Modal Frequency Response

[Torus86]

Hi,
I'm using Nastran and Femap as post-processor to do a modal frequency response of a plate.
I would ask if someone could help me and suggest if I'm writing the right commands for excitation force.

The plate is 3m x 1.7m thick 0.01m and the excitation force is sinusoidal and has an amplitude of 1000N at a frequency of 50Hz at the point xf=0.6m yf=0.4m from the left corner of the plate.

Now I 'm not able to write the excitation frequency.

I attach the file here please HELP ME..
Thank you very much....

 

[drmuh]

Hi,
Initially, in your EIGRL command, you entered up to 20 modes as I see, it may not cover 50 Hz (on the laptop I am writing I do not have a pre-processor or my nastran books). Later I can update the post.
FREQ command looks a little fishy, I will check that one also. I am not clear why you have individual frequencies but not 50 Hz. EIGRL solves for modal and FREQ applies the defined force at the frequency range where you are interested, which is 50 in our case.
Please run a basic modal analysis and see if first 20 modes exceed 50 Hz, I would go upto 100 Hz for including the contribution of residuals.
Later on I will send you a file with the logic chart. I generally follow this chart especially for FRF optimization where there are a lot commands.
Take care,
Mert

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