Doctor of Philosophy, The Ohio State University, 2023, Physics

The proton spin puzzle, the question of how the angular momentum within the proton is distributed, remains an open problem in physics. One of the missing pieces is the small-x helicity of the quarks and gluons. These distributions can be described in the shock wave formalism using small-x helicity evolution of the polarized dipole amplitude. In this dissertation we review the formalism of the polarized dipole amplitudes. From here we may numerically investigate the asymptotically small x properties of the helicity distributions, determining the power-law scaling behaviour. We find good agreement with Bartels, Ermolaev and Ryskin. We then analyze the world polarized deep-inelastic scattering (DIS) and semi-inclusive DIS (SIDIS) data at low values of x < 0.1, using small-x evolution equations for the flavor singlet and nonsinglet helicity parton distribution functions (hPDFs). The hPDFs for quarks, antiquarks, and gluons are extracted and evolved to lower values of $x$ to make predictions for the future Electron-Ion Collider (EIC). While the existing low-x polarized DIS and SIDIS data are insufficient to constrain the initial conditions for the polarized dipole amplitudes in the helicity evolution equations, future EIC data will allow more precise predictions for hPDFs and the g_1 structure function for x values beyond those probed at the EIC. Using the obtained hPDFs, we discuss the contributions to the proton spin from quark and gluon spins at small x.

Committee: Yuri Kovchegov (Advisor); Mike Lisa (Committee Member); Stuart Raby (Committee Member); Richard Furnstahl (Committee Member) Subjects: Physics

Doctor of Philosophy, The Ohio State University, 2021, Materials Science and Engineering

Laser driven shockwaves are currently being used in an assortment of industrial applications and physics research. Although used in many studies, one of the most common and successful industrial applications is the process of laser shock peening (LSP). LSP has been a developing field of study since the 1970's but only experienced commercial success in the early 2000's. Despite the relatively long history, the physical impulses created by the process have been infrequently and incompletely investigated. This study was constructed to investigate the impulse loads created across the LSP tradespace parameters and evaluate how industry can better analyze LSP parameters and utilize the data in their own optimization. Using photon doppler velocimetry, peak pressures and magnitudes generated by LSP conditions are evaluated in titanium and aluminum alloys in this study. The studies are extended to be inclusive of opaque overlays on the target materials that act as thermal barriers and also modify the pressures generated. This data is critical to understanding and optimizing the LSP process for different material applications and LSP treatment purposes and has not been comprehensively investigated prior to this work. Extension of the pressure data to physical treatments was validated through measurements of residual stress with x-ray diffraction and simulation of the process with finite element simulations. Finite element studies were also used to define the converged boundaries for the newly defined impulse parameter space and demonstrated prediction of residual stresses in comparison to experimental datasets. Results of these studies are expected to provide additional understanding of the LSP process for both industrial use and extension to optimization studies of LSP treatments. It is the intent of these cumulative studies that a more thorough detailing of LSP impulse and simulation capabilities are available for those interested in evaluating the process.

Committee: Glenn Daehn (Committee Co-Chair); Stephen Niezgoda (Committee Co-Chair); Enam Chowdhury (Committee Member) Subjects: Materials Science

Doctor of Philosophy, The Ohio State University, 2019, Materials Science and Engineering

High-temperature metallic materials such as nickel-based and titanium alloys are attractive as skin structures for aerospace vehicles. They can allow significant performance improvement and mass reduction in aircraft. However, there are substantial challenges in welding and forming them affordably for service. This project examines the use of impulse-based methods, as enabled by the vaporizing foil actuator method, for the impact welding and precise shaping of alloys Ni - 718, Ni - 625, Ni - 230, and Ti 6242. The mechanical properties and weld microstructure of four similar and Six dissimilar VFA spot welding combinations are presented and analyzed. Microhardness measurements showed the absence of a heat affected zone (HAZ). The dissimilar Ni - Ni joints and Ni - Ti joints exhibited high loads to failure in lap-shear tests and show great potential for applications involving transition joints, repair welding, medical devices, and more. The VFA method is cheap, safe, fast, durable, and marks the advancement in the solid-state joining of dissimilar nickel and titanium systems. Nickel alloys typically exhibit low springback during quasi-static forming processes. However, the large amounts of strain hardening that occurs during these operations often requires a second annealing stress relief operation. Titanium alloys are commonly known to exhibit high springback levels due to the high strength to stiffness ratios of titanium alloys. Sheet metals components are usually shaped by hot or superplastic forming. This process is expensive and has long lead-times. This work examines an athermal process to relax or remove the residual stresses and elastic strains in sheet metals. All the materials explored, especially titanium showed significant improvements in shape conformance when processed through the VFA method. Recent shock-based calibration studies have provided some insight into the previously unconfirmed mechanism of springback relief. The driving hypothesis f (open full item for complete abstract)

Committee: Glenn Daehn (Advisor); Stephen Niezgoda (Committee Member); Xun Liu (Committee Member) Subjects: Engineering; Materials Science

Doctor of Philosophy, The Ohio State University, 2019, Aero/Astro Engineering

Impinging oblique shockwaves are commonplace in both external and internal flow paths on high-speed vehicles, and their prevalence will only increase with the continued pursuit of readily deployable flight vehicles. These shockwaves cause sharp pressure rises that create intense localized structural loads. Recently, impinging shocks waves have been identified as a mechanism to induce panel flutter, which presents a major concern for fatigue failure and increased noise generation. Critical to this is the fact that loss of panel stability occurs at different operating conditions and panel stiffness compared to classical panel flutter. To date, research on shock-induced panel flutter has been limited to a two-dimensional, semi-infinite assumption. Additionally, most existing simulations on the topic are restricted to inviscid flow. This dissertation documents expanded understanding of shock-induced panel flutter phenomena by exploring the effects of three-dimensionality and viscosity on the aeroelastic system. The analysis is carried out numerically using the Air Force Research Laboratory FDL3DI code. The first configuration considered is Mach 2 inviscid flow over a square panel. The panel is simply supported on all four edges, and the shockwave is set to impinge along the mid-chord. A parametric sweep is performed over non-dimensional dynamic pressure and incident shock angle. Mean, standard deviation, and time history of the panel response are presented. Additionally, the panel response is projected onto the natural mode shapes in order to gain deeper insight into the characteristics of the structural response. Fluid pressure snapshots are also provided. In general, the panel flutter response is qualitatively similar to previous studies on the semi-infinite configuration. Flutter amplitude is slightly lower and flutter frequency slightly higher for the three-dimensional configuration in all cases. Additionally, the critical non-dimensional dynamic pressure is i (open full item for complete abstract)

Committee: Jack McNamara Ph.D. (Advisor); Datta Gaitonde Ph.D. (Advisor); Miguel Visbal Ph.D. (Committee Member); Jen-Ping Chen Ph.D. (Committee Member) Subjects: Aerospace Engineering; Mechanical Engineering

Bachelor of Sciences, Ohio University, 2017, Physics and Astronomy

Core collapse supernovae are an important class of objects in stellar evolution research as they are the final life stage of high mass stars. Supernovae in general are classified into several spectral types; this paper explores SN 2005da, classified as a Type Ic, meaning it lacks hydrogen and helium lines. The supernova was originally classified as a broad-lined Type Ic (Type Ic-BL), with expansion velocities near maximum light greater than or approximately equal to 15000 km/s. However, some of the elements present in the spectrum, namely carbon and oxygen, have narrower lines (FWHM approximately equal to 2300 km/s) than other elements, indicating an interaction with a previously ejected envelope. The supernova is also found to have a decay time, with a change in magnitude over 15 days following maximum light of about 1.4 magnitudes, that is significantly faster than typical Type Ic or Ic-BL. This is more akin to a rarer object type known as a Type Ibn, although it lacks the characteristic narrow helium lines of this type. Therefore, SN 2005da appears to be unlike known examples of Type Ic supernovae.

Committee: Ryan Chornock (Advisor) Subjects: Astronomy; Astrophysics; Physics

MS, University of Cincinnati, 2011, Engineering and Applied Science: Aerospace Engineering

Mixed compression inlets offer a potential increase in pressure recovery compared to conventional external compression inlets at Mach numbers above two. However, these inlets suffer from problems with shock boundary layer interactions which cause flow instabilities and severe performance reductions. Previous experiments conducted at the University of Michigan used a wind tunnel with glass side walls and an extensive test section to measure the shock boundary layer interaction associated with a single oblique shock. This work presents an investigation of possible improvements to the current single shock experiment. A 10° oblique shock generator was designed by researchers at the University of Michigan and simulated at the University of Cincinnati. The 10° design did not start in the actual wind tunnel, but was successfully simulated by bypassing the transients from quiescent flow with the help of an initial solution generated from one dimensional inviscid nozzle theory. The residuals from the simulation leveled off at higher levels than expected in some mesh blocks, which indicates unsteadiness. The same case was then simulated in a time accurate manner, and showed very small variations in the solution over time. The magnitude of these variations were large enough to prevent the residuals in the steady simulation from dropping, but small enough that an averaged solution could be used for analysis. A grid dependency study was conducted and found that the 24 million node grid is very close to being grid independent. A new design was desired that would allow the actual tunnel to start, and this resulted in a 6° oblique shock generator. This geometry allows the tunnel to start, and produces a more benign shock boundary layer interaction than the 10° oblique shock generator. A follow up experiment has been designed where the oblique shock is followed by a normal shock and a subsonic diffuser. This new configuration will provide insights into the effects that combined ob (open full item for complete abstract)

Committee: Mark Turner ScD (Committee Chair); Shaaban Abdallah PhD (Committee Member); Paul Orkwis PhD (Committee Member) Subjects: Aerospace Materials

MS, University of Cincinnati, 2010, Engineering and Applied Science: Aerospace Engineering

The presented work shows that Prandtl-Meyer expansion can be used as a foundation to predict bleed rate for a single bleed hole oriented normal to a supersonic freestream. A CFD study was used to explore flowfield phenomena that can be used in conjunction with Prandtl-Meyer expansion theory to improve model accuracy. Of these phenomena, the shear layer and barrier shock were the best defined and their geometric placement within the bleed hole were the basis for the bleed rate model. Coefficients of variation of the root mean square error between data and predictions were between 0.10 and 0.15 for all but the highest of freestream Mach numbers evaluated. Development of an analytical bleed rate model and recommendations for follow-on activity are presented.

Committee: Awatef Hamed PhD (Committee Chair); Prem Khosla PhD (Committee Member); John Slater PhD (Committee Member) Subjects: Aerospace Materials