受停输启用和供需变动的影响,油气管道的输送压力会发生周期性的变化,疲劳失效问题异常突出.特别是对于含有裂纹缺陷的管道,在疲劳载荷的作用下,若管道的应力强度因子幅超过疲劳裂纹扩展门槛值,裂纹就会发生疲劳扩展.当裂纹扩展到一定程度,超过管道运行压力下所能承受的临界缺陷极限尺寸,管道就会发生疲劳失效,从而影响到管道的使用寿命.采用高频疲劳试验机测试了X80钢级HFW焊管焊缝的疲劳裂纹扩展门槛值与疲劳裂纹扩展速率,结合API 579《适用性评价规范》中推荐的失效评估图技术(FAD)和Miner线性疲劳损伤积累理论,考虑了多种应力比对管道疲劳寿命的影响,建立了双参数HFW管道的疲劳寿命预测方法.%The transportation pressure of oil and gas pipeline can change periodically because of restart and supply change, so the fatigue failure problems stand out exceptionally. Especially for pipeline with crack defect, when the value of stress intensity factor exceeds fatigue crack expansion threshold value under fatigue load, the crack will expand; when crack expansion exceed critical defect extreme dimension under pipeline operation pressure, the fatigue failure of pipeline will happen, this will affect useful life of pipeline. In this article, the fatigue crack expansion threshold value of X80 HFW pipe welded seam and fatigue crack propagation rate were tested by using high-frequency fatigue testing machine, combined with the failure assessment diagram (FAD) recommended in API 579 Fitness-for-service Specification and the Miner's linear cumulative damage theory, considering the effect of combined stress ratio on pipeline fatigue life, the fatigue life forecast method for two-parameter HFW pipeline was established.
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