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Precipitation, Orientation And Composition Effects On The Shape Memory Properties Of High Strength Nitihfpd Alloys, Emre Acar
Theses and Dissertations--Mechanical Engineering
NiTiHf high temperature shape memory alloys are attractive due to their high operating temperatures (>100 oC) and acceptable transformation strain compared to NiTi. However, NiTiHf has limitations due to their lack of ductility and low strength, resulting in poor shape memory properties. In this study, Pd has been added to NiTiHf alloys in an attempt to improve their shape memory behavior. A combined approach of quaternary alloying and precipitation strengthening was used.
The characterization of a Ni45.3Ti29.7Hf20Pd5 (at. %) polycrystalline alloy was performed in compression after selected aging treatments. Transmission electron …
A Design Pathfinder With Material Correlation Points For Inflatable Systems, Jared T. Fulcher
A Design Pathfinder With Material Correlation Points For Inflatable Systems, Jared T. Fulcher
Theses and Dissertations--Mechanical Engineering
The incorporation of inflatable structures into aerospace systems can produce significant advantages in stowed volume to mechanical effectiveness and overall weight. Many applications of these ultra-lightweight systems are designed to precisely control internal or external surfaces, or both, to achieve desired performance. The modeling of these structures becomes complex due to the material nonlinearities inherent to the majority of construction materials used in inflatable structures. Furthermore, accurately modeling the response and behavior of the interfacing boundaries that are common to many inflatable systems will lead to better understanding of the entire class of structures. The research presented involved using nonlinear …
Multidimensional Modeling Of Pyrolysis Gas Transport Inside Orthotropic Charring Ablators, Haoyue Weng
Multidimensional Modeling Of Pyrolysis Gas Transport Inside Orthotropic Charring Ablators, Haoyue Weng
Theses and Dissertations--Mechanical Engineering
During hypersonic atmospheric entry, spacecraft are exposed to enormous aerodynamic heat. To prevent the payload from overheating, charring ablative materials are favored to be applied as the heat shield at the exposing surface of the vehicle. Accurate modeling not only prevents mission failures, but also helps reduce cost. Existing models were mostly limited to one-dimensional and discrepancies were shown against measured experiments and flight-data. To help improve the models and analyze the charring ablation problems, a multidimensional material response module is developed, based on a finite volume method framework. The developed computer program is verified through a series of test-cases, …