Large plastic deformation of a thin plate

[Nelso]

Hi everyone,

i'm analysing a screwjoint in abaqus cae 6.5.
Its a joint with two thin plates of aluminium connected by a self-tapping screw.
To determine the shearforce-resistance of the joint the two plates are applied with a deformation of 3mm among eachother. After 1mm there are very large plastic deformations at the thinner plate an it becomes thicker so the resistance grows further. In reality the screw cuts the thinner plate and does not push the whole material in front of it. Does anyone know how to handle this problem ?

Thanks very much for any help
Greets from Europe
Nelso