Dear Wolfgang,
It is as you mentioned, the STRAIN is provided as an input to the UMAT.
UMAT then updates the STRESS and returns it as an output.
I have attached an image of the UMAT subroutine for your reference. This is
a very general outline. Please don't worry about all the parameters which
are present in the subroutine definition.
The most important parameters are:
integer ndi !number of stress components
integer nshr !number of engineering shear stress components
integer ntens !size of the stress array (ndi + nshr)
integer nstatv !number state variables
integer nprops !number of material constants
integer layer !layer number
integer kspt !section point number within the current layer
integer kstep !step number
integer noel !element number
integer npt !integration point number
integer kinc !increment number
c---------------------------------------------------------------------------
real(8) drpldt !jacobian drpl_dt
real(8) dtime !time increment dt
real(8) temp !temperature at t0
real(8) dtemp !increment of temperature.
real(8) celent !characteristic element length
real(8) sse !specific elastic strain energy
real(8) spd !specific plastic dissipation
real(8) scd !specific creep dissipation
real(8) rpl !volumetric heat generation per unit time
real(8) pnewdt !dt_next/dt_now
c---------------------------------------------------------------------------
real(8) ddsdde(ntens,ntens) !jacobian ds_de
real(8) statev(nstatv) !state variables
real(8) props (nprops) !material constants
real(8) ddsddt(ntens) !jacobian ds_dt
real(8) drplde(ntens) !jacobian drpl_de
real(8) stress(ntens) !stress tensor
real(8) stran (ntens) !strains at t0
real(8) dstran(ntens) !strain increments
real(8) dfgrd0(3,3) !deformation gradient at t0
real(8) dfgrd1(3,3) !deformation gradient at t0+dt
real(8) drot (3,3) !rotation increment matrix
real(8) coords(3) !coordinates of this point
real(8) time (2) !1:step time; 2:total time, At t0
real(8) predef(1) !predefined field variables at t0
real(8) dpred (1) !incr of predefined field vrbs
On Wednesday, August 8, 2018 at 6:52:56 AM UTC+2, Wolfgang Bangerth wrote:
>
> On 08/07/2018 03:31 AM, Mahesh Prasad wrote:
> >
> > Thank you for the suggestions. I have already looked through the
> > "Applications" and found that "PRISMS-Plasticity" is working on similar
> lines
> > (Crystal Plasticity FEM).
> > The nature of the problem is : Multi-scale simulations using Crystal
> > Plasticity FEM.
> >
> > Over the years we have developed the UMAT subroutine that describes our
> > material models. So, instead of implementing them from scratch in dealii
> we
> > would like to have an interface that communicates between the UMAT and
> > dealii. So, my question is: Has anyone tried to link the UMAT
> subroutines
> > with dealii ? i.e., The UMAT (fortran 90) has to be called at each
> integration
> > point. If not, How do I go about linking the fortran code with dealii ?
>
> Mahesh,
> since few of us will be familiar with how exactly ABAQUS interfaces with
> externally written routines, can you explain what these UMAT functions
> take as
> input, and which information they return?
>
> I suspect that they probably receive the strain as input and return the
> stress
> as output, but it would be good to know for sure. It may also be that it's
> the
> derivative tensor, of course, which may actually be more useful in
> practice.
>
> Best
> WB
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: [email protected]
> <javascript:>
> www: http://www.math.colostate.edu/~bangerth/
>
>
--
The deal.II project is located at http://www.dealii.org/
For mailing list/forum options, see
https://groups.google.com/d/forum/dealii?hl=en
---
You received this message because you are subscribed to the Google Groups
"deal.II User Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/d/optout.
