Mismatch between the input material stress strain curve and generated curve in Ansys.
I have a question regarding the Multilinear Isotropic hardening in Ansys, more specifically the mismatch between the input material stress strain curve and generated curve in Ansys.
I have created a simple 2D model (plane stress), which is supported on the left side (fixed support). Load is added on the right side in a negative Y direction. I used second order hex mesh and applied local sizing to the edge where the stresses are the highest.
For elastic material properties I have defined Young’s Modulus (160 000 MPa) and Poisson's Ration (0.33). Yield point of the material is 410 MPa, at 0.002 plastic strain (determined with the offset method). The elastic limit is set at 345 MPa. For plasticity I have defined Multilinear Isotropic Hardening, where the first point in the table is the elastic limit at zero plastic strain. All points in the table taken from the true stress strain curve. Auto time stepping is turned ON (min 200 substeps), as well as large deflection.
With the load of 300 N, stresses in the magnified corner exceed the yield point.
I have created a Named Selection on the node in the proximity of max stress and plotted max unaveraged Von-Mises stress versus max unaveraged total strain to create a stress-strain curve. As you can see from the right graph, the stress strain curve from Ansys is not completely aligned with the material curve. In the elastic part (up to 345 MPa) the curves are completely aligned, but there is a deviation as soon as the plastic strain occurs.
Eventually the curves realign, and if the stresses are well beyond yield this mismatch is not a problem. But I am interested in the region just below the yield, therefore this deviation is not acceptable, as the difference in stress, for example at 0.003 total strain, is around 20 MPa.
Can anybody help me how to resolve this issue?