Experimental Investigation of Residual Ultimate Strength of Damaged Metallic Pipelines

Abstract

The ultimate strength of metallic pipelines will be inevitably affected when they have suffered from structural damage. The present experiments aim to investigate the residual ultimate bending strength of metallic pipes with structural damage based on large-scale pipe specimens. Artificial damage such as dent, metal loss, crack and combinations thereof is introduced on the pipe surface in advance. The entire test project consists of 34 seamless pipes with a relative low Diameter-to-thickness (D/t) ratio around 21.3, among which four intact specimens and thirty damaged specimens have been carried out for mutual comparison. Extensive measurements on structural damage and pipe geometries including wall thickness and outer diameter are performed. The material properties are measured by tensile tests with specimens from both pipe longitudinal and hoop direction. The four-point bending tests are performed to investigate the structural behaviors of metallic pipes. The bending strength associating with failure mode of each specimen is documented extensively, and the bending moment-curvature curves are presented and discussed. The fundamental research of experiments on damaged pipes in the present paper will be deployed for the following numerical and analytical research in the near future.

Residual ultimate strength of seamless metallic pipelines under a bending moment-a numerical investigation

“…In this section, the set-up of four-point bending tests and specimens are briefly reviewed. The details of the pipe test have been presented in the relevant experimental investigation part of Cai et al (2017b). Figure. 1 shows the designed four-point bending test set-up.…”

“…The specimens that will be deployed for the following validation are categorized into two groups (all the series numbers of specimens in this paper are exactly the same with the ones in the experimental investigation of Cai et al (2017b)): (a) specimens within the first group without artificial structural damage, including S1N1, S1N2, S1N3 and S1N4; (b) dented specimens within the second group with dent in different dent angle and size, including S2N1, S2N2, S2N3 and S2N5.…”

“…In previous work of Cai et al (2017b), an experimental investigation on the bending capacity of the damaged seamless metallic pipelines has been completed. Artificial damage such as a dent, metal loss, a crack and their combinations thereof is properly introduced on specimens.…”

Numerical investigation of residual ultimate strength of dented metallic pipes subjected to pure bending

“…However, the prediction for curvature is conservative, which is due to the ignorance of frictions of test configuration in the simplified boundary condition of numerical model used in this paper. Moreover, factors such as material properties, as discussed in the experimental investigation (Cai, Jiang, Lodewijks, & Pei, et al 2017), are also related to the discrepancies. Accounting for these reasons, it is safe to conclude that the developed simplified numerical model is capable of predicting the bending behaviour of pipes with a conservative prediction.…”

“…The effects of dent parameters such as dent length (l d ) and dent depth (d d ) have not been quantitatively clarified. Based on the previous experimental research from the authors Cai, Jiang, Lodewijks, and Pei, et al (2017), dented pipes with low D/t (around 21.3) have been studied. The aim of this paper is therefore to quantitatively investigate the residual ultimate strength of dented metallic pipes (D/t of 21.3) subjected to pure bending moment through nonlinear finite element method (FEM).…”