腐食生成物のくさび効果に及ぼす繰返し速度と応力比の影響

抄録

The corrosion fatigue crack growth rate of a high tensile strength steel HT55 has been measured in 1% NaCl solution at various stress cycle frequencies and stress ratios to elucidate the corrosion product-induced wedge effect and dominating mechanical parameters for crack growth. The wedge effect is most effective at R=0.1, whereas it is less effective in the order of R=-1 and R=0.5. At R=-3, however, the wedge effect disappears, and the growth rate in 1% NaCl solution is higher than that in air. At f=50Hz and R=0.1 and 0.5 in 1% NaCl solution, the load strain hysteresis loop traces different paths during loading and unloading periods, resulting from viscosity of the corrosive solution remaining within cracks, but the load sharing capacity of the viscosity is negligibly small. Regions I and II in the hysteresis loop must be taken into consideration to explain uniquely the corrosion fatigue crack growth characteristics under various conditions, and a contributory stress intensity factor range ΔK_cont is proposed as a difference between ΔK and ΔK_ret, deduced from the load range shared by regions I and II.