Id
1 0 0 0 2 0
# STFAC FRIC GAP Tstart Tstop
1 0 0.9 0 0
# I_BC INACTI VIS_S VIS_F BUMULT
000 6 0 0 0
/LINE/SURF/666100102
Airbag Line by Surface - 666100102
666100101
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- All external and internal fabric components including inter-chamber voids and void components for vents should be listed both on secondary and main side
- Istf=4 provides correct contact stiffness
- Stmin=1KN/mm limits smallest contact stiffness
- Gapmin=0.9mm provides a smooth increase of contact force as secondary nodes are approaching main segment. This contact gap is 90% of /INTER/TYPE7 contact gap
- Friction is set to 0
- Inacti=6 deactivates initial penetrations
Initial penetration can be checked with HyperCrash penetrations checker. The Airbag model should be depenetrated till 90% of Gapmin value which would result in a maximum penetration of 10% of the Gapmin value.
Assuming there are no initial intersections in the model, the definition of a TYPE7 and TYPE11 contact prevent node-to-surface and edge-to-edge intersections during airbag simulation. If initial intersections do exist in the model, the model can be unstable because nodes can be stuck on the wrong side of a main surface. In addition to this, the finite volume mesh cannot be created when airbag components have intersections. Therefore, it is important to remove all initial intersections.