عنوان مقاله [English]
In this article, indentation process of damaged drinking water pipelines, repaired by polyester resin, are experimentally investigated while they are under two different conditions of constant and variable inner pressures. For this purpose, a mechanical defect is machined in pipe wall, and then, damaged part of the tube is repaired by the polyester resin. Then, to inject water into the tube and create different pressures, shut down two-end tube is connected to a hydraulic circuit. Then, the specimen with a certain inner pressure is placed into the universal testing machine between a rigid platen and a cylindrical punch. By applying the lateral force on the specimen, indentation test is performed in quasi-static condition; and it continues up to considering the first leakage effect in the repaired zone. In one type of the tests, inner pressure is kept in a constant value during indentation progress; and in the other type, inner pressure increases, slowly, due to indenting the tube wall. In each test, initial pressure, sample deformation mode, ultimate displacement of the punch, ultimate force, and energy absorption are measured; and in the variable pressure tests, ultimate pressure is also recorded. The variable pressure experiments show that when initial pressure increases, ultimate displacement of the punch, ultimate force and energy absorption decreases.; while, in the constant pressure experiments, by increasing the constant inner pressure up to 14 bar, ultimate displacement, ultimate force and absorbed energy increases and then in lieu of higher inner pressure, the mentioned parameters follow a decreasing trend.