I have been easing my way into ANSYS and doing some modal analyses. The component I am modeling is a body of revolution with N=15 slots in it. The cross section looks much like the one in post #1 of this thread.(adsbygoogle = window.adsbygoogle || []).push({});

I started out by modeling the full 360° ring and requested the first 6 Modes shapes. The results were fairly easy to interpret: Here are the first 6 mode shapes and their corresponding frequencies.

Then, I decided to try to make use of symmetry: since a 360°/15 sector repeats 15 times, I used a "cyclic symmetry" model with this sector. So I again requested the first 6 mode shapes. The results are a little confusing to me now. They are instead reported in terms of mode shapes, harmonic indices, and corresponding frequencies (see screenshot below). There are 66 such entries and I am a little befuddled as to how I can relate them to the results I got from the full 360° model (which I have since deleted).

I am reading through Chapter 6 of the ANSYS Mechanical APDL Advanced Analysis Guide (page 157 of this pdf) but it is not quite clicking.

It says that for a nodal diameterd, and model with N sectors (in this case 15), and harmonic indexk, we have:

d = m*N ± k

I understand (I think) that "nodal diameters" are essentially the same as mode shapes. The first mode shape has 1 node and 0 nodal diameters (at least for a circular membrane fixed at its perimeter).

But looking at my results, I am still not sure of how to get from "here to there." "Here" being a solution in terms of mode shapes, k's, and frequencies. And "there" being a solution in terms of Mode shapes and frequencies like for the 360 ring.

Any guidance is much appreciated.

Thanks,

KC

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Modal Analysis: Interpreting ANSYS Results

Have something to add?

Draft saved
Draft deleted

**Physics Forums | Science Articles, Homework Help, Discussion**