Research On Local Corrosion Fatigue Properties Of Pressure Structure Of Submarine

The submarine is a naval vessel with high concealment capability. It not only can involvein the fighting on the water, but also can raid enemy under the water. So it has a greatdeterrent force. In order to improve the concealment capability, security, mobility and otherfighting performance, submarines require regular floating and diving which can lead to thefatigue damage. In addition, seawater as a corrosion medium which long-term contact withsubmarine pressure hull structure will not only reduce the geometric dimensions of the part ofthe members, leading to a serious decline in their ability to resist deformation and destruction,but also form new sources of fatigue, greatly reducing the fatigue life of the submarinepressure hull. After a lot of study, people found that the evaluation of the submarine servicelife obtained from fatigue or corrosion respectively is quite different from the actual situationand people can`t get an ideal evaluate results. So the evaluation of the submarine service lifeunder the common action of corrosion and fatigue is meaningful for practical engineering.This paper treats the local corrosion fatigue problem of the submarine pressure hullstructure as the research object, and put forward a method to estimate the local corrosionfatigue life of the submarine pressure hull structure. The method is consisted of the finiteelement analysis and the local stress-strain fatigue analysis approach which is based on theCoffin-Manson theory. The specific content of this paper are shown as follows:(1).Make the statics analysis of the complete submarine pressure structure through thefinite element method in order to find out the position of the maximum equivalentstress when the submarine pressure structure is under hydrostatic pressure, and if thelocal corrosion defect appears in this position, it will make the maximum fatiguedamage. Then make the statics analysis of the submarine pressure structure with alocal corrosion defect in order to obtain the response of stress and strain, and theamplitude of stress and strain will be determined by the response of stress and strain.(2).Use the multiaxial fatigue life prediction model which base on the Coffin-Mansontheory to estimate the fatigue life of the structure with a local corrosion defect whendifferent surface roughness has been considered. According to the estimation results,analyze the impact of localized corrosion defect size on the fatigue life of the structure, the impact of surface roughness on the fatigue life of the structure and theestimate effect of the different multiaxial fatigue life estimation model.(3).Use the above method to estimate the local corrosion fatigue life of the submarinepressure hull when the submarine subjected to cyclic external load, and analysis thechanging of submarine local corrosion fatigue life trends with the dive depthchanges.(4).Based on the cumulative damage theory, using the results obtained from the localcorrosion fatigue life calculation, try to analyze the impact of the continuingcorrosive effect on the fatigue life of the submarine pressure inside the casing.