Coupling-vibration Analysis Of The Ship Main Engine And The Double Bottom

Shipping is the carrier of marine military affairs, transportation and entertainment, which plays an important role in the industry epoch as well as the high-speed development of the logistics industry in the 21st century. One of the important factors that affect the security of the shipping is the vibration of the ship structure and equipment, and with the development of science and technology, this subject is scheduled gradually, and becomes the advanced researching subject in modern times. Currently, the modal analysis of the hull ship structure and the influence analysis of the different shell thickness have already developed step by step, and some effective tackling methods have been put forward, while the analysis of the coupling vibration between double bottom structure and the facilities of the ship still has plenty of blank space. Merely analyzing the double bottom structure or the facilities cannot reflect the vibration situation of the real structure. Many factors can cause the structural response, such as the way of connection, arrangement of the top bracing, the stiffness of the structure, condition of operation and etc.According to the present study, the paper summaries the vibration study of ship structure, the vibration analysis of diesel engine, the methods of handling connection, the influence of structure stiffness, which elicits the frontier subject about coupling vibration of the main engine and the double bottom. On the basis of the requirement of improving calculation accuracy and lowing computational scale as well as the influence of different connection, develops the coupling structure of the main engine and the double bottom through ANSYS software, which provides the foundation for characteristic analysis and structural optimization of vibration.Firstly, doing the free modal analysis and constraint modal analysis of the finite element model have reached the variation rule that the natural frequency increases with the different joint stiffness, and stress that it can not change the bolt preload and connection joint surface randomly. Secondly, through load calculation, simplification and loading of the main engine, the author has made several transient dynamic analysis on the coupling structure of the main engine and the double bottom, and the result has demonstrate that the treatment of three dimensional spring and the method of coupling all degrees of freedom are almost the same in the analysis of coupled vibration. Thirdly, analyze the main engine's top bracing arrangement, and then make response structural vibration analysis on the two different top bracings, and it concludes that the vibration response is less when the bilateral top bracing is supplied. Finally, use the statics to analyze and compute the four kinds of structural stiffness of double bottom, and then do the transient analysis. The results indicate that the stronger the structural stiffness is, the weaker the response of vibration is. In other words, it delivers less energy in the vibration. By further use processor to analyze and compute the size and distribution of longitudinal rib's stress, the author finds that both top bracing arrangement and structural stiffness have certain effects on the vibration. Therefore, it is important to design the hull ship structure selectively and specially, according to the requirement of different ships'quality, speed and vibration.