Mechanical Engineering Commons^™

Adaptive Machine Learning Framework For Microstructural Optimization And Mechanical Performance Prediction In Steels, Henry Adekola Haffner

Doctoral Dissertations

Evolution of microstructures, such as polygonal ferrite, acicular ferrite, bainite, and martensite, plays a pivotal role in determining the final microstructural and mechanical properties of steel products. Given the established inter-relationship between processing parameters, microstructure, properties, and performance, precise control of phase transformation is essential to achieve pre-determined properties. To understand transformation routes in different steel grades, time-temperature-transformation (TTT) and continuous-cooling-transformation (CCT) diagrams are necessary and can be described using the Johnson-Mehl-Avrami-Kolmogorov equation and Scheil’s additivity rule. This study presents a comprehensive computational framework for predicting and optimizing microstructure and mechanical properties in advanced high-strength steels (AHSS) using adaptive machine …

Manufacturing And Performance Evaluation Of Carbon/Epoxy Laminated Composites Cured Using Single- And Six-Magnetron Microwave Applications, Nayan Pundhir

Doctoral Dissertations

Microwave curing is fast, energy-efficient, and a viable alternative to conventional thermal curing processes. It has been widely adopted for processing carbon fiber-reinforced polymer (CFRP) composites because the high electrical conductivity of carbon fibers enables strong microwave coupling, leading to rapid volumetric heating and reduced energy consumption. The aim of this study is to investigate the use of microwave curing for manufacturing CFRP composites. IM7/Cycom 5320-1 unidirectional prepreg was utilized to fabricate laminated composites in two thickness ranges: 16-layer laminates (2.5 mm thickness) and 64-layer laminates (9.2 mm thickness). Two lay-up configurations were examined: symmetric cross-ply and quasi-isotropic. Different curing …

Critical Parameters Controlling Oxide Scale Formation And Hydro-Descaling Efficiency During Steelmaking, Tochukwu Princewill Ojiako

Doctoral Dissertations

In modern steelmaking, cast slabs are exposed to high-temperature oxidizing environments during secondary cooling, reheating, and hot rolling, resulting in the formation of multilayer oxide scales on the steel surface. These scales interact with mold-flux residues originating from the casting process (CC). The morphology, chemistry, and adhesion of oxide scale strongly influence its removability during high-pressure hydraulic descaling and ultimately determine the surface quality of hot-rolled products. However, the mechanistic relationship between oxide scale evolution, scale-steel interfacial structure, and hydraulic descaling performance remains poorly understood.

This dissertation investigates oxide scale formation, modification, and removal in low-carbon thin-slab steels produced by …

Investigation Of Electrochemical Corrosion Fatigue Mitigation Strategies For Mild Carbon Steel, Joel Andrew Hudson

Doctoral Dissertations

Corrosion fatigue remains a critical durability challenge for steels used in boiler tubes and other safety-critical components, where the interaction of cyclic stresses and corrosive environments accelerates material degradation. This dissertation comprises three experimental studies aimed at advancing mitigation strategies and test methodologies: (1) enhancing corrosion resistance through electrodeposited Fe-Ni anodic coatings, (2) inducing synthetic crack closure to suppress fatigue crack growth, and (3) developing an accessible, low-cost, automated testing system to investigate environmentally assisted cracking (EAC) under controlled laboratory conditions. The first study examined the corrosion behavior of Fe and Fe-Ni electrodeposits synthesized from sulfate-based baths and applied to …

Multiscale Materials Characterization And In-Situ Process Monitoring In Additive Manufacturing Via Non-Contact Optical Thermometry Techniques, Rifat-E-Nur Hossain

Doctoral Dissertations

While additive manufacturing (AM) is experiencing rapid growth, its development is uneven across different branches. Some areas are still emerging, while even the more established branches are still facing ongoing challenges that require further development. Regardless of their development stage, both emerging and mature AM require process monitoring and part characterization. Process monitoring helps to achieve more control over the process and build a self-adaptive system, while characterization of printed parts speeds up process optimization and ensures required quality. Together, process monitoring and build characterization will transform AM into a more dependable and commercially viable technique. Build surface temperature is …

Process-Structure-Property Relationships In Laser Powder Bed Fusion Produced 17-4 Ph Steel, Ben Brown

Doctoral Dissertations

Laser powder bed fusion (LPBF) is a metal additive manufacturing method that produces non-traditional microstructures as a result of the rapid solidification and thermal cycling inherent to the process. When using LPBF-produced material in application, these unique microstructures challenge the applicability of well-developed mechanical property databases achieved by conventional heat treatments. For wider adoption of this technology, a more holistic understanding is necessary on how process attributes develop material structure, which dictate mechanical properties. This dissertation explores the process structure-property relationships in LPBF 17-4 PH steel through systematic evaluation of atmospheric processing and heat treatment effects on microstructure and mechanical …

Experimental Study Of Defects In Coaxial Wire-Based Laser Metal Deposition, Remy Mathenia

Doctoral Dissertations

This work seeks to improve the usability and capability of coaxial wire-based laser metal deposition (LMD) through the experimental study of process parameters on output geometry, directional effects, and defect formation. Wire-based LMD is a directed energy deposition (DED) strategy that uses a focused laser heat source to melt and fuse metal wire as it is deposited. This process is used to build parts layer-by-layer until a desired geometry is accomplished. LMD enables the creation of complex components at a high build rate with low material and energy waste. This work focuses on the deposition of titanium wire in the …

Design Of Real-Time And Energy-Efficient Driver Assist Systems Using Electroencephalogram And Neuromorphic Computing, Nathan Alan Lutes

Doctoral Dissertations

Despite the technological breakthroughs in advanced driver assist systems, distracted driving persists as a major challenge to roadway safety. This investigation advances the body of knowledge towards a solution by developing an individualized driver-state detection method using electroencephalogram (EEG) and neuromorphic computing to provide a less invasive and more energy efficient ADAS solution. It furthermore explores the changes in brain functional connectivity under distracted conditions to better understand brain state information that could be used for neuro-feedback intervention systems. The first contribution introduces the concept of using Convolutional Spiking Neural Networks (CSNNs) for recognition of patterns with movement-intention predictive power …

Enhanced Optimization Of Mass Transfer For Carbon Capture And Wastewater Remediation In Algal Systems Through Algorithmic And Bioprocessing Techniques, Peter Ofuje Obidi

Doctoral Dissertations

The scalability and industrial deployment of algal cultivation systems are limited by suboptimal mass transfer, constraining their effectiveness in carbon capture and wastewater remediation. This research investigated these challenges through integrated optimization methodologies that combine algorithmic frameworks with enhanced bioprocessing techniques to enhance efficiency, economy, and scalability. A System-of-Systems (SoS) meta-architecture was developed using genetic algorithms and fuzzy assessor functions to demonstrate a pathway toward cost reduction. Rigorous mechanical and chemical characterizations were quantitatively analyzed to reveal existing optimization strategies and further evaluated the best strategies to use in enhancing mass transfer for improved biomass yield. The work also integrates …

Data-Driven Mulitiscale Modeling Of Electrochemical Transport, Non-Linear Electrical Contact, And Additive Manufacturing Processes, Emmanuel Olugbade

Doctoral Dissertations

The growing demand for high-efficiency energy systems and advanced manufacturing technologies requires predictive frameworks that link atomic-scale physics with engineering-scale performance. This dissertation develops a unified multiscale modeling approach that integrates molecular dynamics, density functional theory, finite-element analysis, and machine learning to connect structure, transport, and performance across materials and processes. Depending on the interactions involved, the framework employs loose coupling for parameter transfer, tight coupling for two-way feedback, and hybrid coupling where machine-learning surrogates accelerate high-fidelity simulations while retaining physical interpretability. In electrochemical systems, an XGBoost-enhanced single-particle model reproduces P2D-level electrolyte potential dynamics at roughly one-hundredth the computational cost, …

Identification Of Corrosion Damage, Vibration, And Loose Conections In Aircraft Data Transmission Lines Using Reflected And Transmitted Signals; Formulation Of Vegetable Oil-Based Nanofluids As Cutting Fluids For Mql Machining, Saidanvardzhon Valiev

Doctoral Dissertations

This research presents a novel Frequency Domain Transmitometry (FDT) method that uses transmitted signals (S21) to detect and characterize aircraft data transmission lines (ADTL) corrosion damage without additional reflectometry circuitry. Corrosion experiments were conducted according to ASTM G85-A5 over 14 weeks. Combined FDT and reflected signals (S11) analyses revealed distinct three-peak signatures associated with damage and corrosion. The square root of the Area Under the Curve (AUC) of the FDT damage peak and the Full Width at Three-Quarter Maximum (FW3QM) of the S11 damage peak is correlated with corrosion propagation depth and width. S11 signals were further used for vibration …

Sensor Embedding And Thermal Monitoring Strategies For Laser-Foil-Printing Additive Manufacturing, Tunay Turk

Doctoral Dissertations

"This work investigates Laser Foil Printing (LFP), a novel metal additive manufacturing (AM) process that fabricates parts layer-by-layer using metal foils. To enhance LFP productivity, the process steps were optimized, and an 88.1% reduction in processing duration was achieved. A unique aspect of this study was the introduction of laser polishing as an edge polishing technique within the LFP process. This innovative approach, employing an overlapping spiral pattern, leverages selective laser remelting and erosion to effectively suppress elevated edges. To stabilize the molten melt pool, a discrete spot scanning strategy was implemented. The fabricated parts were subjected to detailed analysis, …

Additive Manufacturing Of Multifunctional Materials And Composites, John Michael Pappas

Doctoral Dissertations

"This research focused on developing fundamental knowledge of process-material interactions for additive manufacturing of multifunctional materials that are highly desirable in high-tech industries for potential weight and space savings. Multifunctional materials are very sensitive to defects, which severely hinder performance. Thus, defect formation was systematically studied to develop strategies and methodologies to efficiently fabricate high-performance materials and composites. Blown-powder-based laser additive manufacturing of transparent spinel ceramics was investigated to reduce porosity and cracking, defects that hindered transparency and mechanical properties. A systematic study of processing parameters revealed that laser power and powder flow rate had the largest effects on defect …

Nano-Micro Engineering For Advanced Energy Devices, Tazdik Patwary Plateau

Doctoral Dissertations

The development of advanced materials and manufacturing techniques for energy storage devices is continuously growing. The research emphasizes micro-engineering, nano-engineering, and advanced materials science, with the goal of enhancing the performance and scalability of manufacturing methods of different materials processing with a view of achieving sustainability. In the micro-engineering domain, novel methods for fabricating thick electrodes with short diffusion paths are introduced, enabling higher mass loading and improved battery performance. Additionally, innovative strategies for optimizing the performance of carbon nanofibers (CNFs) as anode materials in LIBs are explored in the nano-engineering domain. These studies address key challenges such as inter-bonding …

Computational Design Of Complex Concentrated Alloys, Hamid Sharifi

Doctoral Dissertations

A high-throughput parameterization of modified embedded atom model (MEAM) interatomic potentials for combinations of Cu, Ti, Ni, Cr, Co, Al, Fe, and Mn was carried out using a genetic algorithm. Unary systems were parameterized based on DFT calculations and experimental results. MEAM potentials for 28 binary and 56 ternary combinations of the elements were parameterized to DFT results that were carried out with semi-automated frameworks. Specific attention was made to reproduce properties that impact compositional segregation, material strength, and mechanics. Utilizing the MEAM interatomic potentials and a Monte Carlo scheme, phase segregation in the CrNiCo, CuNiCr and CuNiCo fcc alloys …

Impact Of Student Beliefs And Self-Efficacy On Performance In Higher Education Stem Courses, Lauren Nicole Fogg

Doctoral Dissertations

In engineering education, students often face feelings of inadequacy, leading to academic struggles and potential dropout. This dissertation investigates the impact of interactive course materials on students' confidence and self-efficacy in problem-solving, focusing on an Engineering Materials class at Louisiana Tech University. Over four quarters, involving seven sections and 218 students, a 13-question Likert scale survey was administered repeatedly, alongside demographic data and textbook usage surveys. The study aims to compare students’ attitudes and beliefs when not using a textbook versus when using an interactive web-native book. Hypotheses suggest that the interactive book will enhance problem-solving beliefs, confidence, and grades. …

Advanced Manufacturing Of Nanomaterials For Energy Storage And Biomedical Applications, Hiep Pham

Doctoral Dissertations

"Nanomaterials have emerged as an important component to the advancement of many fields, ranging from advanced energy materials in the energy field to highly sophisticated treatment vehicles in the biomedical field. Understanding the physical behavior of nanomaterials is critical to design materials with excellent properties and performance for the many disciplines in which they are utilized and is necessary to master the various manufacturing processes that influence nanomaterial properties and behavior. This research focused on a fundamental study into the behaviors of newly developed nanomaterials under both conventional and new manufacturing processes for high performance lithium-ion batteries and for advanced …

Melt Pool Feature Extraction, A State-Space Model And Spatial Layer-To-Layer Control For Powder Bed Fusion, Xin Wang

Doctoral Dissertations

"Powder Bed Fusion (PBF) is an Additive Manufacturing (AM) technique which can reduce material waste and is a fast-prototyping technique for complex geometries. However, the lack of consistent quality is a major problem in industrial applications. An InfraRed (IR) camera is a common tool to monitor a surface temperature field and melt pool morphology in PBF. With melt pool features from camera videos, manufacturing researchers use spatial feature maps to visualize defect locations and control researchers use layer-to-layer control to achieve more uniform melt pools and less defects.

Paper I presents a simulation method to characterize the effect of down-sampling …

Material Models For Simulation Of Steel Hot Rolling Process Using Experimentally Determined Properties At Elevated Temperatures And Strain Rates, Siva Sai Krishna Dasari

Doctoral Dissertations

"Hot rolling is one of the most important and complex process that includes large material deformation, different contact conditions, complex geometries and different temperature gradients along with micro structural changes such as viscoplasticity, dynamic recrystallization, and static softening. In the present work, the viscoplasticity, damage evolution, static softening and void closure of alloyed metal during hot rolling process was numerically investigated. Gleeble^TM hot compression and double hit tests were performed to provide experimental stress-strain curves at recrystallization temperatures and at different strain rates. Johnson-Cook viscoplastic model was calibrated using experimental stress-strain curves. Static softening model was developed at varying …

Additive Manufacturing Of Steel And Aluminum Structures: Modeling And Experiments, Manoj Kumar Reddy Rangapuram

Doctoral Dissertations

"Additive manufacturing (AM) is defined as the process of joining materials to make objects from three-dimensional model data. Complex geometries can be easily manufactured compared to conventional subtractive methods with more freedom and flexibility in the design process. As the demand for AM process increased, it has become critical to understand the process and various parameters that constitute in affecting the quality of the manufactured part. Conducting experiments can be time intensive and costly to optimize a process. Modeling can be used as an aid to optimize, examine, and predict the process outcome.

The objective of this study is (i) …

Methodology For Parameter Determination For Simulation Software, Aaron Flood

Doctoral Dissertations

"This research aims to present a methodology for optimizing input datasets to increase the accuracy of mathematical models and accelerate their application to engineering problems. To accomplish this goal, this work focused on the application of mathematical models to metal additive manufacturing (AM), specifically the thermal history of laser directed energy deposition (DED) of aluminum alloys. The initial steps of this body of work were to develop a mathematical model that is capable of simulating the metal AM process and applying it to the laser DED of aluminum. It was validated using the well characterized material Ti-64 and shown to …

Kinetic Modeling And Simulations Of Plasma-Surface-Dust Interactions For Lunar Exploration, David Clifford Lund

Doctoral Dissertations

"Due to the recent relevance of NASA’s focus on lunar missions, a better understanding of the lunar plasma-surface-dust environment is vital for their success. The lunar surface, devoid of an atmosphere and a global magnetic field, is directly exposed to solar radiation and solar wind plasma. This exposure leads to the electrical charging of the lunar surface due to the bombardment of solar wind plasma and the emission/collection of photoelectrons. Therefore, this research developed accurate and efficient computational models of plasma-surface-dust interactions and extend a legacy simulation code, namely the Immersed-Finite-Element Particle-in-Cell (IFE-PIC), to a parallel version: Parallel Immersed-Finite-Element Particle-in-Cell …

In Situ Infrared Thermographic Inspection In Additive Manufacturing, Tao Liu

Doctoral Dissertations

"Laser Powder Bed Fusion (LPBF) is a key technique in metal additive manufacturing and has undergone extensive research over the past few decades. It enables the fabrication of complex geometries directly from digital design models. The solidification process in LPBF is heavily influenced by the characteristics of the powder layer, including its thickness and thermal transport properties. Additionally, the performance of the printed part is impacted by the temperature history during solidification and the final residual stress field. While these topics have been the focus of many studies, almost all research has concentrated on ex-situ measurement and testing. These ex-situ …

Optimizing The Total Life Cycle Of Li-Ion Batteries: From Constant Gradient Charging To Aged Cell Performance Restoration, Kasim Adesegun Adewuyi

Doctoral Dissertations

As demand for Lithium-Ion Batteries (LIBs) have skyrocketed over the past decade, the need for better charging methodologies and recycling methods have become vitally important. At a fundamental level, this dissertation strives to fulfill the green promise of a future without fossil fuels. In order to promote a transition away from fossil fuels, LIBs for vehicles require ultrafast charging times equivalent to a normal vehicle (6 mins). However, this process leads to high volume expansion for next generation electrode materials which causes degradation. Without limiting this factor, the environmental impact shifts from oil rigs to Li mines and landfills. The …

Communication Modality And Activity Recognition In Smart Manufacturing, Haodong Chen

Doctoral Dissertations

"Advancements in sensors, computational intelligence, and big data have been rapidly transforming and revolutionizing the manufacturing sector, leading to robot-rich and digitally connected factories. To facilitate such a transformative process, workforce training and coordination between the human workforce and robots have remained a major challenge. This study aims to create intelligent workforce training systems for human-computer interaction and human-robot collaboration. It proposes the use of dynamic gestures and speech commands for seamless communication between a worker and a robot, leveraging Convolutional Neural Networks (CNN) and multiple threading for recognition and integration. Additionally, a fine-grained activity recognition model has been crafted …

Effect Of Ai–Si Coating Weights On Corrosion And Weldability Of Ultra-High-Strength Steel Usiborr 1500 Used In Automotive Structures, Hilary Anayochukwu Onyishi

Doctoral Dissertations

"There has been increased demand for hot-stamped pre-coated Usibor 1500R in automotive industries due to its excellent properties (ultra-high strength, weight reduction, low spring back and excellent corrosion protection). In this research work, investigation was conducted to better understand the effect of Ai-Si Coating Weights on weldability and corrosion of Ultra-High-Strength Steel Usibor 1500R used in Automotive Structures”. The results show that weld nugget diameter increases with increasing weld current, better spot-weld nugget diameter is recorded at weld currents above 7.5 kA for both AS80 and AS150 and the weld current range decreases as the interdiffusion layer (IDL) thickness increases. …

A Primal Treatise Of Constant-Force Compliant Segment And Mechanism Design With Applications, Vamsi Lodagala

Doctoral Dissertations

"The evolution of compliant mechanisms propelled the development of constant-force mechanisms (CFMs) for various applications because of their unique characteristics. Many research endeavors have presented different techniques that often involve some optimization to design the CFMs. However, the mechanics of the generation of constant force at the elemental level is not well understood. This research effort theorizes and validates that simple, compliant segment with different boundary conditions, subjected to axial loading, produce near-constant force without the need for design optimization. Analytical models are developed based on the pseudo-rigid-body model (PRBM) concept to predict their force-displacement behavior, and to establish that …

Unsteady Flow Behaviors Generated By Three-Dimensional Lattice Geometries As Measured By Laser Doppler Velocimetry, Yi Qiao

Doctoral Dissertations

"The relation between flow stream turbulence and heat transfer has been known for a long time, that the heat transfer rate is increased if the turbulence or fluctuation level of the flow increases. Open cell foams and compact heat exchangers are two of the most common models applied for heat transfer augmentation. However, the small ligaments of open cell foams limit the heat conducted and smooth passages in compact heat exchangers cannot cause flow unsteadiness. Accordingly, new geometric models are needed to improve the heat transfer enhancement. Three-dimensional (3D) lattice geometries with a range of features and sizes can be …

Characterization And Improvement Of Powder Properties Through Plasma Spheroidization For Use In The Laser Powder Bed Fusion Process, M. Hossein Sehhat

Doctoral Dissertations

"This research was conducted to characterize the powder properties using different characterization techniques to enhance the powder behavior in the Laser Powder Bed Fusion (LPBF) process. One of the shortcomings of LPBF process is the high cost of gas-atomized powder feedstock. To overcome this downside, the cheaper water-atomized powder was characterized and used in LPBF process, and its performance was compared with those of gas-atomized powder. Also, the plasma spheroidization process was used to improve the powder characteristics; if the spheroidized powder could function as well as the virgin powder, plasma spheroidization process could be applied to the used powders …

Influences Of The Internal Residual On Combustion Instabilities In The Misfire And Partial Burn Regimes Of A Dilute Spark-Ignition Engine, Rachel Inez Stiffler

Doctoral Dissertations

"Dilution in spark-ignition (SI) engines can improve fuel consumption and reduce emissions; however, increased levels of dilution either from excess oxidizer or exhaust gas recirculation (EGR) causes combustion to become more strained and cycle-to-cycle variations increase. At high levels of dilution incomplete combustion events (i.e. misfires and partial burns) start to occur, which cause combustion instabilities and eventually a dilute limit is reached. It is known the combustion instabilities seen are primarily due to the feed-forward mechanism present in the residual gases, but it is still unknown what about the residual is influencing the dynamics under high levels of dilution …