How is plastic strain accounted for under repeated loading in SOL106? I've noticed that although the residual deformation doesn't increase after the first loading event, the plastic strain does increase between the first and second loading event.
What should I make of that?
In this case I'm repeatedly loading in the same direction (+5g(x)). Between loading events, only the constant -1g(z) load remains. I'm a little surprised that the plastic strain is increasing after the first event, while the residual displacements (when relaxed) are not. I think it is an accounting trick, because plastic strain is sort of a nebulous concept when it comes to repeated loading. Basically the local hotspot yields locally again as it is reloaded, but the strain hardening effect prevents growth of displacement. This local second yielding event is added to the strain already accounted for. That is, plastic strain never decreases - it is a cumulative measure of how much yielding strain has occurred, as opposed to a spot on the stress-strain curve.