Application of a discrete model of fatigue defect growth for assessment of tie safe operation life of the main pipeline section with a corrosion defect

摘要

The article proposes a model of fatigue defect growth obtained on the basis of the analysis of the three-dimensional stress state at the apex of the corrosion defect. To study the stress-strain state the actual operational loads of the pipeline were simulated by the finite element method. The scientific novelty of the study is that when developing a model of fatigue defect growth, it is assumed that the growth of the defect, which develops by the opening fracture mode, is controlled only by normal stresses. In one loading cycle, the intensity of the fracture process is determined by both the maximum tensile stresses during the loading period and the maximum compressive stresses during the unloading period. Based on the assumptions made, it has been established that the growth rate of fatigue defects of corrosion origin depends on the magnitude of the coefficient of the average stresses change ahead of the crack front during full loading cycle.