OBRABOTKAMETALLOV Vol. 25 No. 2 2023 technology line to the drop surface and the projection of the surface of the steel workpiece. One of the constructed edge angles of a coolant wetting is shown in figure 4. According to the described method, the limiting wetting angle of every tested coolant brand was determined. Ta b l e 1 Indicators of the coolant lubricating effect Coolants µ Kc Without coolant 0.604 – Coolant 1 0.148 0.25 Coolant 2 0.117 0.19 Coolant 3 0.130 0.22 Coolant 4 0.090 0.15 Coolant 5 0.082 0.14 Coolant 6 0.119 0.20 Coolant 7 0.119 0.20 Ta b l e 2 Coolant densities Coolants ρ, kg/m3 Coolant 1 947.76 Coolant 2 926.56 Coolant 3 957.60 Coolant 4 945.29 Coolant 5 953.43 Coolant 6 940.36 Coolant 7 945.14 Ta b l e 3 Coolant limiting wetting angles Brand of coolant Θ, ° Coolant 1 16.13 Coolant 2 12.6 Coolant 3 10.02 Coolant 4 3.38 Coolant 5 6.2 Coolant 6 5.72 Coolant 7 9.1 Fig. 4. Measured value of the coolant limiting wetting angle Results and discussion The obtained results of the evaluation of the lubricating effect of a coolant, its density and wetting action are presented in tables 1–3. In the current study, it is assumed that the efficiency coefficient of coolant for lubricating action Kc depends on the coolant density ρ and the wetting contact angle Θ. In order to establish the empirical dependence of these parameters, the computer program STATISTICA 12 was used. As a result, two graphical dependencies were built Kc = f(ρ;Θ): quadratic and linear (Fig. 5). The parameter Var1 denotes the coefficient Kc, the parameter Var2 is ρ, kg/m3, and the parameter Var3 is the wetting edge angle Θ, degrees. In addition,
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