Q) Could you tell me the detail difference between a surface-to-surface contact element and extended surface-to-surface contact element?
A)At first, in case of surface-to-surface contact element, the base surface is approximated by a triangular patches and the action body is represented by the every contact node at a set of multi-sphere (when you open the dialog box of contact element, you can easily see the small white points, that are called contact nodes at the action surface) In case of extended surface-to-surface contact element, the both surfaces (base & action) are approximated by triangular patches. For example, if you define the contact element, surface would be represented as shown figure according to contact element type.
