組合せ荷重下にある微小穴材の疲労強度に及ぼす位相差と平均応力の影響の予測

概要

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A criterion is presented that allows us to predict the effects of phase difference and mean stress on the fatigue strength for hole-containing components subjected to combined load. Combined axial and torsional fatigue tests were conducted using annealed S35C and quenched/tempered SCM435H specimens containing a small hole of either 100μm or 500μm in diameter. The phase differences between axial and torsional loads were 0 and 90°. Effects of mean or static stresses were also investigated. The non-propagating cracks emanating in the radial direction from the holes were observed at the fatigue limit. Under the same loading condition, they were present on a plane inclined at the same angle to specimen axis. This suggests that a crack on this specific plane, a critical plane, would play an important role in the determination of fatigue strength. A criterion was proposed on the basis of the assumption that at the threshold level, the time-variation in the mode I stress intensity factor of a crack under multiaxial cylic loading is equal to that under uniaxial cyclic loading. Using this criterion, a prediction method of fatigue strength was also presented. This method is useful since no fatigue test is necessary in making predictions. Good agreement between predictions and experimental results was obtained.
一般社団法人日本機械学会の論文
2005-11-25