Engineering Commons^™

Characterization Of The Acquisition Parameters Of A Submersible Gamma-Ray Computed Tomography System, Zhongmin Jin

Doctoral Dissertations

"The purpose of this work is to study a component of a submersible gamma-ray computed tomography (CT) system used in the non-destructive testing of irradiated nuclear fuels. The first section of this study proposes two acceleration approaches for rapidly modeling a transmission-type gamma-ray tomography system. The first relies on Monte Carlo simulations with a monodirectionally biased source sampled from a sub-volume of the whole source volume. This method estimates the real count rate using analytical correction factors. The second way of acceleration is based on deterministic calculations that use the Beer-Lambert law and detector response characteristics. It shows that both …

Ultrasonic Non-Destructive Evaluation Of Additively Manufactured Polymer-Ceramic Composites, Christian Alexander Ruiz

Open Access Theses & Dissertations

Digital light processing (DLP) is an attractive additive manufacturing technique due to its ability to create ceramic parts with complex geometries. DLP uses ultraviolet light to polymerize a slurry comprised of ceramic powder and photosensitive resin in layers to create solid parts. Printing parameters such as light intensity and exposure time are critical when producing these parts. Improper parameters can lead to over or under-curing, adversely impacting print quality and strength. Samples were printed at varying layer exposure times and then tested using ultrasonics to determine the degree of conversion. Additionally, ultrasonics were used as a non-destructive technique to obtain …

Feasibility Of Applying Motion Magnification In Subsurface Defect Detection For Concrete And Fiber-Reinforced Polymer Specimens, Nagavardhani Malineni

Graduate Theses, Dissertations, and Problem Reports

Irrespective of size and complexity, every civil infrastructure needs certain scrutiny regarding its structural health to ensure its serviceability during its lifetime. In olden times such scrutiny was done with the aid of destructive testing methods using sensors that required cumbersome and expensive installations and led to the destruction of at least part of the tested specimen. However, in recent times, many non-destructive methods, such as acoustic emission testing, electromagnetic testing, and laser testing methods have emerged, leaving the specified tested specimen undisturbed. With the advancement in sensor technology like motion magnification and with the help of access to high-speed …

Implementation Of Ground Penetrating Radar (Gpr) And Complementary Non-Destructive Testing On Concrete Structures, Macy Spears

Electronic Theses and Dissertations

This study analyzes the application and practicality of different non-destructive testing (NDT) methods for the inspection of reinforced concrete. There are two studies discussed in this paper. The first one is a laboratory investigation, utilizing ground penetrating radar (GPR) on concrete slabs that consisted of simulated defects to mimic those found in real concrete structures. This served as a preliminary experiment to verify the GPR data with the design of the slabs. The following study describes a field investigation on an old bridge deck, which involved multiple testing methods. The techniques used were GPR, impact echo (IE), ultrasonic pulse echo …

Cost-Effective Non-Destructive Testing Of Biomedical Components Fabricated Using Additive Manufacturing, Santiago Fabian Cobos

Electronic Thesis and Dissertation Repository

Biocompatible titanium-alloys can be used to fabricate patient-specific medical components using additive manufacturing (AM). These novel components have the potential to improve clinical outcomes in various medical scenarios. However, AM introduces stability and repeatability concerns, which are potential roadblocks for its widespread use in the medical sector. Micro-CT imaging for non-destructive testing (NDT) is an effective solution for post-manufacturing quality control of these components. Unfortunately, current micro-CT NDT scanners require expensive infrastructure and hardware, which translates into prohibitively expensive routine NDT. Furthermore, the limited dynamic-range of these scanners can cause severe image artifacts that may compromise the diagnostic value of …

Innovations In Aligned And Overmolded Long Fiber Thermoplastic Composites, Shailesh P. Alwekar

Doctoral Dissertations

Long fiber thermoplastic (LFT) composite materials are increasingly used in high performance lightweight automotive, sporting, and industrial applications. LFT composites are processed with extrusion-compression molding (ECM) and/or injection molding (IM). Melt extrusion offers unique opportunities to align long fibers in a thermoplastic polymer melt. The properties of LFT materials are highly influenced by processing techniques which leads to different porosity content, fiber length distribution, and fiber orientation distribution. Hence, it is important to understand the various LFT processing techniques and their effect on mechanical, thermal, and microscopic properties.

The fundamental process-property relationships in LFT composites are investigated in this dissertation. …

Active Thermography For Additive Manufacturing Processes, Nicholas Jay Wallace

Theses and Dissertations

The goal of the research conducted for this master's thesis is to understand if active thermography is a suitable technique to detect (identify) and measure (approximate depth and or size) defects in additive manufacturing (AM) processes. Although other non-destructive measurement techniques exist, active thermography is an attractive option for AM applications because of the short measurement times that could be implemented between each layer of a print, and because of the relatively inexpensive equipment required. However, pulse thermography is typically applied to detect larger defects (>1 mm) in materials with high thermal conductivity. It was uncertain if active thermography …

Characterization Of Local Void Content In Carbon Fiber Reinforced Plastic Parts Utilizing Observation Of In Situ Fluorescent Dye Within Epoxy, Wyatt Young Warner

Theses and Dissertations

Experimentation exploring the movement of voids within carbon fiber reinforced plastics was performed using fluorescent dye infused into the laminates observed through a transparent mold under ultraviolet light. In situ photography was used as an inspection method for void content during Resin Transfer Molding for these laminates. This in situ inspection method for determining the void content of composite laminates was compared to more common ex-situ quality inspection methods i.e. ultrasonic inspection and cross-section microscopy. Results for localized and total void count in each of these methods were directly compared to test samples and linear correlations between the three test …

Full-Scale Study Of Infrared Thermography For Assessing Surface And Subsurface Defects In Pavements And Other Civil Infrastructure, Aidin J. Golrokh

Boise State University Theses and Dissertations

Infrared thermography (IRT) is an effective non-destructive testing method in the field of concrete and asphalt pavements inspection. IRT is used to have an initial evaluation of the surface and near surface of pavements in a very time effective manner compared to other types of nondestructive testing (NDT) methods. Different aspects of IRT and its use to assess surface and subsurface defects in different types of pavements are being studied and evaluated in our research group. The effect of the depth of delamination inside concrete pavement on IRT technique is being studied. It is suggested by our group that there …

Interlaminar Damage Detection In Composite Materials, Hariharan Rangarajan

Williams Honors College, Honors Research Projects

Using ceramic matrix composites (CMCs) for high-temperature applications in jet engines increases durability and reduces weight and cooling requirements resulting in improved efficiency and fuel savings. Understanding, detecting, and monitoring different types of damage is essential to achieve optimal performance of CMC components. The Direct Current Potential Drop (DCPD) method is a non-destructive technique of estimating damage in composite materials.

DCPD technique works by measuring nodal potential differences when current is flown through the material. Direct current spreading in different woven and laminate composites is modeled to follow a ladder resistor network in which the nodal voltages decrease exponentially as …

Qualitative Evaluation Of Cfrp-Concrete Bond Using Non-Destructive And Destructive Testing Methods, Ankita Anil Lad

Civil Engineering Theses

CFRP (Carbon Fiber Reinforced Polymer) laminates have been used as externally bonded reinforcements for retrofitting and structural strengthening of concrete structures. The adequacy of the CFRP bonding highly depends on the bond integrity between the concrete and CFRP laminates. Considering the reliability of this bonding technique, premature debonding of laminates from the concrete substrate is a major concern. The bond performance may be influenced directly by various parameters; some of the parameters like surface wetness, surface preparation, presence of voids in concrete substrate and overhead versus on the top installation of CFRP laminate have been discussed in this study. During …

Condition Assessment Of Concrete Bridge Decks Using Ground And Airborne Infrared Thermography, Tarek Omar

Electronic Thesis and Dissertation Repository

Applications of nondestructive testing (NDT) technologies have shown promise in assessing the condition of existing concrete bridges. Infrared thermography (IRT) has gradually gained wider acceptance as a NDT and evaluation tool in the civil engineering field. The high capability of IRT in detecting subsurface delamination, commercial availability of infrared cameras, lower cost compared with other technologies, speed of data collection, and remote sensing are some of the expected benefits of applying this technique in bridge deck inspection practices. The research conducted in this thesis aims at developing a rational condition assessment system for concrete bridge decks based on IRT technology, …

Condition Assessment Of Decommissioned Bridge Decks Treated With Waterproofing Membranes And Asphalt Overlays, Eric Scott Sumsion

Theses and Dissertations

The objective of this research was to assess the condition of four decommissioned bridge decks treated with waterproofing membranes and asphalt overlays following the completion of their service lives. Large samples were cut from each of the bridge decks immediately prior to demolition and taken to the Brigham Young University Highway Materials Laboratory, where extensive sampling and testing was performed. Methods used to evaluate the condition of the bridge deck samples included visual inspection, hammer sounding, Schmidt rebound hammer testing, resistivity testing, half-cell potential testing, linear polarization testing, cover depth measurement, and chloride concentration measurement. The samples were removed from …

Structural Health Monitoring Of Concrete Systems, Matthew Kelly Jones

Theses and Dissertations

Concrete material is widely used around the world for the construction of many infrastructure including highway bridges, residential and commercial building, dams, electric power generation plants, and nuclear power plants. It is therefore practical to continue development of both improved structural systems as well as innovative condition assessment techniques for new and existing concrete structures. This thesis includes two studies which focus on structural health monitoring of concrete systems. The first project deals with performance assessment of an in-situ precast approach slab system and the second is an investigation of acoustic emission (AE) as a condition assessment technique for alkali-silica …

Sensitivity Of Resistivity Measurements On Concrete Bridge Decks To Operator-Controlled And Concrete Material Variables, Natasha Christine Barrus

Theses and Dissertations

The objectives of this research were to investigate the sensitivity of two-prong and fourprong resistivity measurements to certain operator-controlled variables and to conduct a direct comparison of the sensitivity of two-prong and four-prong resistivity measurements to certain concrete material variables. Four full-factorial experiments were designed for this research. In the experimentation on operator-controlled variables with two-prong resistivity testing, main effects that are both statistically significant and practically important include hole depth and surface water. In the experimentation on operator-controlled variables with four-prong resistivity testing, probe position, surface water, and prong spacing are all neither statistically significant nor practically important. This …

Analysis Of Selected Factors Affecting Concrete Cover Measurements On Bridge Decks, Jeffrey Ryan Hoki

Theses and Dissertations

The objective of this research was to quantify the effects of selected parameters on the accuracy of concrete cover measurements on bridge decks. This research involved three full-factorial laboratory experiments each designed to investigate one of three primary variables. These primary variables included distance to a parallel adjacent bar, distance to a reinforcement intersection, and incorrect bar size input for the cover meter. Each experiment also involved four secondary variables known to affect cover readings. These secondary variables included actual cover depth, meter brand, antenna type, and bar size. Statistical analyses were performed to determine the significance of each factor. …

Experimental And Analytical Application Of The Hodd Method For The Detection Of Damage, Jacob Merkley

All Theses

Detecting damage location and severity in civil engineering structures has become an important research topic in the past several decades. Various non-destructive damage identification methods using dynamic properties from ambient and forced vibration have been developed. Researchers have shown that higher order derivatives of mode shapes of the 2nd and 4th order can be effective in detecting damage in civil engineering structures. Furthermore, these higher order derivatives are sensitive to small changes in global stiffness facilitating the detection of small degrees of damage.
In this study a modal analysis is performed on analytical and experimental simply supported beams using the …

Evaluation Of Unknown Foundations, Ronald W. Florkowski

USF Tampa Graduate Theses and Dissertations

In recent years, bridge foundations have been in the spotlight throughout the nation. Bridges built over running water are susceptible to erosion or scour around their foundations. The reduction in load capacity to piers and abutments pose a safety risk to highway motorists. It has become necessary for engineers to examine and monitor these "scour critical" bridges. The difficulty arises with subsurface foundations of which very little is known about their construction. Hence, the methods applied to analyzing "Unknown Foundations" have become a necessary topic of research.

This thesis explores a method to determine foundation lengths. Similar to Sonic Echo …

Single-Sided Noninvasive Inspection Of Multielement Sample Using Fan-Beam Multiplexed Compton Scatter Tomography, Matthew A. Lange

Theses and Dissertations

As aircraft age, corrosion forms upon unobservable surfaces, particularly at the junction of the sheet aluminum and the steel rivets used to attach the sheets to the airframe, degrading the aircraft s airworthiness. Previous research developed a noninvasive technique for the evaluation of the material composition of aluminum surfaces, utilizing the information encoded in the energy spectra of Compton-scattered gamma emissions. The spectra are gathered by a six-element, high purity germanium detector array. A, first principles, deterministic computer code is used to reconstruct a two-dimensional map of the electron density of aluminum samples. Previous efforts, to image pure aluminum samples, …