Currently I try to modell an adhesive in Single Lap shear Joint. As Input data for plasticity I want to use the Test data derived from another shear test (Thick adherent tensile shear test) that describes a simple shear deformation. My Gammar in this tests reaches until 4 so i have large deformaion. For my Plasticity Curve in Abaqus I need to transform the Engineering Stress (actual force/initial Area) first into true /Cauchy Stress and then need to calculate the equivalent Stress according to von Mises. But how can I determine the cauchy Stress when I only know about my Engineering Shear Stress. Are the Piola Kirchhoff stress tensor and my Engineering Stress tensor the same ? I assumed this state for engineering stress tensor (0 t_12 0; t_12 0 0; 0 0 0) where t_12 is my measured Stress from shear test. How can I derive the 1. Piola Kirchhoff stress tensor from Engineering Stress values I get from shear test in order to calculate from 1. Piola Kirchhoff stress tensor the Cauchy stress tensor?