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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(see at our work Shadrinov N.V et al. (2018)) is that heating occurs exclusively in the weld zone, where the ferromagnet is located, which minimizes the deformation of the welded parts in volume. We also developed and manufactured a special mold from polytetrafluoroethylene, which prevents the molten sample from flowing out. PTFE was chosen as the material for the mold because of its high heat resistance, low coefficient of friction and adhesion. Also, PTFE is not subject to heating when exposed to magnetic induction. The essence of the welding method is illustrated by the drawing (see Fig. 1), which schematically shows the proposed device. The heating element 1, which is a ferromagnet (thin steel wire mesh), is placed between the welded parts from UHMWPE 2, which are installed in the mold 3, made of a non-ferromagnetic material. When the magnetic induction source is turned on, the induction field heats the ferromagnet in the weld zone of UHMWPE to the welding temperature (190~270 °C), and the pressing force is controlled on the welding machine "ROWELD P160B". Temperature is measured using a thermocouple placed near the weld. The temperature rises quickly within 3 ~ 7 minutes. The potentiometer on the power supply unit of the induction heater controls the power and the welding temperature. The exposure time during heating is about 30 seconds, then the device of the induction emitter is turned off. The welded UHMWPE components are left in the mold until the weld will be completely crystallized. 3. Results and discussion Welding was performed using a mold to increase the pressure, and to avoid the formation of burrs around the weld (see Fig. 2, a). It was shown that with an increase in the pressure and temperature without using a mold the molten part of the sample flows out, as a result of which the samples are pressed in an unmelted zone, so welding does not occur (see Fig. 2, c). Samples were welded at temperatures of 190, 210, 230, 250, 270 °C to achieve the optimum mode (see Table 1).
Table 1. Mechanical characteristics of welded UHMWPE samples. Temperature (T), °C Tensile strength ( σ p ), MPa
Elongation at break ( ε p ), %
monolithic UHMWPE
26,1 24,7 25,9 25,7 25,3 22,8
400-420
190 210 230 250 270
28-30 37-40
168-170 276-280 215-266
Fig. 1. UHMWPE sample welding scheme.
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