Use a General Contact Pair node () to specify a contact interaction between multiple objects. A general contact pair defines boundaries of parts in an assembly that can come into contact under deformation. The pair establishes a mapping between these boundaries by performing a contact search. For more information about mechanical contact modeling, see the Structural Mechanics Module documentation.

The default Pair type is General contact pair, or you can select Identity pair, Contact pair, or Sector symmetry pair. See Pair Type for more details.

The general contact pair automatically creates source and destination boundaries from the exterior boundaries of the parts included in the pair as controlled by the Selection list. By default, All objects from the current geometry are included. Choose Manual from the Selection list to select domains and boundaries to be included in the pair. The source and destination boundaries are then set up from the union of the exterior boundaries of the selected domains and the selected boundaries.

When the Selection list in the contact selection section is set to Manual, select domains to include in the general contact pair. The exterior boundaries of the selected domains are included in the source and destination boundaries of the pair.

From the Selection list, choose Manual, All domains, or any other available selection. If Manual is selected, click in the Graphics window to add domains to the Selection section. Click the Activate Selection button to toggle between turning ON and OFF selections directly in geometry, for example. Such selections also become active when you choose Manual from the Selection list.

When the Selection list in the contact selection section is set to Manual, select boundaries to include in the general contact pair. Boundaries may either be adjacent to a domain or free.

From the Selection list, choose Manual, All boundaries, or any other available selection. If Manual is selected, click in the Graphics window to add boundaries to the Selection section. Click the Activate Selection button to toggle between turning ON and OFF selections directly in geometry, for example. Such selections also become active when you choose Manual from the Selection list.

The Mapping method list is by default set to Deformed configuration. This setting means that whenever objects included in the pair has moved, a new search for possible contact points is made. If you know that the movements are small, selecting Initial configuration can be more efficient. In this case, a mapping is computed for all points based on the initial configuration and always stays the same. This approach works well if the distance between all objects is initially small, and movements in the tangential direction are small.

A contact search is performed for each destination point by searching for mesh elements in the source that are within the search distance. The mesh element closest to the destination is used to set up the contact mapping. By default, the search distance is determined automatically as three times a characteristic size of the mesh element of the destination point. To tune it manually, choose Manual or Tolerance from the Search distance list.

You can use the Extrapolation tolerance setting (a fraction of the element length; default 10−4) to effectively extend the source slightly outside its selection. The size of this extension is equal to the extrapolation tolerance multiplied with the mesh element size.

The general contact pair allows for objects to self-intersect such that a mapping is possible between points that belong to the same geometric object, including the same boundary. To avoid unwanted mappings, the contact search algorithm performs checks when initializing the solver. Mesh elements that belong to the same geometric object as the destination point and are closer than a multiple of the search distance in the initial configuration are excluded when finding a valid mapping. For large and complex assemblies this check can be expensive. To reduce the cost, the automatic behavior includes optimizations that can be turned off by choosing Exhaustive form the Self-intersection check list. The check can also be disabled by choosing Ignore from the same list.