Research On Cascaded Piezoelectric Ceramic Transducers

Ultrasonic transducer is an energy conversion device that converts electric energy and acoustic energy into each other.It is one of the important parts of power ultrasonic technology.Sandwich piezoelectric ceramic transducers are widely used in ultrasonic machining,ultrasonic cutting,ultrasonic welding,ultrasonic cleaning and other fields due to their excellent performance.In order to better improve the performance of the transducer,based on the traditional sandwich piezoelectric ceramic transducer,the cascaded piezoelectric ceramic transducer is proposed in this paper.It consists of three longitudinal sandwich piezoelectric ceramic transducers which connect mechanically in series and electrically in parallel.Due to unique structure and connection method of cascaded piezoelectric ceramic transducer,sound power and sound intensity can be multiplied simultaneously,and its heat dissipation performance and electro-acoustic efficiency are also improved to a certain extent.Since the longitudinal dimension of the cascaded piezoelectric ceramic transducer is much larger than the radial dimension,one-dimensional theory of the transducer can be used to analyze and study the cascaded piezoelectric ceramic transducer.The research work of this paper mainly includes the following:(1)As the core and key piezoelectric materials of the piezoelectric transducers are briefly introduced.The one-dimensional longitudinal vibration of the variable cross-section thin rod and axial polarization of the piezoelectric ceramic stack are analyzed.The equation of state and equivalent circuit for the one-dimensional longitudinal vibration of the variable cross-section thin rod and axial polarization of the piezoelectric ceramic stack are derived.It provides a theoretical basis for theoretically analyzing the electromechanical equivalent circuit and frequency equation of the cascaded piezoelectric ceramic transducer.(2)Combining the research of the equivalent circuit of the variable cross-section thin rod and the piezoelectric ceramic stack,ignoring the mechanical loss,dielectric loss and load,based on the one-dimensional theory of the transducer,the electromechanical equivalent circuit of the cascaded piezoelectric ceramic transducer is obtained.The resonance frequency equation and anti-resonance frequency equation of the cascaded piezoelectric ceramic transducer are derived,and the effective electromechanical coupling coefficient is obtained.The theoretical relationships between the geometrical dimension of the cascaded piezoelectric ceramic transducer and resonance frequency,anti-resonance frequency and effective electromechanical coupling coefficient are discussed.The optimal design theory is obtained for the cascaded piezoelectric ceramic transducer.The finite element method is used to simulate the vibration modes of cascaded piezoelectric ceramic transducers with different sizes.The theoretically calculated resonance frequency and anti-resonance frequency are compared with the simulated results.The results obtained by the two are consistent;the correctness of theoretical model of the one-dimensional vibration of the cascaded piezoelectric ceramic transducer is verified.(3)Based on the electromechanical equivalent circuit of the cascaded piezoelectric ceramic transducer ignoring the mechanical loss,dielectric loss and load,the cascaded piezoelectric ceramic transducer considering mechanical loss,dielectric loss and load is further analyzed.The electromechanical equivalent circuit is obtained.The resonance frequency equation and anti-resonance frequency equation are derived,and then the effective electromechanical coupling coefficient and mechanical quality factor are derived.By electromechanical equivalent circuit,the electro-acoustic efficiency of the cascaded piezoelectric ceramic transducer is derived.The theoretical relationships between performance parameters of cascaded piezoelectric ceramic transducer and mechanical loss,dielectric loss,geometrical dimension and load are discussed.The optimal design theory is obtained for the cascaded piezoelectric ceramic transducer.Three cascaded piezoelectric ceramic transducers are measured by Precision Impedance Analyzer.The experimental results are compared with the theoretically calculated results.The correctness of theoretical derivation and conclusions is further verified.