Study On Crack Propagation Properties Of Oil&Gas Pipeline

With the accelerated development of modern society, energy has become the standard measure of a country’s comprehensive national power base, the basic condition for the country’s economic development, and a powerful guarantee for social stable operation. In the energy structure in developed countries, the proportion of oil and gas has reached60%, which shows its ineffable importance. Due to the nature of oil, natural gas are flammable, pipeline transportation is the most secure, most economical and practical method of transport. However, during the operation of oil, gas pipelines will inevitably be improper initial installation; weld defects affect erosion, geological changes in ambient temperature changes, the oil, gas harmful media and human factors, resulting in a variety of corrosion, damage or even break. How to evaluate a variety of injuries and defects of the pipeline strength, durability, safety effects and find a scientific and feasible defect fixes, for the protection of the safe operation of oil and gas pipelines, to avoid economic losses and damage to the ecological environment, it has a very important practical significance.This paper describes the results of research and development of domestic and foreign research status of oil and gas pipeline safety evaluation methods, and highlights the existing life prediction method is low maneuverability, accuracy is not high and the limitations of other characteristics, which leads to rupture proposed mechanics evaluation. Secondly, by using the finite element method can determine the stress intensity factor crack through the establishment of a mixed finite element model. Then a similar hybrid tilt crack specimens in the laboratory and actual production of oil and gas pipelines that exist, by measuring along Ⅰ and type Ⅱ crack propagation direction different discontinuous displacement, affecting factors and stress crack intensity factors were evaluated. At the same time, the same finite element models are produced with the experimental specimen size and shape, the stress intensity factors of cracks that without either compressive residual stress or surface interaction were computed, and then the experimental results and finite element analytic calculation results were compared. The influence of hybrid tilt cracks deformation caused by the crack surface compressive residual stresses and the surfaces of cracks, and tortuous fatigue crack propagation expansion characteristics under the external force can be drawn. At last, the conclusions are incorporated into the actual pipeline, and verify the practical significance of this study, provide theoretical support to reasonably determine the replacement or repair of defective pipes.