組合せ応力をうける球状黒鉛鋳鉄の疲労強度評価

概要

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Spheroidal graphite cast iron has many graphite nodules and other casting defects such as microshrinkage cavities in the structure. These small defects cause reduction and scatter in the fatigue strength. In this study, rotating bending, reversed torsion and in-phase combined axial/torsional fatigue tests were carried out on smooth round-bars of FCD 400, FCD 600 and FCD 700. The fatigue limit was determined by the threshold condition for propagation of a small mode I crack emanating from small defects. Using both the multiaxial fatigue fracture criterion derived based on this observational result and the √<area> parameter model, a unified method for predicting the lower bound of fatigue limit of spheroidal graphite cast irons subjected to combined loading was proposed. The predicted and experimental results agreed well.
2001-09-25