The only way to model sth. like a contact is thru gap elements. They work like a spring infinite stiffness when the parts have contact an without or extremely small stiffness if there is no contact.
But I would not recommend odelling contacts in Nastran. I prefer solvers like Permas or Abaqus.
Use the PARAM, BAILOUT, -1 Option to avoid the termination of the solution.With the result you can probably detect, what is wrong with your model, e.g. a lack of constraints.
ANSA is absolutely the best pre-processing tool in the world. It has the fastest mesher I,ve ever seen. You can easily build midsurface models, futhermore it has a really good tet-mesher.
For further information contact the software vendor www.lasso.de
