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.

 

[alphy]

modal frequency analysis is a useful tool for understanding the dynamic behavior of a system. It involves determining the natural frequencies and mode shapes of a system, which can provide valuable information about its structural integrity and potential for resonance.

In order to determine the modal frequency of a system with multiple components, there are several steps you can follow:

1. Identify the individual components of the system: In your case, these would be the compressor, condenser, piping, fan, fan bracket, and frame.

2. Determine the natural frequency of each component: This can be done through experimental testing or using simulation software. Make sure to consider the material properties and geometry of each component in your calculations.

3. Assemble the components into the overall system: This can be done in a simulation software or physically if possible.

4. Conduct a modal analysis on the assembled system: This will result in the natural frequencies and mode shapes of the overall system.

5. Compare the modal frequencies of the individual components with the overall system: This will help you understand how each component contributes to the overall system's modal response.

6. Identify any potential resonance issues: If any of the individual components have a natural frequency close to the overall system's natural frequency, it could lead to resonance and potential structural issues. In this case, adjustments to the design or materials may be necessary.

It is also important to note that the accuracy of the modal frequency analysis will depend on the accuracy of the input data and assumptions made in the simulation or testing process. Therefore, it is recommended to validate the results through experimental testing if possible.

I hope this helps you in your analysis. If you have any further questions or need more specific guidance, I would suggest consulting with a structural engineer or conducting further research on modal frequency analysis. Best of luck in your analysis!