frequency extraction after forming process

[marko11]

Hey guys and girls,

i've some problem that i'm working on:

I've an explicit forming simulation and i want to use a butterworth filter to have a good force-displacement-curve.
To find out the best cut-off frequency of my butterworth-filter i found this in the abaqus manual:

"If you perform a natural frequency extraction analysis on the final model configuration, you will find that the fundamental frequency at the end of the forming step is approximately 1000 Hz. Hence, a cutoff frequency that is slightly larger than this value is a good choice for this model."

Well i did frequency extractions before so i tried to do one on a deformed part. But i was not sure about the results. That's why i tried the example with the forming channel. And i didn't get the frequency of 1000Hz but 686Hz instead.

I tried it the following way:
1. I ran the forming analyses
2. I copied the model and deleted everything despite the deformed part
3. I made up a frequency step
4. I imported the results of the forming analyses by a predefined field in initial state
5. I ran the analyses

But unfortunately i didn't get the result, that the authors of the abaqus manual got

Has anybody an idea what's wrong with my proceeding?

Thanks in advance

Marko