Ti-6 Al-4V合金の疲労特性に及ぼす応力比の影響と高応力比側疲労寿命評価法の提案

概要

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Fatigue tests were conducted for Ti-6 Al-4V alloy under sress ratios of R=-1, 0 and 0.3, and under the condition fixing the maximum stress at the yield stress without fixing stress ratios between each data point (σ_<max>=σ_y test). Internal fracture tended to occur under high stress ratios except R=-1, in spite of no occurrence in R=-1 test. The fracture sites of the internal fracture revealed no inclusion but serveral facets. The fatigue strength determined at 10^8 cycles were below a modified Goodman line in the R=0 and 0.3 tests, although they were above under R=0.7. Besides, fatigue lives estimated with the modified Goodman line were much lower than actual results. These results meant high stress ratio tests were necessary in evaluating fatigue strength and life in the high stress ratio condition. For the high stress ratio tests, the σ_<max>=σ_y tests appeared to be a good solution.
2004-10-25