Hello friends,

I have a question about the data check phase of VUMAT. VUMAT manual said as the following:

In the data check phase of the analysis Abaqus/Explicit calls user subroutine VUMAT with a set of fictitious strains and a totalTime and stepTime both equal to 0.0. This is done as a check on your constitutive relation and to calculate the equivalent initial material properties, based upon which the transverse shear stiffness (if VUMAT is used to define the material response of shell elements and material transverse shear modulus is defined) and the initial elastic wave speeds are computed.

I want to know if we need to program this phase in our VUMAT code or it will be proceed automatically by Abaqus itself? I found that some people used "If (stepTime==0) Then" to program this phase in VUMAT, however, others did not do it, especially the example provided by the VUMAT manual. From my experience, we will get different results with to without this. Wish we can discuss it.

Thanks!

Regards,

Xingyi.