PSI - Issue 41

Ericha Dwi Wahyu Syah Putri et al. / Procedia Structural Integrity 41 (2022) 266–273 Putri et al. / Structural Integrity Procedia 00 (2022) 000 – 000

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Besides, determining the appropriate SCC testing method can help engineers select materials to use more advanced technology in the design process (Prabowo et al., 2021). 2. Definition of Stress-Corrosion-Cracking Stress Corrosion Cracking (SCC) is cracking in the material that occurs when tensile stress, corrosive environment, and susceptible material exist simultaneously (Ahmadi et al., 2020). The occurrence of SCC leads to premature failure of materials that are perceived as potentially dangerous. In this regard, a detailed study of the role of SCC is required to predict the strength and failure of materials and structures accurately. The following Fig. 2 describes the parameters that it causes stress corrosion cracking.

Fig. 2. The parameters of stress corrosion cracking

Tensile stress plays a crucial in the stress corrosion cracking phenomenon. The tensile stresses may be in the form of directly applied stresses, thermal, in the form of residual stresses, or a combination of all (Padekar et al., 2013; Surojo et al., 2021). The second parameter is a corrosive environment where the cracking for each metal or alloy is specific because not all environments promote the SCC, e.g., seawater, water vapor, aqueous solutions, organic liquids, and liquid metals (Nguyen et al., 2018). The last parameter is susceptible material. It requires acceleration by increasing the severity of the environment or the critical test parameters. SCC behavior could be measured using mechanical properties of the material in the air and corrosive environments such as elongation to failure, reduction in area, and ultimate tensile strength to accurately predict the strength and failure of material structures (Kannan et al., 2007; Surojo et al., 2021). The process of the SCC mechanism consists of 3 stages: the cracks initiation sites, coalescence, and fast growth to failure. The schematic of the SCC mechanism is shown in Fig. 3. Stage 1 is a phase where the cracks initiation sites and the interaction between stress fields of nearby cracks influence the crack growth during this stage. The crack initiation (or nucleation) follows a pitting corrosion kinetics model or occurs when the stress intensity factor reaches a threshold (Rokkam et al., 2019). Stage 2 is a phase where the characterized by sustainable small crack nucleation continues (secondary cracks) at multiple sites, and adjacent cracks are found to coalesce to form larger cracks. At this stage, the crack growth rate follows a power law with crack tip strain rate and can be correlated to stress intensity factor ( K ) (Niazi et al., 2021). Stage 3 is the phase where the crack growth is very rapid and unstable. The stress intensity causes it and the crack propagation rate to increase further. The rapid crack propagation at this stage may cause failure by SCC (Bagchi et al., 2019).