Midsurfacing with thin layers

Hi all,

 

I want to run a Radioss analysis of a layered structure under impact. As my layers are too thin to be modeled with 3D elements, I want to use midsurfacing tool. Relative to that, I have 2 questions: 

 

1. One thing I ask myself since the beginning of using midsurface is : should I translate the components relatively to the new midsurface ? ie. if a ball impacts a table, should I translate the midsurface of the table up, to make contact at the right time ? I would say you do not have to translate it as you indicate the thickness, but in my simulations, contact does not begin (vonMises stress = 0 ) before I can visually detect it. So I always translate my components, though it seems weird to me...

 

2. As I said, I want to model a structure comprised of different sheets of materials, which I would like to model as 2D elements.

Problem :  - At first, my 3D components are in contact (if it had been a 3D mesh, I would have liked to have a continuous mesh)

                 - When I do the midsurface for each sheet, they have a gap; which is normal but which I wonder about : I suppose I should not translate my midsurfaces, however contact is not detected and I would like to use continuous meshing instead of interface option.

 

 

Hope that was clear enough. If you can give me some answers to my questions, it would be very helpful.

 

Thank you in advance,

Alice