
The safety factor (SF) is calculated is differently depending on the mean stress theory used. The Goodman theory is linear, so the SF is simply the equivalent alternating stress at the specified design life from the SN curve divided by the equivalent alternating stress. The other mean stress theories are nonlinear.
To verify the SF calculations, insert a Fatigue Tool with the desired mean stress effects active and find the SF. Then insert a second Fatigue Tool and specify the SF from the previous Fatigue Tool as the scale factor in the second Fatigue Tool. If the SF is calculated properly in the first Fatigue Tool, then the calculated SF in the second Fatigue Toll should be 1.0 and the calculated Life in the second Fatigue Tool should be equal to the design life specified for the SF calculation in the first Fatigue Tool.

