Views: 4 Author: Site Editor Publish Time: 2020-03-12 Origin: Site
The transducer array are the key components in the sonar system. It is a device that realizes the mutual conversion of electro-acoustic energy. The performance of the transducer and the transducer array mainly depends on the performance, structure and manufacturing process of the transducing material. At present, most of the underwater acoustic transducers which use lead zirconate titanate piezoelectric ceramics (PZT) as the energy conversion material, which has the advantages of high electromechanical coupling coefficient, low loss, convenient manufacture, and low price. However, due to the high characteristic impedance of piezoelectric ceramics, when the load is water or biological tissue, it is not easy to match the load, the reflection loss of piezo ceramic ring at the interface is large, and its lateral coupling is strong. Therefore, the thickness vibration transducer is prepared with it narrow frequency band, high Q value, low sensitivity and other shortcomings. 1-3 type piezoelectric composite materials have low characteristic impedance, Q value, dielectric constant, lateral electromechanical coupling coefficient and high thickness electromechanical coupling coefficient due to the polymer phase. Ideal material for the energy saving device. The performances of piston transducers made of the same size 1-3 piezoelectric composite materials and ordinary PZT discs were measured, and the admittance curves and transmission of the two transducers in the air and water were obtained. It is voltage response, receive sensitivity, and directivity plots. And through comparative analysis, it is concluded that the 1-3 type piezoelectric composite material transducer has a significantly improved transmission and reception performance compared with ordinary PZT piezoelectric transducers. The improved 1-3 (1-3-2) piezoelectric composite retains the excellent electro-acoustic characteristics of the 1-3 PZT5 piezo ceramic composite, and has good temperature and pressure stability, which is very suitable for preparing underwater acoustics transducer. This paper uses a 1-2-3 piezoelectric composite material to design and manufacture a cylindrical underwater acoustic transducer, and measures its admittance, transmit voltage response, receiving sensitivity, and directivity.
Piezoelectric composite materials are made of 1-3 piezoelectric composite materials and piezo ceramic substrates connected in series along the ceramic polarization direction. This structure has rigid piezoelectric ceramic support in parallel and perpendicular to the polarization direction, which is more stable than 1-3 type composite materials. It not only retains all the advantages of 1-3 piezoelectric composite materials, but also is not easy to deform at higher temperatures, and has better heat resistance and resistance to external impact. The piezoelectric composite material is prepared by a cutting-filling process. The piezoelectric ceramic uses PZT-5A produced by the Institute of Acoustics of the Chinese Academy of Sciences. It has been polarized when it leaves the factory. An automatic cutting machine is used to cut the surface perpendicular to the polarization axis of the piezo ceramic in two directions that are perpendicular to each other, retaining a certain thickness of the substrate to form a ceramic skeleton. A polymer with an appropriate amount of curing agent is poured into the ceramic framework (that is, the epoxy resin WRS618 produced by Wuxi Resin Factory), and then the vacuum ejector bubble is evacuated and cured at room temperature to make a composite material, which is ground or cut to shape the blank. A composite material sample was formed, and finally, the surface of the sample was covered with an electrode by using a high vacuum magnetron sputtering apparatus. Using the above process, two pieces of 1-3-2 piezoelectric ceramic / polymer composite sheet of 40mm * 40mm * 10mm were prepared. The width of the ceramic pillars and the width of the epoxy resin between the pillars are 0.9 and 0.45 mm, respectively, and the thickness of the piezoelectric cylinder transducer
is 1 mm. Along the thickness direction of the composite material, two pieces of composite material were cut into 24 composite material wafers with a length of 10 mm, a width of 6.5, and a thickness of 10 mm. The resonance performance of each piezoelectric wafer was measured, and 18 of them were selected for making two replacement wafers. The performance measurement results of each element of the transducers, the performance consistency of each piezo element is good, and its resonance frequency is almost the same. The figure shows the admittance measurement curve of one of the array elements, where the array elements are all similar to it.
Structure and manufacturing process of piezoelctric cylindrical transducer
A plurality of 1-3-2 piezoelectric composite materials are uniformly arranged along the circumference to form a circular array to produce a cylindrical transducer. The structure of the transducer is shown in the image. At present, no transducer of this structure is found .There are related research reports.
The composite cylindrical piezoelectric transducer is composed of a composite element, a copper backing, a bracket and a cover plate. Eighteen composite PZT material elements are evenly arranged in the grooves of the ring-shaped copper backing along the circumference, and the bottom surface of the composite material elements is adhered to the copper backing with a conductive adhesive. In this way, the copper backing can not only locate the array elements, but also enhance the vibration displacement. Due to the use of conductive adhesive bonding, the lower electrode of the composite element is connected to the backing, which simplifies the electrode lead process. In this way, the lower electrode lead (signal line) can be led out from the inner side wall of the copper tube backing and connected to the same signal cable of the shaft cable. Then, the bracket and the end cover respectively clamp and fix the copper backing from two directions. The backing, the bracket and the end cover are insulated with a rigid foam washer, and then the external electrodes of the composite material piezo elements are connected to the shielded wire of the coaxial cable, and sealed with a watertight joint or waterproof glue. Finally, the assembly is placed in a mold, and a polyurethane with a thickness of about 2 mm is poured to form a waterproof, sound-permeable, and sealing layer. By using the above process, two identical cylindrical transducers were experimentally manufactured, and the overall dimensions of the cylindrical transducers after assembly were 70 mm × 15 mm.
