Structure Design of Piezoelectric Harvester Based on Material Fatigue

In recent research about piezoelectric energy harvester, increasing the amplitude is usually used to improve its output power. But this approach will greatly increase the fatigue burden of the piezoelectric material and make the PZT material surface cracks and rapidly expand, which results in a significant reduction in the natural frequency of the energy harvester. It is undoubtedly devastating for the piezoelectric energy harvester with a narrow bandwidth. The surface cracks of PZT are fitted by linear spring, the equivalent model is established and the theory formula about the effect the surface cracks on the natural frequencies is derived. The limiting conditions of the structure and environment of the piezoelectric energy harvester are obtained when the crack is not expanded and some experiments are carried out to prove the theory. The results show that the natural frequency of the system will almost not change when its amplitude is less than the equivalent amplitude of 1.5 times the coercive electric field, and the natural frequency will decreased significantly when its amplitude is greater than the equivalent amplitude, and the greater the amplitude, the more obvious the decrease speed of the cracks extension.