Modelling plasticity of polymer material 2

[InesGomes]

Hello, I need to model the plastic behaviour of a polymer material (polypropylene). I have data from the tensile test, however I'm not sure how can I assess this curve to convert it to true stress-strain curve. Because, I know that I need to delete the data from the elastic behaviour (before the yeld point = 20,09 MPa), however, if we look to the graph, I will have different strain results for the same stress value, and my question is: can abaqus solve this or it wil

l not converge?

 

[rothers]

Where did that red true stress stain curve come from ?

 

[InesGomes]

The red true stress strain curve was calculated by this formulas:

 

[SWComposites]

Might be easier to use a simple bilinear material model in Abaqus.

For a more complex stress-strain curve, Abaqus uses a tabular input of values. Whether or not Abaqus can converge to a solution with your material will be a function of the stress state un your model.

Suggest you first model the tensile specimen and see if you can duplicate the measured data.

 

[swimfar]

A few notes:
1. The conversion formulas you are using are only valid for uniform elongation (i.e. before necking), and assume a Poisson ratio of 0.5 for the plastic deformation (often a reasonable assumption).
2. Do you actually care about the material behavior at 600% strain? Limiting your model to the range you care about will make things easier.