Study for Mechanism of Corrosion Fatigue Crack Propagation for HT80 Steel at Low ΔK Region by Variable Loading ΔK Decreasing Test Method

In order to predict the safe life of corrosion fatigue under randam loading conditions as are found in service, the fatigue crack propagation properties of high strength steel of HT 80 were studied both in air and in 3% NaCl aqueous solution by using the newly developed variable loading ΔK decreasing test method. The results showed that the acceleration of crack propagation was observed both in air and in 3% NaCl aqueous solution at low ΔK regions when the overload was applied to the compressive direction frequently. The effect of load frequency on the crack propagation rate in 3% NaCl aqueous solution became smaller as the frequency of variable loading increased. The effect of variable loading frequency on the crack propagation rate in 3% NaCl aqueous solution became smaller as the load frequency decreased. The mechanism of acceleration of crack propagation under veriable loading conditions was discussed based on Neumann's model.