M.Sc Thesis

M.Sc StudentMoldavsky Jonathan
SubjectAnalytical Models for Prediction of Energy Production
by Piezoelectric Materials
DepartmentDepartment of Aerospace Engineering
Supervisor ASSOCIATE PROF. Haim Abramovich
Full Thesis text - in Hebrew Full thesis text - Hebrew Version


Recent advancements in the sphere of micro scale technologies and wireless communication greatly increased the demand for small, long-lasting and portable sources of energy. A significant amount of research demonstrates the feasibility and effectiveness of using PZT materials as alternative power sources via converting ambient mechanical vibrations into electrical power. In order to extract a maximum power from the environment (with the dynamic range of mechanical vibrations), the frequency of excitation is to be equal to the undamped natural frequency of the structure.

To maximize the amount of energy scavenged from ambient vibrations of the PZT material embedded in composite beams small cross-sectional dimensions with high natural frequencies should be used. There is no accurate analytical model for this. Hence, the purpose of this study was to develop the advanced structural model composed of Timoshenko beam coupled with a pair of the PZT patches with different boundary conditions and examine the effect of various factors on a maximal feasible amount of power that can be harvested from the free vibration. The model takes into account the effect of rotary inertia and transverse shear deformations.

The numeric solution for beam vibrations was calculated with a varying-step algorithm that significantly decreased the solution time. A calculation of the maximal power was based on the assumption that maximal allowed strain deformation for the PZT material did not exceed 1000 [με].

A comprehensive formula for calculating maximal amount of power was developed. For a particular case of beams with the hinged-hinged boundary conditions and high L/h ratio a simplified and accurate formula was constructed. Different factors were tested parametrically (e.g. the interactions between the composite material of the structure and the PZT material was tested in order to find an optimal place for the PZT patches on the carrying beam, the impact of the boundary conditions, fiber orientations, characteristics of materials utilized for the patches and for the beam, beam’s thickness, etc.). Also, the influence of the above factors on the natural frequency and on the generated power was examined. It was proven that to calculate the exact amount of power harvested from the ambient vibration of the beam with small cross-sectional dimensions, an accurate model that takes into account an effect of transverse shear deformation on the vibratory motion of the beam should be used.