RBE2 to Solid Hex Element Rotational transfer (Patran/Nastran)

[hootrpootr]

Hello,

Any help is appreciated with this analysis of mine. I’m trying to model a lap shear joint test, where two plates are bonded together with an adhesive and sheared apart with an in plane load.

I’ve modeled the plates as solid elements (Hex8). The bond has been modeled following the method from this site (

https://femci.gsfc.nasa.gov/adhesive/index.html),

where zero length springs (CELAS1) are created at the bond midplane, and RBE2 elements connect those springs to the plates.

I’m getting the “excessive pivot ratios” failure and I can’t figure out why. I suspect it’s because of the connection between the solid and RBE2 elements because solid elements don’t transfer rotation. I replaced the solids with shell elements (CQUAD4) as a test, and my model ran just fine.

Sorry for such a long post, but any thoughts/solutions?

Thanks!

 

[karachun]

Yep, SOLID elements have only translational DOF1s. You can coat them with thin layer of shell elements or include rotational degrees of freedom. You can avoid pivot error if RBE2 nodes don’t form line, this line is possible axis of rotation.
P.S. It’s okay to post detailed description, it’s much better than "I have problem, plz help me!!!".