Hi
I want to write the UMAT for hypo-elastic plastic material behavior.
I have to find L velocity gradient L.
The problem is I don't know how to calculate Fdot The derivative of deformation gradient. I have DFGRD1 and DFGRD0 and time increment.
Is it correct Fdot= (DFGRD1 - DFGRD0)/ delta(t)
I think it is not true but I don't have any idea about what is correct
best regards
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