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Corrosion Detection in Reinforced Concrete Beams
Using Piezoceramics
Shainur Ahsan, REU Student Dr. Haichang Gu, Post-Doc Mentor Dr. Gangbing Song, Faculty Mentor
Department of Civil and Environmental Engineering Department of Mechanical Engineering
University of Houston Houston, TX
Sponsored by the National Science Foundation July 2009
Introduction
As more civil infrastructure reach the end of their intended lifespan, they are becoming plagued by many problems as a result of regular wear and tear as well as being exposed to environmental elements. One of the problems, corrosion, occurs as chloride ions react with metals. As a result, part of the metal dissolves into a byproduct; the remaining metal has a smaller cross-sectional area. Corrosion costs the US economy roughly $278 billion dollars a year with approximately $8.3 billion dollars in damage to highway bridges (Virmani). As more and more infrastructure near the end of their service life, this number will only continue to increase.
Corrosion can be hard to detect until major damage has already been done. Because steel rebar is encased inside of a concrete cover, it is hard to observe damage from corrosion directly. Existing methods have used ultrasound technology to detect damage within the concrete. However, this is an inefficient method because of the high cost of equipment as well as high training cost of personnel. The equipment is usually very bulky which makes many areas inaccessible to monitoring. Recently, more emphasis has been placed on embedding sensors inside of the structure to improve monitoring. Though many sensors have been developed to monitor corrosion detection in steel reinforcement, the search for an efficient and functional sensor is ongoing. The majority of existing methods employ electrochemical methods to monitor factors such as pH, oxygen content, and chloride and carbon dioxide concentration. However, many researchers have identified interference from environmental factors as problems to these methods. A method that is immune to environmental effects would be very beneficial.
Piezoceramics have been studied for structural health monitoring (SHM) for a number of years. The relationship between electrical and mechanical impedance is used to detect stress. Because a mechanical stress is induced with an electrical current, the ceramic patches also have an application in vibration dampening. Because of their versatility, they are being used in more and more monitoring scenarios. Their use for corrosion detection in rebar has not been thoroughly examined.
Corrosion monitoring in aircraft has garnered the attention of many researchers. The declining state of KC-135 refueling tankers in the US Air Force’s fleet is one example. Most of these models have well exceeded their intended service life though they continue to be in use today. Corrosion is one of the problems the aircraft are suffering from (Groner). A number of researchers have devised ways to monitor corrosion including the use of piezoceramics. A number of studies have experimented with using piezoceramics on aluminum beams and plates to test their applicability for SHM on aircraft. Not only were the researchers able to detect the corrosion damage, but they were also able to locate and quantify it.
Steel rebar in beams are much thicker than the specimens previously used in
corrosion detection. The rebar is also encased in concrete and is not able to transfer vibration freely as was the case in Simmer’s study. However, a study conducted by Wang et. al showed that guided waves can be used to detect debonding damage. Their study did not specifically deal with corrosion, but their methods may still be highly
applicable. As the rebar corrodes, the cross sectional area of the rebar will decrease. As a result, there should be corresponding debonding. In their study, piezoceramics were used to generated a guided wave signal at one section and detect the signal at other sections. The wave signal was altered as it passed through debonded sections. They was able to determine the length and location of the debonded sections. The wave signal travels faster through debonded sections. The location can be determined by analyzing the reflected wave signals. Wang found relationships between the amplitude and phase difference and the debonding location. Their results should be applicable to corroded rebar, and it is expected similar patterns will emerge. Corrosion Process
Corrosion is an electrochemical process that degrades steel and generates rust by-products. Steel is a man-made material that stores energy as a result of its manufacturing process; the stored energy makes the steel very reactive with the environment to return to its natural state as iron ore (Corrosion Protection: Concrete Bridges – CP:CB). When steel rebar is placed in the concrete, the alkalinity causes the steel to form a thin protective layer. This layer makes the steel inactive and resistant to corrosion (CP:CB). Cracks commonly form in reinforced concrete; chloride ions can enter through these cracks and accumulate on the rebar. After a certain concentration of chloride accumulates, the protective layer of steel is destroyed (CP:CB). The cracks form a channel for moisture and oxygen to reach and react with the steel. Corrosion can also be induced by elements besides chloride, but chloride is the main catalyst. The concrete and steel rebar form a closed loop for a circuit to form. Parts of the steel become anodic while others become cathodic. The concrete acts as an electrolyte to complete the electrochemical circuit (CP:CB). At the cathode, the iron is oxidized, and then further reacts to become rust products. The follow equations and comments from the Corrosion Protection: Concrete Bridges document on the Federal Highway Administration’s (FHWA) website explain the reactions that take place on the steel rebar.
1. At the anode, iron is oxidized to the ferrous state, releasing electrons.
Fe Fe +2 + 2 e - (1)
2. At the cathode, these electrons combine with oxygen and moisture to form hydroxide ions.
½ O 2 + H 2O + 2 e - 2 OH - (2)
3. The ferrous ions combine with hydroxyl ions to produce ferrous hydroxide. Then the latter is further oxidized in the presence of moisture to form ferric oxide.
Fe +2 + 2 OH - Fe(OH) 2 (3)
4 Fe(OH) 2 + 2 H 2O + O 2 4 Fe(OH) 3 (4)
2 Fe(OH) 3 Fe 2O 3 + 3 H 2O (5)
Effects of Corrosion in Reinforced Concrete
After corrosion has started, the resulting reactions can affect the structural integrity of reinforced concrete. As the reaction proceeds, steel is consumed. Accordingly, the diameter and mass of the rebar are decreased. The reduction of diameter leads to the loss of bond with the surrounding concrete (CB:CP). This can lead to major problems in pre-stressed concrete where the interface with the steel is important. The corrosion process also creates rust by-products. The by-products can eventually occupy more volume than the initial steel rebar (CB:CP). The by-products then cause stress on the surrounding concrete. As the by-products and resulting stress increase, delamination and spalling of concrete occur (CB:CP). The rebar could then be more exposed to the environment, and the corrosion rate can increase. Accelerated Corrosion Testing
Corrosion takes place over a number of years. As a result, researchers have found different ways to accelerate corrosion for testing purposes. The Florida Depart of Transportation has a standardized method for evaluating corrosion resistant coatings. The setup involves casting a No. 4 rebar within a 10.2 cm x 14.6 cm concrete cylinder so that the rebar sticks out of the cylinder at one end (Brown). After proper curing, the sample is placed in a tank with 5% NaCl solution at a height of 7.5 cm in the tank for twenty-eight days. A bare piece of No. 5 rebar is placed in the tank and connected to the negative terminal of a DC power supply. The positive terminal is connected to the rebar protruding from the concrete cylinder (Brown). The test is initiated by turning on the power supply and setting it to 6V. The NaCl solution is filtered, circulated, and maintained at a concentration of 5%. The current is measured by using a multimeter and using Ohm’s law (Brown). The accumulation of corrosion products will increase stress in the concrete and cause it to crack. When this happens, the current will increase sharply (Brown). The resistance and time to cracking can then be plotted to compare different test specimens.
Another method, used by Simmers et. al., corroded aluminum samples in a very short period of time. Hydrochloric acid was used to induce mass loss in the test samples. The method also involves the simplest setup. The acid is simply applied to the material to be tested until the desired level of corrosion is reached (Simmers). Existing Corrosion Sensors and Preventive Measures Corrosion has been a problem in reinforced concrete for a number of years. As a result a number of solutions have been found to help reduce the effect of corrosion. Earlier, the correlation between the use of de-icing salts and the appearance of corrosion
in bridges was mentioned. Since the two have been linked, the use of de-icing salts has not decreased. There has been a lack of feasible alternatives to alleviate its use (CB:CP). The FHWA also recognize corrosion as a High Priority Area and has conducted numerous research. Most corrosion sensors currently being examined consist of electrochemical sensors. The sensors consist of different electrodes used to detect different properties such as pH and chloride content. In a few reported cases, some of the electrodes did not show good stability over time (Duffo, “Characterization”). The change in environmental conditions affects many materials used in these studies which made it difficult for researchers to find a reference electrode. Environmental factors may impact potential reading and make it possible to misinterpret the condition of the rebar (Duffo, “Characterization” 1019).
Experimental Procedure
The testing was done on a small-scale reinforced concrete beam. The dimensions of the beam are 6” x 6” x 20”. The tension reinforcement consisted of No. 3 rebar while the compression and shear reinforcement consisted of No. 2 rebar. The below diagrams outlines the design for the RC beam:
Once two rebar cages were manufactured, piezoceramic sensors were attached to the rebar cages at sixteen different locations. The below diagram shows the approximate locations:
The ceramic patches were bonded directly to the rebar using epoxy. The piezoceramic sensors consisted of 5A piezoceramics that were cut into 0.25” x 10mm patches for the top rebar and 10mm x 10mm patches for the bottom. Liquid tape was used protect the sensors. The patches were placed so that the wires would exit the beam through the top. To protect the patches from damage during casting of the beam, the patches were covered with mortar (App. C). To prevent water damage, concrete sealant was used on the mortar cubes.
After mortar was placed, baseline data was taken using a D-space control box. The control box had slots for data collection from eight different sensors. For most tests fewer slots were used. The below diagram outlines the equipment arrangement:
A limited number of sensors were also used as actuators to speed up the data collection process. After data collection was completed, thirty-seven data files were created for each data set. To simulate accelerated corrosion, hydrochloric acid was used to corrode the steel rebar. From initial experiments, a thirty percent mass loss was observed in the first twelve hours of exposure to the acid. After this initial period, it was observed each subsequent twelve-hour period had a much smaller mass loss. For the experiment, the acid will be
replaced every twelve hours to ensure corrosion is taking place. Also, at each time that acid was replaced, data was also collected from the sensors. Before the beam is cast, channels must be created to ensure there is a way to corrode the rebar inside of the beam. In this experiment, the channels are created by using traditional straws that will run from the top surface of the beam to the rebar to be corroded. The acid can be injected and replaced by using a pipette. To ensure corrosion takes place around the circumference of the rebar, a transporting material, paper, will be wrapped around the rebar to ensure equal distribution of the acid. After the necessary arrangements are made for the acid, the beam may be cast. The concrete used in the beam is listed in Appendix C.
During casting care must be taken to ensure the wires protrude out of the top surface of the beam and that the channels to the rebar remain unblocked. Also, during concrete placement, the distribution of concrete should be observed to ensure there are no significant voids in the beam. The concrete was consolidated by using a vibrator. The beam should be allowed to cure for approximately one week. Because of time constraints, the beam was allowed to cure for three days. Data was collected at each 12 – hour period during the curing period. This was to observe if the strength development of the concrete would interfere with data collected in the corrosion period. For this experiment, the corrosion period was 60-hours.
Results
From the data, they seemed to be an overall decrease in signal. However, observing the plots of the voltage of the sensor revealed there was no strong evidence for a trend to be identified (App. D).
Signal Change in Sensors
68
5350
0
10
20
30
40
50
60
70
80
Signal Decreasing Signal Increasing No Change
Nu
mb
er
of
Sen
so
rs
Signal Change in Sensors
40%
31%
29%
Signal Decreasing Signal Increasing No Change
The above figures represent the observed change in the plots from the initial data
set to the data set taken after sixty hours of corrosion. The pie and bar chart show that the majority of the sensors showed a decrease in voltage. The next largest group showed an increase in voltage. The smallest group showed no or negligible change in voltage. Though there is a numerical difference, the pie chart displays that there is no identifiable change due to corrosion. Nearly one-third of the signals registered no change. For the practicality of using piezoceramic materials for corrosion detection, this group must be much smaller. In addition, the percentage of sensors that showed a signal increase and decrease must be more differentiated. The pie chart identifies the two groups as only have a nine percent difference - a 15 sensor numerical difference. However, the above figures do not rule out the possibility of their use because of many possible errors in the experimental setup.
The charts attempt to draw a primitive conclusion. This, however, is not necessarily indicative of the signal change as many plots had wide variation of voltage during the corrosion period. Also many showed slight changes in voltage.
0 10 20 30 40 50 600
1
2
3
4
5
6
7
8x 10
5
Time(hours)
Sensor
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S2
S3
E
F
H
G
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1
2
3
4
5
6
7x 10
5
Time(hours)
Sensor
voltage
B11
B9
B7
B12
B10
B8
Tests 186 and 190
From figures 7-11, the signal for sensor R9 shows a sharp decrease from the initial signal to a voltage of approximately zero. This sensor was located close to a corrosion site and may have been damaged by the acid.
0 10 20 30 40 50 600
0.5
1
1.5
2
2.5
3
3.5
4x 10
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Sensor
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R7
R12
R10
R8
0 10 20 30 40 50 600
1
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3
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5
6
7
8
9x 10
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Time(hours)
Sensor
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R11
R9
R7
R12
R10
R8
Tests 171 and 183
Acknowledgements
Dr. Haichang Gu
Dr. Gangbing Song
Dr. Y. L. Mo
The research study described herein was sponsored by the National Science Foundation under the Award No. EEC-0649163. The opinions expressed in this study are those of the authors and do not necessarily reflect the views of the sponsor.
References
Brown, Robert P. Kessler, R. J. “Florida Method of Test for An Accelerated Laboratory Method for Corrosion Testing of Reinforced Concrete Using Impressed Current.” September 1, 2000. Accessed June 18, 2009. <http://www.dot.state.fl.us/statematerialsoffice/administration/resources/library/publications/fstm/methods/fm5-522.pdf>
“Corrosion Protection: Concrete Bridges.” Turner-Fairbank Highway Research Center.
Federal Highway Administration. Accessed July 23, 2009. <http://www.tfhrc.gov/structur/corros/corros.htm>
Duffo, Gustavo S. Farina, Silvia B. “Development of an embeddable sensor to monitor
the corrosion process of new and existing reinforced concrete structures.” Construction and Building Materials. Volume 23. Issue 8. August 2009. Pages 2746-2751.
Duffo, Gustavo S. Farina, Silvia B. Giordano, C. M. “Characterization of Solid
Embeddable Reference Electrodes for Corrosion Monitoring in Reinforced Concrete Structures.” Electrochimica Acta.Volume 54. Issue 3. January 1, 2008. Pg. 1010 – 1020.
Simmers Jr., Garnett E; Sodano, Henry A.; Park, Gyuhae; Inman, Daniel J. “Detection of
corrosion using piezoelectric impedance-based structural health monitoring.” AIAA Journal. 2006. Volume 44. Issue 11. Page 2800-2803.
Simmers Jr., Garnett E; Sodano, Henry A.; Park, Gyuhae; Inman, Daniel J. “Impedance
based corrosion detection” Proceedings of SPIE, the international society for optical engineering. 2005. Volume 5767. Page 328.
Wang, Ying; Zhu, Xinqun; Hao, Hong; Ou, Jinping. “Guided Wave Propagation and Spectral Element Method for Debonding Damage Assessment in RC Structures.” Journal of Sound and Vibration. Vol. 324. No. 3-5. July 24, 2009. pg. 751-772
Appendix A: Notation
g – gram lb – pound in. – inches RC – reinforced concrete mm – millimeter
Appendix B: Corrosion Test Results
Steel Corrosion Results
Time (hrs.) 0 12 24 36 48 60 72 84
Sample 1 Mass (g) 4.6 3.2 2.9 2.7 2.5 2.4 2.2 2.0
Sample 2 Mass (g) 8.3 5.8 5.3 5.0 4.6 4.3 4.1 3.8
Sample 3 Mass (g) 11.0 7.4 6.9 6.4 5.9 5.6 5.2 4.8
Steel Corrosion Rate
0
2
4
6
8
10
12
0 20 40 60 80 100
Time (hrs.)
Mass (
g)
Sample 1 Mass
Sample 2 Mass
Sample 3 Mass
Percentage Lost Over Time
Time (hrs.) 0 12 24 36 48 60 72 84
Sample 1 Mass (g) 0.0 30.4% 37.0% 41.3% 45.7% 47.8% 52.2% 56.5%
Sample 2 Mass (g) 0.0 30.1% 36.1% 39.8% 44.6% 48.2% 50.6% 54.2%
Sample 3 Mass (g) 0.0 32.7% 37.3% 41.8% 46.4% 49.1% 52.7% 56.4%
Mass Loss Percentage Over Time
0
0.1
0.2
0.3
0.4
0.5
0.6
0 20 40 60 80 100
Time (hrs.)
Perc
en
t o
f M
ass L
ost
Sample 1 Mass
Sample 2 Mass
Sample 3 Mass
Appendix C: Mix Designs
Mortar
Component Parts
Water 0.5
Sand 1.5
Cement 1
Concrete
Component Weight (lbs)
Water 6 +/- 0.5
Cement 13.5
Sand 17
Aggregate 39
Appendix D: Sensor Voltage Plots
Note: Unless otherwise stated the ratio is set to 1.
0 10 20 30 40 50 600
2
4
6
8
10
12
14
16
18x 10
4
Time(hours)
Sensor
voltage
B11
B9
B7
B12
B10
B8
Figure 1 – Test 170; Actuator: H; Sensors: B11 B9 B7 B12 B10 B8
0 10 20 30 40 50 60500
1000
1500
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2500
3000
3500
4000
4500
5000
5500
Time(hours)
Sensor
voltage
B11
B9
B7
B12
B10
B8
Figure 2 – Test 176; Actuator: G; Sensors: B11 B9 B7 B12 B10 B8
0 10 20 30 40 50 600
0.5
1
1.5
2
2.5
3x 10
4
Time(hours)
Sensor
voltage
B11
B9
B7
B12
B10
B8
Figure 3 – Test 184; Actuator E; Sensors: B11 B9 B7 B12 B10 B8
0 10 20 30 40 50 601
2
3
4
5
6
7
8
9x 10
5
Time(hours)
Sensor
voltage
B11
B9
B7
B12
B10
B8
Figure 4 – Test 189; Actuator S1; Sensors: B11 B9 B7 B12 B10 B8; Ratio = 0.1
0 10 20 30 40 50 600
1
2
3
4
5
6
7x 10
5
Time(hours)
Sensor
voltage
B11
B9
B7
B12
B10
B8
Figure 5 – Test 190; Actuator: S2; Sensors: B11 B9 B7 B12 B10 B8; Ratio = 0.1
0 10 20 30 40 50 600
2
4
6
8
10
12
14x 10
4
Time(hours)
Sensor
voltage
B11
B9
B7
B12
B10
B8
Figure 6 – Test 191; Actuator: S3; Sensors: B11 B9 B7 B12 B10 B8; Ratio = 0.1
0 10 20 30 40 50 600
0.5
1
1.5
2
2.5
3
3.5
4x 10
5
Time(hours)
Sensor
voltage
R11
R9
R7
R12
R10
R8
Figure 7 – Test 171; Actuator: H; Sensors: R11 R9 R7 R12 R10 R8
0 10 20 30 40 50 600
1000
2000
3000
4000
5000
6000
7000
8000
9000
Time(hours)
Sensor
voltage
R11
R9
R7
R12
R10
R8
Figure 8 – Test 179; Actuator: F; Sensors: R11 R9 R7 R12 R10 R8
0 10 20 30 40 50 600
1
2
3
4
5
6
7
8
9x 10
4
Time(hours)
Sensor
voltage
R11
R9
R7
R12
R10
R8
Figure 9 – Test 183; Actuator E; Sensors: R11 R9 R7 R12 R10 R8
0 10 20 30 40 50 600
1
2
3
4
5
6
7
8
9x 10
5
Time(hours)
Sensor
voltage
R11
R9
R7
R12
R10
R8
Figure 10 – Test 199; Actuator: S2; Sensors: R11 R9 R7 R12 R10 R8; Ratio = 0.1
0 10 20 30 40 50 600
0.5
1
1.5
2
2.5
3x 10
6
Time(hours)
Sensor
voltage
R11
R9
R7
R12
R10
R8
Figure 11 – Test 200 Actuator: S3; Sensors: R11 R9 R7 R12 R10 R8; Ratio = 1
0 10 20 30 40 50 600
0.5
1
1.5
2
2.5
3
3.5x 10
5
Time(hours)
Sensor
voltage
S1
S2
S3
Empty
Empty
Empty
Figure 12 – Test 172; Actuator: H; Sensors: S1 S2 S3 0 0 0
0 10 20 30 40 50 600
2
4
6
8
10
12
Time(hours)
Sensor
voltage
S1
S2
S3
Empty
Empty
Empty
Figure 13 – Test 203; Actuator: R9; Sensors: S1 S2 S3 0 0 0
0 10 20 30 40 50 600
2
4
6
8
10
12
14x 10
4
Time(hours)
Sensor
voltage
S1
S2
S3
Empty
Empty
Empty
Figure 14 – Test 204; Actuator: R10; Sensors: S1 S2 S3 0 0 0
0 10 20 30 40 50 600
1
2
3
4
5
6
7
8
9x 10
5
Time(hours)
Sensor
voltage
S1
S2
S3
Empty
Empty
Empty
Figure 15 – Test 205; Actuator: B9; Sensors: S1 S2 S3 0 0 0; Ratio = 0.1
0 10 20 30 40 50 600
2
4
6
8
10
12
14x 10
5
Time(hours)
Sensor
voltage
S1
S2
S3
Empty
Empty
Empty
Figure 16 – Test 206; Actuator: B10; Sensors: S1 S2 S3 0 0 0; Ratio = 0.1
0 10 20 30 40 50 600
0.5
1
1.5
2
2.5
3x 10
5
Time(hours)
Sensor
voltage
E
G
F
Empty
Empty
Empty
Figure 17 – Test 173; Actuator: H; Sensors: E G F 0 0 0
0 10 20 30 40 50 600
2000
4000
6000
8000
10000
12000
14000
Time(hours)
Sensor
voltage
E
F
H
Empty
Empty
Empty
Figure 18 – Test 177 Actuator: G; Sensors: E F H 0 0 0
0 10 20 30 40 50 600
500
1000
1500
2000
2500
3000
3500
4000
Time(hours)
Sensor
voltage
E
G
H
Empty
Empty
Empty
Figure 19 – Test 181; Actuator: F; Sensors: E G H 0 0 0
0 10 20 30 40 50 600
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5x 10
4
Time(hours)
Sensor
voltage
F
G
H
Empty
Empty
Empty
Figure 20 – Test 185; Actuator: E; Sensors: F G H 0 0 0
0 10 20 30 40 50 600
1000
2000
3000
4000
5000
6000
7000
8000
9000
Time(hours)
Sensor
voltage
B11
B9
B7
S1
S2
S3
Figure 21 – Test 174; Actuator: G; Sensors: B11 B9 B7 S1 S2 S3
0 10 20 30 40 50 600
500
1000
1500
2000
2500
Time(hours)
Sensor
voltage
B11
B9
B7
S1
S2
S3
Figure 22 – Test 178; Actuator: F; S: B11 B9 B7 S1 S2 S3
0 10 20 30 40 50 600
0.5
1
1.5
2
2.5
3x 10
4
Time(hours)
Sensor
voltage
B12
B10
B8
S1
S2
S3
Figure 23 – Test 182; Actuator: E; Sensors: B12 B10 B8 S1 S2 S3
0 10 20 30 40 50 600
1
2
3
4
5
6
7
8x 10
5
Time(hours)
Sensor
voltage
S2
S3
E
F
H
G
Figure 24 – Test 186; Actuator: S1; Sensors: S2 S3 E F H G; Ratio = 0.1
0 10 20 30 40 50 600
1
2
3
4
5
6
7x 10
5
Time(hours)
Sensor
voltage
S1
S3
E
F
H
G
Figure 25 – Test 187; Actuator: S2; Sensors: S1 S3 E F H G; Ratio = 0.1
0 10 20 30 40 50 600
1
2
3
4
5
6x 10
5
Time(hours)
Sensor
voltage
S1
S2
E
F
H
G
Figure 26 – Test 188; Actuator: S3; Sensors: S1 S2 E F H G; Ratio = 1.00
0 10 20 30 40 50 600
0.5
1
1.5
2
2.5
3
3.5
4
4.5x 10
6
Time(hours)
Sensor
voltage
S1
B8
B9
B10
B11
B12
Figure 27 – Test 192; Actuator: B7; Sensors: S1 B8 B9 B10 B11 B12; Ratio = 0.1
0 10 20 30 40 50 600
2
4
6
8
10
12
14x 10
5
Time(hours)
Sensor
voltage
S1
B7
B9
B10
B11
B12
Figure 28 – Test 193; Actuator: B8; Sensors: S1 B7 B9 B10 B11 B12; Ratio = 0.1
0 10 20 30 40 50 600
0.5
1
1.5
2
2.5
3x 10
6
Time(hours)
Sensor
voltage
S1
B7
B8
B10
B11
B12
Figure 29 – Test 194; Actuator: B9; Sensors: S1 B7 B8 B10 B11 B12; Ratio = 0.1;
0 10 20 30 40 50 600
0.5
1
1.5
2
2.5
3x 10
6
Time(hours)
Sensor
voltage
S1
B7
B8
B9
B11
B12
Figure 30 – Test 195; Actuator: B10; Sensors: S1 B7 B8 B9 B11 B12; Ratio = 0.1
0 10 20 30 40 50 600
2
4
6
8
10
12
14x 10
5
Time(hours)
Sensor
voltage
S1
B7
B8
B9
B10
B12
Figure 31 – Test 196; Actuator: B11; Sensors: S1 B7 B8 B9 B10 B12; Ratio = 0.1
0 10 20 30 40 50 600
0.5
1
1.5
2
2.5x 10
6
Time(hours)
Sensor
voltage
S1
B7
B8
B9
B10
B11
Figure 32 – Test 197; Actuator: B12; Sensors: S1 B7 B8 B9 B10 B11; Ratio = 0.1
0 10 20 30 40 50 600
10
20
30
40
50
60
Time(hours)
Sensor
voltage
R11
Empty
R7
R12
R10
R8
Figure 33 – Test 201; Actuator: R9; Sensors: R11 0 R7 R12 R10 R8
Missing data files made the following tests incompatible with the plotting program
*Test 175; Actuator: G; S: R11 R9 R7 R12 R10 R8 *Test 198; Actuator: S1; S: R11 R9 R7 R12 R10 R8; Ratio = 0.1 *Test 202; Actuator: R10; S: R11 R9 R7 R12 0 R8
Appendix E – Recommendations for Future Work
Figure 1 – View of Ferrite Core Housing
Figure 2 – Picture of Ferrite Cores
Source: http://www.intermark-usa.com/products/EMC/Ferrite/RFC_series.shtml
