Parametric investigation of 3-d mixed mod cracks in spherical pressure vessels

Spherical pressure vessels, capable of storing high volume products under high pressure, are among undispensible elements for plants. Nowadays, spherical pressure vessels can be used especially in areas such as petrochemistry, fertilizer industry and liquid gas. Since spherical pressure vessels are prone to crack formation because of the difficulties in the manufacturing processes, fracture mechanics calculations are very important for design of spherical pressure vessels. In this study, for internally pressured spherical vessels having cracks on any of internal or external surface, having different sizes and wall thickness according to its internal or external surface normality, internal or external surface cracks are analyzed by utilizing FCPAS program and mixed mode stress intensity factors are calculated. It is aimed to form a mixed mode stress intensity factor library for internal or external surface cracks which may be met and are not perpendicular to vessel surfaces. The parameters chosen in the analyses are as follows: ratios of outers/inner diameter (Ro/Ri), crack depth/wall thickness, (a/t), crack depth/crack length (a/c), the deflection angles between crack and horizontal axis. Effect of changing of all these parameters surface on stress intensity factor are examined systematically.