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Full-Text Articles in Engineering
Semiempirical Electromagnetic Modeling Of Crack Detection And Sizing In Cement-Based Materials Using Near-Field Microwave Methods, Jagadish Nadakuduti, Genda Chen, R. Zoughi
Semiempirical Electromagnetic Modeling Of Crack Detection And Sizing In Cement-Based Materials Using Near-Field Microwave Methods, Jagadish Nadakuduti, Genda Chen, R. Zoughi
Civil, Architectural and Environmental Engineering Faculty Research & Creative Works
Detection and characterization of cracks in cement-based materials is an integral part of damage evaluation for health monitoring of civil structures. Microwave signals are able to penetrate inside of dielectric materials (e.g., cement-based materials) and are sensitive to local, physical, geometrical, and dielectric variations in a structure. This makes microwave nondestructive testing and evaluation (NDT&E) techniques suitable for inspection and health monitoring of civil structures. Near-field microwave NDT&E techniques offer the added advantage of providing high spatial resolution, requiring simple hardware that may be portable, low power, fast, real time, and robust. Additionally, these techniques are noncontact and one-sided. Besides …
Determination Of Microwave Dielectric Properties Of Materials Using A Unique Application Of Embedded Modulated Scatterer Technique, Gabriel S. Freiburger, R. Zoughi
Determination Of Microwave Dielectric Properties Of Materials Using A Unique Application Of Embedded Modulated Scatterer Technique, Gabriel S. Freiburger, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
The embedded modulated scatterer technique has been investigated in the past as a means of determining the dielectric properties of a material of interest using an open-ended rectangular waveguide and an embedded PIN diode-loaded dipole probe. This technique has been further explored in a unique application utilizing the complex ratio of dynamic reflection coefficients for the two states of the modulated dipole probe. By utilizing this ratio, the calculation of dielectric properties becomes independent of measurement parameters such as distance, orientation, and location of the dipole probe relative to the waveguide radiator. This paper explores this unique application of the …
Determination Of The Thickness And Dielectric Constant Of A Dielectric Slab Backed By Free-Space Or A Conductor Through Inversion Of The Reflection Coefficient Of A Rectangular Waveguide Probe, Jesse Lai, Dana M. Hughes, Eric Gallaher, R. Zoughi
Determination Of The Thickness And Dielectric Constant Of A Dielectric Slab Backed By Free-Space Or A Conductor Through Inversion Of The Reflection Coefficient Of A Rectangular Waveguide Probe, Jesse Lai, Dana M. Hughes, Eric Gallaher, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
Evaluation of thickness and material properties of coatings and dielectric slabs is an important practical issue. Microwave nondestructive testing techniques, using open-ended rectangular waveguide and coaxial probes have shown great potential for this purpose. However, to evaluate one parameter requires that the other be known a priori. This paper discusses the use of a relatively efficient method for evaluating both parameters simultaneously from measurements of the reflection coefficient of a test material. Results of two cases as well as a brief discussion of the limitations of the technique are provided in this paper.
Calculation Of The Impedance Of A Rectangular Waveguide Aperture In The Presence Of A Loaded Dipole Antenna Embedded In A Generally Lossy Material, Dana M. Hughes, R. Zoughi
Calculation Of The Impedance Of A Rectangular Waveguide Aperture In The Presence Of A Loaded Dipole Antenna Embedded In A Generally Lossy Material, Dana M. Hughes, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
The use of a combined embedded modulated scattering technique, utilizing a PIN diode-loaded dipole probe, and near-field microwave nondestructive testing technique, utilizing an open-ended rectangular waveguide, has been investigated as a means for determining the complex dielectric constant in which the MST probe is embedded. For this, the formulation of the forward problem of calculating the modulated reflection coefficient, measured at the aperture of the waveguide, is presented here, This formulation is based upon the reciprocity theorem for two antennae, and utilizes the near-field radiation pattern of a rectangular waveguide aperture and current distribution along the length of a dipole …
Electromagnetic Modeling Of Saltwater Ingress In Mortar At Microwave Frequencies, Shanup Peer, R. Zoughi, K. E. Kurtis
Electromagnetic Modeling Of Saltwater Ingress In Mortar At Microwave Frequencies, Shanup Peer, R. Zoughi, K. E. Kurtis
Electrical and Computer Engineering Faculty Research & Creative Works
Corrosion of reinforcing steel is a major cause of damage and deterioration in reinforced concrete structures. Therefore, as the presence of a sufficient concentration of chloride ions can lead to the onset of corrosion in embedded steel, it is of utmost importance to be able to determine the free salt content and its distribution in these materials. Moreover, it is important to obtain this information nondestructively. Previous investigations have shown the capability of near-field microwave nondestructive evaluation methods, using open-ended rectangular waveguide probes, to evaluate many important properties of cement-based materials. In this Investigation, the temporal microwave reflection properties of …
Comparison Of Water And Saltwater Movement In Mortar Based On A Semi-Empirical Electromagnetic Model, Shanup Peer, R. Zoughi
Comparison Of Water And Saltwater Movement In Mortar Based On A Semi-Empirical Electromagnetic Model, Shanup Peer, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
The presence of chloride ions in steel-reinforced structures leads to the corrosion of the reinforcement thus compromising the integrity and strength of the structure. Thus, it is of great importance to be able to non-destructively detect and evaluate the free chloride content in concrete. To that end, an investigation was initiated where two mortar cubes were soaked in distilled water and saltwater solutions, respectively. Their temporal microwave reflection properties were measured using open-ended rectangular waveguides on a daily basis for three cycles, each lasting 35 days. A semi-empirical electromagnetic model was then developed to simulate the reflection properties of the …
Multimode Solution For The Reflection Properties Of An Open-Ended Rectangular Waveguide Radiating Into A Dielectric Half-Space: The Forward And Inverse Problems, R. Zoughi, Aaron D. Benally, Karl Joseph Bois
Multimode Solution For The Reflection Properties Of An Open-Ended Rectangular Waveguide Radiating Into A Dielectric Half-Space: The Forward And Inverse Problems, R. Zoughi, Aaron D. Benally, Karl Joseph Bois
Electrical and Computer Engineering Faculty Research & Creative Works
Open-ended rectangular waveguides are extensively used in nondestructive dielectric material evaluation. The dielectric properties of an infinite-half space of a material are calculated from the measured reflection properties referenced to the waveguide aperture. This calculation relies on a theoretical and numerical derivation of the reflection coefficient likewise referenced to the waveguide aperture. Most of these derivations assume the dominant mode field distribution across the waveguide aperture. However, when dealing with low permittivity and low loss dielectric materials, there may exist significant errors when calculating the dielectric properties from the measured reflection coefficient. These errors have also shown to be more …
Modeling Of Surface Hairline-Crack Detection In Metals Under Coatings Using An Open-Ended Rectangular Waveguide, Christian J. Huber, Habibollah Abiri, Stoyan I. Ganchev, R. Zoughi
Modeling Of Surface Hairline-Crack Detection In Metals Under Coatings Using An Open-Ended Rectangular Waveguide, Christian J. Huber, Habibollah Abiri, Stoyan I. Ganchev, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
A surface-breaking hairline crack or a narrow slot in a metallic specimen when scanned by an open-ended rectangular waveguide probe influences the reflection-coefficient properties of the incident dominant mode. Subsequent recording of a change in the standing-wave pattern while scanning such a surface results in what is known as the crack characteristic signal. Since microwave signals penetrate inside dielectric materials, this methodology is capable of detecting cracks under dielectric coatings of various electrical thicknesses as well. To electromagnetically model the interaction of an open-ended rectangular waveguide with a surface-breaking hairline crack under a dielectric coating, the dielectric-coating layer is modeled …
Analysis Of The "Crack Characteristic Signal" Using A Generalized Scattering Matrix Representation, Christian J. Huber, Habibollah Abiri, R. Zoughi, Stoyan I. Ganchev
Analysis Of The "Crack Characteristic Signal" Using A Generalized Scattering Matrix Representation, Christian J. Huber, Habibollah Abiri, R. Zoughi, Stoyan I. Ganchev
Electrical and Computer Engineering Faculty Research & Creative Works
Electromagnetic properties of a system formed by an open-ended rectangular waveguide and a surface crack/slot in a metallic specimen are described in this paper. Scanning a crack on a metal surface changes the reflection coefficient of the incident dominant mode. A model as a function of relative crack location within the waveguide aperture (i.e., crack moving with respect to the waveguide aperture) is desired to describe and optimize practical crack detection applications. Hence, the change in the reflection coefficient for a generalized system encompassing empty, filled, and finite cracks located at an arbitrary position inside the waveguide aperture, is evaluated. …
Detecting Stress And Fatigue Cracks, Christian J. Huber, R. Zoughi
Detecting Stress And Fatigue Cracks, Christian J. Huber, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
Discoveries in using open ended rectangular waveguides for microwave surface crack detection and sizing have generated interest. The foundation, potential, advantages and disadvantages of this methodology, developed at the Applied Microwave Nondestructive Testing Laboratory in the Electrical Engineering Department at Colorado State University, are discussed. Microwave techniques in general and this particular approach offer certain unique advantages that can advance the state of the art of fatigue/surface crack detection. The basic features and capabilities of this technique have been theoretically and experimentally investigated these past few years. However, more developmental work is needed to bring this technique from the laboratory …
Microwave Detection Optimization Of Disbond In Layered Dielectrics With Varying Thickness, Stoyan I. Ganchev, Nasser N. Qaddoumi, Emarit Ranu, R. Zoughi
Microwave Detection Optimization Of Disbond In Layered Dielectrics With Varying Thickness, Stoyan I. Ganchev, Nasser N. Qaddoumi, Emarit Ranu, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
The detection sensitivity optimization of air disbond in layered dielectric composites, using an open-ended rectangular waveguide, is studied both theoretically and experimentally. The sensitivity of the disbond detection is strongly influenced by the proper choice of parameters such as the operating frequency and the layered composite geometry (conductor backed or terminated by an infinite half-space of air). The capability of optimizing the measurement system parameters to detect and estimate the thickness of a disbonded layer independent of some changes in the thickness of the dielectric coating is also demonstrated. The impact of the parameters influencing detection optimization is theoretically investigated …
A Novel Microwave Method For Detection Of Long Surface Cracks In Metals, Chin-Yung Yeh, R. Zoughi
A Novel Microwave Method For Detection Of Long Surface Cracks In Metals, Chin-Yung Yeh, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
A novel microwave technique for detecting long surface cracks in metals is described. This technique utilizes an open-ended waveguide to probe the surface of a metal. In the absence of a crack the metal surface is seen as a relatively good short-circuit load. However, in the presence of a crack higher order modes are generated which in turn change the reflection properties at the waveguide aperture. This change brings about a perturbation in the standing wave characteristics which is then probed by a diode detector. The experimental and theoretical foundations of this technique are given, along with several examples. It …
Detection Optimization Of Disbond In Layered Composites With Varying Thicknesses Using An Open-Ended Rectangular Waveguide, Stoyan I. Ganchev, Nasser N. Qaddoumi, R. Zoughi
Detection Optimization Of Disbond In Layered Composites With Varying Thicknesses Using An Open-Ended Rectangular Waveguide, Stoyan I. Ganchev, Nasser N. Qaddoumi, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
The detection of air disbond in layered dielectric composite, which is an important practical issue in many industries, is studied both theoretically and experimentally. Sensitivity of disbond detection depends on certain parameters, like the frequency of operation, the distance between the sensor and the first dielectric layer, and the layered composite geometry (conductor backed or terminated by an infinite half-space of air). The impact of all these parameters is investigated theoretically and then verified experimentally.
Microwave Noncontact Examination Of Disbond And Thickness Variation In Stratified Composite Media, Sasan Bakhtiari, Nasser N. Qaddoumi, Stoyan I. Ganchev, R. Zoughi
Microwave Noncontact Examination Of Disbond And Thickness Variation In Stratified Composite Media, Sasan Bakhtiari, Nasser N. Qaddoumi, Stoyan I. Ganchev, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
Numerical and experimental results of a microwave noncontact, nondestructive detection and evaluation of disbonds and thickness variations in stratified composite media are presented. The aperture admittance characteristics of a flange mounted rectangular waveguide radiating into a layered, generally lossy dielectric media backed or unbacked by a conducting sheet is modeled. The theoretical implementation is based on a Fourier transform boundary matching technique to construct the field components in each medium, coupled with a stationary form of the terminating aperture admittance of the waveguide. The model can serve as a reliable test bed for real-time examination of layered composite media. Experimental …
Open-Ended Rectangular Waveguide For Nondestructive Thickness Measurement And Variation Detection Of Lossy Dielectric Slabs Backed By A Conducting Plate, Sasan Bakhtiari, Stoyan I. Ganchev, R. Zoughi
Open-Ended Rectangular Waveguide For Nondestructive Thickness Measurement And Variation Detection Of Lossy Dielectric Slabs Backed By A Conducting Plate, Sasan Bakhtiari, Stoyan I. Ganchev, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
Solutions of fields inside a slab of a generally lossy dielectric medium backed by a conducting plate, placed outside a waveguide-fed rectangular aperture, are evoked in the application to the microwave nondestructive thickness measurement of such dielectric slabs. Upon construction of the waveguide terminating admittance expression from its variational form, an inverse problem is then solved to extract the slab thickness from the conductance and susceptance in a recursive manner. A comparison between the experimental and theoretical results showed that the significance of higher order modes is minimal; hence, the dominant mode assumption is, in general, valid to describe the …
A Novel Numerical Technique For Dielectric Measurement Of Generally Lossy Dielectrics, Stoyan I. Ganchev, Sasan Bakhtiari, R. Zoughi
A Novel Numerical Technique For Dielectric Measurement Of Generally Lossy Dielectrics, Stoyan I. Ganchev, Sasan Bakhtiari, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
A method for determining the dielectric properties of infinite half-space of generally lossy dielectric materials is described. This method utilizes the measurement of the admittance of a rectangular waveguide radiating into such dielectrics. It is shown that the real part of the admittance is relatively insensitive to the variations of the imaginary part of the dielectric constant. Subsequently, a numerical procedure is initiated which provides a simple and fast-converging approach for calculating the dielectric properties. This numerical procedure lends itself to implementation by personal computers--a major advantage over the existing computational schemes. The theoretical formulation for the expression of the …