Evaluation of the Effect of Internal Pressure and Flaw Size on the Tensile Strain Capacity of X42 Vintage Pipeline Using Damage Plasticity Model in Extended Finite Element Method (XFEM)

Abstract

Pipelines subjected to displacement-controlled loading such as ground movement may experience significant longitudinal strain. This can potentially impact pipeline structural capacity and their leak-tight integrity. Reliable calibration of the tensile strain capacity (TSC) of pipelines plays a critical role in strain-based design (SBD) methods. Recent studies were focused mostly on high toughness modern pipelines, while limited research was performed on lower-grade vintage pipelines. However, a significant percentage of energy resources in North America is still being transported in vintage pipelines. Eight full-scale pressurized four-point bending tests were previously conducted on X42, NPS 22 vintage pipes with 12.7 mm wall thickness to investigate the effect of internal pressure and flaw size on TSC. The pipes were subjected to 80% and 30% specified minimum yield strength (SMYS) internal pressures with different girth weld flaw sizes machined at the girth weld center line. This paper evaluates the TSC of X42 vintage pipeline by utilizing ductile fracture mechanics models using damage plasticity models in ABAQUS extended finite element method (XFEM). The damage parameters required for simulating crack initiation and propagation in X42 vintage pipeline are calibrated numerically by comparing the numerical models with the full-scale test results. With the appropriate damage parameters, the numerical model can reasonably reproduce the full-scale experimental test results and can be used to carry out parametric analysis to characterize the effect of internal pressure and flaw size on TSC of X42 vintage pipes.

Prediction of Tensile Strain Capacity for X52 Steel Pipeline Materials Using the Extended Finite Element Method

“…The final damage parameters (Maxpe = 0.085 mm/mm and G c = 900 N/mm) are proposed as fracture properties of the X52 vintage pipe. The second set of damage parameters (Maxpe = 0.013 mm/mm and G c = 450 N/mm) was previously obtained by Agbo et al [12] in the simulation of the ductile X42 grade of pipeline and applied in the current analysis for comparison.…”

“…Maxpe is chosen as the damage criterion. In contrast to Maxps, which was used previously by Lin et al [13] to predict the fracture response of this grade of vintage pipeline, Maxpe critical values are relatable to the physical critical strain values expected in the vicinity of the crack tip [12]. The crack initiation and propagation are numerically predicted through simulating eight published full-scale tests of X52 vintage pipes that are subjected to the combination of internal pressure and external eccentric tension which were reported by Abdulhameed et al [21].…”

“…Similarly, TSC predictive models developed by ExxonMobil (EM) and Pipeline Research Council International (PRCI) are only applicable to modern high-grade pipelines [8][9][10][11]. However, a high percentage of vintage pipelines are still in service to transport energy resources, thus it is necessary to develop numerical models that can predict the response of such pipelines under complex loading conditions [12].…”

“…CZM in conjunction with the extended finite element method (XFEM) is widely used in simulating the fracture process [15]. XFEM is an extension to the traditional finite element analysis in which the initiation and propagation of cracks that follow arbitrary paths can be simulated without the need for remeshing [12]. Crack or damage initiation in XFEM occurs when a stress-or strain-based criterion is met, while damage evolution follows the CZM model with fracture energy release (G c ) as the input parameter.…”

“…The effects of loading conditions, as well as the geometry of the crack and pipe on the TSC, were also investigated in this research. Agbo et al [12] calculated the strain-based XFEM damage parameters, Maxpe = 0.013 and G c = 450 N/mm, and TSC for an X42 vintage pipeline through calibrating numerical results with full-scale test results.…”