When is it necessary to define contact?

[rm447]

Hello, this is a trivial question but when is it necessary to define contact? More specifically, if I have one single object (and meshed uniformly throughout) which has a core with a set of material properties different than the rest of it, would it be sufficient to define two different materials and and assign them to the two regions using *solid section? Would they separate under loading if no (tied) contact definition is included at the boundary where the properties switch over?
Thank you.

[Jorgen]

Based on your description it sounds like you do not need contact in that case.

In general, two elements that share nodes, do not need contact...

-Jorgen

[rm447]

Thanks That's what I needed to know.