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Logrithmic plastic strain formula confusion - urgent

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I am really confused how to input the hardening values for crushable foam model. Abaqus wants to input the stress - strain values in hardening table as true stress and log plastic strain.

In Abaqus manual the formula for calculating log plastic strain is = ln(1+nominal strain) - true stress/E

But when I use this formule to convert my nominal strains into log plastic strains, the plastic strains decreases as the true stress increases in the densification region, and thus It is impossible to feed these strains as they are no longer in Ascending order.

Do you know how to deal with this situation? please see the attached figure for more clarification

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