Fatigue Strength Analysis And Assessment Method Study Of Membrane Tank LNG Vessel

LNG is shortened form of Liquefied Natural Gas. LNG vessel is an important tool for international LNG transportation. All the technology problems and special technics are integrated into LNG vessels, which make LNG vessel acknowledge as a famous kind of ship with high technology and additional value. Although the first LNG vessel is constructed in china, many critical technology problems are still needed to be solved because all the critical technology is monopolized by Europe and almost all the structural analysis of LNG vessel is based on oil tanker rules for lacking of research about it and critical patent imported abroad. It has practical sense of doing research in this field. Different rules are used to calculate the fatigue capability of a LNG vessel in the research.The influence of LNG vessel's low temperature to fatigue capability is considered,and the influence of temperature alternation stress is first put forward,which can be referenced by other LNG researches in our country.The main work of this research is listed as follows:1) The development of fatigue research and structure characteristics is briefly introduced and the research value of LNG vessel is analyzed. Also, the fatigue analysis method is expounded.2) A deep study of ABS rules about membrane tank LNG was carried out, the finite element model has been built, and fatigue life of typical joints based on the requirements of ABS rules about LNG were evaluated. Besides, because of similar structrual design and similar fatigue damage region between LNG and oil tank, fatigue evaluation of the same LNG was also carried out according to CSR for oil tanker in order to make a comparison between these two rules.3) Based on characteristics of low temperature environment, the influence of the material change to fatigue capability is discussed.4) Considering the temperature alternation stress induced by temperature difference of day and night, the loading and unloading of LNG on board, the research of fatigue damage is done to obtain an useful result.