Contact elements on quadratic faces missing midside nodes

If you export contact elements to jobname.cel using


they only seem to be C3D8 or C3D6 even on faces of C3D20/10. I wonder if the midside nodes really are connected but just not shown in the .cel file?

it seems due to midside node problems in opposite sign. Abaqus also remove by setting to be zero at midside nodes internally. However, CalculiX still using small amount of values

for contact analysis, many recommended using linear element (incompatible or enhanced) to eliminated midside node problems in sign or still using quadratic type with mesh refinement to match curved geometry.

Thanks @xyont I see the manual says node-to-face contact uses tiny weights on quadratic quad face corner nodes but don’t see anything about face-to-face contact treating midside nodes specially. I’m only interested in face-to-face contact.

I’ll do a test forcing a midside node out of place and see how it behaves.

Yea midside nodes seem properly connected and transfer prescribed displacement across the contact just as well as corner nodes. I guess the .cel file just omits those nodes for clarity or something.

so, it’s surface to surface contact type. In this cases large integration point are generates at contact surfaces not only midside nodes connected but all extra point in the surfaces.

probably right for surface to surface contact type, an output of midside nodes should be available.