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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 …