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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.

Zheng Jia's picture

Rate-dependent stress evolution in nanostructured Si anodes upon lithiation

Zheng Jia, Wing Kam Liu, Rate-dependent stress evolution in nanostructured Si anodes upon lithiation, Applied Physics Letters, 109, 163903 (2016) (DOI:

Shailendra's picture

Post-doctoral positions at National University of Singapore (NUS) and Singapore University of Technology and Design (SUTD)

Starting April 2016, we will have openings for two post-doctoral fellow positions in experimental and computational mechanics of advanced polymers. These positions will support a new research program between Singapore University of Technology and Design (SUTD) and National University of Singapore (NUS) funded by Agency for Science, Technology and Research (A*STAR). The project focuses on synthesizing, characterizing, modeling, and simulating the thermo-mechanical behavior of polymers with covalent adaptable networks (CANs), e.g. vitrimers.

Open Ph. D. Position in Dept. of Mechanical Engg. in NC A & T State University

Multiple Phd. positions are available in the area of computational solid mechanics with an emphasis on multiscale modeling of polymer nanocomposites, high strain rate characterization of novel nanocomposite materials,  in Mechanical Engg. Dept. in North Carolina A & T State University. Interested candidates are encouraged to communicate via email to and/or

 There are several graduate positions available in thermal fluid and control area also.


luvsharma11's picture

Viscoplasticity (Anand's Model in ABAQUS CAE 6.8)


I am trying to model a double lap shear in ABAQUS. In Abaqus version
6.7 and above, Anand's model can be invoked by editing keywords and
adding necessary data lines  in keyword editor. I am facing some
prblems in running the job analysis and since I am new to working with
ABAQUS, I am not able to solve the problem. The problem is, when I
submit the job the status keeps on showing "Running" without showing
any error or warnings. I have tried all both coarse and finner meshes
so i think there is no problem with convergence. 

DEM modelling of granular flow

Hi iMechanica,

I want to start a discussion on the current status of DEM modelling of granular media. I know that Luding has published many papers in this area. Please add to the current research on granular flow modelling like viscoplasticity, hypoplasticity etc and the  numerical DEM methods.

Shabeer Khan's picture

Plastic strain data

Dear All

I am working on Abaqus simulation for thermo-visco-plasticity, especially on necking problem in circular bar.
I need the plastic strain data to add in the material properties table of Abaqus.
And, any help in this regard would be appreciated.

Shabeer Khan
MSc Computational Mechanics

Problem solving Strain Gradient Viscoplasticity based on the framework of Fleck and Hutchinson

I am tyring to solve simple shear problem using a large deformation FE code based on the framework developed by Fleck and Hutchinson for gradient plasticity/viscoplasticity problem (see the attached paper). As the per the formulation, the independent variables are the displacement increments and eqv. plastic strain rate increments. Two sets of equations are solved, one for displacements and the other for plastic strain rates at nodes, following the the above formulation.

regarding Abaqus

 hi guys

am Mr.sam doning phd in mechanical engineering, i am a new user in Abaqus i getting well with it, but i always got axcessive distortion whenever i rty to run for high strain rate probelm. if some of you kindly can give me some hinte it will be great.

 thanks in advance 

Problem with fortran code for solving large strain 2D elastic problem by FEM using Updated Lagrangian Framework

I am using my own fortran code to solve a large strain 2D elastic problem using FEM in Updated Lagrangian framework and I am using incremental formulation. It works well for 2D pull of a square block with 2 elements and I've compared the results with a commercial FEA package. But while solving bending of a cantilever beam the results starts to blow up and the elements distort abruptly after certain time step. This happens only when the load or the displacement given at the free end of the beam is large otherwise it works fine.

Chaboche elasto-viscoplastic model with plastic strain memorization and time-recovery in ANSYS

Hi, I am a reserach fellow of mechanical engineering in Italy. I need to implement the elasto-viscoplastic model of Chaboche in a user subroutine in ANSYS accounting also for the plastic strain memorization and for the static and dynamic recovery. In a next step I sould also need to incorporate the damage variable of this model.

Justin C. Mach's picture

Continuity in the Plastic Strain Rate and its Influence on Texture Evolution

Classical plasticity models evolve state variables in a spatially independent manner through (local) ordinary differen- 

tial equations, such as in the update of the rotation field in crystal plasticity. A continuity condition is derived for the 

lattice rotation field from a conservation law for Burgers vector content—a consequence of an averaged field theory 

of dislocation mechanics. This results in a nonlocal evolution equation for the lattice rotation field. The continuity 

Extended Chaboche viscoplastic model for cyclic loading

Choose a channel featured in the header of iMechanica: 

These days I've been applying oneself to implement the Chaboche viscoplastic model in ABAQUS user-subroutine for simulating the cyclic loading in single crystals.
The procedure can easily get out. I'm not sure about the problem, the deduction of Jacobian, the convergence? 
Btw, I know there is free subroutine for crystal plasticity by Huang YG. I wonder if the UMAT routine for chaboche model is available, then I can generalize it to fit for my case.
If pity there isn't, guide or example for viscoplastic model can be of great help also.
Thanks a lot

yoursdhruly's picture

Review of a few "Unified" Viscoplasticity Models (Motivated by solder deformation)

I had prepared this document for a class project, the level is introductory and the selection of models is motivated by solder deformation, but I hope it is of some help. I have examined four models, proposed by Hart, Anand, Krempl and Busso. The document has 16 pages.


PS: This is a wonderful website!!! 

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