Hi Patrick,
Thanks for the notes.
I would not expect an even pressure distribution, both contacting surfaces are unconstrained and elastic. Ignoring friction for a moment, the contact pressure distribution will cause the green block to 'dome' with a lower pressure in the centre and the edges will dig in (I visualise it as a Gibb's effect). Cylindrical rolling elements in bearings have this problem and rather than rectangular cross section they can be given a curved profile (logarithmic) such that the pressure distribution remains linear-ish and peaks at the edges reduced/removed.
The top plate is hanging because is has moved 9mm in the first time step. This is not right. Movement has to begin at the loaded surface and 'propagate along' the structure (try dragging a carpet). In both models everything was in step 1.
The most bothersome thing at the moment is that the interface force and tan force measures are simply wrong (or a badly set up model coupled with poor interpretation).
ttfn