Originally Posted by
Trakhak
Mild steel can be stress cycled forever without fatiguing? Aren't metal paper clips made from mild steel? it takes only a few cycles of flexing a paper clip for work hardening to occur, followed by failure.
I think you define the word "flex" differently than I do. You're talking about bending beyond the yield point, commonly called "taking a set", to where it doesn't spring back to the original shape.
I think "flex" for most people means deflecting below yield, where it does return to the original shape. That's not much deflection for a paperclip, because the steel is so weak. You can only spring it a short distance before it yields, but as long as you stay in that narrow envelope, it'll spring back many times with no damage. You'll get bored long before it fatigues.