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, $\Delta \left(2c\right)/\Delta a$ 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, $\frac{da}{dN}$ with J-integral range, $\Delta J$ at intrados and crown conform to the unified Paris law.

研究了Z2CND18.12N奥氏体不锈钢加压弯管在循环弯曲下的疲劳裂纹扩展行为。结果表明，裂纹的深度随周期数的变化在内部和顶部都呈对数增长，而裂纹长度随周期数的变化呈指数增长。裂纹扩展的长宽比，$\Delta （2C）/\Delta \mathrm{一种}$与拱内和拱顶处的周期数成线性关系。用数值方法求解了相应裂纹尺寸的J积分。裂纹深度增长率的演变，$\frac{d\mathrm{一种}}{dñ}$ 具有J积分范围 $\Delta Ĵ$ intrados和Crown符合统一的巴黎法律。