DP鋼のコーキシング効果に及ぼす組織形態の影響

概要

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In order to investigate the influence of microstructure on the coaxing effect, rotating bending fatigue tests were carried out on plain specimens of two kinds of dual-phase steels, Steel A which has a microstructure containing isolated martensite phases in a ferrite phase and Steel B which has a continuous martensite phase filled with ferrite phase. In both steels, nonpropagating cracks were observed at their fatigue limits and the tips of the nonpropagating crack initiated in a ferrite phase or near the phase boundary were blocked from growing by martensite phases. Moreover, the origin of final fracture in coaxing process was the nonpropagating crack initiated at the first stress level. The coaxing effect was more marked in Steel B than in Steel A. The reason was discussed based on the difference in the crack growth path caused by the martensite morphology, that is, the cracks blocked by martensite structures changed the direction of growth and propagated through ferrite structures in Steel A and the cracks in Steel B penetrate the martensite structures.
社団法人日本機械学会の論文
1995-02-25