zero values for moments in patran

[mirb3000]

Hi,
I have this proble, y rum the analysis for axial loads and all in Ok
but when I tried with moments, the resuls are 0.

I am using patran/nastran 2012

I attached the BDF

All the ideas are welcome

Thanks

 

[nlgyro]

You're directly applying moments to grid points associated to CTETRA (solid) elements without the use of rigids (RBE2/RBE3) elements.

Its natural that nastran generates zero internal moments for these load-cases that explicitly have moments applied.

 

[aerostress82]

solid elements don't carry rotational load. meaning they will never transfer 456 degrees of freedoms.
that's why when you apply axial to those solid element nodes, you can "stress" your FEA model. however when you apply moments directly at the nodes, your solid element is helpless to support it, that's why you can't transfer those applied loads.

only way is as nlgyro mentioned. by attaching RBE2/RBE3 elements and applying this moment to an free node of this RBE, you can have moment arms (RBE arms) - and this will "induce" translational loads from your moment loads applied to the "central" nodes of your RBEs.

Spaceship!!
Aerospace Engineer, M.Sc. / Aircraft Stress Engineer