Abstract
The present research deals with external surface cracks in vertical steel tanks. Such defects occur very often. The analytical expression of stress intensity factor (SIF) is need, for prediction residual life of tanks with cracks. There are solutions for the SIF of surface cracks in hollow cylinders. However, all of them can not be used for steel tank. The main purpose of this research is to present analytical expression SIF for longitudinal external surface cracks in vertical cylindrical steel tanks. The finite element method is used for the SIF calculation of the crack in the tank. All SIF values are determined based on the submodel technique. Firstly, the whole shell model of tank without defects is generated. Real service load and tank size take into account. After that the solid submodel with crack is generated. A wide range of cracks geometries and filling level of oil are researched. The finite element models have a good agreement with wellknown analytical decisions. All SIF results are expressed with polynomial functions, that the fracture criteria can be used easily in the estimation of the residual life of tanks. SIF polynomial function should used in Paris-Erdogan equation. Results of this work could be useful for engineers in oil storage field.
Highlights
Practical observations prove that failures and accident destruction of vertical cylindrical oil steel tanks happen either in the initial operating period in the first of three years or after 15-20 years because of damage accumulation on stream
The fracture mechanical loading of the tank elements are studied using the methods of the linear fracture mechanics by determination a stress intensity factor (SIF) along the crack front
The SIF of the depth point is important for prediction residual life of vertical steel tanks with external surface cracks
Summary
Practical observations prove that failures and accident destruction of vertical cylindrical oil steel tanks happen either in the initial operating period in the first of three years (assembly defects) or after 15-20 years because of damage accumulation on stream. The SIF expresses the intensity of the stress field singularity near the crack tip. It depends on size, shape and location of the defect; the applied load and geometry of the structure according to Anderson and Sullivan (1966) and Kuna (2013). Shape and location of the defect; the applied load and geometry of the structure according to Anderson and Sullivan (1966) and Kuna (2013) It can be used in design strategies for brittle fracture and fatigue control of tanks (Alturi & Kathiresan, 1980). It is necessary to have an expression for the SIF, which describes the special geometrical and loading conditions for the estimation of the safe operating life time of tanks
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