Analysis of strees concentrtion in a thick walled cylinder containing elliptical hole

Abstract

Pressure vessels used in industries usually incorporate openings in the main shell that causes local stress concentration around the opening which in turn reduces the pressure carrying capacity of the vessel. Therefore the aim of the present work is to investigate the stress concentration factor and also the stress distribution around the elliptical radial and offset holes having blended features at the intersection using finite element method. Two different orientations of the cross holes are investigated, one with the major axis of the hole along the longitudinal axis of the cylinder and another along the circumferential direction of the cylinder A finite element package ANSYS is used for the present computation. The cylindrical pressure vessels of different ratios of outer to inner diameter are analyzed using three dimensional solid isoparametric finite elements. After imposing boundary conditions and loading the vessel with internal pressure, the stress concentration factors (SCF) are obtained for some noticeable configurations of cross hole and cylinder. The comparison of principal and von Mises SCFs between equivalent circular (obtained by Hamilton et al. [11]) and elliptical radial cross holes show that elliptical cross holes reduce the SCFs around 30% and 28% respectively compared to the circular ones. Elliptical holes of circumferential orientation show about 55% reduction in SCF values than the longitudinal orientation, thus establishing that the circumferential orientation of the hole must be preferred over the longitudinal orientation. Again, the smaller offset cross holes provide a maximum reduction in principal and von Mises SCF values around 15% ad 9% respectively in comparison with the radial cross holes; thus making offset cross holes a better proposition than the radial ones.