Calculation method for dent strain in oil and gas pipeline

Since the depth criterion cannot meet the demands of oil and gas industry for detecting dent defects in pipeline, a dent evaluation system based on strain was proposed in this paper. In classical shell theory, bending strain can be calculated by the values of dent depth, but the membrane strain can not be calculated by the geometric relationship between displacement and strain. In order to obtain the desired membrane strain values, arc-length method, polynomial, energy method and calculation method of membrane strain according to the bending strain were used respectively to simulate and calculate the actual membrane strain values, and compared with results from finite element calculation. It was found from the analysis and comparison that the calculated membrane strain according to bending strain was closer to actual membrane strain values, which is instructive for the use of strain criterion in evaluating integrity of dented pipeline.