本项目对级联式高强度压电陶瓷功率超声复合换能器进行系统的理论及实验研究。级联式换能器是由两个及两个以上的半波长压电陶瓷复合换能器在电端并联、机械端串联组合而成。该项目的重点研究内容包括：一、对级联式压电陶瓷复合换能器的振动模态，尤其是换能器的高阶振动模态进行研究，探讨换能器在不同振动模态下的机电特性。二、探讨级联式复合换能器的结构及形状尺寸对其机电振动特性的影响，为此类级联式复合换能器的优化设计提供理论基础。三、探讨级联式压电陶瓷复合换能器在单端及两端辐射情况下的机电振动特性及负载特性，为进一步发掘压电陶瓷复合换能器的大功率辐射潜能提供理论及实验数据。四、利用解析法及数值法，对级联式压电陶瓷复合换能器的耦合振动特性，包括换能器不同振动模态之间的耦合以及换能器中纵向振动与径向振动之间的耦合振动特性，进行深入的分析及探讨。该项目的研究目的在于提高传统的功率超声换能器的辐射功率及声强度。

The cascaded high-intensity piezoelectric composite high power ultrasonic transducer is proposed and studied. The cascaded transducer is composed of two or more piezoelectric composite ultrasonic transducers, which are connected together electrically in parallel and mechanically in series. The following main contents are investigated. First, the vibrational modes, espeially the higher vibrational modes of the cascaded transducers are studied, the electromechanical characteristics of the transducers at different vibrational modes are analyzed. Second, the dependency of the electromechanical characteristics of the transducers on the structure, the shape and the geometrical dimensions is studied and the optimization design of the cascaded transducer is investigated. Third, corresponding to the single-end and two-ends radiation of the composite transducer, the load characteristics of the transducer is further analyzed, and the load dependency of the efficieny, the quality factor and the effective electromechanical coupling coefficient are investigated in order to sufficiently develop the potentia of high efficiency of the piezoelectric transducer. Fourth, based on the analytical and numerical methods, the coupled vibration of the cascaded transducer will be studied. In this case, two kinds of coupled vibrations will be analyzed, one is the coupling between the different vibrationbal modes of the transducer, the other is the coupled vibration between the longitudinal vibration and the radial vibrations in the transduicer because of the Poisson's effect. The researech objective of the project is to propose and develop a new type of high-intensity piezoelectric composite power ultrasonic transducer, which can be efficiently used in high power ultrasonic applications, such as ultrasonic processing, ultrasonic oil extraction, ultrasonic metal forming, and ultrasonic liquid processing applications.