Penetration in frictional contact

[Daniele1989]

Hi everyone,
i have a question about "frictional contact" (0.3). I have a pressure inside a chamber that makes a volumetric expansion of the wall.

Where red highlighted there's pressure 4MPa.
The higher and lower component are in structural steel, the middle one in PA.


This is the result of Equivalent Stress:

According to you, why there's penetration between plastic and steel components?

Thank you all!!

 

[karachun]

Maybe due to contact algorithm. Read from p.4. Link
In addition, contact may not work due to selection of master/slave contact surfaces. You can switch contact surfaces or change contact algorithm to Normal Lagrange.