Defect Behavior Analysis Of Natural Gas Pipeline Based On Fracture Theory

In this paper,the defect behavior of the steel X80 natural gas pipeline for the second-line gas transmission of the West-East Gas Pipeline is discussed and analyzed from the causes of the defects and the types of defects.The crac K defects and related crac K-stopping theories in the defects are discussed and analyzed.Based on elastoplastic fracture mechanics and linear elastic fracture mechanics and damage mechanics in fracture mechanics,by controlling the internal pressure load of the pipe and the change in the initial length of the crac K,further analysis of the influence of J integral and stress intensity factor K on axial crac K and circumferential crac K on defect behavior.The finite element software ANSYS Wor Kbench platform establishes a finite element model with initial semi-elliptical crac K defects.The following conclusions are drawn from the simulated cloud map:1.The J-integral of the axial crac K is much larger than the circumferential crac K in the same environment;2.When the initial crac K length is constant,the J-integral of the axial crac K and the circumferential crac K also increase linearly when the internal pressure load of the pipeline increases stepwise;3.When the internal pressure of the pipe is constant,when the initial length of the crac K increases,the J integral of the axial crac K increases linearly,and the J integral of the circumferential crac K increases first and then tends to be gentle;4.The stress intensity factor K of the axial crac K is much larger than the circumferential crac K in the same environment;5.In the same situation,the K1 of the axial crac K is much larger than K2 and K3;6.Under the initial crac K length and the change of the internal pressure load of the pipeline,the change of K is almost the same as the J integral.