The purpose of frequency analysis is to identify the natural frequencies of the system you are analyzing. For example, the fist natural frequency of a simple mass-spring system is (k/m)^.5. In FEA these are obtained by solving for the eigenvalues and eigenvectors of the system. In real world terms, these eigenvalues/vectors correspond to the frequencies/directions for which the system is most susceptible to external perturbation. This in turn helps you figure out if you need to make design changes to make the system stronger/stiffer in certain areas.
Very appreciate your comment.
Would you like to give me some images of "natural frequency" ?
>This in turn helps you figure out if you need to make design changes to make the system stronger/stiffer in certain areas.
Some images will be helpful for me to easy understand, please....
Thank You Mahir
I don't have any pics handy, but I'm sure there is a wealth of information if you checkk Google or Wikipedia.
When frequency of force acting on your detail is close to his natural frequency hi will suffer vibrations and large displacements.
On the case : breaking a wine glass using resonance, the glass break because we put a resonance that reach the natural frequency of the glass ( correct me if I am wrong ).
In those case, the glass break after we "MANUALLY" put a resonance. The glass is ok if we not "MANUALLY" put resonance.
In the real life, what is the example of resonance ?
Thanks for all your help
Another question :
Base on Mahir comment : "This in turn helps you figure out if you need to make design changes to make the system stronger/stiffer in certain areas."
Have you example of this case ?
Even a simple example is ok.
Thanks for Steve & Mahir
If you create weldment structure to support ie. engine you must check if frequency of your support is much higer than frequency of force coming from engine.
If you design cover to shield vibrating device, shield need to have different natural frequency than frequency of vibrations.
I attached example of matched natural frequency of main rotor of heli to support of that rotor. Large vibrations and large displacements and ... crash
If you see on animation that your model vibrate in some shape than you can add some ribs to prevent this deformation. You know place for ribs by studying animation of model shape in resonans.
> frequency of your support is much higer than frequency of force coming from engine.
What is the common method so we can know the force coming from the engine ?
I will take a look your files.
Thank You Sir !!!
First that you know is frequency of load from engine rpm. (Hz=rpm*60)
Second is that any engine is unbalanced so it makes force during rotating.
Normaly force should be small so only frequency is important.
If there is large unbalance you can mesure force by using SolidWorksMotion Simulation.
go through the attached file, and calculate the list of resonant frequency which is like this
Mode No. Frequency(Rad/sec) Frequency(Hertz) Period(Seconds)
1 21203 3374.6 0.00029633
2 21343 3396.8 0.00029439
3 22798 3628.4 0.0002756
4 26778 4261.8 0.00023464
5 28895 4598.8 0.00021745
Suppose the same assembly if shaft is made to run at 1000 RPM is the structure safe and stable.In case if i am not able to predict this in frequency analysis, should i go for dynamic analysis in which (modal time history, harmonic, random vibration) which one to select and what are the inputs required to start any of these dynamic analysis. Please go through the attached file
frequency.zip 468.9 KB
Hi Steve, Mahir and Dustin....
Thanks for all your helps, I got it