Research On Facture Mechanics Method Of Stiffened Plate Of Ship Structure Fatigue Evaluation

Fatigue damage is one of the dominate failure modes of the ships and offshore structures, so the fatigue fracture mechanics theory has been widely recognized as the important method of structure strength analyses. Based on the crack propagation theory, the stress intensity factors and fatigue crack propagation life of a finite stiffened plate of ship structures are studied in this paper, with the hope of providing a referrence to perfect fatigue assessment of ship structures. The major contents are as follows,(1) The method of the fatigue strength assessment based on fracture mechanics is introduced, including the calculation of effective stress intensity factor, the model of fatigue crack growth rate, crack criterion and so on.(2) Based on the comparision with the stress intensity factor calculated by FEM and theoretical method, the accuracy of FEM is affirmed.(3) Effect on stress intensity factors of a finite stiffened plate under various geometric parameters is considered. Case studies are presented to illustrate the influence of geometric parameters on the stress intensity factor at the crack tip.(4) The fatigue life of a representative stiffened plate of a ship is evaluated via the stress history in random sea conditions with and without the influence of stiffener on stress intensity factors, and the results show that the stiffener plays an important role in decreasing crack growth rate and increasing the structure strength.