DEVELOPMENT OF DAMPING TREATMENTS FOR NEW CONSTRUCTION SUBMARINES.
SAN FRANCISCO BAY NAVAL SHIPYARD VALLEJO CALIF RUBBER LAB
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The work reported herein was a continuation of an investigation authorized by the Bureau of Ships for the purpose of developing vibration damping treatments for thick bulkheads and for webs of deep hull frames of submarines. Each tested treatment consisted of a viscoelastic layer of chromated felt, 18-inch thick, and a constraining layer of aluminum plate which was either 1, 0.5, or 0.25-inch thick, depending on the treatment. Each treatment was applied to the two flat sides of 1 34 or 34-inch thick steel bars, and was fastened to them by means of studs, nuts, and washers. Damping of flexural vibrations in the frequency range of 50 to 1500 cps was determined. It was found that damping increased linearily with the logarithm of the constraining pressure applied to the visco-elastic layer. It was also found that after applying a high constraining pressure the latter could be greatly reduced without appreciably affecting damping behavior. The highest average damping over the frequency range of 50 to 1500 cps, namely 10 of critical damping, was obtained with treatment 170, at a constraining pressure of 80 psi. This treatment consisted of a one-inch thick aluminum layer and a 18-inch thick felt layer secured to both sides of the test bar with 58-inch diameter studs. Application of high constraining pressure at the studs caused the constraining layers in some instances to bulge between the studs. This bulge tended to prevent the attainment of high damping efficiency by the treatments. Spacing of the studs affected the magnitude of the bulge. Author
- Submarine Engineering