Elusidation of the mechanism of the "jumping and dropping effect near the mechanical resonance of a piezoelectric element and the solutions to its technical problems

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K04341
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 20010:Mechanics and mechatronics-related
• Research Institution: Yamagata University
• Principal Investigator: Adachi Kazunari 山形大学, 大学院理工学研究科, 教授 (00212514)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 圧電セラミック / 「跳躍・降下現象」 / 不安定現象 / 機械共振周波数 / 電気機械振動変換器 / 非線形振動

Outline of Final Research Achievements

The peculiar events called the “jumping and dropping” phenomena of piezoelectric ceramic vibrators in high amplitude operation have widely been known. The phenomena, which occur solely in the vicinity of the mechanical resonance frequencies of the vibrators, are the emergence of hysteresis in frequency domain with abrupt increase and decrease of the vibratory amplitude. It has long been believed that the third-order elastic nonlinearity of the piezoelectric materials is the dominant cause of the unstable vibratory behaviors. Nevertheless, in this research, it has been found that they can be attributed to the local piezoelectric polarization reversals due to the electric field concentration caused by its conspicuous distortion inside the vibrators in mechanical resonance. The validity of this hypothesis has been verified by numerical and experimental investigations for hard-type piezoelectric ceramics, but regrettably it has not for soft-type piezoelectric ceramics yet.

Free Research Field

超音波工学

Academic Significance and Societal Importance of the Research Achievements

多くに強力超音波の工業的応用においては、大振幅の超音波振動を高効率に発生させるため、圧電セラミック振動子を共振状態で駆動しなければならないが。最も効率が良いはずのその機械共振周波数で駆動しようとすると、「跳躍・降下現象」と呼ばれる不安定現象が起き、動作が安定しなくなる。そのため多くの実用強力超音波応用機器では、出力インピーダンスが非常に高い定電流源とみなせる駆動回路を使って、効率と安全性を犠牲にして、高電圧での駆動をせざるを得ない。本研究の成果は、そうした問題を解決する知見を与えることで、強力超音波応用技術の適用範囲を医学的治療の領域などでより拡大させることに寄与することが期待される。