Results of ISO/TS 6336-22 Evaluating Full Contact Zone

Robin Olson, David Talbot, Mark Michaud, Jonathan Keller, John Amendola

Research output: Contribution to conferencePaperpeer-review


ISO/TS 6336-22 (Calculation of load capacity of spur and helical gears - Part 22: Calculation of micropitting load capacity) is the ISO technical specification containing a proposal for calculations of the risk of micropitting in gear sets. Micropitting is a Hertzian fatigue phenomenon that appears as ultra-fine cracking and pitting on the flanks of gear teeth. Since progressive micropitting can lead to macropitting and flank damage, critical applications such as wind turbines, marine drives, and high-speed gear drives seek to accurately predict whether their designs are susceptible to this damage. ISO/TS 6336-22 assesses micropitting risk through a safety factor that is calculated as the minimum specific film thickness in the contact zone divided by a permissible specific film thickness. In a previous paper, the calculations were performed using the simplified method (Method B) that evaluates points on the path of contact. This was done for three gear sets that experienced micropitting in operation. The minimum specific film thickness for the two field cases was very high, which indicates that the gears were operating in the full elastohydrodynamic lubrication regime. A more accurate calculation for these cases (Method A) calculates the specific film thickness across the entire contact zone. This paper applies this method to the case study from the previous paper. The results are compared to micropitting observed in operation. Results are also compared to the results of the previous paper. Conclusions are made regarding the accuracy of both methods compared to the field cases and relative to each other.

Original languageAmerican English
StatePublished - 2022
EventAmerican Gear Manufacturers Association 2022 Fall Technical Meeting, FTM 2022 - Rosemont, United States
Duration: 17 Oct 202219 Oct 2022


ConferenceAmerican Gear Manufacturers Association 2022 Fall Technical Meeting, FTM 2022
Country/TerritoryUnited States

Bibliographical note

See NREL/CP-5000-83100 for preprint

NREL Publication Number

  • NREL/CP-5000-85163


  • gearbox
  • micropitting


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