K_<max>の上昇による中高温条件下でのSUS304鋼の低ΔK域における疲労き裂伝ぱの下限界挙動の検討

概要

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Fatigue crack growth tests using center-cracked [M (T)] specimens and single-edge-cracked (SEC) specimens of SUS304 steel were conducted to examine the behavior of fatigue crack growth in the near-threshold regime at 623 K. Crack closure was eliminated by keeping K_<max> constant in ΔK decreasing test in order to obtain easily the threshold value expressed in terms of effective stress intensity factor range, ΔK_<ett>. By increasing the value of K_<max> and/or ΔK for a crack in a threshold condition, the fatigue crack growth behavior was investigated even in the region below the threshold value obtained by using the conventional ΔK-decreasing test. When the value of K_<max> was increased in the conventional threshold condition, crack growth was observed in the lower ΔK region. Crack growth was further observed repeatedly after successive increase in K_<max> in the newly established lower region below the conventional threshold value. In the region below a certain value of ΔK, however, crack no longer grew even after the change of K_<max>. Discussion was made on the characteristics of threshold.
社団法人日本機械学会の論文
1998-03-25