Evaluation of true stress-true strain relations through the modeling of ball indentation test of reactor pressure vessel steel

The true stress-true strain relation of SA508 steel, the material for reactor pressure vessel, was evaluated with the analytical solutions and experimental equations on the base of the indentation load-depth curve obtained from the modeling of indentation test. The evaluated relation between true stress and true strain is agreed well with that of SA508 steel, which was used to define the plasticity of the material in the modeling. The pile-up deformation on the edge on the indentor began to appear in the stage of fully plastic deformation of material. Because of the pile-up deformation, the contact radius obtained from modeling was larger than those obtained from analytical solutions. The distribution of effective stresses obtained from Tresca criteria along the center axis of indentation was calculated in the modeling. The representative strains, which are defined as the corresponding strains with the maximum effective stresses, have a linear relation with the true strains