Modeling shell thickness in ABAQUS/STANDARD

[dahste]

Hi,

I am modeling a assembly with two sheet metal parts that are joined together with spotwelds. In order to incorporate the sheet metal thickness, I use:

*CONTACT INTERFERENCE, OP=NEW, TYPE=CONTACT PAIR
under, upper, -1.35

When the parts are in contact the clearance between the parts should be 1.35 mm. But when I check the result the parts have zero clearance??

Thanks!