Changing the mechanical characteristics of cracking pipes during their long‑term operation

The article presents the results of a study on the strength characteristics (tensile strength) of cracking pipes after prolonged operation. It was found that the strength properties of the pipe material deteriorated, while plasticity characteristics showed a slight increase. The decrease in conditional yield strength reached 39.94 %, and the reduction in tensile strength was 40.05 %. It was established that specimens taken from the used pipe underwent 25 % more elongation before fracture compared to specimens made from a new pipe. Using thermomechanical coefficients, the expected values of true yield strength for both materials were calculated. The results showed that the true yield strength of the used pipe material differs significantly from tabulated values, suggesting that for strength assessment of such structures, the true σT should be determined experimentally. If theoretical approaches are used, the influence of operational time on changes in mechanical properties of the metal must be taken into account.