Crack Growth Evaluation of Nozzle Corner Cracks Using the JSME Code Case and Existing Solutions

Abstract Results of fatigue crack growth analysis were compared to validate the JSME Code Case which provides analytical solutions for nozzle corner cracks. The JSME Fitness-for-Service (FFS) Code requires evaluation of structural integrity when cracks are detected at a nozzle corner. However, a stress intensity factor (SIF) solution for nozzle corner cracks is not provided in the JSME FFS Code. A SIF solution for nozzle corner cracks was investigated by finite element analysis using 3D models and existing SIF solutions. An appropriate and conservative approach was selected on the basis of comparisons of SIF results. The JSME proposed a unique approach to for calculating SIFs of nozzle corner cracks that uses flat plate solutions provided in the current FFS Code combined with crack characterization. In the crack characterization, a quarter-circle crack at a nozzle corner is characterized as a semi-elliptical crack in a flat plate. Crack size and thickness of the flat plate are determined from corner crack dimensions and nozzle/shell geometries. The Case provides SIF solutions for a nozzle with a quarter-circle corner crack subjected to internal pressure and enable analytical evaluation of fatigue. The effect of the SIF solutions on fatigue crack growth analysis was investigated by comparing the analysis results obtained by using the Case solution and existing solutions. As a result, the Case solution is nearly the same as existing solutions or conservative.