Mechanical Engineering Commons^™

A Numerical Study Of Incompressible Fluid Flow Over A Forward Facing Step At Various Grades, Peter Andrew Martinez

Mechanical and Aerospace Engineering Theses - Archive

The study of the effect of natural forces on hydraulic structures is of great concern for the accurate prediction of when a design could be at risk of failure. In recent times the use of the shallow water equations to predict the behavior of the free surface for flow over a step has proven inaccurate because only a hydrostatic pressure distribution is considered. One of the phenomena that will not be accounted for with the shallow water equations in such a setup is the formulation of undular bore type waves on the surface. In order for a more accurate representation …

Design, Fabrication And Test Of Surface Tension-Driven Microboats And Thermally Oscillatory Bubble-Propelled Microsubmarines, Lei Qiao

Mechanical and Aerospace Engineering Dissertations - Archive

In this work, we develop microboats and microsubmarines, which are capable of moving on and under water, respectively. The microboat is propelled due to the difference between surface tensions around stern and bow. This difference is generated by releasing a liquid with lower surface tension than water from the stern. We explore both horizontal and vertical motions of the microboats through a combination of experimental and theoretical investigations. It has a length of 8 mm and weight of 20 mg with the highest speed of 25 cm/s and travel distance of 85 cm. Moreover, we design, fabricate and test microboats …

Cal Poly Nano Hydro, Brandon N. Fujio, Alex J. Sobel, Andrew F. Del Prete

Mechanical Engineering

This projects goal was to design, construct, and test a machine capable of generating a usable amount of energy from naturally flowing water. The device conceived for this purpose is a portable raft with a turbine mounted to the underside. The turbine is mated directly to a low angular velocity generator which outputs to a power electronics system on shore. Using a Gorlov Helical turbine, this proof-of-concept is designed to output ~50 Watts of electricity to charge a battery for later use. Possible applications for this device include camping in remote locations, supplemental power generation for a home, or for …

Design, Fatigue, And Strength Analysis Of A Tie Rod Hydraulic Cylinder Bolt, Jacob Roemen, Donald Webber

The Journal of Undergraduate Research

This report illustrates strength and fatigue analysis completed on a tie rod hydraulic cylinder bolt from a Lion TX 2500 tie rod hydraulic cylinder. The goal was to: solve for total clamping force, damping force per bolt at 90% proof load strength, amount of force per bolt, find the required number of bolts to hold the hydraulic cylinder together, solve for bolt spacing requirements, estimate a safety factor based on proof load strength, nut shear strength, required nut thickness, the least number of threads that must be engaged, estimate R.R. Moore Bending Fatigue Strengths, estimate the maximum value of P …

Assessing And Mitigating Airborne Noise From Power Generation Equipment, Limin Zhou

Theses and Dissertations--Mechanical and Aerospace Engineering

This dissertation examines the assessment and mitigation of airborne noise from power generation equipment.

The first half of the dissertation investigates the diagnosis and treatment of combustion oscillations in boilers. Sound is produced by the flame and is reflected downstream from the combustion chamber. The reflected sound waves perturb the mixture flow or equivalence ratio increasing the heat release pulsations and the accompanying sound produced by the flame. A feedback loop model for determining the likelihood of and diagnosing combustion oscillations was reviewed, enhanced, and then validated. The current work applies the feedback loop stability model to two boilers, which …

Decentralized Adaptive Control For Uncertain Linear Systems: Techniques With Local Full-State Feedback Or Local Relative-Degree-One Output Feedback, James D. Polston

Theses and Dissertations--Mechanical and Aerospace Engineering

This thesis presents decentralized model reference adaptive control techniques for systems with full-state feedback and systems with output feedback. The controllers are strictly decentralized, that is, each local controller uses feedback from only local subsystems and no information is shared between local controllers.

The full-state feedback decentralized controller is effective for multi-input systems, where the dynamics matrix and control-input matrix are unknown. The decentralized controller achieves asymptotic stabilization and command following in the presence of sinusoidal disturbances with known spectrum. We present a construction technique of the reference-model dynamics such that the decentralized controller is effective for systems with arbitrarily …

Kinetics Of Wedge-Tee Joint Formation During Brazing Of An Aluminum Alloy Under Controlled Atmosphere, Fangxiao Dong

Theses and Dissertations--Mechanical and Aerospace Engineering

This work involves investigation of the kinetics data of a joint formation during aluminum alloy brazing. Data was generated by several groups of experiments conducted under conditions of a controlled oxygen level of the background brazing atmosphere. Generated data are examined to identify the phases of the joint formation and the time frame of its evolution. Specifically, the triple line kinetics data are analyzed to verify whether a power law between (1) the triple line of the molten metal preceding joint formation and (2) the formation time can be established for each formation phase. In addition, both initial and residual …

Experimental Characterization Of Roughness And Flow Injection Effects In A High Reynolds Number Turbulent Channel, Mark A. Miller

Theses and Dissertations--Mechanical and Aerospace Engineering

A turbulent channel flow was used to study the scaling of the combined effects of roughness and flow injection on the mean flow and turbulence statistics of turbulent plane Poiseuille flow. It was found that the additional momentum injected through the rough surface acted primarily to enhance the roughness effects and, with respect to the mean flow, blowing produced similar mean flow effects as increasing the roughness height. This was not found to hold for the turbulence statistics, as a departure from Townsend’s hypothesis was seen. Instead, the resulting outer-scaled streamwise Reynolds stress for cases with roughness and blowing deviated …

Near Wall Shear Stress Modification Using An Active Piezoelectric Nanowire Surface, Christopher R. Guskey

Theses and Dissertations--Mechanical and Aerospace Engineering

An experimental study was conducted to explore the possible application of dynamically actuated nanowires to effectively disturb the wall layer in fully developed, turbulent channel flow. Actuated nanowires have the potential to be used for the mixing and filtering of chemicals, enhancing convective heat transfer and reducing drag. The first experimental evidence is presented suggesting it is possible to manipulate and subsequently control turbulent flow structures with active nanowires. An array of rigid, ultra-long (40 μm) TiO₂ nanowires was fabricated and installed in the bounding wall of turbulent channel flow then oscillated using an attached piezoelectric actuator. Flow velocity …

Numerical Modeling And Characterization Of Vertically Aligned Carbon Nanotube Arrays, Johnson Joseph

Theses and Dissertations--Mechanical and Aerospace Engineering

Since their discoveries, carbon nanotubes have been widely studied, but mostly in the forms of 1D individual carbon nanotube (CNT). From practical application point of view, it is highly desirable to produce carbon nanotubes in large scales. This has resulted in a new class of carbon nanotube material, called the vertically aligned carbon nanotube arrays (VA-CNTs). To date, our ability to design and model this complex material is still limited. The classical molecular mechanics methods used to model individual CNTs are not applicable to the modeling of VA-CNT structures due to the significant computational efforts required. This research is to …

Cerium Oxide (Ceo2) Promoted Oxygen Carrier Development And Scale Modeling Study For Chemical Looping Combustion, Fang Liu

Theses and Dissertations--Mechanical and Aerospace Engineering

According to IPCC reports, the greenhouse gas CO₂ is responsible for global climate change. Studies show that CO₂ concentration reached a level of 400 ppm in 2013, or 40 % above pre-industrial levels. The contribution of CO₂ from industrial activity to increasing global CO₂ concentrations is widely accepted and points to the need to reduce the emission of this greenhouse gas.One possible combustion technology that shows promise for reducing CO₂ emissions is chemical looping combustion (CLC). It is an oxy-fuel technology, but has the advantages of in situ oxygen separation, low NO_x emissions and …

Advanced Studies On Transfer Impedance With Application To After-Treatment Devices And Micro-Perforated Panel Absorbers, Xin Hua

Theses and Dissertations--Mechanical and Aerospace Engineering

This work is primarily comprised of five self-contained papers. Three papers are applications oriented. A common element in the first three papers is that micro-perforated panels (MPP), the permeable membranes in diesel particulate filters, and a source impedance are all modeled as a transfer impedance. The first paper deals with enhancing the performance of micro-perforated panels by partitioning the backing cavity. Several different backing schemes are considered which enhance the performance without increasing the total volume of the MPP and backing. In the second paper, a finite element modeling approach is used to model diesel particulate filters below and above …

Experimental Investigation To Inform Optimal Configurations For Dynamic Near-Field Passive Uhf Rfid Systems, Donnie E. Proffitt Ii

Theses and Dissertations--Mechanical and Aerospace Engineering

RFID has been characterized as a “disruptive technology” that has the potential to revolutionize numerous key sectors. A key advantage of passive RFID applications is the ability to wirelessly transmit automatic identification and related information using very little power. This paper presents an experimental investigation to inform the optimal configuration for programming passive ultra-high frequency (UHF) RFID media in dynamic applications. Dynamic programming solutions must be designed around the tag’s functionality, the physical programming configuration and environment. In this investigation, we present a methodology to determine an optimal configuration to maximize the systems programming efficiency for dynamic applications.

Process-Induced Surface Integrity In Machining Of Niti Shape Memory Alloys, Yusuf Kaynak

Theses and Dissertations--Mechanical and Aerospace Engineering

NiTi alloys have been the focus of Shape Memory Alloys (SMA) research and applications due their excellent ductility and shape memory properties, and these alloys have been extensively used in automotive, aerospace, and in biomedical applications.

The effects of machining on the surface integrity and the corresponding material and mechanical properties of alloys can be best studied by utilizing NiTi alloys as workpiece material since their physical and mechanical properties are highly microstructure dependent. However, due to very poor machining performance of NiTi shape memory alloys, no comprehensive or systematic investigation on this topic has been conducted by researchers as …

Thermomechanical Fatigue Life Prediction Of Notched 304 Stainless Steel, Justin Karl

Electronic Theses and Dissertations

The behavior of materials as they are subjected to combined thermal and mechanical fatigue loads is an area of research that carries great significance in a number of engineering applications. Power generation, petrochemical, and aerospace industries operate machinery with expensive components that undergo repeated applications of force while simultaneously being exposed to variable temperature working fluids. A case of considerable importance is found in steam turbines, which subject blades to cyclic loads from rotation as well as the passing of heated gases. The complex strain and temperature histories from this type of operation, combined with the geometric profile of the …

The Characterization Of The Effects Of Stress Concentrations On The Mechanical Behavior Of A Micronic Woven Wire Mesh, Steven Kraft

Electronic Theses and Dissertations

Woven structures are steadily emerging as excellent reinforcing components in dualphase composite materials subjected to multiaxial loads, thermal shock, and aggressive reactants in the environment. Metallic woven wire mesh materials display good ductility and relatively high specific strength and specific resilience. While use of this class of materials is rapidly expanding, significant gaps in mechanical behavior classification remain. This thesis works to address the mechanics of material knowledge gap that exists for characterizing the behavior of a metallic woven structure, composed of stainless steel wires on the order of 25 microns in diameter, and subjected to various loading conditions and …

On Radar Deception, As Motivation For Control Of Constrained Systems, Hadi Hajieghrary

Electronic Theses and Dissertations

This thesis studies the control algorithms used by a team of ECAVs (Electronic Combat Air Vehicle) to deceive a network of radars to detect a phantom track. Each ECAV has the electronic capability of intercepting the radar waves, and introducing an appropriate time delay before transmitting it back, and deceiving the radar into seeing a spurious target beyond its actual position. On the other hand, to avoid the errors and increase the reliability, have a complete coverage in various atmosphere conditions, and confronting the effort of the belligerent intruders to delude the sentinel and enter the area usually a network …

A Hybrid Constitutive Model For Creep, Fatigue, And Creep-Fatigue Damage, Calvin Stewart

Electronic Theses and Dissertations

In the combustion zone of industrial- and aero- gas turbines, thermomechanical fatigue (TMF) is the dominant damage mechanism. Thermomechanical fatigue is a coupling of independent creep, fatigue, and oxidation damage mechanisms that interact and accelerate microstructural degradation. A mixture of intergranular cracking due to creep, transgranular cracking due to fatigue, and surface embrittlement due to oxidation is often observed in gas turbine components removed from service. The current maintenance scheme for gas turbines is to remove components from service when any criteria (elongation, stress-rupture, crack length, etc.) exceed the designed maximum allowable. Experimental, theoretical, and numerical analyses are performed to …

Biomechanical Factors Influencing Treatment Of Developmental Dysplasia Of The Hip (Ddh) With The Pavlik Harness, Orlando Ardila

Electronic Theses and Dissertations

Biomechanical factors influencing the reduction of dislocated hips with the Pavlik harness in patients of Developmental Dysplasia of the Hip (DDH) were studied using a simplified three-dimensional computer model simulating hip reduction dynamics in (1) subluxated, and (2) fully dislocated hip joints. The CT-scans of a 6 month-old female infant were used to measure the geometrical features of the hip joint including acetabular and femoral head diameter, acetabular depth, and geometry of the acetabular labrum, using the medical segmentation software Mimics. The lower extremity was modeled by three segments: thigh, leg, and foot. The mass and the location of the …

Manufacturing Of Single Solid Oxide Fuel Cells, Jonathan Torres-Caceres

Electronic Theses and Dissertations

Solid oxide fuel cells (SOFCs) are devices that convert chemical energy into electrical energy and have the potential to become a reliable renewable energy source that can be used on a large scale. SOFCs have 3 main components; the electrolyte, the anode, and the cathode. Typically, SOFCs work by reducing oxygen at the cathode into O2- ions which are then transported via the electrolyte to the anode to combine with a fuel such as hydrogen to produce electricity. Research into better materials and manufacturing methods is necessary to reduce costs and improve efficiency to make the technology commercially viable. The …