Master of Science in Engineering (MSEgr), Wright State University, 2012, Materials Science and Engineering

As the research and development of surface heating methods have increased in the recent years, the consensus has been reached amongst the injection molding community that an elevated mold surface temperature near or greater than the polymer solidification temperature provides acceptable replication of the desired micro-structured parts. The laser heating experimental work and simulation development carried out includes two sample sizes similar to those used in injection molding. A 100W CO2 laser incident on three samples of different surface roughnesses has shown to have elevated temperatures via thermal cameral data and thermocouple measurements. Among five different laser spot sizes varying from 1 mm to 20 mm in diameter, heating rates from 1 second to 5 minutes have shown temperatures rises from 230C to often over 1000C, when measuring 1 mm below the heated surface. A particular case with a laser spot size of 3 mm in diameter incident on a 30 mm thick sample has absorbed 13.2W of laser energy and yielded a surface temperature over 1800C through simulation. A new design has been proposed to allow for a more practical heating method that is feasible, economical, and deemed the next step in future work for laser heating in the rapid mold surface heating community.m

Committee: Shia-Chung Chen PhD (Committee Co-Chair); George Huang PhD (Committee Co-Chair); Wen-Ren Jong PhD (Committee Member) Subjects: Mechanical Engineering

Master of Science in Electrical Engineering, University of Toledo, 2011, College of Engineering

Energy storage devices such as electrochemical batteries typically do not perform well at low temperatures where energy density and peak power suffer. One battery chemistry that is particularly susceptible to this phenomenon is lead-acid which is used predominantly in automobile and truck applications for cranking internal combustion engines during starting. Several approaches have been implemented to aid in cold engine cranking which include external battery preheat techniques as well as using temperature-independent parallel energy storage devices such as ultracapacitors. An alternative approach proposed in U.S. Patent No. 6,259,229 teaches the use of alternating currents for internal heating of the battery electrolyte. This approach was examined and its implementation was studied for 24-volt battery systems intended for cold cranking diesel engines in large military vehicles. Prototype high-frequency heaters were developed and tested for operation in extreme cold climates to -40°C with peak-to-peak currents up to 600 Amps in the frequency range of 5 kHz to 50 kHz. Experimental results demonstrate significant improvement in pulse discharge performance (approaching that of room temperature) using large alternating currents to heat small and medium size battery packs. The research suggests a scale factor that relates the magnitude of heating current to the ampere-hour rating of the battery. However, for large battery packs it is estimated that currents may approach or exceed 1000 Amps peak-to-peak making a compact, cost-effective solution impractical. Additionally, an alternative approach was tested on a large-size battery pack which combines efficient low-current external and internal heating.

Committee: Thomas Stuart PhD (Advisor); Mohsin Jamali PhD (Committee Member); Richard Molyet PhD (Committee Member) Subjects: Automotive Engineering; Electrical Engineering

Master of Science (M.S.), University of Dayton, 2024, Aerospace Engineering

Modern aircraft are overburdened by electrical systems, which are continually increasing their power demands. To generate power on aircraft flying in high speed regimes where high temperatures are imposed by viscous heating, solid state devices can be employed. The high temperature gradient across the thermal protection system of the aircraft creates an ideal environment for thermoelectric generator (TEG) application. The North American X-15 was chosen for its high speed fight profiles and wealth of information available. The fight profiles and geometry will be used to gather data in a more applied sense. One-dimensional codes have been written to model the system's performance over the course of a specified fight profile. Utilizing generic relations, the flow temperature was determined through radiative equilibrium methods, which was then fed to the remaining system. The performance of the system was evaluated over the X-15 high speed mission fight profile. The thicknesses of each component of the system were varied until an optimal range was found. The optimal values found were used as the basis for the remaining computational modeling and physical testing. A high-fidelity modeling effort has been completed to model both the high temperature flow and the transient thermoelectric generator operation. The high temperature flow model is solved in parallel with a conduction heat transfer model of the vehicle skin. This allows the flow and solid bodies to react to one another throughout the transient operation. The models are loosely coupled to a high-fidelity model of a thermoelectric generator. The specific TEG model has been constructed to represent a physical module that was obtained for the physical test articles. Accompanying the computational modeling, two physical test articles have been developed and studied. The first consists of a single TEG stack consisting of a skin material, the TEG, and a heat sink. The second test article includes multiple TEGs within s (open full item for complete abstract)

Committee: Rydge Mulford (Committee Chair); Jose Camberos (Committee Member); Taber Wanstall (Committee Member); Andrew Schrader (Committee Member) Subjects: Aerospace Engineering; Engineering; Mechanical Engineering

Master of Science (M.S.), University of Dayton, 2015, Civil Engineering

Resistive heating of nanocomposite material is proposed for use in many applications because of its light weight and low current requirements. When the nanocomposites are resistively heated, thermal stresses starts arising in it due to mismatch of CTE between the fiber and matrix of the nanocomposite. A nanocomposite material can withstand only limited thermal stress when it is resistively heated. If the thermal load is too high, or combined with other external loads, the nanocomposite can fail by means of delamination, crack formation, warpage and other related modes. Hence, studying the thermal stress that develops in nanocomposites upon resistive heating will help in preventing otherwise unanticipated failures. The objective of this effort was to develop and experimentally validate a Finite Element Method model for evaluation of the thermal stress arising in nanocomposite material upon resistive heating. In order to fill the technology gap of predicting thermal stress in resistively heated nanofiber composites, a finite element method (FEM) model was created. This model was created using ABAQUS® software. To verify the results of the model, the experimental method of hole-drilling was adopted. The nanocomposite considered for the research were a carbon/glass hybrid with epoxy resin and a glass/epoxy composite reinforced with CNT Buckypaper. The experiment was based on the principle of redistribution of stress when the hole is drilled in the composite and the relieved strain is measured by a strain gage rosette. The strain release corresponds to the thermal stress that was present before the drilling the hole. The thermal stress results of hole-drilling method were compared with the FEM model result, validating the model and analysis results. The verified FEM model can be used to predict thermal stresses arising in nanocomposites and preventing failure when the nanocomposite is resistive heated and externally loaded.

Committee: Thomas Whitney (Advisor) Subjects: Aerospace Materials; Automotive Materials; Civil Engineering; Engineering; Materials Science; Nanotechnology

Doctor of Philosophy, The Ohio State University, 2012, Food, Agricultural and Biological Engineering

Currently, the world's food industry has great interest in producing high-quality shelf-stable foods, in particular liquid foods containing solid pieces. One of the promising technologies for this purpose is continuous ohmic heating, which involves the passage of an alternating electrical current for the purpose of internal heat generation. To ensure sterility in continuous ohmic heating systems, the slowest-heating solid piece needs to receive sufficient heat treatment at the outlet of the post-heating holding section. Because in-situ noninvasive temperature measurement of moving pieces in continuous flow is not feasible, this research aims to develop mathematical models, coupled with microbiological validation, to ensure that the entire product is rendered sterile. For this purpose, it was necessary to study a sufficiently large number of samples to ensure that at least one scenario involving a fast-moving particle in the 99th percentile was sampled. A residence time distribution (RTD) study was conducted in a pilot-scale ohmic system using radio frequency identification (RFID) methodology to determine the residence time of a sample of at least 300 particles. The mathematical model, consisting of solution of the electric field, flow, heat transfer and inactivation kinetic problems, coupled with the information from the RTD study, computed the lethal effect of the cold spot of such a solid particle, and predicted the required size of the holding tube. Thermal verification of the mathematical model was conducted to compare the simulated temperatures with experimental temperature profiles for the liquid phase at the outlet of heating and holding sections. Finally, microbiological validation of the model was conducted using at least 300 solid pieces, each individually inoculated with Clostridium sporogenes ATCC 7955 (PA 3679) spores, which were processed through the system, recovered and cultured to determine if survivors existed post-processing. It was also necessary (open full item for complete abstract)

Committee: Sudhir K. Sastry PhD (Advisor); Ahmed E. Yousef PhD (Committee Member); Gonul Kaletunc PhD (Committee Member) Subjects: Agricultural Engineering; Food Science; Microbiology

Master of Science in Chemical Engineering, Cleveland State University, 2007, Fenn College of Engineering

Polymers are generally known for their excellent insulative properties. The addition of carbonaceous fillers such as carbon black and graphite within a polymer matrix can impart electrical and thermal properties making them good conductors. The resulting composites can be used in applications requiring and/or ranging from electromagnetic and radio frequency interference (EMI/RFI) shielding, electrostatic discharge (ESD) and heaters/heating elements to which metals have been the materials of choice. The advantages of using such composites include cost reduction, part consolidation, chemical resistance, lighter weight, and ability to easily design into complex three dimensional shapes via injection molding. For this work, various conductive thermoplastic composites were investigated as a metal (Ni-chrome heating element) alternative and/or substitute for use as heating elements through mechanisms of Joule heating. First, composites and test specimen were prepared via melt extrusion and injection molding respectively. Thereafter, electrical thermal and mechanical properties were characterized using both ASTM and non ASTM techniques. Results were then modeled using statistical software to determine correlations between formulations to responses and whether these results are desired and or meaningful. Results from experiments indicated significant advantage in using semi-crystalline polymers as the base carrier due to the superior electrical properties at equivalent filler loading compared to amorphous based composites, a criterion in joule heating. It was also determined that heating rate and maximum/plateau temperature was mainly a function of specimen resistance (formulation parameter) and voltage setting. Finally, the model obtained for plateau temperature was found to be significant. This indicated it is possible to develop polymeric type heaters with operating temperatures above 100°C (current technology) and as high as 200°C. Moreover, these composites would have (open full item for complete abstract)

Committee: Nolan Holland (Advisor) Subjects: Engineering, Chemical

Doctor of Philosophy, Case Western Reserve University, 2004, Biomedical Engineering

Mathematical models are developed to quantitatively analyze tissue and cellular responses to chronic in vivo heating in calves. Disks for heating and temperature measurements are implanted in the thoracic cavity. A constant heat flux is maintained at the disk surface for up to seven weeks. Tissue temperatures are measured by thermistors placed in needles at various distances from the disk surface. From temperature responses with the heat turned off and on for less than 1 hour, tissue perfusion is estimated by optimal fitting the output from a bio-heat equation to the experimental data. A quasi-steady thermal model is established to predict muscle tissue temperature for heating at 0.06 - 0.12 W/cm 2 up to seven weeks. For chronic heating with initial tissue temperature less than 47¢XC, tissues adapt by increasing capillary density, which allows more capillary blood flow and reduce tissue temperature. After seven weeks of heating at 0.08 W/cm 2 , perfusions of muscle and lung tissues show a statistically significant increase of 3-fold and 2-fold, respectively. At a heat flux of 0.06 W/cm 2 , the changes are less apparent. At a heat flux of 0.04 W/cm 2 , the changes are negligible. Immuno-histochemical data from muscle tissue provides the basis for quantitative analysis of cellular responses to chronic heating. With an input of 0.08 W/cm 2 , capillary density significantly increases under chronic heating, i.e., angiogenesis. Above normal body temperature and below 43¢XC, cells express heat shock protein 70 (HSP70), proliferate, and secrete angiogenic factors, such as basic fibroblast growth factor and vascular endothelial growth factor. A mathematical model is developed to analyze the mechanistic process associated with chronic heating responses of endothelial cells, HSP70-expressing cells, and growth factors. With longer heating, the cell number densities and growth factor concentrations increase while their spatial distributions move closer to the heat source. Conver (open full item for complete abstract)

Committee: Gerald Saidel (Advisor) Subjects: Engineering, Biomedical

Master of Science, Miami University, 2025, Mechanical Engineering

In this work, twenty vertical aluminum plates were fabricated with micro-channel features and tested to evaluate their defrosting effectiveness. Manufacturing techniques included the use of micro-milling, fluorosilane surface coatings, and/or silica nanospring (SN) mats. Given the intended application was heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems, striking a balance between defrosting performance and manufacturing cost was a primary focus. Minimizing the cost was achieved by mitigating the “edge effect” through strategically-located micro-channels. The “edge effect” refers to a phenomenon where droplets cling to the bottom edge of vertical surfaces during defrosting and are not removed. Although full-plate SN coatings were observed to have defrosting percentages as high as 90.3%, their current cost is likely prohibitive for HVAC&R applications. In contrast, micro-channels located at the bottom of vertical surfaces coupled with a fluorosilane coating proved to be a promising balance between performance and cost. By treating only the bottom edge of the plate, manufacturing times were significantly reduced, and the defrosting performance remained comparable to fully-treated plates. General observations about surface defrosting performance in terms of efficiency metrics were also outlined and discussed.

Committee: Andrew Sommers (Advisor); Edgar Caraballo (Committee Member); Carter Hamilton (Committee Member); Giancarlo Corti (Committee Member) Subjects: Engineering; Fluid Dynamics; Mechanical Engineering

MS, University of Cincinnati, 2024, Engineering and Applied Science: Mechanical Engineering

This thesis provides comprehensive insights into the optimization of thermoelectric (TE) systems for small scale energy generation and efficient air cooling and heating proposing new strategies that pave the way for more sustainable and efficient TE applications. The first project examines thermoelectric room air cooling and heating, focusing on a novel design model that optimize the coefficient of performance (COP) and cooling power, with extensive experimental verification based on Abhishek Saini's previous theoretical work [1]. This study focuses on air-to-air heat transfer configuration using a dual-sided TE cooling system with cost-effective design approach integrating commercially available TE modules with efficient heat exchangers and counterflow air streams. System-level evaluations validate the results, showing temperature differences, ?T, and COP across different currents and flow rates. A maximum cooling COP of 4.4 and a heating COP of about 6.5 at optimized current levels for the commercial TE modules were obtained and the analysis shows that parasitic thermal and electrical losses significantly reduced COP and temperature drop by over 50 %. Further optimization on cooling and heating, considering convection heat transfer, interface thermal conductance, and geometric factors like TE leg thickness and module fill factor, suggest potential to triple the temperature difference, increase COP by 1.5 times, and double performance through design adjustments. The second project explores a thermal analysis and simulation study on the impact of sidewall air cooling on the power output and efficiency of solar thermoelectric generators (STEGs) featuring a novel V-shaped TE design, previously introduced by Xinjie Li [2]. This V-shape TE design enables elimination of additional electrodes in the module to reduce electrical resistance and enhance voltage generation. The V-shaped legs not only act as TE elements, but also as heat sinks with sidewall air convecti (open full item for complete abstract)

Committee: Je-Hyeong Bahk Ph.D. (Committee Chair); Kishan Bellur Ph.D. (Committee Member); Sarah Watzman Ph.D. (Committee Member); Raj Manglik Ph.D. (Committee Member) Subjects: Engineering

Doctor of Philosophy, Case Western Reserve University, 2025, Chemical Engineering

Direct air capture (DAC) of CO2 is a keystone technology in global plans to mitigate climate change. While the existing materials capable of performing this difficult separation can absorb high amounts of CO2 from air, the heat required to regenerate them for reuse imposes an immense energy tax. With projected energy demands for DAC exceeding 120 petajoules per year by 2030 (nearly the total annual electricity consumption of Ireland), more efficient materials and processes are vital to reaching net zero CO2 emissions. Ionic liquids (ILs) – salts that melt below 100 ˚C – are a class of solvents with exceptional tunability and negligible volatility, making them excellent candidate materials for DAC. However, a major barrier to the implementation of ILs in DAC is their high viscosity, limiting the diffusion rate of CO2. Through fundamental property characterization, spectroscopic investigation, and lab-scale performance analysis, this thesis seeks to build the scientific foundation for leveraging the advantages of ILs while mitigating their weaknesses by creating composite materials with ILs, enabling high performance DAC sorbents that can be regenerated using dielectric heating (the same heating mechanism as a kitchen microwave). We first explore the complex role that hydrogen bonding plays in CO2 binding mechanisms when diluting amino acid ILs with ethylene glycol to lower their viscosity. We reveal through collaborative study with computational chemists that hydrogen bonding can limit the interactions between amine binding sites, preventing their deactivation and resulting in maintained gravimetric capacity upon dilution. Next, we demonstrate the first successful regeneration of an IL by microwave irradiation. We reveal through finite element modeling that experimental trends in heating rate when varying frequency and material are highly dependent on the geometry of the system. Finally, we investigate the formation of composites between an IL and a metal organic (open full item for complete abstract)

Committee: Burcu Gurkan (Advisor); Christine Duval (Committee Member); Michelle Kidder (Committee Member); Pavel Fileviez-Perez (Committee Member); Rohan Akolkar (Committee Member) Subjects: Chemical Engineering

Master of Science, The Ohio State University, 1977, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1970, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy, The Ohio State University, 2024, Food, Agricultural and Biological Engineering

Bacterial spores, among the most resistant organisms on earth, can withstand harsh treatments such as desiccation, chemicals, heat, UV, and γ-radiation. Traditional thermal sterilization methods subject food to temperatures of 120⁰-130⁰C for several minutes, degrading its texture, color, flavor, and nutritional properties. Consequently, there is a push for less severe methods, though nonthermal approaches are ineffective against spore-forming bacteria. Ohmic heating (OH), which passes electricity through food, shows promise by significantly enhancing spore inactivation compared to conventional heating (CH) at the same temperature. However, the precise mechanisms behind OH's effectiveness and the influence of different OH parameters (field strength and frequency) on spore killing are not fully understood. To investigate this, genetically modified spores of Bacillus subtilis, lacking crucial components such as small acid-soluble proteins (SASP) and essential inner membrane proteins, were used. By comparing the inactivation profiles of these mutants with wild-type spores, the study aimed to identify the components affected by the electrical aspects of OH. Additionally, the effects of varying electric field strength and frequency on spore inactivation were explored. Understanding these mechanisms could lead to designing a less severe inactivation process, preserving food quality. For accurate comparison between OH and CH, the experimental setup allowed matching temperature histories, eliminating spatial temperature gradients. This setup featured small capillaries as sample holders within a T-shaped OH chamber, ensuring precise heating rates. The process differed from traditional methods by allowing temperature to rise linearly with a constant electric field, followed by immediate cooling, enabling the study of field strength effects without holding time. Clostridium sporogenes, a surrogate for neurotoxin-producing C. botulinum, was tested first. Results indicated t (open full item for complete abstract)

Committee: Sudhir Sastry (Advisor); Ahmed Yousef (Committee Member); VM Balasubramaniam (Committee Member); Dennis Heldman (Committee Member); Peter Setlow (Committee Member) Subjects: Food Science; Microbiology

Master of Science, The Ohio State University, 2024, Chemistry

Surface enhanced Raman spectroscopy (SERS) is a highly sensitive chemically specific method that is capable of trace analyte detection.1–3 One challenge with SERS is that the spectrum must be stable and consistent to accurately identify compounds. The localized surface plasmon resonance (LSPR) that enhances the Raman signal can cause chemical transformations on molecules near the nanoparticles. The SERS peaks can fluctuate in intensity and position, indicating the presence of transient species like ions or other products from photo-induced reactions. The background of SERS spectra has also been observed to increase or decrease depending on the experiment.4–9 All of these effects are convoluted with the role of heating that also results from excitation of the LSPR. This thesis attempts to identify spectral fluctuations due to heating as well as to shed some light on the inner workings of the background observed in the spectra.

Committee: Zac Schultz (Advisor); Abraham Badu-Tawiah (Committee Member); Heather Allen (Committee Member) Subjects: Chemistry

Master of Sciences (Engineering), Case Western Reserve University, 2024, EECS - Electrical Engineering

Atrial fibrillation, a prevalent heart condition, poses significant health risks. Traditional treatment involves cardiac ablation catheters guided by x-ray fluoroscopy, which provides limited two-dimensional heart images and subjects patients to substantial radiation. Utilizing magnetic resonance imaging (MRI) in these procedures offers three-dimensional catheter visualization and eliminates radiation exposure. The MRI's magnetic field can be leveraged in order to control a robotic ablation catheter with small electromagnetic coils in the catheter tip. However, these coils may interact negatively with the MRI's radio-frequency transmitter, causing potential overheating. Prior research led to the development of a compact catheter prototype, primarily to demonstrate its fundamental operational principles. Nevertheless, this prototype's limited size renders it unsuitable for practical application within the human body. The aim of this thesis is to engineer a full-scale catheter, a task that presents considerable challenges due to the demanding conditions of the MRI environment and the occurrence of standing waves on uncoupled elongated wires. This prototype is designed to meet the kinematic workspace specifications identified in earlier studies, while also ensuring full compatibility with a human subject. The prototype maintains a low heat output and does not interfere with the MRI's functionality.

Committee: M. Cenk Cavusoglu (Committee Chair); David Kazdan (Committee Member); Mark Griswold (Committee Member) Subjects: Biomedical Engineering; Electrical Engineering; Engineering; Medical Imaging; Medicine; Robotics

Doctor of Philosophy, University of Toledo, 2023, Chemistry

Neutral glycosylation, using microwave irradiation, is novel in the realm of carbohydrate chemistry. Providing mild reaction conditions, decreased reaction times and enabling good yields with high purity are the major advantages of microwave promoted reactions. Microwave assisted glycosylation is a rapidly emerging method in the field of carbohydrate chemistry. However only very few reports have described microwave assisted glycosylation. We have developed a microwave labile protecting group (MWLPG) which is selectively removed when microwave irradiation is applied, and it is orthogonal to other commonly used protecting groups. A dinitrophenyl (DNP) ring, at the anomeric position, gave good yields and high alpha selectivity with simple to complex glycosyl acceptors. The glycoside of DNP is labile to nucleophiles such as ammonia in methanol, but it is not reactive enough to undergo conventional glycosylation. However, the DNP donor is highly reactive under microwave heating with neutral to slightly basic conditions. In contrast to conventional glycosylation, this can be achieved without the use of chemical promoters, usually consisting of Lewis or Bronsted acids. Thermal activation of highly electron withdrawing sugar donors in the presence of microwave irradiation and in the absence of any external additives, albeit for the partnering acceptor and solvent to dissolve the coupling partners. DMF proved to be the best solvent for the reaction which is polar aprotic solvent with high dielectric constant. DNP donors decorated with electron-donating benzyl ethers showed increased reactivity in comparison to the DNP donors protected with electron-withdrawing acetate and benzoyl protecting groups, which are inert under microwave conditions. We have established a fast, high temperature glycosylation method by employing precise microwave heating.

Committee: Peter Andreana (Advisor) Subjects: Chemistry

Doctor of Philosophy, Case Western Reserve University, 2023, Biomedical Engineering

Small-diameter axons (e.g., unmyelinated C fibers) are commonly afferent axons that carry critical sensory signals. Selective inhibition of dysfunctional small-diameter axons can be useful for basic neuroscience research and lead to treatments for neurological diseases (e.g., neuropathic pain and persistent hypertension), but remains an unmet need. Conventional pharmaceutical targets are distributed throughout the body, which causes systematic side effects. Electrode-based neuromodulation modalities tend to block large-diameter axons first. Other efforts, such as multi-electrode designs, have achieved spatial selectivity, which is challenged by the degradation of electrode performance due to immune responses. There is a need for a modality that can intrinsically and reliably induce size-selective inhibition of small-diameter axons. Our lab and collaborators have demonstrated in previous studies that infrared (IR) neural inhibition (INI) can selectively inhibit small-diameter axons via the heat induced by the absorption of IR light (e.g., 1470 nm, 1860 nm) which thermally accelerates ion9 channel dynamics. In this work, we first explored the possibility of lowering the IR power threshold for INI with isotonic ion replacement using glucose and/or choline in the extracellular fluid. We applied IR and isotonic ion replacement simultaneously to the same nerve segment, both at a sub-threshold level, and the results confirmed that the IR power threshold of size-selective INI can be lowered by isotonic ion replacement. Second, we tested the hypothesis that resistive heating can reproduce the size selectivity of INI. We fabricated a customized resistive heating cuff and tested localized heat application via both resistive heating and INI on the same nerve. The experimental results confirmed that resistive heating can reproduce the size-selective inhibition on small-diameter axons with higher overall energy efficiency. Further numerical simulation showed (open full item for complete abstract)

Committee: Andrew Rollins (Committee Chair); Michael Jenkins (Committee Member); Kenneth Laurita (Committee Member); Dustin Tyler (Committee Member); Hillel Chiel (Committee Member) Subjects: Biomedical Engineering

Master of Science (MS), Bowling Green State University, 1953, MBA

Committee: Lewis F. Manhart (Advisor) Subjects: Business Administration

Master of Science (MS), Bowling Green State University, 1953, MBA

Committee: Lewis F. Manhart (Advisor) Subjects: Business Administration

Master of Science, The Ohio State University, 2022, Welding Engineering

For many years, the defense industry has made large investments into making their armored combat vehicles as light as possible without compromising the security of the operators. These heavy vehicles are less agile and more expensive to operate and transport. Friction Stir Welding (FSW) offers a lightweight solution that promotes the weight reduction of these armored vehicles. Traditional arc welding processes create issues that FSW eliminates. As a solid-state process, FSW utilizes low peak temperatures during the welding process which results in superior mechanical performance due to the reduction of the heat affected zone (HAZ) and the dynamic recrystallization that occurs within the stir zone while simultaneously eliminating the potential for hot cracking and hydrogen induced cracking. The overarching goal of this work is to create welds that exceed the capabilities of current arc welding processes utilized in the armor industry. To achieve this goal, this body of work explores the utilization of various in-process thermal management techniques to improve production time and mechanical performance on High Hard Armor (HHA) Steel. This work also investigates the residual stresses present following FSW of Rolled Homogenous Armor (RHA) steel while also looking into the ballistic strength of friction stir welded RHA joints. The in-process induction heating system allowed for the welding speed to be increased by 50%. When this heating system was paired with an ancillary cooling system, the resulting process produced a non-uniform stir zone with various points of high hardness and a larger heat affected zone. Induction assisted + ancillary cooling FSW produced similar toughness values when compared to conventional FSW in all regions of the weld. Residual stresses were successfully measured utilizing neutron diffraction and align with previous research where in the transverse and normal directions high tensile residual stresses were seen in the advancing side and in the (open full item for complete abstract)

Committee: Desmond Bourgeois (Committee Member); Antonio Ramirez (Advisor) Subjects: Metallurgy