Fatigue crack propagation behaviour of pressurised elbow pipes under cyclic bending

Fatigue crack propagation behaviours of Z2CND18.12N austenitic stainless steel pressurised elbow pipes were studied under cyclic bending. The results show that the evolutions of crack depth with the number of cycles at both intrados and crown present logarithmic growth, while the evolutions of crack length with the number of cycles present exponential growth. The aspect ratios of crack increment, Delta(2c)/Delta a versus the number of cycles at intrados and crown are linear. J-integrals of the corresponding crack size were solved by numerical method. The evolutions of crack depth growth rate, da/dN with J-integral range, Delta J at intrados and crown conform to the unified Paris law.