PSI - Issue 30

A.A. Chirikov et al. / Procedia Structural Integrity 30 (2020) 23–27 Chirikov A.A., Sokolova M.D., Gogoleva O.V. / Structural Integrity Procedia 00 (2020) 000–000

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Fig.2. Welded samples: a) with a mold; b) with a mold at 270 °C; c) without a mold.

A visual inspection of the welds did not reveal external defects of the weld at temperatures of 190, 210, 230, 250 °C. The seams turned out without sagging, the latitude of the seam is the same (see Fig. 2, a). In Fig. 2b (sample welded at 270 °C) brittle wax-like formations are visible, most likely due to this, a deterioration of the weld strength is occurred (see Table 1). It was established that the welding mode at a temperature of 250 °C and a heating time of 30 seconds at a pressure of 2.3 MPa is the most optimal for ultra-high molecular weight polyethylene. Adhesion strength is more than 95% in this welding mode. Elongation at break is more than 60% of the value of a monolithic sample. An increase in the welding temperature above 250 ° C leads to a decrease in the mechanical characteristics of the weld, which is explained by thermal destruction processes with the formation of degradation products whose cohesive strength is lower than the cohesive strength of the initial polymer as written in studies by Efremova et al. (2013). 4. Conclusion A method has been developed for welding ultra-high molecular weight polyethylene by installing a ferromagnet in the weld zone, which is heated by magnetic induction, which leads to the expansion of the polymer, creating the pressure necessary for welding. A mold was developed and manufactured, which excludes the formation of burrs around the weld, which made it possible to significantly improve the quality of the welded joint. It has been experimentally established that the optimal mode for this polymer is welding at a temperature of 250 ° C and a heating time of 30 seconds at a pressure of 2.3 MPa. It is shown that in this mode, the weld strength is more than 95% and the relative elongation at break is 66% of the value of the monolithic sample. Acknowledgments This work was performed as part of the RFBR project 19-38-90141 (CIT&S: АААА - А 20-120060890006-4). References Andreeva, I.N., Veselovskaya, E.V., Nalivayko, E.I. and etc., 1982. Sverhvysokomolekulyarniy polietilen vysokoy plotnosti [High density ultra high molecular weight polyethylene], Khimiya, Leningrad, pp.80. Baloshin, Y.A., Ryjov, M.G., Silin, P.N., Sorokin, A.A., Ustinov, M.A., 2013. Ispol’zovanie blijnepol’nogo VC-zondirovaniya dlya ocenki stepeni poverhnostnoy aktivnosti polietilenovogo pokrytiya truboprovodov [The use of near-field high-frequency sounding to assess the degree of surface activity of the polyethylene coating of pipelines], Journal of Instrument Engineering 56(1), 58-61.