PROBLEM
TYPE - Modal Analysis
Data
-> Problem data -> 2D, Axisymmetric
Make sure Geometry is
set to 2D, and that the model Class is
set to Axisymmetric. Next, change the Analysis to Harmonic,
and check both Compute Stress and Include
Losses boxes.
Finally, make sure the Mesh Units are set to
millimeters.
Do not forget to validate your changes by clicking on Accept
Data.
Frequency
Intervals
The harmonic analysis is performed for frequency
intervals that we must specify. Open the Frequency
Intervals window,
and define a linear frequency sweep between 25 and
55kHz with increments of 1kHz.
Next, create a second interval (by copying the first
one), and define a frequency interval between 32 and
34kHz with increments of 100Hz.


Click on Accept Data to validate your changes.
Repeat for a third interval between 36 and 40kHz with
increments of 200Hz.
The choice of intervals is dictated by the user's knowledge
of the system and desired objectives of the analysis.
Here, we use intervals 2 and 3 to obtain a smoother admittance
plot around the electrical resonance and antiresonance
of the transducer.
The frequency intervals are automatically
combined and sorted. The list of frequencies that will
be
used for the harmonic computation is:
25000, 26000, 27000, 28000, 29000, 30000, 31000, 32000, 32100, 32200, 32300,
32400, 32500, 32600, 32700, 32800, 32900, 33000, 33100, 33200, 33300, 33400,
33500, 33600, 33700, 33800, 33900, 34000, 35000, 36000, 36200, 36400, 36600,
36800, 37000, 37200, 37400, 37600, 37800, 38000, 38200, 38400, 38600, 38800,
39000, 39200, 39400, 39600, 39800, 40000, 41000, 42000, 43000, 44000, 45000,
46000, 47000, 48000, 49000, 50000, 51000, 52000, 53000, 54000, 55000
Note that the three lists, composed of 31, 21 and 21 frequencies,
add up to one final list of 65 frequencies instead of 73. This is because
duplicate
frequencies are automatically removed from the final frequency list.
Underwater
The problem data and mesh units have
not changed, so there is no need to modify them. However,
you may want to modify the frequency intervals 2 and
3 as follows, because the resonance
frequency will shift to lower due the water load.
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