Rectangular Plate Vibration Mode Point Streak Research

The bending vibration of the radiation plate has been widely used in air application because of characteristics of a large area. Such as ultrasonic drying, condensation, dust and measured by ultrasound and other fields. Vibration displacement and vibration mode is the key point on the study of bending vibration radiator sound field. Bending vibration of thin circular plate has reached a more in-depth level, and even stepped disc design has also been some progress. Relatively speaking, have little in-depth study of the bending vibration of thin rectangular plate of the sound field, especially in relation to the free boundary rectangular plate radiated sound field. The acoustic of flexural vibration radiators under free boundary conditions, vibration equations have no analytical solution, radiated acoustic field cannot be calculate using the analytic method.In this paper, we start from the stripe vibration modal, special model of bending vibrational rectangular plates when the pitch line close to a straight line, and calculate the acoustic radiation directivity of the plates by using a numerical method. In order to obtain the sharp point of the acoustic radiation directivity, we propose two schemes for the improvement of the structure of the plates.This paper carries out the following works:Modal analysis is carried out by finite element software, the vibrational surface is discretized and the displacement and coordinates of each vibration unit are obtained. We calculate the acoustic radiation directivity of the three kind of rectangular plates, including the original one and the two improved plates, then get the two-dimensional and three-dimensional figures of the acoustic radiation directivity of the three kinds of plates. The conclusions are as follows:(1) Before the improvement, the acoustic radiation directivity is not good in the axial direction of the rectangular plates, and the sound energy is mainly distributed in the non-axial direction. This shows that the acoustic radiation directivity of the rectangular plates is very poor, dispersion of the sound energy is relatively serious, and it cannot be used in the fields which have high demand to the acoustic radiation directivity. So, we must improve the structure of the plates to get good acoustic radiation directivity.(2) The first improved rectangular plates have obvious sharp acoustic radiation directivity in its axial direction. With the gradual reduction of the vibration order, the main-lobe is larger than the side-lobe in the axial direction. This shows that the sound energy has a certain degree of concentration in the axial direction.(3) The second improved rectangular plates also have sharp acoustic radiation directivity in its axial direction and small side-lobe.In contrast, the directivity of the second improved plates is sharper than the directivity of the first improved plates, and the side-lobe of the second improved plates is smaller than the side-lobe of the original one and the first improved plates. This shows that the second improved plates are the best.The practical significance of this paper is that the structure of the free boundary bending vibrational rectangular plates is improved theoretically, it provide a certain reference for the design of the ladder plates.