夹心式径向振动压电超声换能器研究

发布时间：2018-07-03 10:07

本文选题：径向振动压电换能器 + 等效电路　；参考：《浙江师范大学》2014年硕士论文

【摘要】：功率超声换能器是电能与声能(或机械能)互为转换的一种超声设备。在功率超声技术领域应用较广的是夹心式纵向振动压电超声换能器,这类换能器的设计理论基本完善。为满足应用的需求,发展起来一类大功率径向复合压电换能器,由于该类径向复合超声换能器的功率密度大、声辐射效率高、径向声辐射指向性均匀,因此在液体超声处理领域中的应用前景十分广阔,并逐渐成为该领域的研究热点。目前有不少学者对两元或者三元径向复合压电换能器的径向振动、纵径耦合振动模式进行了一定研究,但这类换能器基本采用热胀冷缩法进行装配,需要较高的加工工艺,且预应力大小、均匀性不容易控制,热稳定性仍需提高。本文针对上述大功率换能器应用中存在的问题,对三元径向复合压电换能器进行了改进和初步研究。径向复合换能器主要由三部分组成：内外层均为金属预应力管,中间层为压电陶瓷晶片。不同的是,本文中单层结构的径向复合换能器中的压电单元采用的是压电薄圆片环形排列而成。根据夹心式纵向振动压电换能器的理论设计,本文对这类三元径向振动压电换能器还做了进一步改进,提出了层叠式三元径向复合压电换能器。为了使复杂的装配工艺简单化以及解决预应力均匀性等问题,本文将内部金属预应力管替换为一种柱形弹性膨胀内芯,该内芯不需要高精度的热加工,可随意拆卸。本文通过理论、有限元法以及实验对单层和双层压电陶瓷三元径向复合超声换能器的径向振动特性分别进行了分析,实验测试值与理论结果基本一致。具体进行了如下的工作： 1.分别对各向同性的金属薄圆盘、薄圆环以及薄壁短管径向振动特性进行了简要的研究。由机电类比原理,得到了各组分的等效电路、共振频率方程。 2.对单层压电陶瓷三元径向复合压电超声换能器的径向振动特性进行了研究,导出了分割处理的压电陶瓷管准厚度模振动机电等效电路,通过连续边界条件,进而得到了换能器的径向振动等效电路及频率方程。探讨了换能器的性能参数与其管壁厚度、压电陶瓷位置之间的关系。 3.根据夹心式纵向振动压电换能器的设计方法,在单层结构基础上,提出了复合层(一般为偶数层)夹心式径向振动压电超声换能器。由网络级联理论得到了复合层压电陶瓷晶的准厚度振动机电等效电路模型,从而建立了夹心式径向振动压电换能器的机电类比电路,得出了其共振、反共振频率方程。分析了该换能器第一、二阶径向共振频率、有效机电耦合系数与其几何尺寸之间的依赖关系。 4.利用ANSYS有限元仿真软件,对夹心式径向复合压电换能器的径向振动进行了模态分析。在理论和有限元分析的基础上,分别制作加工了几个管壁厚度不同的单层及双层压电陶瓷径向复合换能器样品,对其共振频率进行了实验测试。结果表明,理论计算与有限元仿真结果以及实验测试结果基本符合。
[Abstract]:The power ultrasonic transducer is a kind of ultrasonic equipment which converts between the electric energy and the sound energy (or the mechanical energy). It is widely used in the field of power ultrasonic technology, the sandwich type longitudinal vibration piezoelectric ultrasonic transducer, the design theory of this type of transducer is basically perfect. In order to meet the demand of the application, a kind of high-power radial composite piezoelectric transducer is developed. Because of the high power density, high efficiency of sound radiation and uniform directivity of radial sound radiation, the radial composite ultrasonic transducer is widely used in the field of liquid ultrasonic treatment, and has gradually become a hot topic in this field.
At present, a lot of scholars have studied the radial vibration and longitudinal coupling vibration mode of the dual or three element radial composite piezoelectric transducer. However, this type of transducer basically adopts the heat expansion and contraction method to assemble. It needs higher processing technology, and the size of prestress is not easy to control, and the thermal stability needs to be improved.
In this paper, in view of the problems existing in the application of the high power transducer, the three element radial composite piezoelectric transducer is improved and preliminarily studied. The radial composite transducer consists mainly of three parts: the inner and outer layers are all metal prestressing tubes and the middle layers are piezoelectric ceramic wafers. According to the theoretical design of the sandwich longitudinal vibration piezoelectric transducer, this kind of three element radial vibration piezoelectric transducer is further improved, and a laminated three element radial composite piezoelectric transducer is proposed in this paper, which makes the complex assembly process simple and solved. In this paper, the internal metal prestressed tube is replaced by a cylindrical elastic expansion inner core, which does not need high precision hot working and can be dismantled at will. The radial vibration characteristics of the three element radial composite ultrasonic transducer are carried out by the theory, the finite element method and the experiment. The experimental results are basically consistent with the theoretical results.
1. the radial vibration characteristics of isotropic thin metal disk, thin circular ring and thin wall tube are briefly studied. The equivalent circuit and resonance frequency equation of each component are obtained by the principle of mechanical and electrical analogy.
2. the radial vibration characteristics of the single layer piezoelectric ceramic three element radial composite piezoelectric ultrasonic transducer are studied. The electromechanical equivalent circuit of the quasi thickness mode vibration of the piezoelectric ceramic tube is derived. The equivalent circuit and frequency equation of the radial vibration of the transducer are obtained through the continuous boundary conditions. The relationship between the number and the thickness of the tube wall and the position of the piezoelectric ceramic.
3. based on the design method of the sandwich longitudinal vibration piezoelectric transducer, a composite layer (usually even layer) sandwich radial vibration piezoelectric ultrasonic transducer is proposed on the basis of a single layer structure. The quasi thickness vibration electromechanical equivalent circuit model of the composite laminating piezoelectric Tao Cijing is obtained by the network cascade theory, and the radial vibration of the sandwich type is established. The electromechanical analog circuit of the piezoelectric transducer has obtained its resonance and the inverse resonance frequency equation. The dependence of the first, second order radial resonance frequency on the transducer, the effective electromechanical coupling coefficient and its geometric size is analyzed.
4. using the ANSYS finite element simulation software, the radial vibration of the sandwich radial composite piezoelectric transducer is analyzed. On the basis of the theory and the finite element analysis, several single layer and double-layer piezoelectric ceramic radial composite transducer with different thickness of the tube wall are fabricated, and the resonance frequency is tested. The results show that the theoretical calculation is basically consistent with the finite element simulation and experimental results.
【学位授予单位】：浙江师范大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB552

【参考文献】