Definition

A monitored volume is defined with one or more shell (3-node or 4-node) parts.

The defined surface must be closed (RADIOSS Starter checks it and outputs an error message, if the surface is not closed). The shells normal must be oriented outside the volume. It is possible to reverse the shells normal for a given part, set by entering a negative part number (or by using an appropriate pre-processor to reverse them).

Three types of monitored volume may be used to model airbags:

The FVMBAG type may be used for curtain bag for an Out Of Position (OOP) situation where the gas flow effects must be taken into account.

The properties and material laws used to model the fabric could be:

Either /MAT/LAW19 + /PROP/SH_ORTH - Used to model a fabric with a linear elastic behavior,

Or /MAT/LAW58 + /PROP/SH_FABR - Used to model the behavior of a nonlinear elastic fabric.

The behavior of the fabric is only a membrane one, therefore one integration point through the thickness is recommended. The fabric may be modeled with 3-nodes shell element, C0 without hourglass or with 4-nodes shell improved Belytschko formulation (Ishell =4); to avoid hourglass, the shell membrane hourglass coefficient hm and the shell out of plane hourglass hf should be set to 10%.

To define communicating surface for the COMMU type monitored volume, dummy properties (/VOID) and dummy materials (/VOID) may be used.

Generally to define an interface self-impact contact, you may define one self-impacting interface TYPE7 and one edge-to-edge interface contact TYPE11. If there are some initial penetrations, then set Inacti =5.