Research On Fatigue Assessment Method Of Ship Structures

In recent years, along with the highly developed economy of our country, the international trade and transportation of cargo increase greatly. Ship as the main means of transport have become increasingly onerous in its work At the same time, there appear all kinds of metal problem which can result in vast personnel and economic loss.Among these problem the most common and also the most serious is the trouble in ship structures which mostly are troubles of fatigue crack. Fatigue is one of the main causes of ship structure failure, which has extensively caught the attention of the people and become a hot investigation point.This thesis takes one 19350 tons bulk carrier as the research object. The fatigue strength of ship body central cabin segment has been checked by the CCS《the ship body structure fatigue strength guide》and fatigue software respectively. Try to provide an usage reference for using fatigue software to check ship structure fatigue strength。First, this thesis discussed the importance of preceding the research on the ship structures and especially the research on the fatigue longevity. It also puts the main content of the problem and elaborates its significance in theory and practice. Then this thesis inquire the basic theory of fatigue strength and introduce the process of《the ship body structure fatigue strength guide》and the fatigue finite element software MSC.Fatigue.Secondly, at the foundation of the knowledge of MSC series software,this thesis gives the finite element modeling and calculation to the ship structure by MSC.Patran and MSC.Nastran. In the processes of making modeling, we take more attention to the multi-point constrain.On the bases of introducing the technology on fatigue Finite Element Analysis, this thesis makes use of the software MSC.Fatigue to proceed the fatigue analysis on the ship body central cabin segment structure under certain load in view of the present practical conditions of the ship structure's fatigue research,by the analysis, we can get the cloudy pictures of the fatigue distribution,and can clearly see every parts fatigue life. The calculation result is basically consistent with CCS fatigue assessment methods situation. Therefore this analysis can supply theory basis for the improvement of ship structure design and fatigue research. The thesis has important engineering practical value.At the end of this thesis, some conclusions on this subject's practical and academic significance are presented, the thesis also submits the research direction in the future.