Danyliuk I. Damage assessment and deformation parameters of cyclic crack resistance of operated steel of gas pipeline.

Object - damage to the pipe steel. The aim is to establish the basic laws of investigation of damageability, deformation and fracture of steel 17G1S in the initial and degraded condition and the evaluation of load-bearing capacity of gas mains with crack-like defects using deformation approach. Methods - modern experimental methods of fracture mechanics. Novelty - The shape, size and microscopic mechanisms of formation of corrosion damage on the surface of the tube operated; Main principles of deformation and fracture of steel stretching 17G1S at baseline and after operational degradation; first estimated fracture 17G1S steel tube using the optical-digital image of the sample surface analysis and the use of artificial sensory markers, determining the intensity of shear strain and the use of measuring the crack tip opening angle (crack tip opening angle - CTOA); developed recommendations for the use of a number of expansion options for the analysis of cyclic crack propagation mechanisms of fatigue cracks in the pipe steel 17G1S at the micro, meso- and macrolevels; suggested engineering methods for evaluating the crack resistance of the pipe after the main gas pipeline operational developments that allow to take into account the effect of scattered structural and mechanical damage. The results are implemented in the branch UMG "Prikarpattyatransgaz", Ref. №353 / 16-02.