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.
Is there anything that I miss in my code? I will appreciate your help. Thanks! If the problem were solved, I will write a tutorial for this and post it on iMechanica and Github.
Notes: The Fortran code is based on VUMAT from Rutger's repo: https://github.com/rutger-kok/composite_cdm_tan
| Attachment | Size |
|---|---|
 1.png | 33.32 KB |
| 2.png | 39.61 KB |
| 3.png | 186.92 KB |
| 4.png | 187.13 KB |
 VUMAT_Elastic_copy.txt | 5.14 KB |
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?
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?
Hi,
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?
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:
1. How does I let ABAQUS know/(How do I toggle) to use Updated Lagrangian formulation, given that I code my constitutive relation in the format mentioned above?
Thank you.
Srikanth
Research Scholar
Department of Mechanical Engineering
IIT Madras, India.
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 http://www.soilmodels.info/ node17.html website. Like UMAT I use the actual version on your uibk.ac.at website (umat_vec.f with consistent tangent operator and error control) for application I try the example of a triaxial test. Please any one have already use the hypoplastic model for any explicit analysis? Please any experience around the UMAT – VUMAT interface for hypoplastic model? Best regards