高強度鋼の下限界近傍の疲労き裂伝ぱ挙動に及ぼす酸化物誘起き裂閉口と粒界破壊の影響

概要

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Near threshold fatigue crack growth behavior of high strength steels has been investigated by varying the yield strength (921-1845 MPa) and stress ratio (R-0.06,0.4). Three kinds of Cr-Mo steels were used in this investigation and the fatigue tests were carried out at room temperature and in laboratory air. The threshold stress intensity factor range, ΔK_<th>, generally decreased with increasing yield strength and/or stress ratio. Then, the influence of stress ratio decreased as the yield strength became high. Several of the materials used, however, showed different tendencies. These observations were rationalized in terms of the concept of oxide-induced crack closure. Then, it was found that the intergranular fracture occurring at low fatigue crack growth rates remarkably encouraged oxide-induced crack closure in the case that the area percentage is more than 50%, and it played the important role to the behavior of ΔK_<th>.
社団法人日本材料学会の論文
1984-12-15