How do I add damping to a certain frequency to my system in FEM

Innovator
Innovator

Hi all

 

using SEMFREQ as solver , and having PBAR, CBAR and CNOM1 point masses, how do I add damping to certain frequencies ?

4 REPLIES 4

Re: How do I add damping to a certain frequency to my system in FEM

Gears Phenom Gears Phenom
Gears Phenom

Use function reference for material damping and modal damping table for overall structural damping.

Beware: AFAIK solver don’t multiply value of damping coefficient and values from damping table. Therefore, you have to write some damp. coefficient too. However, this I`m not 100% sure and will be good if you compare results of damp.function with damp.coef.

Re: How do I add damping to a certain frequency to my system in FEM

Innovator
Innovator

Thank you

 

I am running these on a .bdf file and I have both general damping and material damping, but they are not frequency specific, meaning , damping for one specific frequency. Did you intend that I could do this in Function ?

 

which of the 35 types should I choose ?

 

also , why when I create the critical damping, and export the analysis system to bdf, I don't see the function definition ?

Re: How do I add damping to a certain frequency to my system in FEM

Gears Phenom Gears Phenom
Gears Phenom

First of all, I make check and get that material function dependencies (as at first picture in my previous post) are for temperature only, not for frequency dependencies.

For overall structural damping you can use function type 6..Structural Damping vs. Freq.

Here is an example file.

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Re: How do I add damping to a certain frequency to my system in FEM

Gears Phenom Gears Phenom
Gears Phenom

also , why when I create the critical damping, and export the analysis system to bdf, I don't see the function definition ?


Can you clera this statement with a couple of screenshots? Do you use function Crit. Damp. vs. Frequency?