Mechanical Engineering Commons^™

Grafting Based Thermoplastic-Thermoset Bonding For Aerospace Structures, Saurabh Vaidya

Theses and Dissertations

The use of carbon fiber composites is rapidly increasing in the aerospace industry. Fiber reinforced plastic composites can primarily be classified as thermoplastic and thermoset, both offer unique advantages over one another. Thermosets cure at relatively low temperature and in general, are lower priced than thermoplastic composites. However, the cost of autoclave for the curing of thermosets is a major drawback. On the other hand, thermoplastics are showing higher damage tolerance. They can be re-melted and re-consolidated and have the potential to be re-used / recycled. The repair of TP composites is not developed yet. Therefore, both the types attract …

An Acoustic Emission And Artificial Intelligence Approach To Structural Health Monitoring For Aerospace Application, Joseph Chandler Garrett

Theses and Dissertations

In the area of aerospace and other applications, structural health monitoring (SHM) has been a significant and growing area of research in recent years. Throughout the operational life of aerospace structures, various damage scenarios may manifest, and it is of great concern to the aerospace community to develop methodologies for detecting and assessing these damage scenarios. In this paper, fundamental research on the use of the acoustic emission (AE) approach to SHM for fatigue crack growth is presented. In general, the AE approach to SHM and non-destructive evaluation (NDE) involves the sensing of ultrasonic Lamb waves propagating through a structure. …

Separate Effects Tests For Studying Thermal Gradient Driven Cracking In Uo2 Pellets Undergoing Resistive Heating, Sobhan Patnaik

Theses and Dissertations

A variety of normal operation and accident scenarios can generate thermal stresses large enough to cause cracking in light-water reactor (LWR) fuel pellets. Cracking of fuel pellets can lead to reduced heat removal, larger centerline temperatures, and localized stress in cladding, all of which impact fuel performance. It is important to understand the temperature profile on the pellet before and after cracking to improve cracking models in fuel performance codes such as BISON. However, in reactor observation and measurement of cracking is very challenging owing to the harsh environment and design of fuel rods.

Recently, a state-of-the-art experimental pellet cracking …

Experimental Investigation Of Spray Cooling Integrated With A Modified Vapor Compression Refrigeration System Using Several Refrigerants, Nabeel Mukhlif Abdulrazzaq

Theses and Dissertations

Spray cooling has gained increasing interest over the last three decades due to its high thermal performance as a direct cooling technique. Researchers are investigating spray cooling in thermal management systems for electronic applications, particularly focusing on the use of dielectric fluids including FC-72, FC-87, ammonia, and refrigerants such as R113 and R134a. Their studies indicate that the usage of dielectric fluids as a working fluid in spray cooling systems is promising and has significant thermal performance enhancement, which is suitable for a wide range of electronic applications. However, several deficiencies have been identified with the working fluids studied thus …

Nano-Engineered High-Performance Copper-Water Heat Pipes, Ahmed A. Abdulshaheed

Theses and Dissertations

Recently, heat pipes have gained an exceptional reputation as passive systems. They have become an attractive choice for many engineering applications due to their simple design, high rate of heat transfer, low weight, and low cost of maintenance [1]. A Heat pipe consists of a vacuumed shell filled partially with a compatible working fluid. Three main sections comprise a heat pipe: evaporator, adiabatic, and condenser section. The heat pipe utilizes the principle of evaporation and condensation for operations, i.e., the phase change of working fluid. Heat pipe allows high heat rates to transfer over considerable lengths with minimum temperature differences …

Robust Scandium Aluminum Nitride Mems Resonators For L Band Operation In Orbital Environments, Israel W. Dunk

Theses and Dissertations

This thesis investigates AlN alloyed with scandium in a variety of resonator architectures including WEM, overtone WEM, LEM, and SAW that have the potential to achieve high levels of electrical performance and environmental robustness. SAW resonators operating near 370 MHz are fabricated on polycrystalline Sc_.37Al_.63N, and AlN with the resulting devices compared and conclusions drawn as to the merits of each material. The design and fabrication of SAW devices is discussed in detail, with the operating characteristics of these resonators then tested both electrically and mechanically. Mechanical characterisation includes analysis of vibration and shock effects on …

Discrete Element Modeling Of Hydrogel Extrusion, Rohit Boddu

Theses and Dissertations

Hydrogels are widely used in extrusion bioprinting as bioinks. Understanding how the hydrogel microstructure affects the bioprinting process aids researchers in predicting the behavior of biological components. Current experimental tools are unable to measure internal forces and microstructure variations during the bioprinting process. In this work, discrete element modeling was used to study the internal interactions and the elastic deformation of the molecular chains within hydrogel networks during the extrusion process. Two-dimensional models of hydrogel extrusions were created in Particle Flow Code (PFC; Itasca Co., Minneapolis, MN). For our model's calibration, hydrogel compression testing was used in which a cluster …

Equations Of State For Warm Dense Carbon From Quantum Espresso, Derek J. Schauss

Theses and Dissertations

Warm dense plasma is the matter that exists, roughly, in the range of 10,000 to 10,000,000 Kelvin and has solid-like densities, typically between 0.1 and 10 grams per centimeter. Warm dense fluids like hydrogen, helium, and carbon are believed to make up the interiors of many planets, white dwarfs, and other stars in our universe. The existence of warm dense matter (WDM) on Earth, however, is very rare, as it can only be created with high-energy sources like a nuclear explosion. In such an event, theoretical and computational models that accurately predict the response of certain materials are thus very …

Impact Dynamics Of Surfactant-Laden Droplets On Non-Wettable Coatings, Amir Esmaeili

Theses and Dissertations

Owing to their excellent water repellency, non-wettable (superhydrophobic) coatings have gained tremendous attention in the past couple of decades. Alkyl ketene dimer (AKD), an inexpensive polymer frequently used in paper industry as a sizing agent, has shown potentials to become superhydrophobic. The formation of a porous structure after curing the solidified AKD for an extra-long time (4–6 days) results in superhydrophobicity, i.e., a static contact angle with water of >150° and a roll-off angle of <10°. In this work, a facile and low-cost method was used to turn the surface of AKD superhydrophobic in a very short period of time by briefly treating the coatings, obtained from isothermally heated molten AKD at 40 °C for 3 min, with ethanol. The resulting superhydrophobicity is due to the formation of porous, entangled irregular micro/nano textures that create air cushions on the surface leading to droplet state transition from Wenzel to Cassie. As a proof of concept, the same material was applied to the co-sputtered nickel-tungsten thin films, commonly used in micro/nano-electro-mechanical systems, to improve their hydrophobicity. According to the results, at least 20% increase was observed in the dynamic contact angles of the treated substrates.

In addition, this work presents a detailed high-speed imaging analysis of the influence of the molecular weight, concentration and ionic nature of surfactants on droplet …

Nebulizer-Based Systems To Improve Pharmaceutical Aerosol Delivery To The Lungs, Benjamin M. Spence

Theses and Dissertations

Combining vibrating mesh nebulizers with additional new technologies leads to substantial improvements in pharmaceutical aerosol delivery to the lungs across therapeutic administration methods. In this dissertation, streamlined components, aerosol administration synchronization, and/or Excipient Enhanced Growth (EEG) technologies were utilized to develop and test several novel devices and aerosol delivery systems. The first focus of this work was to improve the poor delivery efficiency, e.g., 3.6% of nominal dose (Dugernier et al. 2017), of aerosolized medication administration to adult human subjects concurrent with high flow nasal cannula (HFNC) therapy, a form of continuous-flow non-invasive ventilation (NIV). The developed Low-Volume Mixer-Heater (LVMH) …

Evaluation Of Regional Extrathoracic Deposition Of Low- And High-Momentum Aerosol Using Anatomically-Correct In Vitro Airway Models, Sana Hosseini

Theses and Dissertations

The popularity of pulmonary aerosol delivery is increasing due to numerous advantages including non-invasiveness, fast onset of action, avoidance of the first-pass metabolism, and relatively good patient compliance. However, aerosol delivery to the site of action within the extrathoracic regions is challenging to quantify from a regulatory perspective due to the combined effects of the device and formulation characteristics, complex morphology of the airways resulting in extreme anatomical variabilities, and user dependent administration methods. Besides the therapeutic aerosol delivery, electronic nicotine delivery systems (ENDS) are a user-driven aerosol technology used to deliver nicotine as one of the electronic liquid (e-liquid) …

Exploring A Platinum Nanocatalytic Microcombustion-Thermoelectric Coupled Device, Dylan Moore Mcnally

Theses and Dissertations

This work aimed to create a first-generation power device for eventual application to portable electronics. A platinum nanoparticle catalytic substrate was employed in a microcombustion-thermoelectric coupled (MTC) device for the purpose of chemical-to-electrical energy conversion. Multiple microcombustion reactors were designed, fabricated, and investigated. Most importantly, the reactor configuration was designed to accommodate thermoelectric generators (TEGs) for power production. Temperature studies with catalytic combustion of methanol-air fuel mixtures were used to evaluate the thermal power generation performance of each reactor. The final reactor design enabled ignition at room temperature with the ability to achieve repeat catalytic cycles upon subsequent exposure to …

A Finite State Automata-Based Description Of Device States For Function Modeling Of Multi-State Technical Devices, Ahmed Mohammed Sobhan Chowdhury

Theses and Dissertations

Many modern and innovative design problems require multi-modal, reconfigurable solutions. Function modeling (FM) is a common tool used to explore solutions in early stages of mechanical engineering design. Currently, function structure representations do not abet the modeling of formally-defined reconfigurable function models as graph-based function models used in early-stage systems design usually represent only one operational mode of the system. Currently there is a need, but no rigorous formalism to model multiple possible modes in the model and logically predict the behavior of the system as it transitions between the modes. Additionally, function modeling representations will benefit from dynamically capturing …

Extreme Response Analysis Of A Site-Specific Offshore Wind Turbine And Offshore Wind Farm Layout Optimization, Xiaosen Xu

Theses and Dissertations

Offshore floating wind turbines have been developed in deep water where bottom-fixed offshore wind turbines are cost-prohibitive. Gulf of Maine has one of the greatest potential wind energy on the east coast. A detailed analysis of metocean data is essential for the dynamic simulation of the floating offshore wind turbine and the offshore wind farm layout optimization. Wave scatter diagram represents the joint probability of significant wave height and peak periods. In the wind energy industry, turbulence intensity is defined as the standard deviation of the horizontal wind speed divided by the average wind speed over certain time period. Uniform …

Mono And Multi-Objective Optimization And Modeling Of Machining Performance In Face Milling Of Ti6al4v Alloy, Al Mazedur Rahman

Theses and Dissertations

Titanium alloys are extensively used in numerous industries like aerospace, automotive, military, etc., due to their exclusive characteristics. But machining these alloys has always been challenging for manufacturers. This research investigates the effect of radial depth of cut on cutting forces, tool life, surface roughness (Ra), and material removal rate (MRR) during face milling of Ti6Al4V alloy. It also aims to perform mono and multi-objective optimization of response characteristics to determine the optimal input parameters, namely cutting speed, feed rate, and radial depth of cut. Taguchi method and analysis of variance (ANOVA) have been used for mono-objective optimization, whereas Taguchi-based …

Optimal Onboard Renewable Energy Charging Method To Improve Micro-Autonomous Underwater Vehicle Deployment Life, Brooklynn Dawn Byford

Theses and Dissertations

This study is an investigation of various methods for recharging a micro autonomous underwater vehicle (μAUV) onboard using renewable energy sources while deployed at sea. The goal of this project is to determine the optimal onboard renewable energy design method to be used to prolong the deployment life of a μAUV. This project specifically targeted vehicles specifications and designs similar to the Riptide Autonomous Solutions’ μAUV[1], which was used for this study. Concluding results are based on the following factors: power generation versus time, structural integrity, and design complexity. The three design method categories investigated are as follows: solar energy, …

The Implementation And Comparison Of Fuzzy Logic Control Systems To Modern Control Methods On Low-Cost Hardware, Cristian A. Barron

Theses and Dissertations

Modern control engineering provides many options to automate systems for which a mathematical model is required. Another control does not rely on the mathematical model of the system and is known as fuzzy logic control. In this study, a literature review is conducted on existing control systems strategies such as proportional integral and derivative (PID), linear quadratic regulator (LQR), and fuzzy logic controller (FLC), the complexity of the systems they control, and their strengths and weaknesses. In addition, a series of experiments are conducted, both through simulations in MATLAB Simulink and using their implementation using the actual physical hardware to …

Optimizing A Railroad Bearing Condition-Monitoring Algorithm For Use With An Onboard Wireless Low-Power Sensor Module, Jonas Regan Leano Cuanang

Theses and Dissertations

An algorithm that utilizes vibration measurements was developed by the UTRGV Center for Railway Safety to monitor the condition of railroad bearings. This algorithm uses the data collected from accelerometers on the bearing adapters to determine if there is a defect, where the defect is within the bearing, and the approximate size of the defect. Laboratory testing was performed on the UTCRS single bearing test rig. A four-second sample window of the recorded vibration data is used by the algorithm to reliably identify the defective component inside the bearing with up to a 100% confidence level. However, considerable computational power …

Effect Of Adding Palm Fiber To Thermal Conductivity Of Quick Set Concrete, Monica Garcia

Theses and Dissertations

As climate change becomes a more dire issue and more readily accepted by those in power, the demand for local and systemic solutions grows louder. In urban environments, one issue of concern is the contribution of anthropogenic heat from buildings which contributes to localized warming of the environment. A method that can reduce anthropogenic heat is decreasing the thermal conductivity of building materials. The objective of this study is to examine the possibility of using palm fibers to reduce the thermal conductivity of quick-set concrete samples. The data gathered in this study are used to determine the thermal conductivity value …

The Design, Fabrication, And Testing Of A Cooling Garment, Richard James Garza

Theses and Dissertations

The aim of this research is to design a device or technology capable of cooling the user – such as a college student walking to class, for example – in a manner as convenient as putting on a jacket. The idea is to use the peltier effect – a phenomenon in which two dissimilar semi-conductors heat up and cool down with the application of an electric current – as the source of heat absorption used to cool the user. In this research it will be determined whether or not it is feasible to use such a phenomenon to keep the …

Assessing The Performance Of Reconditioned Railroad Tapered-Roller Bearings Used In Freight Rail Service, Veronica Valeria Hernandez

Theses and Dissertations

The rail industry currently utilizes two wayside detection systems to monitor the health of freight railcar bearings in service: The Trackside Acoustic Detection System (TADS™) and the wayside Hot-Box Detector (HBD). Bearings that are removed from service are sent to specialized facilities where they undergo a reconditioning process before the bearings can be returned to rail service. The reconditioning process has been used for decades although there has been no previous study on the effectiveness of the reconditioning process on defective bearings that were removed from service. This persuaded the researchers from the University Transportation Center for Railway Safety (UTRCS) …

Electromagnetic Interference Shielding Effectiveness Of Interlayered Systems Containing Metal-Oxide, Conducting Polymer And Carbon Nanotube Reinforced Polymeric Composites, Shaik Merkatur Hakim Marjuban

Theses and Dissertations

The Electromagnetic Interference (EMI) Shielding Effectiveness (SE) has become one of the important requirements for the devices associated with telecommunication systems consisting of large frequency bands. The degradation of the quality of transmitting signal influenced by frequencies emitting from external sources can be reduced by covering the circuits of the devices by EMI Shielding materials like polymer composites, metal-based nanofiber mats, the metal of oxide films, etc. The investigation strives for the attenuation of EMI by introducing two composite mats from conducting polymer-based, multiwalled carbon nanotubes (MWCNTs) coated Nylon 6 nanofiber composites. Two other composite mats are also developed by …

A Modified Peng-Robinson Cubic Equation Of State Based On Bayesian Framework, Wei Chen

Theses and Dissertations

Peng-Robinson cubic equations of state (PR-EoSs) as one of the most popular two-parameter cubic equations of state (2P-EoSs) are widely used to calculate thermodynamic properties of pure substances and their mixtures. However, the prediction accuracy of 2P-EoSs varies significantly among different substances due to its intrinsic limitation. To this end, many modifications have focused on changing the dependence structure of 𝛼 function with temperature for PR-EoS to enhance prediction accuracy. In this paper, we propose a Bayesian framework to calibrate a new 𝛼 function, which is a bias-corrected parametrized model form for the PR-EoS. The developed PR-EoS with the calibrated …

Nonlinear Frequency Tuning Of Pre-Curved Micro-Scale Beams, Mackenzie Rae Robatin

Theses and Dissertations

Micro-electromechanical systems (MEMS) have many common advantages in applications due to their small size and ability to integrate with electronics. For MEMS with vibrating elements, other advantages include their tunable resonant frequencies and the frequency range in which the systems operate. Also, the damping in these devices is often so light that it is nearly negligible, resulting in sharp resonance peaks with good frequency selectivity. Most such devices are designed to operate in their linear range. However, large amplitudes are often desired in order to reduce the relative effects of noise. In such cases, due to mechanical and electrostatic nonlinear …

Optimizing Energy Power Consumption Of Freight Railroad Bearings Using Experimental Data, Carlos Eliasar Lopez Iii

Theses and Dissertations

Throughout the railway industry, trains use systems that record total energy efficiency of a train but not energy efficiency or consumption by components. Monitoring freight bearing power consumption can support the railroad industry efforts to maintain the railroad economic competitiveness and minimize the environmental impact.

For more than a decade now, the University Transportation Center for Railway Safety (UTCRS) at the University of Texas Rio Grande Valley (UTRGV) has been collecting power consumption data for railroad bearings under various loads, speeds, ambient temperatures, bearing condition, and bearing classes. Specifically, data such as temperatures, voltages, speed, and load were collected to …

Water-Soluble Polymers With Ceramic/Metal Nanoparticles For Use As Anode Materials In Lithium-Ion And Sodium-Ion Batteries, Roberto Orrostieta Chavez

Theses and Dissertations

Aqueous solutions of poly(vinylpyrrolidone) (PVP) with 20, 25, and 28 wt.% concentrations were successfully spun into fibers by centrifugal spinning. The pristine PVP fibers were annealed and carbonized to produce flexible carbon fibers for use as binder-free anodes in lithium-ion and sodium-ion batteries. These flexible carbon fibers were prepared by developing a novel three-step heat treatment to reduce the residual stresses in the pristine PVP precursor fibers and to prevent fiber degradation during carbonization. The average diameters of the pristine, annealed, and carbonized fibers were obtained using scanning electron microscopy (SEM), which showed that the average diameter of the carbon …

The Optimization Of Efficiency And Infrastructure For Modern Potable Water Treatment Plants, Brent A. Dekock

Theses and Dissertations

The USDOE Industrial Assessment Centers (IACs) is a program that is designed to help small and medium-sized manufacturing facilities reduce their overall costs and improve energy efficiency. This includes improving potable water treatment plants which supply water throughout the country. This thesis covers the process of how IAC branches and water treatment facilities generally operate, as well as several assessment recommendations that have been developed by a branch of the IAC for several water treatment plants based in the Rio Grande Valley of Texas. The steps of the assessment and water treatment process are described, and several cost saving measures …

Finite Element Method For Assessment Of Air Cushion Skirt Performance, Thomas Arthur Lipscomb

Theses and Dissertations

The objective of this thesis is to create a method of simulating the performance of new materials for use in air cushion vehicle skirts. These systems currently exhibit unacceptable design lifetimes to be considered for widespread adoption, except in specific applications such a military or rapid transport, where high cost is not an obstacle. This project also focuses on using a new high strain to failure resin system that has recently been developed, in combination with high performance reinforcing fibers, to increase the lifespan of the skirt systems. Using industry-standard finite element modelling (FEM) software, a 3d model of the …

Development Of Nirs Based Noninvasive Cerebrovascular Regulation Assessment, Stephanie Marie Miller

Theses and Dissertations

Alterations to cerebral blood flow (CBF) have been implicated in diverse neurological conditions, including mild traumatic brain injury, microgravity induced intracranial pressure (ICP) and intraocular pressure (IOP) increases, and mild cognitive impairment. Near infrared spectroscopy (NIRS)-measured regional cerebral tissue oxygen saturation (rSO2) provides an estimate of oxygenation of the interrogated cerebral volume that is useful in identifying trends and changes in oxygen supply to cerebral tissue and has been used to monitor cerebrovascular function during surgery and ventilation. In this study, CO2-inhalation-based hypercapnic breathing challenges were used as a tool to simulate CBF dysregulation, and NIRS was used to monitor …

An Empirical Investigation Of The Dimensions Of Product Similarity Used In Design By Analogy Of Electromechanical Products, Arnold Nkoane Tsoka

Theses and Dissertations

Analogical reasoning is known to be a core cognitive mechanism behind creative human tasks including the creativity in engineering design. Research shows that during product ideation, designers use analogy to transfer information from prior designs stored in their memory (the source of the analogy) to the task in hand (target of analogy). However, similar to any search process, the source product must be first identified as a potential candidate for analogy before this information transfer can take place. Two products can be similar along multiple dimensions such as their form, function, etc. The dimensions of similarity between two products that …