Add a Boundary to Boundary node to connect two shell boundaries that are geometrically disjoint. It is assumed that the boundaries are parallel to each other. The connection between corresponding points on the two boundaries can be rigid or flexible.

Select the coordinate system to use for specifying the stiffness in the case of a flexible connection. From the Coordinate system list select from:

Select the Method — Rigid or Flexible.

For Rigid, the coupling between the two boundaries is rigid in a pointwise manner. Every node on the destination boundary is coupled by a virtual rigid bar to the nearest point on the source boundary. This does not imply that the whole boundary is rigid, such type of coupling can be obtained using a Rigid Connector.

For Flexible, select the Connection properties — From material or User defined.

When data is taken From material, the elastic material properties of the Joint material are taken from the boundary material on the source side, or other material available in the Material node.

The default values of the Young’s modulus E, Poisson’s ratio ν, and Density ρ are taken From material. Select User defined to enter other values or expressions.

For User defined connection, enter the Spring constant per reference area. This is a matrix ku,A, coupling the displacements on the two sides.

Here, f is the force acting on the destination side, and Δu is the difference of the displacement of the destination and source sides. All vectors are expressed in the Coordinate System Selection.

Optionally, you can enter a Mass per reference area, ρu,A. This can for example be the mass of a glue layer.

Select Connected location — Automatic or Manual. In the automatic method, the two sides of the shells that are found to be closest to each other are connected. If you want to make another choice, or the if the automatic search for some reason does not give the intended result, select Manual.

In the manual method, the Source and Destination lists are shown. Select Top surface or Bottom surface from both lists.

Select the Connection tolerance — Automatic or User defined. For User defined, enter the maximum allowable distance or overlap between the boundaries, δ.

To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog.

Select the Search method — Closest point or Manual to specify what should happen if an evaluation point in the destination boundary is mapped outside the source boundary.

The Closest point method is the default and most robust search method. The closest point in the source selection is used by the mapping operator, even if that point is far away from the destination point. This method is not as efficient as the Manual method.

The Manual method is an alternative search method that is computationally efficient, but its robustness is determined by the curvature of the boundaries, the Search distance, and the Extrapolation tolerance. Specify the maximum search distance between the source and destination boundaries and the extrapolation tolerance.

To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog. The information in this section i sonly used if Method is set to Rigid.

Physics tab with Shell selected: