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Abaqus VUMAT

Abaqus VUMAT doesn't given identical results for orthotropic linear elastic material

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Dear iMechanica community,

Hi! I am trying to verify Abaqus VUMAT with simple examples so I wrote a VUMAT for orthotropic material and compare the result with Abaqus built-in material model (Elastic -> Engineering constants). The material constants are given in 1.png and 2.png. All other settings from part to mesh is identical. The stress distribution of built-in material model is in 3.png and the stress distribution of VUMAT is in 4.png. The discrepancy is not ignorable. The VUMAT code is also attached as a .txt file.

Input file for the Single crystal plasticity subroutine Nonlinear Finite Elements for Continua and Structures by Ted Belytschko

Can anyone provide me with the input file for the example shown in the book Nonlinear Finite Elements for Continua and Structures by Ted Belytschko et al? The poly-slip, rate-dependent, single crystal plasticity VUMAT subroutine that is available publicly is attached in the following link. I have been trying to reproduce the results in Fig. 13.11 to Fig. 13.13. in the book, but am not successful in doing so. Can anyone please provide me with a working example input file for the problem?

Can someone post an example of UMAT and VUMAT for the same elasto-plastic problem?

I want to understand how the stress update algorithm is modified for the different definitions of stress rate in ABAQUS/Standard and ABAQUS/Explicit formulations. I know the relationships, I just want to see how it's coded in a subroutine.

Also, the Hughes-Winget algorithm is used to update the stress defined by the Green-Naghdi stress rate by using the Jaumann rate. How to implement that in VUMAT? Can someone please post an example to clarify these aspects?

How to combine VUMAT an VUEOS in Abaqus


I have written a VUMAT for Johnson Cook Model. I would like to use subroutine VUEOS to define linear Mie-Gruneisen equation of state. The USUP type VUEOS subroutine can be found at Abaqus Documentation.

However, I am not able to figure out how to combine the two subroutines. What needs to be called from VUEOS into VUMAT?



Question reg ABAQUS-VUMAT and Updated Lagrangian formulation.

Hello all,

I am working on implementing a viscoelastic constitutive model from a hyperelastic stored energy potential (for finite-elasticity) and a dissipation potential (for the viscouls evolution). The elastic constitutive relation, hence derived from the stored energy potential is rate-independent and it is expressed as T(Cauchy's Stress) = f(B), where B is the Left-cauchy green deformation tensor.

The evolution equation is derived out in an objective rate form, which I am integrating over time using a 2nd order accurate explicit method.

My question:

Abaqus VUMAT for hypoplastic law

Please, I’m investing about the hypoplastic model for granular materials to study the behavior of sand under a dynamic excitation. I try to use the UMAT – VUMAT interface, Interface between UMAT (Abaqus/Standard) and VUMAT (Abaqus/Explicit) from node17.html website.

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