Define System Stiffness From Vibration Data
Define System Stiffness From Vibration Data
(OP)
Hello,
I do not know that much about modal analysis results, but I was hoping that someone could help me out.
I have some data showing a components deflection under engine operating rpm. What I would like to do is to have a simple calculation which can give me an idea of the components stiffness in that area based on this data. Does anyone know how to do this?
Thank you in advance!
John
I do not know that much about modal analysis results, but I was hoping that someone could help me out.
I have some data showing a components deflection under engine operating rpm. What I would like to do is to have a simple calculation which can give me an idea of the components stiffness in that area based on this data. Does anyone know how to do this?
Thank you in advance!
John





RE: Define System Stiffness From Vibration Data
Cheers
Greg Locock
RE: Define System Stiffness From Vibration Data
I am having some doubts. If we have the deflections for the particular force then we can obtain stiffness. Which is that stiffness. in many FEM analysis we use to calculate the stiffness by this method only.
Please guide me !
regards
jo'
RE: Define System Stiffness From Vibration Data
If you have the results from an experimental modal analysis (or an FEA) then the FRF at point B for the point impedance is Hbb which can be found from the point impedance of the excitation point A and the transfer function between them.
As best I can remember Hbb=Hab*Hab/Haa
using complex maths throughout
This slightly surprising result is due to reciprocity (Hab=Hba). In practice it is rather dangerous, as the errors get out of hand very quickly.
Cheers
Greg Locock
RE: Define System Stiffness From Vibration Data