Use the Penaltyfactor command to modify the penalty factor when using the Penalty method for solving contact events (see Properties for Body Interactions Folder for more information about the Penalty method and penalty factors). The default penalty factor of 0.1 is an empirical value which provides stable solutions in most cases, but in some cases you may want to adjust this number.
The format of the Penaltyfactor command is:
Penaltyfactor,ContactType,Value
ContactType can take the following values:
| ContactType Input | Description |
|---|---|
| Global | Changes the default penalty factor value. This is the value that will be used in all contact events, unless it is overruled by another non-global Penaltyfactor command. |
| Flex-Rig | Defines the penalty factor for contact of flexible contact nodes with rigid target faces. |
| Flex-Flex | Defines the penalty factor for contact of flexible contact nodes with flexible target faces (and vice-versa). |
| Rig-Rig | Defines the penalty factor for contact of rigid contact nodes with rigid target faces (and vice-versa). |
| Rig-Flex | Defines the penalty factor for contact of rigid contact nodes with flexible target faces. |
| Bonded | Defines the penalty factor for all bonded contact definitions in the model (default = 0.1) |
Note:
Global is usually the best choice. Using any value other than Global requires that you have a deep understanding of the solver behavior.
Bonded contact definitions are defined between nodes and faces of solid or shell elements. Typically the node lies in the plane of a face. If this is not the case, they are called offset bonded contact definitions. These offset bonded contacts (and sometimes also in-plane bonded contacts) may suffer from instability due to the fact that rotational movement is not considered. Typically this becomes visible through hourglassing of the underlying elements or nodes moving too fast in the bonded area (blowing up). A remedy for this phenomenon is to lower the penalty factor for the bonded contacts. A suggested value could be 0.01, although care should be taken that with a lower bonding force the surfaces may separate more than wanted.
Value is a real number greater than zero.
Note: There is no upper limit to this value. However, very large or very small values will lead to numerical instabilities. It is recommend that you choose a value less than 3.0. Setting the penalty factor to zero will cause sliding contact with incorrect behavior.
Any penalty factor you define will be sent to the solver and written out in the admodel.prt and admodel.xml files. However, the values actually used in the calculation of contacts will depend on the contact settings. For example, if you define an asymmetric flexible to rigid body contact, then only the FLEX-RIG value will be used.
The solve will stop if the penalty factor is less than zero or if there are multiple values defined for the same contact type.