PSI - Issue 47

L.A. Almazova et al. / Procedia Structural Integrity 47 (2023) 417–425 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

418

2

Nomenclature r

inner radius of the shell outer radius of the shell

R p

internal pressure

curvature radius of the pits

δ

h1,h2 depth of the pits D distance between the pits growth rate of pit at step k

increment of the pitting depth at step i

Pressure vessels are widely used in various industries such as chemical processing, power generation, oil and gas production. They are designed to withstand high pressure and temperature and to store, transport or process substances safely. Often being made of metals pressure vessels may undergo corrosion attack (Obeyesekere, 2017). Corrosion occurs when the metal reacts with the environment for example with the liquid or gas stored inside the vessel, leading to the degradation of the metal and eventually to the failure of the vessel (Zhao et al., 2018). Different types of corrosion damage have different levels of risk depending on the specific situation and environment. Pitting corrosion is one of the most dangerous forms of corrosion that results in a localized formation of cavities on the surface of a metal. It is caused by corrosive elements coming in contact with the metal and attacking it at its weakest points (see Liu et al (2021)). Pitting corrosion can cause a severe damage to structures, especially when the pits are deep enough. The consequences of pitting corrosion in pressure vessels may be severe, including leaks or ruptures that can cause injury or damage to equipment and the surrounding environment. High pressures may intensify the creation of cavities in the material, weakening it and causing it to fail at an accelerated rate. Finite element analysis (FEA) is known as a cost-effective way to evaluate the integrity of structures under different loads and conditions (Mechab et. al. (2020), Vakaeva, A.B., Shuvalov, G.M., and Kostyrko, S.A. (2021), Ahmed et. al. (2019), Lakhdari et. al. (2020)). Numerical analysis may help to estimate the effect of local corrosion on the overall strength of the material and structure. And to make informed decisions about the selection of materials and design of structures to ensure their safety and longevity. Note that the modelling of local corrosion is resource-intensive even taking into account the nowadays development of computer technology. That is the reason why pits are often modeled in 2D. Many authors investigated the effect of single and multiple defects on strength and buckling behaviour of structures experimentally and numerically. Single corrosion defects were addressed, e.g., by Cerit (2013), Pronina (2017) and Sedova et. al. (2014). Multiple defects in plates and shells were considered by Wang et. al. (2020), Liao et. al. (2021), (Khedmati and Nouri (2015), Zhao (2020), Kostyrko et. al. (2021); Abakarov et. al. (2022), Okulova et.al. (2022), Carpinteri et. al. (2006, 2009); Zhu et.al. (2020) and many others. As shown in some articles, the local stresses around each defect differ slightly from the stresses that arise in the vicinity of a single defect if the defects are spaced far enough apart (Sun et al., 2021). However, in many cases, closely spaced local corrosion damages can be more dangerous than single one. Interacting corrosion pits may propagate faster, increasing the material loss and decreasing its service life. The interaction between circumferentially aligned corrosion pits on a pipeline under axial tensile loads was examined in Sun et al (2021). It was discovered that as the distance between corrosion defects grows, the stress concentration close to the defects decreases, when the distance between defects surpasses a particular amount mutual interaction between the defects becomes insignificant. In order to calculate the average stress-average strain connection for steel plates with random corrosion defects on both sides while accounting for geometric and material nonlinearities, Khedmati et al. (2014) devised an analytical method to assess the plate's strength. Zhang et al. (2016) calculated the ultimate strength of hull plate with pitting corrosion damage under combined loads based on the corrosion-related volume loss. Investigations were also done on the effect of certain corrosion parameters on the ultimate strength in relation to the corrosion-related volume loss. Feng et al. (2020) conducted a parametric investigation on the impact of pitting corrosion on the ultimate strength of stiffened plates subjected to uniaxial compression. It was discovered that