Name: quantifying the relative thickness of conductive ferromagnetic materials using detector coil-based pulsed eddy current sensors
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Description: Watch this Scientific Journal Video about Quantifying the Relative Thickness of Conductive Ferromagnetic Materials Using Detector Coil-Based Pulsed Eddy Current Sensors at JoVE.com

The authors would like to acknowledge the contributions made by Michael Behrens and Damith Abeywardana in designing and implementing several sensing hardware components. Research supervision roles played by Alen Alempijevic, Teresa Vidal-Calleja, Gamini Dissanayake, and Sarath Kodagoda, as well as contributions made by all persons and organizations who funded and partnered with the Critical Pipes Project, are also acknowledged.

1. Extracting the decay rate &#946; from an available detector coil-based PEC signal
<ol>
	<li>Express an available experimentally captured PEC signal (i.e., a time domain detector coil voltage (denoted as V(t))) in the logarithmic form of ln[V(t)]. A typical PEC signal expressed in the form of ln[V(t)] is shown in Figure 1.</li>
	<li>Find a linear region in the form of <img align="center" alt="Equation 2" src="/files/ftp_uploa...

<ol>
	<li>Garc&#237;a-Mart&#237;n, J., G&#243;mez-Gil, J., V&#225;zquez-S&#225;nchez, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-destructive+techniques+based+on+eddy+current+testing.">Non-destructive techniques based on eddy current testing.</a> Sensors. 11 (3), 2525-2565 (2011).</li><li>Huang, C., Wu, X., Xu, Z., Kang, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ferromagnetic+material+pulsed+eddy+current+testing+signal+modeling+by+equivalent+multiple-coil-coupling+approach.">Ferromagnetic material pulsed eddy current testing signal modeling by equivalent multiple-coil-coupling approach.</a> Non-Destructive Testing and Evaluation International. 44 (2), 163-168 (2011).</li><li>Xu, Z., Wu, X., Li, J., Kang, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+wall+thinning+in+insulated+ferromagnetic+pipes+using+the+time-to-peak+of+differential+pulsed+eddy-current+testing+signals.">Assessment of wall thinning in insulated ferromagnetic pipes using the time-to-peak of differential pulsed eddy-current testing signals.</a> Non-Destructive Testing and Evaluation International. 51, 24-29 (2012).</li><li>Huang, C., Wu, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+improved+ferromagnetic+material+pulsed+eddy+current+testing+signal+processing+method+based+on+numerical+cumulative+integration.">An improved ferromagnetic material pulsed eddy current testing signal processing method based on numerical cumulative integration.</a> Non-Destructive Testing and Evaluation International. 69, 35-39 (2015).</li><li>Chen, X., Lei, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrical+conductivity+measurement+of+ferromagnetic+metallic+materials+using+pulsed+eddy+current+method.">Electrical conductivity measurement of ferromagnetic metallic materials using pulsed eddy current method.</a> Non-Destructive Testing and Evaluation International. 75, 33-38 (2015).</li><li>Ulapane, N., Alempijevic, A., Valls Miro, J., Vidal-Calleja, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-destructive+evaluation+of+ferromagnetic+material+thickness+using+Pulsed+Eddy+Current+sensor+detector+coil+voltage+decay+rate.">Non-destructive evaluation of ferromagnetic material thickness using Pulsed Eddy Current sensor detector coil voltage decay rate.</a> Non-Destructive Testing and Evaluation International. 100, 108-114 (2018).</li><li>Ulapane, N., Nguyen, L., Valls Miro, J., Dissanayake, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Solution+to+the+Inverse+Pulsed+Eddy+Current+Problem+Enabling+3D+Profiling.">A Solution to the Inverse Pulsed Eddy Current Problem Enabling 3D Profiling.</a> IEEE Conference on Industrial Electronics and Applications. , (2018).</li><li>Ulapane, N., Alempijevic, A., Vidal Calleja, T., Valls Miro, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pulsed+Eddy+Current+Sensing+for+Critical+Pipe+Condition+Assessment.">Pulsed Eddy Current Sensing for Critical Pipe Condition Assessment.</a> Sensors. 17 (10), 2208 (2017).</li><li>Valls Miro, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+live+test-bed+for+the+advancement+of+condition+assessment+and+failure+prediction+research+on+critical+pipes.">A live test-bed for the advancement of condition assessment and failure prediction research on critical pipes.</a> Proceedings of the Leading-Edge Strategic Asset Management Conference (LESAM13). , (2013).</li><li>Valls Miro, J., Ulapane, N., Shi, L., Hunt, D., Behrens, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Robotic+pipeline+wall+thickness+evaluation+for+dense+nondestructive+testing+inspection.">Robotic pipeline wall thickness evaluation for dense nondestructive testing inspection.</a> Journal of Field Robotics. 35 (8), 1293-1310 (2018).</li><li>Valls Miro, J., Hunt, D., Ulapane, N., Behrens, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Towards+Automatic+Robotic+NDT+Dense+Mapping+for+Pipeline+Integrity+Inspection.">Towards Automatic Robotic NDT Dense Mapping for Pipeline Integrity Inspection.</a> Field and Service Robotics. , 319-333 (2018).</li><li>Chen, X., Lei, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrical+conductivity+measurement+of+ferromagnetic+metallic+materials+using+pulsed+eddy+current+method.">Electrical conductivity measurement of ferromagnetic metallic materials using pulsed eddy current method.</a> Non-Destructive Testing and Evaluation International. 75, 33-38 (2015).</li><li>Desjardins, D., Krause, T. W., Clapham, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transient+eddy+current+method+for+the+characterization+of+magnetic+permeability+and+conductivity.">Transient eddy current method for the characterization of magnetic permeability and conductivity.</a> Non-Destructive Testing and Evaluation International. 80, 65-70 (2016).</li><li>Chen, X., Lei, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Excitation+current+waveform+for+eddy+current+testing+on+the+thickness+of+ferromagnetic+plates.">Excitation current waveform for eddy current testing on the thickness of ferromagnetic plates.</a> Non-Destructive Testing and Evaluation International. 66, 28-33 (2014).</li><li>Ulapane, N., Nguyen, L., Valls Miro, J., Alempijevic, A., Dissanayake, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Designing+a+pulsed+eddy+current+sensing+set-up+for+cast+iron+thickness+assessment.">Designing a pulsed eddy current sensing set-up for cast iron thickness assessment.</a> 12th IEEE Conference on Industrial Electronics and Applications (ICIEA). , 901-906 (2017).</li><li>Sophian, A., Tian, G., Fan, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pulsed+eddy+current+non-destructive+testing+and+evaluation:+A+review.">Pulsed eddy current non-destructive testing and evaluation: A review.</a> Chinese Journal of Mechanical Engineering. 30 (3), 500 (2017).</li><li>Sophian, A., Tian, G. Y., Taylor, D., Rudlin, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+of+a+pulsed+eddy+current+sensor+for+detection+of+defects+in+aircraft+lap-joints.">Design of a pulsed eddy current sensor for detection of defects in aircraft lap-joints.</a> Sensors and Actuators A: Physical. 101 (1-2), 92-98 (2002).</li><li>Li, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=System+identification-based+frequency+domain+feature+extraction+for+defect+detection+and+characterization.">System identification-based frequency domain feature extraction for defect detection and characterization.</a> Non-Destructive Testing and Evaluation International. 98, 70-79 (2018).</li><li>Ulapane, N., Nguyen, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Review+of+Pulsed-Eddy-Current+Signal+Feature-Extraction+Methods+for+Conductive+Ferromagnetic+Material-Thickness+Quantification.">Review of Pulsed-Eddy-Current Signal Feature-Extraction Methods for Conductive Ferromagnetic Material-Thickness Quantification.</a> Electronics. 8 (5), 470 (2019).</li><li>Nguyen, L., Valls Miro, J., Shi, L., Vidal-Calleja, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gaussian+Mixture+Marginal+Distributions+for+Modelling+Remaining+Pipe+Wall+Thickness+of+Critical+Water+Mains+in+Non-Destructive+Evaluation.">Gaussian Mixture Marginal Distributions for Modelling Remaining Pipe Wall Thickness of Critical Water Mains in Non-Destructive Evaluation.</a> arXiv. , 01184 (2019).</li><li>Ulapane, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gaussian+process+for+interpreting+pulsed+eddy+current+signals+for+ferromagnetic+pipe+profiling.">Gaussian process for interpreting pulsed eddy current signals for ferromagnetic pipe profiling.</a> 2014 9th IEEE Conference on Industrial Electronics and Applications. , 1762-1767 (2014).</li><li>Ulapane, A. M. N. N. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Nondestructive evaluation of ferromagnetic critical water pipes using pulsed eddy current testing (Doctoral dissertation). , (2016).</li><li>Thiyagarajan, K., Kodagoda, S., Alvarez, J. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+instrumentation+system+for+smart+monitoring+of+surface+temperature.">An instrumentation system for smart monitoring of surface temperature.</a> 2016 14thInternational Conference on Control, Automation, Robotics and Vision (ICARCV). , 1-6 (2016).</li><li>Thiyagarajan, K., Kodagoda, S., Van Nguyen, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Predictive+analytics+for+detecting+sensor+failure+using+autoregressive+integrated+moving+average+model.">Predictive analytics for detecting sensor failure using autoregressive integrated moving average model.</a> 2017 12th IEEE Conference on Industrial Electronics and Applications (ICIEA). , 1926-1931 (2017).</li><li>Thiyagarajan, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Robust sensor technologies combined with smart predictive analytics for hostile sewer infrastructures (Doctoral dissertation). , (2018).</li><li>Thiyagarajan, K., Kodagoda, S., Van Nguyen, L., Ranasinghe, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sensor+failure+detection+and+faulty+data+accommodation+approach+for+instrumented+wastewater+infrastructures.">Sensor failure detection and faulty data accommodation approach for instrumented wastewater infrastructures.</a> IEEE Access. 6 (56), 562-574 (2018).</li><li>Thiyagarajan, K., Kodagoda, S., Ranasinghe, R., Vitanage, D., Iori, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Robust+sensing+suite+for+measuring+temporal+dynamics+of+surface+temperature+in+sewers.">Robust sensing suite for measuring temporal dynamics of surface temperature in sewers.</a> Scientific Reports. 8, 16020 (2018).</li><li>Thiyagarajan, K., Kodagoda, S., Van Nguyen, L., Wickramanayake, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gaussian+Markov+random+fields+for+localizing+reinforcing+bars+in+concrete+infrastructure.">Gaussian Markov random fields for localizing reinforcing bars in concrete infrastructure.</a> 35th International Symposium on Automation and Robotics in Construction. , 1052-1058 (2018).</li><li>Thiyagarajan, K., Kodagoda, S., Ulapane, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Data-driven+machine+learning+approach+for+predicting+volumetric+moisture+content+of+concrete+using+resistance+sensor+measurements.">Data-driven machine learning approach for predicting volumetric moisture content of concrete using resistance sensor measurements.</a> 2016 IEEE 11th Conference on Industrial Electronics and Applications. , 1288-1293 (2016).</li><li>Giovanangelia, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+and+Development+of+Drill-Resistance+Sensor+Technology+for+Accurately+Measuring+Microbiologically+Corroded+Concrete+Depths.">Design and Development of Drill-Resistance Sensor Technology for Accurately Measuring Microbiologically Corroded Concrete Depths.</a> 36th International Symposium on Automation and Robotics in Construction. , (2019).</li><li>Wickramanayake, S., Thiyagarajan, K., Kodagoda, S., Piyathilaka, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Frequency+Sweep+Based+Sensing+Technology+for+Non-destructive+Electrical+Resistivity+Measurement+of+Concrete.">Frequency Sweep Based Sensing Technology for Non-destructive Electrical Resistivity Measurement of Concrete.</a> 36th International Symposium on Automation and Robotics in Construction. (771), (2019).</li><li>Ulapane, N., Wickramanayake, S., Kodagoda, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pulsed+Eddy+Current+Sensing+for+Condition+Assessment+of+Reinforced+Concrete.">Pulsed Eddy Current Sensing for Condition Assessment of Reinforced Concrete.</a> 14th IEEE Conference on Industrial Electronics and Applications. , (2020).</li></ol>

A protocol to quantify the relative thickness (i.e., thickness as a percentage with respect to a reference) of conductive ferromagnetic materials using detector coil-based PEC sensors was presented. The main advantage of this method is the ability to overcome the calibration requirement (i.e., overcome the need to measure or estimate the magnetic permeability and electrical conductivity of the material being inspected to enable thickness quantification). The protocol involves logarithmic representation of the time domain...

The pulsed eddy current (PEC) sensing technique is perhaps the most versatile member of the family of eddy current (EC) non-destructive evaluation (NDE) techniques and has many applications in detection and quantification of defects, and the geometry of metals and metallic structures1. Thickness quantification of conductive ferromagnetic wall-like structures, having wall thicknesses of no more than a few millimeters to a few tens of millimeters, is a high demand engineering service in the field of structural health monitoring of infrastructure. Critical infrastructure made of ferromagnetic alloys that require this service are commonly available in the energy, water, oil, and gas industries. While PEC sensors can be designed following several architectures, the detector coil-based architecture was determined to be the most effective and commonly used in condition assessment of ferromagnetic materials2,3,4,5. Therefore, it is the detector coil-based PEC sensor architecture that sets the foundation to the problem of thickness quantification of conductive ferromagnetic materials.
The detector coil-based PEC sensor architecture is typically comprised of two concentrically wound, air cored, conductive coils2,3,4,5,6 (typically copper coils). It is quite common to wind these coils to be circular in shape2,3,4,5,6, but occasionally, rectangular shaped coils6 have been used. From the two coils in the sensor, one behaves as an exciter coil while the other acts as the detector coil. In a PEC sensor, the exciter coil is excited by a voltage pulse - something that can be characterized as a Heaviside step function in principle. This pulsed excitation generates a transient magnetic field (called the primary field) around the sensor. When the sensor is placed adjacent to a conductive test piece (e.g., a conductive ferromagnetic wall-like structure), this transient magnetic field induces time varying eddy currents in the test piece. These eddy currents generate a secondary magnetic field (called the secondary field) that opposes the primary field. In response to the resultant effect of the primary and secondary fields, a transient voltage is induced in the detector coil - which becomes the time domain PEC signal of interest for this work.
The PEC sensor detector coil voltage decay rate (denoted as &#946;) has been reported6,7,8 to show the proportionality &#946; <img align="center" alt="Equation 7" src="/files/ftp_upload/59618/59618eq7a.jpg" /> &#956;&#963;d2, when a signal is acquired placing a PEC sensor above a conductive ferromagnetic layer of magnetic permeability &#956;, electrical conductivity &#963;, and thickness d. Although this decay rate signal feature has considerable immunity to parameters such as sensor size, sensor shape, and lift-off6,7,8, which makes the decay rate highly desirable for challenging NDE scenarios such as in situ pipe condition assessment9,10,11, this feature must be calibrated (i.e., &#956;, &#963; of the material being inspected be estimated) to enable thickness (i.e., d) quantification. To enable conventional methods of decay rate-based thickness quantification6,8, this calibration must be done by extracting calibration samples6,8 or by involving eddy current-based material property characterization methods12,13. Alternatively, the complexity of calibration can be avoided by representing thickness in the form of relative thickness. Suppose an NDE exercise is carried out and &#946; values are extracted from signals, then, the &#946; value qualitatively representative of the maximum thickness point in the test piece is considered as a reference (i.e., &#946;ref <img align="center" alt="Equation 7" src="/files/ftp_upload/59618/59618eq7a.jpg" /> &#956;&#963;dmax2); then, the thickness of any other location can be represented as a percentage of the maximum thickness in the form <img align="center" alt="Equation 1" src="/files/ftp_upload/59618/59618eq1g.jpg" />, presenting a relative thickness as the output, which is still useful qualitative information as an NDE output that also carries the simplicity of not having to calibrate for &#956;, &#963;. The protocol presented herein describes the steps to be followed to accomplish this.
Since the decay rate &#946; shows generality to the detector coil-based PEC sensor architecture while showing immunity to parameters of the sensor design as well as lift-off6,7,8,14, practitioners may use any detector coil-based PEC sensing system of their choice on a suitable conductive ferromagnetic material to perform relative thickness quantification following the protocol here. A PEC sensor design example for a conductive ferromagnetic material is available for interested readers15. The signals and results presented in this work were acquired using the PEC system developed by University of Technology Sydney6,8. The conductive ferromagnetic material used for representative results acquired by the PEC system is grey cast iron extracted from a pipe test-bed9,10,11 in Sydney Australia.
It should be noted that the methods, results, and discussions presented in this publication explicitly focus on the use of the detector coil-based PEC sensor architecture&#39;s time domain signal&#39;s decay rate for thickness quantification of conductive ferromagnetic materials. The publication does not include a broader discussion on general conventions of PEC sensing principles and sensor configurations. Other published work16,17,18 can be useful for readers to gain more insight about PEC sensor configurations other than the detector coil-based sensor architecture.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>A Detector Coil-based PEC Sensing System.</td>
			<td>N/A</td>
			<td></td>
			<td>The representative results in this work were generated using the PEC system developed by University of Technology Sydney (UTS), Australia and published in works 6,8. This system may be accessible to readers via collaborating with UTS.</td>
		</tr>
		<tr>
			<td>A suitable conductive ferromagnetic material of varying thickness.</td>
			<td>N/A</td>
			<td></td>
			<td>The representative results in this work were generated by acquiring PEC measurements on grey cast iron test pieces extracted from a pipe test-bed located in Sydney Australia, whose location and vintage details are available in references 9-11. The pipe test-bed as well as the extracted calibration samples may be accessible to readers via collaborating with UTS.</td>
		</tr>
		<tr>
			<td>A computation platform for PEC signal processing</td>
			<td>MathWorks, Natick, MA, USA.</td>
			<td></td>
			<td>A computation platform in which the PEC signal processing algorithm can be coded and executed is required. In this publication, PEC signal processing was done using a software executable named &#34;PEC_Signal_Processor&#34;, produced using MATLAB R2017b, Publisher: MathWorks, Natick, MA, USA.</td>
		</tr>
		<tr>
			<td>An application that can produce a table containing raw PEC signals (e.g., Microsoft Office Excel).</td>
			<td>Microsoft Corporation, One Microsoft Way, Redmond, Washington, USA.</td>
			<td></td>
			<td>Microsoft Office Excel (Office 16) was used for the work of this publication.</td>
		</tr>
	</tbody>
</table>

quantifying the relative thickness of conductive ferromagnetic materials using detector coil-based pulsed eddy current sensors

Thickness quantification of conductive ferromagnetic materials by means of non-destructive evaluation (NDE) is a crucial component of structural health monitoring of infrastructure, especially for assessing the condition of large diameter conductive ferromagnetic pipes found in the energy, water, oil, and gas sectors. Pulsed eddy current (PEC) sensing, especially detector coil-based PEC sensor architecture, has established itself over the years as an effective means for serving this purpose. Approaches for designing PEC sensors as well as processing signals have been presented in previous works. In recent years, the use of the decay rate of the detector coil-based time domain PEC signal for the purpose of thickness quantification has been studied. Such works have established that the decay rate-based method holds generality to the detector coil-based sensor architecture, with a degree of immunity to factors such as sensor shape and size, number of coil turns, and excitation current. Moreover, this method has shown its effectiveness in NDE of large pipes made of grey cast iron. Following such literature, the focus of this work is explicitly PEC sensor detector coil voltage decay rate-based conductive ferromagnetic material thickness quantification. However, the challenge faced by this method is the difficulty of calibration, especially when it comes to applications such as in situ pipe condition assessment since measuring electrical and magnetic properties of certain pipe materials or obtaining calibration samples is difficult in practice. Motivated by that challenge, in contrast to estimating actual thickness as done by some previous works, this work presents a protocol for using the decay rate-based method to quantify relative thickness (i.e., thickness of a particular location with respect to a maximum thickness), without the requirement for calibration.

Representative results within this section have been generated using the PEC signals provided as supplementary material with reference8; as mentioned above, the signals have been captured on grey cast iron samples extracted from the pipe test bed in Sydney Australia, whose location and vintage details are provided in references9,10,11.
Figure 1 sho...

Watch this Scientific Journal Video about Quantifying the Relative Thickness of Conductive Ferromagnetic Materials Using Detector Coil-Based Pulsed Eddy Current Sensors at JoVE.com

Quantifying the Relative Thickness of Conductive Ferromagnetic Materials Using Detector Coil-Based Pulsed Eddy Current Sensors

Here, we present a protocol to quantify the relative thickness (i.e., thickness as a percentage with respect to a reference) of conductive ferromagnetic materials using detector coil-based pulsed eddy current sensors, while overcoming the calibration requirement.

Thickness quantification of conductive ferromagnetic materials by means of non-destructive evaluation (NDE) is a crucial component of structural health ...

Pulsed eddy current sensing is an electro-magnetic sensing technique used to assess certain physical properties and effects of electrically conductive and sometimes ferromagnetic materials. We will introduce the use of a software interface of utilizing the pulsed eddy current signals captured from detector coil based sensor architecture and how to extract information from those signals. This protocol enables a relative thickness quantification of ferromagnetic metallic woolite structures using pulsed eddy current sensing.This technique enables the measurement of the extent of corrosion, graphitization or wool loss of ferromagnetic wool like structures for assessment of there structure and build and integrate it. For pulsed eddy current signal processor installation, locate and execute the PEC signal processor. exe file, and when the interface appears, click next.When the next interface opens, specify the file location for installation and check the add a shortcut to the desktop check box to add the software icon to the desktop. Click next and specify the installation location for the required run time environment. When the installation is complete, click finish.The desktop icon will appear. Before beginning the analysis, use a detector coil based pulsed eddy current sensing unit with an operating electronic box and a detector coil based sensor to collect pulsed eddy current signals from the metal structure of interest. At the end of the scan, export the collected signals from the sensing unit to a compatible, editable word processor and confirm that the signals are arranged as a table.Copy the table to the desktop and double click the desktop icon to run the application. The interface will open. To load the signals, click the load signals tab and select the file containing the signals to import the signals to the software interface.When the number of signals contained within the table containing raw signals appears, click pot signals, and observe the signals plotted in logarithmic scale. Click the zoom tab and adjust the plot window for the linear region until it is clearly visible. The lower and upper margins should encompass a straight line region within the light shade of the signals.If unsure, we recommend generating relative thickness values using several margins and then compare the results. After entering reasonable lower and upper margins for the region, click plot margins and wait for the margins to be plotted in green. Click extract features, the straight line segments will be plotted in red.Click calculate relative thickness to observe the plotting of a histogram of calculated relative thickness values. Click save relative thickness to save the calculated relative thickness values. Enter a file name, and click ok.Then click ok again to confirm the file name. The relative thickness values will be saved as a table on the desktop. The relative thickness values shown on screen are in the form of fractions.One denotes maximum thickness for the 100%reference. Here, the typical shape of a time domain signal expressed in the logarithmic form captured from a detector coil based pulsed eddy current sensor is shown. An indicative linear region of the later stage of the logarithmic signal can be observed, for which t is much greater than 0, and from which the decay rate feature beta is extracted.Here, a set of signals captured on different thicknesses of gray cast iron is shown. This signal corresponds to the maximum thickness with the maximum beta value in the set. Such values can be selected as reference beta values to facilitate quantification of the relative thickness, using the equation as indicated.In this table, the actual relative thickness values and the relative thickness values calculated from beta values obtained from pulsed eddy current signals for a representative experiment, are shown. Here, the corelation between pulsed eddy current signal based relative thickness estimates and the actual relative thickness values can be observed. The effectiveness of the method is demonstrated by the high correlation depicted by the linear relationship.Take care to avoid the current region of the pulsed eddy current signal and to select the linear region at the light stage to allow extraction of the beta feature. Pulsed and other eddy current techniques are commonly used for a anomaly detection, physical property measurements, and for the assessment of non-metallic coatings covering metallic structures.

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Concurrent Quantitative Conductivity and Mechanical Properties Measurements of Organic Photovoltaic Materials using AFM

Organic photovoltaic (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale inhomogeneity of OPV materials affects performance of photovoltaic devices. Thus, understanding of spatial variations in composition as well as electrical properties of OPV materials is of paramount importance for moving PV technology forward.1,2 In this paper, we describe a protocol for quantitative measurements of electrical and mechanical properties of OPV materials with sub-100 nm resolution. Currently, materials properties measurements performed using commercially available AFM-based techniques (PeakForce, conductive AFM) generally provide only qualitative information. The values for resistance as well as Young's modulus measured using our method on the prototypical ITO/PEDOT:PSS/P3HT:PC61BM system correspond well with literature data. The P3HT:PC61BM blend separates onto PC61BM-rich and P3HT-rich domains. Mechanical properties of PC61BM-rich and P3HT-rich domains are different, which allows for domain attribution on the surface of the film. Importantly, combining mechanical and electrical data allows for correlation of the domain structure on the surface of the film with electrical properties variation measured through the thickness of the film.

Organic photovoltaic (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale inhomogeneity of OPV materials affects performance of photovoltaic devices. In this paper, we describe a protocol for quantitative measurements of electrical and mechanical properties of OPV materials with sub-100 nm resolution.

Organic photovoltaic  (OPV) materials are inherently inhomogeneous at the nanometer scale. Nanoscale  inhomogeneity of OPV materials affects performance ...

Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O2 pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (&gt;80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO2, Al2O3, WO3 and Ag4O4.

We describe the experimental method to deposit nanostructured oxide thin films by nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas. By using this method Al-doped ZnO (AZO) films, from compact to hierarchically structured as nano-tree forests, can be deposited.

Nanosecond Pulsed  Laser Deposition (PLD) in the presence of a background gas allows the deposition  of metal oxides with tunable morphology, structure, ...

Using Neutron Spin Echo Resolved Grazing Incidence Scattering to Investigate Organic Solar Cell Materials

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped crystallites. Neutrons are passed through two well defined regions of magnetic field; one before and one after the sample. The two magnetic field regions have opposite polarity and are tuned such that neutrons travelling through both regions, without being perturbed, will undergo the same number of precessions in opposing directions. In this case the neutron precession in the second arm is said to &#34;echo&#34; the first, and the original polarization of the beam is preserved. If the neutron interacts with a sample and scatters elastically the path through the second arm is not the same as the first and the original polarization is not recovered. Depolarization of the neutron beam is a highly sensitive probe at very small angles (&#60;50&#160;&#956;rad) but still allows a high intensity, divergent beam to be used. The decrease in polarization of the beam reflected from the sample as compared to that from the reference sample can be directly related to structure within the sample.
In comparison to scattering observed in neutron reflection measurements the SERGIS signals are often weak and are unlikely to be observed if the in-plane structures within the sample under investigation are dilute, disordered, small in size and polydisperse or the neutron scattering contrast is low. Therefore, good results will most likely be obtained using the SERGIS technique if the sample being measured consist of thin films on a flat substrate and contain scattering features that contains a high density of moderately sized features (30 nm to 5 &#181;m) which scatter neutrons strongly or the features are arranged on a lattice. An advantage of the SERGIS technique is that it can probe structures in the plane of the sample.

Progress has been made in utilizing spin echo resolved grazing incidence scattering (SERGIS) as a neutron scattering technique to probe the length-scales in irregular samples. Crystallites of [6,6]-phenyl-C61-butyric acid methyl ester have been probed using the SERGIS technique and the results confirmed by optical and atomic force microscopy.

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped ...

Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO2-Ag Nanowires Made by Templated Electrodeposition

Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and reduction half reactions, and fast electron (hole) diffusion and charge separation. Nanowires present suitable architectures to meet these requirements. Axially segmented Ag|ZnO and radially segmented (coaxial) TiO2-Ag nanowires with a diameter of 200 nm and a length of 6-20 &#181;m were made by templated electrodeposition within the pores of polycarbonate track-etched (PCTE) or anodized aluminum oxide (AAO) membranes, respectively. In the photocatalytic experiments, the ZnO and TiO2 phases acted as photoanodes, and Ag as cathode. No external circuit is needed to connect both electrodes, which is a key advantage over conventional photo-electrochemical cells. For making segmented Ag|ZnO nanowires, the Ag salt electrolyte was replaced after formation of the Ag segment to form a ZnO segment attached to the Ag segment. For making coaxial TiO2-Ag nanowires, a TiO2 gel was first formed by the electrochemically induced sol-gel method. Drying and thermal annealing of the as-formed TiO2 gel resulted in the formation of crystalline TiO2 nanotubes. A subsequent Ag electrodeposition step inside the TiO2 nanotubes resulted in formation of coaxial TiO2-Ag nanowires. Due to the combination of an n-type semiconductor (ZnO or TiO2) and a metal (Ag) within the same nanowire, a Schottky barrier was created at the interface between the phases. To demonstrate the photocatalytic activity of these nanowires, the Ag|ZnO nanowires were used in a photocatalytic experiment in which H2 gas was detected upon UV illumination of the nanowires dispersed in a methanol/water mixture. After 17 min&#160;of illumination, approximately 0.2 vol% H2 gas was detected from a suspension of ~0.1 g of Ag|ZnO nanowires in a 50 ml 80 vol% aqueous methanol solution.

Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO2-Ag Nanowires Made by Templated Electrodeposition

Procedures are outlined to prepare segmented and coaxial nanowires via templated electrodeposition in nanopores. As examples, segmented nanowires consisting of Ag and ZnO segments, and coaxial nanowires consisting of a TiO2 shell and a Ag core were made. The nanowires were used in photocatalytic hydrogen formation experiments.

Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and ...

Using Microwave and Macroscopic Samples of Dielectric Solids to Study the Photonic Properties of Disordered Photonic Bandgap Materials

Recently, disordered photonic materials have been suggested as an alternative to periodic crystals for the formation of a complete photonic bandgap (PBG). In this article we will describe the methods for constructing and characterizing macroscopic disordered photonic structures using microwaves. The microwave regime offers the most convenient experimental sample size to build and test PBG media. Easily manipulated dielectric lattice components extend flexibility in building various 2D structures on top of pre-printed plastic templates. Once built, the structures could be quickly modified with point and line defects to make freeform waveguides and filters. Testing is done using a widely available Vector Network Analyzer and pairs of microwave horn antennas. Due to the scale invariance property of electromagnetic fields, the results we obtained in the microwave region can be directly applied to infrared and optical regions. Our approach is simple but delivers exciting new insight into the nature of light and disordered matter interaction.

Our representative results include the first experimental demonstration of the existence of a complete and isotropic PBG in a two-dimensional (2D) hyperuniform disordered dielectric structure. Additionally we demonstrate experimentally the ability of this novel photonic structure to guide electromagnetic waves (EM) through freeform waveguides of arbitrary shape.

Disordered structures offer new mechanisms for forming photonic bandgaps and unprecedented freedom in functional-defect designs. To circumvent the computational challenges of disordered systems, we construct modular macroscopic samples of the new class of PBG materials and use microwaves to characterize their scale-invariant photonic properties, in an easy and inexpensive manner.

Recently, disordered photonic materials have been suggested as an alternative to periodic crystals for the formation of a complete photonic bandgap (PBG). ...

Formation of Thick Dense Yttrium Iron Garnet Films Using Aerosol Deposition

Aerosol deposition (AD) is a thick-film deposition process that can produce layers up to several hundred micrometers thick with densities greater than 95% of the bulk. The primary advantage of AD is that the deposition takes place entirely at ambient temperature; thereby enabling film growth in material systems with disparate melting temperatures. This report describes in detail the processing steps for preparing the powder and for performing AD using the custom-built system. Representative characterization results are presented from scanning electron microscopy, profilometry, and ferromagnetic resonance for films grown in this system. As a representative overview of the capabilities of the system, focus is given to a sample produced following the described protocol and system setup. Results indicate that this system can successfully deposit 11 &#181;m thick yttrium iron garnet films that are &#160;&#62; 90% of the bulk density during a single 5 min deposition run. A discussion of methods to afford better control of the aerosol and particle selection for improved thickness and roughness variations in the film is provided.

This report describes the use of a custom-built system to perform aerosol deposition of thick films of yttrium iron garnet onto sapphire substrates at RT. The deposited films are characterized using scanning electron microscopy, profilometry, and ferromagnetic resonance to give a representative overview of the capabilities of the technique.

Aerosol deposition (AD) is a thick-film deposition process that can produce layers up to several hundred micrometers thick with densities greater than 95% ...

Detection and Recovery of Palladium, Gold and Cobalt Metals from the Urban Mine Using Novel Sensors/Adsorbents Designated with Nanoscale Wagon-wheel-shaped Pores

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in industrialized countries. Here, the development of optical mesosensors/adsorbents (MSAs) for efficient recognition and selective recovery of Pd(II), Au(III), and Co(II) from urban mine was achieved. A simple, general method for preparing MSAs based on using high-order mesoporous monolithic scaffolds was described. Hierarchical cubic Ia3d wagon-wheel-shaped MSAs were fabricated by anchoring chelating agents (colorants) into three-dimensional pores and micrometric particle surfaces of the mesoporous monolithic scaffolds. Findings show, for the first time, evidence of controlled optical recognition of Pd(II), Au(III), and Co(II) ions and a highly selective system for recovery of Pd(II) ions (up to ~95%) in ores and industrial wastes. Furthermore, the controlled assessment processes described herein involve evaluation of intrinsic properties (e.g., visual signal change, long-term stability, adsorption efficiency, extraordinary sensitivity, selectivity, and reusability); thus, expensive, sophisticated instruments are not required. Results show evidence that MSAs will attract worldwide attention as a promising technological means of recovering and recycling palladium, gold and cobalt metals.

Because of the importance and extensive use of palladium, gold and cobalt metals in high-technology equipment, their recovery and recycling constitute an important industrial challenge. The metal recovery system described herein is a simple, low-cost means for the effective detection, removal, and recovery of these metals from the urban mine.

Developing low-cost, efficient processes for recovering and recycling palladium, gold and cobalt metals from urban mine remains a significant challenge in ...

Characterization of Full Set Material Constants and Their Temperature Dependence for Piezoelectric Materials Using Resonant Ultrasound Spectroscopy

During the operation of high power electromechanical devices, a temperature rise is unavoidable due to mechanical and electrical losses, causing the degradation of device performance. In order to evaluate such degradations using computer simulations, full matrix material properties at elevated temperatures are needed as inputs. It is extremely difficult to measure such data for ferroelectric materials due to their strong anisotropic nature and property variation among samples of different geometries. Because the degree of depolarization is boundary condition dependent, data obtained by the IEEE (Institute of Electrical and Electronics Engineers) impedance resonance technique, which requires several samples with drastically different geometries, usually lack self-consistency. The resonant ultrasound spectroscopy (RUS) technique allows the full set material constants to be measured using only one sample, which can eliminate errors caused by sample to sample variation. A detailed RUS procedure is demonstrated here using a lead zirconate titanate (PZT-4) piezoceramic sample. In the example, the complete set of material constants was measured from room temperature to 120 &#176;C. Measured free dielectric constants <img alt="Equation 1" src="/files/ftp_upload/53461/image001.jpg" /> and&#160;<img alt="Equation 2" src="/files/ftp_upload/53461/image002.jpg" /> were compared with calculated ones based on the measured full set data, and piezoelectric constants d15 and d33 were also calculated using different formulas. Excellent agreement was found in the entire range of temperatures, which confirmed the self-consistency of the data set obtained by the RUS.

This protocol describes the procedure of measuring the temperature dependence of the full set material constants of piezoelectric materials using resonant ultrasound spectroscopy (RUS).

During the operation of high power electromechanical devices, a temperature rise is unavoidable due to mechanical and electrical losses, causing the ...

Electrospray Deposition of Uniform Thickness Ge23Sb7S70 and As40S60 Chalcogenide Glass Films

Solution-based electrospray film deposition, which is compatible with continuous, roll-to-roll processing, is applied to chalcogenide glasses. Two chalcogenide compositions are demonstrated: Ge23Sb7S70 and As40S60, which have both been studied extensively for planar mid-infrared (mid-IR) microphotonic devices. In this approach, uniform thickness films are fabricated through the use of computer numerical controlled (CNC) motion. Chalcogenide glass (ChG) is written over the substrate by a single nozzle along a serpentine path. Films were subjected to a series of heat treatments between 100 &#176;C and 200 &#176;C under vacuum to drive off residual solvent and densify the films. Based on transmission Fourier transform infrared (FTIR) spectroscopy and surface roughness measurements, both compositions were found to be suitable for the fabrication of planar devices operating in the mid-IR region. Residual solvent removal was found to be much quicker for the As40S60 film as compared to Ge23Sb7S70. Based on the advantages of electrospray, direct printing of a gradient refractive index (GRIN) mid-IR transparent coating is envisioned, given the difference in refractive index of the two compositions in this study.

Electrospray Deposition of Uniform Thickness Ge23Sb7S70 and As40S60 Chalcogenide Glass Films

A method of uniform thickness solution-derived chalcogenide glass film deposition is demonstrated using computer numerical controlled motion of a single-nozzle electrospray.

Solution-based electrospray film deposition, which is compatible with continuous, roll-to-roll processing, is applied to chalcogenide glasses. Two ...

Characterization of Ultra-fine Grained and Nanocrystalline Materials Using Transmission Kikuchi Diffraction

One of the challenges in microstructure analysis nowadays resides in the reliable and accurate characterization of ultra-fine grained (UFG) and nanocrystalline materials. The traditional techniques associated with scanning electron microscopy (SEM), such as electron backscatter diffraction (EBSD), do not possess the required spatial resolution due to the large interaction volume between the electrons from the beam and the atoms of the material. Transmission electron microscopy (TEM) has the required spatial resolution. However, due to a lack of automation in the analysis system, the rate of data acquisition is slow which limits the area of the specimen that can be characterized. This paper presents a new characterization technique, Transmission Kikuchi Diffraction (TKD), which enables the analysis of the microstructure of UFG and nanocrystalline materials using an SEM equipped with a standard EBSD system. The spatial resolution of this technique can reach 2 nm. This technique can be applied to a large range of materials that would be difficult to analyze using traditional EBSD. After presenting the experimental set up and describing the different steps necessary to realize a TKD analysis, examples of its use on metal alloys and minerals are shown to illustrate the resolution of the technique and its flexibility in term of material to be characterized.

This paper provides a detailed method to characterize the microstructure of ultra-fine grained and nanocrystalline materials using a scanning electron microscope equipped with a standard electron backscatter diffraction system. Metal alloys and minerals presenting refined microstructures are analyzed using this technique, showing the diversity of its possible applications.