Investigation on behavior of trapezoidal through-wall cracks under constant pressure loading

In general, a crack found in a steam generator tube has an elliptical shape, and as soon as it penetrates through the wall, it is assumed to be rectangular for conservatism. However, the leak and crack growth behavior have not been clearly understood after the elliptical crack penetrates the tube wall. One steam generator tube failure showed the tube rupture behavior without any significant prior indication. Several experiments using steam generator tubes with a trapezoidal crack were performed under constant pressure loading by Argonne National Laboratory and exhibited crack growth behavior much faster than expected. It has been found to be caused by time-dependent fatigue crack growth. No KI solution is available for a trapezoidal crack which can be used for fatigue crack growth analysis. The objective of this study is, therefore, to develop a new KI solution for a trapezoidal crack using FEM.