Application of the Extended Finite Element Method (XFEM) to Simulate Crack Propagation in Pressurized Steel Pipes

The extended finite element method (XFEM) has recently become a very effective method to investigate the propagation of cracks in various structures under complex loading conditions. However, its use in the pipeline industry has been limited. This paper aims to apply XFEM to model our previous experimental results on NPS 12 grade of X52 steel pipes in which circumferential cracks with different sizes were pre-machined near the middle length and then eccentric tension was applied to the pressurized pipe specimens. Our previous experiments showed that the propagation of a surface crack was affected by the original crack configuration, the internal pressure level, and the external loading applied. The crack depth showed greater influence than the crack length on the burst load and the tensile strain capacity of the pipe. In this paper, the fracture criterion for modelling crack propagation using XFEM was defined by two damage parameters, the maximum principle stress and the fracture energy. The values of the damage parameters were varied until excellent agreement was obtained between one of our previous experiments and its numerical model. Then, this set of damage parameters was used to model another one of the experiments for verification. This paper describes our methodology for validation of XFEM and the adequate values of the damage parameters required to model crack propagation in X52 pipes.

Download Full-text

NUMERICAL SIMULATION FOR CRACK PROPAGATION IN GEAR TEETH USING THE EXTENDED FINITE ELEMENT METHOD

10.26678/abcm.cobem2019.cob2019-0243 ◽

2019 ◽

Author(s):

Pedro Murilo Souza de Quadros ◽

Carlos Henrique Silva ◽

Ana Paula Carvalho da Silva Ferreira

Keyword(s):

Numerical Simulation ◽

Finite Element Method ◽

Finite Element ◽

Crack Propagation ◽

Extended Finite Element Method ◽

Extended Finite Element ◽

Gear Teeth ◽

Element Method

Download Full-text

Failure Pressure Prediction of Cracks in Corrosion Defects Using XFEM

Volume 1: Pipeline and Facilities Integrity ◽

10.1115/ipc2020-9312 ◽

2020 ◽

Author(s):

Xinfang Zhang ◽

Allan Okodi ◽

Leichuan Tan ◽

Juliana Leung ◽

Samer Adeeb

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Extended Finite Element Method ◽

Crack Depth ◽

Average Error ◽

Extended Finite Element ◽

Defect Depth ◽

Failure Pressure ◽

Corrosion Defects ◽

Element Method

Abstract Coating and cathodic protection degradation can result in the generation of several types of flaws in pipelines. With the increasing number of aging pipelines, such defects can constitute serious concerns for pipeline integrity. When flaws are detected in pipelines, it is extremely important to have an accurate assessment of the associated failure pressure, which would inform the appropriate remediation decision of repairing or replacing the defected pipelines in a timely manner. Cracks-in-corrosion (CIC) represent a class of defect, for which there are no agreed upon method of assessment, with no existing analytical or numerical models to predict their failure pressures. This paper aims to create a set of validated numerical finite element analysis models that are suitable for accurately predicting the failure pressure of 3D cracks-in-corrosion defects using the eXtended Finite Element Method (XFEM) technique. The XFEM for this study was performed using the commercially available software package, ABAQUS Version 6.19. Five burst tests of API 5L X60 specimens with different defect depths (varying from 52% to 66%) that are available in the literature were used to calibrate the XFEM damage parameters (the maximum principal strain and the fracture energy). These parameters were varied until a reasonable match between the numerical results and the experimental measurements was achieved. Symmetry was used to reduce the computation time. A longitudinally oriented CIC defect was placed at the exterior of the pipe. The profile of the corroded area was assumed to be semi-elliptical. The pressure was monotonically increased in the XFEM model until the crack or damage reached the inner surface of the pipe. The results showed that the extended finite element predictions were in good agreement with the experimental data, with an average error of 5.87%, which was less conservative than the reported finite element method predictions with an average error of 17.4%. Six more CIC models with the same pipe dimension but different crack depths were constructed, in order to investigate the relationship between crack depth and the failure pressure. It was found that the failure pressure decreased with increasing crack depth; when the crack depth exceeded 75% of the total defect depth, the CIC defect could be treated as crack-only defects, since the failure pressure for the CIC model approaches that for the crack-only model for ratios of the crack depth to the total defect depth of 0.75 and 1. The versatility of several existing analytical methods (RSTRENG, LPC and CorLAS) in predicting the failure pressure was also discussed. For the corrosion-only defects, the LPC method predicted the closest failure pressure to that obtained using XFEM (3.5% difference). CorLAS method provided accurate results for crack-only defects with 7% difference. The extended finite element method (XFEM) was found to be very effective in predicting the failure pressure. In addition, compared to the traditional Finite Element Method (FEM) which requires extremely fine meshes and is impractical in modelling a moving crack, the XFEM is computationally efficient while providing accurate predictions.

Download Full-text

Numerical Analysis of API 5L X42 and X52 Vintage Pipes with Cracks in Corrosion Defects Using Extended Finite Element Method

Journal of Pressure Vessel Technology ◽

10.1115/1.4050988 ◽

2021 ◽

Author(s):

Xinfang Zhang ◽

Meng Lin ◽

Allan Okodi ◽

Leichuan Tan ◽

Juliana Leung ◽

...

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Extended Finite Element Method ◽

Pipe Wall ◽

Crack Depth ◽

Initial Crack ◽

Extended Finite Element ◽

Failure Pressure ◽

Corrosion Defects ◽

Element Method

Abstract Cracks and corrosion in pipelines can occur simultaneously, representing a hybrid defect known as cracks in corrosion (CIC), which is often difficult to model using the available assessment codes or methods. As a result, detailed modeling of CIC has not been studied extensively. In this study, the extended finite element method (XFEM) has been applied to predict the failure pressures of CIC defects in API 5L Grade X42 and X52 pipes. The pipes were only subjected to internal pressure and the XFEM models were validated using full-scale burst tests available in the literature. Several CIC models with constant total defect depths (55%, and 60% of wall thickness) were constructed to investigate the effect of the initial crack depth on the failure pressure. The failure criterion was defined when wall penetration occurred due to crack growth, i.e., the instance the crack reached the innermost element of the pipe wall mesh. It was observed that for shorter cracks, the failure pressure decreased with the increase of the initial crack depth. The results indicated that the CIC defect could be treated as crack-only defects when the initial crack depth exceeded 50% of the total defect depth. However, for longer cracks, the initial crack depth was found to have a negligible effect on the failure pressure, implying that the CIC defect could be treated as either a crack or a corrosion utilizing the available assessment methods.

Download Full-text