| Abstract:In order to analyze the influence of geometric discontinuities (mortise and groove, etc.) of turbine disk rim on fatigue crack
initiation and small crack propagation behavior, a structure characteristics simulation specimens were designed based on the actual
configuration of an FGH96 powder disc, naturally-initiated small crack propagation tests of the specimens were carried out under high-
temperature conditions. The fatigue crack initiation and small crack propagation behaviors of the mortise and groove and bolt-hole
structure simulation specimens at 500℃ were observed and analyzed by fatigue interruption tests and surface replication techniques. The
results show that there are multi-site crack initiation phenomena on the notch surface of the two structural simulation specimens. With the
stress level decreases, the location of crack initiation changes from surface grain boundaries to near-surface specific crystallographic facets
and non-metallic inclusions. The crack initiation life accounts for about 36% to 73% of the total predicted fatigue life for the two kinds of
structure simulation specimens, and increases with the decrease of stress level. The crack initiation life is about 82% to 96% of the total
predicted fatigue life when the crack propagates to the detectable size, and the influence of stress level is relatively small. High-level
plastic deformation near the notch leads to the disappearance of the segmented characteristics in the small crack propagation rate, and
delays coalescence behavior during crack propagation, extending the crack propagation life. |
