基于2-2型压电复合材料的新型宽频带径向振动超声换能器

A new broadband radial vibration ultrasonic transducer based on 2-2 piezoelectric composite material

本文提出了一种基于2-2型压电复合材料的新型宽频带径向振动超声换能器,它主要由内金属圆环和外压电陶瓷复合材料圆环组成.首先利用Newnham串并联理论和均匀场理论推导了2-2型压电复合材料的等效参数;其次利用解析法得到了金属圆环和径向极化压电复合陶瓷圆环径向振动的机电等效电路;最后得到了换能器的六端机电等效电路,从而得到了换能器的频率方程.接着分析了换能器共振频率和反共振频率以及有效机电耦合系数与几何尺寸、两相体积占比的关系,采用仿真软件对新型换能器的径向振动进行了数值模拟.结果表明,利用解析法得到的共振频率和反共振频率与数值模拟结果吻合较好.此外,对换能器在水下的辐射声场进行了仿真研究,结果表明新型复合材料径向换能器相比传统纯陶瓷径向换能器,发射电压响应幅值更大,工作带宽提高接近一倍,声匹配更佳.

Radial vibration transducer has the advantages of large radiation area,high radiation efficiency,uniform radial radiation,and wide range of action.Therefore,it is widely used in the technical fields of ultrasonic liquid treatment such as underwater acoustics,ultrasonic degradation and sonochemistry.On the other hand,the 2-2 piezoelectric composite material is one of the most commonly researched piezoelectric composite materials with the best development prospects.Compared with traditional pure piezoelectric ceramics,this new type of material has the advantages of low impedance,low mechanical quality factor,and frequency bandwidth.Therefore,in this paper we propose a new broadband radial vibration ultrasonic transducer based on 2-2 piezoelectric composite material,which is mainly composed of an inner metal ring and an outer piezoelectric ceramic composite ring.First,the Newnham series-parallel theory and the uniform field theory are used to derive the equivalent parameters of the 2-2 piezoelectric composite material.Second,the radial vibration of the combination of the metal ring and the radially polarized piezoelectric composite ceramic ring are analyzed by the analytical method.The six-terminal electromechanical equivalent circuit of the transducer is obtained,and the frequency equation of the transducer is also obtained.And then the relationship between the resonant frequency and anti-resonant frequency of the transducer,as well as the effective electromechanical coupling coefficient,geometric size,and two-phase volume ratio are analyzed.It is concluded that in order to obtain higher electromechanical conversion efficiency,the design of the transducer radius ratio should be as close as possible to 0.35.Although the higher proportion of polymer phase will lead the electromechanical conversion efficiency to decrease,it can also bring better acoustic matching ability.Therefore,the lower proportion of polymer phase can be selected in the transducer design.The finite element method is used to numerically simulate the radial vibration of the new transducer.The results show that the resonance frequency and antiresonance frequency obtained by the analytical method are in good agreement with the numerical simulation results.In addition,the acoustic field of the transducer under water is simulated numerically.The results show that compared with the traditional pure ceramic radial transducer,the new composite radial transducer has a large emission voltage response amplitude,the working bandwidth is nearly doubled,and the acoustic matching is better.