Stress concentration factor estimation for corroded steel plates using the surface gradient method

Abstract

Pitting corrosion occurs in steel components as a stress-accumulating surface irregularity that is vulnerable to fatigue crack nucleation. In this study, stress distribution in sinusoidal surfaces was investigated to devise an estimation method for the stress concentration factor (SCF) fluctuations of corroded steel. An SCF equation for sinusoidal surfaces was developed from empirical data based on three parameters: wavelength, thickness, and position. For corroded surfaces, successive numerical differentiations can be performed on each point to determine the sinusoidal surface having a point sharing the same gradient information. Notably, the SCFs of corresponding points are comparable; SCF estimation is made feasible for irregular surfaces through sinusoidal surfaces. In two-dimensional sections, maximum error was below 5% at pits and 15% for the surface. In three-dimensional models, maximum error was below 20% at pits for wide-ranging corroded specimens. Therefore, the proposed method effectively estimates SCF for identifying areas at risk of fatigue cracking.