Piezoelectric tube with helical electrodes: Numerical analysis of actuator and energy harvesting devices

This article presents a finite element analysis of a polarized piezoelectric tube driven by helical electrodes. It is thanks to a helical coordinate meshing and local coordinate system association with each element that the problem of piezoelectric coupling has been studied. The numerical results agree well with the experimental data without the need of compensation factors as in previous works. The developed model was used to determine the electromechanical coupling coefficients of the tubes in axial and torsional modes. The electromechanical coupling coefficient depends on the helical angle of the electrode. In the axial mode, electromechanical coupling coefficient goes through a maximum value of 25% when the helical angle of the electrode is close to 30 degrees, while in the torsional mode, the maximum value of electromechanical coupling coefficient was reached at a helical angle near 60 degrees. The analysis investigates the tube size effects and shows the potential uses of piezoelectric tubes as an actuator or energy harvesting device. The presented model could be used to analyze the electric fields in the tube during the polarization process or to analyze the mechanical stress (without any limitation due to Saint-Venant's principle) imposed by the simplified analytical approaches available in the literature. The developed approach can also be used for theoretical analysis of the helical/spiral piezoelectric element.