Mechanical Engineering Commons^™

Characterizing And Optimizing The Molten Salt Cleaning, Yangyang Long

Theses and Dissertations - UTB/UTPA

Molten salt cleaning is an important cleaning approach in remanufacturing which can remove a variety of contaminants from metal substrates with high efficiency. Facing the very limited research of this approach in literature, this thesis intends to characterize molten salt cleaning process and optimize its parameters when big parts with complicated shapes are cleaned. Based on the development of molten salt cleaning and studies on contaminations, two experiments are conducted. The first one investigates the influences of the hot salts on three metal substrates and shows the applicable of cleaning carbon steel and grey iron parts with molten salt. The …

The Effects Of Retrogression And Reaging On Aluminum Alloy 2195, N. Ward, A. Tran, A. Abad, E. W. Lee, M. Hahn, E. Fordan, Omar S. Es-Said

Mechanical Engineering Faculty Works

A retrogression and reaging (RRA) treatment was performed on 2195 Al-Li Alloy. The exposure times were from 5 to 60 min, and the temperatures were from 200 to 250 A degrees C. Samples that were exposed to a salt spray test had overall similar mechanical properties as compared to those that were not exposed. The percent elongation, however, was significantly deteriorated due to the salt spray exposure. The mechanical properties of the 2195 samples were compared to those of 2099 samples exposed to similar treatments in an earlier study.

Electrokinetic Transport And Manipulation Of Particles In Curved Microchannels, Junjie Zhu

All Dissertations

The investigation of electrokinetic particle transport in confined microchannels has practical significances in a variety of applications ranging from traditional gel electrophoresis to electrokinetic microfluidics-based lab-on-a-chip devices. To date, however, studies on particle electrokinetics have been limited to primarily theoretical or numerical analyses in straight microchannels of simple geometries. Very little work has been done on electrokinetic particle motions in real microchannels which usually consist of one or multiple turns. This thesis is dedicated to the fundamental and applied studies of electrokinetic transport and manipulation of particles in various curved microchannels using a combined experimental, theoretical, and numerical method.
First, …

An Investigation Of The Effects Of Surfactant Monolayers On Natural Convection Heat Transfer And Evaporative Mass Transfer, Steven Bower

All Dissertations

Laboratory experiments are presented that reveal the effects of surfactant monolayers on natural convection heat transfer and evaporation from bodies of water; more specifically, the situation is studied where the bulk temperature of the water is greater than the temperature of the air so that evaporative convection occurs. Four sets of experiments were performed in a laboratory environment on insulated tanks of different widths and depths for the following surface conditions: 1) clean surface, 2) oleyl alcohol covered surface, 3) stearic acid covered surface, and 4) stearyl alcohol covered surface. An infrared (IR) camera was used to verify the existence …

Computational-Analysis Assisted Introduction Of Friction Stir Welding Into Development Of Light-Weight High-Survivability Military Vehicles, Guruprasad Arakere

All Dissertations

High strength aluminum alloys with superior blast/ballistic resistance against armor piercing (AP) threats and with high vehicle light-weighing potential are being increasingly used as military-vehicle armor. Due to the complex structure of these vehicles, they are commonly constructed through joining (mainly welding) of the individual components. Unfortunately, these alloys are not very amenable to conventional fusion based welding technologies (e.g. Gas Metal Arc Welding (GMAW)) and in-order to obtain high-quality welds, solid-state joining technologies such as Friction Stir Welding (FSW) have to be employed. However, since FSW is a relatively new and fairly complex joining technology, its introduction into advanced …

Experimental Testing Of The Accuracy Of Attitude Determination Solutions For A Spin-Stabilized Spacecraft, Keegan P. Ryan

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Spin-stabilized spacecraft generally rely on sun and three-axis magnetic field sensor measurements for attitude determination. This study experimentally determines the total accuracy of attitude determination solutions using modest quality sensors. This was ac- complished by having a test spacecraft collect data during spinning motions. The data was then post-processed to find the attitude estimates, which were then compared to the experimentally measured attitude. This same approach will be used to test the accuracy of the attitude determination system of the DICE spacecraft to be built by SDL/USU.

Development And Implementation Of Challenge-Based Instruction In Engineering Graphics, Gregory A. Potter

Theses and Dissertations - UTB/UTPA

This thesis discusses the challenge-based instructional (CBI) lessons currently being developed for the Engineering Graphics course at UTPA. This endeavor concentrates on student retention, as well as the students’ ability to practically apply their new skills. Minority science, technology, engineering, and math (STEM) students have been found, in recent studies, to depart from STEM undergraduate fields to some extent because of the lack of real world connections to the subject matter. Also, the traditional way of teaching theory first and then assigning a task may actually stifle creative thought and innovation required in later STEM courses. Our use of CBI …

Immersion Cooling Of Photovoltaic Cells In Highly Concentrated Solar Beams, Ahmed Darwish

UNLV Theses, Dissertations, Professional Papers, and Capstones

Concentrated solar radiation can be utilized to generate electrical power from photovoltaic cells, but concentrated solar radiation increases the photovoltaic cell’s temperature. This increase in temperature can lead to degradation of the cell efficiency, and too high of a temperature can damage the cell’s integrity. This is particularly important in dish and tower systems where a maximum uniform flux may be difficult to achieve. While a variety of approaches have been used to the keep the cells cool, most are based upon removal of heat from the back (opposite surface of the incident flux exposed surface) of the cell. This …

Time-Dependent Crack Growth Behavior Of Alloy 617 And Alloy 230 At Elevated Temperatures, Shawoon Kumar Roy

UNLV Theses, Dissertations, Professional Papers, and Capstones

Two Ni-base solid-solution-strengthened superalloys: INCONEL 617 and HAYNES 230 were studied to check sustained loading crack growth (SLCG) behavior at elevated temperatures appropriate for Next Generation Nuclear Plant (NGNP) applictaions with constant stress intensity factor (K _max = 27.75 MPa[checkmark]m) in air. The results indicate a time-dependent rate controlling process which can be characterized by a linear elastic fracture mechanics (LEFM) parameter - stress intensity factor (K). At elevated temperatures, the crack growth mechanism was best described using a damage zone concept. Based on results and study, SAGBOE (stress accelerated grain boundary oxidation embrittlement) is considered the primary reason for …

Robotic Manipulator With Multiple Instruments For Natural Orifice Translumenal Endoscopic Surgery, Chi Min Seow

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

This thesis presents a novel robotic manipulator with multiple instruments for use in Natural Orifice Translumenal Endoscopic Surgery (NOTES). NOTES is a newly emerging surgical technique that eliminates external incisions on patients’ skin. As a result, better cosmetics, shorter recovery time, and reduced risk of external infection can be achieved.

Research has been ongoing in academia and industry to make this surgical procedure more feasible in human surgeries. Although several robotic platforms have been developed, none of them has the required capability to provide surgeons with the most appropriate tool in a safe and timely matter during surgery. This robotic …

Effects Of Mass Layer Dimension On A Finite Quartz Crystal Microbalance, Y. P. Kong, Jinxi Liu, Huijing He, Jiashi Yang

Department of Mechanical and Materials Engineering: Faculty Publications

In this paper, we investigate free thickness-shear and thickness-twist vibrations of a finite crystal resonator of AT-cut quartz carrying a thin mass layer at the central portion of its top surface operating as a quartz crystal microbalance. The equations of anisotropic elasticity are used with the omission of the small elastic constant c56. An analytical solution is obtained using Fourier series from which the resonant frequencies, mode shapes and vibration confinement by the mass layer are calculated and examined.

Thermal Expansions In Wurtzite Aln, Gan, And Inn: First-Principle Phonon Calculations, L.-C. Xu, R.-Z. Wang, Xiaodong Yang, H. Yan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Using the first-principle phonon calculations under the quasiharmonic approximation, thermal expansions in III-nitrides with wurtzite AlN, GaN, and InN are reported. The results showed that it is different for each thermal expansion of three III-nitrides at low temperatures, which is consistent with their Grneisen parameters as the function of temperature. Below 50 K, negative thermal expansions occur in InN, while GaN and AlN follow the rule of positive thermal expansion. To seek the origin of positivenegative thermal expansion distinction, the mode Grneisen parameters and the phonon spectra are investigated. They indicate that different low-frequency phonon vibration modes correspond to the …

A Solid State Nitrogen Gas Generating Chip And Applications For Picosatellites, Kyle Godin

Graduate Theses and Dissertations

A microscale gas generating chip has many applications; in this study, applications relating to picosatellites have been considered. Cube satellites, a type of picosatellite, are of mass around one kilogram and side length 10cm x 10cm x 10cm. Their launches are becoming more numerous since their debut ten years ago. Their low cost and deployment system makes space accessible to agencies hitherto barred from it, such as universities and small governments. However, their power, mass, and volume budget is extremely tight. A microscale gas chip could compete with other designs for attitude control devices, most not flown yet as cube …

Gauge Repeatability And Reproducibility Study On A Hemi-Shell With A Brown & Sharpe® Coordinate Measuring Machine (U), Lucas Valdez

Mechanical Engineering Student Publications

In engineering at LANL, everything relies on the quality of a product or process. Today dimensional inspection is a necessity to ensure customer specifications are met to the highest standard. Currently LANL’s main processes for dimensional inspection on hemi-shells are conducted on uniquely designed machines - Sheffield or Shell Measuring Machine (SMM). These specialized rotary contour machines were built to measure only the wall thickness, inner and outer contours of a hemi-shell. These machines are heavily dependent on the inspector and typically have very few personnel trained to use them. With no manufacturer support and age leading to production down …

Packaging Strategy For High Voltage And High Shock Environments, Kevin Austin

Mechanical Engineering Student Publications

The historical design approach for ensuring survivability in devices that operate at high voltages which would arc in air or that must survive substantial shock loadings employs an encapsulant whose dielectric strength prevents electrical breakdown and whose modulus prevents gross movement of the embedded components. While mostly successful, this approach presents some significant design challenges: (1) the high thermal expansion of the epoxy leads to large stresses during thermal cycles, (2) degassing of the epoxy before cure and careful encapsulation are essential to eliminate voids that could initiate dielectric breakdown, (3) the internal components are embedded deep within an impenetrable …

A Priori Analysis Of Subgrid-Scale Pressure In High Pressure H2/O2 Mixing And Reacting Shear Layers, Zhiyuan Ma

All Theses

An a priori analysis of subgrid-scale pressure in high pressure combustion is carried out using three different flow fields obtained by direct numerical simulation (DNS). The simulations directly solve the Navier-Stokes equations of high pressure, transitional H₂/O₂ mixing and reacting shear layers employing a cubic Peng-Robinson real gas state equation. Detailed chemistry, multicomponent, differential, and cross diffusion are included. The results are analyzed to provide subgrid information relevant to Large Eddy Simulation (LES) of turbulent combustion. The analysis includes a detailed comparison of the actual filtered pressure with its corresponding form evaluated with the filtered primitive variables. …

Injection Molding Of Micro-Features, Manjesh Dubey

All Theses

A method for creating regular arrays of surface features in the 10µm to 200µm range over large areas in metallic materials enables the use of treated surfaces on injection molds. This surface control is used for manufacturing products with controllable optical, tribological, heat transfer, and surface tension properties. However, the flow, filling, and solidification behavior of molten polymer at the micro scale is not well understood.
Therefore, the purpose of this study is to understand the formation of micro-structure on a polymer surface and derive a range of robust solutions for injection molding of these micro-featured surfaces. This study uses …

Viscoelastic Damping Of Hexagonal Honeycomb Sandwich Panels, Nikhil Seera

All Theses

Composite sandwich structures with a viscoelastic core material constrained between thin stiff face sheets are an effective means of damping in engineering applications. Damping introduces energy dissipation which helps control vibration amplitudes. Conventional Hexagonal honeycombs are often referred to as regular honeycombs and are defined by cellular geometry with effective positive Poisson's ratio. Regular honeycombs are commonly used for the cores of sandwich plates because of their low density and high stiffness properties. Honeycombs with negative in-plane Poisson's ratio are known as Auxetic honeycombs and offer enhancement of mechanical properties such as impact absorption, damage resistance, when compared to regular …

Multi-Length Scale Modeling Of The High-Pressure, Large-Strain, High-Strain-Rate Response Of Soda-Lime Glass, William Bell

All Dissertations

Development of new transparent armor systems is essential for the protection of the current and future US armed forces, especially in light of the recent military operations The Operation Iraqi Freedom in Iraq and The Operation Enduring Freedom in Afghanistan. These conflicts have introduced a new military theater without a well-defined battle front and new types of threats (e.g. improvised explosive devices, IEDs). Development and modeling of new transparent armor systems for use in numerous applications from vehicle windows to face shields is a current area of thrust aimed at addressing the shortcomings of existing systems in order to better …

Mixture Fraction Imaging Based On Photodissociation Spectroscopy And Two Photon Laser Induced Fluorescence, Yan Zhao

All Dissertations

The study of turbulent combustion calls for new diagnostics that can measure multidimensional mixture fraction under a wide range of flame conditions. A laser diagnostic technique based on photodissociation spectroscopy (PDS) is proposed to address this need. This thesis describes the concept of the PDS-based diagnostic, reports its experimental demonstration in a non-premixed jet flame, and assesses its performance and applicable range. The two-photon laser induced fluorescence (TPLIF) technique used in conjugate with the PDS is analyzed numerically in line and planar imaging configuration.
The new mixture fraction imaging technique is centered around the creative use of photodissociation (PD) for …