船殻局部構造の疲労破壊寿命についての試計算

概要

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Fracture mechanics approaches have extensively been applied in the estimation of safety against fatigue fracture in ship hull structures. Fatigue failure often depends on the stress concentration, discontinuities in geometrical shapes and stiffness of local elements in the structure. This paper presents a series of numerical calculation on fatigue crack growth around a man-hole in a double hull structure. Stress analyses were performed both by an ordinary finite element method and by a special one which used a substructure with a singular element in the crack tip region so as to calculate the stress intensity factors. Crack growth was analyzed by using Paris' formula. The direction of crack growth was determined by σ_θ criterion. A simplified analysis was tried for the calculation of the stress intensity factor using a semi-infinite plate model and the numerical results of the ordinary finite element analysis without crack. The influence of the parameter m in Paris' formula to fatigue life was as well discussed.