This is probably the simplest of all nonlinear material models. It considers that once the yield stress is reached, stress becomes constant and only strain continue to increase.
That’s a very big assumption and probably only valid for steel materials near the yield stress (in reality stress continue to increase a bit until the ultimate stress limit is reached)
It’s a very easy model to set-up (you only need the yield stress value…), but don’t overuse this model just because this is the only one you can easily setup as you don’t have the required stress-strain data… you would just get wrong results.
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