Airbag Setup Recommendation

Airbag Materials

Recommendations for fabric material model setup using LAW19.
LAW19 Option Recommended Value Recommended Option Details
RE 0.001 < RE < 0.01 If RE > 0.01 the compression stiffness is too high.
ZeroStress 1 Airbag pre-strain is applied correctly.
sens_ID Use the same sensor as used in /MONVOL card Fabric pre-strain through reference geometry must be activated at time to fire.
Recommendations for fabric material model setup using LAW58.
LAW58 Option Recommended Value Recommended Option Details
B1 and B2 > 0 B1 and B2 values should be positive.
Flex 0.01 The default value is adequate.
G0 < GT -- Shear parameters should be consistent.
α T MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaaeaaaaaaaaa8 qacqaHXoqypaWaaSbaaSqaa8qacaWGubaapaqabaaaaa@38E9@ Enter value in degrees Shear locking angle shall be entered in degrees.
ZeroStress 1 Airbag pre-strain is applied correctly.
sens_ID Same sensor that is used in /MONVOL card Fabric pre-strain through reference geometry must be activated at time to fire.

Airbag Properties

Recommendation in fabric properties /PROP/TYPE9 (SH_ORTH) and /PROP/TYPE16 (SH_FABR).
Property Option Recommended Value (per material) Recommended Option Details
LAW19 1 LAW58 2
Ish3n for trias 2 2 This is the default tria formulation.
Ismstr for trias 1 4 Best practice recommendation for 3 node trias
Ishell for 4-node shells 12 12 This formulation avoids hourglassing.
Ismstr for 4-noded shells 11 11 Must be used with Ishell =12, 4 node shells.
N 1 1 Enable membrane formulation
Thick > 0 > 0 Thickness must be defined
Iplas 0 0 Not relevant for fabric
Ithick 0 0 Not relevant for fabric
Vx, Vy, Vz Non-zero vector Non-zero vector This input defines a vector which determines first orthotropy direction. If not defined the Global X- axis is used.
Idril 0 0 Not relevant for fabric

Airbag Self-Contact

If all intersections can be removed from the airbag, then surface to surface and edge contact and be defined using /INTER/TYPE19. In some advanced cases, it is better to define the two separate contacts, /INTER/TYPE7 for node to surface and /INTER/TYPE11 for edge contact.
Interface Options Recommended Value for contacts TYPE7, TYPE11 and TYPE19 Comments
Intersections No intersections No intersections are allowed.
Penetrations Penetrations < 95% gap All penetrations > 95% gap need to be removed.
Istf 4 Interface stiffness is the minimum of the main and secondary stiffness.
Stmin (kN/mm) 1 Avoids contact that is too soft.
Idel 0 Not relevant for airbag self-contact.
Igap 0 Constant gap is used as defined by Gapmin.
Gapmin 1.0 mm For TYPE11, use Gapmin =0.9mm
Inacti 6 Automatically remove initial penetrations by reducing the contact gap.
Fric 0 No friction used in airbag self-contact.
Ibag 1 Block vent holes and porous fabrics during contact.
If it is not possible to remove intersections, then /INTER/TYPE23 can be used with these recommended values.
Interface Options Recommended Value for TYPE23 Comments
Penetrations Penetrations < 95% gap All penetrations > 95% gap need to be removed.
Istf 4 Interface stiffness is the minimum of the main and secondary stiffness.
Idel 0 Not relevant for airbag self-contact.
Igap 0 Constant gap is used as defined by Gapmin.
Gapmin Thickness of fabric material This value determines both contact gap and contact depth, too high values will mean that intersected nodes will not be released due to too high contact depth.
Inacti 6 Automatically remove initial penetrations by reducing the contact gap.
Fric 0 No friction used in airbag self-contact.
Ibag 1 Block vent holes and porous fabrics during contact.
1 Fabric material LAW19 is only compatible with /PROP/TYPE9 (SH_ORTH).
2 Fabric material LAW58 is only compatible with /PROP/TYPE16 (SH_FABR).