A Simple and Efficient Method for Obtaining the Whole-Range Uniaxial Tensile Properties of Pipeline Steel

Abstract

To obtain the whole-range true stress-true strain curves of API X65, a method is proposed based on the equal proportion principle and digital images. The tensile elongation was obtained by tracing the gauge points on the specimen surface, and the true strain and true stress of API X65 were calculated according to the formulae. The obtained true stress-true strain curves were validated by a 3-D finite element model. The true stress-true strain curve was set as the input data, while the engineering stress-engineering strain curve was set as the output data. The output data of the finite element model was the same as that of the experiment test. The findings imply that the proposed method could acquire reliable, whole-range true stress-true stain curves. These curves, which depict the material behavior of pipeline steel from initial elongation to fracture, could provide basic data for pipeline defect tolerance limit analysis and fracture assessment. by the method, while I2, M2, and O2 were tested by the traditional strain gauge method. Two kinds of results were used for comparison and analysis. Metals 2018, 8, 555 3 of 12 and O1 were tested by the method, while I2, M2, and O2 were tested by the traditional strain gauge method. Two kinds of results were used for comparison and analysis.