Research Of Damage Constitutive Model For X100 High Strenth Pipeline Steel

The demand for oil and natural gas promotes the development of high-grade pipeline steel.Some foreign X100 test pipelines have been applied to pipeline facilities.With the construction and planning of the West-East Gas Pipeline Project,it's urgent to develop the research and application of X100.The rolling process,microstructure,welding performance and mechanical properties of X100 have been studied extensively at home and abroad,while its mechanism of plastic damage is rarely studied.Therefore,starting with the investigations on damage and failure mechanisms of X100,the Johnson-Cook damage model for X100 is established in this paper.Firstly,a series of uniaxial tension and compression tests,under different temperatures and strain rates,are carried out by Gleeble-3800 test machine,MTS universal material tester and Split Hopkinson Pressure Bar.The effects of plastic strain,stress triaxiality,strain rate and temperature on the mechanical properties and damage characteristics of X100 are analyzed based on these tests.Secondly,the Johnson-Cook damage model consists of two parts: the flow stress equation and the failure criterion,each of which containing five parameters to be estimated.Based on the test data,the valuations of modified Powell algorithm and Levenberg-Marquardt algorithm are used to the flow stress equation and the failure criterion respectively.Furthermore,the accuracy of the valuations are verified by 1stOpt software,a mathematical optimization analysis tool.Thirdly,as Johnson-Cook model imported into ABAQUS,the FEM for tests are carried out.The FEM results are close to the experimental results,and the errors are within the allowable range.The accuracy of the model is verified by FEM.The results of this study provide a theoretical basis for further study for plastic damage mechanism of X100 pipeline steel.