ISO/CD 6336-22

Calculation of load capacity of spur and helical gears — Part 22: Calculation of micropitting load capacity

Apstrakt

This document specifies a procedure for the calculation of the micropitting load capacity of cylindrical gears with external or internal teeth. It includes formulae for a quantitative assessment of factors influencing the micropitting load capacity. It applies to any gear pair where suitable reference data are available as long as the following criteria are met.
The given formulae in this document are valid for driving as well as driven cylindrical gears with tooth profiles in accordance with the basic rack standardized in ISO 53. They can also be used for teeth conjugate to other basic racks where the virtual contact ratio of the virtual spur gear is less than εαn = 2,5. For double helical gears it is assumed that the circumferential load is equally distributed on both helices. Else, e.g. for presence of external axial forces, this must be considered in the calculation by treating the two gearings of a double helical gear as two adjacent helical gears.
The methods are validated for:
— normal working pressure angle from 15° to 25°;
— reference helix angle from -25° up to 25°;
— virtual contact ratio of the virtual spur gear from 1,0 to 2,5;
— circumferential velocity of the working pitch circle higher than 2 m/s.
The formulae are not applicable when any of the following conditions exist:
— gears with transverse contact ratios less than 1,0;
— interference between tooth tips and root fillets;
— teeth are pointed;
— backlash is zero.
The given formulae are not directly applicable for the assessment of types of gear tooth surface damage such as macro-pitting, plastic yielding, scratching, scuffing and so on, other than that described in Clause 4.
If this scope does not apply, refer to ISO 6336-1:2019, Clause 4.