Affiliations: Department of Aeronautics and Astronautics: Air Force
Institute of Technology, 2950 Hobson Way, Building 640, WPAFB, OH 45433-7765,
USA | Department of Mathematics and Statistics: Air Force
Institute of Technology, 2950 Hobson Way, Building 640, WPAFB, OH 45433-7765,
USA
Abstract: A novel vibration experiment consisting of a free-free boundary
condition, an electromagnetic excitation source, a vacuum chamber, and a laser
vibrometer based surface measurement system has been developed that permits
high levels of excitation on highly damped specimens with a minimal amount of
unwanted systematic error. While some of the aspects of this experiment are not
unique, when combined with a processing technique that accounts for the
nonlinearities present in the system, this experiment permits, accurate
measurement of strain dependent stiffness and damping properties of hard
coatings at high strain levels. This procedure has been demonstrated using a
titanium beam that has been coated with a free-layer damping treatment of
Magnesium Aluminate Spinel. The results indicate that Magnesium Aluminate
Spinel has both nonlinear stiffness and damping properties. The stiffness
asymptotes to a minimum value around 650 microstrain while the damping is a
maximum around 100 microstrain. Additionally, the data contained herein cover a
larger strain range for this material than previously reported.
