Strain Calculation And Fatigue Life Research Of Pipeline Dents

Various defects in the pipeline affect its safety.As a geometric defect of the pipeline,the dent will cause immediate or delayed failure of the pipeline,resulting in loss of personnel property or even environmental damage.The focus of the research is on the dented pipelines,and the finite element simulation is carried out by ANSYS.The surface strain,rebound process and fatigue life of pipelines are studied.Using the ASME strain evaluation method,the contour detection data and the contour data obtained by finite element simulation are interpolated by cubic spline and B spline interpolation,the equivalent variation of the surface of the depressed pipeline is obtained.Find the best number of data points for circumferential and axial detection by data point encryption.It is considered that the number of data points affects the strain value,the axial step length can be set to 20 mm,and the number of circumferential points can be set to 64.A finite element model of pipes and indenters are established to simulate the process of the dent and rebound caused by the impact of foreign objects.The influencing factors of the rebound amount are analyzed,and the stress and strain distribution and changes of the pipeline during the rebound process are studied.The differences in rebound amount,stress and strain values caused by different shape indenters are compared.The results show that the type of indenter affects the rebound amount,stress and strain state of the dented pipelines.The common fatigue assessment methods for dented pipelines are summarized.The fatigue life value was calculated by combining the stress change results of finite element loading with the S-N curve obtained from the fatigue test of small specimens.By changing the wall thickness of the pipeline,it is found that the fatigue life of the pipeline will be affected by changing the average stress and the variation of stress.