may be affected in bending by compressive stressed region when crack moves into this region Smooth region plus rough region in direction of growth- cyclic loading Rough matte fractures are ductile May indicate transition from fatigue crack growth t Rubbing(general) May indicate vibration May show final direction of separation Swirl pattern indicates torsion Rubbing (localized) indicate crack closure in cyclic loading obliterate beach marks Deformed draw marks, rolling scratches If twisted, indicates torsion loading Machining marks(normal to axis of Not distorted in torsion loading component) Variable roughness of fracture edge In brittle bending. rough side is tension side Table 2 Microscale fractography features Mark/Indication Implication Dimpled fracture surface Ductile overload fracture at this location Faceted fracture surface Brittle cleavage fracture Possible scc fracture May be low△ K fatigue Intergranular with smooth Likely either improper thermal processing or environmental assisted grain boundaries fracture(high temperature, corrosive environment) Less common is low ak fatigue Intergranular with Decohesive rupture--fracture at high fraction of melting point dimpled grain boundaries Possible improper processing creating denuded zone adjacent to grain boundary River pattern or fan Cleavage fracture; crack runs"down"river fan rays point to initiation site attern within a grain(see Fig. 10) Tongues i Twinning deformation during rapid crack propagation(see Fig. 28) Flutes on transgranular Indicates corrosive environment and ductile fracture fracture surface Crack propagates parallel to flutes Striated or ridged fracture Cyclic loading fatigue striations; Constant spacing, constant stress amplitude; variable spacing, variable stress amplitude or block loading (see Fig. 52 Striated surface caused by second phases in microstructure(see Fig 51) Grooves or flutes SCC TGF Artifacts(mud cracks) Dried liquid on surface May indicate incomplete cleaning of surface. If in the as-received condition, may indicate fluids from service and may indicate scc Thefileisdownloadedfromwww.bzfxw.com(may be affected in bending by compressive stressed region when crack moves into this region) · Smooth region plus rough region in direction of growth— cyclic loading · Rough matte fractures are ductile · May indicate transition from fatigue crack growth to overload Rubbing (general) · May indicate vibration · May show final direction of separation · Swirl pattern indicates torsion Rubbing (localized) · May indicate crack closure in cyclic loading · May obliterate beach marks Deformed draw marks, rolling scratches If twisted, indicates torsion loading Machining marks (normal to axis of component) Not distorted in torsion loading Variable roughness of fracture edge In brittle bending, rough side is tension side Table 2 Microscale fractography features Mark/Indication Implication Dimpled fracture surface Ductile overload fracture at this location Faceted fracture surface · Brittle cleavage fracture · Possible SCC fracture · May be low ΔK fatigue Intergranular with smooth grain boundaries · Likely either improper thermal processing or environmental assisted fracture (high temperature, corrosive environment) · Less common is low ΔK fatigue Intergranular with dimpled grain boundaries · “Decohesive rupture—fracture at high fraction of melting point · Possible improper processing creating denuded zone adjacent to grain boundary River pattern or fan pattern Cleavage fracture; crack runs “down” river; fan rays point to initiation site within a grain (see Fig. 10) Tongues Twinning deformation during rapid crack propagation (see Fig. 28) Flutes on transgranular fracture surface · Indicates corrosive environment and ductile fracture · Crack propagates parallel to flutes Striated or ridged fracture · Cyclic loading fatigue striations; Constant spacing, constant stress amplitude; variable spacing, variable stress amplitude or block loading (see Fig. 52) · Striated surface caused by second phases in microstructure (see Fig. 51) Grooves or flutes · SCC · TGF Artifacts (mud cracks) Dried liquid on surface. May indicate incomplete cleaning of surface. If in the as-received condition, may indicate fluids from service and may indicate SCC The file is downloaded from www.bzfxw.com