Engineering Commons^™

Nondestructive Evaluation Of Structural Defects In Concrete Slabs, Ehsanul Kabir

Electronic Theses and Dissertations

Nondestructive testing (NDT) is a reliable method for determining the structural integrity of new and old construction and understanding the condition of structural defects. It is widely acknowledged that the interpretation of nondestructive evaluation (NDE) has a significant impact on the reliability and consistency of this technology. However, NDT data acquisition remains subjective and heavily dependent on the operator’s knowledge and expertise. As a result, there are still issues to be resolved regarding the imaging and diagnostic procedures for NDT-based concrete inspection. NDT methods such as ground penetrating radar (GPR), and impact-echo (IE), have been extensively used to inspect concrete …

Electrical Capacitance Measurements To Assess European Corn Borer Infestation In Maize, Mavrik D. Thomas

Theses and Dissertations

The European Corn Borer (ECB), Ostrinia nubilalis, is an agricultural pest which bores small holes in the rind of maize stalks and then proceeds to consume the pith. Because most of the damage to the stalk is internal, it is difficult to quantify the damage to an individual stalk without time-consuming, manual examination. This work explored the hypothesis that internal damage could be detected and quantified using non-destructive, electromagnetic measurements. Laboratory experiments and numerical simulation studies predicted changes in capacitance of stalks due to hollow core ECB damage. A guarded probe device to measure electrical impedance from 500 Hz to …

Dynamic Testing: An Experimental Approach To Defect Identification In Additive Manufactured Parts, Aimee Allen

Dissertations, Master's Theses and Master's Reports

Today’s additive manufacturing (AM) industry produces specialized parts at low volume or with complex geometries. Traditional testing methods are effective, but costly and time consuming to perform. The AM industry lacks an optimized testing method for identifying internal defects that occur in parts. The evaluation of multiple parts printed on the same build plate for internal defects using various nondestructive (dynamic) testing techniques is presented. From these experiments, perspective was gained on when and how dynamic testing can be used to find defects. Insight gained from these experiments can help the industry in future testing for internal defects.

Prediction Of The Compressive Strength And Dynamic Modulus Of Fiber Reinforced Concrete By Ultrasonic Pulse Velocity Measurement At Early Ages, Daniel A. Castillo Pereira

Electronic Theses and Dissertations

This research investigates the relationship between early age ultrasonic pulse velocity and the compressive strength and dynamic modulus of steel, polypropylene, nylon, and glass fiber reinforced concrete. Previous studies prove that adding fibers to concrete alters the propagation of ultrasonic pulse velocity waves. Therefore, each type of fiber-reinforced concrete will have a unique relationship between ultrasonic pulse velocity and its compressive strength and dynamic modulus depending on fiber type, fiber volume fraction, water to cement ratio, and test age. To test this hypothesis, an experimental program comprising of one hundred eighty-nine 100 mm x 200 mm fiber reinforced concrete cylinders …

Evaluation Of Low And High Frequency Dynamic Response For Condition Assessment Of Reinforced Concrete Structures, Ali Hafiz

Dissertations and Theses

Concrete is widely used for civil infrastructure structures and they experience deterioration and degradation due to aging, increases in the traffic loads, harsher environmental conditions, use of deicing chemicals, etc. Therefore, evaluating the integrity of reinforced concrete structures has become of increasing interest for infrastructure owners and managers. A number of non-destructive testing (NDT) and structural health monitoring (SHM) methods have been developed in recent decades to aid in evaluating structures and provide input for asset management. One family of these methods uses the dynamic response of a structural member: stress waves (high frequency) and structural vibrations (low frequency). Both …

Physics-Based Signal Processing Methods For Terahertz Non-Destructive Evaluation Of Layered Media, Scott G. Schecklman

Dissertations and Theses

In recent years Terahertz (THz) time domain spectroscopy has emerged as a promising new technology with potential applications in a variety of fields, including industrial manufacturing, security screening and medical imaging. Pulsed THz systems are uniquely suited for non-destructive evaluation (NDE) of the sub-surface layers of dielectric packaging and coating materials, because they provide high dynamic range over a wide bandwidth in the far infrared portion of the electromagnetic spectrum. Often the dielectric materials of the packaging and/or surface coating layers exhibit relatively low loss and abrupt changes in the refractive index at the layer boundaries can be observed as …

Passively-Coded Embedded Microwave Sensors For Materials Characterization And Structural Health Monitoring (Shm), Katelyn Rose Brinker

Masters Theses

"Monitoring and maintaining civil, space, and aerospace infrastructure is an ongoing critical problem facing our nation. As new complex materials and structures, such as multilayer composites and inflatable habitats, become ubiquitous, performing inspection of their structural integrity becomes even more challenging. Thus, novel nondestructive testing (NDT) methods are needed. Chipless RFID is a relatively new technology that has the potential to address these needs. Chipless RFID tags have the advantage of being wireless and passive, meaning that they do not require a power source or an electronic chip. They can also be used in a variety of sensing applications including …

Hardware Architectures For Compact Microwave And Millimeter Wave Cameras, Matthew Jared Horst

Doctoral Dissertations

"Millimeter wave SAR imaging has shown promise as an inspection tool for human skin for characterizing burns and skin cancers. However, the current state-of-the-art in microwave camera technology is not yet suited for developing a millimeter wave camera for human skin inspection. Consequently, the objective of this dissertation has been to build the necessary foundation of research to achieve such a millimeter wave camera. First, frequency uncertainty in signals generated by a practical microwave source, which is prone to drift in output frequency, was studied to determine its effect on SAR-generated images. A direct relationship was found between the level …

Development Of Active Microwave Thermography For Structural Health Monitoring, Ali Foudazi

Doctoral Dissertations

"Active Microwave Thermography (AMT) is an integrated nondestructive testing and evaluation (NDT&E) method that incorporates aspects of microwave NDT and thermography techniques. AMT uses a microwave excitation to generate heat and the surface thermal profile of the material or structure under test is subsequently measured using a thermal camera (or IR camera). Utilizing a microwave heat excitation provides advantages over traditional thermal excitations (heat lamps, etc.) including the potential for non-contact, selective and focused heating. During an AMT inspection, two heating mechanisms are possible, referred to as dielectric and induction heating. Dielectric heating occurs as a result of the interaction …

Physics-Based Imaging Methods For Terahertz Nondestructive Evaluation Applications, Gabriel Paul Kniffin

Dissertations and Theses

Lying between the microwave and far infrared (IR) regions, the "terahertz gap" is a relatively unexplored frequency band in the electromagnetic spectrum that exhibits a unique combination of properties from its neighbors. Like in IR, many materials have characteristic absorption spectra in the terahertz (THz) band, facilitating the spectroscopic "fingerprinting" of compounds such as drugs and explosives. In addition, non-polar dielectric materials such as clothing, paper, and plastic are transparent to THz, just as they are to microwaves and millimeter waves. These factors, combined with sub-millimeter wavelengths and non-ionizing energy levels, makes sensing in the THz band uniquely suited for …

Surface Roughness Of Electron Beam Melting Ti-6al-4v Effect On Ultrasonic Testing, Evan T. Hanks

Theses and Dissertations

Experimental research was conducted on the effects of surface roughness on ultrasonic non-destructive testing of Electron Beam Melted (EBM) additively manufactured Ti-6Al-4V. Additive Manufacturing (AM) is a developing technology with many potential benefits, but certain challenges posed by its use require further research before AM parts are viable for widespread use in the aviation industry. Possible applications of this new technology include, Aircraft Battle Damage Repair (ABDR), small batch manufacturing to fill supply gaps, and replacement for obsolete parts. The research presented here assesses the effectiveness of ultrasonic inspection in detecting manufactured flaws in EBM manufactured Ti-6Al-4V. EBM products are …

Field Observation Of Installation And Performance Of Repair Materials, Larisa Diana Susinskas

ETD Archive

The state of Ohio is in a region that commonly experiences drastic changes in weather. States with similar climates are susceptible to pavement cracking and failures due to the frequent or extreme freeze-thaw cycles. Freeze-thaw cycles, paired with de-icing chemicals that are frequently placed on roadways during the winter months will most likely lead to pavement cracks and failure. Ohio Department of Transportation (ODOT) routinely repairs and replaces sections of concrete roadways and bridge decks. Therefore, ODOT is seeking durable, cost-effective materials to repair smaller pavement failures.

The purpose of this study is to determine which high performance repair materials …

Test And Evaluation Of Ultrasonic Additive Manufacturing (Uam) For A Large Aircraft Maintenance Shelter (Lams) Baseplate, Daniel H. Gartland

Theses and Dissertations

Additive manufacturing is an exciting new manufacturing technology that could have application to Air Force Civil Engineer (CE) operations. This research replicates a Large Area Maintenance Shelter (LAMS) baseplate design for ultrasonic additive manufacturing (UAM). Due to production problems the test section was not built as designed. Instead, a smaller block of material was submitted for evaluation. After the UAM build, ultrasonic inspection was conducted to identify anomalies in the test piece. The results of this proof of concept study indicate that UAM is not yet ready for CE expeditionary applications requiring a high degree of mechanical strength. The machine …

Advanced Approaches For Bridge Deck Assessment Using Ground Penetrating Radar, Aleksey Kamilevich Khamzin

Doctoral Dissertations

"Ground penetrating radar (GPR) data were acquired across four bridge decks with the objective of developing an advanced workflow for GPR operation that would allow the bridge owners to estimate repair quantities for certain bridge decks, based on GPR data. The primary contributions from this research are as follows: 1. It was demonstrated that the conditions of bridge decks can be cost-effectively and efficiently assessed using the GPR tool. 2. The GPR tool's ability to provide rapid and reliable results in comparison with conventional bridge deck condition assessment techniques was established. 3. The qualitative and quantitative relationships between the GPR …

Optimization Of Stress Wave-Based Nondestructive Methods In Identifying Deterioration In Concrete Structures, Hoda Azari

Open Access Theses & Dissertations

The transportation infrastructure across the United States is deteriorating and requires periodic inspection to predict the cost of repair and extent of maintenance activities, to remedy structural problems, and to ensure safety and serviceability. The use of nondestructive testing (NDT) methods in detecting and characterizing flaws in the infrastructure has become more common. Among different NDT methods, the stress wave-based methods, including ultrasonic surface waves (USW) and impact echo (IE) methods, are widely used to maintain concrete structures. In this dissertation, a complete literature review of seismic wave theory and wave propagation in plate like structures, and stress wave-based methods …

A High Bandwidth Non-Destructive Method For Characterizing Simple Media, Matthew L. Szuster

Theses and Dissertations

The relative complex permittivity can be extracted with time domain data from a perfect electrical conductor (PEC) backed sample of a low-loss, non-dispersive dielectric using dual ridged waveguide aperture probes with attached PEC flange plates of the same geometry and different dimensions. The temporal domain measurement of interest is the ability to detect the reflection from the edge of the flange plate in the parallel region created by the flange plate and the PEC backing on the dielectric sample. Signal processing windows are applied to the data in order to exploit this edge reflection. The types of signal processing methods …

An Enhanced Fuselage Ultrasound Inspection Approach For Ishm Purposes, Francisco Ospina

Theses and Dissertations

This effort constitutes a systems engineering approach in which the materials science, ultrasound structural health monitoring, flight and maintenance operations, and relevant aeronautical policies and programs are involved to explore the evolution and characterization of structural cracks in aircraft fuselage structures in which the loads are varying. During flight, an aircraft fuselage skin and structure are subjected to varied cyclic loads, which can cause embedded cracks and other damage features to change their characteristics due to loading effects. The current research is based in the application of finite element modeling techniques using COMSOL and PZFLEX software to characterize the behavior …

Document Flash Thermography, Cory A. Larsen

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This thesis presents the application of ash thermography techniques to the analysis of documents. The motivation for this research is to develop the ability to non-destructively reveal covered writings in archaeological artifacts such as the Codex Selden or Egyptian car- tonnage. Current common signal processing techniques are evaluated for their effectiveness in enhancing subsurface writings found within a set of test documents. These processing techniques include: false colorization, contrast stretching, histogram equalization, median altering, Gaussian low-pass altering, layered signal reconstruction and thermal signal reconstruction (TSR), several contrast image definitions, differential absolute contrast (DAC), correlated contrast, derivative images, principal component thermography …

Evaluation Of Nondestructive Technologies To Assess Presence And Extent Of Delamination Of Hot Mix Asphalt Airfield Pavements, Manuel Celaya

Open Access Theses & Dissertations

Sufficient bonding between the hot mix asphalt layers is essential to ensure the desired structural capacity of a pavement. Delamination or debonding problems are particularly more severe on airfield pavements, due to higher traffic loads applied by aircrafts. Further progression of delamination may result in stripping of the lower layers due to the intrusion of moisture or may develop other dangerous distresses such as foreign object debris. The existing nondestructive testing procedures and equipment that have the potential to address the problem were identified and their effectiveness and potential for success were evaluated. The Ground Penetrating Radar, Falling Weight Deflectometer, …

Changes In Structural Health Monitoring System Capability Due To Aircraft Environmental Factors, Jeffrey D. Kuhn

Theses and Dissertations

Structural Health Monitoring (SHM) promises to decrease the maintenance cost and increase the availability of aging aircraft fleets by fundamentally changing the way structural inspections are performed. But this promise can only be realized through the consistent and predictable performance of a SHM system throughout the entire remaining life of an aircraft. In a sensor-based SHM system, sensor signal changes are analyzed and interpreted to identify structural flaws. But aircraft environmental factors such as temperature fluctuations, cyclic strain and exposure to various aircraft fluids also have the potential to change SHM sensor signals, raising questions about long term SHM system …

Inverse Scattering Image Quality With Noisy Forward Data, Thomas J. Sorensen

Theses and Dissertations

Image quality metrics for several inverse scattering methods and algorithms are presented. Analytical estimates and numerical simulations provide a basis for poor image quality diagnostics. The limitations and noise behavior of reconstructed images are explored analytically and empirically using a contrast ratio. Theoretical contrast ratio estimates using the canonical PEC circular cylinder are derived. Empirical studies are conducted to confirm theoretical estimates and to provide examples of image quality vs SNR for more complex scatterer profiles. Regularized sampling is shown to be more noise sensitive than tomographic reconstructive methods.

Development Of An Ultrasonic Nde&T Tool For Yield Detection In Steel Structures, Yilmaz Bingol

LSU Doctoral Dissertations

Nondestructive Evaluation and Testing (NDE&T) is a commonly used and rapidly growing field that offers successful solutions for health assessment of structures. NDE&T methods have gained increasing attention in the last few decades especially with the contribution of the advancements in computer and instrumentation technologies. The applications of numerous NDE&T methods in civil engineering mostly focus on material characterization and defect detection. Techniques for nondestructively identifying the stress state in materials, on the other hand, mostly rely on the Theory of Acoustoelasticity. However, the sensitivity and the accuracy of acoustoelasticity are affected by several factors such as the microstructure of …

Finite Element Analysis Of Lamb Waves Acting Within A Thin Aluminum Plate, Sejin Han

Theses and Dissertations

Structural health monitoring (SHM) is an emerging technology that can be used to identify, locate and quantify structural damages before failure. Among SHM techniques, Lamb waves have become widely used since they can cover large areas from one single location. Due to the development of various structural simulation programs, there is increasing interest in whether SHM data obtained from the simulation can be verified by experimentation. The objective of this thesis is to determine Lamb wave responses using SHM models in ABAQUS CAE(a Finite Element Analysis(FEA) program). These results are then compared to experimental results and theoretical predictions under isothermal …

Lamb Wave Propagation In Varying Thermal Environments, Jennifer P. Andrews

Theses and Dissertations

During flight, launch, and reentry, external surfaces on aerospace vehicles undergo extreme thermo-acoustic loads resulting in structural degradation. Structural health monitoring techniques are being devised to evaluate the health of these structures by locating and quantifying structural damage during and after flight. One such technique uses Lamb wave propagation to assess damage on the surface and through the thickness of thin materials. The objective of this study was to assess the sensitivity of piezo-generated Lamb wave propagation to isothermal and thermal gradient environments using both theoretical and experimental methods. Experimental isothermal tests were conducted over a temperature range of 0-225 …

Blind Multiridge Detection And Reconstruction Using Ultrasonic Signals, Rekha Katragadda

LSU Master's Theses

Time-frequency signal analysis has been widely applied in the modern radar, acoustic, sonar and ultrasonic signal processing techniques. Recently, the nondestructive testing (NDT) techniques via the ultrasonic instrumentation have shown the striking capability of the quality control for the material fabrication industry. In this thesis, we first provide a general mathematical model for the ultrasonic signals collected by pulse-echo sensors and then design a totally blind, novel, signal processing NDT technique relying on neither a priori signal information nor any manual effort. The signature signal can be blindly extracted by using the automatic optimal frame size selection for further modeling …

Theory Of Eddy Currents For Nondestructive Testing, Craig Charles Biddle

Retrospective Theses and Dissertations

Eddy current inspection methods are used extensively in industry for the nondestructive testing of a wide variety of materials and product applications. The general theory of eddy current inspection is described. Equations defining the depth of penetration are derived from Maxwell's equations. Signal analysis methods are described using coil impedance diagrams. The impedance diagrams for a number of inspection applications are presented. A discussion of the techniques for theoretical calculation of the impedance of a coil is described. Typical coil configurations and instrumentation techniques are discussed.