Ansys Modal analysis on simple cantilever beam
Ansys Modal analysis on simple cantilever beam
(OP)
Hi Everyone,
I am going through a modal analysis in Ansys Mechanical and have started out with a problem that has a simple analytical solution (Free-Fixed Cantilever beam circular cross section). I did a modal analysis but putting applying a fine sweep mesh through the part and fixed support on the face of one side of the beam. My results are as follows Modes (256.36, 256.38, 1554.9, 1554.9, 2822.2, 4153.2, 4153.5, 4599.1, 7664.1, 7664.5) while analytical predicts Modes (257, 1606, 4502, 8831, 14596).
I am obviously encouraged by the first mode but I have two questions. Should I be expecting better accuracy one higher modes? Why some of the modes almost identical?
Thanks Guys,
I'm new to FEA and our expert just left the company.
I am going through a modal analysis in Ansys Mechanical and have started out with a problem that has a simple analytical solution (Free-Fixed Cantilever beam circular cross section). I did a modal analysis but putting applying a fine sweep mesh through the part and fixed support on the face of one side of the beam. My results are as follows Modes (256.36, 256.38, 1554.9, 1554.9, 2822.2, 4153.2, 4153.5, 4599.1, 7664.1, 7664.5) while analytical predicts Modes (257, 1606, 4502, 8831, 14596).
I am obviously encouraged by the first mode but I have two questions. Should I be expecting better accuracy one higher modes? Why some of the modes almost identical?
Thanks Guys,
I'm new to FEA and our expert just left the company.





RE: Ansys Modal analysis on simple cantilever beam
RE: Ansys Modal analysis on simple cantilever beam
RE: Ansys Modal analysis on simple cantilever beam
You can calculate twisting and stretching modes by hand as well. Stretching is easiest: omega = sqrt(k/m) where k is the stiffness of the beam (k*delta/L).
Also, you'll probably get closer to the theoretical values if you loosen up your constraints where the beam is tied down. Perhaps if you constrain the beam in the axial direction at the fixity. Of course, you'll have to tie it down in the other two directions as well; you may want to split the fixed face into four quadrants and fix the horizontal split in the vertical direction and the vertical direction at the horizontal split. That will allow for Poisson expansion/contraction.
RE: Ansys Modal analysis on simple cantilever beam
RE: Ansys Modal analysis on simple cantilever beam
Cheers
RE: Ansys Modal analysis on simple cantilever beam