| Budget Amount *help |
¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2011: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2010: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2009: ¥2,340,000 (Direct Cost: ¥1,800,000、Indirect Cost: ¥540,000)
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| Research Abstract |
Twin deformation occurs in the early stage of high-cycle fatigue tests at low temperatures in Ti-5Al-2.5Sn extra-low interstitial alloy. Twins formed during cyclic loading leads to a fatigue crack initiation at twin/matrix interface, probably resulting in the degradation of the high-cycle fatigue properties at low temperatures. The effect of the stress ratio R(the ratio of minimum stress to maximum stress) on the high-cycle fatigue properties was investigated at 293 and 77 K. The fatigue strength at 10^7 cycles at 77 K became much lower than that at 293 K as the stress ratio decreased, implying that the twin deformation has much effect on the fatigue properties at the low stress ratio condition. Furthermore, the fatigue strength fell below the modified Goodman line for 77 K, meaning that the high-cycle fatigue properties of this alloy show an anomalous mean stress dependency at low temperatures.
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