Study On The Fatigue Strength Of Submarine Structure By Numerical Simulation

The using rules about the fatigue strength in "Design and Calculation Standard for Submarine Structure" is worked out according to the standard that the ultimate time of submergence is less than 500. With the using of high strength steel and the development of the structure design, the fatigue strength becomes more and more prominent and the rules of design can no longer meet the demand of the design nowadays.The phenomenon of crack closure, which is important for the crack growth, is widely existed in the progress of fatigue crack growth in the metal materials. The strip-yield model based on the crack closure is used in the plane through cracks. The opening stress and the life of crack growth is calculated and compared with the test results and the experience formula. The feasibility of the Newman theory of opening stress used in the high strength steel is validated. Then through the slice synthesis method, the three dimension surface crack of the weld joint of cone-cylinder is decomposed into many plane through cracks. The strip-yield method is used to analyze those plane through cracks. Then the crack growth velocity is acquired, and the fatigue life is gotten too.The numerical simulation method based on the strip-yield method has begun to be used in the air space structures, but not used in the fatigue questions in the submarine. The numerical simulation technique is used to study on the fatigue properties of submarine with high strength steel. The numerical simulation model is established and its feasibility is validated. At last, the possibility of establishing a kind of calculation and design methods of fatigue life in submarine structure is primarily analyzed.