A Study On Fatigue Assessment Of Ship Structures And Stress Analysis Methods Used

Fatigue is an important failure mode for ship structures. Over the last decades, with the intensive usage of high-tensile steel in ship structures and use of ships of large dimensions, great attention has been paid to how to reasonably assess the fatigue strength of ship structures. This paper expatiates on elements of fatigue assessment and general methods for fatigue strength analysis of ship structures. Special emphasis on the simplified method for fatigue assessment is given to with comparison among the methods of several classification societies. On the basis of these, this paper pays more attention to stress analysis methods used in fatigue assessment of ship structures.The main aspects studied in this paper are as follows:1 Elements of fatigue analysis and general methods for fatigue strength analysis of ship structures is expatiated on, with emphasis on S-N approach.2 The general elements and essential approach of simplified method of fatigue assessment for ship structures is studied. Comparison among the approaches of different classification societies is performed and the reason of the difference is sought for. The formulas of the horizontal wave bending moment and the external pressure loads are paid more attention to.3 Stress analysis method Discussing the difference among nominal stress approach, hot-spot stress approach and notch stress approach and an emphatic comparative study of nominal stress approach and hot-spot stress approach is performed. Different finite element models and extrapolation methods are used in calculating hot-spot stress of a simple detail for studying the numerical procedures and extrapolation methods. It constituted a computational model for a typical detail based on general finite element method program of ANSYS. The parametrical analysis by varying dimensions of lug and cut-out was carried out in order to disclose the dimensional effects on the hot-spot stress.4 Effects on fatigue life of some factors and improvement of fatigue life...