A fifth mean stress correction is by empirical data, which is the selection “Mean Stress Curves” in
the Fatigue Details View. Mean Stress Curves uses experimental fatigue data to account for
mean stress effects. There are two types of stress curves available, mean value stress curves
and r-ratio stress curves. For mean stress value curves, the testing apparatus applied a constant
mean stress while applying a varying alternating stress. In practice, this is relatively hard to do.
R-ratio stress curves are similar to the mean value stress curves, but instead of maintaining a
particular mean stress, the testing apparatus applies a consistent loading ratio. This is typically
easier to perform in actual practice.