Friction Torque Experimental Determining in Radial Angular-Contact Ball Bearing under Combined Loading

Аuthors

Balyakin V. B.^*, Lavrin A. V.^**, Dolgikh D. E.^***

Samara National Research University named after Academician S.P. Korolev, Moskovskoe shosse, 34, Samara, Russia

*e-mail: 029-029@mail.ru
**e-mail: av_lavrin@mail.ru
***e-mail: i@dolgih-work.ru

Abstract

It is urgent to know the exact values of friction torques, originating in the bearing subassemblies, while liquid jet engines designing. For example, torque characteristics are of most importance while the rocket engine steering drives elaboration. The rolling motion subassemblies are being as well employed in the hinged units of the liquid jet engines as path-forming elements for the low-boiling fuel components supplying, where application of the radial ball-bearings is the most rational way for the thrust effort transfer with contemporaneous mobility ensuring. Laboratory installation capable of creating both radial and axial loading within the specified range was developed to confirm experimentally the newly developed technique for the torque moment computing of the low-speed bearing under conditions of grease lubricant application. Experimental technique for obtaining reliable torque characteristic of the bearings under study was developed. All basic types of errors inherent to the said installation were accounted for herewith. The 6-208Y2 serial ball bearing, which is widely applied in the hinged steering units of the Russian-designed liquid jet engines, was employed for the study. Operating conditions of the selected ball bearing are characteristic for the combined loading mode with the friction torques implementation, which were computed in advance according to newly developed analytical dependencies. Processing of the obtained empirical data array was performed with a well-known technique for the indirect measurements processing with a possible range of values determining on the assumption of the 99% probability. Experimental studies have been performed in the ranges 0-6 kN for axial and 4,905-15,696 kN for radial loads, which corresponds to the working area of the RD-107 rocket engine steering units loads. As the result, it was demonstrated that, the theoretical method was confirmed with a probability of 0.99 by experimental data, and the maximum error herewith does not exceed 9%. The obtained minor discrepancies between theoretical and experimental data confirmed the reliability of the newly developed technique for design and verification computations of radial ball bearings, including those employed in rocket and space technology products., Along with theoretical calculations, the performed experiment revealed the possibility of torque characteristics spread of the steering units manufactured according to uniform specifications with account for the of individual operating conditions effect of the support ball bearings. The obtained results may be applied to the analysis of test results of mass-produced products  to assess their adequacy for suitable application. The said technique may be applied, among other things, for determining the permissible increase in the friction torque of steering units, based on its bearings functioning. The data obtained may be employed for assessing condition of the steering units based on test results and confirming normal functioning of all other tribo-joints in the cases when direct measurement of their characteristics is difficult or impossible for technological reasons.

Keywords:

low-speed ball bearing, experimental installation, combined loading, friction torque

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