Change of Acoustic and Magnetic Properties of Metals of Main Pipelines under the Influence of Cyclic Loads

Today, the assessment of the technical condition of objects taking into account the effects of variable loads is gaining popularity in the world. As a rule, such loads do not lead to simultaneous destruction of structures. Such facilities include trunk pipelines. The variable loads arising in them are determined by the technological mode of operation. For main pipelines, a low-cycle load is characteristic, for gas pipelines, a multi-cycle load. During cyclic impact on the metal, its slight damage occurs at the micro level, which is almost impossible to detect without special diagnostic methods. Microdamage in the metal accumulates in the form of microcracks and, with an increase in the number of loading cycles, the number of microcracks increases several times, which can ultimately cause macrocracks and lead to design failure. When analyzing accidents that occurred on pipelines, the fact that failure occurred without the presence of characteristic crack-like defects in the pipe wall is often noted. Thus, fatigue damage to the metal is a dangerous factor that can lead to the destruction of pipelines. Given the new trends in diagnostics, one of the key issues is the assessment of damage to prevent accidents on main pipelines. The article considers the study of the dependence of the acoustic and magnetic properties of specimens from 09G2S steel loaded in the equivalent mode of the main gas pipeline, depending on the level of accumulated damage.