高速度工具鋼の超高サイクル疲労強度特性に及ぼす表面残留応力および介在物寸法の影響

概要

論文の詳細を見る
Fatigue properties in high cycle and very high cycle fatigue regime of high speed tool steel (0.7C-0.1W-3Mo-2V) were investigated through the experimental results obtained from a cantilever-type rotary bending fatigue test in air at room temperature using hourglass shaped specimens. Two kinds of specimen were processed by grinder and cutting tool, which led to different surface compressive residual stress. Both specimens showed clear duplex S-N curve, composed of three types of failure mode depending on the stress amplitude, such as, a surface inclusion-induced failure mode (S-mode), a subsurface inclusion-induced failure mode without (I-mode) and with granular bright facet (GBF) area in the vicinity of inclusion (IG-mode). The transition of the failure mode from S-mode to I-mode and from I-mode to IG-mode was occurred at high stress amplitude level by the large compressive residual stress on the surface layer. A map of the appearance of failure modes relating the stress amplitude with the residual stress was proposed and showed a good agreement with the experimental results. The dispersion of fatigue life in the both specimens was explained by the consideration of an inclusion size at crack origin. S-N curve depended on the inclusion size was provided with the estimation of crack growth rate from the S-N data.
2009-11-25