Hi,
I'm presently working on implementing anisotropic yield criteria in LSDYNA as UMAT.
I understand from the LSDYNA documents that effective plastic strain is a default history variable. So when we code, can we omit the update of effective plastic strain as a history variable? If so, where is it stored and how is it retrieved during post-processing ?
Hi all,
In Abaqus Theory Manual 4.6.1, there is a concept called "effective deviatoric elasticity". I think that term is actually DDSDDE, i.e. the consistent linearized tangent moduli.
But why is it called "effective DEVIATORIC elasticity"? It sounds like we missed the volumetric part (but only considering the isochoric part).
I would really appreciate it if someone could help me with this. Thanks!
-Shawn
Hi all,
I have been writing a UMAT function with modified hyper-visco-elastic model. My question is: after I got the Cauchy stress at the end of step, how do I get the SSE （elastic strain energy density)?
If it is only hyper-elastic I would have known (since the strain energy function itself is given). However, if it is viscoelastic, how should I calculate?
PS: I would also appreciate it if anyone could shed some light in getting SPD, SCD as well. Thanks a lot!
-Shawn
Hello everyone,
I'm currently doing an analysis on the convergence rate of an incremental model that I have implemented in ABAQUS using a UMAT. Here's the BIG lines of the problem:
1) In UMAT : Solution of a differential equation using explicit Runge-Kutta 4 (RK4), which has a 4th order convergence rate, yields the stress state "S". (In my problem, stresses are applied)
Hello everyone,
I am running a UMAT on ABAQUS. However, I need to call another subroutine : URDFIL. I have included the URDFIL subroutine in the same file as the UMAT subroutine.
The problem is that when I run the program, ONLY the UMAT subroutine runs. It looks as if ABAQUS ignores completely the URDFIL subroutine (It doesn't run it at all). Do we have to include anything
specific in the INPUT file in order for ABAQUS to take the URDFIL into account?
Thanks for the help!
- Jack
Hello everyone,
I am currently writing a UMAT for non-linear viscoelastic materials. In order to do some verifications,
I need to be able to customize the time incrementation scheme. For example, the first increment would
have a time step of 1E-5s while the other increments would have constant time step of 1E-2s. I know this is not a
very straightforward problem, but I really need to be able to do that. I am currently trying to combine my UMAT with other subroutines
Hello All,
Does anyone have any idea how to automate meshing using USER DEFINED ELEMENTS (for Example UEL) in Abaqus using python. Actually I need to mesh an arbitrary shaped structure with 9-Node Quadrilateral Element. Abaqus doesn't support meshing of 9 Node Quad Element (S9R) either.
Hello everyone,
I'm last year PhD student. I would appreciate if someone could advice me about active research groups in Computational Plasticity (material models, hardening models, yield criteria, UMAT) in California or Australia.
I'm looking for an interesting research group to find a post-doc but I don't know from where start.
Thansks to everyone!!
Hello everyone,
I'm last year PhD student. I would appreciate if someone could advice me about active research groups in Computational Plasticity (material models, hardening models, yield criteria, UMAT) in California or Australia.
I'm looking for an interesting research group to find a post-doc but I don't know from where start.
Thansks to everyone!!
Greeting to all iMechanicians,
