Research On The Reaction Of Ship Equipment To The Shock Environment Of Installation Foundation

The anti-shock ability of shipboard equipment has always been an important research content of the ship's vitality at home and abroad.In order to accurately study the anti-shock ability of ships,anti-shock design and protection,we must first determine the shock environment that ship equipment received,which is usually expressed by shock spectrum.In the previous analysis,the base and the hull structure were regarded as infinitely rigid foundation,on which the shock environment of the equipment was analyzed.However,the shock environment of equipment is the result of interaction between ship equipment and hull structure.When the modal characteristics of the foundation where the ship equipment installated are the similar to the modal characteristics of the equipment,due to the dynamic reaction of the ship equipment to the foundation,there will be obvious decline of the shock spectrum at the fundamental frequency of the equipment.This phenomenon is called "spectral dip".This paper uses the concept of four-terminal parameters and impedance in mechanical vibration,simplifies hull-base-equipment system to three-degree-of-freedom system based on simplified method in structural dynamics,analyses the the dynamic characteristics of the bare foundation and structure after the installation of equipment,explore the transfer function of the structure after installing the equipment.Combined with Fourier transform,inverse Fourier transform and Duhamel integral,the shock environment calculation method based on impedance concept is proposed to provide input load for the anti-shock design of the equipment.This paper analyses the reaction of the ship equipment on the installation foundation in principle.Due to the use of impedance method,this paper can consider the equipment installation location,equipment size,base form and other factors effect on the shock environment well.In this paper,it is found that equipment impedance,fundamental impedance,equipment frequency and fundamental frequency have effect on the shock environment.This paper studied the influence of impedance ratio and frequency ratio on the "spectral dip" effect and get the empirical formula of spectral dip.Carrying out the shock test of structure after the installation of equipment and impedance test of equipment part and foundation part,so as to test and verify the applicability and reliability of shock environment calculation method and empirical formula of spectral dip.