Nonlinear Material Model using ANSYS

I am performing the static analysis on hydraulics component where I am using the nonlinear material properties with multilinear kinematic material model having yield ~150 ksi and ultimate strength ~210 ksi. However I am getting first principal stress as 280 ksi and von Mises(equivalent) stress ~ 240 ksi.

I checked for the directional stresses where I find the stress in axial direction as ~279 ksi.

Whether it is possible to have the stresses above the given material limit (in this case true ultimate strength is 210 ksi).

Has anyone seen this behavior or know why it occurs?

Thanks for your reply...