Doctor of Philosophy (PhD), Ohio University, 2017, Civil Engineering (Engineering and Technology)

Low-temperature cracking is a major pavement distress for asphalt pavements in most northern parts of the United States and other colder regions of the world. Pavements exposed to cold conditions are subjected to thermal stresses which can result in cracking when the induced stresses exceed the tensile strength. Local governments and road agencies spend large sums of money annually to repair defects in pavements caused by low-temperature cracking. Researchers need straightforward and routine test devices to characterize asphalt mixture's low-temperature performance in the laboratory. These tools are also required to design pavements that can perform satisfactorily in cold temperatures, and for the prediction of frequency and magnitude of cracks developed in asphalt pavements. The low-temperature performance characteristics of asphalt mixtures can be grouped into two broad components. There is the stiffness and thermal contraction component which accounts for the magnitude of strains or stresses induced in the mixture during cooling. The strength or fracture toughness component accounts for the ability of the mixture to resist the induced stresses and to prevent cracking. The main objective of this dissertation was to develop straightforward and routine tests devices for low-temperature characterization that would account for these two components of mixture's low-temperature performance. The Ohio Coefficient of Thermal Contraction (CTC) device developed as part of this dissertation was shown to produce repeatable test data. Asphalt mixture thermal strains recorded from the CTC device fitted the Bahia-Anderson CTC mathematical model for mixtures with a coefficient of determination (R2) greater than 0.999. Mixture properties such as binder grade, binder content, aging and the inclusion of recycled materials [Recycled Asphalt Pavement (RAP) and Recycled Asphalt Shingles (RAS)] resulted in a significant change in the CTC. Asphalt mixtures prepared with two aggrega (open full item for complete abstract)

Committee: Kim Sang-Soo Dr. (Advisor); Nazzal Munir Dr. (Committee Member); M. Sargand Shad Professor (Committee Member); Masada Teruhisa Professor (Committee Member); Mark McMills Dr. (Committee Member); Yu Xiong Dr. (Committee Member) Subjects: Civil Engineering; Engineering; Geotechnology

Doctor of Philosophy, The Ohio State University, 2009, Mechanical Engineering

In this dissertation, finite element models are used to investigate catastrophic failure of thermal barrier coatings (TBCs) due to delaminations along susceptible interfaces of thermally grown oxide (TGO) with the ceramic top coat and the inter-metallic bond coat. The materials and geometries in the studies are chosen to be representative of TBC materials in real applications. The characteristics of the failure modes along the TGO and bond coat interface (e.g. buckling instability and strain energy driven delamination propagation) are investigated using thermo-elastic finite element models. The solution of a linear elastic eigen-value problem determines the onset of the buckling instability with a pre-existing delamination between bond coat and the TGO. The virtual crack extension method is employed to study strain energy release rate driven interfacial delamination at wavy interfaces. The materials and geometries in the study are chosen to be representative of TBC materials in real applications. Extensive sensitivity analyses are conducted to identify the critical design parameters affecting the onset of buckling and extension of interfacial delamination, as well as to develop parametric relations that enhance the understanding of these mechanisms. Finally, a numerical exercise demonstrates that the buckling instability is the leading failure mechanism at flat interfaces or at the locations of minimum cross-section in a wavy interface. However, in the vicinity of waviness, crack extension becomes a dominant mode of failure. The top coat crack initiation and propagation is investigated using a thermo-elastic finite element model with bond coat creep. Cracks are assumed to initiate when the maximum principal stress exceeds rupture stress of the top coat. A sensitivity analysis estimates the contribution of geometric and material parameters and forms a basis to develop parametric relation to estimate maximum principal stress. Subsequently, crack propagation simulati (open full item for complete abstract)

Committee: Somnath Ghosh PhD (Advisor); Mark Walter PhD (Committee Member); James Williams PhD (Committee Member); June Lee PhD (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2022, Welding Engineering

Ductility-dip cracking (DDC) in face-centered cubic (FCC) alloys, such as nickel-based alloys and 300-series stainless steels, is a challenge faced by nuclear power generation. Aging reactors need to be repaired via multipass weld overlays to extend their lifetime. DDC often occurs in the first few layers of these overlays, and the nuclear industry has low flaw tolerance, making DDC subject to costly repair and rework. The prevailing theory describing DDC is based on observations of grain boundary (GB) sliding, microvoid formation, and the effect of GB tortuosity. This work aims to quantify the effect welding process parameters and welding generated stresses have on the formation of DDC and to provide clear avenues for productive future research. The main project objectives include the development of methodology, based on combining physical experiments and computational modeling, for prediction of DDC in multipass welds of austenitic alloys that is applicable for materials selection and process optimization. An additional study on the DDC fracture surface was conducted due to findings from the experimental component. Research began with the development of a Gleeble-based experimental procedure that evaluates a material's susceptibility to elevated temperature embrittlement. The procedure is called simulated strain ratcheting (SSR), and preliminary testing led to the use of the imposed mechanical energy (IME), defined as the integral of experienced stress vs. strain, as a parameter for quantification of thermo-mechanical loading in Gleeble tests and FEA models of multipass welds. This experimental procedure was used to successfully generate DDC in various nickel-based alloys and 310 stainless steel. Fracture surfaces generated from this testing were found to exhibit thermal faceting (TF), which warranted further study. Samples which contained high amounts of DDC, or those which experienced fracture, also generally experience higher IME than those which showed no s (open full item for complete abstract)

Committee: Boian Alexandrov (Advisor); Avraham Benatar (Committee Member); Carolin Fink (Committee Member); John Lippold (Committee Member); Michael Mills (Committee Member) Subjects: Engineering; Materials Science; Metallurgy

Doctor of Philosophy (PhD), Ohio University, 2020, Civil Engineering (Engineering and Technology)

The long-term performance of a bridge deck depends on its resistance to bridge cracking. Most of these cracks are initiated at the early age. Early age cracking of bridge decks is a typical issue in the U.S. that reduces bridge service life. Therefore, internally cured concrete (ICC) has been used in some states to reduce or eliminate the development of cracks in reinforced concrete decks. In this study, the early age behavior of ICC deck and the effect of the internal curing on the long-term behavior of the bridge was measured and evaluated in the laboratory and field for newly adjacent constructed bridge, which were located on Route 271 in Mayfield, Ohio. Two different types of concrete mixtures were utilized for the decks: conventional concrete (CC) and internally cured concrete (ICC). Firstly, the ICC and CC mixtures were examined in the laboratory in terms of a mechanical properties test, a plastic shrinkage test, a free shrinkage test, and a restrained shrinkage test. Second, the field behavior of an ICC deck and an adjacent CC deck during their early age and long-term performance were evaluated. Also, the shrinkage development for both decks was examined during the very early age. Instrumentation was used to measure the concrete and reinforcement strains and the temperature in both bridges. The instrumentation and results for both bridges are discussed. Laboratory results indicated that using pre-wetted lightweight concrete in the concrete mixture led to decreased density, coefficient of thermal expansion, and free shrinkage strain, and increased tensile strength and cracking time of concrete compared to conventional concrete. In the field, from the early age test, it was observed that the time to develop concrete shrinkage was approximately 5-6 hours after casting the deck of the ICC and the CC. The results indicated that the majority of shrinkage occurred during the first week after concrete placement. However, the deck with ICC experienced less longitud (open full item for complete abstract)

Committee: Eric Steinberg Professor (Advisor) Subjects: Civil Engineering

Master of Science, University of Akron, 2020, Civil Engineering

Low temperature cracking is a major distress for flexible pavements in cold regions. Most tests that are used currently to predict asphalt mixture performance at low temperatures require long time and effort to perform the test and analyze the data. A new laboratory test called the Ohio CTE device (OCD) has been developed as a more practical alternative to predict the asphalt mixture performance at low temperatures. This study presents an evaluation of the Ohio CTE device (OCD) in terms of effort for sample preparation, testing time, repeatability of test results, and complexity of the analysis of test data. To assess the ability of the Ohio CTE device (OCD) to predict the low temperature performance of asphalt mixtures, results obtained from this test were correlated to three other common low temperature tests, including the creep compliance and indirect tension test (IDT), the thermal stress restrained specimen test (TSRST), the asphalt concrete cracking device test (ACCD). Nine asphalt mixtures prepared using the same aggregate blend and different asphalt binders were included in this study. High correlation was observed between the Ohio CTE device (OCD) test results and results obtained from the other laboratory tests. In addition, the Ohio CTE device (OCD) was found to be advantageous over the other low temperature tests in that it requires significantly less time to prepare the test samples, which suggests that the Ohio CTE device (OCD) can be used as a routine test for low temperature characterization of asphalt mixtures.

Committee: Ala Abbas Dr. (Advisor); Wieslaw Binienda Dr. (Committee Member); Nariman Mahabadi Dr. (Committee Member) Subjects: Civil Engineering; Engineering

Doctor of Philosophy (Ph.D.), University of Dayton, 2019, Mechanical Engineering

Heat removal capacity of catalytically cracked jet fuel using supercritical n- dodecane as a jet fuel analogue in a cylindrical packed bed reactor is examined. The cracking reactions are endothermic, and can be used in the design of a potential hypersonic vehicle fuel reactor. Fuel endotherm and product distribution were examined using three catalysts: a commercially available platinum catalyst on a ceramic support matrix, cerium applied to the platinum catalyst, and cerium applied to a ceramic support. Where much previous research has used catalyst coated tubes, this study made use of a solid catalyst structure in a packed bed to distribute the catalyst throughout the fuel flow in order to provide more surface catalyst sites. The packed bed was assumed to be an ideal plug flow reactor, with catalytic reactions that are radially uniform across the reactor diameter. For some experiments, water was added to the fuel mixture prior to heating for steam assistance to the n-dodecane pyrolysis reaction in order to examine the steam effect on carbon production and endotherm. Where previous research has used either used a catalyst to aid in endothermic thermal management or has focused on water addition to pyrolysis reactors in order to reduce coke formation, this study combines these approaches. A catalyst is used to initiate endothermic reactions at lower temperatures than would be achieved by thermal cracking alone, in conjunction with steam addition to reduce coking. The packed bed catalyst configuration provides continued catalytic action even as cracking temperatures increase and thermal cracking becomes dominant, thereby enhancing chemical heat sink. The cerium catalysts out-performed the platinum catalyst both in terms of increased endotherm and decreased carbon deposition. Steam assistance proved beneficial in decreasing carbon deposition, although at the cost of decreased dodecane conversion, hence endotherm. No appreciable product selectivity was observed for stea (open full item for complete abstract)

Committee: Jamie Ervin Ph.D. (Advisor); John Petrykowski Ph.D. (Committee Member); Thomas Reitz Ph.D. (Committee Member); Scott Stouffer Ph.D., P.E. (Committee Member) Subjects: Engineering; Mechanical Engineering

Master of Science (MS), Ohio University, 2017, Civil Engineering (Engineering and Technology)

The continuous use of recycled material in asphalt pavement mixtures, specifically Reclaimed Asphalt Pavement (RAP), Recycled Asphalt Shingles (RAS) and Re-Refined Engine Oil Bottoms (REOB), have developed an increasing need to further evaluate the performance of these mixtures at the micro and macro-levels, as the use of such materials reduces cost of virgin materials and energy consumption. Although asphalt binder, including recycled or additive materials, may meet a desired performance grade (PG) using macro-scale tests, they may lack critical nano-mechanical properties that largely affect long-term performance, such as adhesion and diffusive efficiency between virgin and recycled binders. These commonly overlooked properties can correlate with performance behaviors such as fatigue and low temperature cracking during field performance. This study was conducted in two major parts. Part one was performed with the intent to evaluate the nano-mechanical and blending-diffusive efficiency of toluene and trichloroethylene extracted RAP and RAS binder using tapping mode imagery and force spectroscopy using Atomic Force Microscopy (AFM). Furthermore, this study was set to correlate the findings from micro-testing to macro-scale laboratory performance tests including Semi-Circular Bending (SCB) to evaluate fatigue cracking resistance at intermediate temperatures, Asphalt Concrete Cracking Device (ACCD) to evaluate low temperature cracking and AASHTO 283 ITS to study moisture damage susceptibility of intermediate course mixtures with high RAP and RAS contents. Results showed that tear-off RAS material have a significant effect on fatigue and low temperature cracking performance, primarily at long-term aged conditions. Neither tear-off nor manufactured waste RAS binder blend well with virgin binder, whereas RAP shows a zone of blending. AFM imaging indicated all extracted RAS binder had a much rougher surface texture than RAP or virgin binders and did not contain any (open full item for complete abstract)

Committee: Munir Nazzal Dr. (Advisor) Subjects: Civil Engineering; Materials Science

Master of Science, The Ohio State University, 2016, Welding Engineering

High manganese steels are potential candidates for use in cryogenic applications as they exhibit desirable low temperature properties and are a cost-effective alternative to high-Ni steels (i.e. 9%Ni steel, Type 304L) and Invar alloys. Their cryogenic properties are derived from the austenite stabilizing ability of manganese. A potential use for these steels is in the fabrication of liquefied natural gas (LNG) storage tanks. The demand for natural gas is expected to increase 65% by the year 2040 and thus the need for cost-effective materials to replace conventionally used high-Ni alloys during construction of storage and transportation tanks is relevant. When fabricating these LNG tanks, welding is a critical procedure and thus the weldability of these high manganese steels must be evaluated. In this study, the effect of tungsten (W) and boron (B) additions on the microstructure and solidification cracking susceptibility of Fe-Mn-C filler metals was evaluated. Five compositions with tungsten additions up to 4.7 wt% and boron additions up to 27 ppm have been evaluated. Susceptibility to solidification cracking of these filler metals was determined using the Cast Pin Tear Test (CPTT). Solidification simulations were conducted using the Scheil approximation within Thermo-Calc™ and actual solidification temperature range measurements were conducted using the Single-Sensor Differential Thermal Analysis (SS-DTA™) technique. Metallurgical characterization was carried out using both optical microscopy, and scanning electron microscopy. The objective of this study was to determine the optimum range of tungsten and boron additions within the compositional range of interest that provides adequate resistance to weld solidification cracking. Results from Scheil simulations indicated only slight variations in the solidification temperature range (STR) among the alloys tested. The simulations showed that W additions lowered the liquidus temperature and subsequently the STR w (open full item for complete abstract)

Committee: John Lippold (Advisor); Antonio Ramirez (Committee Member) Subjects: Engineering; Materials Science; Metallurgy

Master of Science (MS), Ohio University, 2004, Civil Engineering (Engineering)

Development and comparison of the asphalt binder cracking device to directly measure thermal cracking potential of asphalts

Committee: Sang-Soo Kim (Advisor) Subjects: Engineering, Civil