Fatigue crack initiation and growth behavior within varying notch geometries in the low‐cycle fatigue regime for FV566 turbine blade material

Plain bend bars made from FV566 martensitic stainless steel were extracted the root of ex-service power plant turbine blades and several industry-relevant notch geometries introduced. Some samples shot peened. The notched loaded plastically in low-cycle fatigue regime finite element (FE) modeling carried out to investigate effects changing geometry, combined with peening, on behaviors such as crack initiation, short growth, coalescence. Shot peening damaged surface, accelerating initiation behaviors, but had a lifetime-extending effect by retarding growth all tested geometries. At total strain range higher than 1.2%, lifetime extension benefit was diminished due compressive residual stress relaxation field. Notch geometry (and associated varying constraint levels stress/strain gradients) found have no notable difference life when at identical notch-root ranges.