Short and long crack growth behavior of welded ferritic stainless steel

International audienceTo analyze the influence of welding on fatigue crack growth, several geometrical configurations have been tested using notched specimens with notch located within base metal and welded joint. This methodology has shown that fatigue crack growth rate was similar for base metal and welded part for the ferritic stainless steel F18TNb (corresponding to AISI 441 or EN 1.4509 grades) considering long crack. Whereas for short crack, the microstructure induced by the welding process was evidenced to drastically increase the resulting crack growth rate. The tested configurations have been systematically modeled by finite element analysis to obtain reliable shape function and SIF assessment for the chosen geometries. Then fatigue crack growth behavior is discussed on the basis of both SIF values and the influence of microstructure in crack path and crack growth rate