Download Poster

TRANSFER FUNCTION TESTS ON SELF HEALING BIOMIMETIC
STRUCTURES
D. Daugaard, E. Petersen and U.Korde
South Dakota School of Mines and Technology, Rapid City, SD 57701
Introduction
A lightweight film known as Kapton with 12 piezoelectric transducers attached was subjected to a frequency range of 1 kHz to 15 MHz of current at 10 volts. The resulting sinusoidal waves produced and sensed by an actuator-sensor pair will be compared to the waves
produced and sensed by a different actuator-sensor pair or more than one actuator-sensor pair. A transducer can act as an actuator or a sensor. An actuator makes waves and a sensor senses them. Eventually an identical film with a cut in it will be used. The purpose of
this research is to see if a pattern can be recognized and used in order to locate, acknowledge or repair a crack in the membrane. The tests that will be run will be in the d31 mode. Periodic excitation in this mode will produce longitudinal (along the length) waves.
Procedure
Kapton is a polyimide film that is being tested. Eventually a membrane
impregnated with heat sensitive epoxy like material will be used. Below
is an example of a 3 part membrane that could be used. An epoxy
makes up the larger portion. Packets or bubbles of glue are used as
the healing material. A catalyst known as Grubbs’ catalyst is used to
help polymerize the healing material.
Layout of Piezo Transducers on the
Kapton Membrane
This graph shows the results of transducers
1 & 2 with a variety of changes in the tension
of the Kapton on the sides and edges.
Tension Comparison for Transducers 1 & 2
0.0005
0.0004
Comparison of 1 & 7
0.0002
0.0001
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
Log(Hertz)
Normal Tension
Inner Tension
Outer Tension
Both outer
This graph compares one pair of transducers
with another transducer in the center with
power to another pair under the same
conditions.
Comparison of 1 & 4 with 1 & 7 with a center sensor with power
0.0004
0.0003
0.0002
Initial Results (Control)
0
3
3.5
4
4.5
5
5.5
6
6.5
7
Vout/Vin
0
0.0001
{Voltage out /voltage in =(10^-(dbVin-dbVout)/20)}
This graph compares the results of
a 1-7 actuation-sensor pair by
itself, with an extra transducer
placed in the center without power
and with the extra transducer with
power.
0.0003
V out/V in
A transducer is a device that can be used as an actuator or a sensor contingent upon the circuit and
connections made. A transducer is made up of a piece of piezo film pinched between 2 electrodes. The piezo
film is a material that will respond to electrical forces and convert it to a mechanical force or convert a
mechanical force to an electrical force.
1.Connect the waveform generator and
oscilloscope to 2 of the transducers.
2.Set the oscilloscope to 10 volts and
test for frequencies of 1 kHz to 15 MHz
based on a sinusoidal waveform.
3.Measure and record the decibel voltages
going in the first transducer and out the
second transducer.
4.Test all the possible combinations of 2
transducers.
5.Record the data on a chart and plot the
voltage out divided by the voltage in,
against the Log of the frequency.
6.Voltage out divided by voltage in was
calculated by taking 10 to the power of
the negative of dB voltage in minus dB
voltage out divided by 20.
7.Repeat tests for other variables.
8.The results below are for transducers 1 & 2.
9.These results were typical other the pairs tested.
V out/V in
Materials
Tested Variable Results
3.50E-04
3.00E-04
2.50E-04
2.00E-04
1.50E-04
1.00E-04
5.00E-05
0.00E+00
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
Log(Hertz)
1 & 7 with center
1 & 7 with center with power
1 & 7 alone
This graph compares the results of 4
powered actuators and 4 sensors by
themselves, with an extra transducer
placed in the center without power
and with the extra transducer with
power.
7.5
Comparison of 2,3,4,5 with 8,9,10,11
Log(Hertz)
Sensors 1 & 7 with one in the center with power
0.0002
Data for Transducers 1 & 2
Research Objective & Set Up
1. Prepare a 100mm by 200mm piece of Kapton by attaching 4
transducers on each of the 200mm sides and 2 to each of the 100mm
sides.
2. Mount the membrane on a rectangular frame.
3. Set up the experiment with a voltage waveform generator and
oscilloscope.
4. Test single-input--multiple-output transfer functions.
5. Test multiple-input—multiple-output functions.
6. Plot all transfer functions.
7. Continue tests on the specimen with a transducer in the center
as an obstruction.
8. Continue tests on the specimen with a crack.
9. Plot all transfers and compare with the original specimen.
Kapton Membrane & Transducers
dBVin
dBVout
Vout/Vin
Hertz
Log(Hertz)
36.98333
-49.3767
4.81E-05
1000
3
36.77333
-51.25
3.97E-05
3000
3.477121
37.19
-52.5
3.28E-05
5000
3.69897
36.25
-52.8133
3.52E-05
7000
3.845098
36.04333
-53.23
3.44E-05
9000
3.954243
35.10667
-52.9167
3.97E-05
10000
4
34.37667
-52.8133
4.37E-05
30000
4.477121
36.25
-52.19
3.78E-05
50000
4.69897
35.83667
-51.3533
4.37E-05
70000
4.845098
35.94
-51.7733
4.11E-05
90000
4.954243
35.41667
-50.8333
4.87E-05
100000
5
35.94
-50.62
4.70E-05
300000
5.477121
36.66667
-50.8333
4.22E-05
500000
5.69897
35.31
-51.5633
4.53E-05
700000
5.845098
35
-51.9767
4.48E-05
900000
5.954243
37.08667
-50.1033
4.37E-05
1000000
6
33.74667
-52.1867
5.05E-05
3000000
6.477121
32.70667
-52.2933
5.62E-05
5000000
6.69897
28.13
-56.1467
6.11E-05
7000000
6.845098
23.44
-58.7533
7.77E-05
9000000
6.954243
23.23333
-53.1233
0.000152
10000000
7
36.14667
-55.1033
2.74E-05
15000000
7.176091
Equipment
A test was done to see if the wave motion
was vertical or horizontal. Silver dust
particles sprinkled on top to see if nodes
and antinodes would form produced
negative results as did chalk dust. This
supported the fact that the excitation of the
waves were longitudinal.
**An oscilloscope is an instrument that
displays and/or records the changes of
voltage in an electric circuit.
Waveform Generator*
Oscilloscope**
0.00015
0.0001
0.00005
0
3
3.5
4
with center no power
V out/V in : Experimental
Acknowledgements
0.00008
0.00006
0.00004
0.00002
0
5
5.5
Log(Hertz)
6
6.5
7
7.5
with center with power
no center
Future tests will include time reversal signal processing, cracked membrane testing with
different combinations of the 12 transducers and verification of results with analytical
modeling.
0.0001
4.5
6
Future Work
0.00012
4
5.5
Log(Hertz)
0.00014
3.5
5
The tests performed with the individual pairs and with different variables produced similar
results of a higher ratio of voltage out to voltage in at a frequency in the range of 3 MHz to
10 MHz. The different transfer functions performed provides insight towards algorithms that
will be useful in the repair process. Qualitatively the results are similar. The small particles
on top of the membrane did not respond, supporting the fact that the energy movement is
longitudinal.
Voltage Between Sensors 1 & 2
3
4.5
Conclusions
0.00016
*A waveform generator is an instrument that
converts a wave function, a pattern of electricity,
to a waveform with crests, troughs and
amplitudes.
Vout/Vin
Sensors 1 & 4 with one in the center with power
6.5
7
7.5
Thanks to Dr. Umesh Korde of the School of Mines, Eric
Petersen of the University of Nebraska at Lincoln, Brant Miller of
the School of Mines, Dr. Rob Winter of the School of Mines, the
National Science Foundation RET program and the Air Force
Research Laboratory, Kirkland, AFB, New Mexico.