stresslearner,

Rather than adding your question to existing threads, start your own.

It looks like you are referring to the B31.1/B31.3 sort of stress evaluation.

Since expansion stress range is strain-based, actual stress does not exceed yield - even with excessive strain. The calculated expansion stress range (assuming elastic response) can then be higher than yield.

In terms of stress, keep that categories separate - yielding is the mode of failure for force-based loads and fatigue is the mode of failure for strain-based loads.

The Tresca (Maximum Shear Stress) Theory of failure is used for both force-based load and strain-based load evaluation.