perfectly plastic material

Hi all,

I have a problem with perfect-plasticity material model in Abaqus. I this simple 2D analysis, I am modeling a beam fixed at both ends and applying temperature loading on it that will cause yielding. The material model is perfectly plastic with,

*PLASTIC

4.85 E8, 0.0

The problem is, stresses go beyond yield limit (4.85 E8) which should not be the case for the perfectly-plastic material model. I would appreciate any comment/help/suggestion.

Regards,

Soner