Simple Contact Mechanics Problem

Hi All,

I have been struggling a little with trying to implement a contact mechanics.

I am modelling indentation of a hybrid polymer base layer in 2D. The polymer base layer is a combination of two materials:polyimide (PI) and PDMS and the probe is rigid metal probe with a spherical tip. The boundary condition is a pressure (50 kPa) applied to the top surface of the probe. At the moment I am using Linear elasticity just so I can can it to solve first but with use hyperelastic law subsequently.

I have selected 2 contact pairs: (1) the probe and the top PI film and (2) the PI and PDMS film. For contact (1) I am using a contact node with the default contact penalty factor and an intial contact pressure equal to the applied pressure (50 kPa). for contact (2) I am applying a continuity condition across those boundaries as the material (PI and PDMS) is bonded together and their boundaries match. I also have fixed the displacement in the x direction for the probe as it only moves in the y direction.

Attached is a screen shot of the problem and the model.

Would appreciate any suggestions.

Thanks in advance.

Darren