Fatigue Lifetimes for Pressurized, Eroded, Cracked, Autofrettaged Thick Cylinders

This paper summarizes Boundary Element Method Stress Intensity Factor solutions, obtained by the authors and presented elsewhere, for internally pressurized thick cylinders having a single longitudinal, semicircular erosion on the internal bore with radial straight-fronted and elliptical cracks emanating from the deepest point of the bore erosion.

A ratio of external to internal cylinder radii (R₀/R₁) of 2.0 is employed and a range of semicircular erosion depths varying from 0 to 40% of the wall thickness. Care is taken to determine accurate stress concentration factors for the various erosion depths in order to accurately quantify limiting values of stress intensity factor at very short crack lengths.

Employing a standard fatigue crack growth law, lifetime calculations are presented for cyclic pressurization of the bore. The results indicate that the presence of a modest semicircular erosion at the bore serves to reduce the fatigue lifetime by an order of magnitude. A similar reduction in lifetime results from the elimination of the autofrettage residual stress field.