基于断裂相场法的管道环向表面裂纹扩展研究

Fracture phase-field method-based circumferential surface crack propagation investigation of pipeline

[目的]旨在深入探讨轴向力作用下不同初始环向表面裂纹形态(椭圆形和扇形)对管道裂纹扩展行为的影响,为海洋工程结构物的结构完整性安全提供理论支持。[方法]采用断裂相场法模拟和分析裂纹扩展过程,通过连续的场函数以弥散的形式表征裂纹,依托Francfort-Marigo变分原理,将断裂能融入系统的总势能中,引入退化函数量化损伤导致的应变能折减,在有限元软件ABAQUS中进行二次开发,利用交替解法求解管道裂纹扩展问题。[结果]结果显示,环向椭圆形表面裂纹深度小于壁厚的1/2时,裂纹先沿环向扩展,再沿壁厚方向扩展直至穿透;当椭圆形裂纹贯穿程度较大时,裂纹先沿壁厚方向扩展至穿透,再沿环向扩展;扇形裂纹则倾向于先沿壁厚方向穿透,随后沿环向扩展。[结论]研究表明,断裂相场法能准确模拟裂纹在管道中的局部演化过程,应重视轴向力作用下的管道初始裂纹形态及裂纹贯穿程度对管道结构完整性的影响,这对提高管道结构的安全性及可靠性具有重要意义。

[Objective]This study aims to deeply investigate the influence of different initial circumferen-tial surface crack shapes(elliptical and sectoral)on pipeline crack propagation behavior under axial forces,thereby providing theoretical support for the structural integrity safety of offshore structures.[Methods]The crack propagation process is simulated and analyzed using the phase field method,and cracks are repres-ented in a diffused manner through a continuous field function.Relying on the Francfort-Marigo variational principle,fracture energy is integrated into the total potential energy of the system.A degradation function is introduced to quantify the reduction of strain energy caused by damage.Secondary development is conducted in finite element software ABAQUS,and the staggered solution strategy is used to solve the problem of pipe crack propagation.[Results]The results show that when the depth of an elliptical circumferential surface crack is less than half the wall thickness,the crack first propagates circumferentially,then extends through the wall thickness until penetration occurs.When the extent of the elliptical crack penetration is larger,the crack first extends through the wall thickness until penetration,then propagates circumferentially.Sectoral cracks tend to penetrate through the wall thickness first,followed by circumferential expansion.[Conclusions]The results of this study indicate that the fracture phase-field method can accurately simulate the local evolution process of cracks in pipes and highlights the impact of the initial crack shape and the extent of crack penetra-tion on the structural integrity of pipes under the action of axial forces.This has significant implications for en-hancing the safety and reliability of pipeline structures.