Determining the Dissipative Properties of a Flexible Pipeline’s Material at Stretching in the Transverse Direction Taking Its Structural Elements Into Consideration

This paper reports an experimental study that determines the dissipative properties of a pressure fire hose, the type of «T», whose inner diameter is 77 mm, under the static load conditions, taking into consideration the structural elements of the hose in the transverse direction. For this study, experimental samples were separated from the different sections of the hose. The study involved both the outer fabric reinforced frame and the internal waterproofing rubber layer of the pressure fire hose. A series of field experiments were carried out while stretching the samples under the conditions of static loading-unloading cycles. The tests included 7 cycles, which were carried out in a two-minute interval for the material of the hose. The study results showed that during the first two to three cycles, the materials manifest a short-term creep that stabilizes under modes 4‒7. The results from experimental research were approximated by polynomial trend lines. The deformation of samples demonstrated the curves that, under the conditions of cyclic loading and unloading, formed hysteresis loops. When analyzing the appropriate curves, it was found that, first, during the first two-three loading-unloading cycles the area of the hysteresis loops decreases, second, the inclination angle of hysteresis loops also decreased during each subsequent loading-unloading cycle. It was established that the dissipation coefficients of the hose material stretched in the transverse direction are significantly reduced under the first three test modes in the range from 0.49 to 0.37. At subsequent tests (cycles 4–7), dissipation coefficients stabilize at the level of 0.18 for the reinforced frame, and 0.316 for the rubber layer.