Mechanical Engineering Commons^™

Surrogate Model-Based Design Optimization Of A Mobile Deployable Structure For Overpressure Load And Vehicular Impact Mitigation, Daniela F. Tellkamp

Theses and Dissertations

Artificial Neural Network (ANN) ensemble and Response Surface Method (RSM) surrogate models were generated from Finite Element (FE) simulations to predict the overpressure load and vehicle impact response of a novel rapidly deployable protective structure. A Non-dominated Sorting Genetic Algorithm-II (NSGA-II) was used in conjunction with the surrogate models to determine structure topology input variable configurations which were suited to produce the optimal balance of minimum mass, minimum rotation angle, minimum displacement, and maximum total length of the deployable structure. The structure was designed to retract into a container, be lightweight to facilitate transportation, and be able to adapt to …

Framework For The Utilization Of The Agile Methodology In Engineering Consulting Services, Cristian Daniel Nuñez

Theses and Dissertations

The guidelines that form the Agile methodology framework are developed and adapted to the engineering consulting services industry. Four tools recommended by the literature are developed and adapted for the specific case of this industry. The implementation of the use of these tools is intended to help adopt the Agile methodology more effectively. A company that performs consulting services for airports is taken as a case study. This company did not officially implement the Agile methodology at the time this research has been done. The data is obtained through a survey designed to associate the company's activities with the guides …

The Deflection And Heat Transfer Analysis Of Injection Mold Cavity With Sla Cooling Channel Insert, Olumide Temidayo Aladesiun

Theses and Dissertations

Fast cooling in injection molding is the critical in the process economy. Among many different cooling channel designs available, conformal cooling offers the best and the most efficient cooling. However, limited awareness, accessibility, complexity, cost, knowledge, and experience limit the use of conformal cooling channels to be used into the mold in a molding process.

Typically, SLM(Selective Laser Melting) method is used to create cavity inserts with conformal cooling channels, however, due to the difficulties listed above, applications of conformal cooling channels are very limited. For an inexpensive alternative SLA (Stereolithography Apparatus) can print cavity inserts with conformal cooling channels. …

Fabrication And Characterization Of Force Spun Polymeric Nanofiber For Drug Delivery And Tissue Engineering Applications, Salahuddin Ahmed

Theses and Dissertations

This study focuses on the development and characterization of polymeric nanofiber for drug delivery and tissue engineering applications. In this study, poly(lactic-co-glycolic) acid (PLGA), Poly-vinyl alcohol (PVA), and Pullulan(PL) were used as the base polymers to develop the nanofiber. Bioactive components Oleanolic acid(OA), Oxymatrine(OM), and Salvianolic Acid(SA) were incorporated in PLGA, PVA, and PL, respectively, via solution mixing. The nano fiber systems were developed using the Forcespinning® method. Morphological, thermo-physical, and biological properties of the fiber mats were analyzed. The composite fiber system containing OA showed a very high drug loading efficiency. The composite fiber system containing high concentration of …

Fabrication Of Solar Absorber Tube With Internal Fin Structure With In718 And Effect Of Boron With In718 For Solar Absorber Tube Using Selective Laser Melting 3d Printing Technology, Naznin Nuria Afrin

Theses and Dissertations

This research aimed to fabricate Solar Absorber Tubes for Solar-Thermal Power Plant with internal fin structures using Selective Laser Melting (SLM) technology. In this study, we investigated the effect of B with IN718 in 3D printing using SLM for solar absorber tubes. The objective was to study the material-process-properties relationship with goal to identify and validate the optimal parameters for the SLM process. Material selected for this study was IN718 with 0.5% and 1% B particle mixed using a V-shape mixing machine. The flowability test was conducted using the Angle of Repose (AOR) method. 3D printed samples …

A Numerical Simulation Of The Powder Bed Additive Manufacturing Process With Molecular Dynamics Simulation, Yeasir Mohammad Akib

Theses and Dissertations

Many manufacturing industries utilize powder bed fusion (PBF) since it can produce microscale precision 3D parts. During PBF, powder particles are selectively fused layer by layer using thermal energy. The build quality in the PBF process relies heavily on powder bed properties and thermal energy deposition. Powder flowability, spreadability, and packing fraction are some of the insightful factors that determine the quality of the powder bed. In this study, a two-dimensional powder bed is developed using the LAMMPS package. A cloud-based pouring of powders with varying volumes and initialization is adopted for the work. A blade-type and circular recoater is …

Ultrafast Laser Direct Writing Of Conductive Patterns On Modified Polyimide Film For Flexible Electronic Applications, Ishrat Jahan Biswas

Theses and Dissertations

Conductive patterns can be printed on a flexible polymer substrate using the direct laser writing (DLW) method. In order to write conductive circuits in such polymer using a laser, polyimide (PI) is a desirable material choice due to its electrical, chemical, and mechanical properties. Electrically non-conductive PI has shown great potential for flexible printed electronics as LDW enables selective carbonization in the bulk of such material leading to the formation of conductive lines. The technique is shown to be a rapid and minimal cost method for printing electrodes to nanoscale devices. However, investigations in this field show several limitations to …

A Study Of The Surface Properties Of Additive Manufactured Inconel 718 After Laser Surface Treatment And Cnc Grinding, Sampson K. Canacoo

Theses and Dissertations

This study investigated the surface properties of additive manufactured Inconel 718 produced through selective laser melting, and the effects of laser ablation and CNC grinding on the surface finish. The objectives were to investigate the effects of the various parameters of laser ablation and CNC grinding on the Inconel 718 surface. The parameters used for the laser experiments were pulse energy (4, 20, and 30 µJ), scanning speed (5, 10, and 15 mm/s), and hatch distance (10, 30, and 50 µm). For the grinding experiments, the wheel speed was kept constant at 20.3 m/sec, however, two different workpiece speed (8.6 …

Development Of Vegetable Oil-Based Nano-Lubricants Using Ag, H-Bn And Mgo Nanoparticles As Lubricant Additives, Kollol Sarker Jogesh

Theses and Dissertations

Because of the harmful impact of petroleum-based lubricant on the environment and human body, vegetable oil-based lubricant with eco-friendly nanoparticles has a great potential to be an alternative lubricant if it possesses proper lubricating properties. In this study, thermal conductivity, viscosity and tribological properties (wear scar diameter and coefficient of friction) of vegetable oil-based nanolubricant, developed from soybean oil and sunflower oil, modified with Ag, h-BN and MgO nanoparticles as lubricant additives, were evaluated. For thermal conductivity evaluation, a line heat source method was used with KD2 Pro-Thermal Property Analyzer. For viscosity evaluation, Haake Mars 40-rheometer was used to evaluate …

Investigation Of Process Parameters To Fabricate Refractory Medium-Entropy Alloy By Selective Laser Melting Process, Abdullah Al Masum Jabir

Theses and Dissertations

This thesis proposal investigates the synthesis of TiWMo refractory medium entropy alloy (RMEA) by selective laser melting process from elemental powder. Steel, titanium and tungsten substrates were used to study the impact on the formation of TiWMo RMEA. Different process parameters were applied to investigate the effects on melting, diffusion and formation of RMEA. The microstructure of TiWMo and elemental distribution were observed by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). SEM analysis revealed that with higher energy density the pores and microcracks were improved. EDS data validated the composition is homogenized and stable after few layers …

Femtosecond Pulse Filamentation In Dielectric Media Toward Photonics Sensor Fabrication, Anitha Narayanan

Theses and Dissertations

Through pulse filamentation, femtosecond laser pulses have been utilized to modify the refractive indices of dielectric materials such as glass, A-plane sapphire crystal, and Cplane sapphire crystal. The 10x Infinity Corrected Lens was used, and the focusing condition was tuned as being the same and fixed to both glass and sapphire crystals. First, 8uJ of laser energy was optimized to produce controlled pulse filamentation voids in the glass. The laser intensity was then optimized to 2-3.5 uJ, 1.5 uJ, & 2.5 uJ, respectively, for the controlled pulse filamentation in A and C plane sapphire crystals. Due to the different crystal …

Development Of An Electro-Centrifugal Spinning Setup For Nanofiber Production Research, David A. Treviño

Theses and Dissertations

Nanofiber production methods have been developed and improved over the course of decades. Each process allows for the creation of fibers with distinct properties that provide benefits to growing number of applications. On the same note, every process has shortcomings that keep them from being universally valid for all applications. This research considers electrospinning and centrifugal spinning systems and attempts to create a process which maintains high fiber qualities like small and consistent fiber diameters, and improved fiber alignment while providing a high fiber yield. The electro-centrifugal (EC) spinning machine that resulted was designed utilizing computer aided design (CAD) software …

Feasibility Analysis Of Embedding Optical Fiber Sensor Into Additively Manufactured Part, Mahmudul Hasan Porag

Theses and Dissertations

The research tried to examine the viability of the embedment of optical fiber sensors in Additively built components, packaging the sensors within the components, and characterizing the sensors for sensing a specified measurement. Optical fiber sensors are popular due to their small size, resilience against electromagnetic radiation, and reliability in potentially dangerous conditions. Embedding fibers inside a product allows for the monitoring of critical areas, allowing for preemptive action in the case of a breakdown. Coupons of Inconel 718 were made using laser powder-bed fusion (LPBF), with the fabrication settings tuned to determine whether such a development was possible. After …

Analysis Of Propeller Designs Focusing On Lowering Sound Pressure Level Through Reduced Tip Loading, Luca A. Zeitvogel

Theses and Dissertations

This research focused on potential design optimizations for small propellers. Designs sought to reduce noise generated without sacrificing efficiency by “unloading” the propeller tip by reducing angle of attack near the tip. To see if nearfield performance improvements translated to a reduction in farfield sound pressure level, farfield experimental acoustic testing was performed on propellers that had been measured experimentally in the nearfield. The farfield results provided limited insight due to an equipment malfunction during testing. However, a large data set was obtained, which provides opportunities for future analyses. A computational simulation sought to recreate some of the nearfield experiments …

Design And Optimization Of High-Power Density Permanent Magnet Motor With Integrated Cooling For Aircraft Propulsion, Aravindakshan Thirumalai Ananthanpillai

Theses and Dissertations

There is a critical need for the electrification of transportation systems. While power density required for ground-based vehicles can, to some extent, be met by current off-the-shelf motors and generators, aircrafts require significant improvements both in terms of power density and efficiency. The concept relies on the tight integration of a high-power density dual-rotor permanent magnet motor, high power density SiC power converters, and a shared closed loop cooling system rejecting the heat in the propulsion ducted fan air stream. The motor is based on a dual-rotor configuration using permanent magnets forming ideal Halbach arrays allowing for high magnetic loading …

Thermal Design And Energy Analysis Of A Greenhouse In Microgravity Conditions, Nivedha Karigiri Madhusudhan

Theses and Dissertations

The recent progress in commercial space flights and prospects for interplanetary space missions has attracted more attention towards developing sustainable built environments in microgravity conditions. An important factor in establishing a sustainable living condition for outer space applications is the ability to produce food. The thermal design considerations in a greenhouse have a major impact on the survival, water efficiency, quantity, and quality of plants produced. The extremely low environmental temperatures necessitate the use of heaters which do consume energy. Given the scarcity of energy access, it is important to achieve proper thermal conditions with the lowest possible energy requirements. …

The Effect Of Zonation, Biofouling, And Corrosion Products On Cathodic Protection Design For Offshore Monopiles, Caglar Erdogan

Theses and Dissertations

Cathodic protection (CP) is required to prevent corrosion of the submerged steel for offshore wind monopile foundations in the marine environment. The design of these systems depends on the environmental conditions, including temperature, salinity, pH, dissolved oxygen, depth, micro- and macro-organisms, and water flow rates. The standards utilized to design cathodic protection systems consider only some of these conditions. This research identified the gaps in knowledge for the design of corrosion prevention systems for offshore wind monopile foundations and investigated the changes in cathodic current densities due to macro-galvanic cells, fouling communities and corrosion products established on uncoated vertical steel …

Tympanostomy Tubes In Children: A Fem Study Of Adverse Effects, Manuel Nicolas Jaramillo Bucheli

Theses and Dissertations

Background: The current study investigates if tympanic (myringotomy) tubes affect hearing by comparing the harmonic displacement response to sound excitation within the hearing frequency range for healthy vs. surgically-treated pediatric tympanic membranes. The use of ear myringotomy tubes has proven an effective method for combating recurrent ear infections in infants and children. These tubes are placed in the tympanic membrane through an incision and connect the middle ear to the external ear, thereby allowing fluid drainage and middle-ear ventilation. While this treatment has been proven beneficial in alleviating urgent pus accumulation in the middle ear, recent research shows that it …

Investigation Of Polymer Nanocomposites With Silicon Dioxide Fillers As Helium Cooled High-Temperature Superconducting Cable Dielectrics, Jordan Thomas Cook

Theses and Dissertations

In this thesis, three polymer nanocomposite configurations are fabricated for investigation as dielectrics in helium-cooled high-temperature superconducting (HTS) cables. Polyimide, polyamide, and polymethyl methacrylate are utilized as host polymers. The composite samples are synthesized through an in situ process, dispersing silicon dioxide nanoparticles throughout the polymer hosts. Fourier transform infrared spectroscopy and scanning electron microscopy were employed to validate the synthesis of each composite configuration. Thin film samples of each configuration were also tested for their dielectric strength at both room (300 K) and cryogenic (92 K) temperatures. When going from room to cryogenic temperatures, all materials demonstrated a significant …

A Hybrid Experimental-Computational Study: Prediction Of Flow Fields And Full-Field Pressure Distributions On Three-Tab Asphalt Roofing Shingles Subjected To Hurricane Velocity Winds, Troy A. Myers

Theses and Dissertations

A novel hybrid experimental-computational study is performed to predict the flow fields and pressure distributions on the measured shapes of flexible, three-tab asphalt roofing shingles undergoing increasing uplift when exposed to hurricane velocity winds. StereoDIC analysis is performed to measure the transient full-field deformed shapes of full-size three-tab asphalt shingles when subjected to hurricane velocity winds for two hours. Steady state computational fluid dynamics (CFD) simulations of the shingled roof facsimile-plenum region representative of the experiments are successfully performed. The simulations are performed to predict wind loading of the uplifted shingle shapes by utilizing the measured full-field three-dimensional uplifted shapes …

Impacts Of Preferential Vaporization Of Multi-Component Liquid Fuels On Near-Limit Combustion Behaviors, Seungjae Lim

Theses and Dissertations

Combustion technologies used in energy conversion devices involve multi-phase and multi-component combustion behaviors associated with chemical kinetic characteristics coupled with spray dynamics. For reliable engine operation, the engine operation envelope is necessarily required to be determined by near-limit combustion behaviors such as flame flashback, lean blowout, ignition, and extinction, which are influenced by both fuel chemical and physical properties. Liquid fuels are composed of a wide range of molecular structures and weights, therefore exhibiting relatively large distillation temperature range. When fuel chemical properties change during fuel vaporization, preferential vaporization effects could play a considerable role in near-limit combustion behaviors. In …

Towards Modeling Of Induction Welding Of Thermoplastic Laminates With A Mixed Finite Element Boundary Element Approach, Florentius Johannes Van Zanten

Theses and Dissertations

There is an increased interest in induction welding of carbon fiber reinforced thermoplastic composite laminates within the aerospace industry. Currently, optimal manufacturing process parameters (e.g., current, power, and frequency settings, coil movement speed, etc.) are determined through an experimental trial-and-error approach. To reduce the need for an experimental approach that can determine the manufacturing process parameters, which would be expensive in both time and money, accurate and computationally efficient numerical tools are desired. This research is focused on improving the existing numerical tool, WelDone, in regard to its speed and accuracy.

WelDone utilizes a hybrid element formulation that combines traditional …

Molten Salt Thermal Properties Database – Thermochemical Development And Thermodynamic Assessment Of Various Molten Salt Systems, Johnathon Chandler Ard

Theses and Dissertations

The Molten Salt Thermal Properties Database – Thermochemical (MSTDB-TC) is a validated open-source database for thermochemical modeling of molten salt reactor (MSR) relevant fluoride and chloride salt systems. The database has been created and populated by leveraging available models from literature as well as completing novel system assessments. The development and contents of the MSTDB-TC v1.2 initial release are detailed along with various system assessments performed in the course of the work. The database utilizes a major strength of the CALPHAD thermodynamic modeling method. This is the ability to estimate higher-order system behavior by combining modeled lower-order systems, …

Experimental Investigations Of Yarn Pull-Out Behavior In Kevlar®: Influence Of Applied Metallic Coatings And Effect Of Dynamic Loading, Julie Ann Roark

Theses and Dissertations

Flexible woven Kevlar® textile fabrics are widely used in protective armor applications. Yarn pull-out, comprised of yarn uncrimping (i.e., straightening) and yarn translation, is a major energy absorption mechanism during ballistic impact onto these fabrics, especially for impact velocities below the ballistic limit. Yarn pull-out is influenced by various parameters including inter-yarn friction, pull-out distance, pull-out velocity, transverse pre-tension, fiber diameter, fabric architecture, fabric waviness, fabric count and yarn modulus.

The first part of this thesis investigates yarn pull-out behavior of commercially available Kevlar® KM2+ individual yarns coated with metallic layers (copper, aluminum, aluminum nitride, silver) via a directed vapor …

High-Throughput Computation Of Interfacial Thermal Management Of Wide-Bandgap Semiconductors, Hao-Wen Chen

Theses and Dissertations

As semiconductor electronics, in particular high electron mobility transistors, get hot in operation, people are trying to incorporate different semiconductor materials to solve the problem of heat dissipation to maintain the device efficiency and performance. In this master thesis, two different packages, LAMMPS and almaBTE, that are focusing on micro-scale and atomic scale respectively, are used to simulate the heat transfer process across interfaces in two different scales. In the LAMMPS simulation, the research is exploring how the location of atoms and the thickness of interfacial layers will influence the interfacial thermal conductance. On the other hand, using the almaBTE …

Uncrewed Aircraft Systems For Autonomous Infrastructure Inspection, Michail Kalaitzakis

Theses and Dissertations

Uncrewed Aircraft Systems (UAS) are becoming increasingly popular for infrastructure inspections since they offer increased safety, decreased costs and consistent results, compared to traditional methods. However, there are still many open challenges before fully autonomous, reliable, and repeatable UAS inspections. While a UAS platform has increased mobility and can easily approach hard to reach areas, it has limited range and payload capacity and is susceptible to environmental disturbances. Therefore, current operations are limited to Visual Line of Sight (VLOS) manual inspections that usually result in just a qualitative (visual) assessment of the structure.

The objective of this work is to …

Fabrication Of Asymmetrical Hollow Fiber-Supported Thin Film Membranes, Stack Assembly, And Accelerated Long-Term Stability Test For Oxygen Production From Air, Myongjin Lee

Theses and Dissertations

Air separation is a widely used process for oxygen production. Several separation technologies have been developed for air separation, including cryogenic distillation, swing adsorption, redox process of metal oxides, and electrochemical process. Among these technologies, electrochemical permeation process stands out as a cost-effective and simple process for pure oxygen production from air. The electrochemical permeation process employs a gas-tight membrane to permeate and separate oxygen from air directly, where the membrane conducts both ions and electrons simultaneously. Different membrane designs have been studied to obtain the improved performance for oxygen permeation, typically planar and tubular designs. Among these membrane configurations, …

Shear Localization In The Metallic Nanolayered Composites, Shujing Dong

Theses and Dissertations

In this dissertation, the influences of layer thickness (h), interface orientation relationship (OR) and dislocation slip activities on shear band (SB) formation mechanisms was investigated by means of molecular dynamics (MD) simulations.

The effect of h and dislocation slip systems on the shear localization in Cu-FCC/Nb-BCC MNCs was studied. The strain softening observed in those samples was triggered by the SB formation. The microstructure evolutions and dislocation slips revealed that the unsymmetrical dislocation transmission across the interface induces the shear localization and promotes the SB formation. The quantitative analysis of the change in the separation distance of initially …

Use Of Dic Measurements With Finite Element Models For Direct Heterogeneous Material Property Determination And Wrinkle Formation During Automated Fiber Placement, Sreehari Rajan Kattil

Theses and Dissertations

In this work, application of DIC in combination with finite element modeling is demonstrated for efficient material characterization for complex heterogeneous materials and tow wrinkle formation during automated fiber placement.

The first part of the work describes the integration of DIC measurements with finite element models for direct property identification in heterogeneous material systems. The material property identification is based on solving partial differential equations (PDE) of equilibrium for unknown elastic material properties with known boundary conditions and full field strain data (Eg. DIC). The PDEs are solved numerically using Petrov-Galerkin finite element procedure. The classical Bubnov-Galerkin method is shown …

Investigation Of Adhesion, Deformation Mechanics, And Electrical Properties Of Ag/Sio2/Pdms Tri-Layers For Stretchable Electronic Applications, Rhandy Joe Paladines

Theses and Dissertations

The motivation behind this research is to improve the interfacial layer bonding of metallic thin films to PDMS substrates with the aid of a buffer layer. The physical vapor deposition (PVD) technique of sputtering was used to deposit bilayer thin films of silver (Ag) and silicon dioxide (SiO2) on PDMS. Two chamber pressures were used in this work, 5 and 20 mTorr, to investigate the role of this parameter in determining the interfacial adhesion and the role in determining the resistance sensitivity. Studies of the surface energy and increased bonding strength for metallization are carried out. Surface characterization using atomic …