Naval Postgraduate School
Calhoun, Institutional Archive of the Naval Postgraduate SchoolNot a member yet
71232 research outputs found
Sort by
COLD SPRAY ALUMINUM 7075 FUNCTIONALLY GRADED COATING REINFORCED WITH BORON NITRIDE NANOPLATELETS AND VARYING VOLUMETRIC BORON CARBIDE LOADS
No full textCold spray additive manufacturing (CSAM) is a rapidly growing technology with numerous industrial applications that has yet to be fully utilized in the Department of Defense (DoD). CSAM has been shown to deposit aluminum coatings onto many surfaces including aluminum alloys like AA7075, which the DoD uses extensively. This specific alloy has been used in many of its aerospace applications due to its excellent specific strength, fatigue resistance, and relative light weight, while being cost efficient. However, AA7075 is susceptible to abrasion due to having low wear resistance. Previous studies confirm that one of the most effective strategies to enhance the wear performance is incorporating ceramic reinforcements into the aluminum matrix. Boron carbide has been highly researched as a reinforcement for being one of the hardest materials known and exhibiting high wear resistance. Yet the harmonious effects of combining different ceramic reinforcements together in a cold spray functionally graded coating using nitrogen gas are unexplored. In this work, an AA7075 functionally graded coating was created by incorporating various nanoscopic and microscopic particles, including boron carbide, to enhance the coating’s mechanical properties. By changing the concentrations of boron carbide and boron nitride nanoplatelets throughout the coating layers, the specific wear rate reduced 45.5% and the wear track depth reduced 24%; exemplifying improvements in hardness and wear resistance.Distribution Statement A. Approved for public release: Distribution is unlimited.Lieutenant, United States Nav
DEVELOPMENT AND VALIDATION OF FUNCTIONAL FAILURE CRITERIA
No full textThe scope of this thesis was to validate the functional failure criteria developed by Kwon and Didoszak through physical experimentation. When there is no major visible structural failure, but the equipment cannot operate as intended, we call this functional failure. If functional failure can be developed and validated, it could change how civilian and military manufacturers design for vast dynamic loading conditions. The tested failure systems were the Monoprice Cadet 3D printer (MP) and the Dual Cantilever Beam Box (DCBB). Utilizing the Compressed Air Shock Pipe Underwater Release (CASPUR) system, high-impact shock was applied to these systems, and the dynamic response was measured using accelerometers. The maximum velocities and maximum change in displacement were calculated and plotted from this data. The results showed that failure was observed when the maximum velocity and maximum change in displacement were equal to or larger than their critical value limits, respectively. This consistent correlation validated and proved that new failure criteria can enhance the current guidelines outlined in MIL-S-901E and MIL-STD-167-1A. These findings will not only revolutionize the testing procedures used for shock verification within the Department of the Navy but also enhance the survivability of internal components within naval vessels.Distribution Statement A. Approved for public release: Distribution is unlimited.Outstanding ThesisLieutenant, United States Nav
HOT WIRE ANEMOMETRY IN COLD MACH 4 FLOW
Get PDFThe Naval Postgraduate School operates a cold-flow Mach 4 supersonic wind tunnel, which was renovated in 2022 to improve flow conditioning. Following the upgrades, flow recharacterization was conducted with an emphasis on quantifying turbulence, with turbulence intensity identified as the primary metric. A Dantec constant temperature anemometer was used to determine freestream turbulence intensity by traversing a probe laterally across the test section centerline at locations of known Mach number. Data were collected at 170 kHz and 1 MHz. Calibration using the boundary layer velocity profile was attempted but was unsuccessful due to an advection gradient between the freestream and boundary layer, which prevented accurate conversion of voltage to velocity. As a result, raw voltage fluctuations were analyzed directly to estimate pseudo turbulence intensity. The 170 kHz data yielded a pseudo turbulence intensity of 0.718%, while the 1 MHz data yielded 0.521%. Frequency domain analysis of the 1 MHz data revealed a 100 Hz flow structure present in the freestream but absent in the boundary layer. While traditional turbulence intensity values were not obtained, the study provided a practical methodology for estimating turbulence intensity using hot-wire anemometry in cold, constant-Mach supersonic wind tunnels.Distribution Statement A. Approved for public release: Distribution is unlimited.Outstanding ThesisEnsign, United States Nav
COMMAND CLIMATE AND THE EFFECTS ON RETENTION
Get PDFThe Marine Corps has struggled to retain the Marines needed and thus meet the retention mission that is critical for maintaining necessary end strength. This research identifies command climate variables that could affect the retention rate and analyzes related data to better understand retention dynamics within the Marine Corps. The researcher collected command climate and retention data from various sources in the Marine Corps and utilized correlation, variance, and regression analysis to determine the relationship between command climate and retention. The data analysis showed a positive correlation between command climate and retention. However, the regression analysis showed that this relationship is not statistically significant as defined by the standard P-value and the null hypothesis could not be rejected. The literature examines both command climate or retention and offers solutions to improve upon them but does not address the problem of USMC retention as it relates to the relationship between command climate and retention. This research makes an important contribution to the body of knowledge on variables related to retention rates in the USMC and by supporting an important relationship between command climate and retention.Distribution Statement A. Approved for public release: Distribution is unlimited.Outstanding ThesisMajor, United States Marine Corp
Faces of NPS: Lt. Cmdr. Hans Lauzen, USN
Get PDFFaces of NPS features interviews spotlighting the students, faculty, staff and alumni of our Nation's premier defense education and research institution
Faces of NPS: Timothy Shives, PhD
No full textFaces of NPS features Interviews spotlighting the students, faculty, staff and alumni of our Nation’s premier defense education and research institution
Faces of NPS: Lt. Pasquale Anthony Cassese, USN
No full textFaces of NPS features interviews spotlighting the students, faculty, staff and alumni of our Nation's premier defense education and research institution
Faces of NPS: Lt. Angelia O'Toole, USN
No full textFaces of NPS features Interviews spotlighting the students, faculty, staff and alumni of our Nation’s premier defense education and research institution.Link to video can be found at: https://youtu.be/_40dyi85iYc?si=YZg4l4HAOs0ypty
Faces of NPS: Lt. Col. Jennifer Nolta, USAF
Get PDFFaces of NPS features interviews spotlighting the students, faculty, staff and alumni of our Nation's premier defense education and research institution
METHODS FOR ESTIMATING MICROGRID RESILIENCE FOR THE DOD
No full textA microgrid is a local power grid that may be installed to manage and distribute power at military installations, either as a backup system when a grid outage occurs or as a primary system for day-to-day use. One of the Department of Defense (DoD) objectives for military microgrids is to develop resilient systems that can withstand events that may reduce operational capabilities, such as severe weather events and attacks from adversaries. While some initial metrics for resilience have been introduced in the literature for resilient microgrid design, further work is needed to develop a metric that captures DoD resilience considerations and requirements effectively. We construct a set of test cases to evaluate both existing and new resilience metrics to identify their strengths and weaknesses for microgrid design. We find that one of our new metrics measures resilience in a particularly effective way, compared with both the other metrics we introduce and existing metrics. We couple these metrics with methods we introduce to consider multiple times at which a disturbance may occur. Our approach provides decision-makers with better information regarding the strengths and weaknesses of potential microgrid designs prior to infrastructure investment. We recommend this work be incorporated into Microgrid Planner, an open-source software platform, to support future DoD microgrid planning.Distribution Statement A. Approved for public release: Distribution is unlimited.Ensign, United States Nav