Research On Fatigue Strength Analysis Of The Ice-going Ship

In recent years,ice in the polar region is melting rapidly,and there are more navigation activities in these areas with the intensification of global warming.Polar fisheries emerge to enhance the decline of marine fisheries.Ice-going ships have been operating in the Antarctica for a long time,which not only suffer from the wave loads,but also inevitably collide with the brash ice in the voyage.The loading induced by waves and ice are the main source of fatigue damage for hull structure.Moreover,once the damage occurs,the pollution would be difficult to eliminate because of the lack of light,low temperatures and high winds.Therefore,it is necessary to research on the fatigue strength assessment of ice-going ships.The object of this paper is to investigate the fatigue damage analysis of the structure induced by wave loading and ship-ice collisions,and analyze the fatigue strength of hot spots in its designed life,in which a krill factory trawler is taken as the research object.The result can offer a reference for the antifatigue design and structural optimization of ice-going ship.The main works of this paper are summarized as follows:1.The procedure of fatigue strength analysis under wave loading and the basic principle of spectral analysis were reviewed,and the formula of cumulative fatigue damage was derived.2.The finite element model of the ice-going ship was established and the hot spots in the ship shoulder position were selected according to the CCS specifications and the structural stress analysis.The ship motion and wave load in regular waves were calculated through the basis of the 3D linear potential flow theory and applied to the finite element model to obtain the transfer function of the stress response.Based on the S-N curve and the linear cumulative fatigue principle,the fatigue damage of typical parts under the wave loading was evaluated.3.The numerical simulation models about the ice-going ship and brash ice fields were established.The time-history curves of the ice resistance and hull stress responses were obtained.The numerical simulation results were compared with the measured datas and model test results,confirming the effectivenes of the numerical model.The Rayleigh separation method was used to extract the stress ranges.The fatigue damage of hot spots under ice loading was evaluated according to the formula of cumulative fatigue damage.4.According to the working conditions,the fatigue damage under the effect of wave loading and ice loading was combined with their respective distribution coefficients,to evaluate the fatigue strength of hot spots in the entire design life cycle.