3D Indenter Problem

[Mcmathews]

I am trying to model an AFM tip pressing down on the center of a circular membrane. The AFM indenter is an analytical sphere and the membrane is clamped around the perimeter. These parts have surface-to-surface contact. I am applying a displacement to the AFM tip.

My problem is that I am getting the following warnings that ultimately result in an error:

***WARNING: THE SYSTEM MATRIX HAS 31081 NEGATIVE EIGENVALUES.
***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE
MEMBRANE-1.3306 D.O.F. 1 RATIO = 310.855E+09 .

The nodes it gives error messages for are actually usually half way in between the edges and the center of the circle.

Any Suggestions?

 

[rstupplebeen]

If you upload the CAE file you may get more help.

Is your model axisymmetric, implicit?

Hopefully I'll be more help later.

Rob

Thank you.

Rob Stupplebeen
OptimalDevice.com
My Personal WP