Master of Science, The Ohio State University, 1967, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2008, Graduate School

Committee: Not Provided (Other) Subjects:

MS, University of Cincinnati, 2023, Engineering and Applied Science: Aerospace Engineering

The development of additive manufacturing techniques which enable the creation of complex-shaped components (CSCs) have brought about significant improvements of many engineering systems. These components, usually printed as a single part using high density metallic alloys, are characterized by surfaces of high curvature and complicated internal geometry usually consisting of many vanes/channels. While CSCs have been highly optimized for their respective systems, the widespread usage of such components has been stunted due to the sub-adequate ability of current nondestructive testing (NDT) techniques to detect defects and flaws inside the complex geometries. Until recently, the most reliable form of NDT on CSCs was ultrasonic inspection utilizing water immersion because of water's ability to transfer ultrasonic energy through channels and cavities inside a CSC. Unfortunately, this method is extremely limited because of water's severely lower impedance compared to many CSC's ultrasonic impedance. Recently, a promising development in NDT has improved the viability of CSCs by encapsulating said parts inside crystal clear ice, dubbed Cryo-ultrasonic testing (Cryo-UT). Compared to typical water immersion testing ice coupling promotes significantly more ultrasonic energy transmission into test components and increases the critical angle at which waves can enter components; thus, increasing the efficiency of locating defects. These benefits can be expanded upon by altering the properties of the ice medium. This study details a methodology to create and subsequently freeze an alumina/water nanofluid, which then acts as an ultrasonic couplant bonded with aluminum test components of rectangular geometry. The couplant's properties of density, velocity, and ultrasonic impedances were measured with ultrasonic inspection tests in Pulse-Echo and Through Transmission on a multitude of different test configurations. A 2D Axisymmetric simulation created in-house was used to ob (open full item for complete abstract)

Committee: Francesco Simonetti Ph.D. (Committee Chair); Gui-Rong Liu Ph.D. (Committee Member); Joseph Corcoran Ph.D. (Committee Member) Subjects: Aerospace Engineering

Doctor of Philosophy, The Ohio State University, 2018, Materials Science and Engineering

Elastic constants Cij are one of the essential properties to understand mechanical behaviors of materials. They are indispensable inputs for physics-based models of microstructural evolution and constitutive/micro-mechanistic simulations of properties. Young's modulus, bulk modulus, shear modulus and Poisson's ratio are just different combinations of elastic constant components and they only describe mechanical behavior under specific conditions. Elastic constants Cij are the intrinsic parameters fully describing the elastic mechanical behavior under any given condition. Several experimental methods have been developed to measure elastic constants of materials but most of them require single-crystal samples, which are time-consuming to grow. Many compounds are not even possible to grow single crystals. As a result, only about 1% (roughly 1500 out of 160,000 kinds) of distinct solid compounds have experimental values of the elastic constants. To change this scenario, an innovative experimental method has been developed to measure single-crystal elastic constants directly from polycrystalline samples, without the need of growing single crystals. The new method is based on measuring and modeling femtosecond laser-generated surface acoustic waves (SAWs) that only propagate on the sample surface and decay with the distance from the surface into the sample exponentially. An elastodynamic model has been developed to predict the SAW phase velocities along any general direction at given full elastic constants and density. A femtosecond laser-based experimental set-up was applied to generate and detect SAW velocities along any specific direction. To enable measuring narrow-band SAW velocities along a single direction without any interference from multiple modes, an organic PDMS (polydimethylsiloxane) film of 1-D grating was placed on top of the sample surface to guarantee only one SAW mode survives to be detected. With modeling predictions and experimental measurements (open full item for complete abstract)

Committee: Ji-Cheng Zhao (Advisor); Wolfgang Windl (Committee Member); Stephen Niezgoda (Committee Member) Subjects: Acoustics; Materials Science; Mechanical Engineering

PhD, University of Cincinnati, 2017, Engineering and Applied Science: Aerospace Engineering

Ceramic matrix composites (CMCs) are poised to revolutionize jet engine technology by enabling operation temperatures well beyond those possible with current superalloys, while reducing active cooling requirements and engine weight. Manufacturing of parts formed by silicon-carbide (SiC) fibers in a SiC matrix is now well advanced, with the first non-structural static components already in service in the CFM Leap engine. In order to expand the scope of application of CMCs to rotating parts, it is necessary to characterize the modes of failure of these materials at temperatures beyond 1100 C. In this context, the ability of nondestructively monitoring the formation and progression of damage in CMCs specimens during high-temperature mechanical testing is critical. Due to its excellent sensitivity and low cost, ultrasonic inspection is a well developed technique which allows to create accurate two and three-dimensional images of specimens by either mechanically scanning them or using phased array probes. However, the elevated temperature precludes use of traditional actuation techniques. In this context, the generation and detection of elastic waves using laser beams is an attractive possibility to characterize CMCs in a hostile environment with high sensitivity. In this work, the first experimental assessment of the feasibility of noncontact laser ultrasonic inspection of SiC/SiC flat coupons is presented. An Nd:Yag laser is used to excite ultrasonic waves on one side of the specimen while a Michelson interferometer detects the signals emerging on the other side at the epicenter position. The lasers are mounted on synchronized linear stages to form C-scans as in conventional immersion ultrasonics while ablation damage to the surface of the specimen is prevented by operating the lasers at low power density. It is shown that it is possible to image interlaminar defects caused by impacts and monitor crack opening under tensile load. Finally, very go (open full item for complete abstract)

Committee: Francesco Simonetti Ph.D. (Committee Chair); San-Mou Jeng Ph.D. (Committee Member); Aaron Sellinger Ph.D. (Committee Member) Subjects: Aerospace Materials

PhD, University of Cincinnati, 2017, Engineering and Applied Science: Aerospace Engineering

The complexity of modern engineering systems is increasing in several ways: advances in materials science are leading to the design of materials which are optimized for material strength, conductivity, temperature resistance etc., leading to complex material microstructure; the combination of additive manufacturing and shape optimization algorithms are leading to components with incredibly intricate geometrical complexity; and engineering systems are being designed to operate at larger scales in ever harsher environments. As a result, at the same time that there is an increasing need for reliable and accurate defect detection and monitoring capabilities, many of the currently available non-destructive evaluation techniques are rendered ineffective by this increasing material and geometrical complexity. This thesis addresses the challenges posed by inspection and monitoring problems in complex engineering systems with a three-part approach. In order to address material complexities, a model of wavefront propagation in anisotropic materials is developed, along with efficient numerical techniques to solve for the wavefront propagation in inhomogeneous, anisotropic material. Since material and geometrical complexities significantly affect the ability of ultrasonic energy to penetrate into the specimen, measurement configurations are tailored to specific applications which utilize arrays of either piezoelectric (PZT) or electromagnetic acoustic transducers (EMAT). These measurement configurations include novel array architectures as well as the exploration of ice as an acoustic coupling medium. Imaging algorithms which were previously developed for isotropic materials with simple geometry are adapted to utilize the more powerful wavefront propagation model and novel measurement configurations.

Committee: Francesco Simonetti Ph.D. (Committee Chair); Gui-Rong Liu Ph.D. (Committee Member); Peter Nagy Ph.D. (Committee Member) Subjects: Acoustics

Doctor of Philosophy, The Ohio State University, 1978, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 1978, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 1972, Graduate School

Committee: Not Provided (Other) Subjects: Biology

MS, University of Cincinnati, 2016, Arts and Sciences: Physics

The most widely used methods for growth of carbon nanotubes (CNTs) arc discharge, laser ablation, and chemical vapor deposition (CVD). Some of these methods have difficulties, such as controlling the quality and straightness of the nanotube in the synthesis of CNTs from substrates. Also, the enhanced plasma chemical vapor deposition method with the catalyst on a substrate produces straighter, larger diameter nanotubes by the tip growth method, but they are short. The difficulty in the floating catalyst method is that the nanotubes stay in the growth furnace for short times limiting growth to about one mm length; this method also leaves many catalyst impurities. One factor that limits CNT growth in these methods is the difficulty of getting enough carbon atoms to the growth catalyst to grow long nanotubes. The motivation of this work is that longer, higher quality nanotubes could be grown by increasing growth time and by increasing carbon atom movement to catalyst. The goal of this project is to use acoustic levitation to assist chemical vapor deposition growth by trapping and vibrating the growing CNTs for better properties. Our levitation system consists of a piezoelectric transducer attached to an aluminum horn and quartz rod extending into the growth furnace. The most important elements of our methods to achieve the acoustic levitation are as follows. 1. Using COMSOL Multi-physic Simulation software to determine the length of quartz rod needed to excite standing waves for levitation in the tube furnace. 2. Determining the resonance frequency of different transducers and horns. 3. Using ultrasound measurement to determine the time of flight, velocity of sound and sound wavelength of different horns. 4. Making Aluminum horns with the appropriate lengths. 5. Using ultrasound measurement to determine the changing of quartz rod velocity of sound and length in the furnace. 6. Mounting the transducer to booster horn and aluminum cylindrical horn abov (open full item for complete abstract)

Committee: David Mast Ph.D. (Committee Chair); Howard Jackson Ph.D. (Committee Member); Frank Pinski Ph.D. (Committee Member); Hans-Peter Wagner Ph.D. (Committee Member) Subjects: Physics

Master of Science in Engineering, Youngstown State University, 2015, Department of Mechanical, Industrial and Manufacturing Engineering

Over the years, many studies have been conducted to study and analyze the grain structures of metal alloys in order for them to have superior structural and mechanical properties. In particular, columnar grains are observed predominantly during rapid solidification of molten metal. This leads to lower mechanical properties and requires expensive secondary heat-treatment processes. This study is aimed at disrupting the formation of columnar grain growth during rapid solidification using ultrasonic vibration and analyzes the effects on grain structure and mechanical properties. A MIG welder mounted on a low cost metal 3D printer was used to deposit ER70S-6 mild steel layers on a plate. A contact type ultrasonic transducer with control system to vary the frequency and power of the vibration was used. The effects of ultrasonic vibration were determined from the statistical analysis of microstructure using ImageJ and micro-indentation techniques on the deposited layer and heat affected zone. It was found that both frequency and interaction between frequency and power had significant impact on the refinement of average grain size up to 10.64% and increased the number of grains by approximately 41.78%. Analysis of micro-indentation tests showed that there was an increase of approximately 14.3% in micro-hardness and 35.77% in Young's modulus due to the applied frequency during rapid solidification. Along with the results from this study, further efforts in modeling and experimentation of multi directional vibrations would lead to a better understanding of disrupting columnar grains in applications that use mechanical vibrations, such as welding, metal additive manufacturing, brazing, and the likes.

Committee: Guha Manogharan PhD (Advisor); Brett Conner PhD (Committee Member); Darrell Wallace PhD (Committee Member) Subjects: Acoustics; Industrial Engineering; Materials Science; Statistics

Master of Dental Hygiene, The Ohio State University, 2015, Dentistry

There are two types of ultrasonic devices used by dental hygienists; magnetostrictive (M) and piezoelectric (P). Research supports using these devices during prophylaxes/periodontal debridement but there is little evidence determining which is superior. The purpose of this study was to determine if any differences between the magnetostrictive and piezoelectric scaling devices existed in calculus removal, patient preference and practitioner preference. Subjects included senior dental hygiene students and patients of The Ohio State University College of Dentistry. This double-blinded study employed a quantitative experimental randomized split mouth design on contra-lateral quadrants for the evaluation of calculus removed by each device. Five calibrated examiners recorded the presence of calculus on the quadrants assigned prior to and post treatment. Upon completion of each device, patients completed a visual analog scale (VAS) to gauge patient preference and each student completed a five point Likert survey to measure practitioner preference. Twenty-three subjects completed the study. Data reveals the M device removed more calculus than the P device (70.5% vs 66.1% respectively). Results from the student survey reveal the M device was significantly more user friendly than the P device. Device M scored an average total likert score of 21.0 vs. 18.7 for device P. Results from the patient VAS reveal M is preferred for discomfort, vibration and noise factors. This data provides strong evidence that device M is preferred for this group of hygiene students. However, all other differences in the data were not significant. This significant difference in student practitioner preference is likely due to a major limitation of the previous experience imbalance between the two devices. This reveals a need for required experiences with both ultrasonic devices throughout the dental hygiene students' clinical education.

Committee: Michele Carr MA (Advisor); Rachel Henry MS (Committee Member); John Walters DDS, MMSc (Committee Member) Subjects: Dentistry

Master of Science, The Ohio State University, 2008, Welding Engineering

Ultrasonic metal welding (UMW) is a solid-state joining process in which materials are held together under moderate forces while applying localized high frequency shear vibrations, creating a true metallurgical bond. While ultrasonics have been applied extensively to joining soft materials, such as copper and aluminum, applications for joining more advanced materials are limited. UMW has generally not been considered for more advanced materials due to poor tooling life and inadequate ultrasonic power levels. In a relatively short period of time, developments in UMW equipment and potential tool materials, may allow UMW to be applied to these more advanced metals. Using commercially-available ultrasonic spot welding equipment, the ultrasonic weldability of 304 and 410 stainless steel, commercially pure and 6Al-4V titanium, and Nickel-base superalloys 625 and 718 was investigated. Tool materials developed for friction-stir weld tooling were used to develop new ultrasonic tools. Tool textures and designs were also evaluated.

Committee: Karl Graff (Advisor) Subjects:

Doctor of Philosophy, Case Western Reserve University, 2008, Chemical Engineering

Previous research endeavors resulted in a process to recover solid particles and oil droplets from aqueous suspensions. This process involves applying a one-dimensional resonant ultrasonic field to the suspension while it is flowing through or resting in a rectangular chamber. The same process has been utilized here for gas bubbles in an aqueous medium. Bubbles in this system move to the acoustic pressure antinodes, based on the density and compressibility of the bubble and the surrounding fluid as well as the driving frequency and the radius of the bubble.To obtain a fundamental understanding of the movement of a single bubble within the acoustic chamber, a balance of the relevant physical forces was completed: primary acoustic force, buoyancy force, and drag force. The resulting equations could be used to determine the position of a single bubble within the chamber and the velocity at which that bubble would be moving toward those positions. A microscopic mathematical model was developed to predict the relative trajectory of a bubble pair in an acoustic field. This model not only took into account the primary forces previously discussed, but also inter-bubble effects: secondary acoustic force, van der Waals force, hydrodynamic interactions, and Brownian diffusivity. The trajectory analysis was used to track the movement of the bubble pairs under a variety of operating conditions and the results were compared to experimental data. This data was then used to calculate volume cleared by the collision of different bubble pairs, thus describing the kinetics of the collision process. The results from the models were then compared to experimental data obtained by injecting small numbers of bubbles into an acoustic chamber. This comparison was done by taking video of bubbles colliding, mapping their path, and comparing this to the trajectory determined from the bubble pair model. The projected trajectory and the experimental trajectory were shown to be in good agreement. (open full item for complete abstract)

Committee: Donald Feke PhD (Advisor); J. Adin Mann PhD (Committee Member); Robert Edwards PhD (Committee Member); Dov Hazony PhD (Committee Member) Subjects: Chemical Engineering