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中国物理学会期刊

基于环形声黑洞结构的弯张换能器

Analysis of flextensional transducer based on annular acoustic black hole structure

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  • 利用声黑洞结构能量聚集和弯曲波振幅放大的特性,本文提出了一种新型声黑洞弯张换能器,该换能器由内部朗之万换能器与外部声黑洞金属环组成.基于Timoshenko曲梁理论,使用传递矩阵法建立了声黑洞环的理论模型,可计算出环弯曲振动的共振频率.通过有限元法对该理论模型进行验证,进一步对换能器的电阻抗频率响应特性、振动特性、空气中的辐射声场进行仿真模拟,并与等厚度环形弯张换能器进行对比分析,其发射电压响应、最大声压均优于等厚度环形弯张换能器.最后加工了换能器样机并进行实验验证,仿真与实验结果均证明,在相同工作频率和振动模态的条件下,声黑洞结构能够提升换能器的定向辐射能力和声辐射性能.

     

    Acoustic black hole (ABH) structures possess unique properties of energy concentration and flexural wave amplitude amplification. By taking advantage of these properties, this paper proposes a novel ABH flextensional transducer, which consists of an internal Langevin transducer and an external ABH metal ring. The longitudinal vibration generated by the Langevin transducer drives the flexural vibration of the acoustic black hole ring (ABHR), thereby converting the longitudinal vibration into flexural vibration of the radiator with a large amplitude. Based on the Timoshenko curved beam theory, a theoretical model of the ABHR is established using the transfer matrix method (TMM), where the ring is circumferentially divided into 2n elements of equal thickness, enabling calculation of the resonant frequency of its flexural vibration. The accuracy of the theoretical model is verified through finite element simulations. Furthermore, the electrical impedance frequency response, vibration characteristics, and radiated sound field of the transducer in air are simulated. Compared with a ring flextensional transducer of equal thickness, the ABH transducer exhibits superior performance in terms of vibration displacement amplitude, transmitting voltage response, and maximum sound pressure. A prototype of the transducer is fabricated, and its electrical impedance and vibration characteristics are experimentally measured. These measurements agree well with the numerical simulations, verifying the reliability of the theoretical model and the numerical analysis. The results show that under the same operating frequency and vibration mode conditions, the ABH structure can enhance the sound radiation performance and directional radiation capability of the transducer. This type of ABH transducer holds promise for applications in airborne ultrasonic directional radiation and related fields.

     

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