長年の暴露発錆後の構造用鋼材の表面性状と疲労強度

概要

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In order to investigate the fatigue behavior of corroded steel plates, fatigue tests and surface roughness analysis of the plates were carried out for two kinds of steel: mild steel JIS SS41 and weathering steel JIS SMA50 which were exposed for 7 years at a materialyard or for 25 years at seaside, respectively. The following results were obtained:(1) Fatigue cracking of the corroded steel plates occurred under the conditions of surface roughness with y/ymax≥0.56 and (n/L)max≤1.2.(2) The average angles at the fringe of corrosion pits were 151°30′00″ and 156°49′54″ for the weathering steel and mild steel, respectively.(3) The fatigue strengths calculated basing on the sectional area through corrosion pits nearly coincided with the fatigue test results.(4) In the case of weathering steel, the fatigue strength of the as-rusted surface for 2×106 stress cycles was higher than that of the rust removed surface. On the other hand, the fatigue strength of the rust removed mild steel for 2×106 stress cycles was nearly equal to that of the as-rusted mild steel. This fact may be caused by the adherent rust on weathering steel surface which has an effect of stress relief and cutting off the groundmetal from atmosphere.
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