Experimental determination of friction coefficients in sliding pairs of pivoting devices

Abstract

The study is devoted to the development of a comprehensive methodology for the experimental determination of friction coefficients in sliding pairs of pivoting devices of construction machinery. The relevance of the study is due to the increasing requirements for the accuracy of calculating the moments of resistance to rotation in modern construction machines, where pivoting devices operate under difficult loading conditions. The existing analytical models show significant discrepancies with experimental data, especially when taking into account the factors of preload, geometric deviations and elastic deformations of the rings. The paper presents an innovative experimental approach, including the creation of a specialized test bench with precision measurement of the friction moment, the development of a methodology for accounting for the preload of balls and the implementation of a data processing algorithm using experimental planning. The experimental base of the study includes 240 measurements on 12 standard sizes of four-point ball bearings with diameters from 800 to 2200 mm for various combinations of axial, radial loads and tipping moments. The results show that the equivalent coefficient of friction varies in the range of 0.008-0.024 depending on the loading mode, while the effect of the preload spread is up to 35% of the total value of the friction moment. For bearings with a diameter over 1,500 mm, a nonlinear dependence of the coefficient of friction on the angular velocity with an exponent of $0.23\pm0.03$ has been established. At high tipping moments, a transition from four-point to two-point contact is observed, accompanied by a decrease in the moment of friction by 18-42%. The developed methodology provides an error in determining the coefficients of friction of no more than $\pm8.5\%$, which exceeds the accuracy of existing approaches by 2.3 times. The results of the study open up prospects for optimizing the design of pivoting devices and improving the energy efficiency of construction machinery. The practical significance of the work is confirmed by the introduction of the developed methodology into the design practice of leading manufacturers of construction machinery.