Hi all researchers
I'm writing user material for shell elements. For writing VUMAT abaqus says that I must write constitutive equation for plane stress condition and I must define thickness strain increment (strainInc(i,3)) but in there is nothing in the abaqus manual about writing UMAT for shell elements and it doesn't say that in must provide relation for thickness strain. Did anyone know about this?
What are the points that I must consider in writing user materials for shell elements?
Any help appreciated
Dear Mhdi
First of all you should read Abaqus documentation. It has many explanations and examples. you can also read the file below. It is useful too.
http://imechanica.org/files/Writing%20User%20Subroutines%20with%20ABAQUS.pdf
Dear readers
if you are using shell elements with Abaqus standard, then you should write a umat for a user material. In this case, the big difference with the vumat is the calculation of the stiffness matrix (which doesn't exist in the vumat). For shell elements, you should calculate the stiffness matrix (DDSDDE) as for the plane stress case (NDI=2 and NSHR=1)
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