Estimating Remaining Ductility of Corroded Steel by Using Surface Roughness Characteristics Based on Tensile Coupon Test Results

Abstract

Corrosion may cause not only a reduction in thickness but a change in the surface geometry, as well. Recent studies have shown that ductility capacity is reduced by the presence of corrosion surface roughness. The current study investigated the role of the surface roughness in the reduction of the static ductility. Standard uniaxial tensile tests were conducted on corroded steel plates exhibiting varying surface roughness characteristics. The specimens were obtained from naturally corroded steels having different material properties and corroded in different environments. First, 3D surface heights measurements were performed to obtain surface profile data for statistical quantification of surface roughness features. The remaining load and elongation capacities were determined experimentally from the tensile tests. The distribution of the surface strains was studied employing digital image correlation techniques. From this work, the mechanism of ductility decrease was confirmed to proceed as follows: Surface unevenness due to corrosion was found to cause stress concentration and uneven yielding, and strain localization after yielding during the tensile test. This translates to an early necking initiation, resulting in reduced ductility in corroded specimens. Finally, empirical equations for estimating remaining ductility of corroded steel based on surface roughness characteristics are proposed.