圧延集合組織を有する純チタン膜材の疲労き裂進展挙動に及ぼす負荷方向の影響

抄録

Rolled pure titanium films were fatigued. The film was adhered to a through elliptical hole in a base plate and was fatigued in accordance with the displacement constraint along the hole circumference in the base plate subjected to a cyclic stress. Commonly, a stress intensity factor range was increased with a crack propagation under a constant stress amplitude but was decreased toward the hole edge because of the difference in thickness between the film and the base plate in this ΔK-decreasing test method. The crack propagation test was conducted for pure titanium films with the thickness of 30μm under three loading directions, parallel, transverse and 45degree to the rolling direction. As a result, fatigue cracks propagated faster in the specimen loaded to the rolling direction than in that loaded to the transverse direction and intermediate behavior was indicated in the specimen loaded to 45degree. From the crystal orientation analyzed by EBSD method, slip lines caused by the prismatic slip were observed around the fatigue crack in the specimen loaded to 45degree. On the other hand, the fatigue crack propagated along the prismatic planes for the high stress amplitude while that often propagated along the pyramidal planes for the low stress amplitude.