Özet:

The urgency of the problems connected with periodical diagnostics and repair of the linear section of main pipelines and the expediency of the use of repair technologies for restoration of the required wall thickness are proved. The experimental part of the work was the welding of a corrosion defect on the outer surface of the pipe by successive surfacing of the “filament” rollers in the environment of CO2 (MAG) – metal active gas and manual arc (MMA) – manual metal arc method in three layers, with a contour seam. The results of the residual stress-strain state obtained experimentally by brewing the defect of corrosive origin are presented, as well as the modeling of the stress-strain state (NDS) by the finite element method (ITU), which is formed at the same time on the section of a tube of 17G1C steel with a diameter of 1420 × 16 mm. As a defect model, a hollow oval shape with dimensions of 100 × 60 mm and a depth of 6 mm in the central part was made. The analysis and comparison of stress distribution, plastic deformations and displacements for these methods were made. The main factors influencing the VAT are established. It is shown that the VAT for different welding methods has the same distribution pattern, but differs in size. An assumption is made about the interconnection of displacements of the sample in the formation of residual stresses in the free state and, in the presence of rigid ligaments. The appropriateness of using the MAG method of repairing the thinned section of the main pipeline in terms of the formation of residual VAT rates has been confirmed. The effect is related to the formation of an area with increased values of residual tensile stress after the overlap of the last seam of each layer due to the effect of transverse and longitudinal shrinkage of the metal through the interaction of the last roller in the layer with the side wall of the defect.

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