Types and designs of underwater acoustic transducers(2)
Publish Time: 2019-03-13 Origin: Site
A flexural transducer is a type of transducer that utilizes the longitudinal vibration of a piezoelectric ceramic or a magnetostrictive rod to excite a radiating surface of an outer casing (or barrel beam) having an amplitude amplification effect for bending vibration. Types of flexural transducers, in which have the common feature, the longitudinal vibration rods excite a rotationally symmetric curved shell, and the shell may be a continuous structure or a structure in which a slit is machined into a set of beams. which developed a concave barrel beam bending transducer with Terfenol-D material, the resonance frequency is 1300Hz, the sound source level is 188.7dB, and the bandwidth is 600Hz. Due to the single rod open magnetic circuit, At the resonant frequency, the AC acoustic efficiency is only 7% at maximum, and the weight of transducer is 2.7kg. Type IV, VII, and fish lip-bend transducers have the common feature. The transducer is excited by a longitudinal vibrating rod to excite the bending vibration of a convex or concave elliptical shell to achieve high-power radiation. The amplitude amplification effect and area effect are adopted to improve the sound radiation power. The new low-frequency, high-power hydroacoustic underwater ultrasonic transducer is reported, including transducers with resonant frequencies of 210 Hz, 450 Hz, 800 Hz, and 1200 Hz. The new transducers are currently used in low-frequency active sonar arrays. It is acoustic sound source, noise simulator and other acoustic systems.
ferroelectric material underwater acoustic transducer:
Relaxation ferroelectric materials are a kind of functional materials with potential, which can be divided into electrostrictive ceramic and relaxed ferroelectric single crystal types. Ferroelectric single crystals are much more complicated than electrostrictive ceramic materials. Researchers have used this type of material to make a variety of types of piezoceramic cylinder ceramic transducer, such as flexural transducers, longitudinal transducers, etc. The manufacturing technology of transducer material is more complicated, and it needs to add DC electric field, applying prestress, control process temperature and so on. The flexural transducer was developed by using PMN-PT-BT (lead magnesium niobate-lead titanate-barium titanate) electrostrictive ceramics. The research results develop transducer has not been maximized. this work in the future is still one of the hot issues that need to be explored in the field of underwater acoustic transducers.Ferroelectric single crystal materials studied 3.5 MHz ultrasonic probes for medical B-mode and Doppler ultrasound imaging equipment, suggesting the application prospect of relaxation ferroelectric single crystal materials in the high frequency image sonar.
Piezoelectric polymer film underwater acoustic transducer
transducer is made, it can be designed into any shape, and the acoustic impedance of the material is low, and it is easy to achieve impedance matching with fluid medium and biological tissue such as water, and is commonly used to make high-frequency standard water, high frequency transducers, medical ultrasound transducers, conformal arrays and diversified composite transducer arrays.The common piezoelectric polymer is used to make transducers mainly polyvinylidene fluoride ( PVDF ). The more compelling piezoelectric polymer material film (abbreviation of electro-mechanical film) is a polypropylene foam flexible film with a piezoelectric constant of about 10 times that of PVDF, which can be used to make high sensitivity transducers. A structural EMFi film transducer was developed with a receiving surface diameter of 35 mm and a transducer receiving sensitivity is greater than one 190 dB. This transducer can also be used in the air to receive or emit sound waves.