Modal Frequency of a System having more than two components.

In summary, the individual is looking for an efficient procedure to find the natural frequency of a system comprising more than two components, such as a compressor, condenser, piping, fan, fan bracket, and frame. They have considered using finite element analysis software, such as ANSYS or Comsol, or a less expensive option like LISA. However, their main concern is how to correlate the natural frequency of each component with the total assembly. They have been advised to research "Component mode synthesis" or "Craig Bampton" for more information on this topic.
  • #1
subha_iit
13
0
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
 
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  • #2
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
 
  • #3
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.
 
  • #4
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.
 
  • #5
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!
 

What is the definition of modal frequency?

Modal frequency is the frequency at which a structure or system naturally vibrates. It is also known as the natural frequency or resonant frequency.

How is the modal frequency calculated for a system with more than two components?

The modal frequency for a system with more than two components is calculated by finding the eigenvalues and eigenvectors of the system's mass and stiffness matrices. These values are then used to determine the natural frequencies and corresponding modes of vibration for the system.

What factors can affect the modal frequency of a system with multiple components?

The modal frequency of a system with multiple components can be affected by various factors such as the stiffness and mass distribution of the components, the boundary conditions, and any external forces or excitations acting on the system.

Why is understanding the modal frequency important in engineering and design?

Understanding the modal frequency of a system is important in engineering and design because it helps to predict the dynamic behavior of the system. This information can be used to ensure that the system can withstand the expected loads and vibrations, and to avoid potential resonance issues.

How can the modal frequency of a system be controlled or adjusted?

The modal frequency of a system can be controlled or adjusted by changing the stiffness or mass of the components, altering the boundary conditions, or adding damping elements to the system. This can be done through design modifications or by using active control techniques.

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