Mechanical Effects of Corrosion Products in Corrosion Fatigue Crack Growth of a Steel

Abstract

Corrosion fatigue crack growth test of a high-tension steel HT55 was conducted in 1% NaCl, and the wedge effect by corrosion products and crack extension by corrosive dissolution have been estimated in terms of ΔKeff. da/dN against ΔK in 1% NaCl decreases in the order of 0.01 Hz, 0.1 Hz, in air (having no frequency effect) and 5 Hz under R=0.1. da/dN in NaCl at 5 Hz is smaller than that in air on account of the wedge effect by corrosion products. There is no wedge effect under R=0.5. When the wedge effect is eliminated by re-plotting the results in terms of ΔKeff, da/dN under R=0.1 decreases in the order of 0.01 Hz, 0.1 Hz, 5 Hz and in air as is under R=0.5. Supposing the linear summation hypothesis in terms of ΔKeff, the crack extension by corrosive dissolution (da/dt)D is reduced.