各種高張力鋼とステンレス鋼の 3%NaCl 水溶液中, 低ΔK 領域における疲労き裂伝ぱ特性

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Low-rate fatigue crack propagation properties in sodium chloride solution were investigated for carbon steel S45C, high-strength steels SM 50B and HT 80 and stainless steels SUS 403 and SUS 304. Tests were conducted under the condition of decreasing ΔK where maximum load was kept constant and minimum load was increased with the increase of crack length. This constant P_<max> test was confirmed to be a method free from crack closure, although the load ratio increased from 0.5 to 0.97. Low-rate fatigue crack propagation properties, obtained under closure-free condition, are summarized as follows. 1) In air, fatigue crack propagation properties including the threshold, ΔK_<th, air>, were independent of the kind of materials. The ΔK_<th, air> values for the five steels were around 2.8 MPa・m^<1/2>. 2) In 3% sodium chloride solution under freely corroding condition at a frequency of 30 Hz, fatigue crack propagation rates were also independent of the kind of materials and coincided with those in air when ΔK>ΔK_<th, air>. When ΔK<ΔK_<th, air>, the crack propagated at such low region of ΔK<1 MPa・m^<1/2> that the threshold, ΔK_<th, corr>, did not exist in practical sense for carbon and high-strength steels. ΔK_<th, corr>, which was 70% of ΔK_<th, air>, existed for stainless steels under the experimental conditions. 3) Fatigue crack propagation properties including the threshold values for all the steels coupled with zinc anode in sodium chloride solution were coincident with those in air. 4) Decreasing in frequency from 30 to 0.03 Hz resulted in a sixfold acceleration of crack propagation rate regardless of materials and ΔK levels under freely corroding condition.
社団法人日本鉄鋼協会の論文
1987-04-01

各種高張力鋼とステンレス鋼の 3%NaCl 水溶液中, 低ΔK 領域における疲労き裂伝ぱ特性

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