The Research On The Vibration And Sound Radiation From A Finite Elastic Structure Excited By Random Force

This dissertation is based on FEM and BEM methods. The FEM software ANSYS and the BEM software SYSNOISE are used to resolve the problem of the structure excited by random force. By analyzing the structure vibration and sound radiation properties of finite length elastic cylindrical shell excited by random force, it gives numerical calculation methods for the sound field response of the structure from random excitation in different sound field conditions. The main contents and methods are as follows:1. The power spectrum density of the structure response is calculated by using ANSYS. A numerical calculation model is founded by using the software ANSYS, the random vibration response of the structure excited by the random force has been analyzed by using the dynamic analysis function of the software.2. The coupling vibration of fluid and structure from random excitation in infinite field can be solved by using SYSNOISE. Firstly the modes of an underwater elastic structure are analyzed, then the structure's normal displacement response has been calculated, and the sound field properties can be obtained by analyzing the sound pressure distribution of the sound radiation field.3. Based on structure-sound system function, the sound response of the structure excited by random forces is analyzed. The system function of the structure-sound response from random excitation is built up. According to the theory of random vibration response, the structure-sound radiation from random force excitation is simulated by using the transfer function between the random input forces and sound field output.The problem of random force input in different sound field has been studied. It makes the simulation much closer to the practical engineering, and may be valuable to the random noise prediction of the underwater elastic structures.