Strain Capacity of Line Pipe with Yield Point Elongation

摘要

Line pipe varies in mechanical properties before and after thermal aging during an anti-corrosion coating. The increase in the yield strength (YS) and the appearance of the yield point elongation (YPE) is reported to have a harmful affect on the strain capacity required for discontinuous permafrost. This paper deals with the strain capacity of high strength steel line pipe under the bending moment, and describes the effect of YPE on the compressive strain limit of the pipe. The strain capacity of the pipe was analyzed by the finite element analysis (FEA) using the measured and the modeled stress-strain (S-S) curves. As a result, the strain capacity was found to have degraded remarkably by YPE for higher diameter/thickness ratio (D/t), higher yield to tensile strength ratio (Y/T), and lower internal pressure. Moreover, the strain capacity with YPE is more sensitive to the initial geometric imperfection of the pipe. In conclusion, the combined agents with the material strength, the pipe geometry, and the working conditions were determined in order to evaluate the strain capacity of the pipe subjected to the thermal aging.