Кинетика возникновения и развития трещин в конструкционных элементах газотранспортной системы

Abstract

The kinetics of the appearance and development of structural elements corrosion fatigue damages of Gas transmission system (GTS) operating under the complex influence of external factors with their various numbers and combinations, is considered. Taking into account the location of the GTS in an open area and the cyclical nature of the action of external factors, the dominant type of overall loading of pipelines is one-sided variable bending, which causes corrosion and fatigue damage along the perimeter of the transverse annular section of pipes. Herewith, a significant service life and round-the-clock operation of pipelines, in addition to ensuring their fatigue strength, also requires calculations for the crack resistance of pipes. The calculated schemes of crack resistance are studied and the equation of the K_ƒc stress intensity coefficient is chosen. It is demonstrated that this function gives reliable results with static and low-cycle loading of pipelines, but during multi-cycle loading, taking into account the kinetics of fatigue crack development, which leads to a change in the parameters, as well shapes and location of the break area, the application of this equation becomes conditional, requiring its correction taking into account variations in σ_pmax maximum stresses, а_ƒc the depth of crack propagation, as well as geometric parameters. and forms of fatigue break. A new function has been obtained that makes it possible to clarify the K_ƒc values and determine the N_э equivalent durability of the structure, taking into account the presence of a а_ƒc fatigue crack and give quantitative assessment the process of fatigue failure of the elements of the GTS structure.