Effects of load ratio, R, and test temperature on fatigue crack growth of fully pearlitic eutectoid steel (fatigue crack growth of pearlitic steel)

The effects of changes in load ratio, R, and test temperature on the fatigue crack growth behaviour of fully pearlitic eutectoid steel have been investigated. Separate fatigue crack growth experiments were performed at load ratios of 0.1, 0.4, and 0.7 at −125 °C and compared to the behaviour at room temperature. An increase in load ratio at −125 °C decreased the fatigue threshold and significantly increased the Paris Law slope. Similar effects of changes in R, but less in magnitude, were observed in tests conducted at 25 °C. Fracture surfaces were examined using SEM. The significantly increased Paris Law slope exhibited in separate tests conducted at −125 °C and/or higher load ratio was coincident with an increase in the amount of cleavage fracture present on the fracture surface.