Query regarding 2D VUMAT

[Tirthkumar12]

I have a 2D VUMAT which works if I keep my element type plain stress but if I change it to plain strain it shows
"***ERROR: Bad Material definition in element number 1244 instance UNIT_CELL:
zero or negative initial dilatational modulus caused by bad material
data. Please check your material input and any initial conditions if
necessary." Please Help! THANK YOU?

 

[FEA way]

Apart from the obvious fact that those element types have different stress and strain/deformation gradient components, there are some special considerations when preparing VUMAT for plane stress (but not plane strain) elements. They are described in the documentation chapter User Subroutines —> Abaqus/Explicit User Subroutines —> VUMAT (paragraph "Shell and Plane Stress Elements").