β型チタン合金の内部疲労き裂発生挙動に及ぼす応力比の影響

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rights: 本文データは社団法人日本機械学会の許諾に基づきCiNiiから複製したものであるThe effect of stress ratio (R=σ_<min>/σ_<msx>) on subsurface fatigue crack initiation behavior in high-cycle fatigue of beta-type titanium alloy, Ti-15V-3Cr-3Sn-3Al, was investigated using smooth specimen subjected to axial reversed loading in air at room temperature. Two types of microstructure prepared using different aging time conditions included the partially precipitated alphaphase in beta-phase and the fully precipitated one. The first part of S-N curves at high stress amplitude region tested under R=-1 and 0.05 looks similar to curves reported in the literature, however after the curve flattens out there was a sharp drop in the fatigue strength at low stress amplitude region, accompanying a transition of crack initiation site from surface to interior. The number of cycles to the transition depended on R but did not depend on the microstructure. Fatigue fracture of all specimens tested under R=0.5 and 0.7 showed the subsurface crack initiation. No defect was observed at the subsurface crack nucleation sites, but the region of the nucleation site had a grain morphology of facet pattern. Limit of fatigue fracture occurred by surface crack initiation was controlled by the threshold of formation of slip in beta-phase due to cyclic hardening, and described by the Gerber-relationship characterizing mean stress effect.
一般社団法人日本機械学会の論文
1998-10-25

β型チタン合金の内部疲労き裂発生挙動に及ぼす応力比の影響

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