Mechanical Engineering Commons^™

Characterization Of High Cycle Fatigue And Laser-Aided Machining And Polishing Of Additively Manufactured Materials, Mohammad Masud Parvez

Doctoral Dissertations

“Additive manufacturing (AM) and laser-aided machining and polishing (LAMP) of materials are emerging manufacturing processes both for research and industrial sectors. The AM process can manufacture near-net-shape parts with complex geometries. Meanwhile, the LAMP process integrated with an AM system offers a high processing rate, minimum heat-affected zone, and easily adjustable process parameters during machining and polishing. In mechanical properties characterization of AM metals and alloys, fatigue is a vitally important test method to understand the behavior of materials in cycling loading and unloading circumstances since most mechanical failures of structures are due to fatigue. To characterize AM metal fatigue …

Determining Thermal Properties Via Parameter Estimation Of A One-Dimensional, Analytical Model, Lauren B. Tomanek

Doctoral Dissertations

“In thermal applications, thermal conductivity is used to predict how well a material conducts heat. The accuracy of the magnitude of the thermal conductivity becomes increasingly essential to optimize part geometry. Thermal conductivity can vary significantly from the nominal value due to post-processing. The ASTM standards available to measure thermal conductivity are challenging to reproduce because of the insulated and prescribed temperature boundary conditions that are needed. The research introduces two new methods for estimating thermal conductivity that deliver the same accuracy as the existing ASTM standards and are easier to implement. The methods account for losses in the heating …

Advances In Control Of Uncertain Dynamical Systems With Optimal And Adaptive Approaches, Meryem Deniz

Doctoral Dissertations

"This research starts with designing optimal control for uncertain systems, adding the adaptive control input to suppress the uncertainty. It then follows with designing the optimal control for state constraint, designing the optimal nonlinear reference model, designing adaptive control to handle state constraint and uncertainty. Finally, it designs the finite-time controller for uncertain multiagent systems.

It is well known that the design of the control algorithm for an uncertain dynamical system is not trivial. Motivated by this standpoint, this study focuses on optimal and adaptive control approaches with stability and performance guarantees for uncertain sole and multiagent dynamical systems. From …

Development Of An Interactive Robot For Overground Physical Human-Robot Interaction, Sambad Regmi

Doctoral Dissertations

"The overground interactive robots are potentially beneficial for humans in various areas, such as overground rehabilitation therapies and robotic interactive assistance. However, it is unclear what the expectations and challenges are for a robot to be physically interactive with a human during overground tasks, such as a robot helping an older adult walk. To develop such a robot, one must first build a clear understanding of how the human motor intent is communicated when interacting with another agent. Specifically, how do humans understand the leader’s intention when being led?

Based on previous works, we hypothesized that humans modulate their arm …

Sustainable Face Milling Of Inconel 718 Using Mql And Nanofluids Mql With Vegetable Oil As Base Fluid, Theodore Obumselu Nwoguh

Doctoral Dissertations

"Extreme heat and friction are generated in machining difficult-to-cut metals used in aerospace and nuclear industries leading to poor machinability (high cutting forces, rapid tool wear, shorter tool life, and poor surface integrity). Conventional flood coolant (CEC) used in industry is environmentally unfriendly, hazardous to operators, and unsustainable. These problems motivated this research, which can be mitigated with the use of effective biodegradable cutting fluids, appropriate cutting conditions, and lubrication/cooling strategies. This research provides a sustainable and environmentally friendly replacement to CEC. Firstly, the research characterized three vegetable oils (High Oleic Soybean Oil (HOSO), Low Oleic Soybean Oil (LOSO), and …

Processing And Characterization Of Tini-Based Alloys Fabricated By Laser Aided Manufacturing, Yitao Chen

Doctoral Dissertations

"Laser powder-based directed energy deposition (DED) is a major laser aided additive manufacturing (AM) process for metals. It applies laser energy to deposit metal powders to form 3D metal parts. Apart from manufacturing traditional alloys, DED can also be used to develop advanced alloys with the novel idea of elemental powder mixture feedstock. TiNi-based alloy is a type of shape memory alloy (SMA), a smart material with unique shape memory effects. Using laser powder DED to synthesize TiNi-based SMAs from elemental powder mixture can create more possibilities in new compositions and properties. It can also overcome the limitations of conventional …

Mobility Analysis And Topology Synthesis Of Compliant Mechanism Using Compliance Number And Pseudo-Rigid-Body Model (Prbm), Pratheek Bagivalu Prasanna

Doctoral Dissertations

"Establishing and understanding the kinematic properties of a compliant mechanism has been a relatively recent endeavor and has proved to be a challenging task. A concept of compliance number was offered earlier; the development of terminologies was emphasized that aided in its determination. It also hypothesized that the compliance number (C) and stored strain energy, or mode shapes, are strongly correlated. This compliance number (C) concept is revisited, and a more lucid interpretation of its significance is provided. A fundamental understanding of the concept of deformation mode shapes in compliant mechanisms is formalized using two distinct categories: (i) segmental and …

Investigation Of Control Parameters, Strategies, And Transport Modeling For Effective Electrokinetic Nanoparticle Treatment Of Cementitious Materials, Huayuan Zhong

Doctoral Dissertations

Various deleterious chemical species (including sulfates, chlorides, and others) contaminate concrete structures which are inherently porous and thus suffer from compromised durability. Several technologies have been developed for repairing concrete or enhancing the service life. Nevertheless, their efficiency, practicability, and cost can vary widely. Compared with chemical grout, fiber wrap, and traditional repair technology, electrokinetic nanoparticle treatment (EN) has been found to provide remarkable benefits for strength restoration and mitigation of durability problems via porosity reduction. Nanoparticle instability and over dosage issues can arise and lead to problems during treatments. In many cases, these treatment processes have been accompanied by …

Lateral Torsional Buckling Resistance Of Continuous Steel Stringers In Existing Bridges, Dinesha Malky Kuruppuarachchi Kuruppuarachchi Appuhamilage Don

Doctoral Dissertations

Some of the Louisiana’s bridges built in the 1950s and 1960s used two-girder or truss systems, in which floorbeams are carried by main members and the continuous (spliced) stringers are supported by the floorbeams. The main members are either two edge (fascia) girders or trusses. When the flexural capacity of continuous stringers is calculated, the moment gradient factor (Cb) is not accurately calculated considering the lateral torsional buckling (LTB) at the negative moment section. In particular, the bracing effect of the non-composite concrete deck is not accounted for, and as a result, the current practice has underestimated the LTB strength …

Layer-To-Layer Feedback Control For Direct Energy Deposition Additive Manufacturing, Michelle Gegel

Doctoral Dissertations

"Additive manufacturing (AM) has garnered much attention in recent years, some calling it the fourth industrial revolution. It was first used to create rapid prototypes, although recent efforts have been made to advance the technology towards production of functional parts. This requires advancement in the materials used in AM, as well as the ability to produce quality parts repeatably. More specifically, direct energy deposition (DED) of metal powders is a process capable of producing and repairing parts with complex geometries; however, it is not widely used in industry due to challenges with quality control. In this process, metal powder is …

Experimental Characterization And Crystal Plasticity Modeling Of Mechanical Properties And Microstructure Evolution Of Additively Manufactured Inconel 718 Superalloy, Saeede Ghorbanpour

Doctoral Dissertations

In this thesis, the mechanical behavior of the additively manufactured (AM) IN718 nickel-based superalloy and their correlations with the evolution of microstructure are studied comprehensively. The effects of manufacturing parameters, build orientations, and post processing procedures, i.e. standard heat treatment and hot isostatic pressing (HIP), on various mechanical properties including monotonic compression and tension strength, low cyclic fatigue performance, high cyclic fatigue behaviour, and fatigue crack growth behavior are investigated. Due to the high temperature applications of the IN718 alloy, elevated temperature properties are examined as well. Electron Backscattered Diffraction (EBSD) technique is employed to measure the initial and deformed …

Identification Of Neuromarkers Using Structural And Functional Neuroimaging, Sreevalsan Sanathanan Menon

Doctoral Dissertations

"One of the grand challenges in science is understanding the human brain. Recent advances in magnetic resonance imaging have opened unmatched opportunities to demystify neural circuitry. In this research, the spatially and temporally complex neuroimaging data were used to identify neuromarkers that aids in quantifying a brain’s health. In the first part, a comparison of static and dynamic functional connectivities was made to study their efficacies in identifying intrinsic individual connectivity patterns. Results show that the intrinsic individual connectivity pattern can be used as a ‘fingerprint’ to distinguish among and identify subjects and their biological sex and is more accurately …

Theoretical Study Of Magnetic Particles In A Shear Flow Subjected To A Uniform Magnetic Field, Christopher A. Sobecki

Doctoral Dissertations

"Magnetic manipulation of non-spherical magnetic microparticles is important for applications in shape-based and magnetic-based separations such as waste management, disease diagnostics, drug delivery, and mining. Manipulations of magnetic microparticles also include chain formation to assemble compositions for electronics, drug loading designs, and magnetorheological fluids for smart armor, hydraulic brakes, and dampers. In microfluidic devices, separation-formation-effectiveness depends on the shape of the channel, the shear rate, and the magnetic field strength and direction.

Particle separation and chain formation involved highly complex and computational expense-demanding studies in microfluidic devices, magnetic fields, and particle- particle/wall interactions. This research took complex experimental studies and …

Computational Intelligent Impact Force Modeling And Monitoring In Hislo Conditions For Maximizing Surface Mining Efficiency, Safety, And Health, Danish Ali

Doctoral Dissertations

"Shovel-truck systems are the most widely employed excavation and material handling systems for surface mining operations. During this process, a high-impact shovel loading operation (HISLO) produces large forces that cause extreme whole body vibrations (WBV) that can severely affect the safety and health of haul truck operators. Previously developed solutions have failed to produce satisfactory results as the vibrations at the truck operator seat still exceed the “Extremely Uncomfortable Limits”. This study was a novel effort in developing deep learning-based solution to the HISLO problem.

This research study developed a rigorous mathematical model and a 3D virtual simulation model to …

Fabrication, Characterization Of High-Entropy Alloys And Deep Learning-Based Inspection In Metal Additive Manufacturing, Wenyuan Cui

Doctoral Dissertations

"Alloying has been used to confer desirable properties to materials. It typically involves the addition of small amounts of secondary elements to a primary element. In the past decade, however, a new alloying strategy that involves the combination of multiple principal elements in high concentrations to create new materials called high- entropy alloys (HEAs) has been in vogue. In the first part, the investigation focused on the fabrication process and property assessment of the additive manufactured HEA to broaden its engineering applications. Additive manufacturing (AM) is based on manufacturing philosophy through the layer-by-layer method and accomplish the near net-shaped components …

Thermomechanical Simulation And Process Optimization For Hot Rolling Of Steel, Shouvik Ganguly

Doctoral Dissertations

"Hot rolling is a manufacturing process that involves large material deformation, complicated geometries, contact conditions and non-uniform temperature gradients. Steel industries are motivated to prevent hot rolled steel products to be defect free and with desired shape and size. In order to simulate the process accurately, it is essential that the material model for steel accounts for the viscoplasticity and changes in properties that occur in steel at elevated temperatures as grain growth and recrystallization.

The healing of existing voids during hot rolling was investigated using finite element simulations. Voids are highly undesirable as they not only degrade the product …

Fabrication Of 304l Stainless Steel And Aluminum Parts By Laser Foil Printing And Process Automation, Chia-Hung Hung

Doctoral Dissertations

"This work presents research conducted on a novel metal additive manufacturing process, called Laser Foil Printing (LFP), to fabricate metal parts with various geometries layer by layer using metal foil as the feedstock. To investigate the processability and characteristics of LFP for fabricating metal parts, the materials included 304L stainless steel and Al-1100 aluminum alloy. The LFP process parameter windows for both 304L and Al-1100 were determined, and the optimal process parameters with stable formation of the melt pools were selected to fabricate dense metal parts. The microstructure and properties of LFP-fabricated parts were characterized and analyzed using tensile testing, …

Numerical And Experimental Study Of Mechanical Properties For Laser Metal Deposition (Lmd) Process Part, Lan Li

Doctoral Dissertations

"Laser Metal Deposition (LMD), also called as, Laser Engineered Net Shaping (LENS), Directed Energy Deposition (DED), is a typical Additive Manufacturing (AM) technology, is used for advanced free-form fabrication. It creates parts by directly melting materials and depositing them on the workpiece layer by layer. In this process, the metal powder or fiber is melted within the melting pool by laser beam or electron beam and quickly solidifies to the deposited layer. LMD technology shows great advantages over traditional manufacturing on complex structure fabrication, including high building rates, easy material replacement and reduced material waste. These merits make the wide …

Dynamic Behavior And Interactions Of Ferrofluid Droplets Under Magnetic Fields In Low Reynolds Number Flows, Md Rifat Hassan

Doctoral Dissertations

Digital microfluidics in combination with emulsion microfluidics are crucial building blocks of droplet-based microfluidics, which are prevalent in a wide variety of industrial and biomedical applications, including polymer processing, food production, drug delivery, inkjet printing, and cell-based assays. Therefore, understanding the dynamics and interactions of droplets as well as the interactions between the droplets and solid surfaces are of great importance in order to improve the performance or product in these applications.

Recently, several studies in the literature have demonstrated the potential of magnetic fields in controlling the behavior of droplets in microscale; however, the fundamental mechanism behind the interesting …

An Investigation Of Unsteady Thermal Exchange Processes In Geothermal Heat Exchangers, Ganesh Ravi Shanker

Doctoral Dissertations

“Geothermal heat exchangers, has become one of the highly recognized non conventional heat exchangers as they utilize renewable energy source earth to initiate the thermal energy transfer. However, these heat exchangers suffer from a expensive installation cost due to their conservative design model, thereby facilitating the need to identify and improve the design. In this dissertation, three gaps, which identifies improvement over conservative design were investigated, to assess the heat exchanger performance. In the first approach, borehole thermal and geometrical properties were investigated keeping the outlet leg of the heat exchanger as adiabatic, which neglects the thermal short-circuiting between the …

Development Of In-Situ Radiometric Inspection Methods For Quality Assurance In Laser Powder Bed Fusion, Cody S. Lough

Doctoral Dissertations

“Laser Powder Bed Fusion (LPBF) metal Additive Manufacturing (AM) fabricates 3D metal parts layer-by-layer. The process enables production of geometrically complex parts that are difficult to inspect with traditional methods. The LPBF parts experience significant geometry driven thermal variations during manufacturing. This creates microstructure and mechanical property inhomogeneities and can stochastically cause defects. Mission critical applications require part qualification by measuring the defects non-destructively. The layer-to-layer nature of LPBF permits non-intrusive measurement of radiometric signals for a part’s entire volume. These measurements provide thermal features that correlate with the local part health. This research establishes Optical Emission Spectroscopy (OES) and …

Additively Manufactured Metallic Cellular Structures, Okanmisope Aziel Fashanu

Doctoral Dissertations

"Cellular structures are lightweight structures with excellent mechanical, thermal, and acoustic properties. They offer promise in a series of applications, including lightweight applications, sandwich cores, mechanical damping, acoustic absorption, strain isolation, and thermal management. The manufacturing of these complex cellular structures is expensive and time-consuming, which hinders the adoption of these structures in many industries. Advancement in manufacturing technologies, such as additive manufacturing (AM), however, have changed this. AM allows for the rapid and less expensive manufacturing of complex cellular structures. This work aimed to investigate the performance of additively manufactured cellular structures for lightweight and sandwich core applications. In …

Advanced Battery Modeling For Interfacial Phenomena And Optimal Charging, Yaqi Zhu

Doctoral Dissertations

"Lithium-ion batteries are one of the most promising energy storage systems for portable devices, transportation, and renewable grids. To meet the increasing requirements of these applications, higher energy density and areal capacity, long cycle life, fast charging rate and enhanced safety for lithium-ion battery (LIBs) are urgently needed. To solve these challenges, the relevant physics at different length scale need to be understood. However, experimental study is time consuming and limited in small scale’s study. Modeling techniques provide us powerful tools to get a deep understanding of the relevant physics and find optimal solutions. This work focuses on studying the …

Prediction Of Battery Health Dynamics, Damola Martins Ajiboye

Doctoral Dissertations

"The successful market penetration of lithium-ion batteries in the last 30 years has ushered in a new dawn in energy applications. Notwithstanding their widespread use, lithium-ion batteries are affected by a plethora of fundamental issues — safety, cycle life, performance, and cost. In this work, advanced modeling techniques are developed to tackle some of these issues. This dissertation is subdivided into four parts, the first is introduction while the remaining are dedicated to the development of computational techniques for predicting battery health dynamics.

In the second part of this work, we developed fast and accurate algorithms for modeling essential battery …

Sources Of Quality Uncertainty In Laser Powder Bed Fusion Metal Additive Manufacturing, Zachary Young

Doctoral Dissertations

"Powder based additive manufacturing (AM) exhibits tremendous uncertainties, where variations in build quality is present despite utilizing similar build processing parameters. First, this work reports the features and formation mechanisms of five unique types of spatter during the LPBF process by in-situ high-speed, high-energy x-ray imaging. The unique physical characteristics of spatter are determined. The effect of laser scan speed and laser power on spatter formation, ejection, and mitigation are determined. Second, this work addresses the uncertainty challenge by identifying the sources of uncertainty in SLM by in-situ characterization due to variations from the additive manufacturing processing parameters needed for …

Novel Piezo Actuators For Surface Cleaning, Yezad H. Anklesaria

Doctoral Dissertations

"Optical cameras are becoming increasingly common and are used in a variety of applications. With recent progress and transition toward more autonomous systems, the usage of optical systems will be common and widespread. Applications of the optical systems range from autonomous vehicles, home security systems, aviation, extraterrestrial vehicles, spacecraft, and satellites. Imaging systems are used in decision-making in many of these applications. Fouling of the field of view of the imaging system can impede the decision process. An active autonomous cleaning method for the optical surface of the optical systems reliably would be advantageous. The research work focuses on developing …

Time- And Space-Dependent Uncertainty Analysis And Its Application In Lunar Plasma Environment Modeling, Xinpeng Wei

Doctoral Dissertations

”During an engineering system design, engineers usually encounter uncertainties that ubiquitously exist, such as material properties, dimensions of components, and random loads. Some of these parameters do not change with time or space and hence are time- and space-independent. However, in many engineering applications, the more general time- and space-dependent uncertainty is frequently encountered. Consequently, the system exhibits random time- and space-dependent behaviors, which may result in a higher probability of failure, lower average lifetime, and/or worse robustness. Therefore, it is critical to quantify uncertainty and predict how the system behaves under time- and space- dependent uncertainty. The objective of …

A Framework For A Successful Additive Repair System, Todd E. Sparks

Doctoral Dissertations

“The goal of this research is to generate a revolutionary improvement to the usability and usefulness of additive repair technology by integrating a set of tools into a seamless work flow. Insufficient automation in the current repair process is a huge hurdle in achieving cost-effective, reliable repairs. Many opportunities have been missed due to inconsistency, quality issues and lack of robustness and flexibility. The present work addresses deficiencies in preparatory steps such as 2D and 3D geometry processing, parameter estimation, and path planning as well as on-machine execution of the path plan. The bulk of the effort is focused on …

Human Behavior Understanding For Worker-Centered Intelligent Manufacturing, Wenjin Tao

Doctoral Dissertations

“In a worker-centered intelligent manufacturing system, sensing and understanding of the worker’s behavior are the primary tasks, which are essential for automatic performance evaluation & optimization, intelligent training & assistance, and human-robot collaboration. In this study, a worker-centered training & assistant system is proposed for intelligent manufacturing, which is featured with self-awareness and active-guidance. To understand the hand behavior, a method is proposed for complex hand gesture recognition using Convolutional Neural Networks (CNN) with multiview augmentation and inference fusion, from depth images captured by Microsoft Kinect. To sense and understand the worker in a more comprehensive way, a multi-modal approach …

Magnetic Control Of Transport Of Particles And Droplets In Low Reynolds Number Shear Flows, Jie Zhang

Doctoral Dissertations

“Magnetic particles and droplets have been used in a wide range applications including biomedicine, biological analysis and chemical reaction. The manipulation of magnetic microparticles or microdroplets in microscale fluid environments is one of the most critical processes in the systems and platforms based on microfluidic technology. The conventional methods are based on magnetic forces to manipulate magnetic particles or droplets in a viscous fluid.

In contrast to conventional magnetic separation method, several recent experimental and theoretical studies have demonstrated a different way to manipulate magnetic non-spherical particles by using a uniform magnetic field in the microchannel. However, the fundamental mechanism …