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What is frequency response analysis - FEA for All
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- čas přidán 15. 08. 2024
- Frequency response analysis is an extension of modal analysis in some way. If you want to know about modal analysis, the full article is here:
feaforall.com/w...
In short, modal analysis helps to determine the modes of vibrations and the frequencies at which those modes are triggered, BUT modal analysis doesn’t give you any info about the real deformation that an excitation of one of those modes will actually cause. When you have to do a dynamic analysis, modal analysis is only the beginning!
Some modes will cause more « resonance » than others (and thus more damage)… so we want to know which ones and we want also to calculate the maximum deformation for each of the modes « triggered ».
Go on the blog to read the full explanation:
feaforall.com/f...
Usually I avoid videos which start with "This is My Horn", but this video was very useful, even though I'm more confused than before I watched it.
Still getting my head around modal analysis, (for CubSats during launch), knowing which modes are critical, how to know which of an infinite number of modes impart more structural loading and displacements on the CubSat. How to look at individual components and sub-assemblies with in the entire system etc. Looking into mode participation factors now to try to understand what's important and what's rubbish.
Hey Cyprien. This is by far the best tutorial I have found on the topic. Very well explained. Please keep making more such videos.
Thank you Rahul! Glad it is useful to you.
Really good explanation in this media. I have seen many videos. But yours explanation is the best.
I really appreciate your work, THANKS for sharing your knowledge for FREE
It is such a hard thing to find now a days
Thank you so much for taking the time to make this video! I knew nothing about FRF before this but i have somewhat of a vague idea now. Very much appreciated!
Extremely helpful for beginners in modal analysis irrespective of the software they use!
It is a very helpful video to understand the harmonic response. You cover all the things of harmonic analysis.
Amazing video. Thank you very much!
Excelent tutorial, thanks!
Really helpful. Please do video on how to get PSD values for random vibration and how to design components for random vibration
Awesome. Great work, this is timeless.
great video on frf analysis
Very well explanation !! Thanks a lot
Very good explanation. Why should we consider less no of mode shapes(say 10 or 20) why can't we go or 50 or more
You can, but it is generally useless because you want to detect the main modes of vibration which have a strong response to a certain type of loading. There are generally only a few of those really “strongly problematic” modes. Others are minor vibration modes which aren’t so impactful.
@@Feaforall I absolutely accept ur answer. What factors should define the main modes of vibration or strongly problematic modes.
Thank you very much. This is most helpful!
Great work cyprien.!!
Looking forward to more updates from you.
If I understand this correctly for frequency response, after you have done the modal analysis, you have to run a static analysis. Then you define a modal frequency response associating the load to frequency and then giving a range of frequencies for the response. The question I had is the pressure load that you applied does it matter how much is the pressure load .? or you just have to define a reasonable pressure load .? The load you applied seems low so my question is if I am working on a different component will such a low pressure load still work or do i have to be very accurate defining the load.?
Hi cyprian..
As per my understanding we don't apply any load in modal analysis. We just apply boundary condition..but you are applying pressure of 0.1 mpa..Can you convince in which case we can do this.?
This is not modal, this is frequency response. Yes, modal has no load.
@@Feaforall ii think first analysis you did was modal
@@yogeshbavge8263 i guess software connivanced the load automatically
thanks!! for such a video, really needed and could please make video on "what after FR-Analysis, like time response, time points etc..."
Thanks for the video - good introduction on FRF to me - however I have a question - dont we want to design the structure to have min NF higher than max operating frequency? When you set the Freq range (1000-10000hz) is this based on the operating frequency of the ultrasonic weld machine?
Instablaster...
Good nice very helpful video
will you excite the modes the same way if you have a force in a different location? Let's say on the side of the block, instead the bottom
No you won't excite in the same way. That's why in frequency/time response, the load direction is important.
Nice explanation Rasu. I would like to know the conclusion from this analysis. what are important factors while considering response location & criteria for reducing response. waiting for your answer. Thanks Pradeep
Thanks! My name is Rusu BTW ;-) But you can call me Cyprien. I guess that there are many criteria to reduce the response, incuding redesigning your part... that's very experimental I think
Thanks for the reply Cyprien. could you please give me links on such vedios or materials. It would help me in understanding NVH like FRF, Transient, Random, PSD., etc Thanks once again for your quick response that I had not expected.
Merci beaucoup
C'est exactement ce que je cherchais.
Êtes vous toujours en Chine?
Thank u so much for this such a great video..it's helpful of many Engineering students......sir..... actually I'm doing a electric go kart..so I have problem with simulation..can I have u r contact details sir .??
Thanks for the great video. At the end you mention that there are 3 frequencies that are dangerous and should be avoided, but this is an ultrassonic horn, shouldn't it be designed for those specific ressonating frequencies?
Good point!
Thank you for your video, it helps me to much.
Thank you so much. This helped me a lot bro.
Hi thanks for the wonderful video! I have a question as you mentioned that Freq. Res. Analysis Direct and Freq. Res. Analysis Modal are different in that damping is not considered in the latter. If possible could you please elaborate it little more? Also I could not understand the benefit of performing Freq. Res. Analysis Modal except that it facilitated to know the natural freq. modes which otherwise we can also know from the freq. displacement graph! so what is the purpose of adding modal to the setup ?
Frequency response on modal base is much faster in terms of calculation time it takes. That’s because once the base is calculated, all the frequency responses can be calculated from it with just a simple linear equation. Direct frequency response requires to solve the matrices for every frequency so if you have a large frequency bracket to evaluate, it can take a lot of time!
@@Feaforall thanks a lot for your quick response ! I got the point👍
Great Video
Why is the modal analysis done with constraints and loads?
Constraints only, no loads for modal analysis. Frequency response can be done with constraints and loads
Amazing.. And subscribed your channel.. It's awesome
Greetings Cyprien
I am new in the channel and thanks to you I have discovered Salome and Code Aster.
The university that I attend is still closed by the pandemic and open source and free software will be handy next semester so I would like to ask you if this type of analysis is doable in Code Aster
Yes, it is possible. I haven’t done any videos about frequency response with code aster, but it’s possible. I think the command is DYNA_VIBRA
www.code-aster.org/UPLOAD/DOC/Formations/02-transient-harmonic.pdf
Check Harmonic Analysis
@@Feaforall Greetings
Thank you so much for your answer. I will check the link you left below.
It's an excellent news!!
Good job
Hey Cyprien, very good video, a lot of useful information there. Do you happen to have some video or article where you explain more about stress safety factors? I'd like to hear about that
Not yet ;-) But that's a very good idea! Join the email list on feaforall and I'll send you the article when it is ready
feaforall.com/calculate-safety-factor/
@Cyprien Rusu
Hi can you please tell me which software it is????
Midas NFX… not sure you can still purchase this software.
Excellent video
Thanks
i have a doubt ,you are done modal analysis first ,then you are done FRF analysis and that too you verify the excitation(in FRF) what we get in modal analysis ,cyprien, geting exitations in modal and FRF is same(nearly)....so why we do FRF ,is it not enough to do modal analysis.
thanks!
What is the I fundamental frequency in the problem.
Every time signal can be decomposed into an infinite sum of certain frequencies multiplied by a coefficient. The fundamental frequency is the one that has the largest coefficient. In other terms, it is the frequency at which your system will resonate the most.
Great job
If the frequency response analysis at 0 Hz demonstrates the same as static deflections?
1 Hz yes (0 Hz is impossible because T=1/f would be infinite)
Good video...