伸線加工した共析鋼の疲労き裂進展特性

概要

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Fatigue crack propagation tests had been conducted on fully pearlitic eutectoid steels with different carbon contents drawn to various strain levels. In addition, the crack growth behavior in view point of their microstructures were observed. The crack propagation resistance decreased with an increase in drawing strain at low propagation rate region and increased at high propagation rate reglon. The decrease in the threshold stress intensity factor. ΔK_<th> with increase in the strain was attributed to the decrease in the roughness induced crack closure level due to a decrease in the pearlite colony size. It was also shown that the size dependence of ΔK_<th> in the present study is different from that in the eutectoid steel, the size of which was controlled by heat-treatments. On the other hand, the decrease in the exponent m in the Paris' power law was ascribed to the increase in 0.2% proof stress through both in the decrease of the pearlite lamellar spacing and the development of high-density dislocation structures.
社団法人日本機械学会の論文
1999-10-25