Фрактологический анализ тяжелонагруженных элементов конструкций газотранспортных систем

Abstract

The stress state change in the main gas pipelines in the zone of butt welds of pipe edges, which is the most stressed element of pipelines, is considered. The classification of loads, acting on the weld due to the main influencing factors, is given. It is specified that in thin-walled pipes, a plane stress state mainly acts and the tension acting normally to the circumferential weld is selected as the calculated one. The features of fatigue processes development in these structural elements are presented, depending on the stress level, and zones with different fracture gradients are marked. It is shown that a one-sided cyclic bending occurs in the walls of above ground pipelines with a non-stationary loading mode, which determines the nature and intensity of the process of occurrence and development of fatigue cracks, as well as the shape and geometric parameters of the fatigue ellipse form break. Taking into account the continuous growth of fatigue damage in the entire range of corrosion fatigue (durability cycles), a two-stage parameter adjustment is proposed to clarify the calculation procedures: determination of the maximum equivalent stress by using the Mises strength theory, and equivalent durability calculation based on the principle of linear summation of relative fatigue damage. As a result, the maximum equivalent values of voltage and cyclic durability are obtained in order to reliable estimate the service life of the pipeline.