AGMA 15FTM26 PDF

Micropitting is a surface fatigue phenomenon on highly loaded gears with case-hardened gear flanks. Main contributors are local stress, surface roughness, sliding speed, and lube oil properties.

General influence factors, testing, and earlier calculation methods were described in 11FTM15 [1]. Meanwhile, a new version of the ISO Technical Report, TR 15144-1:2014 [2], was issued. It is intended to become an ISO Standard within the next years.

This paper describes the definition of micropitting, the actual calculation method, and its application to practical examples where micropitting has either occurred or not. The examples give evidence that the Technical Report reliably predicts the risk of micropitting where it is later found on the gear flanks. For cases where no micropitting occurs, the calculated safety factors are sufficiently high. Operating conditions for some examples are out of the validated range of the Technical Report.

Examples are selected from the fields of high-speed gears, cement mill drives, extruder drives, and wind turbine gears. The examples are limited to the authors’ own experience and are not considered a full-scale validation of [2].