Internal Pressure Test on HDPE Pipe Ring

The purpose of experiment was the highlight of the creep of ring from polyethylene pipe subjected to internal pressure. To create the internal pressure in the HDPE pipe ring, a weight of 4.5 kg was superimposed on it, in the form of a cylindrical plate. In order to evaluate the strains of the elastic element subjected to the tensile stress, respectively compression, tensometric marks 1 and 2 are placed on the outside, in the case of the circular section. The internal pressure test was performed to evaluate the strains of the material of a PE 100 polyethylene ring in two directions: one axial (longitudinal) and the other transverse (circumferential) in order to highlight the creep of the pipe material due to its structure. In a polyethylene pipe stressed at internal pressure, due to the symmetry the tangential stresses are zero. The axial strain initially showed a positive increase, followed by a decrease, reaching negative values towards the end of the experiment, while the circumferential strain recorded positive values, about 300 times higher than the initial ones. The principal stress changed approximately linearly. The circumferential stress recorded the maximum value of σ1=0.33 MPa (3.3 bar) after two and a half hours of experiment. Based on such this test could be calculate Poisson s ratio ν.