I have built a model in abaqus using a viscoelastic material. This material is defined by using prony series. I applied a ramp as a pretension displacement then a periodic displacement. My results look good compared with experiment except one issue. When applied a displacement, the load went to relax quickly (stress relaxation due to viscoelastic material) until reach zero. The relaxation disturb my results. In experiment test, I did not get this stress relaxation.

My model material : Elastic + Viscoelastic, Visco step

My questions are:

1. In abaqus, can I control on load relaxation speed or stop it ?
2. Is my issue related to material model or with the abaqus analysis ?

Please see attached, the red color is the load

thanks