| Fatigue destroy is one of main forms of ship structures destroyed. Every classification society and shipyard takes fatigue assessment rules of ship structures as an instruction to assure fatigue strength of ship structures. Although these rules are based on the method of S-N curve, different fatigue lives of the same node are obtained with the help of different rules, because the disadvantages of S-N curve could not be avoided, such as neglect of initial objection of material, fatigue strength assessment methods of ship structures are studied based on the facture propagation theory, which are supposed to reference to predict fatigue life and preparation to perfect fatigue strength assessment of ship structures.This article is to study fatigue strength assessment methods of ship structures based on the facture mechanics, and includes the following aspects:(1) Both the fatigue strength development and the ship structures fatigue strength assessment trend are reviewed.(2) Fatigue assessment methods based on the facture mechanics are introduced; conventional fatigue assessment methods based on S-N curve are also explained briefly; and the comparison between them is carried out to point out the differences and the relation between them.(3) A detailed fatigue assessment method of ship structures is proposed, which is made up of modeling FEM model, determining the loads, choosing the dimension of initial crack, stress distribution formula of typical node, power function of different crack, strength factor solution, selection of crack criteria, speed calculation of crack propagation, and fatigue life estimation of structures with crack.(4) The method based on the facture mechanics and the method based on S-N curve are carried out to evaluate the fatigue life of a ship, and the two results is compared, which indicates that the model is satisfied the requirement of fatigue life prediction.
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