In this paper, the results of several tests concerning possible application of piezoelectric elements to reduce torsional vibrations of a beam are presented and discussed. The proposed method of application is a novel one. The piezoelectric elements are positioned in two pairs and glued to the beam at the chosen cross-section. These elements are activated using a harmonically varying voltage of the same amplitude and opposite in phase. Simulations are performed regarding the active reduction of the lowest natural frequencies of vibration of the xed-free beam with the use of piezoelectric actuators. The results of these simulations are obtained by means of the nite element method (ANSYS).

Beams with rectangular cross-section, with large length-to-width ratio, can be excited to torsional vibrations. If the piezoelectric elements are mounted to the beam in pairs at the same cross-section with two separated elements positioned on the same side of the beam, and the voltages applied to them are in the opposite phase, they produce twisting moments which can be applied to reduce the torsional vibrations. Results of FEM simulations are presented and analysed in the paper. All analyses are performed for a steel free-clamped beam. The piezoelectric elements made of PZT material are mounted in pairs on one side of the beam. The analyses are done for separated natural modes.

In the paper, the analytical solution of excited torsional vibrations of prismatic thin-walled beams for different types of boundary conditions and different types of external excitation of torsional moment are formulated. The presented solution can be applied, among others, to preliminary analysis of the optimal position of the actuators and the value of the applied voltage to the elements for minimization of the vibrations of the beams.