How to define Abaqus UMAT subroutine for perfectly, linear and nonlinear plasticity?

More Majid Tanbakuei Kashani's questions See All

How can I change Global CSYS?

Hi, How can I change global CSYS from rectangular to cylindrical in the initial step in Abaqus? I want to map radial and tangential stress components to the elements and nodes. Thanks.

03 April 2018 1,355 2 View

How can I define crack on .odb file and mapping the results as initial values?

Dear friends, As a part of my project and after the first step of simulation, I have to put a crack on the .odb file and then simulate the crack propagation with considering the initial stress and...

11 December 2016 8,222 3 View

Error for changing the material property from initial to the soft one?

Hi everyone, I am working on a project in which Young's modulus is changed during Abaqus simulation. Actually, the soft material with the value of 1/10 of initial Young's modulus should be used...

11 December 2016 4,877 1 View

How can I change material properties of elements during simulation regarding stress values in Abaqus software?

11 December 2016 2,833 3 View

Is it possible to use defined element and node sets in Abaqus subroutine?

Hi, I have to use some element and node sets in the Abaqus subroutine which already are defined in the model. Anybody can help me how can I do that please?

10 November 2016 7,945 5 View

How can I use Abaqus Script to overwrite the analytical data to the Abaqus results?

Hi, In my project, I have to extract the stress results in the last step of simulation and then use theses values in some equations and overwrite the calculated values as the initial stress (S11,...

10 November 2016 4,549 3 View

Why are my results, with the same conditions, different in ABAQUS Standard and ABAQUS Explicit?

10 November 2014 6,676 5 View

How to define and get results (stresses) for certain points of a model in abaqus, using python? When the size of the model changes?

I want to do a parameter study of a aixsymmetric cylinder in Abaqus. I want to create several jobs where I get the stresses for 3 different points in my model. These points are defined. I wrote a...

01 March 2021 10,078 1 View

Joint behaviour in Abaqus is not captured well?

I am working on roof joint and trying to simulate the behaviour in Abaqus. I am successful in running the model but the final graph does not follow the experimental curve in the negative direction...

01 March 2021 6,661 3 View

Which one is easier and better at modeling slender masonry structures? ANSYS or ABAQUS?

I need to model masonry and reinforced concrete minarets for my MSc thesis. Which one is easier and better at modeling slender masonry structures? ANSYS or ABAQUS? (Or any other program for just...

01 March 2021 736 3 View

How to assign different material properties to each element in Abaqus ?

Hello, I am writing a python script to generate my model and write the input file. The problem is I have 1000 elements in my mesh and I want to assign different material properties to each...

01 March 2021 9,511 3 View

How to define tie constraint between rigid body and another part in dynamic explicit model of Abaqus?

Hi dear researchers I connected a rigid body into the part of my structure by tie constraint and then I added displacement to rigid body, in static general step every thing is fine and these two...

28 February 2021 3,442 2 View

How to modify Johnson cook equation in ABAQUS?

I wanted to add an extra parameter to the existing Johnson cook equation in the ABAQUS simulation. How to add those extra parameters. Ref: A modified Johnson-Cook material model with strain...

28 February 2021 4,841 3 View

For modelling epoxy-based matrices (in composites), which model in ABAQUS is the most suitable, Concrete damaged plasticity or Drucker-Prager model?

I am working on developing a micromechanical FE model for predicting kink-band formation in UD composites. To model matrix plasticity, which model, out of Concrete Damaged Plasticity and...

28 February 2021 5,415 1 View

How to find the right number of integration points in second order 3d finite elements?

I am familiar with finite element simulations and numerical schemes like the Gauss Legendre quadrature. I also know that the Gauss integration yields exact values for polynomials up to degree 2n-1...

27 February 2021 6,818 3 View

How can we use a hybrid element in Abaqus Dynamic/Explicit for impressible materials?

Hi, all! How can we use a hybrid element in Abaqus Dynamic/Explicit for impressible materials? I have not find the choice for explicit element in Abaqus CAE. I am wondering whether it is possible...

25 February 2021 9,936 2 View

Is it possible to do optimization for a submodel in Abaqus?

I'm trying to run an optimization in Abaqus for a submodel with no luck, jobs are not being create for submission. Is this even possible? or is Abaqus limited to do Opt. for the model itself...

24 February 2021 4,908 5 View

Maulik Kotecha Popular answer

By any chance anyone of you have Fortan codes provided in Appendix B of the book " Introduction to Computational Plasticity by Fionn Dunne, Nik Petrinic". I read this book and I found it very useful. The publisher has made the codes unavailable. I was wondering if anyone has these codes.

Shreeraman Swamynathan

Hi,

If you are new to UMAT and Abaqus, there are some good tutorials and pdf's available online (try imechanica).

Ideally, I would first find the correct constitutive relation that would suitably model the material behavior. (tricky part)

Once point two is done, writing a FORTRAN code would not be such a big problem, assuming you are familiar with programming.

Regards,

Shree

Alaa Elsisi

Hello

You need to install C++ and Visual FORTRAN , then you will need to write you material model by using FORTRAN language, finally you will compile the code.

There are a lot of tutorials about this, you can find them online.

Majid Tanbakuei Kashani

Hi Shreeraman and Alaa,

Many thanks for your response, but my question is about the C matrix wich is shown the relationship between stress and total strain in elasto-plastic materials. I would like to know the how can I find the C matrix for perfectly, linear and nonlinear plasticity to defined it in UMAT subroutine.

Many thanks again.

Majid, you can find this in any theory of plasticity book. You will need two matrices for implicit Analysis. One is the secant matrix and the other is the tangent matrix. I can send you Ansys example it are approximately similar to Abaqus just few changes.

Alaa

Thanks

Hi Alaa,

Would it be possible for me to have the Ansys file please? Many thanks in advance for your help.

Majid

Mohammad Kashfi

Dear Majid, in the attachment you can find a file may help you to write a UMAT and also to define the stiffness matrix in ABAQUS.

Farajollah Zare Jouneghani

Dear Majid

Attached you can find a video file related to how you write UMAT.

https://www.youtube.com/watch?v=5br5fjqK0uM

I am sorry for the late response, please find attached Ansys user material subroutine for different plasticity models.

Also you can get the following book, it includes explainations for plasticity implementation and the examples are showed by Abaqus subroutines. All the files are found in the book CD.

https://www.amazon.com/Introduction-Computational-Plasticity-Fionn-Dunne/dp/0198568266

Hi Gentlemen,

Many thanks for your responses.