Ti-6Al-4VのCold Dwell Fatigue特性および寿命評価に与える試験応力とミクロ組織の影響

抄録

Low cycle fatigue life of Ti and Ti alloys decreases due to tensile stress dwell even at ambient temperature. This phenomenon is called Cold Dwell Fatigue (CDF). CDF properties are affected by dwell time, test stress, and microstructure. In our previous study, the effects of dwell time and the life assessment by linear cumulative damage rule were reported. The effects of test stress and microstructure for CDF properties and life assessment are discussed in this study. Test stress was from 0.85 to 0.955 σ_0.2 and influenced fatigue life. As for strain accumulation during stress dwell, rupture time was affected by both test stress and microstructure. On the other hand, rupture elongation was affected by only test stress. Considering stress dependence on rupture elongation was important for ductility exhaustion rule in linear cumulative damage rule and lead to calculation of creep-fatigue damage as D_F+D_C~1 (D_F: fatigue damage, D_C: creep damage).