Multi-physical Field Modeling And Equipment Development Of Low-frequency And High-power Giant Magnetostrictive Tansducer

Ocean contains rich biological and mineral resources,which is an important guarantee for the sustainable development of humanity.Meanwhile,with the increasingly fierce international battle for maritime rights and interests,underwater combat equipment such as low-noise and quiet submarines have developed rapidly.It seriously threatens the Marine national defense security of our country.Therefore,the development of underwater remote target detection system is of great significance for realizing the sustainable development of national energy and maintaining Marine national defense security.The low-frequency underwater active detection method has significant advantages in detection distance,environmental adaptability,and anti-noise processing.It has become an important means for countries to explore ocean resources and warn underwater military threat targets.Lowfrequency and high-power electroacoustic transducers and arrays are the key equipment to transmit low-frequency sound in the underwater remote target active detection system.They also are the key to seize the "Marine strategic commanding heights" in the world at present.This paper focuses on the important needs of Marine resources exploration and national Marine security defense.It is supported by the National Major Research Instrument Development Project "Multi-frequency and Multi-azimuth Cooperative Acoustic Radar System Oriented to Marine Underwater Moving Target Measurement"(52127901)and the National Natural Science Foundation key Project "Research on High-power and High-efficiency Electro-acoustic Transduction Mechanism and Control Method"(51837005),etc.Researches on multi-field coupling modeling,optimization method under multi-parameter and multi-boundary conditions,efficient and high reliable development method of low-frequency and high-power giant magnetostrictive electroacoustic transducer(GMEAT)are carried out.The efficient and reliable low-frequency and high-power electroacoustic transducer and its array have been developed.The acoustic source level(SL)of more than 220dB and the remote target detection of 50km have been realized.This research provides the theoretical basis and practical guidance for the realization of low-frequency and high-power acoustic source,and provides equipment and technical support for the underwater remote active detection system.The main technological innovations are as follows:1.The magnetic structure and its modeling method are studied.The differences in magnetic field strength and copper loss between the two magnetic structures with bias field provided by DC and bias field provided by permanent magnet are explored.It provides the basis for the subsequent selection of magnetic structure of low-frequency and high-power GMEAT.The equivalent "magnetic circuit" model of the multi-vibrator magnetic circuit considering permanent magnet and air-gap leakage is proposed.It can quickly calculate the magnetic field strength of the rod.A test platform for the characteristics of giant magnetostrictive materials(GMM)is built to verify the effectiveness of the proposed equivalent "magnetic circuit" model.The platform can also determine the bias condition of GMM,which provides the basis for the design of low-frequency and high-power GMEATs.2.A low-frequency and high-power GMEAT field-circuit multi-field coupling model is constructed considering the influence of eddy current and magnetic leakage.Based on the idea of piezoelectric and piezomagnetic analogy and the idea of field-circuit coupling,the magnetic circuit model considering magnetic leakage is combined with the electro-mechanicalacoustic coupling finite element model(FEM).The complex permeability is introduced to consider the influence of eddy current,which can predict the impedance and acoustic characteristics of GMEATs effectively.In addition,a mechanical-acoustic coupling model of the electroacoustic transducer based on lumped parameter method is proposed.The output force of the GMM rod is equivalent to the sum of lumped parameter elastic force and magnetostrictive driving force.The SL of the transducer can be predicted effectively only by the mechanical-acoustic coupling calculation,which greatly improves the analysis and calculation efficiency.The experimental results verify the validity of the proposed multi-field coupling models.This method provides support for the optimization of low-frequency and high-power GMEATs.3.The optimization method of low-frequency and high-power GMEAT is studied.Aiming at the problem that it is difficult to quickly obtain a transducer design scheme that can meet the requirements of frequency,SL and working water depth,a response surface optimization method of lowfrequency and high-power GMEAT is proposed.According to the electromagnetic parameter limit of GMM,the number of vibrator rods,the magnetic loop structure and the coil parameters are determined.Combined with the cavitating boundary,the optimization range of mechanical shell structural parameters is determined.The main optimization variables are determined by sensitivity analysis.Based on Box-Behnken method,the"multivariable-output" response surface model of GMEAT is established,and the optimal structural parameters of the shell are obtained.Finally,a GMEAT prototype is developed.Experimental results verify the effectiveness of the design method.4.The development method of low-frequency and high-power GMEAT is studied.In order to solve the problem that it is difficult to predict and control the prestress of the GMM rods under the target water depth,a physical analytical model of the assembly process of GMEAT is established.The influence of water depth on the deformation of the transducer shell is analyzed,and a method to ensure the desired prestress of the GMM rods under the target water depth is proposed.The sealing method of transducer,considering the effect of hydrostatic pressure,is studied to meet the requirements of long-term reliable underwater operation.The experimental results show that when the transducer works in the water depth of 40m,the SL is greater than 210dB in the frequency range of 300～350Hz.The prototype transducer can realize high efficiency and reliable operation,and verifies the validity of the design and development process.5.The low-frequency and high-power GMEAT array technology is studied.The effects of array spacing,array amplitude and initial phase difference on directivity,array gain and interaction between array elements are investigated.A high-gain array arrangement is determined.Aiming at the demand of sound source for 50km underwater target detection,the realization schemes of single transducer and array sound source are compared and analyzed from the aspects of rod number,power supply demand and shell radiation area.Line array of different elements is developed,and lake test is carried out.The experimental results verify the feasibility of the proposed array scheme.On this basis,a 3element line array with a center frequency of 320Hz is adopted to realize 50km underwater target detection.The test provides reliable support for further improving the underwater target detection distance.