About Interfaces
Use interfaces to connect coincident components or surfaces in a model. When you create an interface, you specify how Creo Simulate will treat a particular pair of mated or overlapping surfaces during meshing and analysis. You can create different types of interfaces to connect coincident components or surfaces. Sometimes Creo Simulate creates default interfaces in a model while meshing the model or running an analysis.
Creo Simulate can create interfaces for the following types of entity pairs:
• Solid—solid
• Solid—shell
• Solid—midsurface
• Shell—shell
• Shell—midsurface
• Midsurface—midsurface
• Quilt—quilt(FEM mode only)
• Quilt—solid (FEM mode only)
If your assembly includes components modeled with midsurfaces, Creo Simulate compresses these components during meshing, potentially creating gaps in the assembly. To prevent these assembly gaps, Creo Simulate creates automatic midsurface connections where the original surfaces of midsurface components mate or overlap with surfaces from other assembly components.
To create an interface between any two components or surfaces in your model, click > 
Interface to open the Interface Definition dialog box.
Interface to open the Interface Definition dialog box.Creo Simulate automatically creates interfaces between all mated components of an assembly during meshing and analysis. To set the default type of this automatically created interfaces, click > 
Model Setup to open the Model Setup dialog box and set the default interfaces.
Model Setup to open the Model Setup dialog box and set the default interfaces.For each type of interface, Creo Simulate automatically creates some interface measures to monitor various aspects of the interface. However, Creo Simulate does not create any interface measure for the default interfaces that are created automatically during meshing and analysis.