[tintin (OP)]

I'm pinned by the concept of "saturation stress" in some stress-strain or stress-Temperature graphs. Who knows what this "saturation" signifies?

[RD]

when a ductile material is cycled at constant plastic strain amplitude, the maximum stress in one cycle rises and then saturates.
The saturation stress is identified as being to an excellent approximation equal to the endurance limit of the material,
as measured by conventional stress cycling tests.

http://cat.inist.fr/?aModele=afficheN&cpsidt=1411797