The Solid, Midsurface, and Solid / Midsurface options on the AutoGEM menu let you specify whether Creo Simulate will treat models that include midsurfaces as solid models, midsurface shell models, or a mixture of both during meshing and analysis. In the FEM mode, you can specify model treatment by selecting the mesh type on the Mesh menu.

In models that have no midsurfaces, the Solid option is turned on and the Midsurface and Solid / Midsurface options are deactivated. However, when you define shell pairs for your model, the software automatically activates these two options and turns on the Midsurface option. Provided that you keep the option on, Creo Simulate meshes and analyzes the model as a shell model. If any portion of the model is a solid, Creo Simulate omits that portion from the mesh and, consequently the analysis. If you want to include the solid portions of the model, turn on the Solid / Midsurface option instead.

For models with midsurfaces, the Midsurface option stays on by default unless you select one of the other two options and then save your model in that state. If you delete all the shell pairs in your model, Creo Simulate automatically turns off and deactivates the Midsurface and Solid / Midsurface options, reverting to the Solid option.