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, 2023, Welding Engineering

Collision welding or impact welding is a solid-state welding technique which enables unique materials joining opportunities. The high velocities and short timescales of the welding process lead to extreme peak collision pressures, high strain rates, low heat inputs, steep thermal gradients, and narrow thermo-mechanically affected zones (TMAZ). These features can be advantageous in the joining of traditionally unweldable materials such as 2XXX or 7XXX series aluminum alloys, and for the joining of dissimilar metals which would form unwanted phases under traditional fusion welding. However, these same features can also make impact welding challenging to control and characterize. Analytic process limits have been developed to calculate limiting flyer velocities and impact angles for welding success as functions of the weld member properties based on the physical mechanisms that enable joining. The maximum impact velocity for a weld is determined by a dynamic solidification cracking mechanism: reflected dynamic tensile stresses arrive to the nascent weld interface prior to full interface cohesion, which is mediated by the presence of interfacial melting. However, current analytic models for the upper limit of the collision welding window were developed for autogenous welds, which develop symmetric stress conditions at impact. In this thesis, we develop alternative formulations to the analytical upper limit of the welding window which better support dissimilar welding. Shock-informed calculation of the asymmetric stress and thermal partitioning between dissimilar weld members is achieved through the application of modified Rankine-Hugoniot relations. We compare the application of the shock-informed upper limit to the existing upper limits in the context of historical data. The shock upper limit is further validated experimentally through the use of The Ohio State University Impulse Manufacturing Laboratory's (IML) Laser Impact Welding (LIW) and Vaporizing Foil Actu (open full item for complete abstract)

Committee: Glenn Daehn (Advisor); Wei Zhang (Advisor); Eric Seiber (Committee Member); Boyd Panton (Committee Member); Avraham Benatar (Committee Member); Kevin Doherty (Committee Member) Subjects: Materials Science; Mechanics

Master of Science, The Ohio State University, 2019, Materials Science and Engineering

Laser impact welding is a relatively new technology that combines the existing technologies of impact welding and laser-driven flyers to create solid state welds between a thin metallic flyer and a target. A high power laser pulse is fired through a transparent confinement layer and onto an ablative layer that is directly attached to the flyer. This ablative layer absorbs the laser energy and is vaporized creating a plasma that is in turn confined by the transparent confinement layer directing the pressure into the flyer. This drives the flyer to velocities of hundreds to thousands of meters per second in under a microsecond. When the flyer impacts the target if the velocity is high enough and the angle between the two is sufficient, the two surfaces of the materials will be cleaned of their oxides, which in turn allows for a solid-state metallurgical bond to be made between the flyer and target. By controlling the laser parameters, much thicker flyers than previously reported can be welded. Using a 24J 65ns pulse, a 305µm 3003Al flyer was welded to 6061-T6Al. These welds were extremely strong and failed through the 3003Al flyer in all cases when peeled. To further push laser impact welding towards a scalable industrial process, liquid backing layers such as water and glycerin solution were studied for their effect on flyer impact velocity. Impact velocity was measured using Photon Doppler Velocimetry and it was determined that while both are suitable for welding, water would be the preferred backing in an industrial application due to its ease of use and low cost. Potential applications of laser impact welding, such as beverage can manufacturing, are also outlined and discussed.

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