散逸エネルギ評価によるSUS304鋼試験片の疲労限度予測法に及ぼす結晶粒径の影響

抄録

In recent years, fatigue limit estimation based on dissipated energy is getting an increasing attention in various industries because of its time and cost effectiveness. Heat treatment is applied to the material and machine components for the improvement of the mechanical properties. In this study, fatigue limit estimation based on dissipated energy measurement was applied to the evaluation of heat treated materials. Fatigue limit estimation by energy dissipation and conventional fatigue tests were conducted for as-received materials and re-solution heat treated materials of JIS type 304 steel to investigate the influence of grain size and the change of mechanical properties on energy dissipation. It was found from the fatigue limit estimation by energy dissipation that the fatigue limit of the re-solution heat treated materials could be precisely estimated, although estimated fatigue limit of the as-received materials obtained by energy dissipation was conservative values compared with that obtained by conventional fatigue tests. In conventional fatigue tests, volume fraction of martensite and its changing rate in the re-solution heat treated materials are less than those in the as-received materials. Therefore, the influence of the phase transformation to the re-solution heat treated materials was smaller than that to the as-received materials. The relationship between the dissipated energy and the plastic strain energy was also investigated. The dissipated energy in both materials could plot in the same straight line against plastic strain energy. The results in type 316L also plotted in the same line. It was found that materials with the same thermal property has same relationship between dissipated energy and plastic strain, even though mechanical properties of material are different from each other; thus the energy dissipation has a close relationship with plastic deformation.