Finite Element Modeling of the Failure Behavior of Pipelines Containing Interacting Corrosion Defects

Abstract

This paper describes the application of solid finite element models in the analysis of five tubular specimens containing interacting corrosion defects. Each of these specimens has been submitted to hydrotest up to failure as part of a previous research project. The specimens were cut from longitudinal welded tubes made of API 5L X80 steel with a nominal outside diameter of 457.2 mm (18 in) and a nominal wall thickness of 7.93 mm (0.312 in). The analyses accounted for large strains and displacements, stress-stiffening and material nonlinearity. The failure pressures predicted by the solid finite element models are compared with the failure pressures of these specimens measured in the laboratory burst tests carried out previously. Also the failure behavior of each specimen is described and illustrated by contour plots of stresses.

Failure pressure prediction of corroded pipes under combined internal pressure and axial compressive force

“…As expected, the highest stresses are concentrated in the regions of defects, where the thickness of the pipes is smaller, which is also in accordance with burst tests provided by Benjamin et al [23,24]. Using the results presented by Motta et al [3], experimental rupture pressures of Benjamin et al [23,24], numerical results of Andrade et al [25] for the IDTS 5 and results of analytical methods, Tables 5 and 6 are obtained.…”

“…In the methodology of Motta et al [3], failure pressures are predicted using PIPEFLAW program for five cases of pipelines with multiple idealized corrosion defects and compared to experimental results of Benjamin et al [23,24] and to numerical results obtained from manual modeling, i.e., creating the geometry and applying boundary and loading conditions manually, as well as FE simulation of Andrade et al [25], along with analytical methods results, among which: ASME B31G [26], DNV RP-F101 [27], RSTRENG Effective Area [28] and Mixed Type of Interaction-MTI [29].…”

“…Plastic deformation limit value, also pre-defined, was 0.0025. Figure 2 shows the true stress-strain curve for API 5L X80 steel obtained from Ramberg-Osgood equation, with parameters experimentally determined by Andrade et al [25].…”

“…For this first study, two models presented in Motta et al [3] were used. Models IDTS 5 and IDTS 9, with defects on the outer surface of the pipes, were previously manufactured and tested by Benjamin et al [23,24], as well as IDTS 5 was computationally modeled by Andrade et al [25]. Corrosion defects IDTS 5 and IDTS 9 are presented in Fig.…”

The development of a computational tool for generation of high quality FE models of pipelines with corrosion defects

“…To validate the automatic procedure for modeling and performing the FE simulation, the failure pressure (FP) obtained with the automatically generated models will be compared with experimental results obtained by burst tests [11] and numerical results obtained by manually generated computational models [5]. Those results are also compared with those obtained using semi-empirical assessment methods.…”