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Design And Validation Of A High-Lift Low-Pressure Turbine Blade, Mark W. Mcquilling
Design And Validation Of A High-Lift Low-Pressure Turbine Blade, Mark W. Mcquilling
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This dissertation is a design and validation study of the high-lift low-pressure turbine (LPT) blade designated L2F. High-lift LPTs offer the promise of reducing the blade count in modern gas turbine engines. Decreasing the blade count can reduce development and maintenance costs and the weight of the engine, but care must be taken in order to maintain turbine section performance with fewer blades. For an equivalent amount of work extracted, lower blade counts increase blade loading in the LPT section. The high-lift LPT presented herein allows 38% fewer blades with a Zweifel loading coefficient of 1.59 and maintains the same …
Particle Based Plasma Simulation For An Ion Engine Discharge Chamber, Sudhakar Mahalingam
Particle Based Plasma Simulation For An Ion Engine Discharge Chamber, Sudhakar Mahalingam
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Design of the next generation of ion engines can benefit from detailed computer simulations of the plasma in the discharge chamber. In this work a complete particle based approach has been taken to model the discharge chamber plasma.This is the first time that simplifying continuum assumptions on the particle motion have not been made in a discharge chamber model. Because of the long mean free paths of the particles in the discharge chamber continuum models are questionable. The PIC-MCC model developed in this work tracks following particles: neutrals, singly charged ions, doubly charged ions, secondary electrons, and primary electrons. The …
Robust Estimation Of Reliability In The Presence Of Multiple Failure Modes, Phani R. Adduri
Robust Estimation Of Reliability In The Presence Of Multiple Failure Modes, Phani R. Adduri
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In structural design, every component or system needs to be tested to ascertain that it satisfies the desired safety levels. Due to the uncertainties associated with the operating conditions, design parameters, and material systems, this task becomes complex and expensive. Typically these uncertainties are defined using random, interval or fuzzy variables, depending on the information available. Analyzing components or systems in the presence of these different forms of uncertainty increases the computational cost considerably due to the iterative nature of these algorithms. Therefore, one of the objectives of this research was to develop methodologies that can efficiently handle multiple forms …
Dissipated Energy At A Bimaterial Crack Tip Under Cyclic Loading, Jeremy S. Daily
Dissipated Energy At A Bimaterial Crack Tip Under Cyclic Loading, Jeremy S. Daily
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A new theory of fatigue crack growth in ductile solids has recently been proposed based on the total plastic energy dissipation per cycle ahead of the crack. This, and previous energy-based approaches in the literature, suggest that the total plastic dissipation per cycle can be closely correlated with fatigue crack growth rates under mode I loading. The goal of the current research is to extend the dissipated energy approach to steady-state crack growth under mixed-mode I/II loading conditions, with application to cyclic delamination of ductile bimaterial interfaces. Such systems can occur in brazing, soldering, welding, and a variety of layered …
Characterizing Battlefield Human Decision Making With Value Focused Thinking And Reliability Modeling, Fawaz Al-Karaeen
Characterizing Battlefield Human Decision Making With Value Focused Thinking And Reliability Modeling, Fawaz Al-Karaeen
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Military officers and soldiers in combat are faced with complex, time-critical decision problems. The battlefield, or combat, environment involves decisive operations under unpredictable and rapidly changing conditions. Decisions in battlefields take place under uncertain, time constrained conditions and in a tactical environment. A battlefield decision maker encounters a dynamic information environment. During combat, individuals gather and consider information from a variety of sources to determine what information is reliable and useful, and what information is not. There is a clear correlation between the decision making process and the value of information feeding that process. This research examines a decision making …
The Effect Of Process Variables On Microstructure In Laser-Deposited Materials, Srikanth Bontha
The Effect Of Process Variables On Microstructure In Laser-Deposited Materials, Srikanth Bontha
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The ability to predict and control microstructure in laser deposition processes requires an understanding of the thermal conditions at the onset of solidification. The focus of this work is the development of thermal process maps relating solidification cooling rate and thermal gradient (the key parameters controlling microstructure) to laser deposition process variables (laser power and velocity). The approach employs the well-known Rosenthal solution for a moving point heat source traversing an infinite substrate. Cooling rates and thermal gradients at the onset of solidification are numerically extracted from the Rosenthal solution throughout the depth of the melt pool, and dimensionless process …
Topology Optimization Of Engine Exhaust-Washed Structures, Mark A. Haney
Topology Optimization Of Engine Exhaust-Washed Structures, Mark A. Haney
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Aircraft structure subjected to elevated temperature and acoustic loading present a challenging design environment. Thermal stress in a structural component has typically been alleviated by allowing thermal expansion. However, very little work has been done which directly addresses the situation where such a prescription is not possible. When a structural component has failed due to thermally-induced tensile stresses, the answer to the question of how best to stiffen the structure is far from trivial. In this work, we demonstrate that conventional stiffening techniques, for example, those which add material to the thickness of a failing panel, may actually increase the …
Nano-Coatings On Carbon Structures For Interfacial Modification, Rajasekhar Venkata Pulikollu
Nano-Coatings On Carbon Structures For Interfacial Modification, Rajasekhar Venkata Pulikollu
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Surface modification of materials is a rapidly growing field as structures become smaller, more integrated and complex. It opens up the possibility of combining the optimum bulk properties of a material with optimized surface properties such as enhanced bonding, corrosion resistance, reactivity, stress transfer, and thermal, optical or electrical behavior. Therefore, surface functionalization or modification can be an enabling step in a wide variety of modern applications. In this dissertation several surface modification approaches on carbon foam and carbon nano-fibers will be discussed. These are recently developed sp 2 graphitic carbon based structures that have significant potential in aerospace, automotive …