Date of Award


Document Type


Degree Name

Master of Science


Department of Aeronautics and Astronautics

First Advisor

Anthony N. Palazotto, PhD


This project compares the damping and fatigue life of bare titanium plates to those coated with magnesium aluminate spinel (mag spinel). Two different coating thicknesses were tested: .005" per side and .010" per side (total thicknesses of .010" and .020"). Dynamic ping tests were conducted on all specimens to determine their resonance frequencies. Laser vibrometry was used to determine the mode at each resonance frequency. Damping ratios were determined through the use of sine sweeps. A vibration mode was selected at which to fatigue the specimens, and the stress pattern was analyzed utilizing the Stress Pattern Analysis by Thermal Emissions (SPATE) process. Once characterization was complete, fatigue testing was conducted on the thick plates utilizing the resonant dwell process. The specimens were vibrated by applying a harmonic excitation through the base. The strain level which would result in fatigue at 106 cycles, and the velocity necessary to achieve this strain were determined. The test specimens were excited at this velocity, and the number of cycles to failure was noted. Results were compared for the uncoated, thin coated, and thick coated specimens.

AFIT Designator


DTIC Accession Number