水下宽频带声子晶体换能器的研究

Using period structure of phononic crystal to broaden the bandwidth of the underwater transducer is of great sigificance to the develpoment of underwater detection technology. In this project, phononic crystal which has special energy band structure is used to design the ultra-wide frequency band composite underwater transducer.Firstly, the transfer matrix method is used to compute the relationship between the band gap and the structure of phononic crystal and the optimal material parameters of the phononic crystal are obtained in theory. Secondly, the theory model of a composite transducer with phononic crystal head mass is setup and the effects of phononic crystal structure on the transmitting response of the transducer in work frequency band is analyzed. Thirdly, finite element method is used to simulate the vibration modal,radiation acoustic field, directivity and the transmitting response of the transducer and the law between the frequency band of transducer and the structure of the phononic crystal is obtained.Finally, the prototype transducers with different frequencies and bandwidth， which have phononic crystal head mass， are fabricated experimentally. The transmitting response level of the transducers in work frequency band are measured and then the measured results are used to optimize the structure of the transducer. The research will have some sigificance to the design of phononic crystal wide-band transducer.

宽带换能器在水声探测领域具有广阔的应用前景。声子晶体的周期结构在声学器件设计方面具有独特的优势。本项目利用声子晶体的能带特性，对压电换能器的频带宽度进行调控，揭示声子晶体展宽换能器频带的物理机理。首先，用传输矩阵方法计算声子晶体的通带和禁带随其构成材料和结构的关系，找出影响声子晶体能带的材料密度、弹性常数及声速、声阻抗等参数的最优组合；其次，建立前盖板粘结有声子晶体的复合压电换能器的理论模型，分析其结构参数对换能器的振动模态和发射响应的影响；再次，运用有限元对声子晶体换能器的振动模态、液体中的辐射声场、指向性和发射响应等进行仿真，找出换能器工作参数与声子晶体结构、材料和声学参数之间的规律，获得具有较宽频带声子晶体换能器的最优结构参数；最后通过实验制作具有不同频率和带宽的声子晶体换能器，测量换能器的发射响应级随频率的变化关系。本研究对应用声子晶体设计新型水声换能器具有理论和实际意义。

本项目系统地研究了声子晶体夹心式压电陶瓷复合换能器的结构和性能，给出声子晶体换能器的解析设计理论。首先，建立前盖板粘结有声子晶体的复合压电换能器的理论模型，得出其机电等效电路以及共振频率方程，分析其结构参数对换能器的振动模态和发射响应的影响。同时，采用有限元数值仿真，分析其结构参数对换能器的振动模态和发射响应的影响；再次，运用有限元对声子晶体换能器的振动模态、液体中的辐射声场、指向性和发射响应等进行仿真，找出换能器工作参数与声子晶体结构、材料和声学参数之间的规律，获得具有较宽频带声子晶体换能器的最优结构参数。最后，在数值仿真的基础上，通过实验制作出具有不同频率和带宽的声子晶体换能器，并且测量了换能器的发射响应级随频率的变化关系，揭示了声子晶体展宽换能器频带的物理机理。本项目所设计的声子晶体换能器的性能指标可达到目前水声对抗技术中对宽带换能器的实际应用要求。