Fatigue crack propagation in steels with different yield strengths

Abstract

1. Fatigue crack propagation in low-alloy and low-carbon steels can be described by the relationship d2a/dN=C(ΔK)n. Two sections — lower and upper — are observed on the curves of crack growth, differing from each other in their slope to the ΔK axis. 2. The length of the fatigue crack corresponding to the change from one section to the other increases with increasing yield strength of the steels. 3. On the lower section, with a steeper slope to the ΔK axis, corresponding to the initial stage of crack growth, the average rate of crack propagation is considerably smaller than in the upper section. 4. In the upper section the relationship between exponent n and coefficient C and the yield strength and ultimate strength of the steels is almost linear. 5. The average rate of fatigue crack propagation in low-alloy and low-carbon steels decreases with increasing yield strength, as the result of which the life of the steel increases. The largest values of vav were obtained for steel 15kp and the smallest for steel 10G2S1.