Fatigue growth of internal flaw: Simulation of subsurface crack penetration to the surface of the structure

• A fatigue crack growth simulation system for the penetration of inner cracks to a surface is developed.
• The system is fully automated and employs the s-version Finite Element Method (s-FEM).
• The system gives an adequate accurate estimation of the stress intensity factors.
• We showed the proximity rules are conservative and can be optimized for more efficient inspection.
• S-FEM successfully simulates the crack growth process with the penetration of fatigue cracks.

In the maintenance code for nuclear power plants, initial defects are modeled as elliptical cracks in a plane normal to the tension loading direction. However, in the S-FEM simulation the defect shape, which is subjected to multi-axial loading, is realistically modeled, and the crack growth due to fatigue can be simulated. The conservativeness of the maintenance code is discussed. Parametric studies are conducted by S-FEM for examination of this problem. A simple new proximity rule was proposed, and the results of this new rule are found to be reasonable and conservative.