高強度鋼の表面および内部起点型疲労特性に及ぼす応力比の影響(鉄鋼材料,<特集>ギガサイクル疲労)

概要

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In order to clarify effects of stress ratios (R=σ_<min>/σ_<max>) on surface- and interior-originating fatigue properties, uniaxial fatigue tests of high strength steel (SNCM 439) were carried out under three different stress ratios, R=0.3, 0.1 and -1. Based on tests results and fractofraphic analysis in initial crack propagation regions (Optically Dark Area (ODA) and Stage 2a), the following results were obtained; (1) Surface-originating fractures occurred in the same fatigue life region regardless of the stress ratio. On the other hand, interior-originating fractures occurred at a longer fatigue life region, as the stress ratio increased. It is unsure to apply the modified Goodman diagram to high strength steels of which main fracture mode was the interior-originating fracture. (2) In initial crack propagation regions, the fracture surface of the interior-originating fracture was strongly affected by the stress ratio, even though that of the surface-originating fracture was scarcely affected. The formation of a fine bumpy pattern which was characteristic of the ODA's fracture surface was affected by a multiplier effect of the inner environment of material and the compression load.
社団法人日本機械学会の論文
2004-08-25