Radial Vibration Study Of Radial Compound Ring Ultrasonic Transducer

The radial ring piezoelectric ultrasonic transducer with the characteristics of simple structure,wide radiation range,high radiated ultrasonic power,and non-directivity,has broad application prospects in the fields of ultrasonic medical imaging,underwater acoustic communication and energy harvesting.In this paper,based on the traditional radial ultrasonic transducer,two different types of ring transducers are analyzed from three aspects:theoretical analysis,finite element simulation and experimental test.Since the radial dimensions of the two transducer models are much larger than their axial height,the equivalent circuits of metal ring type vibrators and piezoelectric ceramic ring type vibrators can be deduced by plane stress theory.Then according to the conditions of continuous external force and displacement at the interfaces between the piezoelectric ceramic ring type vibrator and the metal ring type vibrators,the equivalent circuits of the two types of ring transducers are obtained.The specific research contents of this paper are as follows:(1)In Chapter 2,according to the height expression h=h0r,the equivalent circuit of the radial vibration of a metal ring type vibrator with a conical section is derived.The analytical theories of a metal ring with equal section and two types of polarized piezoelectric ceramic ring type vibrators are introduced in detail.The derivation of the equivalent circuits in Chapter 2 provide a theoretical basis for the derivation of the electromechanical equivalent circuits of the two transducer models in Chapters 3 and 4.(2)In Chapters 3,the electromechanical equivalent circuit of radial composite ultrasonic transducer with conical section is obtained by theoretical analysis.According to the relation of total input electrical impedance of the tranducer with conical section,the resonance frequency equation and anti-resonance frequency equation of the transducer with conical section are derived.And then the effective electromechanical coupling coefficient(Keff)of the transducer in resonant modes is obtained by the resonance frequency(fr)and anti-resonance frequency(fa).Based on theoretical derivation,the relationships between the materials and geometric dimensions of the transducer and fr,fa and keff are theoretically analyzed.The analysis results provide a theoretical basis for the performance optimization of the transducer with conical section.Through the finite element simulation,the radiated sound power and beam directivity of the transducer with conical section are compared with the transducer with equal section,which proves the superiority of the transducer with conical section.A transducer with conical section model is designed and fabricated,and the resonance frequency and antiresonant frequency of the transducer are tested experimentally.The results of analytical theory,numerical simulation and experiment test are compared,the three results were consistent,which proves the correctness of the theoretical deduction.(3)In Chapter 4,the electromechanical equivalent circuit of radial cascaded ultrasonic transducer with conical section is obtained by theoretical analysis.According to the relation of total input electrical impedance of the radial cascaded tranducer,the resonance frequency equation and anti-resonance frequency equation of the radial cascaded transducer are derived.And then the effective electromechanical coupling coefficient(Keff)of the transducer in resonant modes is obtained by the resonance frequency(fr)and anti-resonance frequency(fa).Based on theoretical derivation,the relationships between the radial geometric dimension,positions of the piezoelectric ceramic thin rings and fr,fa and keff are theoretically analyzed.The analysis results provide a theoretical basis for the performance optimization of the radial cascaded transducer.Through finite element simulation,the effective electromechanical coupling coefficients of the radial cascaded composite transducer are compared with those of the traditional radial composite transducer of the same dimension.It is clear that when the transducer is vibrating at the first order and the second order,the effective electromechanical coupling coefficient of the radial cascaded composite transducer is much larger.Two radial cascaded transducer models are designed and fabricated,and the resonance frequencies and anti-resonant frequencies of the transducers are tested experimentally.The results of analytical theory,numerical simulation and experiment test are compared,the three results were consistent,which proves the correctness of the theoretical deduction.