Analysis Help: Free Modal Analysing with Ansys 13

[alireza1359]

I am a new user in this forum. In free- free modal analysing, there is 6 rigid body motion (3 displacements and 3 rotations) with frequencie's of 0, but in my analysis there is 3 rigid body motions with frequencie's of 0 (linear displaements) and the frequencie's of others (rotational rigid body motons) are not zero. I do not know this reason. Please help me. I am analysing the model using Ansys 13.

 

[joslopher]

Hi,
If I wanted to get the natural frequencies of a box-like structure with four wheels (at each corner of the bottom surface) by means of FE-analysis, should it be performed as constrained or unconstrained ? Indeed, the wheels are not bounded to the ground, so please, could you help me?
Thank you very much