UMAT of beam B23

[Salvanto2]

Hi, I start to study the UMAT subroutine.

I want to change the mechanical constitutive behavior of a material in ABAQUS. I have the Young's module that it varies rspect the coordinate "X".
I don't understand the meaning of the material Jacobian matrix (DDSDDE).

Can anyone explain the meaning to me?

 

[Dave442]

Check for UMAT in the "User Subroutines" guide in the 2018/2019 Abaqus documentation:

"DDSDDE(I,J) defines the change in the Ith stress component at the end of the time increment caused by an infinitesimal perturbation of the Jth component of the strain increment array."

This section also contains an example UMAT for a linear viscoelastic material with theory and FORTRAN code which might be helpful.

 

[Salvanto2]

Can you give me this example so that you have everything clearer?
If I have a Bernoulli euler beam modeled on Abaqus as a "B23" element which should be Jacobian matrix (DDSDDE)? Only the Young's module? It has only one element, or is a matrix 3x3?

Thx.

 

[Mustaine3]

I think you don't need a UMAT to change the Youngs Modulus with location. It should also work with Field Variables and a USDFLD.

 

[Salvanto2]

I have to do even more complex cases, for which I will necessarily have to use UMAT, so I wanted to understand it very well.

Can you answer to my question? Thx