水素供給下における高強度鋼の疲労き裂進展下限界特性について

概要

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Constant maximum stress intensity (K_<max>) fatigue tests were carried out to obtain the nearthreshold characteristics in fatigue crack growth of high strength steel. Specimens were loaded in in-plane bending at various K_<max> under hydrogen supply and in room air. Fractographic observations were made on the fracture surfaces at the near-threshold regions. The results obtained are as follows; (1) The threshold stress intensity factor range (ΔK_<th>) obtained under hydrogen supply was equivalent substantially to that in room air with an exception of the region of K_<max>\/K_<lscc> under hydrogen supply. (2) ΔK_<th> decreased linearly with an increase in stress ratio (R). In this regard, the effective value of the threshold stress intensity factor range (ΔK_<effth>) was constant, ΔK_<effth>≒3 MPa√<m>, in the region of R<0.7. On the other hand, in the region of R>0.7, ΔK_<th> decreased with increasing R. From these results, it is noted that the design based on ΔK_<th> Obtained at lower R is dangerous even m room arr. (3) On the fractographic observations at the near-threshold region, the striation-like pattern occupied the major portion of the fracture surfaces in the region of R<0.7. On the other hand, in R>0.7, the proportion of intergranular facet increased with R. (4) It is confirmed that the constant-K_<max> fatigue test is suitable for the determination of ΔK_<th>.
社団法人日本材料学会の論文
1986-02-15