definitions

[ka3ki]

Hi everybody there,
I'm really having a problem with the definition of:

eigenfrequency(ies)
eigenvector
vibrational mode
mode shape
modal energy

what the difference between the eigenfrequency and the resonant frequency? and in which case we refer to each one?

thanks in advanced

 

[MikeyP]

"Eigenfrequency" is equivalent to undamped "natural frequency" (note that "resonant frequency" is an ambiguous term which could refer to undamped or damped natural frequency or maximum of resonance peak).

"Eigenvector" is equivalent to "undamped normal mode shape" (with a similar caveat to that above)

Applied mathematicians tend to use Eigenfrequency/vector where engineers tend to use natural frequency and mode shape. They are called Eigenfrequencies/values/vectors because they are solutions to an Eigenvalue problem (look in a graduate maths text)

Modal energy is the energy stored in a mode!

Seems like you need to do some reading. "Modal testing: Theory and Practice" by DJ Ewins has a nice gentle introduction to this sort of thing.

M

--
Dr Michael F Platten

 

[ka3ki]

Thank you for the great help