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Hi

that is a nice one :)
I doubt it's physical, except if you have a very special beam (may be ?), certainly not a simple 2nd order resonator can explain that one.

I would suggest you try:
1) to show the data points to better identify the true discretization used
2) you check the calculated values in a table to be sure there is no aliasing effects on the plot
3) perhaps also plot the phase to have the full Bode plot

And if you do not find anything, I would suggest to submit the case to support, with the model for their analysis

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Good luck
Ivar

Hey Ivar! Thanks for replying so quick.
I am working on Piezoelectric Cantilever beam. The graph is accurate at step size 2KHz.. It's showing maximum displacement at Resonance but when I take step size 0.1KHz it gives me minimum displacement at resonance. Why?

Hi,

This is because you are plotting the real part of the result, and at resonance there is a 90 degree phase shift.

Below you will find a quote from the documentation.

Regards,
Henrik

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Most results of a frequency domain analysis are complex. In results evaluation, the real value of any result quantity will be shown. Assuming that you want to display for example the displacement in the x-direction, u, you have following options:

• Plot u or real(u). This gives the displacement at zero phase angle.
• Plot imag(u). This gives the displacement at a phase angle of 90 degrees.
• Plot abs(u). This gives the amplitude of the displacement.
• Plot arg(u). This gives the phase angle of the displacement.

Result quantities that are nonlinear in terms of the displacements, such as principal stresses, should be interpreted with great care. They will in general not be harmonic, so the amplitude and phase information is not reliable.

Some extra variables for postprocessing are created in a frequency-domain analysis. As an example, in the Solid Mechanics interface the following variables are defined:

• solid.disp—Norm of displacement (at current phase angle)
• solid.vel—Norm of velocity (at current phase angle)
• solid.acc—Norm of acceleration (at current phase angle)
• solid.disp_rms—RMS displacement over a cycle
• solid.vel_rms—RMS velocity over a cycle
• solid.acc_rms—RMS acceleration over a cycle
• solid.uAmpX—Amplitude of displacement in X direction
• solid.uAmp_tX—Amplitude of velocity in X direction
• solid.uAmp_ttX—Amplitude of acceleration in X direction
• solid.uPhaseX—Phase of X displacement, in radians
• solid.uPhase_tX—Phase of X velocity, in radians
• colid.uPhase_ttX—Phase of X displacement, in radians

The components in other coordinate directions are obtained by replacing X by another coordinate name.
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Hi

I hadn't thought of a PZT cantilever, true if you plot the square of the signal you will see such a dip as you have the anti and resonances both wrapped "up". But then plotting amplitude and phase would show this easier.

But Henrik has given you already most explanations.
So your nice dip curve it's true and physical ;)

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Good luck
Ivar