PSI - Issue 71

V. Thondamon et al. / Procedia Structural Integrity 71 (2025) 226–232

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analysis for two sizes of indenters, viz., 89 mm and 142 mm diameter. For dent formation, indentation forces of 90 kN and 105 kN were applied. The dent depths were compared from experimental and numerical studies. Commissioning condition and in-service condition were considered for re-rounding studies. In the commissioning condition, there was no internal pressure during indentation whereas in the in-service condition, internal pressure of 9 MPa was applied prior to indentation. The dent depths at various stages were measured and compared. Below are the observations from the study. ● For the same indentation force, dent depth is higher for smaller indenter. ● For the same dent depth, higher dent diameter exhibits higher percentage re-rounding. ● For the same indenter diameter, higher dent depth shows lower percentage re-rounding. ● For the same dent depth and indenter diameter, higher percentage re-rounding is observed without internal pressure. ● In longitudinal direction the strain value keeps decreasing with distance from the indenter, but in circumferential direction, strain values are maximum at around 80 mm distance from the indenter. Further parametric studies are planned to study the variation of dent depths with respect to various mechanical parameters.

6. Acknowledgement This paper has been assigned the registration number CSIR-SERC-1141/2024. This research is funded by generous grant from CSIR, New Delhi.

7. References Naghipour M, Ezzati M, Elyasi M. 2018. Analysis of high-strength pressurized pipes (API-5L-X80) with local gouge and dent defect. Applied Ocean Research. 1;78:33-49. Rezaee N, Sharifi SM, Rashed GR, Niknejad A. 2018. Denting the oil pipelines by a rigid cylindrical indenter with conical nose by the numerical and experimental analyses. Thin-Walled Structures.124:312-22. Sha S, Jia G, Yan B, Chen P, Pang S, Feng Q. Full Scale Dent Rebound Testing of X65 Steel Linepipe. InIOP Conference Series: Materials Science and Engineering 2021 (Vol. 1043, No. 3, p. 032028). IOP Publishing. Wu Y, Zhang Y, Li L. 2021. Analysis of ductile damage changes of pipelines with unconstrained dents in rebound process. Engineering Failure Analysis.120:105071. Yu C, Qiu B, Hu J, Zhang J. 2019. Mechanical behavior and evaluation of dented pipe caused by cylindrical indenter. Journal of Failure Analysis and Prevention.19(2):519-35. Zhang P, Huang Y, Wu Y, Mohamed HS.2020. Investigations on the re-rounding performance of dented-pipelines at the service and shutdown stages. Engineering Failure Analysis. 116:104746. Zhao P, Shuai J, Lv Z, Xu K. 2020. Strain response of API 5L X80 pipeline subjected to indentation. Applied Ocean Research. 94:101991.