Simulation Research On Pipelines Crack Propagation Under Low Strength Seismic Waves And Different Low Temperatures

The fatigue crack propagation on pipelines is an important content in the study of fatigue fracture under low strength of seismic wave,and different environmental temperature make different effects on properties of pipeline.Through summarizing the results of domestic and foreign research on the crack propagation,this article analyzed and summarized the three types of pipeline cracks;And on the basis of the fatigue crack propagation rule curve which is built in the theory of Paris,comprehensively reviewed of the theory of fracture mechanics on the fatigue crack propagation on pipelines and the criterions of the fatigue crack propagation which were used commonly in engineering;briefly introduced the characteristics of applications on the existing software in the simulation of crack,And combined with the study on the expression of the propagation rate on the fatigue crack, Integratly analysised the impact of the three basic elements on fatigue crack propagation on pipeline(elastic modulus,fracture toughness and crack threshold value),and analysised the general rules of the effects on the three basic elements,which including temperature and external load andinternal microstructure of material;Finally,after established the theoretical basis comprehensively,selecting the pipeline steel named X80 that serviced in the West-East natural gas transmission project as the simulation object,established the model of X80 pipeline steel on Ansys Workbench module,after studying the stress and strain of the three-dimensional model of pipeline without the initial crack, precutting a semielliptical surface crack in the center of the pipeline,setting the same condition of alternating load but deferent temperature fields,simulating the 3D model of pipeline with initial crack,through further comparative analysise on the stress intensity factor of type I, type II,type III and J-integral from the post-processing on Ansys,learned the changing rule on the control parameter of pipeling with semielliptical surface crack which were under the conditions of low strength and different temperature environment.Then providing a theoretical reference for prediction of fatigue life and the innovative design of pipeline.