Crack Propagation and Burst Pressure of Pipeline with Restrained and Unrestrained Concentric Dent-Crack Defects Using Extended Finite Element Method

Abstract

Mechanical damage in form of dents, cracks, gouges, and scratches are common in pipelines. Sometimes, these damages form in proximity of each other and act as one defect in the pipe wall. The combined defects have been found to be more injurious than individual defects. One of the combined defects in pipeline comprises of a crack in a dent, also known as dent-crack defect. This paper discusses the development of finite element models using extended finite element criterion (XFEM) in Abaqus to predict burst pressure of specimens of API X70 pipeline with restrained and unrestrained concentric dent-crack defects. The models are calibrated and validated using results of full-scale burst tests. The effects of crack length, crack depth, dent depth, and denting pressure on burst pressure are investigated. The results show that restrained dent-crack defects with shallow cracks (depth less than 50% wall thickness) inside dents do not affect pipeline operations at maximum allowable operating pressure if crack lengths are less than 200 mm. Releasing restrained dent-cracks when the pressure is at maximum allowable operating pressure can cause propagation of deep cracks (depth of 50% wall thickness or more) longer than 60 mm. However, only very long cracks (200 mm and higher) propagate to burst the pipe. Cracks of depth less than 20% of wall thickness inside dents formed at zero pressure are not propagated by the maximum allowable operating pressure. Dent-crack defects having dents of depth less than 2% outside diameter of pipe behave as plain cracks if the dents are formed at zero denting pressure but are more injurious than plain cracks if the dents are formed in pressurized pipes.

Experimental and Nonlinear Analysis of Cracking in Concrete Arch Dams Due to Seismic Uplift Pressure Variations

“…This is a consequence of the displacement vector function approximation which is appended to model the crack's existence. When the crack is modelled using XFEM, the classical displacement is predicated on the finite element approximation in conjunction with the partition of unity method (PUM) paradigm, as per Melenk and Babuška [10,36,37]. This permits easy incorporation of local Figure 11.…”

Experimental study and finite element analysis of notch effect on HDPE pipes’ resistance under internal pressure

“…In the other hand, it is very important to identify the areas of maximum stress concentration in order to know where the strain gages should be placed [7]. Thus, to predict the burst pressure and evaluate the stress and strain field along the pipe [8] or around the defect [9], ONO et al [10] studied the visualization of internal defect of a Pipe using mechanoluminescent sensor. They found that the hoop strain on the defective pipe had maximum and minimum values around the defect and the maximum hoop strain increased with deepening the defect.…”

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

“…They noticed, however, that the critical strain decreases when the beam specimen thickness increases, suggesting that a fixed criterion might not be suitable for all failure scenarios. Okodi et al [18] used Maxpe and G c in XFEM analysis to predict the burst pressure in X70 pipe specimens with dent-crack defects. They investigated the effects of the denting pressure as well as dent and crack sizes on the burst pressure and validated the predicted XFEM results with experiments [18].…”

“…Okodi et al [18] used Maxpe and G c in XFEM analysis to predict the burst pressure in X70 pipe specimens with dent-crack defects. They investigated the effects of the denting pressure as well as dent and crack sizes on the burst pressure and validated the predicted XFEM results with experiments [18]. Okodi et al [19] simulated the propagation of cracks in X60 grades of pipeline using the XFEM damage criterion, Maxpe, and G c and validated their results with small-scale and full-scale tests.…”