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stress versus strain data in mat file

Michal Lukac

Hi, 

I need to use my own matarial data for elastic-plastic analysis.

I have Stress - strain curve from test data, So I calculateed True strain and true stress according to equations:

σ_true = σ_test*(1+ε_test) and 

ε_true = ln(1+ε_test)

from the ε_true values is then subtracted ε_true at σ_yield.

So I have ε_true from 0 to e.g. 0.105 and σ_true from σ_yield to e.g. 1400.

But in the original marc mat files the ε_true is from 0 to 1.0   

So do I do something wrong or can I use the calculated data?

Thanks for help

m.

  • 0

    Dear ,

    Marc expects the plasticity table data in equivalent plastic strain vs true stress form.

    True stress = eng stress * (1+ engg strain)

    'Total true strain = ln(1+engg strain)

    Plastic strain = total true strain - (E/True stress)

    Hence the first point in this table will always be (0, yield stress)

    Use below format to convert the engg stress strain data to Marc data,

    Make sure in the material properties menu, you use yield stress 1 while using actual plasticity data in the table.

    Regards,

    Kiran

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