Hi John, thanks for your suggestion.
I did the modification you suggested and what I see now is that wear works effectively. The order of magnitude of displacements is now as expected and the wear-induced displacement growth is progressive, whereas I had constant displacements before the modification.
What I cannot understand is that as soon as I define the second contact and I kill it at LS1, I get a higher wear rate, and consequently a bigger final displacement (max from 4 mm to 7 mm). Needless to say, I use the same constants to define the wear behaviour as in the case of single contact analysis. In addition, even if I set the wear constant of the second (killed) contact to 0, I get bigger displacements.
EDIT: the increased wear rate is due to increased contact pressure. I do not see the reason for this pressure increase, though. The second contact is killed before LS1 “SOLVE” command.