Analyses on interaction of internal and external surface cracks in a pressurized cylinder by hybrid boundary element method

Abstract

This paper presents a comprehensive range of analyses on the interaction of two identical semi-elliptical surface cracks at the internal and external surfaces of a pressurized cylinder. The considered ratios of the crack depth to crack length are b/ a=0.25, 0.5, 0.75 and 1.0; the ratios of the crack depth to wall thickness of the cylinder are 2 b/ t=0.2, 0.4, 0.6, 0.7 and 0.8. Forty crack configurations are analyzed and the stress intensity factors along the crack front are presented. The numerical results show that for 2 b/ t<0.7, the interaction leads to a decrease in the stress intensity factors for both internal and external surface cracks, compared with a single internal or external surface crack. Thus for fracture analysis of a practical pressurized cylinder with two identical semi-elliptical surface cracks at its internal and external surfaces, a conservative result is obtained by ignoring the interaction.