摘要
超临界态CO2的管道运输是目前国际上控制大气中CO2等温室气体过度排放的碳捕捉与封存计划中的重要一环。因此,在内压波动作用下,研究CO2管道内表面裂纹的疲劳扩展路径问题具有重要意义,这是应用"破前漏"断裂准则判断压力管道安全性的关键。该文借助线弹性断裂力学的基本理论,基于ABAQUS平台建立了包含单一半椭圆型轴向内壁裂纹的三维有限元管段模型。该模型应用虚拟裂纹闭合法,可实现在管端轴力及弯矩、内压等载荷作用下的裂纹前沿断裂力学参数的提取。基于该断裂力学有限元模型,该文以两种薄壁CO2管道(厚径比:t/R=1/10和t/R=1/27.3)为研究对象,主要研究了在其各自特定工作内压作用下,不同初始裂纹深径比(?0≤1)的半椭圆型轴向内壁裂纹由于内压波动引起的疲劳扩展问题。详细分析了初始裂纹深径比?0分别为1、2/3、1/2、1/4、1/6和1/8等六种内表面裂纹的疲劳扩展路径;绘出了各种裂纹体的阶段性扩展轮廓并比较了其各自的疲劳扩展寿命。同时,亦讨论了管道厚径比对裂纹扩展趋势的影响。数值分析结果表明,裂纹体的初始几何形状与裂纹的疲劳扩展路径密切相关。各类裂纹的疲劳扩展存在一条"渐近路径",该"渐近路径"与管道厚径比有关。
Piping transportation of supercritical carbon dioxide(CO2) is a key link connecting the global Carbon-Capture-and-Storage(CCS) plan aiming to reduce excessive emissions of greenhouse gases like Co2. Therefore, it is of utmost importance that a series of problems involving the growth paths of fatigue cracks in CO2 pipelines with crack-like surface defects are taken into account when the leak-before-break(LBB) fracture criteria is used to evaluate the safety of pressure piping. Based on the linear elastic fracture mechanics(LEFM) theory and the ABAQUS software platform, this paper builds a three-dimensional finite element model of a pipe segment containing an axial semi-elliptical inner surface crack, which can be used to obtain the fracture parameters of the surface crack under axial forces, bending moments, and/or internal pressures by adopting the virtual crack closure technique(VCCT). On the platform of this presented finite element model in fracture mechanics, focusing on two types of thin-walled CO2 pipelines(thickness-radius ratios: t/R=1/10 and 1/27.3) under their specific operation pressures, this paper mainly discusses fatigue propagation problems of an axial semi-elliptical in-wall surface crack with different initial aspect ratios(?0≤ 1) caused by pressure fluctuation. Specifically, the fatigue propagation paths of the six inner surface cracks are analyzed when their initial aspect ratios are chosen as 1, 2/3, 1/2, 1/4, 1/6 and 1/8, respectively. The fatigue propagation stages for these cracks are drawn and their fatigue crack growth lives are compared. Meanwhile, the effect of thickness-radius ratios on the crack growth trends is also discussed. The numerical results show that the fatigue growth paths of these cracks have a close relationship with their initial geometrical shapes. There also exists an asymptotic route for fatigue propagation of these cracks, which is closely connected with the thickness-radius ratio of pipeline.
出处
《工程力学》
EI
CSCD
北大核心
2015年第5期84-93,共10页
Engineering Mechanics
基金
国家自然科学基金项目(51008049)
关键词
超临界态CO2管道
内压波动
半椭圆轴向裂纹
虚拟裂纹闭合法
疲劳扩展路径
supercritical CO2 pipeline
internal pressure fluctuation
semi-elliptical axial crack
virtual crack closure method
fatigue crack growth path
