| The vibration characteristic analysis of ship structure is a very important part of the research of ship structure vibration. Excessive vibration response levels will affect the normal work and life of crew and passengers, and will also cause acoustic fatigue damage to some part of ship structure. Furthermore, the vibration of structure will affect the normal function of electronic instruments and reduce the lifetime. With the development of high speed ships and large-scale power plant, this problem is becoming more and more important.Plate structure is the most basic and most important component of ship structure. In engineering applications, plates are generally joined together along their junctions with specific angles, within which the longitudinal, shear and bending waves are transmitted. Of these three waves, bending is referred to as the out-of-plane mode, longitudinal and shear together as in-plane modes. Particularly, these three waves can be converted into each other due to wave reflection and refraction at plate junctions, which makes dynamic characteristics very complicated, and greatly challenges the design capability of mechanical engineers.Our present work covers the several following parts: Firstly, projection method is utilized to derive the generalized displacements and forces so as to obtain the dynamic stiffness matrix accounting for both in-plane and bending vibrations of a rectangular plate in an explicit form, which is validated by the experiment results. Secondly, through coordinate transform of local coordinate system into the global coordinate system and classic finite element assembly theory, the overall dynamic stiffness matrix of built-up structures is deduced. Then the vibration responses are obtained, and are verified by analyzing the free and forced vibrations of an L-shaped plate. Thirdly, power flow characteristics of the L-shaped plate are investigated. Finally, the prediction for the vibration of a double bottom ship section structure is carried out by using the dynamic stiffness matrix, and the influences of some of the structure parameters are investigated, which provides theoretical guidance for engineering application. |
