带有复合结构的多层隔振系统振动传递及声辐射研究

本文将船体结构与安装在其上的设备和周围水介质合在一起建立了一个数学物理模型，即研究具有机器──上层隔振器──带有粘弹性材料（阻尼处理）的筏架结构──下层隔振器──基座艇体──外流场的艇体振动及声辐射。首先，从复合结构与流体相互作用问题的有关混合边值问题出发，针对声波辐射特点，推导了一种广义形式的Hamilton原理及有限元形式的运动方程。在此基础上，分别推导了带有粘弹性材料的筏架结构和艇体与声学介质耦合的动力学运动方程式。进一步在阻尼处理面积及位置、上下层隔振器刚体变化、基座面板厚度变化等四个方面对浮筏隔振系统声场特性的影响作了详细计算及分析研究，得到了一系列具有工程应用价值的结论。

RESEARCH ON VIBRATION AND SOUND RADIATION OF MULTILAYER ISOLATION SYSTEM WITH COMPOSITE STRUCTURE

In this paper, a mathematical and physical model is established to simulate the system, a rigid body supported on a flexible raft, which in turn is supported on a flexible cylinder. The raft contains the elastic and visoelastic materials. Flexible passive isolators are located between the rigid body and the raft, and between the raft and the flexible base.The reinforced cylinder is freely submerged in an infinite fluid. An analytical theory and a series of numerical methods for the vibration behaviour and sound radiaton of the system have been studied. At first, based on the boundary value problem concerned with fluid composite structure interaction and characteristic of acoustic wave radiation, a generalized Hamilton variational principle is derived, and the equations of motion based on the finite element method are also derived. From this, the motion equations of the raft with viscoelastic materials and the motion equations of the cylinder submerged in an infinite fluid are obtained respectively. The effect of the area and location of damping treatment in the raft, the stiffness of the flexible isolators, as well as the thickness of the surface plate of the base on the behaviour of the acoustic field and vibration of the system are studied and calculated in detail. Valuable results for engineering application are obtained.