Failure Behavior of Colonies of Corrosion Defects Composed of Symmetrically Arranged Defects

Abstract

This paper presents a case study on the failure behavior of four colonies of corrosion defects using solid Finite Element models. These analyses accounted for large strains and displacements, stress-stiffening and material nonlinearity. Colonies 1 and 2 are each composed of two longitudinally aligned defects. Colonies 3 and 4 are each composed of four defects (two longitudinally aligned defects and two circumferentially aligned defects) arranged in a rhombus shape. For each of the four colonies a parametric study is performed in which the longitudinal spacing sL between the two defects longitudinally aligned is varied from a small value (sL)min to a large value (sL)max. Based on the results obtained the failure behavior of each colony is described and illustrated by contour plots of stresses. The failure pressures predicted by the Finite Element analyses are compared with those predicted by six assessments methods, namely: the ASME B31G method, the RSTRENG 085dL method, the DNV RP-F101 method for single defects (Part B), the RPA method, the RSTRENG Effective Area method and the DNV RP-F101 method for interacting defects (Part B).