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Full-Text Articles in Engineering
Sources Of And Remedies For Removing Unwanted Reflections In Millimeter Wave Images Of Complex Sofi-Covered Space Shuttle Structures, Sergey Kharkovsky, F. L. Hepburn, R. Zoughi
Sources Of And Remedies For Removing Unwanted Reflections In Millimeter Wave Images Of Complex Sofi-Covered Space Shuttle Structures, Sergey Kharkovsky, F. L. Hepburn, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
In the recent years, continuous-wave near-field and lens-focused millimeter wave imaging systems have been effectively used to demonstrate their utility for producing high-resolution images of metallic structures covered with spay on foam insulation (SOFI) such as the Space Shuttle external fuel tank. However, for some specifc structures a certain interference pattern may be superimposed on the produced images. There are methods by which the influence of this unwanted interference can be reduced, such as the incorporation of an incidence angle and the proper use of signal polarization. This paper presents the basics of this problem and describes the use of …
High Resolution Millimeter Wave Inspecting Of The Orbiter Acreage Heat Tiles Of The Space Shuttle, Joseph Toby Case, Sergey Kharkovsky, R. Zoughi, Frank L. Hepburn
High Resolution Millimeter Wave Inspecting Of The Orbiter Acreage Heat Tiles Of The Space Shuttle, Joseph Toby Case, Sergey Kharkovsky, R. Zoughi, Frank L. Hepburn
Electrical and Computer Engineering Faculty Research & Creative Works
The physical cause of Space Shuttle Columbia's catastrophic failure was a breach in its thermal protection system, caused by a piece of external tank insulating foam (SOFI) separating from the external tank and striking the leading edge of the left wing of the orbiter. Consequently, there is an urgent need for a rapid, robust and life-circle oriented nondestructive testing (NDT) technique capable of inspecting the SOFI as well as the orbiter's protective heat tiles and its fuselage prior and subsequent to a launch. Microwave and millimeter wave NDT methods have shown great potential to achieve these goals using real focused …
High Resolution Millimeter Wave Detection Of Vertical Cracks In The Space Shuttle External Tank Spray-On-Foam Insulation (Sofi), Sergey Kharkovsky, R. Zoughi, F. L. Hepburn
High Resolution Millimeter Wave Detection Of Vertical Cracks In The Space Shuttle External Tank Spray-On-Foam Insulation (Sofi), Sergey Kharkovsky, R. Zoughi, F. L. Hepburn
Electrical and Computer Engineering Faculty Research & Creative Works
Space Shuttle Columbia's catastrophic failure, the separation of a piece of spray-on-foam insulation (SOFI) from the external tank (ET) in the Space Shuttle Discovery's flight in 2005 and crack detected in its ET foam prior to its successful launch in 2006 emphasize the need for effective nondestructive methods for inspecting the shuttle ET SOFI. Millimeter wave nondestructive testing methods have been considered as potential and effective inspection tools for evaluating the integrity of the SOFI. This paper presents recent results of an investigation for the purpose of detecting vertical cracks in SOFI panels using a focused millimeter wave (150 GHz) …
Microwave Quantitative Nde Technique For Dielectric Slab Thickness Estimation Using The Music Algorithm, Mohamed A. Abou-Khousa, R. Zoughi
Microwave Quantitative Nde Technique For Dielectric Slab Thickness Estimation Using The Music Algorithm, Mohamed A. Abou-Khousa, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
Non-invasive monitoring of dielectric slab thickness is of great interest in various industrial applications. This paper focuses on estimating the thickness of dielectric slabs, and consequently monitoring their variations, utilizing wideband microwave signals and the MUtiple SIgnal Characterization (MUSIC) algorithm. The performance of the proposed approach is assessed by validating simulation results with laboratory experiments. The results clearly indicate the utility of this overall approach for accurate dielectric slab thickness evaluation.
Millimeter-Wave Detection Of Localized Anomalies In The Space Shuttle External Fuel Tank Insulating Foam, Sergey Kharkovsky, R. Zoughi, J. T. Case, Mohamed A. Abou-Khousa, F. L. Hepburn
Millimeter-Wave Detection Of Localized Anomalies In The Space Shuttle External Fuel Tank Insulating Foam, Sergey Kharkovsky, R. Zoughi, J. T. Case, Mohamed A. Abou-Khousa, F. L. Hepburn
Electrical and Computer Engineering Faculty Research & Creative Works
The Space Shuttle Columbia's catastrophic accident emphasizes the growing need for developing and applying effective, robust, and life-cycle-oriented nondestructive testing (NDT) methods for inspecting the shuttle external fuel tank spray on foam insulation (SOFI). Millimeter-wave NDT techniques were one of the methods chosen for evaluating their potential for inspecting these structures. Several panels with embedded anomalies (mainly voids) were produced and tested for this purpose. Near-field and far-field millimeter-wave NDT methods were used for producing images of the anomalies in these panels. This paper presents the results of an investigation for the purpose of detecting localized anomalies in several SOFI …
Inspection Of Spray On Foam Insulation (Sofi) Using Microwave And Millimeter Wave Synthetic Aperture Focusing And Holography, Joseph Toby Case, Frank L. Hepburn, R. Zoughi
Inspection Of Spray On Foam Insulation (Sofi) Using Microwave And Millimeter Wave Synthetic Aperture Focusing And Holography, Joseph Toby Case, Frank L. Hepburn, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
The Space Shuttle Columbia's catastrophic failure is thought to have been caused by a dislodged piece of external tank spray on foam insulation (SOFI) striking and significantly damaging the left wing of the orbiter, which may have been due to a flawed section of SOFI. Microwave and millimeter wave nondestructive evaluation (NDE) methods have shown great potential detecting anomalies in SOFI such as small air voids using a horn and lens in a (real) focused configuration. Synthetic focusing methods may also be used to detect air voids in SOFI and may additionally offer the ability to locate the defect in …
Millimeter Wave Imaging Of Corrosion Under Paint: Comparison Of Two Probes, Mohammad Tayeb Ahmad Ghasr, Sergey Kharkovsky, R. Zoughi, Matthew O'Keefe, Ajay Padwal, Donald D. Palmer
Millimeter Wave Imaging Of Corrosion Under Paint: Comparison Of Two Probes, Mohammad Tayeb Ahmad Ghasr, Sergey Kharkovsky, R. Zoughi, Matthew O'Keefe, Ajay Padwal, Donald D. Palmer
Electrical and Computer Engineering Faculty Research & Creative Works
Critical aircraft structures are susceptible to harsh environmental conditions that cause corrosion of these structural components. It is of great importance to detect corrosion under paint, particularly in its early stages. Millimeter wave nondestructive evaluation methods have shown great potential for detecting corrosion under paint and evaluating its properties. This paper presents and compares the results of using two distinct millimeter wave detection methods; namely a standard single probe and a newly developed differential probe for detecting corrosion under paint.
A Novel Method For Determination Of Dielectric Properties Of Materials Using A Combined Embedded Modulated Scattering And Near-Field Microwave Techniques-Part I: Forward Model, Dana M. Hughes, R. Zoughi
A Novel Method For Determination Of Dielectric Properties Of Materials Using A Combined Embedded Modulated Scattering And Near-Field Microwave Techniques-Part I: Forward Model, Dana M. Hughes, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
The use of combined embedded modulated scattering technique and near-field microwave nondestructive testing techniques is investigated as a novel method for evaluating the dielectric properties of a material. The forward formulation for determining the reflection coefficient at the aperture of a waveguide radiating into a dielectric half-space in which a PIN diode-loaded dipole (i.e., modulated scattering technique probe) is embedded is presented. This formulation is based upon calculating the near-field coupling between the waveguide and the dipole as a mutual impedance.
A Novel Method For Determination Of Dielectric Properties Of Materials Using A Combined Embedded Modulated Scattering And Near-Field Microwave Techniques-Part Ii: Dielectric Property Recalculation, R. Zoughi, Dana Hughes
A Novel Method For Determination Of Dielectric Properties Of Materials Using A Combined Embedded Modulated Scattering And Near-Field Microwave Techniques-Part Ii: Dielectric Property Recalculation, R. Zoughi, Dana Hughes
Electrical and Computer Engineering Faculty Research & Creative Works
The use of combined embedded modulated scattering technique and near-field microwave nondestructive testing techniques is investigated as a novel method for evaluating the dielectric properties of a material. The forward formulation for determining the reflection coefficient at the aperture of a waveguide radiating into a dielectric half-space in which a PIN diode-loaded dipole (i.e., modulated scattering technique probe) is embedded was presented in Part I of this paper. Here, in Part II, the recalculation of the dielectric properties, using the results of the forward model, is presented along with some associated experimental results.
Evaluation Of Microwave Reflection Properties Of Cyclically Soaked Mortar Based On A Semiempirical Electromagnetic Model, Shanup Peer, K. E. Kurtis, R. Zoughi
Evaluation Of Microwave Reflection Properties Of Cyclically Soaked Mortar Based On A Semiempirical Electromagnetic Model, Shanup Peer, K. E. Kurtis, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
Detection of chloride ingress and evaluation of its distribution and temporal movement in reinforced concrete structures is an important practical issue. Steel reinforcing bars embedded in good quality concrete are normally protected from corrosion. However, the presence of a sufficient concentration of free chloride ions in the region of the reinforcing steel can initiate the process of corrosion. Therefore, it is important to be able to detect ingress of chloride ions and their distribution in cement-based materials. Moreover, it is important to obtain this information nondestructively. In recent years, near-field microwave nondestructive evaluation methods, using open-ended rectangular waveguide probes, have …
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 …
Microwave And Millimeter Wave Imaging Of The Space Shuttle External Fuel Tank Spray On Foam Insulation (Sofi) Using Synthetic Aperture Focusing Techniques (Saft), Joseph Toby Case, J. Robbins, Sergey Kharkovsky, Frank L. Hepburn, R. Zoughi
Microwave And Millimeter Wave Imaging Of The Space Shuttle External Fuel Tank Spray On Foam Insulation (Sofi) Using Synthetic Aperture Focusing Techniques (Saft), Joseph Toby Case, J. Robbins, Sergey Kharkovsky, Frank L. Hepburn, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
The Space Shuttle Columbia's catastrophic failure is thought to have been caused by a dislodged piece of external tank spray on foam insulation (SOFI) striking the left wing of the orbiter causing significant damage to some of the reinforced carbon/carbon leading edge wing panels. Microwave and millimeter wave nondestructive evaluation methods have shown great potential for inspecting SOFI for the purpose of detecting anomalies such as small air voids that may cause separation of the SOFI from the external tank during a launch. These methods are capable of producing relatively high-resolution images of the interior of SOFI particularly when advanced …
Microwave And Millimeter Wave Testing For The Inspection Of The Space Shuttle Spray On Foam Insulation (Sofi) And The Acreage Heat Tiles, R. Zoughi, Sergey Kharkovsky, Frank L. Hepburn
Microwave And Millimeter Wave Testing For The Inspection Of The Space Shuttle Spray On Foam Insulation (Sofi) And The Acreage Heat Tiles, R. Zoughi, Sergey Kharkovsky, Frank L. Hepburn
Electrical and Computer Engineering Faculty Research & Creative Works
The utility of microwave and millimeter wave nondestructive testing and evaluation (NDT&E) methods, for testing the Space Shuttle's external fuel tank spray on foam insulation (SOFI) and the acreage heat tiles has been investigated during the past two years. Millimeter wave NDE techniques are capable of producing internal images of SOFI. This paper presents the results of testing several diverse panels with embedded voids and debonds at millimeter wave frequencies. Additionally, the results of testing a set of heat tiles are also presented. Finally, the attributes of these methods as well as the advantageous features associated with these systems are …
Dielectric Material Characterization By Complex Ratio Of Embedded Modulated Scatterer Technique States, Gabriel S. Freiburger, R. Zoughi
Dielectric Material Characterization By Complex Ratio Of Embedded Modulated Scatterer Technique States, Gabriel S. Freiburger, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
The embedded modulated scatterer technique (MST) is an innovative tool which can be used for microwave dielectric characterization of infrastructure and composite structures. By impinging a microwave signal on a loaded thin dipole antenna embedded in a material whose dielectric properties are sought, the resulting refelction data can be used to inversely solve for the dielectric properties of interest. Previous investigations utilized reflection information from a single loaded dipole and required known system parameters, such as radiator polarization vs. dipole alignment and relative distance between radiator and probe, to solve for the sought-for dielectric properties. This paper explores a unique …
High-Temperature Monitoring Of Refractory Wall Recession Using Frequency-Modulated Continuous-Wave (Fm-Cw) Radar Techniques, Bivin Varghese, C. Deconick, G. Cartee, M. Velez, Robert E. Moore, R. Zoughi
High-Temperature Monitoring Of Refractory Wall Recession Using Frequency-Modulated Continuous-Wave (Fm-Cw) Radar Techniques, Bivin Varghese, C. Deconick, G. Cartee, M. Velez, Robert E. Moore, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
Furnaces are among the most crucial components in the glass and metallurgical industry. Nowadays, furnaces are being operated at higher temperatures and for longer periods of time thus increasing the rate of wear on the furnace refractory lining. Consequently, there is a great need for a nondestructive tool that can accurately measure refractory wall thickness at high temperatures. In this paper the utility of a frequency-modulated continuous-wave (FM-CW) radar is investigated for this purpose.
Millimeter Wave Detection Of Localized Anomalies In The Space Shuttle External Fuel Tank Insulating Foam And Acreage Heat Tiles, Sergey Kharkovsky, R. Zoughi, J. T. Case, F. L. Hepburn
Millimeter Wave Detection Of Localized Anomalies In The Space Shuttle External Fuel Tank Insulating Foam And Acreage Heat Tiles, Sergey Kharkovsky, R. Zoughi, J. T. Case, F. L. Hepburn
Electrical and Computer Engineering Faculty Research & Creative Works
Undesired manufactured or in-service produced anomalies in the form of voids in the SOFI and unbonds in the heat tiles can significantly reduce their designed effectiveness. Additionally, unbonds in the heat tiles may cause their complete separation from the fuselage exposing it to extreme heat. Millimeter wave NDT methods are viable candidate for life-cycle inspection of the SOFI and the acreage heat tiles of the Space Shuttle fleet. The results of these investigations described in this paper clearly showed the utility of these methods for detecting localized anomalies in thick SOFI and acreage heat tiles. These methods are fast and …
Size Evaluation Of Corrosion Precursor Pitting Using Near-Field Millimeter Wave Nondestructive Testing Methods, Mohammad Tayeb Ahmad Ghasr, Brian D. Carroll, Sergey Kharkovsky, R. Zoughi, R. Austin
Size Evaluation Of Corrosion Precursor Pitting Using Near-Field Millimeter Wave Nondestructive Testing Methods, Mohammad Tayeb Ahmad Ghasr, Brian D. Carroll, Sergey Kharkovsky, R. Zoughi, R. Austin
Electrical and Computer Engineering Faculty Research & Creative Works
Early detection of corrosion precursor pitting and estimation of its overall dimensions directly affects the required effort and cost associated with repair and maintenance of critical aircraft structural components. The magnitude and phase of a reflected signal from a pitting are directly related to its dimensions. This paper presents a millimeter wave probe and a sizing procedure used to detect and evaluate overall pitting dimensions.
Comparison Of Water And Saltwater Movement In Mortar Based On A Semiempirical Electromagnetic Model, Shanup Peer, R. Zoughi
Comparison Of Water And Saltwater Movement In Mortar Based On A Semiempirical 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 interest to nondestructively detect and evaluate free chloride content in concrete. To this 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. Subsequently, a semiempirical electromagnetic model was developed to simulate the reflection properties of the cubes. The outcome of …
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.
An Electromagnetic Model For Evaluating Temporal Water Content Distribution And Movement In Cyclically Soaked Mortar, Shanup Peer, K. E. Kurtis, R. Zoughi
An Electromagnetic Model For Evaluating Temporal Water Content Distribution And Movement In Cyclically Soaked Mortar, Shanup Peer, K. E. Kurtis, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
Evaluation of water distribution and its temporal movement in cement-based materials is important for assessing cement hydration, curing, and long-term performance. From a practical standpoint, it is also important to obtain this information nondestructively. Near-field microwave nondestructive evaluation methods have proven effective for evaluation of cement-based materials for their various mixture properties, including the detection of salt added to the mixing water and chloride ions entering these materials through exposure to salt water solutions. Electromagnetic modeling of the interaction of microwave signals with moist cement-based materials can provide the necessary insight to evaluate water content distribution and movement in these …
Microwave Reflection And Dielectric Properties Of Mortar Subjected To Compression Force And Cyclically Exposed To Water And Sodium Chloride Solution, Shanup Peer, Joseph Toby Case, Eric Gallaher, K. E. Kurtis, R. Zoughi
Microwave Reflection And Dielectric Properties Of Mortar Subjected To Compression Force And Cyclically Exposed To Water And Sodium Chloride Solution, Shanup Peer, Joseph Toby Case, Eric Gallaher, K. E. Kurtis, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
Corrosion of the reinforcing steel is a major cause of damage and deterioration in reinforced concrete structures such as concrete bridge decks and columns. Chloride intrusion into concrete can lead to depassivation of the steel and initiation of corrosion. Thus, it is very important to be able to nondestructively detect and evaluate the free chloride content in concrete. Near-field microwave nondestructive testing techniques, using open-ended rectangular waveguide probes, have shown great potential for evaluating various properties of concrete, including the successful detection of sodium chloride added to mortar mixing water. In this study, several mortar samples are cyclically soaked in …
Near-Field Microwave Non-Invasive Determination Of Nacl In Mortar, Karl Joseph Bois, Aaron D. Benally, R. Zoughi
Near-Field Microwave Non-Invasive Determination Of Nacl In Mortar, Karl Joseph Bois, Aaron D. Benally, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
In recent years near-field microwave nondestructive testing and evaluation techniques have shown great promise for evaluating different properties of cement-based structures. An important issue regarding the inspection of these structures is the ability to determine the presence and evaluate the content of chloride in them. Chlorides can be introduced in these structures in many different ways including when salts are present in their mixing water. Consequently, for this investigation, two sets of 8" × 8" × 8" (203mm) cubic mortar specimens were prepared each with a water-to-cement (w/c) ratio of 0.5 and 0.6, respectively, and both sets with sand-to-cement ratios …
A Method For Evaluating The Dielectric Properties Of Composites Using A Combined Embedded Modulated Scattering And Near-Field Microwave Nondestructive Testing Technique, Dana M. Hughes, R. Zoughi
A Method For Evaluating The Dielectric Properties Of Composites Using A Combined Embedded Modulated Scattering And Near-Field Microwave Nondestructive Testing Technique, Dana M. Hughes, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
Investigation into the derivation of the dielectric property of a material with an embedded modulated PIN diode-loaded dipole is described, using an open-ended rectangular waveguide as the irradiating source. Previous measurements of the curing of a mortar specimen show the sensitivity of this combined technique and its potential for inspecting composite structures. Modification of previous algorithms for back calculating the dielectric properties of a material with a conductor backing is considered. The modification would involve replacing the reflection at the conductor with the reflection at a modulated dipole antenna. For this, comparisons between the reflection coefficients of the dipole antenna …
Whispering Gallery Mode Dielectric Resonators For The Millimeter Wave Near Field Sensing Applications, Sergey Kharkovsky, Yu Prokopenko, M. F. Akay
Whispering Gallery Mode Dielectric Resonators For The Millimeter Wave Near Field Sensing Applications, Sergey Kharkovsky, Yu Prokopenko, M. F. Akay
Electrical and Computer Engineering Faculty Research & Creative Works
The resonance characteristics of whispering gallery modes (WGMs) in parallel-plate type cylindrical dielectric resonators (DRs) are numerically considered to optimise their characteristics for sensing applications. Results for the dependency of the resonant frequency, Q-factor, slow-down factor and electric energy filling factor of the modes on resonator parameters for both isotropic and anisotropic DR are presented. The possible applications of the results for millimeter wave near field nondestructive measurements are discussed.
Cure-State Monitoring And Water-To-Cement Ratio Determination Of Fresh Portland Cement-Based Materials Using Near-Field Microwave Techniques, Karl Joseph Bois, Aaron D. Benally, Paul S. Nowak, R. Zoughi
Cure-State Monitoring And Water-To-Cement Ratio Determination Of Fresh Portland Cement-Based Materials Using Near-Field Microwave Techniques, Karl Joseph Bois, Aaron D. Benally, Paul S. Nowak, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
Quick and nondestructive determination of curestate and water-to-cement (w/c) ratio in fresh Portland cementbased materials is an important issue in the construction industry since the compressive strength of these materials is significantly influenced by w/c ratio. This is especially true since current techniques are not reliable and require a priori testing of test specimens as calibration for subsequent on-site monitoring of a cast in-place structure. Recently, the sensing of Portland cementbased materials using microwave techniques has received much attention. Microwave nondestructive techniques have already shown the potential for determining w/c ratio, sand-to-cement (s/c) ratio and coarse aggregate-to-cement (ca/c) ratio in …
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 …
Measurement Parameter Optimization For Surface Crack Detection In Metals Using An Open-Ended Waveguide Probe, R. Zoughi, Stoyan I. Ganchev, Christian J. Huber
Measurement Parameter Optimization For Surface Crack Detection In Metals Using An Open-Ended Waveguide Probe, R. Zoughi, Stoyan I. Ganchev, Christian J. Huber
Electrical and Computer Engineering Faculty Research & Creative Works
Fatigue and stress induced surface crack detection in metals is an important practical issue. A newly developed microwave inspection approach, using an open-ended rectangular waveguide, has proved to be an effective tool for detecting such cracks. This novel microwave approach overcomes some of the limitations associated with the standard detection methods for surface crack detection. In addition, this approach is applicable to exposed, filled (with a dielectric such as dirt, rust, etc.) and cracks under dielectric coatings such as paint. This paper presents the basic foundation of this surface crack detection methodology along with the ways by which measurement parameters …
Calibration And Measurement Of Dielectric Properties Of Finite Thickness Composite Sheets With Open-Ended Coaxial Sensors, Stoyan I. Ganchev, Nasser N. Qaddoumi, Sasan Bakhtiari, R. Zoughi
Calibration And Measurement Of Dielectric Properties Of Finite Thickness Composite Sheets With Open-Ended Coaxial Sensors, Stoyan I. Ganchev, Nasser N. Qaddoumi, Sasan Bakhtiari, R. Zoughi
Electrical and Computer Engineering Faculty Research & Creative Works
The application of open-ended coaxial sensors for dielectric measurement of finite thickness composite sheets is studied. Expressions for calculation of the complex aperture admittance for two geometries are presented. These expressions are used to calculate the dielectric constant of infinite half-space as well as finite thickness slabs. A more efficient method of such calculations, using a personal computer, for low to medium loss dielectrics is demonstrated. The question of when a dielectric layer may be considered as infinitely thick is also addressed, and examples are presented. A different calibration technique (compared to the conventional ones) is described and successfully implemented. …
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.