Study On Low Temperature Fatigue Properties Of Polar Ship Structure

The structure of polar ship is complex and the sailing conditions are diverse.There are two dangerous environment challenges in service process of polar ship which is which is the low temperature and the sea ice.At present,the study on the hull structure fatigue of conventional ships has been mature and thorough,however the research work on the fatigue of polar ship structure is limited.In this paper,a polar ship is taken as an example to analyze and study about the fatigue strength.The effects of low temperature environment on the fatigue strength of polar ship are considered.The main work of this paper includes the following four aspects:1)Two typical welding node fatigue strength test is carried out in low-temperature environment.The specimen are designed according to the relevant national standards and professional standards of design.The loading levels are determined according to the finite element calculation.Linear regression fitting method is used to obtain the S-N curves at low temperature and normal temperature.2)The basic principle of spectral analysis is expounded and the basic flow of wave ship fatigue strength of polar ship evaluated by spectral analysis method is described.Fatigue evaluation hotspots are directly sorted by sorting finite element coarse mesh node damage degree and analyzing dynamic response.3)The differential equation of ship's time-history motion is established.The ship ice-breaking load is solved and obtained by the Newmark method.The ship-ice collision contact area is determined by geometrical method.4)The dynamic response analysis method is used to analyze the dynamic response of the breaking ice progress,and the stress time history of ice-induced fatigue hot spot is calculated.The amplitude and mean value of the stress cycle are obtained by rain flow counting method.At last,the ice-induced fatigue strength of polar ship is evaluated.