# Development of Automatic Crack Growth Simulation Program Based on Finite Element Analysis
###### Abstract  
A crack growth simulation program based on the advanced iterative-finite element method (AI-FEM) was developed to predict realistic crack growth of structures. The developed program was suggested to calculate the exact stress intensity factor for arbitrary structures by regenerating the crack tip mesh as the crack grows. The main advantages of the developed program are to estimate each different crack growths along the crack tip line and to simulate the cracking transition from a surface crack to a through-wall crack under a complex stress field. For these purposes, the sensitivity analyses were performed for various influence variables on stress intensity factors, such as element types and crack dimensions. Based on the results of sensitivity analyses, the appropriate criteria for crack tip modeling to be used in AI-FEM were suggested to calculate sufficient converged SIF. The program developed in this research was validated through stress corrosion crack growth and natural crack growth examples including cracking transition, and it was confirmed that the program simulates crack growth well and has reasonable methods for cracking transition. stress intensity factor; fatigue crack growth; stress corrosion crack growth; program; finite element method +
Footnote †: journal: Applied  
shape, so that crack growths are estimated only at the surface and deepest points. However, such an evaluation method can overly conservatively evaluate the integrity of a structure as in the case of the Wolf Creek NPP, which may result in unnecessary maintenance costs [5]. This conservatism can be improved by directly evaluating the crack growth at the crack tip of a natural crack rather than evaluating the idealized crack growth. To evaluate the growth of real cracks with complex geometries, various studies have been conducted based on finite element analysis (FEA). The finite-discrete element method [6; 7; 8] has been employed for impact failure of monolithic glass, layered composite material, and functionally graded materials. Furthermore, the phase-field and extended finite element method based on damage fracture mechanics [9; 10; 11; 12] have been known to be powerful to simulate brittle cracking and anisotropic fracture. However, high nonlinearity in the numerical analysis process is unavoidable using these methods, so the applicability of these methods to various components in NPP is not fully investigated yet. For this reason, conventional FEA based on the linear elastic fracture mechanics using the spider-web mesh at the crack tip has been generally considered as the reliable approach of crack growth assessment for structures in NPP. However, high proficiency in modeling techniques is required to generate the spider-web mesh at the crack tip. To overcome these difficulties, crack growth evaluation programs were also developed based on relative research. [PERSON] et al. [13] developed ZENCRACK, a program that can simulate 3D crack growth based on Abaqus. However, this program cannot simulate the transition from a surface crack to a through-wall crack and it is difficult to accurately simulate the crack growth due to the combined load because the combined load is applied replacing it with an equivalent load. In Emc\({}^{2}\), AFEA (Advanced Finite Element Analysis), a method that can simulate crack growth through crack tip mesh regeneration without assuming a semi-elliptical crack, was developed [14]. Using this program, crack growth analysis was performed for nozzles in the PWSCC environment, and the safety margin of the structure was verified by comparing typical ASME code, Sec. XI-type analysis. As a follow-up study, [PERSON] et al. [15] simulated cracking transition as a through-wall crack by performing crack growth of a pipe with semi-elliptical inner surface cracks in a primary water environment. [PERSON] et al.