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Fatigue Crack Growth Rate of High Strength Pipe Steels

Fatigue crack growth rate is a significant mechanical property of high strength pipe. Some properties of fatigue crack propagation can be obtained by evaluating the mechanical performance of the material. In this study experiment studies were conducted with the fatigue crack growth rate test for two commonly used high strength pipe steels, X70 and X80 pipe steels, and the relationships between the length of the crack (a) and the number of the loading cycles (N) were derived. In addition, the crack tip opening displacement Δδ was calculated. Based on the experimental results, a regression equation was fitted for da/dN and Δδ. Results showed that the regression equation is similar to the Paris Formula, and X80 pipe steel has lower crack growth rate than the X70 pipe steel.