Scientific Journal Problems of Emergency Situations - Nazarenko S., Chernobay G., Kolienov O., Borodych P., Kryvoshei B., Titarev V. Determination of viscouselastic properties of pressure fire hoses with a diameter of 150 mm. С. 152-166.

The presented experimental studies to determine the viscoelastic characteristics of a pressure head fire hose of the "T" type with an inner diameter of 150 mm under static load conditions. In the course of the work, a number of full-scale tensile experiments were carried out with a sample under conditions of static loading-unloading cycles. The tests consisted of 7 cycles (mode) of loading-unloading, which were carried out with a two-minute interval. Taking into account the experimental data, the tensile stiffness of the sleeve material in the longitudinal (along the base) direction was determined. It has been established that numerous results of mechanical properties depend on the "history" of the sleeve load, that is, in the first two load modes, the rigidity is given, increased, and only then, in the next ones, they stabilized. This, together with a significant reduction in residual deformations, enhances the elastic properties of the fire hose material. The results of the studies have shown that during the first two cycles the material demonstrates the manifestation of short-term creep, which is stabilized at 5-7 modes. To general-ize the experimental studies, the results are approximated by the corresponding trend lines. Deformation curves of the samples were determined under cyclic loading-unloading conditions, which formed hysteresis loops. When analyzing the corresponding curves, it was found that: firstly, during the first two three cycles of loading-unloading, the area of the hysteresis loops decreases. Secondly, the angle of inclination of the hysteresis loops also decreased with each loading-unloading cycle. It was found that the dissipation coefficients of the sleeve material when stretched in the longitudinal direction in the first two or three test modes increases. In subsequent tests (cycle 4-7), the dissipation coefficients decrease and then stabilize at a level of 0.42.

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