含裂纹缺陷气瓶疲劳裂纹扩展及寿命预测

Fatigue crack growth and life prediction of steel cylinder with crack defects

对于循环载荷作用下含初始缺陷的承压类油气储运设备,准确预测其疲劳寿命并完整描述疲劳裂纹扩展过程一直是工程界和学术界的研究重点和难点。以含初始裂纹缺陷的34CrMo4材料气瓶为研究对象,运用扩展有限元技术分析循环内压作用下气瓶结构的疲劳力学响应,并研究多种参数(初始裂纹的尺寸大小、方向、位置)对疲劳寿命及裂纹扩展过程的影响。最后,将有限元的计算结果与ASME VIII-3中的评价结果进行对比,发现两者的评价结果相当。但是,由于扩展有限元技术能够更加准确、高效地模拟初始裂纹从开始扩展直至断裂的整个动态过程,因此扩展有限元技术在复杂结构的疲劳寿命预测和损伤容限设计时更具有优势。

In engineering and academic researches, it is always important and diffi cult to accurately predict the fatigue life and completely describe the fatigue crack growth process of pressure equipment for oil ＆ gas storage and transportation with initial defects under cyclic loading. Taking the 34CrMo4 steel cylinder with initial crack defects as an example, the extended fi nite element technology is used to analyze the mechanical fatigue response of the cylinder structure under the cyclic internal pressure. The impacts of various parameters（size, direction and location of initial cracks） on fatigue life and crack growth process are also investigated. Finally, the fi nite element calculation results are compared with the evaluation results of ASME VIII-3, revealing that they are very close. Nevertheless, since the extended fi nite element technology can more accurately and effi ciently simulate the whole dynamic growth process of initial cracks from the beginning of growth to fracture, it is more advantageous to predict the fatigue life and design the damage tolerance of complex structures.