Fallback Conditions to Contact Regions
In the Solid Mechanics, Shell, and Membrane interfaces, certain boundary conditions may act as fallback conditions to a contact region, or any pair region, if their selection overlaps with the source and destination boundaries. The Layered Shell interface does not support any fallback conditions. When a boundary condition is considered as a fallback, the condition is only active for regions that are not in contact.
In the Solid Mechanics interface, the following boundary conditions are by default recognized as fallback conditions if their selection intersects any source and destination boundary:
In the Shell and Membrane interfaces, the following boundary conditions can be recognized as fallback conditions:
To enable the fallback condition in these nodes, change the Allowed region to Fallback and nonpair regions in the Applicable Pair Regions section of settings window of the node. To display the Applicable Pair Regions section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog box.
The most common case when a fallback condition is used is when there is a pressure load acting on the part of the boundary that is currently not in contact. In this case you would add a Boundary Load or Face Load with a selection that intersects with the source and destination boundaries.