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.
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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
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.
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
https://depositonce.tu-berlin.de/handle/11303/1574
http://dx.doi.org/10.14279/depositonce-1277
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
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
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:
