Mechanical Engineering Commons^™

Generation And Analysis Of Fcg Data Using A Single Specimen And Kmax - ∆K Testing Matrix, Sree Phani Chandar Reddy

Masters Theses

A custom method to generate fatigue crack growth (FCG) data requires testing of multiple specimens at different load ratios. In addition, it includes the application of a load shedding procedure from pre-cracking level to threshold.

In this thesis, a novel method of testing has been investigated that utilizes a single specimen and a testing matrix in terms of K_maxand ∆K values corresponding to predetermined R-ratios for which FCG data, da/dN, are recorded. Automatic K-controlled tests on 2324-T39 Al alloy were conducted using the ∆K increasing and ∆K decreasing procedures while K_maxwas kept constant. Results show that …

Numerical Analysis For Determination Of Fiber Orientation In Nonwoven Mats, Lee Reynolds Allen

Masters Theses

The University of Tennessee Space Institute is interested in pitch-based carbon fibers. A need has arisen for characterizing relative alignment of nonwoven fiber mats, produced by the spinning gathering technology implemented. Knowledge of this alignment is relevant in the validation of production methodology as well as aiding in the analysis of carbon fiber composite materials made with the fiber mats. A digital image processing method was developed presented and evaluated in this thesis consisting of three steps: preprocessing using image smoothing, edge detection based upon local intensity gradients, and line detection via the Hough Transform. A summary of typical results …

Ductile-Regime Machining Of Silicon Carbide And Quartz, Deepak Ravindra

Masters Theses

Silicon carbide (SiC) and quartz are one of the advanced engineered ceramic materials designed to operate in extreme environments. One of the main reasons for the choice of these materials is due to its excellent electrical, mechanical and optical properties that benefit the semiconductor, MEMS and optoelectronic industry respectively. Manufacturing these materials is extremely challenging due to its high hardness, brittle characteristics and poor machinability. Severe fracture can result when trying to machine SiC and quartz due to its low fracture toughness. However, from past and current research efforts, it has been proven that ductile regime machining of brittle materials …

The Effect Of Bluff Body Flameholders On The Inter-Turbine Burner Performance, Richard Jackson Holder

Masters Theses

In this thesis, a three-dimensional numerical simulation has been conducted to study the complex reactive flows which are present during the combustion in an inter-turbine burner (ITB) with the inclusion of V-gutter flame holders. Optimal conditions for the V-gutter were then further studied through a parametric study. The ITB configuration with straight radial vanes (SRV) was based on the innovative, high efficiency, high-g Ultra-Compact Combustor (UCC) concepts developed at the Air Force Research Laboratory (AFRL).

For the first section, the V-gutter’s angle of attack was varied from -10 degrees to 10 degrees. The turbulent flow was modeled with a RANS-based …

Effects Of High Temperature Cyclic Aging On A Fully-Formulated Lean NoX Trap Catalyst, Nathan Andrew Ottinger

Masters Theses

The thermal deactivation mechanisms of a lean NO_x trap (LNT) are analyzed in this study. Accelerated lean/rich aging experiments are performed with a bench-flow reactor, and high temperature exotherms are achieved with pulses of reductants. Reduction in steady state NO_x conversion as a result of aging is evaluated at a range of temperatures using the same bench-flow reactor. The results of these evaluations are used to show that NO_x conversion in this study is a function of evaluating temperature, aging temperature, and number of aging cycles.

Surface characterization studies are used to determine changes in washcoat morphology. …

Prediction Of Fatigue Crack Growth Retardation Due To A Tensile Overload Using Two-Parameter (∆K, Kmax) Approach, Wataru Tsutsui

Masters Theses

A theoretical crack growth study on powder metallurgy aluminum alloys AA5091 and AA8022 was conducted. Specifically, the research focused on the crack growth retardation due to the application of a tensile overload. The tensile overload creates a plastic zone ahead of the propagating crack tip that induces the compressive residual stress after unloading. Such compressive residual stress pushes the crack tip faces against each other, which results in crack growth retardation.

In the study, simulation started from the calculation of the compressive residual stress. The details of the calculation steps are explained in the thesis. Eventually, the stress intensity factor …

Mechanical Property Testing Apparatus For Use In A Scanning Electron Microscope, Robert Brian Peters

Masters Theses

The purpose of this design project is to develop a mechanical testing device to work in conjunction with a scanning electron microscope [SEM]. The objective of this work was to be able to perform a mechanical property measuring test and observe the small scale physical behavior of the sample with the SEM as the test progresses. The design process is presented from concept development through to the completion of the prototype device. Test data was acquired and analyzed and the results are compared to standard values for the materials being tested. Recommendations for future improvements in the next generation of …

Experimental Measurement Of Thermal Conductivity Of An Unknown Material, Aaron Christopher Whaley

Masters Theses

The objective of this study was to determine effective thermal conductivity of an unknown material sample for sample temperatures up to 1000 degrees Celsius. A steady state, one-dimensional heat conduction test setup was designed, fabricated, assembled, and used to determine thermal conductivity of the sample. The measurement was accomplished by applying a heat flux from a radiant heater through a stack consisting of the test sample, reference plates, heat spreaders, and insulation layers. The heat transfer equation for steady state, one-dimensional conduction relates thermal conductivity of the sample to the thickness and cross-sectional area of the sample, the temperature difference …

Development Of An Accelerated Ash Loading Protocol For Rapid Evaluation Of Diesel Particulate Filters Including Comprehensive Characterization Of Ash-Loaded Substrates, Adam Daniel Youngquist

Masters Theses

The accelerated ash loading of diesel particulate filters (DPFs) by lube-oil derived products is investigated in the present study. A 517-cc single-cylinder, naturally aspirated direct-injection diesel engine is used to accelerate ash formation by artificially increasing the rate of lube-oil consumption to approximately 40 times that observed during normal engine operation. Lube-oil consumption (LOC) is accelerated by blending diesel fuel with 5% by volume of standard 15-w40 lube oil and is subsequently injected through the fuel injector into the combustion chamber.

The ash loading protocol is a backpressure-based method of determining the amount of soot present within the DPF and …

Investigative Study On An Energy Theorem For Developing Testing Functions For Numerical Simulations Of Multibody Dynamic Systems, Kulasegaram Gugaratshan

Masters Theses

Multibody dynamic systems designers utilize computer software extensively to simulate the motion of mechanical systems. The governing differential equations of motion are formulated and solved numerically. The accuracy of the numerical solutions is always a concern to the analyst. There have been many investigations done around the world to check the accuracy of these simulations, and based on these investigations, many methods have been developed. These methods are usually based on energy balance equations and can be used to test the validity or the correctness of the numerical solutions. This thesis analyzes and compares these methods based on their formulation …

Iterative Design Of The Aeroship Through Flight Testing, Michael R. Schulte

Masters Theses

This research covers the design, construction, and testing of a hybrid flight platform called the Aeroship. The Aeroship is a combination of current aerodyne and aerostat technology that have been merged at an optimal ratio. In order to create an efficient design, flight testing was employed as a catalyst for design changes. The final design was then flight tested for performance validation using videogrammetry.

Sorting Automated Concept Generator Results Based On Manufacture And Assembly Concerns, Kerry Ryan Poppa

Masters Theses

"Early in the design process, it is desirable to produce a large number of potential solutions. Completely exploring a problem's solution space is an unreasonable expectation for an unaided designer or design team. Computational tools have emerged to help designers more fully explore possible solutions. These automated concept generators use knowledge from existing designs and the desired functionality of the new product to suggest solutions. Existing automated concept generation methods produce many candidate solutions, but produce unmanageably large sets of solutions. Techniques are needed to organize the set of concepts into smaller groups, more easily parsed by the human designer. …

Sensitivity Analysis Of Relative Worth In Empirical And Simulation-Based Qfd Matrices, Robins Mathai Kalapurackal

Masters Theses

"Quality Function Deployment (QFD) is one of the most popular design tools used in product development. One of the objectives of QFD is to map customer requirements to product requirements and calculate their relative worth. A product requirement with a large relative worth indicates that it is an important product requirement in satisfying customer requirements. QFD applications use various rating scales in quantifying the degree of mapping from customer requirements to product requirements and various worth calculation methods to calculate the relative worth. The purpose of this paper is to study the sensitivity of relative worth when different rating scales …

Femtosecond Laser Micro-Structuring Of Silicon Wafer In Water Confinement, Songping Wu

Masters Theses

"This thesis investigates the use of femtosecond laser induced surface morphology on silicon wafer surface in water confinement. Unlike irradiation of silicon surfaces in the air, there are no laser induced periodic structures, but irregular roughness is formed when the silicon wafer is ablated under water. Interestingly, a particular parameter combination enables a smooth surface, which can improve the surface quality of micro-machining products. This thesis first investigates the single ablation and multi-pulse ablation processes in order to study the effects of laser parameters on ablation morphology, as well as the basic physics and mechanism of the laser-material interaction process …

Individual-Based Artificial Ecosystems For Design And Optimization, Shivakar Vulli

Masters Theses

"Individual-based modeling has gained popularity over the last decade, mainly due to the paradigm's proven ability to address a variety of problems seen in many disciplines, including modeling complex systems from bottom-up, providing relationship between component level and system level parameters, and discovering the emergence of system-level behaviors from simple component level interactions. Availability of computational power to run simulation models with thousands to millions of agents is another driving force in the widespread adoption of individual-based modeling. This thesis proposes an individual-based modeling approach for solving engineering design and optimization problems using artificial ecosystems"--Abstract, page iii.

Parameter Estimation Of Systems With Deadzone And Deadband And Emulation Using Xpc Target, Jeffrey James Lentz

Masters Theses

"The first paper presents a new approach for online parameter estimation using multiple recursive least squares estimations implemented simultaneously to determine system model parameters, as well as a deadzone and/or deadband. the online adaptive estimation scheme was verified in simulation using MATLAB Simulink and verified experimentally for a DC motor driven cart, an electro-hydraulic pilot valve system, and a free cart loosely coupled to a DC motor driven cart by a pin that fits loosely in a slot...The second paper demonstrates the use of the Mathworks xPC Target environment for validation of a control system and emulation of a physical …

Design For Manufacturing For Friction Stir Welding, Harish Bagaitkar

Masters Theses

"This thesis is divided in two parts. In the first part, technical feasibility of implementing Friction Stir Welding (FSW) for automobile chassis fabrication is discussed using a case study. In the case study, Design for Manufacturing (DFM) principles are applied to manufacture an aluminum automobile chassis. Various DFM issues such as Tool Accessibility Issue, Joint Configuration Issue, and Fixture Support Issue along with relevant guidelines such as component geometry change and component elimination are discussed in the first section. Results show that more than 50% of the chassis joints can be welded using FSW technique. The second part of the …

Fault Propagation Timing Analysis To Aid In The Selection Of Sensors Fro Health Management Systems, Jeremy Johnson

Masters Theses

"Sensor data is processed to assess performance and health of complex systems. Proper sensor selection, placement, and implementation are critical to build an effective health management system. For complex systems in which the timely assessment of the health is desired to avoid expensive consequences of failure, sensor placement is vital. The ability to identify a critical failure early is completely dependent on sensor location within the fault propagation path. A strategy for assessing a sensor suite with respect to timely critical failure detection is presented in this thesis. To illustrate the strategy, Fault Propagation Timing Analysis (FPTA) will be performed …

Indication Of Cylinder Pressure Rise Rate By Means Of Vibration And Acoustic Emissions Of An Internal Combustion Engine, Jeffery A. Massey

Masters Theses

"The focus of this study is to investigate the ability of the vibration and acoustic emissions of an internal combustion engine to indicate the cylinder pressure rise rate (PRR). Investigations are conducted on both a small-single cylinder spark-ignition (SI) engine and a larger multi-cylinder compression-ignition (CI) engine. Vibration measurements were made on both engines, however only acoustic measurements were made on the SI engine. Specific vibration and acoustic frequency bands were identified as correlating to energy generated from combustion and energy generated by cylinder cavity resonances"--Abstract, page iii.

Fabrication Of Soy Oil Epoxy Resin Based Composites, Vinay Prabhakar Pai

Masters Theses

"A renewable resource derived epoxidized ester - Epoxidized Allyl Soyate (EAS) yields a versatile epoxy resin system that can be used in pure form combination with bis-phenol epoxy systems to obtain high strength composite materials. EAS containing composites materials exhibit higher toughness and impact resistance than the traditional bis-phenol epoxy composites. These resin systems were found to be compatible with different fibers and screens such as glass fibers, glass mats, carbon fibers and metallic wire screens including those obtained from an automobile tire recycling process. The materials were tested for mechanical properties including tensile and flexure strengths. The highest tensile …

Numerical Study Of Energy Utilization In Nozzle/Plume Flow-Fields Of High-Speed Air-Breathing Vehicles, Althea Grace Wilson

Masters Theses

"Focused local energy deposition in both internal and external flow-fields associated with high-speed aerospace vehicles can provide many system level benefits. This study specifically analyzes the effects of targeted (local) energization of the flow in the nozzle and afterbody flow-field regions of a hypersonic lifting body configuration. Benefits are shown to include the generation of a favorable vehicle pitching moment (nose-down) increment associated with such energy deposition and a reduced local and overall thermal load in both combustor and nozzle for all cases examined. These results have been obtained by modeling the nozzle/afterbody region of a simple generic 2-D wave-rider/lifting …

Aflp Fingerprint Analysis Of Hybrid Salamanders In The Missouri Caverns Section Of Onondaga Cave, Maria Louise Potter

Masters Theses

"Two species and one subspecies of salamander in the genus Eurycea, two species of Plethodon and one species of Typhlotriton (recently considered to be Eurycea) salamander currently reside in an area of Onondaga Cave known as the Missouri Caverns section. Due to the presence of two known interbreeding subspecies of salamanders, Eurycea Longicauda (Long-tailed salamander) and Eurycea longicauda melanopleura (Dark-sided salamander), the possibility may exist for interbreeding of one or all of these taxa. Specifically, it is hypothesized that the two species of Eurycea longicauda may interbreed with Eurycea lucifuga (Cave salamander). through visual assessment and phenotypic analysis, …

A Separation Criterion And Non-Intrusive Thickness Measurement Technique For Shear-Driven Films, Mark A. Friedrich

Masters Theses

"The behavior of a shear-driven thin liquid film at a sharp expanding corner is of interest in many engineering applications. However, details of the interaction between inertial, surface tension, and gravitational forces at the corner that result in partial or complete separation of the film from the surface are not clear. The focus of this study was to develop a criterion to predict the onset of shear-driven film separation from the surface at an expanding corner as well as to develop a film thickness measurement technique that could be used to obtain an average film thickness for input into the …