The article presents the results of testing samples of welded joints of polyethylene pipes for crack resistance at various temperatures. It is shown that in the weld zone a decrease in the stress intensity factor is observed up to 27% compared with the base material.

Keywords: Polymer, polyethylene, pipe, stretching, crack resistance, low temperatures, brittle failure, crack, welding, welded joint, fusion zone

From the pilot section of the gas pipeline, after ten years of operation, specimen-witnesses were seized. The gas pipeline consists of reinforced polyethylene pipes with an average adhesive reinforcing layer. The results of mechanical tests of model samples are given in the article. Investigations of the deformation-strength properties of the witness specimens show a decrease in the temperature of the viscous-brittle transition to -15 ° C. These results indicate a deterioration in the adhesion between the outer layers of PE80 and the middle technological layer. Good adhesion led to the emergence and development of a fragile crack. Stability tests at constant pressure showed satisfactory results, not a single sample collapsed. According to the research data, the reinforced polyethylene pipe did not deteriorate its deformation-strength properties for ten years of operation of the gas pipeline under pressure.

Keywords: Reinforced polyethylene pipe, specimen-witnesses, adhesion, stretching, viscous-brittle transition, resistance at constant internal pressure

Implemented assessment of the mechanical behavior of reinforced synthetic fibers of polyethylene pipes, which are provided in the construction adhesive layer connecting the reinforcing plastic shells and pipes. Presents the results of quasistatic tests the tensile strength of model samples in the range of low climatic temperature and speed tests 25-100mm/min. The dependence of the temperature of ductile-brittle transition in the mechanism of destruction of model samples of speed tests, which at 100 mm/min up to 0°С. The mechanism of destruction of a model sample of the reinforced polyethylene pipe, consisting in cracking of the technological layer connected with layers of PE80 which ability to braking of a crack and defines transition from viscous destruction to fragile at fall of temperature of tests is interpreted. It appears that this result emphasizes the need to further clarify and harmonize the existing regulatory requirements on the use and operation of pipes and polyethylene pipelines in cold climate regions.

Keywords: reinforced polyethylene pipe, pipeline, temperature, adhesive layer, strength, crack, viscosity, brittleness, cold climate