High Frequency Response of a Ring-Stiffened Cylinder.
DEFENCE RESEARCH ESTABLISHMENT ATLANTICDARTMOUTH (NOVA SCOTIA)
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Power Flow Finite Element Analysis PFFEA has been under development at Defence Research Establishment Atlantic DREA in support of the Ship Noise Project. PFFEA is an analysis method for predicting high frequency structural acoustic and vibration response. The method is based on a vibrational conductivity approach in which the flow of vibrational energy is modelled in a similar fashion to heat conduction with convective losses. This report discusses experiments performed with DREAs 3m ring-stiffened cylinder to assist in the validation of the PFFEA software for high frequency structural vibrations. The experiments involved excitation of the cylinder structure at relatively high frequencies using an electromagneticpiezoelectric shaker located on either the cylinder shell or one of the ring-stiffeners. Both the input power and the response of the cylinder were measured with both harmonic and broadband excitation using an accelerometer. The power flow predictions for either input mobility harmonic case or input power broadband case did not correlate well with the measured data. The measured applied forces were used as input to predict the response of the cylinder to both harmonic and broadband excitation. Not unexpectedly, the predicted harmonic response did not compare favourably with the measured values in the frequency ranges dominated by modal behaviour however, predictions were better at the higher frequencies where the response is not modal. The broadband predictions were more accurate for both locations of the shaker. The 13-octave band predictions were more accurate for the shaker on the shell and for both locations the results were better at high frequencies.
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