310 Ti-6Al-4V合金の高サイクル疲労特性と応力比の相関(OS1-2 高強度材の超高サイクル疲労(2))(OS1 高強度材・表面改質材の疲労と破壊)  [in Japanese] 310 The Relation between High-Cycle Fatigue Characteristics and Stress Ratio of Ti-6Al-4V Alloy  [in Japanese]

To investigate the interrelation between high-cycle fatigue behavior and stress ratio (R=σ_<min>/σ_<max>), uniaxial fatigue tests were carried out under two different stress ratios, R=-1 and -0.5. The results are as follows: (1)The difference of stress ratios had a great influence on mechanism of interior fracture. (2)When stress ratios were negative, softening type fracture sometimes occurred. (3)Stress ratios had significant effect on aspects of fracture surface. (4)It is inappropriate and risky to apply modified Goodman diagram to the evaluation of a long fatigue life where interior fractures occur.