オーステンパ球状黒鉛鋳鉄の高サイクル疲労における破壊機構の遷移現象について

概要

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We carried out high-cycle internal pressure fatigue tests using a large number of thin-wall cylinders of austempered ductile iron (ADI). As a result, we observed a distinctive feature often seen in high-strength steel, that the SN diagram inclined again after about 10^7 cycles, in spite of once revealing a horizontal part at 10^6- 10^7 cycles, and that an obvious fatigue limit could not been observed. Corresponding to this characteristic SN diagram, Weibull plots of the fatigue data were dramatically changed between high-and low-pressure levels. The thorough SEM observation of the fracture surfaces clarified that the fracture origins changed from casting defects to relatively small graphite particles between high-and low-pressure levels. This means that different fracture mechanisms exist between high-and low-pressure levels. These two mechanisms competed in the high-cycle region and brought about the distinctive fatigue behavior of ADI.
社団法人日本機械学会の論文
1993-11-25