報告題目：Nonlinear Piezoelectric Vibration for High-power Ultrasonic Devices

報告人：Prof. Takeshi Morita( The University of Tokyo)

報告時間：2018年11月29日（星期四）上午9:30

報告地點：明故宮校區9號樓506會議室

主辦單位：機械結構力學及控制國家重點實驗室、航空宇航學院、國際合作處

報告內容簡介：

It’s well-know that the nonlinearity of the piezoelectric materials limits the performance of high-power ultrasonic devices. For developing these devices, understanding of the nonlinear piezoelectric vibration is essential challenge. To clarify the nonlinear vibration mechanism of hard-type piezoelectric materials, two measurement methods, burst-mode method and admittance measurement under high power level were introduced. By comparing these results, it was found that the nonlinear terms exist only in mechanical compliance and mechanical damping in piezoelectric parameters. In other words, you can treat the force factor, the damped capacitor and the mechanical mass as constant parameters.

Based on our nonlinear model, various simulations became possible. By evaluating the nonlinear parameters, it was clarified that the CuO-doped KNN ceramic has superior performance for high-power ultrasonic transducer compared to the conventional PZT ceramic. Putting the nonlinear parameters into the transfer-matrix model, the temperature effect under high-power operation could be taken into account. It means the high-power ultrasonic transducer can be designed including the temperature distribution. Recently, this nonlinear transfer-matrix model was adapted to the Langevin transducer and good agreement was confirmed between simulation and experimental results. Our nonlinear model would be useful for the future development of the high-power ultrasonic devices.

報告人簡介：Takeshi Morita received B. Eng., M. Eng. and Dr. Eng. degrees in precision machinery engineering from the University of Tokyo in 1994, 1996, and 1999, respectively. After being a postdoctoral researcher at RIKEN (the Institute of Physical and Chemical Research) and at EPFL (Swiss Federal Institute of Technology), he became a research associate at Tohoku University in 2002 and an associate professor at the University of Tokyo in 2005. Since 2018, he has been a full professor at the University of Tokyo. His research interests include piezoelectric actuators and sensors, their fabrication processes, and control systems.