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

Master of Science in Engineering, Youngstown State University, 2020, Department of Civil/Environmental and Chemical Engineering

In any civil engineering structure, damage resulted from the construction phase or developed over time affects the structural performance and may result in its failure. Early-stage damage detection is necessary for maintaining structural safety, serviceability, and minimizing the cost throughout the structural operation. Various destructive and conventional non-destructive damage detection techniques employed over the years are either laborious or, uneconomical, and require access to the entire structure. These limitations were addressed by developing the vibration-based methods for regular structural health monitoring. This holistic approach includes analyses of vibration signals and the related modal parameters. The change in these parameters may be used for detection of damage. In this research, modal frequency was used as a parameter to detect damage. The objective is to identify damage using natural frequency. To achieve this objective, several tests were conducted on simply supported steel beams having an open transverse crack with varying depths and locations. The analytical, numerical, and experimental approaches generate frequencies for the first three vibrating modes. The analytical approach considered the beam as the Euler-Bernoulli beam. Analytical frequencies were found from the solution of a partial differential equation by applying the boundary conditions. Vibration signals collected from the portable digital vibrometer (PDV 100) were analyzed using the Fast Fourier Transform (FFT) technique to achieve modal frequencies of the steel beam. In ANSYS (ANSYS, 2017), the finite element models of the beams were calibrated using the experimental results. The frequency from the analytical approach depends on the crack depth. Therefore, this method cannot produce the actual frequency of a beam with varying damage locations and depths. The graphical plots of the normalized frequency with varying damage depth and damage location was used to study the impact o (open full item for complete abstract)

Committee: AKM Anwarul Islam PhD (Advisor); Shakir Husain PhD (Committee Member); Richard Deschenes PhD (Committee Member) Subjects: Civil Engineering; Engineering

Doctor of Philosophy, Case Western Reserve University, 2019, EMC - Mechanical Engineering

The mechanical properties of materials are known to be rate- and temperature-dependent. Owing to this, investigations aimed towards the exploration of material behavior (i.e. plasticity, strength, and failure) under thermomechanical extremes has been a subject of sustained interest. The extreme temporal and precise nature of these studies produces special experimental challenges, and as a consequence, knowledge regarding the dynamic response of materials, especially in thermomechanical extremes, is still limited by the deficiency of experimental data. The main objectives of the current study are to 1) develop a reliable experimental scheme for investigating the dynamic inelasticity of metals under thermomechanical extremes. In particular, the focus is on elevated temperature dynamic compressive and shearing resistance of metals at plastic strain rates in excess of one-million/sec and sample temperatures approaching melt. And, 2) to address the need for experimental data on the dynamic response of FCC metals in previously unexplored but important thermomechanical regimes, such as elevated temperatures and plastic strain-rates on the order of 10^5 – 10^9 /s. In order to conduct this research, the single-stage gas-gun facility at CWRU was modified to include a breech-end sabot heater system and a novel fully fiber-optics based normal and transverse motion diagnostics system, which enabled reverse geometry normal and pressure-shear plate impact experiments to be conducted on pure aluminum at elevated temperatures. Additionally, a full characterization of the WC anvil plates was performed. Using these capabilities, elevated temperature normal and combined pressure-shear plate impact experiments were carried out to better understand the high temperature dynamic compressive and shearing resistance of aluminum. These experiments were used to shed light on the temperature-dependence of the shock impedance of aluminum at pressures of around 1.0 – 1.6 GPa, and the tempera (open full item for complete abstract)

Committee: Vikas Prakash (Committee Co-Chair); Bo Li (Committee Member); Sunniva Collins (Committee Member); John Lewandowski (Committee Member) Subjects: Materials Science; Mechanical Engineering

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

Master of Science, The Ohio State University, 2012, Materials Science and Engineering

Electromagnetic forming via die impact has shown results beyond normal forming limits but there is little experimental research presenting the potential of kinetic type presses. This thesis introduces a suite of sheet metal forming methods to assess forming velocity's affect on plane-strain formability using ten different materials within three different categories of sample dimensions. In addition to strain rate effects from each technique, lubricant is varied on self-similar forming dies to investigate impact geometry and frictional conditions. Three very different ‘press' types are used to apply a large uniform pressure over flat sheet materials into a single sided die that is accompanied by no draw-in of the material. These presses include a traditional quasi-static press, QS; an electromagnetically driven high speed press, HSP; an electromagnetically driven uniform pressure actuator, UPA; and an electromagnetically exploded foil, EF. Experimental energy requirements for electromagnetic forming, EMF, limits are reported along with characterization of the HSP peak current and velocity through the use of a Photon-Doppler Velocimeter, PDV. Cross-sectional photographs and thickness strain measurements are presented to see the strain rate effects on the samples. The resulting methodologies allow for predictions of shearing conditions and forming limits of nominally flat grooved structures.

Committee: Glenn Daehn PhD (Advisor); Peter Anderson PhD (Committee Member) Subjects: Materials Science