Anbang Li

Bio: Anbang Li is an academic researcher from Xi'an University of Architecture and Technology. The author has contributed to research in topics: Corrosion & Ultimate tensile strength. The author has an hindex of 7, co-authored 12 publications receiving 210 citations.

Effect of 3D random pitting defects on the collapse pressure of pipe — Part I: Experiment

Abstract: This paper is aimed at assessing the effects of local random external pitting defects on the collapse pressure of pipe under external pressure. In this two-part paper series, the buckling performance of locally random corroded pipe was experimentally and numerically studied. The experimental program described in Part I involves seamless carbon steel tubes with D/t = 17 and with different size of pitting defects. The random pitting defects were introduced into the outside surface of pipe using 6% FeCl3 solution and then the collapse pressure of such locally random corroded pipe was obtained experimentally. The profile of pipe was examined in details using Hexagon's new RA7320 Portable Arm Coordinate Measuring Machine (PACMM) and the measured data were analyzed meticulously. It indicated that either the out-of-roundness imperfection shape n = 2 or n = 3 fits best with the measure data. The characteristics of random pitting corrosion were statistically analyzed and the mass loss of pipe due to pitting corrosion was also determined after buckling test, the analysis results indicate that both lognormal and generalized extreme value (GEV) distribution are adequate to depict the distribution of pitting depth and pitting diameter-to-depth ratio (DDR). The corrosion morphology was observed using scanning electron microscope (SEM), which indicates that the shape of pitting defect is cylindrical or semi-ellipsoid. Finally, the relationship between collapse pressure and geometry defects was analyzed based on the experiment results.

Effect of 3D random pitting defects on the collapse pressure of pipe — Part II: Numerical analysis

Abstract: In the second part of this investigation, a 3D nonlinear (Finite Element) FE models was established to systematically study the collapse pressure of random corroded pipe. The models are developed within the framework of the nonlinear finite element ABAQUS in combination with a user defined Python program. Two constraints technique including surface-based tie constrain (SBTC) and shell-to-solid coupling (SSC) were implemented to take the complex geometry into account without the sacrifice of model accuracy while minimizing the computational cost. It was found that SBTC is more robust to simulate the locally random corroded pipe (external corrosion) than SSC. After validation models, a parametric investigation is performed to study the influence of wave number and amplitude of out-of-roundness, random pitting factors (pitting shape, pitting density and the length of pitting affect zone (LC)). It was revealed that the amplitude (wmax) and wave number (n) of out-of-roundness, pitting density and mass loss are the main factors that govern the collapse pressure (PCO) of 3D random corroded pipe whereas pitting shape has minor impact on PCO. Finally, a simplified pitting model was proposed, it was found that the circumferential and axial bending rigidity are key parameters that govern the PCO of pipe, which is mainly determined by the minimum remaining area in circumferential and axial direction.