OBRABOTKAMETALLOV technology Vol. 27 No. 1 2025 According to the calculation scheme (Fig. 4), the friction force Ffr is an equivalent force, which can be determined according to the principle of finding equivalent forces for parallel distributed forces. Let us determine its magnitude and the point of its application, which is located at the center of the contact line l between the drill bit and the workpiece. According to the scheme of the friction unit, a pair of forces {−Ffr; Ffr} with a moment acts on the indenter (drill bit): ⋅ + = 0 ( ) , 2 fr fr F D d M (1) where D is the diameter of the indenter (drill bit); d0 is diameter of the hole in the counterbody or = + 0 2 fr fr M F D d . (2) For the unit under consideration, Equation (2) relates the moment and friction force. The axial force PN acting on the contact surface of the tool is the projection of the axial force PN by the sine of the angle between the forces. Using the equilibrium condition, and taking into account the normal pressure force on the indenter (drill) surface PN, which is in contact with the counterbody, we obtain: ⋅ ϕ = 0 sin 2 N P P , (3) where P0 is the axial force, N. According to the Amont-Coulomb law, the normal force PN is related to the friction force Ffr, which can be defined by the following equation: Fig. 3. Friction torque values in various MWF environments Fig. 4. Design scheme of the analyzed friction pair: 2φ – drill apex angle, deg; Ffr – friction force, H; P0 – axial force, H
RkJQdWJsaXNoZXIy MTk0ODM1