# Crack Extension Analysis of Atmospheric Stress Corrosion Based on Peridynamics
## 1 Introduction  
Atmospheric stress corrosion (ASCC) is the phenomenon of the stress corrosion cracking (SCC) of metals in the atmospheric environment and is one of the most prevalent and hazardous forms of metal corrosion. Metallic materials are subject to varying degrees of atmospheric corrosion from raw material inventory and component processing to assembly and service. Some common examples can be observed in land, water, and air transportation systems; electronic circuit boards; and urban and marine infrastructure. The degradation of metals due to atmospheric exposure has a significant impact on society [1]. According to recent reports, economic losses due to corrosion are estimated to be 3.4% of the global GDP, and losses due to atmospheric corrosion failure account for approximately more than 50% of losses in the overall corrosion field [2]. Stress corrosion cracking (SCC) is the process of rupture of a metallic material under the combined effect of stress and the corresponding environment. Stress corrosion cracking occurs in many common metallic materials in the corresponding environment, and in some harsh stress corrosion systems, stress corrosion in the material can even occur within a few minutes. The initial formation of SCC is microcracking, followed by the continuous expansion and fusion of microcracks to form macroscopic cracks. The environments in which SCC occurs are usually acidic, alkaline, and high-temperature water. According to the corrosion mechanism, SCC is split into two types: anodic dissolution (AD) and hydrogen embrittlement (HE) [3]. Regarding the AD mechanism, under the combined influence of stress and the medium, the metal is dissolved by electrochemical reactions in the medium, resulting in crack creation and extension. The AD stress corrosion mechanism includes the slip dissolution mechanism, oxide film cracking mechanism, selective dissolution mechanism, and corrosion-promoted plastic deformation mechanism [4, 5]. In the hydrogen embrittlement mechanism, hydrogen atoms diffuse into the metal matrix and become trapped by various hydrogen traps [6]. The metal matrix exposed tohydrogen becomes brittle due to reduced ductility, followed by cracking under stress. The hydrogen-enhanced debonding process, hydrogen-enhanced local plasticity, adsorption-induced dislocation emission, hydride production, cleavage, and other HE stress corrosion mechanisms are the most common [7; 8; 9; 10]. During the atmospheric stress corrosion of metals, the variation of thin-film electrolyte thickness is a major factor in determining the corrosion rate and corrosion mechanism [11; 12; 13; 14; 15; 16]. For example, the corrosion rates of iron [14; 16] and steel [17; 18; 19; 20] are significantly higher in uniform electrolyte thicknesses of 10-30 \(\upmu\)m than in monolithic electrolyte or immersion conditions [14; 16; 17; 18; 19; 20], and the maximum corrosion rate of zinc occurs at electrolyte thicknesses of 8-10 \(\upmu\)m [21; 22]. However, the thickness of thin-film electrolytes is affected by many factors, such as the temperature, relative humidity, wind, rainfall, and contaminants in the air and on the metal surface [23; 24; 25; 26; 27]. These environmental factors have an important influence on the thickness of the electrolyte, and this influence is both profound and extremely complex. The complexity is mainly due to the following reasons: these environmental factors are not constant and change dynamically, not only with time but also with spatial shifts; the effects of these environmental factors on the electrolyte thickness are not independent of each other but interact with each other. Furthermore, these environmental factors interact with each other and cause dynamic changes in each other. ASCC has become an important research area for stainless steel because of the characteristics of sudden onset, large damage, and being difficult to monitor. Simulating the crack sprouting and expansion in materials plays an important role in the reliability analysis and health monitoring of engineering structures.