Fatigue analysis methods of crack like defects I. Strain range evaluation

Structural components of nuclear reactors may contain fabrication defects that can propagate under cyclic loading resulting from operating conditions. Such designed defects are, for example, partially penetrated weldments between two components parts. These defects present frequently very sharp extremities that may lead to consider them like cracks for analysis. In such situations fatigue analysis methods for discontinuities as proposed in construction codes like ASME III ( 1 ), Code Case N47 ( 2 ), RCC-M ( 3 ) or RCC-MR ( 4 ) are not directly applicable. Special developments are needed. Important work was performed in France in order to derive practical methods to predict fatigue initiation in crack-like defects. Roche in ( 5 ) describes some developments accomplished and presents the principles of rules based on strain evaluation at a constant material characteristic distance d from the notch tip and on the use of a design fatigue initiation curve. This study presented here was performed under financial support of the C.E.A. Safety Authorities-IPSN.