Keyword: «stress-strain state»

As a result of seasonal thawing and freezing of the surrounding soil, an underground pipeline, laid in the permafrost area, undergoes vertical displacement changes twice a year. Complex deformations occur in some sections, manifesting as multiple arches transitioning into one another without intervals. This article proposes a methodology for assessing the stresses that occur in the pipeline in such sec-tions. An equation describing the vertical position of the underground pipeline, depending on the weight of the soil above and the reactions of the soil below, has been obtained. There is no need to explicitly specify longitudinal forces in the equation, which greatly simplifies field work in data collection. The soil reactions are determined by using the gradient descent method in solving the equation.

Determination of impact strength during mechanical impact bending tests is the main practical method for assessing the susceptibility of steel to brittle fracture (GOST 9454-78). The article points out the disadvantages of this test method. Based on finite element modeling, the loading of specimens under impact bending with different types (shapes) of stress concentrator made of structural steel grade St3 was carried out. As a result of the research, a picture of the stress-strain state in the area of stress concentrators was obtained and the edge effect of stress-strain state was shown.

Based on the analysis of the stress-strain state of welded joints, it is shown that when welding saddle branches to existing gas pipelines at low temperatures using the proposed technology and standard welding, the differences in the values of stresses and displacements occurring are insignificant. Numerical calculations have shown that when welding a saddle branch at low temperatures using the proposed technology, it can be expected that the joint strength will not be lower than when welding under standard conditions.