Modal Frequency of a System having more than two components.

[subha_iit]

I am looking for an efficient procedure to find the natural frequency of a system comprising more than two components. Like I have an assembly of system comprising compressor, condenser, piping, fan, fan bracket, and frame. I have all the designs and dimensions of the total model. How can I find out the total modal response of the overall system as well as how I relate the modal response of each components with the modal response of my total assembly.

Any response is welcome. I have gone through some literature review, but nowhere I have not seen such a problem with some really good solution. Please, HELP ME TO FIND OUT THIS. A

 

[Mech_Engineer]

For complex geometry, your best bet is finite element analysis software such as ANSYS or Comsol. Each is capable of finding modal frequencies for assembled components.

http://www.ansys.com/
http://www.comsol.com/
List of commercial FEA packages: http://en.wikipedia.org/wiki/List_of_finite_element_software_packages#Proprietary.2FCommercial

For a more inexpensive option you may also look into LISA although I can't vouch for its capabilities or accuracy.

http://www.lisa-fet.com/
List of free/open source FEA packages: http://en.wikipedia.org/wiki/List_of_finite_element_software_packages#Free.2FOpen_source

 

[subha_iit]

Mech_Engineer@ Thanks for your response.

I know commercial software like ANSYS or other you specify do calculate the natural frequency of a total assembly, but What I am looking for is how can you co-relate the natural frequency of several components with the natural frequency of total assembly.

If I got individual response of several components and mass_participation factor for all the 6 d.o.fs (means X, Y,Z, Rot X, Rot Y, Rot Z) can I co-relate form that.

 

[AlephZero]

Google for "Component mode synthesis" or "Craig Bampton".

That should get you started on a literature ssearch. There's a lot to read and many different variations of the general idea.