Ti-6Al-4V合金のギガサイクル疲労特性における速度効果(非鉄材料,<特集>ギガサイクル疲労)

概要

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The effect of frequency on giga-cycle fatigue properties was investigated for 900-MPa-class Ti-6Al-4 V alloy of three heats (heat A〜C) with smoothed specimen and with 0.3mm-hole-notched specimens. Fatigue tests were carried out at frequencies of 120Hz, 600Hz and 20kHz, using electromagnetic resonance, high-speed servohydraulic and ultrasonic fatigue testing machines, respectively. Heats A and B developed internal fractures, and in that case, frequency effects were negligible. On the other hands, heat C revealed only surface fracture. In this case, high frequency tests showed higher fatigue strength, i.e. frequency effects were not negligible. The tests using notched specimens hardly not revealed frequency effects regardless of the heats. The frequency effect observed in the cases of surface fracture were considered to relate to the delay of local plastic deformation reacting to the high frequency loading, since the temperature increase of specimens were successfully suppressed. The delay of plastic deformation was found to be reduced in the notched specimens, because of stress concentration and limitation of plastic deformation zone. In turn, the significant conclusion of this research was that the high frequency tests could be applicable not only to internal fracture but also to notched problem, while those were not to surface fracture of smoothed specimens.
一般社団法人日本機械学会の論文
2004-08-25