Abstract:

X52 pipeline steel is widely used in long-distance oil and gas pipeline engineering. This kind of material has its unique mechanical properties：high strength and good plasticity. The establishment of its constitutive relation，matrix presentation and failure criterion are the main content of this study. By comparing the static tensile experimental result and the Ramberg–Osgood constitutive model，we found that when ε ≤ εP0.2，the Ramberg–Osgood constitutive equation could accurately reflect the X52 pipeline steel tensile stress-strain relationship. When ε > εP0.2，however，the theoretical constitutive curve which is based on the experimental results of Ramberg–Osgood constitutive model has large error. Based on this，we have made a correction on the Osgood constitutive model and proposed X52 pipeline steel global 2–phase stress strain relation in the condition of unidirectional pull-up，and then established the matrix expression of the constitutive relation of X52 pipeline steel. According to X52 pipeline steel excellent characteristics，this paper studied the plastic material stress failure criteria and strain failure criteria，then provided the strain failure criterion of X52 pipeline steel.

Key words: X52 pipeline steel；constitutive relation；matrix equation；Ramberg&ndash, Osgood constitutive model；failure criterion