Fatigue Strength Analysis Method Study Of Complex Cabin Structural Naval Ship

At present, research on methods of Naval Architecture and Ocean Structure fatigue strength assessment is very extensive and profound. A variety of common methods to fatigue strength assessment has been matured. However, these widely used methods are mainly aimed at regular ships,researches on Complex Cabin Structural Naval Ships (referred to as CCSNS),on the other hand,failed to develop a complete procedure or design consideration of corresponding fatigue strength assessment. Compared to regular ships,such as bulk cargo or oil tanker, numerous factors of CCSNS, such as complex hull structure and diverse sailing conditions, have led to a highlighted fatigue problem. Taking a CCSNS for example, a suitable method for CCSNS fatigue strength assessment is explored in this paper. The main contents of this paper are as follows:1) Four fatigue strength assessment rules are detailed comparative analyzed to manifest the differences between them. The feasibility of the four rules' application in the hull structural fatigue strength assessment of CCSNS is discussed.2) Due to the complex hull structure, diverse sailing conditions and numerous typical nodes, the fatigue check positions to be considered in CCSNS is correspondingly large. In order to solve the problem of fatigue check positions selection,a finite element coarse mesh fatigue hotspots screening method based on spectral analysis is put forward in this paper to determine the fatigue node positions of the target ship.3) The direct computing based on design wave method is adopted in the fatigue damage calculation of the checking positions in the target ship. The calculation results are compared to ones of spectral analysis method to investigate the application of design wave method to fatigue strength assessment of CCSNS.4) Fracture mechanics method is used to calculate the fatigue lives of the typical welded structures of the target ship. A criterion is obtained in the comparative analysis of calculation results of different initial crack size. The application of fracture mechanics method in the welded structures' fatigue evaluation of CCSNS is also detailedly discussed.5) The calculation results of rules simplified methods, spectral analysis method, design wave method and fracture mechanics method are comparative analyzed. With all the advantages and disadvantages of each method taken into consideration, an ultimate integrated method is put forward in the fatigue strength assessment of CCSNS.