Research On The Sound Radiation Characteristics And Active Control Of Rib-stiffened Plates

The rib-stiffened shells or plates are commonly used in the modern equipment. The sound radiation of such structures can have direct effects on the performance of the equipment, therefore it is of great importance to investigate the sound radiation characteristics of rib-stiffened structures. This dissertation applies a method using Finite Element Method(FEM) in conjunction with Boundary Element Method(BEM) based on First-Order Shear Deformation Plate Theory(FSDT) to investigate the sound radiation of rib-stiffened plates. The influence of the hosting homogeneous isotropic plate, boundary conditions, stiffeners and viscoelastic damping materials on the sound radiation characteristics of rib-stiffened plate are studied and then validated by experiments. In addition, the application of active control in vibration and sound radiation at low-frequencies is also studied preliminarily. The main work and conclusions are as follows:1. The method to sound radiation calculation of rib-stiffened plate considering moving fluid loading is developed using FEM coupled with BEM based on FSDT. In comparison with the result calculated using COMSOL, this method is verified.2. The theoretical analysis of sound radiation of the rib-stiffened plate is carried out. Considering the effects of factors such as hosting plate, boundary conditions, stiffeners, viscoelastic damping materials, the effective density and effective stiffness have significant influences on the sound radiation of rib-stiffened plate. The experimental results also agree well with the theoretical analysis.3. Due to the poor results passive control for sound radiation of the rib-stiffened plates at low-frequencies, the active control methods based on velocity and displacement negative feedback control are used on the plate to see further decrease in the level of vibration and sound radiation. These active control methods are applied to a rib-stiffened plate submerged in both air and water as a comparison. The analysis results show that using active control to reduce the vibration and sound radiation of the rib-stiffened plate is effective. Moreover, it is more effective to use the active-passive control, a method combining active control and passive damping control, than to only use active control to achieve better results at low-frequencies.In summary, the influences of various factors on the vibration and sound radiation characteristics of rib-stiffened plates are investigated systemically in this dissertation and the effects of active control and active-passive control at low-frequency range are studied. This work provides certain theoretical and technical guidelines to effectively reduce the sound radiation of rib-stiffened plates.