Analysis Of Ultimate Bearing Capacity Of Pipelines Containing Depressions

Dent is due to permanent plastic deformation of pipeline wall and the total deformation that occurs in the pipeline cross-section. As the main geometric defect in pipeline maintenance, dent has been paid more attention by pipeline managers. Engineering practical experience shows that pipeline failure is often controlled by limit load, and the plastic limit pressure is an essential parameter to the safety assessment of dent pressure pipeline. So, it has important academic significance and application value to analysis the limit pressure of dent pipeline.This paper of finite element analysis method to the plastic limit internal pressure of pipeline with dent and its influencing factors analysis of the system. Research and conclusion are as follows:(1)The analysis of dent re-rounding. The dent re-rounding is defined as two types:re-rounding after unload of external load and internal pressure. FEM model was set up to describe stress and strain changing when re-rounding. Due to the deviaition of empirical coefficients, according to influence analysis of pipeline dimension, pipe steel, external load depth, indenter and dent dimension, re-rounding factors calculation formula of the two types were fitted, which were the base of dent assessment methods.(2) The analysis on ultimate capacity of plant dent.Analytical solutions for burst pressure of pipeline was carried out on the basis of classic criteria to draw their limitiaions. In order to determine the failure criterion of pipelines under internal pressure, finite element simulation were conducted. Numerical simulation method was used to analysis the ultimate bearing capacity of dent pipeline by using AB AQUS finite element analysis software. And the stress and deformation in the process of dent deformation was described.In addition, Parameter sensitivity analyses were conducted to analyze the effect of external load depth, indenter radius, internal pressure, radius-thickness and pipe steel on the ultimate load capacity, and calculation formula were fitted considering main influence factors.(3) The analysis on ultimate capacity of plant dent containing corrosion. By using numerical simulation method, the FEM model of plant dent containing corrosion was set up and the ultimate capacity of the pipe was calculated. The influence of the ultimate pressure by corrosion depth, corrosion length, corrosion width, dent depth, indenter radius and initial pressure have been got. In addition, an empirical formula adapted for engineering is fitted by the FEM results.