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Jinxiong Zhou's picture

Implementation of ABAQUS User Subroutines for Viscoplasticity of 316 Stainless Steel and Zircaloy-4

This paper describes the formulations for the viscoplasticity of metals based on the Chaboche and Delobelle model. The implementations of the viscoplastic models were detailed herein and then implemented via user subroutines for material models (UMAT) in ABAQUS. Two typical metals, i.e., 316 Stainless Steel and Zircaloy-4, were chosen as examples and their viscoplastic behaviors were captured. Numerical simulations are compared to reported experiments in order to validate the models and the UMAT codes.


All qualified candidates are encouraged to apply; however, Canadians and permanent residents will be given priority.

Institution: University of Windsor, Canada ( )


Salary: will be commensurate with the successful applicant’s qualifications and experience, and will be determined at the time of hiring.

Start date: immediately


Dear All, 

We are working on Equal Channel Angular Pressing (ECAP) project and we are trying to implement CPFEM with Abaqus UMAT, there are few examples online but we could not able to run them on abaqus 6.13 with any subroutine. Does anyone have any working subroutines on related subject?

Kind Regards


Yunus Emre Kulhan

ABAQUS: Access stress of integration point of elements during calculation

Hi all,

I'm using ABAQUS and UMAT for structural simulation. I used quadratic element (CPS4) with 4 integration points (IP).

During the calculation (which calling my UMAT), at each time step, for each element, I need to calculate the average stress of these IPs and produce a state variable for these IPs from this average stress. Then, I would need to update this state variable back to these IPs in that element. But as far as I know, the ABAQUS call UMAT for every IP and calculate everything within this current IP.

UMAT for MAZAR's Concrete Damage Model

Hello All,

I am working on stochastic upscalling of damage in concrete microstructure. Can someone provide a UMAT for Mazar's damage model or any resource to help me create UMAT on my own.

Thank you.


Vasav Dubey

Texas A&M University

Texas, USA


Frank Richter's picture

UMAT for Zener model and Kelvin-Voigt model

Dear iMechanica community,

you can find the UMAT-implementation of a Zener model, i.e. a Maxwell model parallel to a spring, in my PhD thesis:

“Upsetting and Viscoelasticity of Vitreous SiO2: Experiments, Interpretation and Simulation“
Technische Universitaet Berlin, Germany, 2006

shreeram111's picture

UMAT Non linear Viscoelasticity - Algorithm verification?

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Hello everybody,

           My task is to write a UMAT for Non-linear Viscoelasicity based on Schapery's model in ABAQUS. I have coded the routine, but I am still not able to predict correct response. I tried to debug it as much as I can. I understand that it would be difficult for anybody to understand my code. So, I have attached a flowchart (pdf) of the whole algorithm that I follow. It would be nice if you could check that and correct me if I am wrong.

Thanks in advance for your time and consideration



Modelling cyclic behaviour of soil using UMAT

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I have been trying to model the cyclic behaviour of soil. I got a UMAT. But when I'm using UMAT, it is creating lot many errors (like numerical singularity and excessive distortion). I have constrained it properly. I tried running my model with an inbuilt material (clay plasticity) and I'm getting results. Here I'm not even able to move from the initial geostatic step. Can anyone please help

New publication for UMAT and VUMAT in ABAQUS

We performed a comprehensive study of a large class of Implicit and Explicit integration algorithms for Elastic-Plastic behaviors in Finite Element Analysis (FEA) developed in UMAT and VUMAT for ABAQUS and presented various unique results. We also showed detailed integration algorithms for both Associated and Non-Associated Flow Rules with mixed isotropic and kimenatic hardening with expandable number of internal variables (damage and etc).

Full bibliographic details:

bitamendi's picture

Looking for a VUMAT programmer to share publication with

Dear researchers,


I’m Joseba Mendiguren, researcher at the Advanced Manufacturing Group of Mondragon Unibertsitatea. I’m currently working on advanced yielding/hardening models for metals.
I’m in the middle of a paper writing work but I cannot find time to sit down and program the VMAT that I need to run some simulations for the paper. I’m looking for a VUMAT programmer researcher willing to work on the topic and share the publication authorship on return.

Bone Remodeling Subroutine

Dear all,

changing density for FGM in umat

Free Tags: 

Hello friends,
Here is the Abaqus user subroutine for Functionally Graded Material with direct integration method. This Umat is based on S.H.Song's Umat. Obviously the coefficient AAA in calculating E is the ratio of young moduli of  two sides of the plate. With this method, one can change young modulus through the thickness.

But I have problem with changing density through the thickness, meaning from density of ceramic to density of metal.
I would be grateful if anyone can help me. Any help would be appreciated.

DSTRAN in UMAT with nonlinear geometry

Dear Colleagues,

I have done some analysis with nonlinear geometry. I use quadratic 3D solid elements. I have learned the way to calculating DSTRAN and DROT from ABAQUS documentation as follows:

Rashid K. Abu Al-Rub's picture

Postdoctoral Position in Computational Damage Mechanics Available at Masdar Institute in Abu Dhabi

A Postdoctoral Research Fellow position in computational damage mechanics is
available immediately at Masdar Institute of Science and Technology in Abu
Dhabi in United Arab Emirates. Masdar Institute is established in collaboration
with Massachusetts Institute of Technology. The research project focuses on
using advanced computational fracture and damage mechanics for simulating the
behavior of advanced materials under different loading and environmental
conditions. The candidate is expected to have a PhD in the field of Mechanical,
Civil, or Aerospace Engineering with solid knowledge of theoretical/computational
solid mechanics; continuum damage mechanics, fracture mechanics,

UMAT and UEXPAN subroutines

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I am having problems in writing the umat and uexpan subroutines applicable to the creep model defined in


Has anybody written the algorithm? 

Postdoctoral position in computational solid mechanics

Job Summary:
The postdoctoral research associate is expected to
provide research support within the frame of a multi-year engineering
research project undertaken by faculty from the departments of
Mechanical Engineering and Applied Math and Sciences at Khalifa
University. Limited teaching or other academic duties may be assigned to
the successful candidate under the supervision of the Advisor as
required by the University.
The successful candidate will be

Adding static/dynamic library to an Abaqus user subroutine

I want to use an external subroutine in my umat but I have not been able to do that so far. Having created a dynamic library project in Visual Studio 2008, I have created a .dll and .lib files and copied the .lib file into the working directory of my abaqus job and the .dll file to exec folder. I have also added the directory of the .lib file in the LIB environmental variable. But I get these errors from ABAQUS: 

Sample code for Abaqus subroutines

Here you can find a sample codes along with documentation:

 At the end of the page there is the link. 

Parallel Multiscale modeling in ABAQUS using UMAT

Hello everyone,

I am currently in the process of implementing a multiscale modeling approach in ABAQUS/Standard.

Here is what I am doing.

Macroscale ABAQUS model <--> UMAT <--> Python script <--> Microscale ABAQUS model

So basically the microscale model is being called at every macroscale integration point. The UMAT passes the required data to python as command line arguments and the python script returns the stress and tangent modulus in a text file.

ABAQUS model of polycrystal plasticity

Hi everyone 

I am learning the polycrystalline crystal plasticity and testing material in ABAQUS and UMAT. Now I am trying to build a RVE by using the truncated octahedrons as the grain shape or Voronoi tessellations.

For truncated octahedrons, I built a truncated octahedrons and assembled them into the grain aggregate in the .inp file, and assign orientations in the UMAT based on the part's name. However, I found it hard to define their interaction between grains. What is their interaction properties and how to define the contact pair in an automatic way?

UMAT Multi-element Error

Hello All:


I have written a UMAT code to predict the viscoelastic behaviour within a
shape adaptive structure. I have followed similar steps used in Abaqus
subroutine manual, I have applied this UMAT to a single quad element and
it works as predicted. But when I apply it multiple elements model it
breaks down. 

Is there any special command i need to put in UMAT subroutine to account
multi element analysis? I will appreciate all related comments, 


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