人工切欠きを持つ浸炭歯車の曲げ疲労強度

概要

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The fatigue strength of carburized gears is influenced by the surface integrity, namely, the roughness, structure, hardness and so on. The most notable parameter of surface integrity is the latent defect. To clarify the influence of the latent defect, the bending fatigue strength of carburized gears with an artificial notch is evaluated in this paper. The notches over 50,μm depth are processed　by wire-cut electrical discharge machining. The notches of 10 to 50,μm depth are etched by focused　ion beam (FIB). The fatigue strength of the tooth with the notch over 35,μm depth greatly decreases　in comparison with the non-notched tooth. In the case that the notch is shorter than 20,μm, the bending strength as well as the crack initiation is not practically influenced by the crack. Therefore threshold notch depth a(nth) which does not affect the fatigue strength is estimated as 20,μm. By assuming a crack of the same length as the notch, the stress intensity factor K1 is calculated considering the effect of residual stress. The fatigue strength of gears with artificial notch are lower then those expected from the threshold stress intensity factor range.
1999-04-25