Generalized expressions for stress concentration factors of pipeline plain dents under cyclic internal pressure

The present work follows a previous study devoted to developing a new methodology for fatigue life assessment of steel pipelines with plain dents, under cyclic internal pressure, based on the estimation of SCFs to modify appropriate S–N curves. SCFs were estimated from a non-linear finite element model and the methodology was validated according to experimental results. A comprehensive parametric study was then carried out for spherical, longitudinal and transverse plain dents, with varying pipe and dent dimensions, and analytical expressions to provide SCFs were developed for each dent type. The aim of this work is to simplify these expressions, which have the disadvantage of being related to particular dent types (geometries). Here, a new analytical formulation is developed and simpler expressions are obtained to estimate SCFs. The proposed methodology becomes then more practical and easy to be used in the fatigue life assessment of steel pipelines with plain dents of different types, based only on measurements of dent dimensions without the need of classifying them according to their types.