Natural Frequency, Resonance, and FRFs

[@ED-ix6mq]

Very good explanation, thank you!

[@IRANIGUY]

in FRF plots @4:00 : the vertical axes do not appear to be correct. The Imag axis should be Flipped in the lower phase diagram.

[@_LusitaSimbolon]

thank you, very good video!

[@Lethgar_Smith]

Altering the resonate frequency of an object is the key to an entirely new era of human technology.

[@jihopark1020]

Thank you so much

[@jjxie3291]

Hello, among the three elements of frequency, damping and vibration mode obtained in modal analysis, does damping refer to "damping factor" or "damping ratio"? Is it the latter? Thank you and look forward to your reply

[@SimcenterTesting]

Damping factor and damping ratio are just different ways of describing the same thing. See this article for more info and how the different forms are related (in Section 2). community.sw.siemens.com/s/article/how-to-calculate-damping-from-a-frf

[@jjxie3291]

@@SimcenterTesting Thank you. I will continue to study the linked articles

[@SoulfullSpace]

I want to find the damping ratio of a helical spring using this method: 1. Attach an accelerometer at the top of the spring. 2. Disturb the spring by hand to generate a time vs. frequency graph. 3. Convert this time vs. frequency graph to an FFT to see the frequency vs. amplitude graph. 4. Find the damping ratio using the half-bandwidth method on the FFT. My questions are: a. Is this the right method to find the damping ratio, or is the FRF necessary to include the force with hammer impact? b. What if I use or don't use an impact hammer as in this video?

[@Will_Rog42]

The half-power method is defined based on the FRF, so to use the half-power method you would need to measure the input to the spring. Alternatively, you could use the logarithmic decrement method. This does not require you to measure the force and does not require an FFT.

[@SoulfullSpace]

@@Will_Rog42 DO you think we can measure damping ratio using Log decriment without FFT and input force?

[@giovannigiorgio0]

At 5:04 isn't the left spring system supposed to dampen over time?

[@SimcenterTesting]

This is a theoretical example where the left mass-spring system does not have any damping (c). As a result, it does not dampen over time.

[@toddr5732]

Where is the powerpoint plug in they mentioned ? Any link to download it ?

[@SimcenterTesting]

community.sw.siemens.com/s/article/active-pictures-plug-ins-for-simcenter-available

[@dawonpark3268]

well helped