Determination of the influence of an artificial defect on the mechanical properties of the material of a flexible pipeline during a rupture test

Abstract

The object of research is the phenomenon of influence of hidden defects on the mechanical properties of the material of flexible pipelines. T-type pressure fire hoses with an inner diameter of 77 mm were used as test samples of flexible pipelines. During the operation of pressurized fire hydrants and their laying on vertical surfaces, they are subjected to significant bursting pressures in their longitudinal direction. That is, such operating modes of the sleeve may occur during its operation. The research was carried out on the FP 100/1 bursting machine, in which the test samples were fixed. The dependence of the stiffness and normal elasticity of the material of the flexible pipeline on the depth and length of the artificial defect when testing it for breaking has been established. With an artificial defect depth of 0.2 mm and its length from 0 to 40 mm, the stiffness of the flexible pipeline material decreases from 573.812 kN/m to 478.276 kN/m. With the indicated values of the defect, the normal elasticity ranged from 86.46 MPa to 64.567 MPa. When the depth of the defect increases by 0.4 mm, the stiffness of the sleeve material decreases to 432.902 kN/m, and the normal elasticity decreases to 58.442 MPa. The obtained results are explained by the fact that when the thickness of the threads of the base of the power frame is reduced by 33 %, the longitudinal stiffness and normal elasticity of the material of the flexible pipeline are reduced by 25 % and 26 %, respectively. The results of these studies are needed in practice, because they can allow to develop new or improve existing methods of detecting hidden defects in the material from which flexible pipelines are made.