Interface between a shell and a 3D domain element

I'm curious if anyone has any experience with the preferred way to couple the physical mechanical stress and strains between a 3D domain and a shell.

This MEMs problem consists of a very thin Si3N4 plate spanning a large trench etched in silicon. Early attempts which treated the span as a domain were of limited success so the next approach is to treat the Si3N4 as a span and interface it with the subdomain of the silicon substrate at teach end of the trench.

The 3D geometry model forms the silicon substrate with a very long and wide trench. A workplane is then added to create a geometry rectangle that becomes a shell.

Two Physics sets are added. The first is the 'Shell' and the second is a 'Solid Mechanics'. The difficulty I'm having is the coupling the displacements and forces from the silicon substrate domain to the shell. After some study the approach that seemed most viable was to create an 'assembly' rather than a 'union' and to create Identity Pairs for the needed physical coupling. It would seem that using 'Shell/Pairs/Continuity' would be the approach but the Identity pairs are not available for selection.

So, looking to the SolidMechanics/paris/continuity I find that only one end of the pairs is available.

I'm certainly open to suggestions on a better approach for this coupling.



Thanks,
Marty