OK, I tried the perfect plasticity model, the stress value did not reach the ultimate stress, but actually it is not possible caused by the perfect plastisity model:
If the stress value is higher than yield stress then it will not increase so it is evident that the stress doesnt reach the ultimate stress... In my opinion, this mode is ok for special materials but in my case it is not ok. I have a measured material curve and it is not similar to the perfect mat. model. The best case was the definition with the exponential law but it leads to too high stress value.... I dont understand it....