The Fatigue Analysis On Connector Of Semi-submersible Very Large Floating Structures

With the reduction of land resources in China,the development of marine is imminent,in recent years China's dispute with neighboring countries on the sovereignty of the islands intensified,It is important to have large floating platforms for berth and land.Beacuse the VLFS has a huge size,it is unwise to use long continuous structure,the multi-module mode is a wiser choice.The modules are connected by connectors to ensure the continuity of the structure,and to reduce the bending stress caused by the wave.The fatigue life of the connector to the VLFS has a vital influence on normal operations,its service life directly affects the VLFS whole life,it is important to study the fatigue life of connector.First of all,this paper expounds the material fatigue life of the related theory,according to the material properties of very large floating body connector,selects the s-n curve method for fatigue life theory basis.According to the influence of average stress on fatigue strength,the GOODMAN method was chosen to revise.Secondly,according to the theory of hydrodynamics,the hydrodynamic analysis software AQWA,Using time domain analysis method to simulate the response of VLFS in mooring motion is calculated based on connectors static load amplitude and load time history spectrum.Concluded that under the load Angle of 45° environment connector c6 stress is the largest,and the load has little effect on the y direction of connector.Then,Based on the previous research,this paper selects three kinds of connector design scheme,a rigid hinge scheme and two kinds of flexible hinge schemes.Three kinds of flexible cushioning materials with different elastic moduli are selected.Through the combination of different buffer materials and flexible connection schemes,seven kinds of connectors are obtained.through the connector static load is calculated,according to the elastic contact finite element theory,static analysis using MSC.PATRAN/NASTRAN for each connector,the results of the stress calculation under different conditions are obtained.Found that flexible material placed on the inner wall of the ear canal such design has a significant effect to reduce the stress concentration phenomenon.In the end,the connector with a buffer pad is also concentrated in the earhole.Finally,using the Miner linear cumulative damage theory,the load time history according to the results of S-N life cycle curve,material stress and connector connector spectrum,using the fatigue life analysis software MSC.Fatigue of the six articulated connector for fatigue life analysis,comparison of different connectors,different flexible materials on fatigue life.connector ear canal in a certain degree of stress concentration will affect to the fatigue life of connector,the service life of pure rigid hinged connector shorter than flexible connector.