Research On Radiated Sound Field Control Of Spherical Coronal Array Ultrasonic Transducer

With the development of ultrasonic technology in medical diagnosis and treatment,military marine,nondestructive testing,oil logging and other fields,the demand for precise control of sound field in various applications is also getting higher and higher.As the core device for realizing electro-acoustic energy conversion,the performance of the ultrasonic transducer is the key to determining the overall equipment level.Aiming to improve the performance of ultrasonic transducers,this paper discusses the influence of matching layer on the performance of focused ultrasonic transducers,designs the manufacturing method of the matching layer of spherical coronal focused transducers,and studies the effect of the backing layer material on the ultrasonic transducer,and proposed to use air as the backing material of the underwater acoustic transducer can improve the radiation efficiency of the transducer effectively.A spherical coronal array ultrasonic transducer composed of 128 array elements was designed and fabricated to obtain a high intensity focused sound field.Combined with the phased array technology,the focus position was controlled.The specific work is as follows:1.Study the influence of matching layer on the performance of focused ultrasonic transducer.(1)Based on the transmission and reflection theory of acoustic wave,the influence of matching layer on acoustic radiation propagation is analyzed.According to the characteristic impedance of the piezoelectric ceramic and the load,the optimal characteristic impedance of the matching layer is obtained.Based on the simulation,the influence of matching layer on the radiation performance of the focused transducer is analyzed.(2)Explore the proportion of materials used to produce impedance values for specific acoustic characteristics.The fabrication process of spherical coronal matching layer was designed for the focused ultrasonic transducer.The effect of the matching layer on the radiated sound field is verified by building a three-dimensional acoustic scanning system.The results show that the spherical coronal matching layer can make the sound wave emitted by the piezoelectric material propagate to the target load more effectively,reduce the reflection of the sound wave at the junction of the two kinds of media,effectively improve the acoustic radiation efficiency of the focused ultrasonic transducer,and protect the piezoelectric material from corrosion and damage by theexternal material.2.The influence of backing material on the performance of ultrasonic transducer is studied.(1)Based on the theoretical analysis of the influence of the backing material on the radiation efficiency of the transducer,it is found that the greater the acoustic impedance different between the backing layer and the piezoelectric element material,the higher the radiation efficiency of the forward load of the transducer.By using air as the backing material of the underwater acoustic transducer,the radiation of sound energy to the piezoelectric material can be reduced and the utilization rate of sound energy can be improved.(2)Based on simulation,the acoustic radiation of two kinds of transducer with different backing layer is simulated under the same voltage condition.It is found that the acoustic power and pressure obtained by the transducer with air backing layer are nearly twice that of the transducer with resin backing layer,and the acoustic radiation efficiency of the transducer is significantly improved.(3)Based on the sound field scanning system,the sound field distribution of the two kinds of transducers is mapped,and it is verified that the forward end radiation efficiency of the air backing layer transducer is higher.3.Designed and manufactured a spherical coronal array ultrasonic transducer composed of 128 array elements.According to the Huygens superposition principle,when 128 array elements are excited in the same phase by a phased array system,a spherical superimposed focus with a radius of about 3 cm is naturally generated at the center of the sphere due to the coherent superposition or cancellation of sound waves in each column in the space.The sound field inside is the strongest,and the sound field outside the ball decreases in turn.In addition,based on the time inversion method,the phase sequence of each array element is calculated according to the distance between each array element and the target point,and the phased array technology is used to set the phase or the corresponding delay signal of each array element,so the dynamic focusing of the array transducer can be realized at different positions within a certain space range.