Experimental study on long-term fatigue behavior of piezoelectric energy harvesters under high and low-frequency vibration excitation

Abstract

The strain distribution along the cantilever piezoelectric energy harvester (PEH) beam is nonuniform, which would induce fatigue damage at the root of the cantilever in the long run, and cause failure in the piezoelectric material. In this study, fatigue vibration experiments are repeated to determine and analyse fatigue characteristics and output performance changes of the improved structures under cyclic vibration with 1 m/s² acceleration at resonance frequencies of 15 Hz and 250 Hz. In the fatigue experiment, waveform distortion or large attenuation of the high-frequency PEH is not observed during 2.03 × 10⁶ cycles. It shows that the high-frequency beam structure can protect the piezoelectric patch, which is susceptible to fatigue, from mechanical cracks to improving the lifetime of the PEH. Unlike the high-frequency PEH beam, the low-frequency PEH beam underwent final failure at the middle of the piezoelectric transducer after 3.1 × 10⁵ cycles. The result indicated that high-frequency PEH exhibits better fatigue characteristics and reliability in the complex vibration environment of the drive motor, while the fatigue strength of low-frequency PEH still needs further optimization and research. This work provides a deep insight into the reliability of the designed high-low frequency beams for piezoelectric energy harvesting on driving motor system (DMS) of electric vehicles. It will provide a reference for future studies on improving the structure reliability and electric output of PEH when working on actual working conditions.