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Contact interface type 7 parameters? [SOLVED]

Altair Forum User

I have the following understanding about the parameteres:

1. Igap - defines the type of gap, always use 4

2. Idel - did not understand anything, please elaborate

3. FRIC - Is this co-efficient of static friction?

4. Gapmin - minimum distance between the master and slave surfaces that will always be kept? So shouldn't gap always be zero so that they are actually in contact instead of having a gap?

5. Inacti - did not understand anything, please elaborate

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Altair Forum User

Interface 7 is a multipurpose contact. The node set will be the slave and the surface set will be the master.

Gapmin - Minimum gap for impact activation. Type 7 interfaces have a gap that determines when contact between two segments occurs. This gap is user defined. The gap will allow to distinguish the impact. The contact will be activated when the distance between node to surface is less than gap.

Igap - If Gapmin is not provided, the contact activation gap can be provided using IGap. If Igap =1, gap will be computed as Gap (master) + Gap (slave), where Gap master will be gm = t/2, t is the thickness of the master element for shell elements and similarly for slave. The the gap will be directly assigned from the property.
Similarly other flags can be seen in the Help Menu.

FRIC - Type 7 interface allows sliding between contact surfaces and coulomb friction between the surfaces is modelled. No value (default) defines zero friction between the surfaces.

Inacti - Type 7 interface is very sensitive to initial penetrations. Inact is used to auto correct the initial penetrations happening due to the defined contact.One method for solving the resulting problems is to use Inacti = 6, where it will automatically depenetrate. When using Inacti =1, the penetrating nodes are deleted from the modelThe correction is only applied to the initially penetrated nodes. The various flags for reducing the initial penetrations in contact using Inacti can be reffered in Help Menu.

Idel - During contacts, when elements are deleted, using this option the segment can be removed from the interface. Using 1 option, when all the elements associated to one segment (master/slave) are deleted, the segment is deleted from interface. Where as for 2, it will be deleted if any one element is deleted from segment.

Altair Forum User

George, does this gap mean the physical gap that will be kept constant throughout, or this is just an indicator for RADIOSS to start looking for contact algorithms upon reaching Gapmin? My confusion is whether this gap is kept between the 2 surfaces, or it is just a timer for beginning the contact looking algorithm and no gap is actually kept? Is the FRIC for static or kinetic friction? Idel - what is the segment you are talking about?

Altair Forum User

This Gapmin is for RADIOSS to activate contact upon reaching Gapmin. This is not the physical gap to be kept. Default static friction formulation is used. By changing the Ifric flag this formulations can be changed. The various flags and the formulations for this is listed in the help menu. In Idel, the corresponding elements from the interface (segment) will be deleted.

Altair Forum User

I get it now, thank you very much George!