Tests for power flow measurement and vibrational energy estimation

A test rig was built to measure power flow and estimate vibrational energy here. Both force signal and acceleration signal of the same location and direction of one point could be simultaneously captured by inserting an impedance head sensor between a vibration source and a receiver. Subsequently, the power flow entering the foundation was calculated with the time domain average method, the fundamental wave frequency domain method and the second harmonic wave frequency domain method, respectively. Experimental investigation showed that the harmonic vibration of the system should be controlled if the exciting frequency of the vibration source is the fractional double frequency of modal frequencies of the system. Because a negative value was inevitable in measurement processes of power flow, the cause of the negative power flow was explained with the theory of multi-DOF vibration. Due to the difficulty of measurement, the vibrational energy of the foundation was estimated via the driving point impedance and the mobility technique. Finally, the relationship between power flow and vibrational energy was examined with the loss factor of the system.