Doctor of Philosophy, The Ohio State University, 2023, Materials Science and Engineering

The work in this dissertation is focused on the development of new manufacturing technologies at the early stage. Two concepts are developed in the category of Impact Welding and two in the category of Metamorphic Manufacturing. Under the Impact Welding category two different welding processes are studied, the Vaporizing Foil Actuator Welding and the Augmented Laser Impact Welding processes. Both of these processes were demonstrated to produce impact welds between traditionally unweldable aircraft aluminum alloys which performed as well or better than comparable riveted joints without the need for the drilling of holes or removal of surface coatings. Additionally, basic engineering guidelines are established for the design of foils for the Vaporizing Foil Actuator Welding process and basic performance metrics are established for the Augmented Laser Impact Welding technique. Two new data analysis techniques were developed for the Augmented Laser Impact Welding process which were validated by the use of high-speed videography. Models of the impact conditions for both of these impact welding techniques were established. For the Augmented Laser Impact Welding process, a technique for accurately measuring the welding velocity during an impact event is developed and validated. Metamorphic Manufacturing refers to the agile use of deformation to create shapes and modify microstructure. In this area two concepts were developed where metallic components are transformed from one shape into a second more desirable and useful form. A device and process for bending medical fixation plates to match patient skeletal anatomy is developed. The method can make arbitrary controlled shapes and may save time in the operating room for reconstruction surgeries. The second concept is an approach for Robotic Blacksmithing, a process for incrementally transforming a malleable material into useful shapes by deformation. This concept was initially developed on a purpose-built desktop robotic (open full item for complete abstract)

Committee: Glenn Daehn (Advisor); Antonio Ramirez (Committee Member); Boyd Panton (Committee Member); Enam Chowdhury (Committee Member) Subjects: Materials Science; Medicine; Robotics

Master of Science, The Ohio State University, 2022, Materials Science and Engineering

The process of laser impact welding utilizes impact welding and laser-driven flyers to form solid-state, metallurgical welds between similar or dissimilar metallic flyers and targets. With chemically augmented laser impact welding, stronger and thicker metal flyers and targets can be welded together. Using a high-powered laser, a laser pulse is shot through a transparent tamping layer onto a translucent layer of chemical liquid and the bare surface of a metallic flyer. The energy from the laser pulse detonates the chemical augment and the pressure created from the explosion is confined by the tamping layer. This pressure is directed towards the flyer that is then driven to velocities in the hundreds of meters per second within 20 microseconds. Under the correct conditions, high speed and acceptable impact angle between the flyer and target, jetting will occur. The jet cleans the surface of the flyer and target of oxides, and the two surfaces will form a solid-state, metallurgical bond. Using a chemical augment, thicker, stronger flyers and targets can be welded compared to unaugmented laser impact welding. With the chemical augment, a 3J, 8.1ns laser pulse can weld a 0.5mm Al2024-T3 flyer to a 0.5mm Al2024-T3 target. To explore the capabilities of chemically augmented laser impact welding, two chemical augments were used as candidates for the process. Various tamping materials and thicknesses were also investigated along with variance in the laser spot diameter. The velocities of flyers were measured using Photon Doppler Velocimetry and a thicker tamping layer produced higher velocities and larger deformations than thinner tamping layers did with the same parameters. The strength of the welds between 0.5mm Al2024-T3 flyers and targets were also measured using a tensile test. Over two-thirds of the welded samples failed by nugget pullout during these tensile tests, validating the strength of the welds formed. Micrographs of a welded sample were also collected to o (open full item for complete abstract)

Committee: Glenn Daehn (Advisor); Boyd Panton (Committee Member) Subjects: Engineering; Materials Science; Metallurgy

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, 2014, Materials Science and Engineering

Towards the end goal of high rate tensile characterization of any material, existing ideas and newly developed technology have been combined in the form of a test platform dubbed the FIRE system. The acronym stands for Fully Instrumented Ring Expansion, a concept that is capable of evaluating the dynamic behavior of a wide range of materials in tension at strain rates well in excess of 1000/s. At the center of the design is a collection of techniques used to impulsively drive ring shaped samples radially outward in a highly symmetric fashion. This geometry avoids many of the traditional pitfalls associated with high rate testing such as end effects and critical extension speeds. Precision velocimetry has been adapted to the system utilizing state of the art optical and electronic equipment via a subassembly known as PDV (Photon Doppler Velocimetry). The PDV capabilities at present include determination of sample velocities up to 3.2 km/s with simultaneous displacement resolution on the order of 1-10 microns. As validation of the techniques developed, numerous representative material studies were carried out and compared to established data from other sources. Results were found to be in favorable agreement, verifying the efficacy of the methods. Additionally, the expanding ring test has been applied in conjunction with sample types and actuator technologies not reported previously. This provides an expanded usefulness to the test, which has been developed to the point now of being user friendly.

Committee: Glenn Daehn Dr. (Advisor); Michael Mills Dr. (Committee Member); John Lippold Dr. (Committee Member); Alan Hirvela Dr. (Committee Member) Subjects: Electromagnetics; Engineering; Experiments; Materials Science; Mechanical Engineering; Mechanics; Metallurgy; Physics