Review of different calculation approaches for the mean coefficient of friction in ISO 6336

Abstract

Important goals in gear design are high load carrying capacity, good noise, vibration, and harshness (NVH) performance and high efficiency. Regarding the load carrying capacity, the international series of standards ISO 6336 [13–15] is the state of the art for its calculation. To ensure reliable calculation of the load carrying capacity of gears and the temperatures occurring during operation, knowledge of the friction in the gear mesh is crucial. Currently, various approaches exist in the literature for calculating the mean coefficient of friction, which weight the influencing variables to varying degrees. In this publication, the empirical approaches for calculating the mean coefficient of friction given in the international series of standards ISO 6336 [13–15] are to be analyzed in terms of their origin and validated ranges, systematically compared, and contrasted. These calculation approaches are mainly covered in the parts ISO/TS 6336-20 [14], ISO/TS 6336-21 [15], and ISO/TS 6336-22 [13], which address the calculation of the scuffing load carrying capacity according to the flash and integral temperature method and the calculation of the micropitting load carrying capacity, respectively. Additionally, ISO/TR 14179‑2 [12] which describes a calculation approach for the thermal load carrying capacity will be included in this review. Besides the analysis of their origin, exemplary comparative calculations for various applications are intended to show possible differences between the various calculation approaches and enable a quantitative evaluation. The overall, long-term goal is to merge and standardize the various calculation approaches for the mean coefficient of friction in the international series of standards ISO 6336.