In abaqus, there is an option “allow separation after contact”.
this is tricky sometimes:
if tick off means “not allowed to separate After contact”:
(1) if use exactly same node between master and slave, abaqus think it is contacted even if there is not initial stress, then it will not separate as specified;
(2) if use difference nodes, abaqus may think some part is not contacted, then it will still be “separated” in the analysis!!!!