ランジュバン型ポリマー振動子の特性解明に関するWu（PD）の論文が Smart Materials and Structures に掲載されました。
J. Wu, Y. Mizuno, and K. Nakamura, “Vibration characteristics of polymer-based Langevin transducers,” Smart Mater. Struct., vol. 27, no. 9, 095013 (2018).
Our previous studies demonstrated that some functional polymers could exhibit satisfactorily low mechanical loss in high-amplitude bending vibration in the ultrasonic frequency range. In this study, to explore further applications of these functional polymers in high-power ultrasonic transducers, we focus on Langevin transducers as they are most widely employed in industrial applications. The developed transducer has a sandwich structure: piezoelectric ceramic elements are clamped between two polymer cylindrical bodies with a metal screw. The vibration characteristics of the polymer-based Langevin transducers differ from the metal-based ones owing to the difference in the material constants. When working in the 1st-order longitudinal modes, the polymer-based transducers exhibit dumbbell-shaped deformations because of the higher stiffness of the metal screws. Their mechanical losses reach the maximal values on the vibrating bodies instead of the piezoelectric ceramic elements. Besides, when the strains on polymer vibrating bodies exceed certain values, there exist sharp reductions in mechanical quality factors (Q factors), which restrict the maximal vibration velocities of polymer-based transducers. The poly phenylene sulfide (PPS)-based transducer yields Q factors of 350 and its vibration velocity linearly increases to 1060 mm s−1, comparable to the maximal values achievable on metal-based ones. These properties indicate the potential of PPS-based transducers for ultrasonic applications.