Life factor at 10^10 load cycles (test cond.)

With the aid of the life factors Z_NT and Y_NT, the higher permissible stress can be taken into account in the calculation of the load capacity when designing in the fatigue strength area.

When calculating according to the DIN 3991 calculation method, the calculation is made against the fatigue strength (Z_NT = 1.0; Y_NT = 1.0).

For calculations according to ISO 10300 (2001) and ISO 10300 (2014) the following options are available:

• Direct input
  The specification can be made manually using a numerical value.
  
  
• No Input
  For calculations according to ISO 10300 (2001) and ISO 10300 (2014), the life factor is determined according to the respective calculation specifications.
  The curve of the life factors over the required number of load cycles according to ISO 10300 (2001) or ISO 10300 (2014) is stored internally. Above 5∙10⁷ load cycles, the curve for the long-term fatigue strength according to ISO 10300-2 (2014) is used for Z_NT, and the corresponding long-term fatigue strength curve for Y_NT (see figure) above 3∙10⁶ load cycles according to ISO 10300-3 (2014). Thus, a decrease of the sn-curve in the fatigue strength area is expected. The gradient of this part of the sn-curve can be specified by the user with the life factors Z_NT10 and Y_NT10. They represent the ratio of the strengths at 10¹⁰ load cycles to the fatigue strengths (Z_NT = 1.0; Y_NT = 1.0). The number of load cycles for pinion and gear are determined from the speed and the required service life. If neither the life factors nor the required service life are specified, the default value 1.0 is used internally for the life factors.

Material abbreviations see ISO 6336-1:2006 Table 2 - Materials