Effects of the corrosion pitting parameters on the mechanical properties of corroded steel

Abstract

To study the effects of corrosion on the mechanical property of corroded steel, the standard monotonic tensile tests and corresponding finite element (FE) simulations with a modified fracture criterion to analyze the ductility degradation and fracture behaviour are systematically conducted on corroded steel specimens. The results showed that the degeneration of the mechanical property of corroded steel is mainly affected by the presence of single or double critical pits, the pit sizes (a or c), as well as the spatial distance (S) between the adjacent critical pits; the spatial parameter must be ignored during the interaction of the adjacent critical pits. The strength and deformation of the corroded steel rapidly degenerated because the critical pit led to the prematurely initiated ductile cracks, which were enhanced by the presence of double critical pits, as their interactions facilitated a faster accumulation of local plastic strains on the specimen; The initiation and propagation of local ductile cracks were closely associated with the critical pits because of the loss of sectional stiffness near the critical pits. By increasing the pit size and reducing the spatial parameter, the effect of the critical pit on local ductile crack evolution gradually increased, and the stress triaxiality was continuously elevated; thus, the equivalent deformation capacity defined by the equivalent plastic fracture strain (εplf) was reduced. Finally, an all-encomplete concept, including fracture initiation and propagation, was employed with the FE analysis to distinguish between the contributions of different pitting parameters on the ductility degradation of corroded steel.