Dear Erik Yes, I have read the chapter. The chapter says that "multilinear hardening behavior is described by a piece-wise linear stress-total strain curve, starting at the origin" but what it does not say is that you cannot start at the origin of the multilinear curve (0 strain, 0 stress) when giving points by the command TB,PT (ansys error).
The chapter also says that "The first stress-strain point corresponds to the yield stress", but what it does not say is that the first point must have 0 strain (otherwise, ansys error). How do you define then the Young modulus?
Thus, I find the chapter confusing and I ask for clarification in my post.