Preliminary Evaluation of Digital Image Correlation for In-situ Observation of Low Temperature Atmospheric-Induced Chloride Stress Corrosion Cracking in Austenitic Stainless Steels

Digital image correlation has been used to observe the growth of atmospheric-induced chloride stress corrosion cracking in type 304L stainless steel under controlled conditions of temperature, relative humidity and chloride-deposition density in a non-destructive manner. The technique is capable of detecting changes in crack dimensions that are difficult to discern via conventional optical microscopy, i.e. crack growth beneath salt layers and adherent corrosion product deposits, and measurement of crack opening displacements. Our results also demonstrate that suitable specimen design, combined with digital image correlation, will provide the means of comparing the growth behaviour of short atmospheric-induced chloride stress corrosion cracks with data obtained from conventional pre-cracked compact tension specimens as a function of mechanical "driving force".