Numerical Analysis of Tensile Behavior of Stainless Steel SS304 With Corrosion Pits

Abstract

Pitting corrosion is one of the leading causes of structural failure in marine and aerospace applications, as fracture initiates from the pits. The pitting phenomenon is one of the less predictable forms of corrosion; it is a localized corrosion of a metal surface where small areas corrode preferentially, leading to the formation of cavities or pits. In this study, numerical simulations are performed on an austenitic stainless steel (SS 304) dog-bone specimen of a thickness of 6 mm with spherical pits and different shapes of pits as per the ASTM G46-21 standard, as well as with different aspect ratios of pits. The pits were placed either in-line with the loading direction and different orientations, apart from random position of corrosion pits. It was observed that there is a reasonable decrease in the toughness of the sample with pits compared to no-pit conditions. The inline orientation of pits is found to be more harmful than the random orientation of pits, as the decrease in strength and stiffness is more. The different-shaped pits will initiate the failure faster than the identical (spherical) pits. In comparing inline and random orientations, for all aspect ratios and orientations, the highest tensile force is observed for pits with a random orientation and an aspect ratio of 1.76, while the minimum force is seen in spherical pits with a random orientation and an aspect ratio of 1.56. As the aspect ratio increased, strength initially decreased and then increased. Pits with a 1.76 aspect ratio showed greater strength and toughness, whereas the 1.56 ratio demonstrated poor performance. The spherical pits have a lower stress concentration factor (SCF) than different shapes of pits. Random orientation of pits with an aspect ratio of 1.76 had the highest SCF of 3.508, while spherical pits with an inline orientation and a 0.69 aspect ratio exhibit the lowest SCF of 2.866. As the aspect ratio increases, there is a corresponding increase in SCF across all pit shapes and orientations.