Life factor for contact stress

Symbol	Z_NT
Unit	-
Attribute-ID	stress_cycle_factor_pitting_resistance_z_nt_agma_2003
Numeric ID	9886
Value Type	PMDouble

The life factor Z_NT considers the dependency between the allowable contact stress and the number of load cycles that the gearbox is subjected to.

Input options:

User specification of Z_NT:
Corresponding values are contained in AGMA 2003.
Calculation before Z_NT:
The AGMA 2003 calculation method always calculates with decreasing allowable contact stress. However, the user can specifyg the gradient between the load cycle numbers 10⁹ and 10¹⁰ by specifying the life factor Z_NT10. The life factor Z_NT is determined from the required operating time and the speed. If the required operating time is not specified, the life factors for pinion and wheel are set to Z_NT = 1.0.

The life factor Z_NT is only used for the S-N curve calculation. If a component S-N curve is specified in the material of the respective gear, it is used for the load capacity and load spectrum calculations.