Reduced Thickness in General contact

[R.Eng]

Hi,
How can I solve this warning during forming of shell element?
Solver: Dynamic Explicit
Interaction: General Contact-Tangential behavior
Element: Shell Thk:12

 

[FEA way]

In some cases Abaqus automatically reduces contact thickness of shell elements to avoid self-intersections. The CTHICK variable will show you those reductions. And if you want to prevent them, you should adjust the mesh size, use Edit Interaction --> Surface Properties --> Surface thickness assignments or add the *Contact controls assignment, contact thickness reduction keyword described in the documentation.

 

[R.Eng]

Thank you so much.
Which surface should I Use? outer or inner as per picture?
What about scale factor and Thickness?

 

[FEA way]

You can use the Global surface (entire general contact domain) or the one that corresponds to problematic shell geometry.

By default original thickness is used but you can type THINNING (decreasing thickness, useful in sheet forming analyses) or specify value (to reduce initial overclosures or model surface coatings on solid elements).

Scale factor probably won't be needed here so you can leave the default value of 1. It's just another way of preventing overclosures.