Vibration of Propeller Blades

Abstract

This is a report of vibration test for two different types of propellers. The contents may be summarized as follows. 1. Fundamental frequency of bending vibration of propeller A in air was 137.5 c/sec. 2. Difference in fundamental frequency due to material may be ascribable to the difference of E and γ. 3. Fundamental frequency in water was about a half of that in air. 4. Calculating the fundamental frequency of propeller having large expanded area ratio and pitch ratio, it was found to be necessary that fixing position to be located at about 7/8 of the span, instead of the root of blades. 5. Resonant frequency about singing phenomenon was analysed from the hammered sound at the vicinity of trailing edge of blade. This frequency remained constant, regardless of the impact position. 6. Fundamental frequency obtained by analysing the hammered noise well coincided with the result by magnet excitation. 7. It was concluded that obtaining the natural frequency by the analysis of hammered noise was a useful method. 8. It was found that resonance of stress fluctuation due to unequality of wake field to blades was hardly caused.