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Very strange displacement values for eigenfrequency calculation of piezoelectric beam
Posted Oct 16, 2012, 4:27 p.m. EDT Structural Mechanics 1 Reply
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I am modelling a piezoelectric cantilever beam using the piezoelectric devices module in 4.2a. For certain beams, which have several piezoelectric elements on one beam, I get a very high value for the 5th eigenmode. My beam is 60 microns long, and 1 micron in diameter. The displacements are small for the first 4 modes, about 10^-2. But the displacement for the 5th mode is 10^2. I am not sure how to account for this. I know that one expects physically, higher displacement at the 5th eigenmode, but this value seems nonphysical. Im not sure it's a problem of the solver scaling because the other values make sense. Any help you can provide would be greatly appreciated
1 Reply Last Post Oct 16, 2012, 4:40 p.m. EDT
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Posted:
1 decade ago
Hi
You should read through the theory of Eigenfrequency analysis. This is an energy method and the amplitudes are normalised but arbitrary, only the shape has its true importance, and relative to each other.
With COMSOL you can normalise in different ways, also w.r.t. the participation mass of the modes, then their participating mass is related
Try a search on the Forum, you are not the first asking this question
--
Good luck
Ivar
You should read through the theory of Eigenfrequency analysis. This is an energy method and the amplitudes are normalised but arbitrary, only the shape has its true importance, and relative to each other.
With COMSOL you can normalise in different ways, also w.r.t. the participation mass of the modes, then their participating mass is related
Try a search on the Forum, you are not the first asking this question
--
Good luck
Ivar