In general for incremental plasticity problems it is well known that one has to use an iteration scheme (Newton-Raphson, modified Newton-Raphson or Quassi Newton etc.) in order to achieve a converged solution for finite element equations. Is it also neccessary to have an iteration scheme for an incremental viscoplastic problems ? I am also attaching a paper where the authors have implemented an equilibrium correction scheme in the principle of virtual work, which is supposed to ensure convergence. I am not able to comprehend how it takes care of the convergence without any iterations. Any help would be highly appreciated.

Thanks

Suman

Hi,

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. 

Thanks,

Luv Sharma

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.

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.

Thanks
Shabeer Khan
MSc Computational Mechanics

This is a review on ductile fracture committed to the Advances in Applied Mechanics (Vol 44). Part of the review has an educational purpose and, as such, is intended for advanced undergraduates and starting graduate students. The other part is an account of recent research conducted in the field.

Though quite long, the review is by no means exhaustive. As noted in the discussion, many valuable contributions to this field have been left out. The focus was laid on micromechanics-based approaches to connect to microstructural aspects in engineering materials.

 I will try to post the electronic PDF once I get permission from Elsevier. 

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.

The solution for plastic strain rate increments starts to blow up after few steps of entering the plastic regime. I've tried several things:

i) running the problem, reducing the time steps.

ii) refining the mesh.

But the problem persists. 

 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 

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.

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.

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 

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

maxianfeng@gmail.com

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.

Thanks,
Dhruv

PS: This is a wonderful website!!!