The Study Of Pressure Resistance Ability For Class-? Flextensional Transducer

In order to obtain the further distance function,the modern underwater acoustic equipment presents an obvious trend towards Low-frequency development.Low-frequency sound waves were not easy to loss during propagation,and the key to get low frequency sound waves is to develop low-frequency emission transducers.The flextensional transducer is one of the main types of low-frequency emission transducers.It has the characteristics of small size,light weight and large power.However,due to the empty cavity inside the flextensional transducer,it is generally not suitable for deep water work.Therefore,it is an important issue to improve the pressure tolerance of the flextensional transducer.Based on the commonly used Class-? flextensional transducer as the research object,this paper has researched the structural features of air backing Class-? flextensional transducer,the pressure mechanism of pressure,the ways to improve the pressure capacity of transducer.Since the complex structure of Class-? flextensional transducer,the finite element method was used in this paper for simulation and analysis.This paper has derived the piezoelectric elastomer matrix forms of vibration equation and the finite element equations of the fluid and structure interaction problems,and probes into the ANSYS finite element software on the analysis of the application of transducer,ANSYS software is given when designing transducer specific steps.This paper has simulated calculated the air backing Class-? flextensional transducer,by using the finite element software ANSYS.The influence of structure size on resonant frequency and transmission voltage response of transducer is studied.The impedance characteristic curves in the air of the transducer,the impedance characteristic curves in the water and the transmission voltage response in the water are calculated.Finally,an optimized prototype of the transducer was obtained,with a resonant frequency of 1350 Hz and transmitting voltage response of 132.6dB.This paper makes an analysis of the key issues with Class-? flextensional transducer,such as the contradiction between low frequency high,broadband emission,pressure resistance ability.To improve the pressure resistance ability of Class-? flextensional transducer is the main research point in this paper.There are two solutions: one is to change the structure of transducer,enhance the structure strength,and improve the pressure resistance ability.Another way is to balance the internal and external pressure of the transducer to improve the working depth,by using pressure compensation.To solve the pressure problem of transducer,three solutions are proposed,and the simulation calculations are carried out respectively.The first is structure self-supporting.It calculated that the transducer end cover and concave shell parts are the stress concentration,through the stress analysis of transducer under the action of static pressure.By the way of increasing circular bead in the joint parts of end cover and shell,it makes the maximum stress decreased by 48%.So that the maximum working depth of structure self-supporting Class-? flextensional transducer increased from 50 m to 95 m,but basic performance remains the same.The second way is to the overflow Class-? flextensional transducer acoustic performance of the transducer has carried on the simulation,and compared with the situation of air when backing,not feasible to direct relief plan are summarized.Successively to the pore diameter of 1 mm respectively,2 mm,3 mm,6 mm hole overflow Class-? flextensional transducer are simulated.The hole diameter of 2 mm is the optimal effect.At that time,transducer resonance frequency is 2469 Hz,transmitting voltage response of 120 dB.With compared to the air backing Class-? flextensional transducer,r resonant frequency increased 1181 Hz,transmitting voltage response decreased 12.7 dB.The fourth way is the overflow filling of the acoustic compliance tube,which can improve the response of the transducer and eliminate the "sound short circuit" by filling the fluid cavity in the transducer with a certain compression coefficient.Through analyzing the structure and working principle of the acoustic compliance tube,a good pressure tolerance of more than 3MPa was designed,which the compressibility factor was 20 times of the water.When fill the fluid cavity of Class-? flextensional transducer with six roots acoustic compliance tube,the resonance frequency of the fluid cavity modal is 650 Hz,transmitting voltage response is 120.8dB;the resonance frequency of the bending vibration modal is 1950 Hz,transmitting voltage response is 126 dB.According to the simulation results,the acoustic compliance tube and Class-? flextensional transducer under different working conditions are processed and measured.As the result of test,the resonance frequency of air backing Class-? flextensional transducer is 1450 Hz,the transmitting voltage response is 132 dB,pressure resistance ability less than 0.7MPa.The overflow Class-? flextensional transducer appeared serious "short circuit" phenomenon,bending vibration modal of the resonance peak disappear,but the liquid cavity resonance peak appeared in the low frequency band.When fill the fluid cavity of Class-? flextensional transducer with six roots acoustic compliance tube,the resonance frequency of the fluid cavity modal is 780 Hz,transmitting voltage response is 115dB;the resonance frequency of the bending vibration modal is 2000 Hz,transmitting voltage response is 125.1dB,in the working frequency from 680 Hz to 3000 Hz,the source level greater than 175 dB.Under the hydrostatic pressure of 3MPa,the transducer keeps the performance,and test results is the same with simulation results.The above results show that the overflow filling of the acoustic compliance tube has affectively increased the compression capacity of Class-? flextensional transducer.