Robert J. Unglenieks
Robert J. Bernhard
School of Mech. Eng., Purdue Univ., 1077 Ray W. Herrick Lab., West Lafayette, IN 47907-1077
Recently, a number of investigators have proposed so-called energy flow analysis techniques to allow engineers to perform high-frequency structural vibration studies of coupled structural elements. One key parameter required for this analysis is the power transmission and reflection coefficients of the joints that couple structural elements. A wave-number domain technique has been developed which uses a spatial fast Fourier transform to transform velocity data obtained in the spatial/frequency domain into the wave-number/frequency domain. The resulting wave-number domain spectrum allows estimation of energy flow segregated into right and left traveling components. Using the segregated energy flows for all of the structural elements coupled at a joint, it is possible to estimate the power transmission and reflection coefficients of the joint. A ladder frame structural system is analyzed to determine the flexural wave power transmission and reflection coefficients of ell- and tee-joints that comprise the structure. The structure is forced so that only flexural and longitudinal waves are excited. A scanning laser Doppler vibrometer is used to collect the flexural wave velocity data. The estimates of the joint coefficients are presented and compared to the analytical values for rigid joints.