Study On High Directivity And Modal Radiation Efficiency Of Curved Vibration Disc

The application of the flexural vibration radiator in the ultrasonic field is more and more widely since it was proposed in the last century. The flexural vibration radiator has large radiation area, and its radiation impedance can better match with the air medium.If the efficient power sandwich transducer is applied in the center of it as a driver, that it can radiate intense ultrasound into the air more easily.Directivity pattern is a very important parameter to describe the radiator performance, it shows that whether the energy of acoustic field is concentrated.And because the sides phase disk vibration section line of the flexural vibration flat disk is opposite, that causes sound field vibration interference cancellation and the acoustic field directivity not sharp, in this case the flexural vibration stepped circular plate is put forward. The modal radiation efficiency of the vibrating objects is the ability to radiates energy of different modals. Along with the change of the flexural vibration radiator size and the vibrating frequency, the directivity and the modal radiation efficiency will change, the working frequency, the plate radius and thickness of the plate be known in advance makes the directivity and the radiation efficiency of the plate is easier to reach the maximum. In this paper, the influence of the radiation efficiency and the directivity caused by the change of the size and the flexural vibration frequencies of the flexural vibration plate and the plate ladder is calculated and analyzed. The main work and research results are as follows:1The flexural vibration frequency, the displacement distribution and the radius of nodal circle radius of the plates with the same radius and different thickness are calculated by using the Kirchhoff classical thin plate theory and Mindlin plate theory. These results compared with the finite element results. The above results intuitively show the differences between the two kinds of theory in the treatment of different thickness flexural vibration plate.2The flexural vibration stepped plate is divided into two parts, a part is a ring disk outside of the pitch line, the other part is circular plate inside of the pitch line. The directivity of the free boundary stepped plate with a step is calculated on the flexural vibration frequency of the stepped circular plate based on the actual model. The relationship between the directivity and the material composition, the substrate thickness and the resonance frequency is also calculated by using directional analytic expression.With the increase of the vibration frequency, the radius of the stepped circular plate and the radius of its pitch line will decrease, the directivity pattern of the main lobe is becoming more and more sharp, but the side lobe will increase. The changes of the direction is not obvious of ladder disc with a resonant frequency and different materials, which indicates that directivity seems doesn’t matter with the material of the stepped plate. The main lobe direction will be more sharp as the increase of the substrate thickness of the stepped plate with a resonant frequency and the same material.3The relationship between the modal sound radiation efficiency of the flexural vibration thin plate and the disk geometries, the frequency factors is derived. Which can determine the optimal geometric dimensions of the thin plate when the modal radiation efficiency is the highest.The radiation efficiency increases with the increase of the frequency when the disk drive frequency is low; when the frequency increases to a certain value, the radiation efficiency began to change with the frequency. The geometry of disk to the maximum radiation efficiency is calculated when the frequency and the nodal lines are specified.This study provides a theoretical reference for the design of practical science of the stepped circular plate.