Mechanical Engineering Commons^™

Measuring The Vortex-Shedding Frequency Behind Staggered Cylinders In Cross-Flow, Christopher Clark

Mechanical Engineering Master's Theses

In this thesis, the Strouhal numbers from the downstream cylinder in a two cylinder configuration have been measured experimentally. Special apparatuses were designed to secure the cylinders in the wind tunnel as well as to hold a hot film anemometer probe in the center of the downstream cylinder’s wake. The cylinders were smooth, of equal diameter and extended the entire width of the wind tunnel. Because the cylinders used in this thesis were sufficiently long compared to their diameters and measurements were taken at center span, they were assumed to be infinite. The anemometer was calibrated according to King’s Law, …

Development Of Iowa Dot Combination Bridge Separation Barrier With Bicycle Railing, Chaz M. Ginger

Department of Engineering Mechanics: Dissertations, Theses, and Student Research

The Iowa Department of Transportation typically builds separation barriers between vehicle and pedestrian/bicycle facilities when sidewalks or trails are present on vehicular bridges. Currently, Iowa DOT employs a combination bridge rail that utilizes a concrete parapet that previously had been successfully evaluated to National Cooperative Highway Research Program (NCHRP) Report 350 Test Level 4 (TL-4) criteria for these situations. While the parapet had been successfully evaluated, the combination bridge rail system as a whole had not been evaluated to any crash test standards. Iowa DOT desired that researchers at Midwest Roadside Safety Facility (MwRSF) design and test a combination bridge …

Multi-Physics Design Optimization Of 2d And Advanced Heterogenous 3d Integrated Circuits, Pavan Rajmane

Mechanical and Aerospace Engineering Dissertations - Archive

The convergence and miniaturization of computing and communications dictate building up rather than out. As planar device miniaturization continues to its ultimate limits, the complexity of circuit interconnections for 2-D devices becomes a limitation for performance and drives up power dissipation [1]. Failure analysis and its effects are major reliability concerns in electronic packaging. More accurate fatigue life prediction can be obtained after the consideration of all affecting loads on the electronic devices. In this study, an attempt is made to analyze 3 types of packages i.e. Wafer Level Chip Scale Package (WCSP), Quad Flat No-Lead (QFN) Package and 2-Die …

A Framework For Optimal Path Planning And Nonlinear Guidance For Autonomous Mobile Robots, Paul A. Quillen

Mechanical and Aerospace Engineering Dissertations - Archive

The purpose of this research is to investigate methods and technology for enhancing autonomous capabilities for mobile robots. The measures of autonomy which are specifically covered in this dissertation pertain to a mobile robot’s ability to make decisions and act, in other words guidance and control. This dissertation puts forth a framework using optimal path planning and nonlinear guidance techniques to address these matters. The path plans are synthesized using a numerical navigation function algorithm that will form its potential contour levels based on the “minimum control effort” of the system. Additionally, extensions of the path planning algorithm in the …

Numerical And Experimental Study Of Single Phase And Multiphase Droplet Dynamics On Electrowetting-On-Dielectrode Digital Micro-Fluidics, Mun Mun Nahar

Mechanical and Aerospace Engineering Dissertations - Archive

In the recent years, significant efforts have been devoted to the development of droplet based lab-on-a-chip devices of which advantages include being programmable and reconfigurable. Among various droplet flow based microsystems [1-5], electrowetting on dielectric (EWOD) digital microfluidics has many advantages, such as rapid switching response, no joule heating, no need for moving parts like pumps and valves, and most importantly low power requirement [6]. Basic droplet handling techniques - droplet dispensing, transporting, merging and splitting - can be done by sequentially activating and deactivating specific electrodes, which allows to address each droplet individually and to perform various unit processes …

A Multiphysics Study Of Interfacial Properties Of 3d Printed Filaments, Alireza Rezaee

Mechanical and Aerospace Engineering Dissertations - Archive

Fused Deposition Modeling has become the most popular 3-D printing method over the last decade. Due to its potential to save time, cost and, labor, there is a great deal of interest to use this technique for production of functional load carrying parts and assemblies in bio-medical, automotive, aerospace, and oil and gas industries. In general, materials used in FDM process are isotropic; however, parts printed using FDM process show anisotropic mechanical properties with inconsistent properties in the transverse direction to the filaments’ cross-section. This anisotropic behavior is due to the fabrication process, and the inconsistency in the transverse mechanical …

Characterizing Contamination To Expand Ashrae Envelope In Airside Economization And Thermal And Reliability In Immersion Cooling Of Data Centers, Jimil Manojbhai Shah

Mechanical and Aerospace Engineering Dissertations - Archive

The Datacom facility which comprises rooms or closets used for communication, computers/servers or electronic equipment requires cooling unit which consumes 31% (23% HVAC cooling + 8% HVAC fans) of overall energy. The ASHRAE TC9.9 subcommittee, on Mission Critical Facilities, Data Centers, Technology Spaces, and Electronic Equipment, has suited the data center’s executives by permitting brief period outings of the environmental conditions outside the prescribed temperature-humidity range, into passable extents A1-A3. To comprehend the expanding server densities and the required cooling vitality costs, data center operators are falling back on cost cutting measures. For instance, they are not firmly controlling the …

Woods Tire Model, Priyank Vasant Nandu

Mechanical and Aerospace Engineering Theses - Archive

The performance of a racecar in a maneuver is almost totally determined by the characteristics of the tires and the suspension setup. If the suspension is properly tuned for the maneuver, then the limiting factor is the tire. Therefore, any racecar design and performance analysis must start with a full description of the performance of the tire [1]. Mathematical models for tire performance such as the Pacejka model have been in use for a long time and have become the standard for expressing how a tire will perform dynamically. It comprises of curve fit to experimental data and requires about …

Thermodynamic Modeling And Transient Simulation Of A Low-Pressure Heat Recovery Steam Generator Using Siemens T3000, Andres Caesar

Electronic Theses and Dissertations

With world energy consumption rising, and nonrenewable energy resources quickly depleting, it is essential to design more efficient power plants and thereby economically utilize fossil fuels. To that end, this work focuses on the thermodynamic modeling of steam power systems to enhance our understanding of their dynamic and transient behavior. This thesis discusses the physical phenomena behind a heat recovery steam generator (HRSG) and develops a mathematical description of its system dynamics. The model is developed from fundamentals of fluid dynamics, phase change, heat transfer, conservation laws and unsteady flow energy equations. The resulting model captures coupled physical phenomena with …

Design Survey Of Laminated Composite I-Beam, Mrinmoy Saha

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

Composite I-beams are popular for high-strength low-weight applications. Learning the macro-mechanics and designing the composite I-beam properly are necessary. In this report, a design overview of the composite I-beam is discussed which is based on classical lamination theory where it includes the homogenization approach, the plane stress assumption and the Kirchhoff hypothesis. Using these assumptions, a method was developed to come up with the effective material properties of a beam. Formulas to calculate maximum deflection and maximum bending stress and shear stress and the stress concentration at the connection of web-flange are discussed which describe ways for designing and manufacturing …

Investigation Of Thermo-Physical Property Enhancement Mechanism Of Molten Salt Nano-Eutectic Via Nanostructural Change And Polyalphaolefin Nanofluid Via In Situ Formation Of Superstructures, Zahra Pournorouz

Mechanical and Aerospace Engineering Dissertations - Archive

For many years, scientists enhanced the specific heat capacity of molten salt nanofluids by dispersing only minute concentrations of different nanoparticles (e.g., 1 wt.%). While the specific heat capacity for molten salts was enhanced in many types of research, other engineering fluids (i.e., water, ethylene glycol, oil) showed decreased specific heat capacity with doping the nanoparticles. Recently, researchers discovered that a unique nanostructure formed by molten salt molecules, which were doped and interacted with nanoparticles, were the reason for enhanced specific heat capacity. Therefore, the enhanced specific heat capacity only happens for molten salts rather than other fluids that may …

Wireless Antenna Sensors For Boiler Condition Monitoring, Franck Tchafa

Mechanical and Aerospace Engineering Dissertations - Archive

Structural Health Monitoring (SHM) is a vital technology that implements real-time condition monitoring or damage detection mechanisms for the safety assurance of structural systems such as power stations, aircrafts, bridges, dams, buildings, large machinery, and more. Without proper and timely maintenance, mechanical systems are prone to failures since they experience detrimental factors such as harsh environments, excessive loads, and vibrations. Several sensing technologies exist for SHM applications. Patch antennas are among the list of these technologies, and they are an attractive choice due to their compact size, light weight, ease of manufacturing, and low fabrication cost. Patch antennas have been …

Developable Compliant-Aided Rolling-Contact Mechanisms, Todd G. Nelson, Just L. Herder

Student Works

Rolling-contact mechanisms can provide low-friction motion with unique kinematic paths. We show that developable surfaces can be used as a design tool for rolling-contact mechanisms joined with compliant bands. These mechanisms can exhibit 3D motion paths, couple rotational and translational motions into a single degree of freedom, and can be designed to exhibit various tailored kinetic responses. We set forth developable surface parametrizations well suited to the creation of rolling contacts. We highlight how the geodesic and principal curvatures of the non-ruling principal curves of a developable surface are meaningful design quantities for rolling contacts. We provide kinematic and kinetic …

Low-Cost Experimental System For Center Of Mass And Center Of Pressure Measurement, Cai Xia Yang

Mechanical Engineering Faculty Publications

Falls happen when the center of mass of body is outside of its base of support and the recovery of the center of mass back to the base of support failed. Balance ability is an essential ability needed for humans' daily routine activities. Improving balance ability should result in a better and more convenient way of living. There are various factors influence on balance ability. The focus of this paper is to investigate which factors have the greatest effect on balance. Balance ability is measured by deviations of center of pressure in both x-direction (side-to-side) and y-direction (front-to-back) with the …

Water Entry Cavity Dynamics, Nathan B. Speirs

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

When a sphere or a stream of water hits the surface of a pool of water and enters a crater or air cavity often forms. This topic has been studied, both formally and informally, for a long time. This dissertation investigates four areas of water impact that are still poorly understood using high-speed photography. First, it examines a stream of droplets impacting on a pool of water, similar to a faucet drizzling into a full bucket. For these types of impacts we predict the depth, diameter, velocity, and shape of the cavities that the droplet stream forms. Second, it examines …

Fast Prediction Of Thermal Distortion In Metal Powder Bed Fusion Additive Manufacturing: Part 2, A Quasi-Static Thermo-Mechanical Model, Hao Peng, Morteza Ghasri-Khouzani, Shan Gong, Ross Attardo, Pierre Ostiguy, Ronald B. Rogge, Bernice Aboud Gatrell, Joseph Budzinski, Charles Tomonto, Joel Neidig, M. Ravi Shankar, Richard Billo, David B. Go, David Hoelzle

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The additive manufacturing (AM) process metal powder bed fusion (PBF) can quickly produce complex parts with mechanical properties comparable to that of wrought materials. However, thermal stress accumulated during Metal PBF may induce part distortion and even cause failure of the entire process. This manuscript is the second part of two companion manuscripts that collectively present a part-scale simulation method for fast prediction of thermal distortion in Metal PBF. The first part provides a fast prediction of the temperature history in the part via a thermal circuit network (TCN) model. This second part uses the temperature history from the TCN …

Decomposition And Ionization Of Ionic Liquids, Forrest Grady Kidd Iii

Dissertations

The United States Air Force is interested in developing a situationally responsive space environment. In order to achieve this, dual-mode-propulsion will be utilized. A new class of propellants is being developed for this application based on energetic ionic liquids. Two ionic liquids of current interest are Hydroxylammonium Nitrate (HAN) and Hydroxyethylhydrazinium Nitrate (HEHN) due to their beneficial performance characteristics. The decomposition and ionization chemistry of these two species is investigated in this work. Using GAUSSIAN09 software, reactions with important radicals are explored through quantum chemistry. The energetics of reactions as well as the identity of key product complexes are given. …

Thermal And Stress Analysis Of Nasa X-57 Maxwell Battery Pack, Bhumika Nautiyal

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

Air travel has long been an established way of life for millions around the world, but innovation continues to push the boundaries of what is possible in the skies. While aviation has made it easy to travel long distances, the need to lower emissions from flights is pressing. The European Commission has described aviation as “one of the fastest-growing sources of greenhouse gas emissions.”

Airplanes release around 500 million tons of carbon dioxide into the atmosphere each year, representing a significant contribution to global warming. The very concept of a fossil-fuel-powered airplane needs to evolve to fully mitigate the impacts …

Experimental Comparison Between Hollow Cathodes With Cermet, Lanthanum Hexaboride, And Barium Oxide Insert Materials, Nagual Simmons

Masters Theses

This thesis compares two different hollow cathode assemblies (HCA) using three different insert materials. NASA’s Jet Propulsion Laboratory (JPL) provided the H6 HCA and the Lanthanum Hexaboride (LaB₆) insert. A barium oxide (BaO) insert was purchased from Ebeam and used with the H6 HCA. The novel Cermet material was purchased from Plasma Controls, LLC and the HCA was based on the JPL H6 HCA. Plasma properties in the external region of all three inserts and the internal region of the LaB₆ were determine using two separate Langmuir probes. Various operating points were tested at a combination of …

Thermal And Mechanical Response Of Inner Cone Sample Of Zrb₂-Sic Ceramic Under Arc-Jet Conditions, Jun Wei, Lokeswarappa R. Dharani, K. Chandrashekhara

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Under arc-jet test conditions, ZrB₂-SiC ceramic will undergo high temperature oxidation and develop an external glassy layer (SiO₂), zirconia sub-layer (ZrO₂) and SiC-depleted diboride layer (ZrB₂). This study relates to finite element modeling of the effects of oxidation on heat transfer and mechanical behavior of ZrB₂-SiC ceramic under arc-jet test conditions. A steady-state heat transfer FE method was employed to conduct the heat transfer analysis to obtain the temperature distribution in the inner body of the cone. The surface thermal conditions available in the literature were used in the heat …

Generation Of Transverse Photo-Induced Voltage In Plasmonic Metasurfaces Of Triangle Holes, Marjan Akbari, Jie Gao, Xiaodong Yang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We experimentally and numerically demonstrate the transverse electrical response produced by circularly-polarized light with normal incidence observed as transverse photoinduced voltage across the plasmonic metasurface made of triangle holes. The measured transverse photo-induced voltage is consistent with the calculated acting force on electrons in the metasurface by using the Maxwell's stress tensor. The polarity of voltage reverses as the incident spin (light helicity) switches from right-handed circular polarization to left-handed circular polarization. The origin of the spin-dependent voltage sign is the broken symmetries of the electric and magnetic fields in the triangle hole due to the opposite circular polarizations. The …

Fast Prediction Of Thermal Distortion In Metal Powder Bed Fusion Additive Manufacturing: Part 1, A Thermal Circuit Network Model, Hao Peng, Morteza Ghasri-Khouzani, Shan Gong, Ross Attardo, Pierre Ostiguy, Bernice Aboud Gatrell, Joseph Budzinski, Charles Tomonto, Joel Neidig, M. Ravi Shankar, Richard Billo, David B. Go, David Hoelzle

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The additive manufacturing (AM) process metal powder bed fusion (PBF) can quickly produce complex parts with mechanical properties comparable to wrought materials. However, thermal stress accumulated during PBF induces part distortion, potentially yielding parts out of specification and frequently process failure. This manuscript is the first of two companion manuscripts that introduce a computationally efficient distortion and stress prediction algorithm that is designed to drastically reduce compute time when integrated in to a process design optimization routine. In this first manuscript, we introduce a thermal circuit network (TCN) model to estimate the part temperature history during PBF, a major computational …

Shape Optimization Of A Fan Duncte For A Vertical Takeoff And Landing, Jie Hua

Mechanical and Aerospace Engineering Theses - Archive

The popularity of ride sharing services and recent improvements in electric car performance and automation have sparked interest in E-VTOL (Electric Vertical Takeoff and Landing) aircraft for personal transportation. Companies such as Uber, Airbus and EHANG are currently researching such aircraft for transportation over short distances in crowded urban environments. A personal E-VTOL design based on a ducted fan concept is proposed and the vertical lift capability is optimized. A numerical optimization algorithm is coupled with a computational fluid dynamics (CFD) analysis code to perform shape optimization. The objective is to determine the internal and external duct shape that maximizes …

A Study Of Effect Of Bond Length On Bond Strength Using Transient Heat Transfer Analysis, Junaid Mohamed Baig

Mechanical and Aerospace Engineering Theses - Archive

It is important to understand the mechanical properties of the bonding between the adjacent layers of 3D printed parts build by fused deposition modeling. The bonding process is highly nonlinear and depends on various geometrical and thermal process parameters. This work aims to quantify the degree of bonding by calculating bond potential between the extruded layers using finite element heat transfer analysis. Successive transient analysis were carried out using this model by constantly updating the boundary conditions and geometric model during the deposition of the extruded bead. Temperatures at critical points were calculated over a period to calculate the bond …

Inverse Analysis Of Heat Generating Body For Safety Applications, Sandeep Patil

Mechanical and Aerospace Engineering Dissertations - Archive

Inverse thermal analysis and its applications have been applied to numerous fields of science and engineering. Historically during the 1950's and early 1960's, space programs played a significant role in the advancement of solution techniques for Inverse Heat transfer Problems(IHTP). It was applied to measure the surface temperature of thermal shield of a space vehicle during its re-entry into atmosphere. Inverse analysis was also used in the estimation of thermo-physical properties of the shield at high operating temperatures. Besides thermal application, inverse technique was also used in other engineering applications such as estimation of alloy specification, design of a shape …

Optimization Of Board Level Reliability Of Microelectronic Packages And Modules, Alok Kumar Lohia

Mechanical and Aerospace Engineering Dissertations - Archive

Thermo-mechanical reliability estimation of electronic packages and modules provides an opportunity to predict the function life of semiconductor devices. The problem complexity lies in the fact that there are variety of electronic packages with different form factors, materials and manufacturing technology for various applications. The custom PCB ranges from very thin for portable application to very thick for power application. Despite conventional understanding and prior studies, some of the failures were not explained. This study reviews three failure problems for QFN, WCSP and BGA packages by characterizing the properties of custom PCB materials by layer removal process. Due to layup …

Control-Oriented Automatic Transmission- Based Powertrain Modeling And Simulation With Judder, Harshal B. Kundale

Masters Theses

This work presents automatic transmission-based powertrain modeling. The powertrain consists of an engine, torque converter with lock up clutch, transmission gearbox, propeller shaft, and vehicle body. Simplified powertrain component models are developed for vehicle powertrain dynamic response analysis and future control work. The powertrain components are modeled with algebraic and first order non-linear differential equations. A MATLAB-based powertrain simulation system is developed to investigate the transient characteristics during lock up of torque converter. Simulation results are used in the determination of effects of judder on torque and angular velocity. Clutch judder is a self-excited vibration that occurs during the clutch …

Large Scale Cryogenic Storage With Active Refrigeration, Adam Swanger

Electronic Theses and Dissertations

Storage and transfer of cryogenic liquefied gases on volume scales from under 10 liters for lab use, up to hundreds of millions of liters for industrial applications is of paramount importance across a vast range of industries. Traditionally, these commodities have been stored at or near the normal boiling point due to relative ease of operation and safety-related considerations; however, this also means that some percentage will always be lost due to environmental heat leaking into the vessel and causing boiloff. These losses become more concerning as scales increase, and are of particular importance for high-cost commodities such helium and …

New Era In Designing And Governing Cooling Intensity Of Liquid Quenchants To Decrease Distortion During Hardening Of Steel Parts, Nikolai I. Kobasko, Anatolii A. Moskalenko, P. N. Logvynenko, George E. Totten, Volodymyr V. Dobryvechir

Mechanical and Materials Engineering Faculty Publications and Presentations

It was proved in last decade that very intensive and uniform cooling eliminates quench crack formation and significantly decreases distortion of quenched steel parts as compared with their slow cooling in mineral oils. That opened a new era in design ing and governing cooling intensity of liquid quenchants for strengthening steel parts and decrease their distortion after quenching. The new approaches were developed by authors to provide accelerated and uniform cooling steel parts during quenching by creation on their surface thin insulating layers. For this purpose low concentration of water polymer solutions of inverse solubility are used as a quenchant. …

Temperature Effects On Helium Filled Soap Bubble Particle Tracking Velocimetry., Michael C. Blum

Electronic Theses and Dissertations

Helium Filled Soap Bubble (HFSB) Particle Tracking Velocimetry (PTV) methods are becoming increasingly popular as they provide a low cost, safe option for reliable flow visualization. Several studies have been conducted to understand the accuracy of such systems under normal temperatures and pressures; however, no such studies to date have examined accuracy of HFSB PTV at high temperatures. The goal of this study is to characterize the capability of HFSB PTV methods to visualize air flow through a rectangular duct at elevated temperature. A heated wind tunnel was designed to heat up to 150 m³/h of 25 °C …