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Strain rate dependence with failure and damage model *MAT_ADD_DAMAGE_DIEM is not working

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(@hauser-lukas)
Barista
Joined: 6 months ago

Hello everyone,

I have a problem regarding the implementation of a strain rate dependence with the failure and damage model DIEM (DITYP=3: FLC).

In this case, I would like to check the failure using DIEM as a function of strain rate.

For different strain rates, the failure should be defined by the FLC curves corresponding to the strain rates.

To do this, I used the failure and damage model *MAT_ADD_DAMAGE_DIEM in combination with the material model *MAT_3-PARAMETER_BARLAT (without strain rate dependence).

As defined in the keyword manual, a table with strain rate dependence was stored for DITYP = 3.0. The individual FLC curves were also defined by setting the points in the *DEFINE_CURVE keyword for the critical plastic strains as a function of alpha (the ratio of the principal plastic strain rates).

However, for different strain rates, only the FLC curve defined first in the 2D-TABLE is used as the active failure criterion, i.e. there is no strain rate-dependent query or change of the failure criterion when the defined critical strain rates are exceeded.

I have attached my material model including the definition of the material histories (for tracking and visualising the instability/failure criteria in LS-PrePost). Also attached is a simulation for a Nakajima test corresponding to the strain state for alpha=-0.5. Even with reduced time (parameter ENDTIME) and thus significantly increased punch speed, no strain rate dependent failure occurs.

Can anyone help me find out why my strain rate dependency doesn't work for DIEM?

I would be very grateful for any feedback with a possible error source / suggestion for solving my problem.







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