To me it doesn't make sense to apply standard text book reliability factors to the endurance limit for an infinite life check. IE. Modified Goodman Theory Failure Criterion. I can't find any references that provide definite direction to perform it or not to perform it. The FE manual doesn't have it as a factor, but it can't be used as reference. With the typical fatigue chart I am looking at it normally has the endurance limit past 1E7 cycles. Since the cycles go well past the 1E6 for the enduring limit, adding a reliability factor does not make sense. Adding surface finish, geometry, and notch factors does make sense. Can anyone point me to a good reference on this that says it in black and white?