径向夹心式压电陶瓷复合超声换能器的研究

With the developemnt of high power ultrasonics and underwater sound technology, the requirement for more power and wide action range of the transducers is becoming more and more pressing. In this project, a new type of radially sandwiched piezoelectric ultrasonic composite cylindrical transducers are presented and studied. The objective of the project is to develop a new kind of high power ultrasonic transducers with two-dimensional acoustic radiation. The transducer is composed of the radially polarized piezoelectric tubes which are sandwiched between the inner and outer metal tubes. First, the analytical theory of the radial composite piezoelectric transducer is studied. Based on the plane-stress, the plane-strain and the radial-longitudinal coupled vibration theory, the exact analytical theory and the corresponding electromechanical equivalent circuit for the thin composite transducer with small height-radius ratio, the long composite transducer with large height-radius ratio, and the short composite transducer with in-between height-radius ratio are analyzed and given. Based on the electroemchanical equivalent circuit of the composite transducer, the resonance/anti-resonance frequency equations are obtained and the relationship between the electromechanical characteristics of the transducer and the geometrical dimensions, the vibrational modes and the load impedance is analyzed and given. Second, the finite element method is used to simulate the radial vibration of the radially sandwiched piezoelectric ultrasonic transducer. By using the ANASYS and ATILIA simulation program, the vibrational mode, the frequency response, the vibrational displacement distribution and the radiated acoustic field are theoretically simulated and compared with the analytical results. Finally, the electromechanical parameters, the vibrational displacement distribution and the radiated acoustic fields are measured by using the Impedance Analyzer, the Laser vibrometer and the ultrasonic C-Scanning system and compared with the analytical and numerical results. By means of the analytical theory, the numerically simulated and the experimental results, the radially sandwiched piezoelectric ultrasonic composite transducers are optimized and the conclusions can be used in the engineering design of the composite transducers with high power and wide action range.

在功率超声以及水声技术领域，换能器的辐射功率及声波处理范围是两个重要的参数。本项目提出一种径向夹心式压电陶瓷复合超声换能器，目的在于实现换能器的二维大功率声辐射。该换能器是由径向极化的压电陶瓷圆管及金属圆管在径向复合而成。首先从理论上探讨此类换能器的解析设计理论。分别基于平面应力、平面应变以及耦合振动理论，推导薄圆环型、长圆管型以及粗短圆柱形径向夹心式压电陶瓷复合换能器的机电等效电路及共振频率方程。在此基础上探讨换能器的机电性能参数与其几何尺寸、振动模态及负载的依赖关系。其次，利用数值方法对换能器的径向振动模态、频率响应、位移分布以及辐射声场进行数值仿真，给出换能器的径向振动位移分布和辐射声场与其振动模态及负载阻抗之间的关系。最后，利用阻抗分析仪、激光测振仪及超声C扫描等测试系统对换能器的机电等效参数、振动位移及辐射声场进行实验研究，为此类换能器的优化设计提供理论及实验数据。

为了适应功率超声新技术中对超声功率和超声作用范围提出的更高要求，克服目前传统的纵向夹心式压电换能器的不足。本项目提出了一种新型的径向夹心式功率超声压电陶瓷复合换能器,在此类换能器中，其声波辐射是通过换能器的内表面或外表面在换能器的径向方向来实现的。由于换能器的圆柱形声波辐射面积可以做得很大，因而可以辐射较大的声功率。同时，径向夹心式换能器的声波辐射方向是二维的，因而可以大大地增大声波的作用范围，对大规模大容量的超声处理技术具有重要的实际意义。另外，通过合理设计此类径向夹心式压电陶瓷复合超声换能器内外金属圆柱的材料，可以实现径向夹心式压电陶瓷复合换能器的两种不同功能的声波辐射。第一，换能器的外金属圆管选用轻金属，而内金属圆管选用重金属。此时，借助于换能器几何形状和尺寸的优化设计，可以实现换能器声波能量的外向辐射。这种组合形式换能器的声波辐射是发散的，可以提高声波的作用范围，适用于低强度大作用范围的超声应用技术。第二，换能器的外金属圆管选用重金属，而内金属圆管选用轻金属。同样借助于换能器几何形状和尺寸的优化设计，可以实现换能器声波能量的内向辐射。这种组合形式换能器的声波辐射是会聚的，可以提高处理区域的声波强度，适用于小范围高强度的超声处理技术。.本项目对此类径向夹心式压电陶瓷复合超声换能器进行了系统的研究。基于平面应力、平面应变以及耦合振动理论给出了此类换能器的精确设计理论及机电等效电路,并探讨了换能器的几何形状、尺寸以及负载对其振动性能的影响。利用数值方法对换能器的径向振动模态、频率响应、位移分布以及辐射声场进行了数值仿真，给出了换能器的径向振动位移分布和辐射声场与其振动模态及负载阻抗之间的关系。利用阻抗分析仪、激光测振仪及超声C 扫描等测试系统对换能器的机电等效参数、振动位移及辐射声场进行了实验研究，为此类换能器的优化设计提供了理论基础及实验数据。